I really would like to know
what are the most accepted theories regarding the size and shape of the universe?
Whoever understand of physics and care to explain please do.
Whoever understand of physics and care to explain please do.
Is the universe infinite?
- Thread starter FredLC
- Start date
Some decades ago their was an argument raging as to..
whether the Universe was a Steady State model
or Expanding..(the Big Bang theory etc).
Astro physics isn't my strong point. But a guy by the Name of George Smoot in the last few years mapped the temperature variations of what was 'The Big Bang'. So the Big Bang theory has pretty much be 'proved' as much as any theory can be.
The next problem is..The Universe is expanding but in what way?
1. Expanding to infinitum - in which case we could possibly 'see' the heat death of the universe? In X trillions of years..nobody really knows.
2. Will it expand to some predefined limit then contract and collapse in on itself only to initiate another big bang?
All that is known is the Universe is expanding, but we can't see past what is beyond the expanding universe if anything.
As for the size of the universe? I don't think anyone would dare estimate. The error margin alone even if it was 0.001% would make for a huge amount of missing mass/volume in the result.
Nobody actually knows for sure and probably wont know for sure.
whether the Universe was a Steady State model
or Expanding..(the Big Bang theory etc).
Astro physics isn't my strong point. But a guy by the Name of George Smoot in the last few years mapped the temperature variations of what was 'The Big Bang'. So the Big Bang theory has pretty much be 'proved' as much as any theory can be.
The next problem is..The Universe is expanding but in what way?
1. Expanding to infinitum - in which case we could possibly 'see' the heat death of the universe? In X trillions of years..nobody really knows.
2. Will it expand to some predefined limit then contract and collapse in on itself only to initiate another big bang?
All that is known is the Universe is expanding, but we can't see past what is beyond the expanding universe if anything.
As for the size of the universe? I don't think anyone would dare estimate. The error margin alone even if it was 0.001% would make for a huge amount of missing mass/volume in the result.
Nobody actually knows for sure and probably wont know for sure.
joespaniel
Unescorted Settler
Asking me about physics would be like asking a cocker spaniel what time it is, but I recently read about astronomers now saying the universe is MUCH bigger than ever previously thought.It must be pretty god-danged big!
In high-school (circa 1980s) they proposed it was cylindrically shaped, and "folded" back in upon itself after a few bazillion miles or so.
This ofcourse was sheer rubbish.
Truth is, no one has a telescope big enough yet to find out. The polar ice "telescope" shows promise, in theory, of being able to see much farther than anything else existing today.
That in and of itself is another can of worms.
You call, I come. 
Ever heard of the big bang?
In the beginning there was one huge bulk of pure energy which spread out with the speed of light and when it was "cold" enough (let's say only a few million degrees Celsius) mass was able to form.
This is the beginning that almost every big scientist agrees about. The trouble is: what's the current situation? The universe is believed to exist for about 10 billion years. If the universe still expands with it's original speed it should have a size of about...
...400E+24 cubic meter (400.000.000.000.000.000.000.000.000 cubic meter).
But energy simply spreads. Mass however attracts itself. This attraction causes the Earth the turn around the sun as that thing is so heavy. So there are too possibilities: the universe keeps it's size at some time (either in the past or in the future), or...the universe will collapse. But don't worry. It won't happen tomorrow. 
Either way, the universe will not be bigger than 400E+24 cubic meter.
Ever heard of the big bang?
In the beginning there was one huge bulk of pure energy which spread out with the speed of light and when it was "cold" enough (let's say only a few million degrees Celsius) mass was able to form.This is the beginning that almost every big scientist agrees about. The trouble is: what's the current situation? The universe is believed to exist for about 10 billion years. If the universe still expands with it's original speed it should have a size of about...
...400E+24 cubic meter (400.000.000.000.000.000.000.000.000 cubic meter).But energy simply spreads. Mass however attracts itself. This attraction causes the Earth the turn around the sun as that thing is so heavy. So there are too possibilities: the universe keeps it's size at some time (either in the past or in the future), or...the universe will collapse.
But don't worry. It won't happen tomorrow. Either way, the universe will not be bigger than 400E+24 cubic meter.
I just did.
Is the universe infinite? I'll answer that literally. I think that there is no smallest thing (particle), and no largest thing (the universe). I also think that there is no limit to velocity or mass. Or time!
