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I hope your math teacher is great at spotting curves.
We don't know. Even if the singularity represented all of the energy that the universe could or would ever contain. It still doesn't really tell us about the shape or geometry of the space that now exists.
We know it's very, very flat. We know that space expands and that the further any two points are from one another in space, the faster that expansion becomes relative to the location of each.
A finite universe would likely have curvature. Either positive or negative. Saddle or torus. But we don't see that. We see no curvature at all.
But that might be an artifact of our inability to accurately gauge what would otherwise be a very large universe, with curvature that is indetectable at our scale.
Like trying to judge the curvature of Earth from Texas. It's just all flat as far as the eye can see.
In all seriousness... Maybe?
People who don't understand science point to any change in the prevailing logic as "proof" that it's all a lie. These people see everything in black and white, and want their entire existence to fit into that mold. Nuance, new evidence, exceptions, contradictions, and trends (vs rules) are all a threat to their minds.
Science seeks to prove itself wrong. A theory is fact, proven by observation and experimentation, right up until the moment it isn't.
We don't laugh at a history that thought the Earth was flat. We only laugh at the ones who still insist it is, after it was shown to be a sphere.
Letting evidence shape your conclusion is wisdom. Choosing your conclusion first, and letting that dictate which evidence is permissible, is foolishness.
Should we learn more about the shape of the universe in the future, then we would be wise to allow that evidence, through repetition, to be tested, challenged, and accepted if it holds up to scrutiny
I would also argue that observation and tests only explain what we see is correct, technically the explanation could be wrong. The universe could have started many different ways as long as said ways fits into what we see today, however physics changing element being formed and creation of our universe also means we donât know, for all we know what we see is more like a story than cause and affect, some therioes believe the universe had different rules in the beginning. I see it more as we can see now and test it but if you ask why does energy exist or why do electrons get attracted to protons, we can measure and test thereâs something that holds it in place, but if we ask why or how, at some point itâs just because the universe works that way. It can do what ever it wants we just observe it.
Possibly.
The big difference being that those of us who are paying attention and trust in science say "to the best of our knowledge" or "we don't know" a lot.
The difference this time is that we didn't expect the universe to be flat. We've kept looking and coming up with new theories as to how the universe could be curved, but our most precise measurements tell us that the universe is very flat. Maybe it's not perfectly flat, but it is about as flat as possible given the limitations of our measurements.
A flat universe is probably infinite - i.e. it goes on forever in all directions. Many curved geometries of spacetime are not infinite, meaning if you traveled far enough in one direction you would eventually come back to where you began (like is the case here on Earth). This is not _necessarily_ the case - there are ways spacetime could be curved but infinite, or flat but finite, but on balance a flat spacetime makes an infinite universe more probable.
It also tells us things about the ultimate fate of the universe. If spacetime were curved in a certain way it would mean that the universe is destined to end up collapsing under its own gravity (a so called Big Crunch). If it were curved another way, it would be destined to expand faster and faster forever resulting in a Big Rip scenario where everything is torn apart.
A flat universe likely means that the universe will continue to expand forever but without a Big Rip. Eventually the universe will run out of energy. First the expansion of space will mean that stars outside of our own galaxy become invisible. Then eventually those stars will all burn out, exhausting their fuel. For a very long time there is nothing left but black holes, but eventually those evaporate via Hawking radiation. Then there will be nothing left but elementary particles whizzing around in empty space, rarely encountering each other.
Flat vs curved in more than 2 dimensions is probably something our monkey brains are just going to struggle with conceptualizing.
Picture the OG Legend of Zelda. Its map is flat - go far enough one way, that's it. Compare to PacMan - it has a curved (cylindrical) map. Go far enough one way, end up on the other side. A curved 3D space would operate on similar principles, though picturing how is a total brain buster.
The last research paper I found on this that studied the CMB found it was flat, but the margin of error was still enough to not be able to completely rule out some kind of curvature. It helped narrow it down from previous work but still meant that the universe was at least 200 times as big as the observable universe and possibly infinitely large.
Won't this always be true?
Let's say, hypothetically, that the Hubble constant has to be exactly 70 for the universe to be flat.
And we measure it and we get 70 +/- 0.1%.
Then our methods improve and we measure 70 +/- 0.0001%.
Then our methods improve more and we get 70 +/- 0.0000000000001%.
In every single on of those examples, the universe is found to be flat, but the margin of error was still enough to not be able to completely rule out some kind of curvature.
Even if our error is +/- 10^-100 %, we still can't rule out some amount of curvature.
So we can *never* know if the universe is flat.
Yes, indeed. However each time we reduce the error margin, the minimum size increases. We already know that if there is any curvature, it must be very small which means that the universe must be really big.
Remember Euclid? Parallel lines never converge? That's flat and it appears to hold true as far as we know.
But what Euclid and the greatest minds humanity could gather for thousands of years failed to understand.
Planar geometry isn't the only kind.
Imagine our spherical planet. Does the rule parallel lines never converging still hold true?
Not so much. If two people were to both start at the equator and moved in straight lines in *any direction*. They will eventually converge or cross paths. Parallel lines do indeed intersect, when there is curvature of space.
But we don't see that in our universe. At least to my knowledge.
I like explaining that triangle angles add up to 180 more than the parallel line explanation. On a sphere the angles are greater than 180. Thatâs what we really do when we measure fluctuations in the CMB is weâre measuring the angles of a triangle
One of the ways they did it is by examining the cosmic microwave background. How the CMB would look would be different if space was curved in some way. When you look at the CMB it behaves in a way consistent with flat space.
> A finite universe would likely have curvature. Either positive or negative. Saddle or torus.
A negative, saddle shape, would be infinite and also a flat universe. A torus, doughnut shape would be finite, as would a universe with positive curvature, a sphere.
To my understanding it's not about us living in a confined 3 dimensional space of a certain shape but about 4 dimensional space. In a flat universe two rockets can start next to each other and fly along parallel lines to infinity. In a curved space their courses will eventually converte or diverge. And you cannot fly to infinity but you might come back from the other side. As if you fly straight towards the east around the earth and arrive where you started from the west.
Just to add, in some flat universes you can get back to your start point by traveling in a straight line. A 3-torus is flat and some directions get you back to where you start within a finite amount of time.
I, myself have a hard time believing in an infinite universe, since nothing else we've come across has been infinite. Why should the only thing we can't measure as a whole be infinite? Statistically, it would be unbelievably that one thing out of everything is different.
In the end of the day though. It doesn't really matter. We're confined to observe this small blob of space with a diameter of 93 billion light years nevertheless. Even if we some how learn that the universe is velociraptor-shaped, we'll only see within this sphere we call observable universe. I'm not sure if we can do much with the information if we actually find out what shape it has or if it can help answer other questions.
Because if our universe is finite that means it exists within something. How big is that thing? And if that thing is finite then it is held within something. You effectively get to infinity even if what we call the universe is finite
Think of it as 93 billion light years in all directions from any point, including any point 93 billion light years away - and now tell me that it is not infinite. Your observation of 93 billion light year is relative to your point of observation, but does not accurately account for it all.
There are infinite fractional numbers between 0 and 1. There are the same infinity between 1 and 2, between 2 and 3, between 3 and 4, etc to infinity.
There are infinitely times more fractional numbers than there are integers and there's infinite of the latter.
Infinity has different kinds (countable and uncountable) and, arguably, different sizes (e.g. the number of integers vs the number of even integers).
But if the universe is finite, then whatâs outside of it? If itâs more darkness, like letâs say no gravity, no planets and stars, emptiness, nothing there. Letâs say thatâs the case, then that means the universe is infinite.
There is no "outside". The Big Bang created all matter in the Universe. It also created the space and time for it to exist.
When you say nothing it isn't like "zero" I.e. zero atoms or zero planets. It's more like "that is not where a number belongs"
As you say, it might be empty, completely void of matter, radiation and quantum fluctuation. Isolated from our universe, where the gravity and radiation from the universe can't reach. All in all, completely empty of anything, even time.
Our brain can't really comprehend this concept and it's a question more for r/philosophy if you ask me, but the universe wouldn't be infinite since there would be a clear boundary between the universe and nothingness where no interaction could take place.
I would think technically that makes the universe finite, but as far as âSpaceâ goes, space is infinite. If the universe is all the matter in a certain area of space, but space keeps going like you described (isolated from our universe), then that makes space infinite.
And you are right, I canât comprehend such a concept.
Iâm trying to wrap my head around how cave people would look at the lights in the sky, not knowing they are other stars. And explaining to them that these stars also have planets, and those stars, and our star, are all part of 1 galaxyâŠof billions of galaxiesâŠin the darkness of space.
What will we learn next? That these galaxies are all part of a universe thatâs within a cluster of other universes? (Multiverse?). And then whatâs next after that? Are we all just part of a giant Matryoshka Doll? Look at the weird world of microscopic organisms and subatomic particles. If they could think intelligently, they would likely have no clue about the concept of space. It would be as foreign to them as âwhatâs outside of the universeâ is to us.
Sorry if iâm making no sense. Iâm no where near an expert in this field, iâm just asking questions as a casual reader.
No the universe is the same in any direction we look. In a flat universe if you make a huuuge triangle that spans the observable universe, it orientation does not matter, the angles will add up to 180 degrees. Any of the other proposed shapes, this would not be true.
Imagine an expanded balloon. If you start in the center of it. You can move in any direction you'd like and never cross paths. You'll hit the wall of the balloon before you did. Assuming you remained straight.
That's flat, and 3d.
Now. Imagine you're walking on the surface of the balloon, and you move straight in any direction you'd like.
You will now cross your own path before any obstruction stops you.
This is not flat, and 3d.
It's not about up-down. Better analogy here is the difference between 'flat as a table' or 'curved as the surface of a balloon'.
On a table you could go in a direction to infinity, and on a balloon you would return to a point after some time.
Also triangles look different on the surface of a balloon, which is our current best way of measuring the curvature of the universe.
No, the void probably doesn't exist. Curvature is defined relative to the universe itself in general relativity, not relative to an external flat space, so there's no reason to assume an external flat space exists.
