Space, Infinite or Finite?

Off Topic
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Astrophysics is some freaky stuff. Einstein’s theories (which I believe more modern people like Stephen Hawking concur on) predict that the universe is doughnut shaped. So, whatever direction you go, if you travel long enough you will come back where you started. But the math for that is way beyond me, and I don’t even know if it is meant literally as a doughnut shape, or just that the properties of movement can best be methematically represented that way.

Also, here is another tricky thought. Just because the universe is expanding, does not prevent it from already being everywhere at the same time. How can both of these things be true? Because there are different degrees of infinity. For example, there are an infinite number of fractions between the number 0 and 1, right… You can just keep chopping the numbers in half infinitely getting smaller and smaller numbers. So, if there are an infinite number of fractions between 0 and 1, therefore there must be twice as many between 0 and 2. In both cases, the number is infinite. But in the second case there are twice as many as the first.

Think about this as it applies to space. Imagine that the universe extends infinitely. Well, what happens if everything moves further apart? It’s still infinite, and yet it has expanded. I believe this is what physicists typically mean when they say the universe is expanding.

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[quote]humanjhawkins wrote:
Astrophysics is some freaky stuff. Einstein’s theories (which I believe more modern people like Stephen Hawking concur on) predict that the universe is doughnut shaped. So, whatever direction you go, if you travel long enough you will come back where you started. But the math for that is way beyond me, and I don’t even know if it is meant literally as a doughnut shape, or just that the properties of movement can best be methematically represented that way.[/quote]

General relativity is really just the idea that space is a kind of smooth surface, and that gravitation somehow comes from the curvature of this surface. The Einstein field equations don’t predict a doughnut shaped universe. The doughnut thing is just a way of explaining how you can have a space with a different geometry to the usual flat plane.

[quote]humanjhawkins wrote:
Also, here is another tricky thought. Just because the universe is expanding, does not prevent it from already being everywhere at the same time. How can both of these things be true? Because there are different degrees of infinity. For example, there are an infinite number of fractions between the number 0 and 1, right… You can just keep chopping the numbers in half infinitely getting smaller and smaller numbers. So, if there are an infinite number of fractions between 0 and 1, therefore there must be twice as many between 0 and 2. In both cases, the number is infinite. But in the second case there are twice as many as the first.[/quote]

Well, there are actually exactly the same number of rational numbers in the interval [0,1] as there are in the interval [0,2].

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I think that space is finite.

It began when the Big Bang happened and has been expanding ever since.

Right now I think we’re at 156 billion light years across.

What’s beyond that? Good question.

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Not very knowledgeable on this whole subject, but very interested in it.

Semi-off-topic question- what does the speed at which you travel have to do with time?

For example, lets say that i am running. As i get faster and faster, time is still passing.

Theoretically, if i can run to light speed, how does it relat to time? Is it because i would be traveling at the speed of light, which would essentially mean i am “teleporting,” therefore time does not pass?

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[quote]TomRocco wrote:
Not very knowledgeable on this whole subject, but very interested in it.

Semi-off-topic question- what does the speed at which you travel have to do with time?[/quote]

Everything. Your speed relative to someone else will determine how differently you experience time.

[quote]For example, lets say that i am running. As i get faster and faster, time is still passing.

Theoretically, if i can run to light speed, how does it relat to time? Is it because i would be traveling at the speed of light, which would essentially mean i am “teleporting,” therefore time does not pass?[/quote]

Time would pass normally for you, to everyone else you would have moved instantaneously.

As you approach the speed of light time goes “slower” for you, meaning more time passes for everyone else. Astronauts often gain a few seconds on a trip if I remember correctly (basically travelling slighly forward through time).

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[quote]The other Rob wrote:
TomRocco wrote:
Not very knowledgeable on this whole subject, but very interested in it.

Semi-off-topic question- what does the speed at which you travel have to do with time?

Everything. Your speed relative to someone else will determine how differently you experience time.

For example, lets say that i am running. As i get faster and faster, time is still passing.

Theoretically, if i can run to light speed, how does it relat to time? Is it because i would be traveling at the speed of light, which would essentially mean i am “teleporting,” therefore time does not pass?

