Do you think the Universe explodes and contracts in a cycle, disrupting time and space while at it?
Or do you think it's like a ripple in a Multiverse puddle, expanding until it disappears, and maybe faintly interacting with other ripples, beyond our power to observe?

I've never understood why people have this idea that the universe is like a bubble with an increasing volume. I've always just thought that the two farthest objects from each other were getting further away from each other, I don't see how the space they can travel through can be limited to certain boundaries.

A while ago I saw a NOVA episode about how, in such-in-such trillion years, the matter in the universe may tear apart because of space expanding. I would like to know why matter cannot just occupy less of the expanding space...it implies that matter is aligned to a grid (space) which is expanding, and that the interactions between matter are not affected by this expansion - which makes no sense.

By the way what character did you use in the topic title? Some sizeless unicode control character?

Here's something I don't understand about the beginning...

There is a singularity, of sorts. Nothing exists, really, but at some point, it becomes unstable and decides to explode and the universe is formed.

No cause? No explanation?

I think there is a lot more we don't know and everything we're hearing is speculation.

@L B,
You're right, although there are no two farthest objects AFAIK. It's not expanding from any central point but from all points simultaneously. If that's confusing, imagine doing this (or actually do it): get an uninflated balloon and draw some points on it in permanent marker. As you inflate the balloon you should notice all the points getting farther away from each other, rather than away from the centre of the balloon. Also, the universe isn't expanding into anything (there is, by definition, nothing outside of the universe for it to expand into), instead, all the distances are increasing. Imagine a distance of 1 metre. In an imaginary universe where the rate of expansion is 100% per year (that is, it doubles in size every ~31,536,000 seconds), after one year that distance would be two metres. However, if you measured it it would still be one metre, and you could never perceive it to be anything but one metre, because one metre has doubled in size, meaning every ruler in the universe has also doubled in size. If, however, you could take a ruler from another universe (one that isn't expanding) where 1 metre is still 1 metre, I think you would measure the distance to be two metres.

---

Here's a thought. Imagine two galaxies with a distance of d = 100 ly in between them. Assuming the rate of universal expansion is constant such that v = 1 ly per year. Let's say that in each galaxy is an immensely powerful and highly developed civilisation which collaborate on a system of faster-than-light communication via some kind of cable which spans the distance between the two galaxies (don't ask how they decided to collaborate if they didn't have the communication system already, or how they apparently became so intelligent as to break physical laws). In 100 years the distance will have double to 200 ly. Assuming the cable is flexible enough and long enough to take into account the movement of the planets and galaxies but not the expansion of the universe, does it still span the full distance, or does it break? Why?

I think it stays as it is because of the explanation I gave above.

---

One more. The universe, by definition, encompasses all time and space. This means that to speak of a "before the universe" is meaningless, since before the universe there was nothing, not even time itself. Therefore, isn't is meaningless to speak of the creation of the universe, or its having come into being? Even though the age of the universe is estimated at 13.7 billion years, isn't it possible to say that it's infinitely old, since it has existed for as long as time has? Doesn't that mean that the universe has always existed, and therefore that it was never created? Doesn't that make the question of where the universe came from moot, since the universe didn't come from anything or anywhere - it has simply always been?

That's something that's been bugging me for a while since, unless it can be shown to be flawed, it would negate the need for a creator, intelligent designer or source of creation. It wouldn't disprove a creator, but it would make the existence of one unnecessary. I hope it's not so but I'm guessing there's some kind of flaw there that I'm unable to see, or else that what I said doesn't make sense or makes sense but simply doesn't change anything.

Yeah, I'm understanding all of that, but what I am not understanding is why NOVA explains that all matter in the universe would tear apart eventually. There are so many flaws with this idea using your logic, which I agree with by the way.

However, if you measured it it would still be one metre, and you could never perceive it to be anything but one metre, because one metre has doubled in size, meaning every ruler in the universe has also doubled in size.

This is not actually true. Gravity compresses space-time, so gravitationally-bound objects like galaxies aren't as affected by expansion as intergalactic space. The speed of light doesn't increase, either, so there's one consistent ruler for you to use.
A constant speed of light in an expanding universe causes a Big Rip. It's when space expands so much that even subatomic particles take too long to communicate with each other.

The universe, by definition, encompasses all time and space.

Well, more like all space-time that is topologically connected. There could in principle be things that exist outside the universe, but we can't know about them.

This means that to speak of a "before the universe" is meaningless

Only if you speak about it from within the universe. Just like how sqrt(-1) only makes sense from outside the real line.