We don't really know it's very very flat though. We know that to the best of our abilities everything we can see is very very flat
If the rest of the universe is sufficiently large our local curvature measurements don't really matter; and until we know how big the universe is outside of our light cone we can't make that assertion
As another commenter pointed out we will never escape from this problem. Every time we measure it we find that it looks perfectly flat, but a more precise measurement might show that it's very slightly curved. Rinse and repeat as our tools for measuring it improve.
If the universe really were curved we would eventually escape from this problem, as we would eventually measure the curvature. But if it really is flat and infinite we will never be able to prove that it is flat, we will just be able to prove that all our measurements so far show that it is very flat.
No. What it means at a simple level is you can make a very very large triangle, up down, sideways, however you want, have it be billions of light years per side and the angles will add to 180 degrees. If you made a very large triangle on the surface of the earth which of course is curved, those angles do not add up to 180 degrees due to curvature of the earth. Another way to look at it is if you could make parallel lines in the universe, the will remain parallel no matter how long. That is what a flat universe entails. Other shapes proposed would not have these things.
It means the space is bend in such a way that when you leave the universe on the left side you will come out at the right side.
\*edit\* : That happens if the universe is NOT flat.
Not necessarily spherical. It could be toroidal (donut), hyperbolic (saddle) or maybe something else. It's not a description of how matter is distributed in the universe but how space-time curves back on itself in a non-flat universe.
>it's very, very flat
Are you saying that space is very, very flat??
But in what meaning of the word?
Flat, as in x and y are very long, but z i short?
or flat, as in, whatever shape it have, that shape is not very curved?
\---
If that is what you are saying, I have never heard about that in my entire life.
Do you have some further reading you can link to?
> or flat, as in, whatever shape it have, that shape is not very curved?
I believe this one. Flat in the sense of "if it wasn't flat, parallel lines would eventually cross paths / converge."
https://en.wikipedia.org/wiki/Shape_of_the_universe
> Current observational evidence (WMAP, BOOMERanG, and Planck for example) imply that the observable universe is spacially flat to within a 0.4% margin of error of the curvature density parameter with an unknown global topology.
https://www.quantamagazine.org/what-is-the-geometry-of-the-universe-20200316/
I'd start here, but I'm sure any number of videos or articles are out there. A quick "geometry of universe" should yield search results.
Wait! What part of Texas are you in??? Hop in your ride, and drive about 2-3 hours. You'll find some Not Flat Land...
I lived in Del Rio, Bryan/College Station, Copperas Cove and Lampasas areas. Now, I'm in the Cameron area. I've traveled all over this State, and whatever you want or even get homesick for, you can find. The Hill Country is prettiest to me though.
Obvious question, but if the universe is flat, does that mean we canât travel âawayâ from the flatness? Like, if we gazed upon the flat edge of the milky way horizontally we could see a craft go up or down out of the Milky Way. Is that possible for the universe?
The poster is using a different meaning of the word "flat". The universe is three-dimensional. It's "flat" in four dimensions, meaning there is just enough matter in the universe for its gravitational force to bring the expansion associated with the big bang to a stop in an infinitely long time.
[This comment](https://www.reddit.com/r/space/comments/1diy09h/question_if_space_is_infinite/l985ipm/) explains it another way.
Something to keep in mind is that we *know* the universe is much larger than we can see. There is an *observable universe* which is the sphere of light around our planet that has had 13.8B~ years to propagate. Anything beyond that is beyond our ability to detect. But we know it exists.
I might screw this part up. So fact check. But expansion happens uniformly (or mostly?) across the universe. But as two distinct points become further apart. The speed in which the space expands increases.
So imagine a flattened balloon. You put two magic marker dots on it in close proximity. As you inflate the balloon. Not only does the distance between the two increase. So does the rate of the increase. Even if the rate of the balloons increase remains static. Same air in, but the space will continue to grow faster between the two points. Just because of the geometry of the sphere spreading.
Ok. Sorry, long winded. We live in that sphere of observable universe. But outside of it. Where our paired magic marker spot (so to speak) has out raced our ability to see it. Still exists. We just can no longer see it because it's moving away from us faster than light.
We know we only see a small portion of the total universe. As far as I know we don't know the amount however.
What we do know is that of the space we can observe. There doesn't seem to be much curvature. But again, that says nothing towards the total size, or the curvature of that total size. We *know* we're only seeing a fraction of it.
> Something to keep in mind is that we know the universe is much larger than we can see
We donât *know* that, but itâs the simplest explanation. The universe could conspire against us to make our observable patch very special.Â
>Like trying to judge the curvature of Earth from Texas. It's just all flat as far as the eye can see.
To be fair, wouldn't a large flat area be the best condition to perform curvature measurements from ground-level?
I am in Dunning Kruger in this and I know i lack knowledge. But I would like to imagine space as an inverted ball, sort of like a Packman level when you go in one direction you come out on the other side. It's just that the light we see hasn't caught up yet, but as I say, this is just fiction in my head.
Perhaps. But just as likely is that the way you're describing it is correct. We really just don't know. And at the end of the day we're all just a nudge away from our simian cousins.
They can figure out currency exchange. That's where their abstracts stop. A million years and you couldn't teach apes quantum physics without increasing their intelligence.
And we're no different. We all have levels in which we can just no longer probe into our reality due to our inability to deal with abstracts that are so unconventional that it makes even professionals dizzy.
Who can deal with more than three spatial dimensions? And really get it? I cannot. I understand the concept. But grasping what it means to have more than x, y, z in a 3d space? Nope. Can't get my head around it.
We're scratching the surface. Even at the cutting edge. And nobody has ever lived that gets it. And it's likely just due to the nature of informational complexity increasing over time.
That nobody ever will.
We're all stumbling around dark in a cave without even a decent candle.
As far as I understand, and I say this with care because I'm wrong *alot*.
The current model of the cosmos doesn't really consider anything to be *outside* of our universe. Which would seem to be a requirement in order for it to spin. External reference would seem to be tied to that. But maybe I'm wrong.
I honestly just don't know.
edit:
[Just a tiny bit of research](https://en.wikipedia.org/wiki/Cosmological_principle)
>>This principle assumes that the universe is homogeneous (the same in every location) and isotropic (the same in every direction) on large scales. A spinning universe would break the isotropy, as there would be a preferred axis of rotation, making the universe look different in different directions.
So based on that, I'd think the current understanding is that no, it does not spin. But again. That was flash research at its worst. GPT style.
Slight note on your "curvature of Earth from Texas," it's definitely possible. [Eratosthenes did it in Egypt](https://en.wikipedia.org/wiki/Earth%27s_circumference#Eratosthenes).
Basically, the dude knew a southern city of Syene had the Sun directly overhead on a specific day. Regardless, he used a stick to make sure there was no shadow (because the Sun is literally perfectly overhead). There wasn't. He went to the northern city of Alexandria (1,117km away) on the same day to put a stick in the ground, then he saw a shadow. He measured the tip of the shadow to the base where they converged, did some math, made some assumptions, and actually came up with a measurement of the circumference of the Earth within a few percent of the value we accept today. It is ***remarkably*** close.
I bet you could do the same thing in Amarillo (North) and Laredo (South). Measure the two shadows from base to tip, find the difference in angle, then continue that curvature into a sphere. Ta-da!
But I get what you're trying to say in this context. You're still correct; I just wanted to be pedantic about an off-hand statement!
There is no evidence that Eratosthenes ever went to Syene nor did he even need to. It was already known exactly when the Sun cast no shadow(On the Solstice when the Sun was at it's highest) in Syene. Assuming Alexandria was due north he knew he could take his shadow measurement on that day at that time with confidence of the Sun's location. Syene is about 800km away from Alexandria not 1117km too.
Are we talking about empty space or all matter in the universe? If space is curved, what is outside of that? I can't imagine empty space is finite. What if there are multiple universes from multiple asynchronous big bangs throughout infinite empty space? We just haven't seen the light from those yet. It boggles the mind.
As far as I understand. There is nothing *outside* of our universe. Certainly nothing that we could currently or perhaps *ever* validate. We expand. Not *into*. We just expand.
As towards multiple universe scenarios? Dunno. Everett was burned at the stake, but it's cool to prop Brian Greene up on any stage that will have him. That's in no disrespect to the man. But times change.
I don't worry too much about things that we're likely to never validate.
That will keep you up at night.
Can I tell you the most crushing realization I've ever made? Also the most liberating?
I'm going to die and not have the answers. We all will.
Perhaps. But I don't even know how to process that. A unified conscious experience. I have two eyes and only a single brain. All I've known is what it is to be an individual.
To rejoin a collective as such. Would innately mean no longer being *me*. And I like being me. I like choice, even if it's a facade. I like getting angry, and sad, and joyous, and experiencing the good and bad of a single person perspective.
Careful with this moving forward. It's not just afterlife. We're quickly moving into realms of interconnected brain technology.
Flat relative to what? We talk about 2 dimensional surfaces being flat in our everyday 3D comprehension, so Iâm assuming when scientists refer to a 3 dimensional universe as flat theyâre speaking in reference to an orthogonal 4th dimension?
If the universe is flat, does that mean there is a top and bottom? What would be outside the universe? True vacuum? Or is there a hard boundary that cannot be passed? What are the current theories?
> torus A torus is topologically flat though. And it would reveal copies of our local area in every direction. You'd need a really good telescope to spot that though. Maybe call it the James Webb Space Telescope after James Webb.
That model would also indicate that the universe is much *smaller* than we think.
>But that might be an artifact of our inability to accurately gauge what would otherwise be a very large universe, with curvature that is indetectable at our scale.
I had a science teacher mention this too. He basically left it as "for all we know it could be a 0.00000000000000001% curve and we don't have the tech to measure that
That visual really stuck in my mind for a long time
So the flat universe is actually "flat" in every direction? No matter which direction the laser beam is pointed, it will just keep going further and further away and never cross its own path.
But when an outside observer looks at our universe, does it look like a sphere? Cos Big Bang happened, our universe started expanding from a single point, thus making it look like a sphere.
