Ray- I'll take your questions starting with the easiest for me to answer.
1. Is it possible that there is another state of matter?
Sure, there are other states of matter. You even mentioned some in
your other questions. For example, if you squeeze nuclei together
enough the quarks in them should form a sort of interacting quark soup,
rather than separate nucleons, sort of like the way when you heat atoms
enough then can form a plasma. Even under much less exotic conditions
there are other states of matter. For example, liquid crystals (like in
watch displays) have some properties like solids and some like liquids.
Liquid crystals alone give quite a number of different states of
matter, qualitatively distinct from each other.
2. If there is no friction/viscosity, doesn't this defy the law of conservation of energy?
Nope. Take a bucket of superfluid that happens to be spinning
around. If there's no viscosity, it will spin the same forever, so you
can directly see conservation of energy. Now take a bucket of spinning
water. Thanks to viscous friction, it will gradually stop. That looks
like it violates conservation of energy. Only when you figure out how
to track the missing energy into thermal forms (the temperature goes up
a little) do you realize that ordinary friction doesn't violate
conservation of energy.
3. I've recently read an article about the possible discovery of
quark stars; if this is found to be a new state of matter, what does
this say to us?
I'm not an expert, but I don't think it would tell us anything very
new. Quark matter was predicted on the basis of what we already
believed about how quarks interact, so its discovery would only confirm
the standard picture (QCD) of those interactions.
4. If the universe were full of space, absent of all other forces
but gravity, and only two objects existed, would gravity reach out
infinitely? How far does the gravitational force reach?
So far as we know, gravity does just trail off gradually. That's true in General Relativity and also in Newton's approximation.
5.Is there an outer limit to the Universe? I know the universe
seems to be expanding, but what if we could some how reach, and then
out run the expansion of the universe? Would we hit a wall, so to
speak, where space/time ends?
The current pictures of our spacetime have no edges in them. We
just don't know whether our spacetime is finite or infinite. If it's
finite, that doesn't mean that you'll hit an edge. It means that if you
and your brother set off in opposite directions, you'll meet up again.
Mike W.
(published on 10/22/2007)