We have some modernday shamans here who keep expanding their four corners of the Earth, and mystifying it. They see the local as the all, for example in saying that the universe is expanding when in fact it's just a (relatively) tiny bit of space in our neighbourhood that appears to be expanding.
The most accepted theory is that the universe was created, is finite, and will have an end.
Good luck in your search.
We have some modernday shamans here who keep expanding their four corners of the Earth, and mystifying it. They see the local as the all, for example in saying that the universe is expanding when in fact it's just a (relatively) tiny bit of space in our neighbourhood that appears to be expanding.
The most accepted theory is that the universe was created, is finite, and will have an end.
Good luck in your search.
MCdread
Couldn't she get drowned?
- Joined
- Jun 21, 2001
- Messages
- 5,348
The present standard theory regarding your question states the following:
The Universe is finite, but one cannot reach its borders, or if you prefer a more bombastic sentence, it is finite but has no ending. The Universe is a quadri-dimentional (at least) space, and we move in a 3-D space. A geometrical aproach is to consider a sphere, that is expanding. In a 3-D model, what is hapening is that the radius of this sphere is increasing, which means that the surface area is also becoming bigger. This is exactly what happens to a balloon that you are filling with air.
Now, expand this into 4 dimensions. You get a 3-D surface and a 4-D sphere. The analogous 4-D radius is called Universe Radius, and the surface is precisely our space, it is where we move, in the same way that we move in the surface of the earth. In the earth, if you start moving in one direction, you will not come to an end. At the best you'll get to your starting point, and completed a circumference around the globe. So, if you start a space journey, moving in one direction of space, you would only return to where you started. But I strongly discourage you to embark on such a voyage; the most distant objects we know are about 14 bilion light-years away, and matter can only travel at a velocity smaller than 300000 Km/s.
What you could do, at least theoretically, is to use certain shortcuts. Matter distorts space, and the more massive the object is, the bigger the distortion. There's nothing with higher density than a black hole, and in theory, the deforming of space can go to the point of connecting to far away regions. So one could speculate that you could use this "high speed tunnel" to emerge in a different place. However, that is also something you mustn't try at home.
And there's allways the question of the Schwarzchild radius, which is a critical horizont. In our referential, an object would never reach that critical point, but in the particle referential it would disappear into the black hole. Pretty confusing, huh!
Anyway, don't worship these words. A physicist is just a seeker of models, and I don't seek models in Cosmology, although I'll have an Astrophysics exam this week. This was the reason why I came to Physics, when I was a naive kid, and even if I eventually didn't follow this field of Physics, I decided to keep a course on this to my last year, as a sort of homage. Well, forget this paragraph, I've already caused you enough bore.
The Universe is finite, but one cannot reach its borders, or if you prefer a more bombastic sentence, it is finite but has no ending. The Universe is a quadri-dimentional (at least) space, and we move in a 3-D space. A geometrical aproach is to consider a sphere, that is expanding. In a 3-D model, what is hapening is that the radius of this sphere is increasing, which means that the surface area is also becoming bigger. This is exactly what happens to a balloon that you are filling with air.
Now, expand this into 4 dimensions. You get a 3-D surface and a 4-D sphere. The analogous 4-D radius is called Universe Radius, and the surface is precisely our space, it is where we move, in the same way that we move in the surface of the earth. In the earth, if you start moving in one direction, you will not come to an end. At the best you'll get to your starting point, and completed a circumference around the globe. So, if you start a space journey, moving in one direction of space, you would only return to where you started. But I strongly discourage you to embark on such a voyage; the most distant objects we know are about 14 bilion light-years away, and matter can only travel at a velocity smaller than 300000 Km/s.
What you could do, at least theoretically, is to use certain shortcuts. Matter distorts space, and the more massive the object is, the bigger the distortion. There's nothing with higher density than a black hole, and in theory, the deforming of space can go to the point of connecting to far away regions. So one could speculate that you could use this "high speed tunnel" to emerge in a different place. However, that is also something you mustn't try at home.
And there's allways the question of the Schwarzchild radius, which is a critical horizont. In our referential, an object would never reach that critical point, but in the particle referential it would disappear into the black hole. Pretty confusing, huh!
Anyway, don't worship these words. A physicist is just a seeker of models, and I don't seek models in Cosmology, although I'll have an Astrophysics exam this week. This was the reason why I came to Physics, when I was a naive kid, and even if I eventually didn't follow this field of Physics, I decided to keep a course on this to my last year, as a sort of homage. Well, forget this paragraph, I've already caused you enough bore.