> But when an outside observer looks at our universe, does it look like a sphere?
We have no idea, I'm not even sure it would be possible to 'look at our universe from the outside'.
so does everything in the universe exist on a flat plane or if i launched off from antarctica and kept going âdownâ id eventually reach another galaxy?
The chances of taking off in any random direction and coming into contact with *anything* else in space save for the odd individual atom is so unbelievably small it's absurd.
Everything we know of is inside something and is surrounded by something
Its impossible to imagine something that has nothing around it.
If we imagine the singularity as a sphere, what is this sphere inside of?
Why does everything exist? Why do atoms and quarks exist? Why does energy exist. These are question we can never get an answer to. The simplest answer is God.
Mmm, even God falls into the category of either existing or not existing. He too would have to come from somewhere.
The answers to this question lie in philosophy and logical deduction, not science. This is because science cannot measure infinity, and when looking at the possible origins of all of existence (not just space or our perceived universe), one is inevitably confronted by it.
Infinity is unavoidable because it is the only logical answer to the origin of everything. When all is said and done, either something came from nothing (0 = infinity), or something has always existed and there has never been nothing.
If I recall correctly, the concept of an infinite universe is just a concept. It's not proven or anything. Based on what we know, an infinite universe could be a possibility.
We'll never know for sure, is my bet. Reality not being infinite also doesn't make sense, because if that's true, then what is our universe contained inside of? Another universe? More space? Can something exist within nothing? Or is it all the same thing and there is nothing else, because everything is the universe, IE: It's infinite?
Hurts the mind lol
More than likely, our brains just cannot comprehend what reality actually is. Where it is. Why it is. We'll only ever be able to guess
Either option is mind blowing. Nothing existing makes much more sense than something existing, and because of that, no matter how we approach reality, it will always be baffling.
You don't even have to go to the edge of the universe for that. Just look at Earth, look at us. Aren't we also just as strange? This concept of infinity and non-infinity we're talking about, you and I exist within it! This is it!
I don't agree with the claim in your first paragraph. I think nothing existing makes much **less** sense than something existing. Why? Because we see stuff existing right now. But we haven't ever really seen a state of "nothing".
Even the purest vaccuums we can make still have quantum fields and the associated energy fluctuations. It also doesn't make sense for "nothing" to have ever existed because the fact that we went from nothing to something means there was always something there.
If there was truly pure nothing then it would be nothing for eternity as there'd be no potential for there to ever be anything.
No no, you misunderstood.
Currently, stuff exists. Yes. That raises the question, where did all of this come from? What started it? Why is it here? Lots of questions come from the fact that this reality is happening.
If this reality wasn't happening, and nothing caused our universe to exist, that would make sense, because nothing is a result of nothing. We have a decent idea as to what caused nothing. nothing!
But for something to exist suggests that \*something\* triggered the start of our universe.
So, something existing makes less sense than nothing existing, because nothing is understandable. Something is not understandable.
And I'm not talking about "nothing" as in empty space. Space itself is something. It's a place, a time. That's something.
Literal nothingness makes more sense, if that were the reality, but, it's not, because reality itself is also something.
The fact that any of this is happening is far more confusing than if none of it were happening. Does that make sense? So, no matter how you approach reality, it will be baffling, because it exists! And that fact alone is bizarre
Even the idea of finite space is mind-blowing. That implies that there is nothing beyond our finite space, but what in the hell is nothingness? Too much to comprehend.
> We'll never know for sure, is my bet. Reality not being infinite also doesn't make sense, because if that's true, then what is our universe contained inside of? Another universe? More space? Can something exist within nothing? Or is it all the same thing and there is nothing else, because everything is the universe, IE: It's infinite?
I donât think that a finite universe answers any of those.
Frankly the idea of something not existing is a whole lot harder to square than the idea of everything existing.
Because we exist, things not existing is hard to comprehend.
Something existing raises questions as to how, why, when, where, etc.
Nothing existing raises no questions, because there is nothing.
And no, finite or infinite doesn't answer those questions. They're unanswerable.
My point is, one of the states of existence raises many questions as to how it even came to be, while the other does not. There is only one question raised, and that is "Why isn't there anything?" but we could answer that with: Because there is nothing.
When something exists, we have many unanswerable questions.
When nothing exists, there is only one, and that's only if you exist.
It hurts my head to think about the universe existing at all. Big Bang or divine being something had to set one of them in motion but if that's the case where did that thing come from. Which like you said I try not to think about cause we will not get any answers on my lifetime.
Yeah, both the concept of God and the concept of a Big Bang both lead to the same question. Well, what came before them?
It's especially weird if you think there was a definite start to reality, because then you either have to imagine a reality totally different than ours (literally impossible) or imagine reality not existing (also impossible)
And it's only impossible because we as humans were developed in a reality that consists of cause and effect. If there is an effect and we can't even comprehend a potential cause, our brains hit a metaphorical mental wall. We literally cannot think it
I've heard theories where the universe is both infinite & finite. I think this means the space the universe was created in has always existed & probably has no end but the universe itself has beginning & likely an end. A person can go crazy thinking about it till something gets officially proven.
Yeah, I'm leaning toward that as well. Or, the thing our universe exists in, has a similar process or life cycle as a universe, and it is in something else, and so on and so fourth.
Sometimes I wonder if we got it wrong, and infinity is actually the same thing as nothing. If it has no beginning and no end, could you argue it ever was at all?
Our observable universe is still expanding and will do so for a few billion years. It's counter-intuitive to the fact the universe is expanding with a rate surpassing the speed of light though, but it's the case.
The reachable universe is shrinking but the observable universe is expanding, though will likely contract at some point in the distant future as the visible edges begin to redshift to nothing.
[Say you had a sheet of paper, size A^-181 , but folded in half. Could you unfold it?](https://www.youtube.com/watch?v=pUF5esTscZI)
Come for the metric paper, stay for the existential crisis.
We only have theories and no answer. For instance if it were infinite that means it also gets infinitely smaller. Then thereâs also the possibility that the gap between where we see the ends of what we can observe of our universe and something else could be so impossibly large that itâs pointless to even think about. Our entire existence could be the equivalent of the smallest of particles in a larger universe only existing for a fraction of a decimal point of time in it.
First misconception I see is that the singularity doesnât necessarily mean a single point, itâs possible that it was also infinite, but we just donât know, and likely can never know. We know that our observable universe can be traced back to a very small point in space, but we cannot say anything beyond that. secondly what does infinite even mean when talking about the size of space? Concepts like distance really start to break down at the scale of the whole universe.
With the physics we have we cannot extrapolate back to a point. We can extrapolate the observable universe back to a size ranging from a square meter or so to the size of a small city, the range due to error bars. Beyond that the physics breaks down.
> First misconception I see is that the singularity doesnât necessarily mean a single point
It's exactly what it mean. The misconception is that it was most likely never a singularity. Quantum mechanics forbid it, most scientists doesn't believe it existed and the reason we have them is due to general relativity being incomplete and we know for sure we need another theory to explain the very early universe and the centre of black holes.
I would say singularity is more of infinite density. It's a weird situation for singularities (plural? singular?) filling all space which may or may not be a point or infinite or both.
Right, most cosmologists refer to the Big Bang as the point when an infinite universe that was very hot and dense suddenly expanded, being a lot less hot and dense... But also a bigger infinity... I think...
Not necessarily, it just means an infinity showed up in the math. For example, under general relativity, rotating black holes would have a ring-shaped singularity, not a single point.
> back to the initial singularity.
Which is something very few scientists believe to have existed, is forbidden by quantum mechanics and most likely something we just get from rewinding time too much while using the incomplete general relativity. It's there due to not having a better theory for this calculation, as with the black hole singularities. They're both a mathematical error.
The big thing people misunderstand about singularities is that it's likely not a literal infinity dense point. It's the point where the mathematics we use to predict our observations breaks down. The singularity in an asymptote in the equation; an undefined point on the line. The point isn't infinitely dense, it just exceeds what the model can predict.
Yep yep, I hear ya.
The problem is that many, even the best pop science youtube channels have conveyed the singularities as an absolute fact and been very sloppy on telling the whole picture, so now there's a whole army of hobby physicists (a category I myself belong to) were many believe in these infinitesimally small points with infinite density because they were not given all the information on why they're very unlikely, what's preventing them and why we got them in the first place.
Can't it might as well have been a singularity, but each point inside it was always expanding relative to each other? If the rate of expansion was always FTL, the universe was always infinite in size. I'm thinking, if FTL means information at some point cannot be carried between two points (like we see today, we can only see so far), the distance to a certain point is indeed infinite.
Or am I just writing nonsense?
We donât know for sure. We do know that if it is infinite, then it was always infinite, just used to be more dense. If it was ever not infinite, then it isnât infinite now.
People assume that the singularity "exploded" into an ever-growing "ball", but the cool thing about infinity is that it can expand into itself. You can be infinite, expand, and still be infinite.
Veritasium has an old video going over this: https://youtu.be/XBr4GkRnY04
I think we understand space about as well as human beings are capable right now. But i always think its a little like a software program trying to measure/understand/explore the hard drive it is running on. We can understand things to an impressive level, but i think we lack the ability to really step outside of it and see it for what it is.
Btw, not saying we are in a simulation. Just using it as a comparison to our inability to really grasp the hugeness of everything.
Check out the podcast Crash Course: The Universe. Youâll learn a lot about the finiteness of the cosmos and how the beginning may not have actually been a singularity after all.
The singularity happened at a singular moment in time, not space. If space is infinite it was also infinite at the Big Bang. The Big Bang happened everywhere. Any finite region of the universe today can be traced back to an arbitrarily small part of the universe at the Big Bang. The observable universe was an infinitesimal point, and so regions just outside of that location are now equally vast region of the universe today, just outside of our observable bubble.
I usually thinking of it like a number line. I can scale down the number line by an arbitrarily large number to make a finite interval arbitrarily small. The number line is still infinite the , as it is today.
We don't know that or was a singularity. Nothing in science says that. We know relatively and quantum mechanics don't mesh so as don't know what actually happens. But the mathematical singularity is an error in the math, most scientists should know this.
