Quote:
Originally Posted by T@T
Ok, I have another question (last one today I promise) 
If in-fact this video explains expansion(balloon theory) how is it that galaxies collide? It happens all the time, Even our own milky way is suppose to collide with the Andromeda galaxy in a about 3 billion years. |
You could also ask why do solar systems stay together. The expansion is quite weak and is only significant over very long distances.. the distances between galactic clusters and greater. At "smaller" distances (like the distances between galaxies in galaxy clusters) gravity is stronger, so gravity dominates. Andromeda is moving towards us because gravity dominates at that scale.
Same thing for our solar system, the expansion is so weak at that scale the gravity of the sun dominates, or the electromagnetic, weak, and strong forces dominate at the size of our bodies.
Quote:
Originally Posted by robocop
funny thing is this doesn't answer T@T's question at all. I read a lot about physics and still can't quite grasp how lightspeed effects the actual shape of the universe.
|
The "shape" of the universe isn't dictated by light speed, it's dictated by the mass in the universe and the nature of gravity. What you're looking for is called the
Friedmann–Lemaître–Robertson–Walker metric, which is the current best guess about the geometry and topology of the universe.. infinite and flat best guess, though I think there's some other weird multi-dimensional shapes that could fit too.
Quote:
Originally Posted by robocop
below is a picture of the universe from hubble showing the thermodynamic state of matter, except that it's coming from different sources from different distances so this isn't really what things look like, and that's what T@T was asking or hinting at.
|
That's the Cosmic Microwave Background Radiation, basically a picture of the radiation when the universe became transparent as it cooled (called the surface of last scattering). This radiation has been redshifted so much as the universe expanded that it's now at a colour temperature of 2.725 Kelvin, and it'll continue to drop. What that picture shows is the variation in temperature (a variation of only micro Kelvin) of that radiation, which is due to the variations in density of the material of the universe when it became transparent.
More on CMBR:
http://en.wikipedia.org/wiki/Cosmic_...ound_radiation
The thing with distance is it's not a simple definition due to the expanding universe, the limit of light speed, and time being relative, so any answer given (like that the universe is 46.5 billion light years in radius) is given with certain assumptions (like that distance is in comoving coordinates).
Plus we can only talk about the observable universe, that what we can ever possibly see.. the actual universe is probably far bigger, and likely infinite.