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NASA: Evidence Favors Infinitely Expanding Universe
Chris Gondek writes "The Sydney Morning Herald has a story here about how NASA is expected to announce this week that it has proved the existence of "dark energy," a cosmic force that counteracts gravity and will keep the universe expanding forever. The announcement will effectively demolish the theory that life will be wiped out in a "big crunch" when the universe collapses, and should end decades of academic dispute. Scientists ranging from Stephen Hawking, the Cambridge University physicist, to Albert Einstein, have argued that the universe eventually will stop expanding and then implode under the force of gravity, destroying all life. The Chicago Sun Times has also got some info."
So the universe won't be wiped out by a big crunch.
What a relief. I was worried.
The universe will be wiped out by the heat death of the universe instead.
(Or am I incorrect in my understanding?)
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Expansion of the universe doesn't actually mean the space between the atoms in your body increases. The atoms in your body are tightly coupled by strong electromagnetic forces, which are stronger than the expansion of the universe. Imagine a cardboard disc on the elastic surface that usually represents spacetime - several cardboard discs will grow apart as you stretch the surface, but the discs themselves will not grow, they are rigid because of the internal forces.
Those discs are actually of sizes somewhere around clusters of (billions of) galaxies, so the atoms in your body are fairly safe.
Daniel
Carpe Diem
Thus finally allowing Mickey Mouse to pass into the public domain.
> Whew! That's a relief!
Reminds me of the story of the student of cosmology who frantically waved his hand until the annoyed professor finally called on him.
"Professor, would you mind repeating what you just said about the end of the universe?"
"I said that according to recent estimates it would take place in about 200 billion years."
"Oh, thank God, you really had me worried there for a minute! I though you said million!
How the hell can they predict what the universe is going to do in trillions of years, but I can't get an accurate weather forcast for the next 24 hours??
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My guess is that they are talking about the results from MAP. This is a satellite that was looking at the CMB. Unfortunately, this won't tell us one bit about dark energy. What it tells us about is the total matter-energy budget of the universe. But we've known that the universe is "flat" since COBE (the last satellite to look at the CMB).
The basic way at looking at cosmological parameters is this: CMB tells us about the geometry of the universe (Omega_total = Omega_matter + Omega_energy), clustering tells us about the matter content (Omega_matter), and supernovae tell us about the acceleration of the universe (Omega_matter - Omega_energy).
Only supernovae have given us direct evidence that the universe is accelerating.
It's kind of a funny term. Heat death is actually the complete conversion of all the free energy in a system (in this case, of all systems) into the corresponding entropy. It's the victory of the second law of thermodynamics. It's not that all the energy goes away, but that it becomes so evenly spread that no further work is possible - there are no more free energy gradients to traverse. So it's not the death of heat, it's a death in heat - literally a tepid cosmos. ;)
As I noted in another message, an infinitely expanding universe means that the temperature of the heat-dead cosmos will constantly drop as the volume increases. It will asymptotically approach absolute zero.
Some others have noted that there are theories where energy and/or matter are spontaneously created in empty space. These can coexist with the heat death fate if the new energy is also evenly spread, which it probably would be in such a uniformly boring heat-dead universe. Still no way to create a new free energy gradient.
I find this an interesting fate because it's also reflected in some religions and philosophies, where everything becomes one at the end of time.