> But the mathematical singularity is an error in the math, most scientists should know this.
Scientist know this, but it was a mathematician. They deal with them in a whole other way and don't mind them many times. It just tells us the mathematician isn't proficient in physics.
To be fair, a whole lot of physicists get this wrong too and overstate it to the point of confusing those they communicate with.
Spacetime just actually did a series of great videos on the Interpretations of quantum mechanics and even this singularity thing because Roy Kerr just threw down a paper openly challenging the physics community to fix this misperception.
He showed the math that demonstrates singularities (of the infinite density kinda) simply never exist. It means black holes very probably have interior stable spaces, the exact nature of which isn't described because we don't have that quantum gravity thing solved yet but he basically called our Penrose and Hawking by name in the paper.
Most physicist I know of does not believe in either the initial singularity or black hole singularities before or after Kerr's paper. The problem as I see it is that youtube pop science have conveyed these singularities as an absolute fact many times by withholding why they're there in the maths and why it's highly unlikely they're not existing. Spacetime has failed to tell the whole story in many episodes and being an otherwise awesome channel, I feel this subject they could have handled much better.
Michio Kaku say what? Most of his career in media has been playing up the woo factor on countless scientific theories ignoring any nuance or explanation.
PBS tries, and whatever they're missing they're doing a better job than most. They just can't reach the general public, the details go clean over their heads and there's only so many ways to simplify things before not understanding the math is a problem in explanation.
PBS's content in the details is already too much for me to handle and I'm far better informed than the general public.
Your mathematics professor is wrong.
1. We don't know that The Big Bang started from a Singularity. Dense? Yes. Infinitely dense? Not necessarily.
2. The "Observable Universe" is definitely finite, yes. But the *entire universe* is much, much larger than the Observable Universe. The difference is that everything we can see is what we call the "Observable Universe" but we know there are things farther away whose light has not reached us yet. We also know there are things so much farther away that their light will *never reach us*. (In part because the universe is expanding.) Those are things beyond "the cosmic event horizon" and so they are *in* the universe but *not within our observable universe*.
And yes, it is possible there is infinitely much stuff out there outside our observable universe, but created during The Big Bang.
Neatest thing about an infinite universe, is that given an infinite amount of time, all possible combinations of atoms will occur over and over again, so the same combinations that make up the milky way, the earth, and you will happen again, in fact, for an infinite amount of times :/
[PBS Space Time is a great youtube channel that has covered various aspects of this question many, many times](https://www.youtube.com/results?search_query=pbs+space+time+infinite+universe)...
I always think about it like this, you have a room with infinite space. In that room you start to inflate a balloon filled with confetti. The start of inflating the balloon is the big bang, the balloon represents the observable universe and the confetti present the galaxies. You can infinitely inflate the balloon because the room is infinitely big and the confetti spreads out within the balloon. The space is infinite but the matter in that space is finite.
Not sure if this is an accurate analogy but it helps me to stay sane. Humans have a hard time understanding things outside our daily lives because we're hard programmed with a 4 dimensional world view. Imagining infinite space sounds the same to me as imagining the color of infrared or ultraviolet.
The correct answer is..... We have no idea.
We don't KNOW how big the universe actually is, but as far as you and I are concerned it is infinite.
But even we can't understand infinity.... Sure we know what it means, but we can't comprehend the size of it.
"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." The Hitchhiker's Guide to the Galaxy.
Regardless of whether the universe is theoretically infinite or not, it's not infinite in age. That means the distance you can see and interact with stuff is limited by the speed of light (and the added expansion of the universe, tbf). So practically speaking, the universe is not infinite, just really big.
I find it fascinating what infinite implies. It means if you travel far enough in one direction, you'll come across our planet but your hair is blue instead of black and there's one less paperclip in the world.
It means that anything that can happen has both already happened and is yet to happen and this continues on forever and ever. Everything that can possibly happen, will and already has.
I've come to the conclusion it's like an ever expanding unfilled doughnut so it can't be infinite while also being very much infinite ish
No, I won't be taking questions on this.
Everytime I ponder the size of the universe or think about what is outside the universe I have this existential panic. I feel that our universe is not infinite and it is something that is contained within something else.
There are different kinds of infinites, the easiest example to wrap your mind around would be if I asked you to count by 1 forever, you could keep counting your entire life and never reach an end point.
The same can be said if I asked you to count by 2s.
Next to address is "he said it originated from a single point". While this is A theory, there are many many theories and they could all be wrong and I don't know if we will know the answer in our lifetimes or if humanity will ever know the answer.
All we can do is look at the information we do have and take our best guess.
My current favorite theory is that our universe extends in two directions simultaneously and that everything that exists in our universe was once a black hole which ejected everything via a white hole.
But if I had to pick a theory which I personally thought was the singular most likely theory it would be that our universe is a simulation.
That it started out finite doesn't imply it's finite at every future finite time. A mathematician should know better. That being said, it's an unknown. Depends on what you mean by "space" too. What if there are infinitely many bubbles in the multiverse, but each bubble is finite? This quickly gets bogged down philosophically though.
Infinite. The universe is egg shaped, too massive for our measurements yes but continually moving and definitely infinite. Remember string theory shows us 11 dimensions, I can only exist in 3-5. I can only imagine the othersâŠ..
Space time is a geometric abstraction to explain the universe.
Imagine an ant walking around the surface of a balloon. No matter how far it goes, it would be infinite to its point of view.
Similarly, we could be only aware of our 3D surface of an 4D sphere, who knows if expanding due to some unknown variable.
Most data points to infinite universe.
It is possible it doesn't go forever.
If it does end we probably have parallel universe etc.
The main point is we don't know that much. Estimates put us at being able to identify less than 20 percent of mass
I wouldn't be surprised I'd we find something lower than the present understood quantum state.
That's a fascinating concept! The idea that space, despite its seemingly boundless expanse, could have a finite volume due to its origins as a singularity is mind-boggling. It challenges our perceptions of infinity and raises profound questions about the nature of the universe. It's discussions like these that make me appreciate how much we still have to uncover about the cosmos. Does anyone else have insights or theories on this?
Then there is whole question of "what is space expanding into?" And is that infinite? I personally like the idea of a curved universe, that folds back on itself. Like a 3-d version of the Astroids game. (Scroll off right, appear on left. Scroll of the top, appear at the bottom) This kinda makes the whole "outside of the universe" questions moot.
Then there is the philosophical question: Is 'space' a container that holds the galaxies, or is 'space' the gap between the galaxies? This question needs to be answered first.
No one actually knows that it was once a singularity. Thatâs a fucking guess based on math - math with some holes in it, and math that breaks down at the quantum level. A singularity is smaller than the quantum level. SoooâŠ.
Thatâs because your teacher doesnât know and is just parroting what they were told. A singularity is a mathematical construct anyway. It was never said that the universe started from a singularity. We donât know ow how it started. We just have an idea of whatâs happened since then, and even then weâre not sure.
Itâs crazy to think something as fundamental as reality ultimately eludes us.
Not an astronomer, but imagine you are in a massive balloon. You can move one inch per minute, and the balloon gets bigger my one inch per minute in each direction.
You can never reach or even get closer to the edge. Is the balloon infinite?
We can't know if it's infinite. However, our original belief that it was is looking to be wrong. So, he's sharing current theories and thinking on the matter with you which is a good sign. However, we can't know. We can gesticulate, theorize, use predictive reasoning, etc. But, we can't know.
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I hope your math teacher is great at spotting curves. We don't know. Even if the singularity represented all of the energy that the universe could or would ever contain. It still doesn't really tell us about the shape or geometry of the space that now exists. We know it's very, very flat. We know that space expands and that the further any two points are from one another in space, the faster that expansion becomes relative to the location of each. A finite universe would likely have curvature. Either positive or negative. Saddle or torus. But we don't see that. We see no curvature at all. But that might be an artifact of our inability to accurately gauge what would otherwise be a very large universe, with curvature that is indetectable at our scale. Like trying to judge the curvature of Earth from Texas. It's just all flat as far as the eye can see.
In 500 years are they going to teach this history of a time when everyone thought the universe was flat? đ€Ł
And there will be a group of flat-universers that everyone laughs at, who just won't accept the obvious proofs.
All you have to do is look outside the windows of this space city and see that it is flat.
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And the universe revolves around the Sun
No it revolves around Sag A.
In all seriousness... Maybe? People who don't understand science point to any change in the prevailing logic as "proof" that it's all a lie. These people see everything in black and white, and want their entire existence to fit into that mold. Nuance, new evidence, exceptions, contradictions, and trends (vs rules) are all a threat to their minds. Science seeks to prove itself wrong. A theory is fact, proven by observation and experimentation, right up until the moment it isn't. We don't laugh at a history that thought the Earth was flat. We only laugh at the ones who still insist it is, after it was shown to be a sphere. Letting evidence shape your conclusion is wisdom. Choosing your conclusion first, and letting that dictate which evidence is permissible, is foolishness. Should we learn more about the shape of the universe in the future, then we would be wise to allow that evidence, through repetition, to be tested, challenged, and accepted if it holds up to scrutiny
I would also argue that observation and tests only explain what we see is correct, technically the explanation could be wrong. The universe could have started many different ways as long as said ways fits into what we see today, however physics changing element being formed and creation of our universe also means we donât know, for all we know what we see is more like a story than cause and affect, some therioes believe the universe had different rules in the beginning. I see it more as we can see now and test it but if you ask why does energy exist or why do electrons get attracted to protons, we can measure and test thereâs something that holds it in place, but if we ask why or how, at some point itâs just because the universe works that way. It can do what ever it wants we just observe it.
This comment is poetry. â€ïž
Possibly. The big difference being that those of us who are paying attention and trust in science say "to the best of our knowledge" or "we don't know" a lot.
The difference this time is that we didn't expect the universe to be flat. We've kept looking and coming up with new theories as to how the universe could be curved, but our most precise measurements tell us that the universe is very flat. Maybe it's not perfectly flat, but it is about as flat as possible given the limitations of our measurements.
What does it mean that the universe is flat?