Switch625
I don't care.
The Ekpyrotic Model of the universe is an emerging challenger to the "Big Bang" theory. Fact is, I just learned about this model earlier today from another thread on this very site. Anyway, I can't claim to truly understand everything being put forth by this new theory, so you'll have to follow the link and try to figure it out for yourself. From what I do catch, in this model there was no initial singularity for the universe, our universe was created by the collision of two 3D "membranes" that exist within a 5D space. I'm not going to try to explain it any further than that, I'm still digesting it myself. Follow the link and take a look.
Fascinating idea, though. If this theory is correct, there was no universe shattering kaboom at the beginning of time... more like the crash of two cymbals together kicking everything into motion.
[EDIT]How is this topical? Well, it basically says that all we thought we undestood about the universe just got a big kick in the pants. Answers are farther away than we thought.[/EDIT]
Fascinating idea, though. If this theory is correct, there was no universe shattering kaboom at the beginning of time... more like the crash of two cymbals together kicking everything into motion.
[EDIT]How is this topical? Well, it basically says that all we thought we undestood about the universe just got a big kick in the pants. Answers are farther away than we thought.[/EDIT]
Except that in recent years experiments have proved that the universe's expansion (or the visible part of it) is accelerating. It was assumed that it was decelerating. So I guess that option 2 is not going to happen.
Which would mean that you cannot rely on this figure being the upper limit to the size of the universe.
There is also a theory out there that suggests that the universe is a lot smaller than the visible universe! (Some kind of optical effect)
I'd heard about the Ekpyrotic model a couple of weeks ago, but thanks for the link. Its interesting, I like the idea of other universes not being nessacary (and I know that basing an opinion of a theory on asthetics isn't good practice), although there could be other universes on the fifth dimension, but there are other questions like what if another membrane hits ours. It might also provide a solution to why the universe's expansion is accelerating because it allows for something outside of our universe which can affect it, according to the link gravity can work outside of our universe.
However I don't think it is a challenger to the Big Bang theory, it seems to build on top of it, although it may challenge the inflationary theory.
But in answer to the origianl question, I don't think anyone will have a decent idea about the size and shape of the universe within my lifetime
Wait a moment, I'll just check...
No!
Lucky
Game- and Quizmaster
- Joined
- Nov 6, 2001
- Messages
- 2,304
The universe is finite. That is the basic fact everyone agrees on.
But the real question whether the lifetime is infinite, i.e. if the universe is somewhen collapsing again.
The currently accepted idea is that the universe is constantly expanding, even accelerating right now. The main forces that we already have defined for this effect are gravitation and the original expansion velocity. Gravitation is decreasing as the universe is expanding, so the contracting force is decreasing, too. The question is whether the universe has enough mass to stop the expansion at some point. Currently it has not. But there is the so called amount of "Dark Mass", matter that does not reflect radiation for us to register and therefore "see" this matter. But even with an estimate, the total mass would not be enough. That lead to the popular agreement that the universe will always expand.
But recently, in the last few years, new discoveries have underlined the theorie of constant expansion. The overall expansion rate is even increasing at the moment. Scientist have christened the force behind this "Dark Energy", because they have also not been able to prove this force.
But nonetheless, the universe is expanding and accellerating at it even.
All in all, there will not be a factual answer to this anywhere in the near future, since we still know not nearly enough to make a solid theory about it.
So everyone can still more or less dream about, or base his own theory on the little facts known today.
But the real question whether the lifetime is infinite, i.e. if the universe is somewhen collapsing again.
The currently accepted idea is that the universe is constantly expanding, even accelerating right now. The main forces that we already have defined for this effect are gravitation and the original expansion velocity. Gravitation is decreasing as the universe is expanding, so the contracting force is decreasing, too. The question is whether the universe has enough mass to stop the expansion at some point. Currently it has not. But there is the so called amount of "Dark Mass", matter that does not reflect radiation for us to register and therefore "see" this matter. But even with an estimate, the total mass would not be enough. That lead to the popular agreement that the universe will always expand.
But recently, in the last few years, new discoveries have underlined the theorie of constant expansion. The overall expansion rate is even increasing at the moment. Scientist have christened the force behind this "Dark Energy", because they have also not been able to prove this force.
