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the expanding universe - someone please explain?
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| Psy-T |
how does infinite space stretch or shrink?
please use analogies and explanations in words rather than formulas, thanks.
if no one can be bothered, just let me know and i'll go hunting the web for information, just rather hear it from you guys. |
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| pkcRAISTLIN |
do you mean how is it expanding?
either way, i dont have a clue ;) good question tho. i hope someone here can help us both out. quantum physics ftw!! :) |
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| Sunsnail |
The big bang happened. All the matter in the universe expanded outward at a constant rate. It is still expanding now. Imagine a single point in space, the origin of the universe. Everything is moving away from that point. It has 3 options in the future:
1) It will keep expanding forever because the outward force is more than the gravitational pull of everything
2) It will stop expanding and start collapsing. The gravity of everything is stronger than the outward force.
3) Gravity and outward force will equal eachother and the universe wont move.
Nothing we need to worry about though... unless you plan on living a LONG LONG TIME |
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| Psy-T |
| quote: | Originally posted by Sunsnail
The big bang happened. All the matter in the universe expanded outward at a constant rate. It is still expanding now. Imagine a single point in space, the origin of the universe. Everything is moving away from that point. It has 3 options in the future:
1) It will keep expanding forever because the outward force is more than the gravitational pull of everything
2) It will stop expanding and start collapsing. The gravity of everything is stronger than the outward force.
3) Gravity and outward force will equal eachother and the universe wont move.
Nothing we need to worry about though... unless you plan on living a LONG LONG TIME |
i can understand relative distance between entities growing, but if there were no entities in the universe, would it still be expending? how would one be able to discern that? (not sure discern is the right word, but hopefully you understood my meaning)
how can something with no end grow? where does it grow to? (same goes for shrink) |
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| occrider |
| Think of three dimensional space as if it were a 2-dimensional point on the surface of a sphere, or the surface of the Earth if you will. One has infinite space on Earth in the sense that you can keep walking around and around and never reach a cliff or an "end". It is in a sense infinite. Now think of this three dimensional space on the surface of the Earth as the Earth expands or shrinks. You still have infinite space but it is expanding or shrinking. It's a little difficult to envision because our perceptions are limited to spatial geometry in 3 dimensions, but I believe that's the best analogy I've heard. |
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| pkcRAISTLIN |
excellent analogy occ.
| quote: | Originally posted by Sunsnail
1) It will keep expanding forever because the outward force is more than the gravitational pull of everything
2) It will stop expanding and start collapsing. The gravity of everything is stronger than the outward force.
3) Gravity and outward force will equal eachother and the universe wont move. |
well, the rate or speed of expansion is increasing, so i dont reckon #2 also known as "the big crunch" will happen (yeah, me with my awesome command & understanding of science and all :rolleyes: ) |
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| Sunsnail |
| quote: | Originally posted by pkcRAISTLIN
excellent analogy occ.
well, the rate or speed of expansion is increasing, so i dont reckon #2 also known as "the big crunch" will happen (yeah, me with my awesome command & understanding of science and all :rolleyes: ) |
Ah, well I haven't really been up to date on this stuff. What I posted above was off the top of my head. |
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| trancaholic |
| quote: | Originally posted by Psy-T
if there were no entities in the universe, would it still be expending? how would one be able to discern that? |
As far as I understand, no.
You might want to read
http://www.amazon.co.uk/exec/obidos...9255026-6368720
It tries to be a laymans explanation of stuff like this. |
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| Sunsnail |
| When people say "the universe is expanding" I do not believe they mean that the nothingness area is expanding. When I say "the universe is expanding" I am implying that the matter that makes up the universe is spreading further apart. The space that this matter can go into is limitless because there is nothing there. What is going to stop matter from expanding? |
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| pkcRAISTLIN |
| quote: | Originally posted by Sunsnail
Ah, well I haven't really been up to date on this stuff. What I posted above was off the top of my head. |
hey, dont listen to me!! :D im happy to repeat stuff ive heard being said by people like hawking, but half the time im not sure if i understand it to begin with ;)
theoretical physics is so far beyond me, but i love it anyway :D actually regular physics is also too hard. well to be honest i failed parts of grade 9 (15yo) science ill have to admit. speak slowly people :D
| quote: | Originally posted by Sunsnail
When people say "the universe is expanding" I do not believe they mean that the nothingness area is expanding. When I say "the universe is expanding" I am implying that the matter that makes up the universe is spreading further apart. The space that this matter can go into is limitless because there is nothing there. What is going to stop matter from expanding? |
i think i get what you mean. and i think i agree. i still cant really comprehend the nothing bit though.
and wtf is an entity?
| quote: | Originally posted by Sunsnail
All this has to do with variable constants. According to this school of thought light travels at a fixed velocity therefore it is constant...unless light travels through water or a vacuum then does that figure change..hence variable constant. Another oxymoron. |
theres some aussie scientist now trying to prove that the theory of relativity isnt correct. hehe, ambitious.
we know gravity can bend it, but how does a vacuum effect the speed of light?
i want my own black hole :cool: |
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| occrider |
| quote: | Originally posted by Sunsnail
When people say "the universe is expanding" I do not believe they mean that the nothingness area is expanding. When I say "the universe is expanding" I am implying that the matter that makes up the universe is spreading further apart. The space that this matter can go into is limitless because there is nothing there. What is going to stop matter from expanding? |
Actually I don't think the matter itself is expanding outwards. Sure matter moves in space but that movement is dictated by gravitational effects. However, there isn't a gravitational field coming from all directions that is pulling matter outwards (I think that would result in some heavily skewed elliptical orbits or something) rather I think that space itself is expanding and the matter is going along for the ride. Think of matter as 2 pen dots on a rubber band which is "space". As the rubber band stretches, the 2 dots do not move on the rubber band but rather "space" moves, contorts, whatever, and brings the dots along with them. Thus space is expanding ... which really cannot be classified as nothing despite the fact that there might not be matter in it. |
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| NebulousQ |
| quote: | Originally posted by pkcRAISTLIN
we know gravity can bend it, but how does a vacuum effect the speed of light? |
The speed of light in constant in different mediums. In a vacuum the speed of light is c, which equals 299 792 458 m / s. Yet in other mediums, such as water, glass, or air, the speed of light is less. Yet within each of those mediums the speed of light is constant. This is basically how fiber optics work, since light moves slower in glass it tends to stay within it. The light "bends" to follow the glass as that provides the path of least resistance.
And to stay on topic:
Have you read the Ultimate Hitchikers Guide to the Galaxy? There is another interest conundrum about the infinite nature of the universe:
The books states that the population of the universe is 0. This is becuase there are an infinite number of planets in the universe and there are only a finite number of populated planets. Therefore the ratio of populated planets to unpopulated planets is 0 since any finite number divided by a infinite number is 0.
I always like that one. |
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