Expanding Universe

[alice3]

If the universe is expanding, does that mean that all matter inside it is also expanding, ie. humans?

[Siguy]

No, it is expanding as in all of the galaxies are moving away from each other and dark matter or just emptiness is filling in the gaps and in time all of the stars move away from each other, and then:

a.) The universe collapses into the big crunch

b.) The whole universe just keeps on expanding and then just freezes up when all of the stars are black holes and black dwarfs and there is no radiation left

c.) Every particle in the universe decays into radiation

d.) The big rip, which because I'm really bad at explaining things, you would be better off asking someone else about.

e.) Another theory about the fate of the universe that I have left out.

[Ken G]

That's right, and note that if absolutely everything expanded, we'd have no way of saying that anything did.

[01101001]

If you have other questions about cosmology, you may enjoy the Preposterous Universe Cosmology Primer (http://preposterousuniverse.com/writings/cosmologyprimer/index.html) and FAQ (http://preposterousuniverse.com/writings/cosmologyprimer/faq.html). For instance, applying to this topic:

Could we detect the expansion of the universe by trying to measure the expansion of the solar system?
No. Any system that is bound together by internal forces -- whether it is a table, the solar system, or the galaxy -- does not expand along with the universe. (Not just that it only expands slightly; it really doesn't expand at all, or at least not because of the expansion of the universe.) To observe the expansion, we need to study objects that are very distant, not directly bound to us by gravity or anything else.

[EvilEye]

Why is it so difficult for us as people to understand that the universe will just keep expanding?

So what if the earth is just rock in nothingness in a billion years? It won't cease to exist. It just will be by itself and cold and lonely.

[dhd40]

That's right, and note that if absolutely everything expanded, we'd have no way of saying that anything did.

You hit the nail on the head !

[alice3]

You hit the nail on the head !

The red shift would still be visible.
Thus there surely is no real way to discover if we ourselves are expanding or not?

[Ken G]

The red shift would still be visible.
Thus there surely is no real way to discover if we ourselves are expanding or not?

If we are expanding, the redshift would not be visible to us-- redshift is an increase in wavelength, but if our rulers were expanding too, we would notice no redshift.

[Cougar]

If you have other questions about cosmology, you may enjoy the Preposterous Universe Cosmology Primer.... (http://preposterousuniverse.com/writings/cosmologyprimer/index.html)
Great link. Sean Carroll is excellent:

In cosmology, the curvature of spacetime comes from two contributions: the curvature of space by itself, and the expansion rate of the universe. The curvature of space is the same throughout space, and can be positive, negative, or zero; recent observations of the Cosmic Microwave Background indicate that it is close to zero. General relativity then relates the expansion rate and spatial curvature to the energy density of the universe... and we know how the energy density changes as the universe expands, we can reconstruct the entire expansion history of the universe.