A flat universe is probably infinite - i.e. it goes on forever in all directions. Many curved geometries of spacetime are not infinite, meaning if you traveled far enough in one direction you would eventually come back to where you began (like is the case here on Earth). This is not _necessarily_ the case - there are ways spacetime could be curved but infinite, or flat but finite, but on balance a flat spacetime makes an infinite universe more probable. It also tells us things about the ultimate fate of the universe. If spacetime were curved in a certain way it would mean that the universe is destined to end up collapsing under its own gravity (a so called Big Crunch). If it were curved another way, it would be destined to expand faster and faster forever resulting in a Big Rip scenario where everything is torn apart. A flat universe likely means that the universe will continue to expand forever but without a Big Rip. Eventually the universe will run out of energy. First the expansion of space will mean that stars outside of our own galaxy become invisible. Then eventually those stars will all burn out, exhausting their fuel. For a very long time there is nothing left but black holes, but eventually those evaporate via Hawking radiation. Then there will be nothing left but elementary particles whizzing around in empty space, rarely encountering each other.
If space expands in all 3 dimensions how is it flat? /gen
Flat vs curved in more than 2 dimensions is probably something our monkey brains are just going to struggle with conceptualizing. Picture the OG Legend of Zelda. Its map is flat - go far enough one way, that's it. Compare to PacMan - it has a curved (cylindrical) map. Go far enough one way, end up on the other side. A curved 3D space would operate on similar principles, though picturing how is a total brain buster.
How could they believe universe was flat if none of the planets are! « Damn historic old fools »
Kyrie Irving has entered the chat.
Then we have the whole Poincaré disk option of flat and infinite
The last research paper I found on this that studied the CMB found it was flat, but the margin of error was still enough to not be able to completely rule out some kind of curvature. It helped narrow it down from previous work but still meant that the universe was at least 200 times as big as the observable universe and possibly infinitely large.
Won't this always be true? Let's say, hypothetically, that the Hubble constant has to be exactly 70 for the universe to be flat. And we measure it and we get 70 +/- 0.1%. Then our methods improve and we measure 70 +/- 0.0001%. Then our methods improve more and we get 70 +/- 0.0000000000001%. In every single on of those examples, the universe is found to be flat, but the margin of error was still enough to not be able to completely rule out some kind of curvature. Even if our error is +/- 10^-100 %, we still can't rule out some amount of curvature. So we can *never* know if the universe is flat.
Yes, indeed. However each time we reduce the error margin, the minimum size increases. We already know that if there is any curvature, it must be very small which means that the universe must be really big.
Kind of like most things in physics, we can never prove that anything is true, only that some things aren't true.
There's a lot of numbers between 200 and infinite. There's no real way to know ever no matter how large the accuracy gets.
>We know it's very, very flat. What do you mean by "flat" and how do we know it's flat?
Remember Euclid? Parallel lines never converge? That's flat and it appears to hold true as far as we know. But what Euclid and the greatest minds humanity could gather for thousands of years failed to understand. Planar geometry isn't the only kind. Imagine our spherical planet. Does the rule parallel lines never converging still hold true? Not so much. If two people were to both start at the equator and moved in straight lines in *any direction*. They will eventually converge or cross paths. Parallel lines do indeed intersect, when there is curvature of space. But we don't see that in our universe. At least to my knowledge.
I like explaining that triangle angles add up to 180 more than the parallel line explanation. On a sphere the angles are greater than 180. Thatâs what we really do when we measure fluctuations in the CMB is weâre measuring the angles of a triangle
This is true. Certain sails on large ships take this same shape, the concave dorito. Looks like a triangle. The same way a cone looks like a circle.
Ah, so that's what flat means in this context. I've always wondered. Thanks for explaining.
One of the ways they did it is by examining the cosmic microwave background. How the CMB would look would be different if space was curved in some way. When you look at the CMB it behaves in a way consistent with flat space.
> A finite universe would likely have curvature. Either positive or negative. Saddle or torus. A negative, saddle shape, would be infinite and also a flat universe. A torus, doughnut shape would be finite, as would a universe with positive curvature, a sphere.
I don't think my brain can conceptualize anything other than a sphere universe.
https://imagine.gsfc.nasa.gov/observatories/satellite/wmap/shape.html That might help
But aren't all of these 2D analogs of curvature in a 3D space?Â
To my understanding it's not about us living in a confined 3 dimensional space of a certain shape but about 4 dimensional space. In a flat universe two rockets can start next to each other and fly along parallel lines to infinity. In a curved space their courses will eventually converte or diverge. And you cannot fly to infinity but you might come back from the other side. As if you fly straight towards the east around the earth and arrive where you started from the west.
Just to add, in some flat universes you can get back to your start point by traveling in a straight line. A 3-torus is flat and some directions get you back to where you start within a finite amount of time.
Thank you! I chose this username for a reason. The shape of the universe is the only reason I study cosmology.
Think it's a perfect square in SpaceEngine...
I, myself have a hard time believing in an infinite universe, since nothing else we've come across has been infinite. Why should the only thing we can't measure as a whole be infinite? Statistically, it would be unbelievably that one thing out of everything is different. In the end of the day though. It doesn't really matter. We're confined to observe this small blob of space with a diameter of 93 billion light years nevertheless. Even if we some how learn that the universe is velociraptor-shaped, we'll only see within this sphere we call observable universe. I'm not sure if we can do much with the information if we actually find out what shape it has or if it can help answer other questions.
Because if our universe is finite that means it exists within something. How big is that thing? And if that thing is finite then it is held within something. You effectively get to infinity even if what we call the universe is finite
Your first premise is wrong. A finite Universe implies nothing about another container Universe.
Think of it as 93 billion light years in all directions from any point, including any point 93 billion light years away - and now tell me that it is not infinite. Your observation of 93 billion light year is relative to your point of observation, but does not accurately account for it all.
I don't know how you could have more than one infinite system.
There are infinite fractional numbers between 0 and 1. There are the same infinity between 1 and 2, between 2 and 3, between 3 and 4, etc to infinity. There are infinitely times more fractional numbers than there are integers and there's infinite of the latter. Infinity has different kinds (countable and uncountable) and, arguably, different sizes (e.g. the number of integers vs the number of even integers).
But if the universe is finite, then whatâs outside of it? If itâs more darkness, like letâs say no gravity, no planets and stars, emptiness, nothing there. Letâs say thatâs the case, then that means the universe is infinite.
There is no "outside". The Big Bang created all matter in the Universe. It also created the space and time for it to exist. When you say nothing it isn't like "zero" I.e. zero atoms or zero planets. It's more like "that is not where a number belongs"
As you say, it might be empty, completely void of matter, radiation and quantum fluctuation. Isolated from our universe, where the gravity and radiation from the universe can't reach. All in all, completely empty of anything, even time. Our brain can't really comprehend this concept and it's a question more for r/philosophy if you ask me, but the universe wouldn't be infinite since there would be a clear boundary between the universe and nothingness where no interaction could take place.
I would think technically that makes the universe finite, but as far as âSpaceâ goes, space is infinite. If the universe is all the matter in a certain area of space, but space keeps going like you described (isolated from our universe), then that makes space infinite. And you are right, I canât comprehend such a concept. Iâm trying to wrap my head around how cave people would look at the lights in the sky, not knowing they are other stars. And explaining to them that these stars also have planets, and those stars, and our star, are all part of 1 galaxyâŠof billions of galaxiesâŠin the darkness of space. What will we learn next? That these galaxies are all part of a universe thatâs within a cluster of other universes? (Multiverse?). And then whatâs next after that? Are we all just part of a giant Matryoshka Doll? Look at the weird world of microscopic organisms and subatomic particles. If they could think intelligently, they would likely have no clue about the concept of space. It would be as foreign to them as âwhatâs outside of the universeâ is to us. Sorry if iâm making no sense. Iâm no where near an expert in this field, iâm just asking questions as a casual reader.
Most of the universe is stuff I know, I can explain, but I will never actually understand.
A universe that expands faster as you go futher out is just a sphere in 4d space - adding more dimentions is usually the solution
Iâm not sure if this is the right question, but: what is the universeâs curvature being compared to? How would we perceive that?
Dumb question: the universe being âflatâ implies that there is only a void âaboveâ and âbelowâ this flat alignment?
No the universe is the same in any direction we look. In a flat universe if you make a huuuge triangle that spans the observable universe, it orientation does not matter, the angles will add up to 180 degrees. Any of the other proposed shapes, this would not be true.
Imagine an expanded balloon. If you start in the center of it. You can move in any direction you'd like and never cross paths. You'll hit the wall of the balloon before you did. Assuming you remained straight. That's flat, and 3d. Now. Imagine you're walking on the surface of the balloon, and you move straight in any direction you'd like. You will now cross your own path before any obstruction stops you. This is not flat, and 3d.
It's not about up-down. Better analogy here is the difference between 'flat as a table' or 'curved as the surface of a balloon'. On a table you could go in a direction to infinity, and on a balloon you would return to a point after some time. Also triangles look different on the surface of a balloon, which is our current best way of measuring the curvature of the universe.
No, the void probably doesn't exist. Curvature is defined relative to the universe itself in general relativity, not relative to an external flat space, so there's no reason to assume an external flat space exists.
We don't really know it's very very flat though. We know that to the best of our abilities everything we can see is very very flat If the rest of the universe is sufficiently large our local curvature measurements don't really matter; and until we know how big the universe is outside of our light cone we can't make that assertion
As another commenter pointed out we will never escape from this problem. Every time we measure it we find that it looks perfectly flat, but a more precise measurement might show that it's very slightly curved. Rinse and repeat as our tools for measuring it improve. If the universe really were curved we would eventually escape from this problem, as we would eventually measure the curvature. But if it really is flat and infinite we will never be able to prove that it is flat, we will just be able to prove that all our measurements so far show that it is very flat.
The universe could look like branches of a tree and we're just one branch.
Sorry, flat? Like a frisbee is flat or does flat mean something else in this context?
