>If the temperature of the universe converges to a constant temperature, won't
>it vary depending on the size of it. After all, a compressed gas is much
hotter
>than a gas at ordinary atmospheric pressure, and yet the energy contained
>within the system is the same. Therefore, if the universe is constantly
>changing shape and size, the temperature will never level out at a constant
>value.
>
>I must admit at this point that, as yet, this topic is more of an interest than
>a speciality, so I'll probably fail to argue that convincingly, but I'll have
>a go. Give me about 4 years, and when I finish my degree course in
Astrophysics
>then I'll have another go.
>
>I would have to say though, that although stars do burn out, when a star dies
>it releases all of the gasses that remain, and these go on to make up other
>stars. In the event of a supernova, then the debris of the dead star often
>forms new and smaller stars very rapidly. An example of this, for the
>astronomers out there, might be the Crab Nebula, which is believed to be the
>remnants of a supernova, where burried deep in its heart is a relatively new
>neutron star. But also surrounding it are many other collections of hot
>gasses, which are the beginings of new stars. So it would be true to say
>that eventually all stars are going to burn out, but others will take their
>place.
Stars do not release all of their mass after they burn out. Most of
their material remains, slowly cooling off. Eventually they reach
some ambient temperature...
After awhile there will be very little available material to form
new stars. (But it doesn't really matter - if all the material were
available then as the atomic masses of the matter went up, nuclear
fusion will become more and more difficult anyway... till it is no
longer a viable source of energy.)
>This is just what I understand, and reason, by the way.I would be grateful if
>someone could explain entropy to me in a different way to Stephen Hawking,
as I didn't understand it in his book.
My explanation of entropy:
Entropy is the tendency of closed systems to become more and more
disordered. One consequence is that less and less energy is
available to do work (energy is conserved, so their is a constant
amount of energy, but for instance, as the temperature gradient
becomes smaller, less and less can be done with it). Entropy
can never get smaller (on a macroscopic time scale, in a closed
system). It will always either increase or stay the same. In
interesting systems it rises (work is being done).
Some trivia -
The term entropy comes from the Greek expression of "transformation",
and was suggested by Rudolf Clausius in 1865.
ken