Time would pass normally for you, to everyone else you would have moved instantaneously.

As you approach the speed of light time goes “slower” for you, meaning more time passes for everyone else. Astronauts often gain a few seconds on a trip if I remember correctly (basically travelling slighly forward through time).[/quote]

The other rob is correct. As you approach the speed of light time slows. Once you reach the speed of light time “stops” for you, and passes at normal speed for everyone not going faster than normal. Say you have a twin how travels at normal speed, and you can travel the speed of light for 20 years. Once you stop, the twin has aged 20 years while you have not.

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[quote]ucallthatbass wrote:
Say you have a twin how travels at normal speed, and you can travel the speed of light for 20 years. Once you stop, the twin has aged 20 years while you have not.
[/quote]

That’s not really true. Unless you have a similar situation to the original formulation of the paradox (where one twin stays on Earth), then they will both see each other aging more slowly, because that’s how relativity works.

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I still dont understand how time slows when speed increases.

Basically (if i understand correctly), youre saying that if i travel at light speed for 20 years (on earth), and my friend just lives life normal for 20 years, he’ll get older, and i’ll be the same.

Isn’t 20 years 20 years, so my body will age/mature just as it would at regular speed?

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It works like this: one twin goes up in a rocket going at high-speed, and returns home. He will have aged less than the other twin who stayed on earth.

Special relativity basically says that a moving clock ticks more slowly than a clock at rest. But the reason for the twin paradox is hard to explain if you don’t have a background in physics.

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i dont know how complex the answer to this question is, but if it doesnt require much time to answer it i’d really appreciate it.

how would you prove that the moving clock slows time? How did scientists even come to that conclusion? we havent gotten to light speed yet (correct?)

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[quote]Rational Gaze wrote:
Bill Roberts wrote:
While that sounds reasonable enough to me, I don’t quite grasp what happens in the case of a contracting universe. Would matter traveling outwards, to its perception, at virtually the speed of light still nonetheless become closer and closer to the center of the universe? I suppose so but that is from supposition, not anything concrete. Performing general relativity computations is too hard for me.

It would be the matter within the universe that is contracting, not the universe itself somehow getting smaller. Similarly, with an expanding universe, it’s not expanding into anything, there’s just more space (an analogy would be the way a bread loaf rises in an oven, you aren’t getting more bread, it’s just stretching out). [/quote]

I’d be interested in a further reply on that from someone well versed in general relativity, in the sense of being able to perform the necessary computations to actually solve for the given questions (not that I am implying that you may not be: I don’t know.)

Not on the “not expanding into anything” – that is agreed.

But on the, apparently, “contracting out of remaining larger space” (paraphrase) that you seem to be advocating.

I don’t know for a fact but I had thought that the contraction was also of space, not merely the matter and radiation contained within it.

Question: why would photons radiating outward return back towards the center if space is not contracting?

Which raises further questions beyond my ability to establish regarding a universe that begins contracting or has been doing so for a while: To the perception (if it has perception) of matter moving outwards at exceedingly close to the speed of light, is it still moving “outwards” at the same speed, or does it perceive Hey dammit we’ve somehow gone into reverse?

My expectation is that the perception is that energy and momentum are conserved, and there is no loss of measurable velocity or change in direction.

If so then in what sense – to what observer – is the universe becoming smaller when it contracts? Assuming a universe that has a contracting phase.

Only to a transcendent observer? But we never allow those in physics. In the sense of physical constants?

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[quote]Bill Roberts wrote:
I’d be interested in a further reply on that from someone well versed in general relativity, in the sense of being able to perform the necessary computations to actually solve for the given questions (not that I am implying that you may not be: I don’t know.)
[/quote]

Oh, if it were so simple :smiley:

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[quote]BrownTrout wrote:
sufiandy wrote:
spyoptic wrote:
Have you guys seen the History Channel special on the theories of parallel universes??? Well, I didnt understand a fucking thing but it was interesting to watch!

It doesnt matter, theres a hundred billion stars in our galaxy and a hundred billion galaxies in the observable universe.

traveling at the speed of light - it would take 10000 years to reach the nearest start alpha centauri. we’re fucking stuck!

in 15,000 years a new ice age will come, so hopefully we’ve found a new world by then.