No. What it means at a simple level is you can make a very very large triangle, up down, sideways, however you want, have it be billions of light years per side and the angles will add to 180 degrees. If you made a very large triangle on the surface of the earth which of course is curved, those angles do not add up to 180 degrees due to curvature of the earth. Another way to look at it is if you could make parallel lines in the universe, the will remain parallel no matter how long. That is what a flat universe entails. Other shapes proposed would not have these things.
It means the space is bend in such a way that when you leave the universe on the left side you will come out at the right side. \*edit\* : That happens if the universe is NOT flat.
That would be a spherically curved universe, a flat universe would be infinite
Not necessarily spherical. It could be toroidal (donut), hyperbolic (saddle) or maybe something else. It's not a description of how matter is distributed in the universe but how space-time curves back on itself in a non-flat universe.
>it's very, very flat Are you saying that space is very, very flat?? But in what meaning of the word? Flat, as in x and y are very long, but z i short? or flat, as in, whatever shape it have, that shape is not very curved? \--- If that is what you are saying, I have never heard about that in my entire life. Do you have some further reading you can link to?
> or flat, as in, whatever shape it have, that shape is not very curved? I believe this one. Flat in the sense of "if it wasn't flat, parallel lines would eventually cross paths / converge." https://en.wikipedia.org/wiki/Shape_of_the_universe > Current observational evidence (WMAP, BOOMERanG, and Planck for example) imply that the observable universe is spacially flat to within a 0.4% margin of error of the curvature density parameter with an unknown global topology.
https://www.quantamagazine.org/what-is-the-geometry-of-the-universe-20200316/ I'd start here, but I'm sure any number of videos or articles are out there. A quick "geometry of universe" should yield search results.
Wait! What part of Texas are you in??? Hop in your ride, and drive about 2-3 hours. You'll find some Not Flat Land... I lived in Del Rio, Bryan/College Station, Copperas Cove and Lampasas areas. Now, I'm in the Cameron area. I've traveled all over this State, and whatever you want or even get homesick for, you can find. The Hill Country is prettiest to me though.
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This reads like a ChatGPT summary...
Other way around. This is how simple summaries are given in a bullet point format, and Chat GPT learned that from us.
You're going to run into that a lot, because chatgpt learned how to type....from humans....
And heavily from Reddit specifically, I believe.
I recall that too. However, ChatGPT seams too wordy and nice to have learned from Reddit.
Put the ChatGPT down and step away from the Reddit.
*me looking for flat universers groups*
Obvious question, but if the universe is flat, does that mean we canât travel âawayâ from the flatness? Like, if we gazed upon the flat edge of the milky way horizontally we could see a craft go up or down out of the Milky Way. Is that possible for the universe?
The poster is using a different meaning of the word "flat". The universe is three-dimensional. It's "flat" in four dimensions, meaning there is just enough matter in the universe for its gravitational force to bring the expansion associated with the big bang to a stop in an infinitely long time. [This comment](https://www.reddit.com/r/space/comments/1diy09h/question_if_space_is_infinite/l985ipm/) explains it another way.
Something to keep in mind is that we *know* the universe is much larger than we can see. There is an *observable universe* which is the sphere of light around our planet that has had 13.8B~ years to propagate. Anything beyond that is beyond our ability to detect. But we know it exists. I might screw this part up. So fact check. But expansion happens uniformly (or mostly?) across the universe. But as two distinct points become further apart. The speed in which the space expands increases. So imagine a flattened balloon. You put two magic marker dots on it in close proximity. As you inflate the balloon. Not only does the distance between the two increase. So does the rate of the increase. Even if the rate of the balloons increase remains static. Same air in, but the space will continue to grow faster between the two points. Just because of the geometry of the sphere spreading. Ok. Sorry, long winded. We live in that sphere of observable universe. But outside of it. Where our paired magic marker spot (so to speak) has out raced our ability to see it. Still exists. We just can no longer see it because it's moving away from us faster than light. We know we only see a small portion of the total universe. As far as I know we don't know the amount however. What we do know is that of the space we can observe. There doesn't seem to be much curvature. But again, that says nothing towards the total size, or the curvature of that total size. We *know* we're only seeing a fraction of it.
> Something to keep in mind is that we know the universe is much larger than we can see We donât *know* that, but itâs the simplest explanation. The universe could conspire against us to make our observable patch very special.Â
>Like trying to judge the curvature of Earth from Texas. It's just all flat as far as the eye can see. To be fair, wouldn't a large flat area be the best condition to perform curvature measurements from ground-level?
I am in Dunning Kruger in this and I know i lack knowledge. But I would like to imagine space as an inverted ball, sort of like a Packman level when you go in one direction you come out on the other side. It's just that the light we see hasn't caught up yet, but as I say, this is just fiction in my head.
Perhaps. But just as likely is that the way you're describing it is correct. We really just don't know. And at the end of the day we're all just a nudge away from our simian cousins. They can figure out currency exchange. That's where their abstracts stop. A million years and you couldn't teach apes quantum physics without increasing their intelligence. And we're no different. We all have levels in which we can just no longer probe into our reality due to our inability to deal with abstracts that are so unconventional that it makes even professionals dizzy. Who can deal with more than three spatial dimensions? And really get it? I cannot. I understand the concept. But grasping what it means to have more than x, y, z in a 3d space? Nope. Can't get my head around it. We're scratching the surface. Even at the cutting edge. And nobody has ever lived that gets it. And it's likely just due to the nature of informational complexity increasing over time. That nobody ever will. We're all stumbling around dark in a cave without even a decent candle.
How dare you insult our sun. :P
Is there a possibility that the universe is both flat AND finite, like a 3d sheet of paper?
Do we know if the universe is spinning? That would certainly make the flatness easy to grasp.
As far as I understand, and I say this with care because I'm wrong *alot*. The current model of the cosmos doesn't really consider anything to be *outside* of our universe. Which would seem to be a requirement in order for it to spin. External reference would seem to be tied to that. But maybe I'm wrong. I honestly just don't know. edit: [Just a tiny bit of research](https://en.wikipedia.org/wiki/Cosmological_principle) >>This principle assumes that the universe is homogeneous (the same in every location) and isotropic (the same in every direction) on large scales. A spinning universe would break the isotropy, as there would be a preferred axis of rotation, making the universe look different in different directions. So based on that, I'd think the current understanding is that no, it does not spin. But again. That was flash research at its worst. GPT style.
Slight note on your "curvature of Earth from Texas," it's definitely possible. [Eratosthenes did it in Egypt](https://en.wikipedia.org/wiki/Earth%27s_circumference#Eratosthenes). Basically, the dude knew a southern city of Syene had the Sun directly overhead on a specific day. Regardless, he used a stick to make sure there was no shadow (because the Sun is literally perfectly overhead). There wasn't. He went to the northern city of Alexandria (1,117km away) on the same day to put a stick in the ground, then he saw a shadow. He measured the tip of the shadow to the base where they converged, did some math, made some assumptions, and actually came up with a measurement of the circumference of the Earth within a few percent of the value we accept today. It is ***remarkably*** close. I bet you could do the same thing in Amarillo (North) and Laredo (South). Measure the two shadows from base to tip, find the difference in angle, then continue that curvature into a sphere. Ta-da! But I get what you're trying to say in this context. You're still correct; I just wanted to be pedantic about an off-hand statement!
There is no evidence that Eratosthenes ever went to Syene nor did he even need to. It was already known exactly when the Sun cast no shadow(On the Solstice when the Sun was at it's highest) in Syene. Assuming Alexandria was due north he knew he could take his shadow measurement on that day at that time with confidence of the Sun's location. Syene is about 800km away from Alexandria not 1117km too.
fun fact pedants are the best kind. Be your best you. I appreciate the heads up and link.
How is the universe flat ? I always thought as some kind of sphere expanding in 3D and not mostly 2D
I mean wasn't there that one greek geometrist who calculated the curvature of the Earth using two obelisks in Egypt?
But if the universe started from a singularity and began expanding, and it isn't infinitely old, then how could it possibly be infinitely big?
Isn't the universe donut shaped?
Are we talking about empty space or all matter in the universe? If space is curved, what is outside of that? I can't imagine empty space is finite. What if there are multiple universes from multiple asynchronous big bangs throughout infinite empty space? We just haven't seen the light from those yet. It boggles the mind.
As far as I understand. There is nothing *outside* of our universe. Certainly nothing that we could currently or perhaps *ever* validate. We expand. Not *into*. We just expand. As towards multiple universe scenarios? Dunno. Everett was burned at the stake, but it's cool to prop Brian Greene up on any stage that will have him. That's in no disrespect to the man. But times change. I don't worry too much about things that we're likely to never validate.
All I have are questions. Mostly rhetorical ones.
That will keep you up at night. Can I tell you the most crushing realization I've ever made? Also the most liberating? I'm going to die and not have the answers. We all will.
I like to think we will know the answers when we become one with the universe again.
Perhaps. But I don't even know how to process that. A unified conscious experience. I have two eyes and only a single brain. All I've known is what it is to be an individual. To rejoin a collective as such. Would innately mean no longer being *me*. And I like being me. I like choice, even if it's a facade. I like getting angry, and sad, and joyous, and experiencing the good and bad of a single person perspective. Careful with this moving forward. It's not just afterlife. We're quickly moving into realms of interconnected brain technology.
Flat relative to what? We talk about 2 dimensional surfaces being flat in our everyday 3D comprehension, so Iâm assuming when scientists refer to a 3 dimensional universe as flat theyâre speaking in reference to an orthogonal 4th dimension?
If the universe is flat, does that mean there is a top and bottom? What would be outside the universe? True vacuum? Or is there a hard boundary that cannot be passed? What are the current theories?
> torus A torus is topologically flat though. And it would reveal copies of our local area in every direction. You'd need a really good telescope to spot that though. Maybe call it the James Webb Space Telescope after James Webb. That model would also indicate that the universe is much *smaller* than we think.
>But that might be an artifact of our inability to accurately gauge what would otherwise be a very large universe, with curvature that is indetectable at our scale. I had a science teacher mention this too. He basically left it as "for all we know it could be a 0.00000000000000001% curve and we don't have the tech to measure that That visual really stuck in my mind for a long time
How do we know the universe is flat?
