16 replies to this topic

[DukeNukem]

These are all basic questions that have been answered 1000 times in topical books. Wikipedia is likely also a good source to review.

In short, all objects in the universe are moving relative to each other, and yes their are new stars still appearing.

[bgwowk]

Space itself is expanding. Galaxies move farther apart from each other as space expands. If you project all this backward in time, there was a time when the whole universe was very small, compressed, and hot. That is the Big Bang.

No new matter is being created. Stars that are being born are being born in galaxies that already exist from left over matter from older stars that exploded. This will eventually stop when the universe runs out of hydrogen to burn in stars.

Thus, the universe had a very hot and bright beginning, and appears headed toward a very cold and dark end.

[Lazarus Long]

And about hydrogen, dosen't it constantly recyle? gas to matirial, matirial to gas?

You are confusing chemistry and physics. Hydrogen isn't being *burned* in the star and chemically combined with other elements; it is undergoing nuclear fusion and becoming helium and other elements. These heavier elements undergo further forms of fusion reaction and are not *generally* returning to being hydrogen even when the atomic instability of the isotope involved induces fission easilly.

It is by this process that most of the heavier elements that compose the matter of solar systems was formed and like the old saying goes; "we are all made of star stuff".

[Lazarus Long]

If space expands and galaxies move away, howcome people forsee collision of 2 galaxies?

Not everthing is moving away from everything else. Some objects are on collision courses and the massive gravity of galaxies and the super massive black holes at their centers increases the attractive force for collision once the bodies are reasonably close enough.

This is not a theory occurance since we can see galaxies colliding with telescopes and also measure that Andromeda is on a collison course with the Milky Way.

[bgwowk]

Yes, galaxy collisions are local effects. Like a cloud of expanding gas in an explosion, gas molecules can still bump into each other, but the overall trend is expansion. The farther a piece of space is away from another piece of space, the faster they recede from each other. The fabric of the universe is expanding.

[bgwowk]

Still confusing about the expanding part, I mean, isn't space infinite and the stars and galaxies are just object?

No. In most cosmological models, which are based on General Relativity, the universe is unbounded but finite like the surface of an expanding sphere. It is however an extremely large "hypersphere", at least 10**20 (1 with 20 zeroes after it) larger than the visible part of the universe we see.

Concepts of the universe existing in a flat 3D space, extending forever backward and forward in time looking like it does now, are not correct. The present condition of the universe is evanescent. It was not always this way, and will not remain this way for very long (cosmologically speaking).

[bgwowk]

This is really the least of your survival problems. But if you find interventive physical eschatology interesting, Google Frank Tipler and baryon tunneling. It really is difficult to predict the future of universes that contain intelligent life. Life changes everything.

[bgwowk]

http://en.wikipedia...._point_(Tipler)

Have fun.