Actually it would only take 4.25 years

And BAM. Let there be time dilation![/quote]

lol @ physics joke. but, explain it…

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I’m pretty sure Poliquin knows the answer to this one.

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In fact, it is the 17th new science that he has discovered.

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[quote]Rational Gaze wrote:
humanjhawkins wrote:

Well, there are actually exactly the same number of rational numbers in the interval [0,1] as there are in the interval [0,2].[/quote]

The fun thing was a showing that (0,1) open and [0,1] closed can have a bijection.

I remember from Proof class Aleph NULL. Infinite yet countable. I described that in my honors Pre-calc class for them. They were “skeptical”

I think the true question is; is the “empty” space really empty or is it simply that there are places our understanding of physics does not work. So as a few others seem to have alluded to is there an event horizon that we would not be able to pass? Prior to the big bang during the time of the singularity was the universe a point? The more I read and find out the more I believe we simply make some of these judgments on our understanding or the laws. It may be possible that humans will never physically be able to understand the universe.

I don’t mean we can’t know vast amounts but wouldn’t there have to be some limit to the abilities of the “human Computer” and it’s I/O and operating system. Our base understandings may be biased by our own sensory abilities.

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[quote]PonceDeLeon wrote:
I’m pretty sure Poliquin knows the answer to this one.[/quote]

Ponce is right, he has a Canadian speedskater who has the biggest legs ever And a PhD in Astrophysics that can answer all your questions pertaining to either topic

(disclaimer - this post is in jest and there is no intentional underlining theme where i am trying to say that i know more about training or astrophysics than Poliquin)

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There’s too much to read in this thread for me while I’m doing homework, but I can add that I had a physics teacher in high school who explained a few basic things about space that made a lot of sense.

If you think of space as being the inside of a sphere, then the explanation of one of those first posts (“infinitely finite”) is provided. There IS a boundary, but you could never really find it because you’d start traveling to another area of space (the way it was decided Earth had flat edges and such…but you just ‘kept going’).

That kind of idea also makes the strange idea that it may be like PacMan styled a little more true. Eventually you travel back to the place from which you came.

This is all just conjecture obviously, but it’s some added material to mull over.

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[quote]Rational Gaze wrote:
It works like this: one twin goes up in a rocket going at high-speed, and returns home. He will have aged less than the other twin who stayed on earth.

Special relativity basically says that a moving clock ticks more slowly than a clock at rest. But the reason for the twin paradox is hard to explain if you don’t have a background in physics.[/quote]

I think of it as a wave. (treat x as time) look at the graph of sin(x) if we think of each of these up and down movements as a tick on the clock, when we speed up and go faster sin(2x) we get to these values quicker. the thing is really the same amount of time has gone by to an outside observer. The person who is traveling faster has more happen while passing through the same amount of time. so in a sense even though the same amount of time to a 3rd party has gone by the one who is traveling faster has more happen outside of there frame of reference.

This may not be coming through well in type and I’m kinda tired.

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[quote]Rational Gaze wrote:
It works like this: one twin goes up in a rocket going at high-speed, and returns home. He will have aged less than the other twin who stayed on earth.

Special relativity basically says that a moving clock ticks more slowly than a clock at rest. But the reason for the twin paradox is hard to explain if you don’t have a background in physics.[/quote]

This is really interesting stuff, and is still confusing me so i got this from

A point of clarification, donâ??t be mistaken to think that if you traveled at the speed of light you would have stayed forever young.

In your reference system, the system that travels at the speed of light, you would grow old the same way as if you were at rest because your biological clock will pace the same. In that sense a photon is not comparable to a living creature. So what’s the story? Well in other reference systems that are much slower than yours, things will occur at much faster rate. So it’s better to think about it as if in slower systems times moves “faster”. It is only when you will stop or slow down to meet other people at other systems you will notice the RELATIVE time difference. This is why it is called the Theory of Relativity and the time difference (dilation) is noticeable only when you compare different reference systems. If Earth had moved at the speed of light, from our perspective in our reference system everything would stay the same.

So, even if you travel at the speed of light, you do grow old.