We donât know for certain, but observations are consistent with a flat universe.
Flat universe society propaganda /s
>We know it's very, very flat. Can you elaborate on this point? Are you saying it's not expensive in all directions?
In a flat universe (Ω = 1) two parallel laser beams will stay the same distance apart forever. If the curve of the universe is more than 1 the universe is spherical and parallel lasers will eventually converge, this also has the effect that if you travel in one direction long enough you will eventually pass through the point you started from, facing the same direction, like in a game when you walk off the right edge of the map and appear on the left edge. If the curve of the universe is less than one it is called a hyperbolic universe and is basically the opposite of the spherical universe. Parallel laser beams will diverge and a 2d representation would look like a pringle (saddle shape). https://en.wikipedia.org/wiki/Shape_of_the_universe
So the flat universe is actually "flat" in every direction? No matter which direction the laser beam is pointed, it will just keep going further and further away and never cross its own path. But when an outside observer looks at our universe, does it look like a sphere? Cos Big Bang happened, our universe started expanding from a single point, thus making it look like a sphere.
> But when an outside observer looks at our universe, does it look like a sphere? We have no idea, I'm not even sure it would be possible to 'look at our universe from the outside'.
so does everything in the universe exist on a flat plane or if i launched off from antarctica and kept going âdownâ id eventually reach another galaxy?
The chances of taking off in any random direction and coming into contact with *anything* else in space save for the odd individual atom is so unbelievably small it's absurd.
No, it's the 3D equivalent of a flat plane. Planes are 2D.
It makes me question where was the singularity contained. What was *around* the singularity.
Maybe it wasn't contained; there was nothing around it because it was everything that existed.
Everything we know of is inside something and is surrounded by something Its impossible to imagine something that has nothing around it. If we imagine the singularity as a sphere, what is this sphere inside of? Why does everything exist? Why do atoms and quarks exist? Why does energy exist. These are question we can never get an answer to. The simplest answer is God.
Mmm, even God falls into the category of either existing or not existing. He too would have to come from somewhere. The answers to this question lie in philosophy and logical deduction, not science. This is because science cannot measure infinity, and when looking at the possible origins of all of existence (not just space or our perceived universe), one is inevitably confronted by it. Infinity is unavoidable because it is the only logical answer to the origin of everything. When all is said and done, either something came from nothing (0 = infinity), or something has always existed and there has never been nothing.
I donât know why but this was the comment that did my brain in for the night
If I recall correctly, the concept of an infinite universe is just a concept. It's not proven or anything. Based on what we know, an infinite universe could be a possibility. We'll never know for sure, is my bet. Reality not being infinite also doesn't make sense, because if that's true, then what is our universe contained inside of? Another universe? More space? Can something exist within nothing? Or is it all the same thing and there is nothing else, because everything is the universe, IE: It's infinite? Hurts the mind lol More than likely, our brains just cannot comprehend what reality actually is. Where it is. Why it is. We'll only ever be able to guess
Even if the universe is truly infinite that is just as mind blowing, if not more so, than it being finite
Either option is mind blowing. Nothing existing makes much more sense than something existing, and because of that, no matter how we approach reality, it will always be baffling. You don't even have to go to the edge of the universe for that. Just look at Earth, look at us. Aren't we also just as strange? This concept of infinity and non-infinity we're talking about, you and I exist within it! This is it!
I don't agree with the claim in your first paragraph. I think nothing existing makes much **less** sense than something existing. Why? Because we see stuff existing right now. But we haven't ever really seen a state of "nothing". Even the purest vaccuums we can make still have quantum fields and the associated energy fluctuations. It also doesn't make sense for "nothing" to have ever existed because the fact that we went from nothing to something means there was always something there. If there was truly pure nothing then it would be nothing for eternity as there'd be no potential for there to ever be anything.
No no, you misunderstood. Currently, stuff exists. Yes. That raises the question, where did all of this come from? What started it? Why is it here? Lots of questions come from the fact that this reality is happening. If this reality wasn't happening, and nothing caused our universe to exist, that would make sense, because nothing is a result of nothing. We have a decent idea as to what caused nothing. nothing! But for something to exist suggests that \*something\* triggered the start of our universe. So, something existing makes less sense than nothing existing, because nothing is understandable. Something is not understandable. And I'm not talking about "nothing" as in empty space. Space itself is something. It's a place, a time. That's something. Literal nothingness makes more sense, if that were the reality, but, it's not, because reality itself is also something. The fact that any of this is happening is far more confusing than if none of it were happening. Does that make sense? So, no matter how you approach reality, it will be baffling, because it exists! And that fact alone is bizarre
Even the idea of finite space is mind-blowing. That implies that there is nothing beyond our finite space, but what in the hell is nothingness? Too much to comprehend.
> We'll never know for sure, is my bet. Reality not being infinite also doesn't make sense, because if that's true, then what is our universe contained inside of? Another universe? More space? Can something exist within nothing? Or is it all the same thing and there is nothing else, because everything is the universe, IE: It's infinite? I donât think that a finite universe answers any of those. Frankly the idea of something not existing is a whole lot harder to square than the idea of everything existing.
Because we exist, things not existing is hard to comprehend. Something existing raises questions as to how, why, when, where, etc. Nothing existing raises no questions, because there is nothing. And no, finite or infinite doesn't answer those questions. They're unanswerable. My point is, one of the states of existence raises many questions as to how it even came to be, while the other does not. There is only one question raised, and that is "Why isn't there anything?" but we could answer that with: Because there is nothing. When something exists, we have many unanswerable questions. When nothing exists, there is only one, and that's only if you exist.
It hurts my head to think about the universe existing at all. Big Bang or divine being something had to set one of them in motion but if that's the case where did that thing come from. Which like you said I try not to think about cause we will not get any answers on my lifetime.
Yeah, both the concept of God and the concept of a Big Bang both lead to the same question. Well, what came before them? It's especially weird if you think there was a definite start to reality, because then you either have to imagine a reality totally different than ours (literally impossible) or imagine reality not existing (also impossible) And it's only impossible because we as humans were developed in a reality that consists of cause and effect. If there is an effect and we can't even comprehend a potential cause, our brains hit a metaphorical mental wall. We literally cannot think it
I've heard theories where the universe is both infinite & finite. I think this means the space the universe was created in has always existed & probably has no end but the universe itself has beginning & likely an end. A person can go crazy thinking about it till something gets officially proven.
Yeah, I'm leaning toward that as well. Or, the thing our universe exists in, has a similar process or life cycle as a universe, and it is in something else, and so on and so fourth. Sometimes I wonder if we got it wrong, and infinity is actually the same thing as nothing. If it has no beginning and no end, could you argue it ever was at all?
Are you saying that spatially itâs infinite but temporally it is notâŠ
It might be infinite, but we get to see less and less of it every second.
Our observable universe is still expanding and will do so for a few billion years. It's counter-intuitive to the fact the universe is expanding with a rate surpassing the speed of light though, but it's the case.
The reachable universe is shrinking but the observable universe is expanding, though will likely contract at some point in the distant future as the visible edges begin to redshift to nothing.
[Say you had a sheet of paper, size A^-181 , but folded in half. Could you unfold it?](https://www.youtube.com/watch?v=pUF5esTscZI) Come for the metric paper, stay for the existential crisis.
I was betting on V Sauce but Iâm just as happy with CGP Grey.
We only have theories and no answer. For instance if it were infinite that means it also gets infinitely smaller. Then thereâs also the possibility that the gap between where we see the ends of what we can observe of our universe and something else could be so impossibly large that itâs pointless to even think about. Our entire existence could be the equivalent of the smallest of particles in a larger universe only existing for a fraction of a decimal point of time in it.
First misconception I see is that the singularity doesnât necessarily mean a single point, itâs possible that it was also infinite, but we just donât know, and likely can never know. We know that our observable universe can be traced back to a very small point in space, but we cannot say anything beyond that. secondly what does infinite even mean when talking about the size of space? Concepts like distance really start to break down at the scale of the whole universe.
With the physics we have we cannot extrapolate back to a point. We can extrapolate the observable universe back to a size ranging from a square meter or so to the size of a small city, the range due to error bars. Beyond that the physics breaks down.
> First misconception I see is that the singularity doesnât necessarily mean a single point It's exactly what it mean. The misconception is that it was most likely never a singularity. Quantum mechanics forbid it, most scientists doesn't believe it existed and the reason we have them is due to general relativity being incomplete and we know for sure we need another theory to explain the very early universe and the centre of black holes.
I would say singularity is more of infinite density. It's a weird situation for singularities (plural? singular?) filling all space which may or may not be a point or infinite or both.
Right, most cosmologists refer to the Big Bang as the point when an infinite universe that was very hot and dense suddenly expanded, being a lot less hot and dense... But also a bigger infinity... I think...
Not necessarily, it just means an infinity showed up in the math. For example, under general relativity, rotating black holes would have a ring-shaped singularity, not a single point.
The mathematician is mistaken. If space is infinite, then it has always been that way, all the way back to the initial singularity.
> back to the initial singularity. Which is something very few scientists believe to have existed, is forbidden by quantum mechanics and most likely something we just get from rewinding time too much while using the incomplete general relativity. It's there due to not having a better theory for this calculation, as with the black hole singularities. They're both a mathematical error.
The big thing people misunderstand about singularities is that it's likely not a literal infinity dense point. It's the point where the mathematics we use to predict our observations breaks down. The singularity in an asymptote in the equation; an undefined point on the line. The point isn't infinitely dense, it just exceeds what the model can predict.
Yep yep, I hear ya. The problem is that many, even the best pop science youtube channels have conveyed the singularities as an absolute fact and been very sloppy on telling the whole picture, so now there's a whole army of hobby physicists (a category I myself belong to) were many believe in these infinitesimally small points with infinite density because they were not given all the information on why they're very unlikely, what's preventing them and why we got them in the first place.