Even though the age of the universe is estimated at 13.7 billion years, isn't it possible to say that it's infinitely old, since it has existed for as long as time has?

Imagine the universe as a set of toy bricks and the Big Bang as the state of all the bricks being inside a bucket. In this state, it's not possible to know when the bricks themselves were made, in what configuration they were before being put in the bucket, or how long they've been in the bucket. If all you know is that the bricks were inside the bucket, you can only deduce (ignoring Last Thursdayism) that the bricks are at least as old as now-bucket_time. They could be 2*(now-bucket_time) old or infinitely old, but neither are knowable.

Although it's worth mentioning that infinite time fits inside finite time. That is, ignoring physical limitations, we could create within our universe another universe whose inhabitants believe had existed forever.

helios wrote:

This is not actually true. Gravity compresses space-time, so gravitationally-bound objects like galaxies aren't as affected by expansion as intergalactic space. The speed of light doesn't increase, either, so there's one consistent ruler for you to use. A constant speed of light in an expanding universe causes a Big Rip. It's when space expands so much that even subatomic particles take too long to communicate with each other.

This makes sense - thanks!

Although it's worth mentioning that infinite time fits inside finite time. That is, ignoring physical limitations, we could create within our universe another universe whose inhabitants believe had existed forever.

Also known as "WoW syndrome".

roberts wrote:
There is a singularity, of sorts. Nothing exists, really, but at some point, it becomes unstable and decides to explode and the universe is formed.

Singularity, AIUI, is a phase of the Universe when it is collapsed onto itself, in an infinitely small point of infinitely high density. I don't think you could call that "stable".

It also makes no sense asking what was before that point, or what was around that point, because space and time aren't defined. At least not in the way they are now, for inhabitants of the "expanded" version of the Universe.

L B wrote:
I've never understood why people have this idea that the universe is like a bubble with an increasing volume.

Probably because infinity doesn't apply to the real world? The closest thing to it is a cycle.
Therefore, regarding space, I simply can't think of it as a void stretched out to infinity. It too must be made of some particle, I think.

L B wrote:
A while ago I saw a NOVA episode about how, in such-in-such trillion years, the matter in the universe may tear apart because of space expanding.

A repulsive anti-gravity force, maybe?

helios wrote:
Although it's worth mentioning that infinite time fits inside finite time. That is, ignoring physical limitations, we could create within our universe another universe whose inhabitants believe had existed forever.

Philosophically indeed a lot of things can be accomplished.

You are definitely thinking a lot about this subject lol most people have just come to terms with the universe expanding, but i suppose that could always be a possibility

@ Catfish: In regards to the part about infinity and 'the void' being made out of some 'particle', say goodbye to any hopes of getting much done today: http://en.wikipedia.org/wiki/String_Theory

Singularity, AIUI, is a phase of the Universe when it is collapsed onto itself, in an infinitely small point of infinitely high density. I don't think you could call that "stable".

So does that increase the probability of the universe being cyclic? Or does that mean we have universes popping all over the void?

@ roberts: That depends on what you think a Black Hole really is.

I don't even really know, truthfully. I know they used to be supermassive stars that collapsed on themselves in their death throes. The resulting concentration of mass pulls spacetime in around it. It becomes the classical point mass of infinite mass and density with the caveat that our understanding of physics is out the window at the center. But there was something in existence before that point, so I start to lose understanding of how a point mass creates the universe before anything existed before it.

Personally, I can't equate a black hole to a universe.
Computergeek01, could you tell what makes you suggest that it could be?

roberts wrote:
But there was something in existence before that point, so I start to lose understanding of how a point mass creates the universe before anything existed before it.

The rest of your post is also my view and understanding so far, but this quoted part confuses me.
Where's the "before" in a cycle? (If a cycle is what it truly is, of course.) Or did I misunderstand you?

Disclaimer: I'm unfamiliar with the String Theory, thanks for the wiki link, which I'll read later.

Catfish, the before is what created that cycle. For instance, everything has a cause and effect, except for whatever started the universe. For instance, if I kick a bottle, the bottle flies but what happened to cause me to kick the bottle? Then, what happened to cause that cause? And so on. You can go all the way back to the beginning of the universe.

It's such a large question that some consider whatever started the chain of cause and effect to be "God".

The problem I have with string theory (other than the fact that I don't really understand it) is that it doesn't seem like it's really solving the problem of existence, but delaying it - if quarks are made of strings, what are strings made of? And what is that made of? Also, could quarks, leptons and bosons really be called "fundamental" particles if they had constituent parts?