But nonetheless, the universe is expanding and accellerating at it even.
All in all, there will not be a factual answer to this anywhere in the near future, since we still know not nearly enough to make a solid theory about it.
So everyone can still more or less dream about, or base his own theory on the little facts known today.
joespaniel
Unescorted Settler
Maybe there is somebody who knows more about the polar ice project?
I understand the idea is to create a gigantic "mirror" out of ice to study starlight very, very far out into space (much, much farther than any telescope can see).
They would be able to map out star-systems at increadible distance, however the maps would be obsolete as they are made.
The light takes so many millions of years to get here, the star that made it would have moved, or may already be gone.
I understand the idea is to create a gigantic "mirror" out of ice to study starlight very, very far out into space (much, much farther than any telescope can see).
They would be able to map out star-systems at increadible distance, however the maps would be obsolete as they are made.
The light takes so many millions of years to get here, the star that made it would have moved, or may already be gone.
If the universe is infinite, then our quest to prove it as finite will be infinite. There have always been intelligent people who can not accept infinity, and draw a boundary - the Edge of the Earth, the Indivisable Atom, the Apocalypse, the Creation, the Sound Barrier (nowadays the Speed of Light). All these boundaries were based on some pretty strong evidence, or lack of evidence against, in their time. Now, we have no evidence at all of there being more to the universe than what we can observe. If someday we can observe more, that doesn't disprove our belief that it is finite.
Kinda looks like religion vs. atheism, doesn't it?
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An ice mirror? Wow! That's a great idea. But how are we going to smooth it to the perfect concave shape? Does anyone know about this? If only there was some way to use the natural convexity of the Earth for a telescope.
There's a company making huge parabolic mirrors now, at very low cost. Their mirrors are made of (liquid) mercury, spun inside a roughly parabolic bowl. As long as it spins, centrifugal force holds the thin layer of reflective liquid against the insides of the bowl, forming a smooth surface, with the perfect curvature. The only drawback to these telescopes is that they must always point straight up! But many astronomers don't need any particular view for their purposes.
Kinda looks like religion vs. atheism, doesn't it?
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An ice mirror?
Wow! That's a great idea. But how are we going to smooth it to the perfect concave shape? Does anyone know about this? If only there was some way to use the natural convexity of the Earth for a telescope.There's a company making huge parabolic mirrors now, at very low cost. Their mirrors are made of (liquid) mercury, spun inside a roughly parabolic bowl. As long as it spins, centrifugal force holds the thin layer of reflective liquid against the insides of the bowl, forming a smooth surface, with the perfect curvature. The only drawback to these telescopes is that they must always point straight up! But many astronomers don't need any particular view for their purposes.
Archbob
Ancient CFC Guardian
No, only I am infinite.
Well, say it is finite, but suppose you set out from one extreme edge at the speed of light. I wonder if you would ever reach the other side? If the answer is no, then the universe is effectively infinite, though factually finite.
Since we believe the Big Bang hypothesis, that the universe expanded from a point in all directions, it is logically obvious that if the expansion was initially the speed of light or close to it, there has not been enough time in the lifetime of the universe for light to cross from one side of the universe to the other.
So I believe that even if the universe is finite we'll never ever get to the edge - which is good because we might fall off
Since we believe the Big Bang hypothesis, that the universe expanded from a point in all directions, it is logically obvious that if the expansion was initially the speed of light or close to it, there has not been enough time in the lifetime of the universe for light to cross from one side of the universe to the other.
So I believe that even if the universe is finite we'll never ever get to the edge - which is good because we might fall off
starlifter
Deity
- Joined
- Jun 17, 2001
- Messages
- 4,210
by Joespaniel:
You have just (knowingly or unknowingly) described on variant of a time machine... the humble telescope.
You have just (knowingly or unknowingly) described on variant of a time machine... the humble telescope
.Actually, yes. We have observed other universes indirectly, via their interaction with stellar bodies. Across an event horizon, the laws of this universe are not obliged to be followed. It gets kindof esoteric, but the same is true across the event horizon of the original creation of the universe, presuming the observations indicating a common origin point of the observable universe are borne out. One cannot track time back past this point, and across this horizon, in fact, one cannot even pose the question of what came before, as it is not connected to what came after. All in all, physics of the last 35 years has made remarkable strides to the account of creation in Genesis.