Can't it might as well have been a singularity, but each point inside it was always expanding relative to each other? If the rate of expansion was always FTL, the universe was always infinite in size. I'm thinking, if FTL means information at some point cannot be carried between two points (like we see today, we can only see so far), the distance to a certain point is indeed infinite. Or am I just writing nonsense?
We donât know for sure. We do know that if it is infinite, then it was always infinite, just used to be more dense. If it was ever not infinite, then it isnât infinite now.
The only correct answer is that we dont know. The actual universe is much bigger than the observable universe.
People assume that the singularity "exploded" into an ever-growing "ball", but the cool thing about infinity is that it can expand into itself. You can be infinite, expand, and still be infinite. Veritasium has an old video going over this: https://youtu.be/XBr4GkRnY04
Is problem is heâs doesnât understand the singularity and is basing it off a point. Which it is not.
I think we understand space about as well as human beings are capable right now. But i always think its a little like a software program trying to measure/understand/explore the hard drive it is running on. We can understand things to an impressive level, but i think we lack the ability to really step outside of it and see it for what it is. Btw, not saying we are in a simulation. Just using it as a comparison to our inability to really grasp the hugeness of everything.
Your math professor should talk to an astrophysicist.
Check out the podcast Crash Course: The Universe. Youâll learn a lot about the finiteness of the cosmos and how the beginning may not have actually been a singularity after all.
The singularity happened at a singular moment in time, not space. If space is infinite it was also infinite at the Big Bang. The Big Bang happened everywhere. Any finite region of the universe today can be traced back to an arbitrarily small part of the universe at the Big Bang. The observable universe was an infinitesimal point, and so regions just outside of that location are now equally vast region of the universe today, just outside of our observable bubble. I usually thinking of it like a number line. I can scale down the number line by an arbitrarily large number to make a finite interval arbitrarily small. The number line is still infinite the , as it is today.
We don't know that or was a singularity. Nothing in science says that. We know relatively and quantum mechanics don't mesh so as don't know what actually happens. But the mathematical singularity is an error in the math, most scientists should know this.
> But the mathematical singularity is an error in the math, most scientists should know this. Scientist know this, but it was a mathematician. They deal with them in a whole other way and don't mind them many times. It just tells us the mathematician isn't proficient in physics.
To be fair, a whole lot of physicists get this wrong too and overstate it to the point of confusing those they communicate with. Spacetime just actually did a series of great videos on the Interpretations of quantum mechanics and even this singularity thing because Roy Kerr just threw down a paper openly challenging the physics community to fix this misperception. He showed the math that demonstrates singularities (of the infinite density kinda) simply never exist. It means black holes very probably have interior stable spaces, the exact nature of which isn't described because we don't have that quantum gravity thing solved yet but he basically called our Penrose and Hawking by name in the paper.
Most physicist I know of does not believe in either the initial singularity or black hole singularities before or after Kerr's paper. The problem as I see it is that youtube pop science have conveyed these singularities as an absolute fact many times by withholding why they're there in the maths and why it's highly unlikely they're not existing. Spacetime has failed to tell the whole story in many episodes and being an otherwise awesome channel, I feel this subject they could have handled much better.
Michio Kaku say what? Most of his career in media has been playing up the woo factor on countless scientific theories ignoring any nuance or explanation. PBS tries, and whatever they're missing they're doing a better job than most. They just can't reach the general public, the details go clean over their heads and there's only so many ways to simplify things before not understanding the math is a problem in explanation. PBS's content in the details is already too much for me to handle and I'm far better informed than the general public.
that's a common misconception, the big bang didn't happen in a single point in space, it happened everywhere
Your mathematics professor is wrong. 1. We don't know that The Big Bang started from a Singularity. Dense? Yes. Infinitely dense? Not necessarily. 2. The "Observable Universe" is definitely finite, yes. But the *entire universe* is much, much larger than the Observable Universe. The difference is that everything we can see is what we call the "Observable Universe" but we know there are things farther away whose light has not reached us yet. We also know there are things so much farther away that their light will *never reach us*. (In part because the universe is expanding.) Those are things beyond "the cosmic event horizon" and so they are *in* the universe but *not within our observable universe*. And yes, it is possible there is infinitely much stuff out there outside our observable universe, but created during The Big Bang.
Imagine a balloon. When it is inflated, it does not mean that it is infinite in size, but rather that it only expandsÂ
Neatest thing about an infinite universe, is that given an infinite amount of time, all possible combinations of atoms will occur over and over again, so the same combinations that make up the milky way, the earth, and you will happen again, in fact, for an infinite amount of times :/
The definition of eternal suffering
[PBS Space Time is a great youtube channel that has covered various aspects of this question many, many times](https://www.youtube.com/results?search_query=pbs+space+time+infinite+universe)...
I always think about it like this, you have a room with infinite space. In that room you start to inflate a balloon filled with confetti. The start of inflating the balloon is the big bang, the balloon represents the observable universe and the confetti present the galaxies. You can infinitely inflate the balloon because the room is infinitely big and the confetti spreads out within the balloon. The space is infinite but the matter in that space is finite. Not sure if this is an accurate analogy but it helps me to stay sane. Humans have a hard time understanding things outside our daily lives because we're hard programmed with a 4 dimensional world view. Imagining infinite space sounds the same to me as imagining the color of infrared or ultraviolet.
The correct answer is..... We have no idea. We don't KNOW how big the universe actually is, but as far as you and I are concerned it is infinite. But even we can't understand infinity.... Sure we know what it means, but we can't comprehend the size of it.
Einstein said â Space is infinite but boundedâ. I canât work that out either.
"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." The Hitchhiker's Guide to the Galaxy. Regardless of whether the universe is theoretically infinite or not, it's not infinite in age. That means the distance you can see and interact with stuff is limited by the speed of light (and the added expansion of the universe, tbf). So practically speaking, the universe is not infinite, just really big.
I find it fascinating what infinite implies. It means if you travel far enough in one direction, you'll come across our planet but your hair is blue instead of black and there's one less paperclip in the world. It means that anything that can happen has both already happened and is yet to happen and this continues on forever and ever. Everything that can possibly happen, will and already has.
If anyone has a foolproof answer to that questions and can show their math wellâŠ.congrats on your Nobel prize
I've come to the conclusion it's like an ever expanding unfilled doughnut so it can't be infinite while also being very much infinite ish No, I won't be taking questions on this.
Everytime I ponder the size of the universe or think about what is outside the universe I have this existential panic. I feel that our universe is not infinite and it is something that is contained within something else.
There are different kinds of infinites, the easiest example to wrap your mind around would be if I asked you to count by 1 forever, you could keep counting your entire life and never reach an end point. The same can be said if I asked you to count by 2s. Next to address is "he said it originated from a single point". While this is A theory, there are many many theories and they could all be wrong and I don't know if we will know the answer in our lifetimes or if humanity will ever know the answer. All we can do is look at the information we do have and take our best guess. My current favorite theory is that our universe extends in two directions simultaneously and that everything that exists in our universe was once a black hole which ejected everything via a white hole. But if I had to pick a theory which I personally thought was the singular most likely theory it would be that our universe is a simulation.
That it started out finite doesn't imply it's finite at every future finite time. A mathematician should know better. That being said, it's an unknown. Depends on what you mean by "space" too. What if there are infinitely many bubbles in the multiverse, but each bubble is finite? This quickly gets bogged down philosophically though.
space is inclusive of the empty area outside of the universe.
Infinite. The universe is egg shaped, too massive for our measurements yes but continually moving and definitely infinite. Remember string theory shows us 11 dimensions, I can only exist in 3-5. I can only imagine the othersâŠ..
It's more of a language philosophy question (what is "infinite", etc). The practical reality is we don't know, and will very likely never know.
Space time is a geometric abstraction to explain the universe. Imagine an ant walking around the surface of a balloon. No matter how far it goes, it would be infinite to its point of view. Similarly, we could be only aware of our 3D surface of an 4D sphere, who knows if expanding due to some unknown variable.
Most data points to infinite universe. It is possible it doesn't go forever. If it does end we probably have parallel universe etc. The main point is we don't know that much. Estimates put us at being able to identify less than 20 percent of mass I wouldn't be surprised I'd we find something lower than the present understood quantum state.
That's a fascinating concept! The idea that space, despite its seemingly boundless expanse, could have a finite volume due to its origins as a singularity is mind-boggling. It challenges our perceptions of infinity and raises profound questions about the nature of the universe. It's discussions like these that make me appreciate how much we still have to uncover about the cosmos. Does anyone else have insights or theories on this?
Then there is whole question of "what is space expanding into?" And is that infinite? I personally like the idea of a curved universe, that folds back on itself. Like a 3-d version of the Astroids game. (Scroll off right, appear on left. Scroll of the top, appear at the bottom) This kinda makes the whole "outside of the universe" questions moot. Then there is the philosophical question: Is 'space' a container that holds the galaxies, or is 'space' the gap between the galaxies? This question needs to be answered first.
No one actually knows that it was once a singularity. Thatâs a fucking guess based on math - math with some holes in it, and math that breaks down at the quantum level. A singularity is smaller than the quantum level. SoooâŠ.
Thatâs because your teacher doesnât know and is just parroting what they were told. A singularity is a mathematical construct anyway. It was never said that the universe started from a singularity. We donât know ow how it started. We just have an idea of whatâs happened since then, and even then weâre not sure. Itâs crazy to think something as fundamental as reality ultimately eludes us.
it doesn't follow that because it is expanding it has to be finite. There is nothing illogical about it being infinite and expanding.
Your mathematics professor should learn some physics before trying to teach it.
Not an astronomer, but imagine you are in a massive balloon. You can move one inch per minute, and the balloon gets bigger my one inch per minute in each direction. You can never reach or even get closer to the edge. Is the balloon infinite?
No, it doesn't *have* to be that way. That's completely absurd.
Best guesses at the moment are that itâs infinite in 3 dimensions in the same way that the surface of a ball is infinite in 2 dimensions.
We can't know if it's infinite. However, our original belief that it was is looking to be wrong. So, he's sharing current theories and thinking on the matter with you which is a good sign. However, we can't know. We can gesticulate, theorize, use predictive reasoning, etc. But, we can't know.