Then again, what else could they be made of?

@helios,
Thanks for that explanation, that cleared a few things up.

I've never understood why people have this idea that the universe is like a bubble with an increasing volume.

Because they would be wrong. Just because planets and stars are spherical, does not mean the Universe must be spherical. The Universe is actually flat: http://map.gsfc.nasa.gov/universe/uni_shape.html

It too must be made of some particle, I think.

Dark Energy.

A while ago I saw a NOVA episode about how, in such-in-such trillion years, the matter in the universe may tear apart because of space expanding.

Keyword: may.

The Big Rip (http://en.wikipedia.org/wiki/Big_Rip) is just a hypothesis, just like The Big Crunch (http://en.wikipedia.org/wiki/Big_Crunch). The most accepted model at the moment is The Big Freeze, where the Universe continues to expand for infinite time but due to the Second Law of Thermodynamics the temperature of the Universe would be Absolute Zero resulting in heat death.

This means that to speak of a "before the universe" is meaningless, since before the universe there was nothing, not even time itself. Therefore, isn't is meaningless to speak of the creation of the universe, or its having come into being? Even though the age of the universe is estimated at 13.7 billion years, isn't it possible to say that it's infinitely old, since it has existed for as long as time has? Doesn't that mean that the universe has always existed, and therefore that it was never created? Doesn't that make the question of where the universe came from moot, since the universe didn't come from anything or anywhere - it has simply always been?

We don't if there was "nothing" before the Universe. Anything that happened before the Big Bang could not have affected anything that happened after. All we know is that the "battle" between equal amounts of matter and anti-matter in the Big Bang Singularity (a point of zero volume, but extremely high mass: hence infinite density) caused them to annihilate together and caused The Big Bang and the Universe as we know it. We don't even have an accurate model of the early Universe before one unit of Planck Time, and we may never know. To understand the pre-Planck Time era we would need a "Theory of Quantum Gravity" because everything was so small that General Relativity just simply doesn't apply and Quantum Mechanical effects are most important. To this date, no such theory exists, so we cannot properly determine if the Universe actually had a beginning or not. The biggest obstacle of this, I would summise, is that Quantum Theory relies heavily on probability.

Did you know that, using an old analog television, you can see some remnants of the Big Bang by tuning the it between 2 channels? About 1% of the snow and noise comes from the Big Bang itself. It's possible to "eaves drop" on the beginning of the Universe itself.

"We need a Theory of Everything, which is still just beyond our grasp, perhaps the ultimate triumph of science." -- Stephen Hawking

"The poetry of the expanding Universe and the complexity of life; we are not normally equipped to understand it. Science gives it. Science is opening your eyes to the wonderfulness of what's there, to the poetry of the expanding Universe." -- Richard Dawkins

"Science is more than a body of knowledge. It's a way of thinking. A way of skeptically interrogating the Universe. If we are not able to ask skeptical questions, to be skeptical of those in authority, then we are up for grabs." -- Carl Sagan

darkestfright wrote:

We don't if there was "nothing" before the Universe. Anything that happened before the Big Bang could not have affected anything that happened after. All we know is that the "battle" between equal amounts of matter and anti-matter in the Big Bang Singularity (a point of zero volume, but extremely high mass: hence infinite density) caused them to annihilate together and caused The Big Bang and the Universe as we know it. We don't even have an accurate model of the early Universe before one unit of Planck Time, and we may never know. To understand the pre-Planck Time era we would need a "Theory of Quantum Gravity" because everything was so small that General Relativity just simply doesn't apply and Quantum Mechanical effects are most important. To this date, no such theory exists, so we cannot properly determine if the Universe actually had a beginning or not. The biggest obstacle of this, I would summise, is that Quantum Theory relies heavily on probability.

That makes sense. So I guess I'm not necessarily wrong, but I am missing information. That's kind of what I expected to happen.

darkestfright wrote:
Did you know that, using an old analog television, you can see some remnants of the Big Bang by tuning the it between 2 channels? About 1% of the snow and noise comes from the Big Bang itself. It's possible to "eaves drop" on the beginning of the Universe itself.

Isn't that the Cosmic Microwave Background? It causes the static on radios and such as well, I think.

That makes sense. So I guess I'm not necessarily wrong, but I am missing information. That's kind of what I expected to happen.

That's the beauty of science really. It teaches us to never be satisfied with an answer, but to always push to learn even more.

Isn't that the Cosmic Microwave Background? It causes the static on radios and such as well, I think.

Exactly that.