The Big Rip

WolfWithoutAClause writes "It's been known for decades that the universe is expanding. The current evidence points to this rate of expansion increasing, and if so, there's no obvious reason why the expansion rate couldn't continue to increase ever faster. A physicist, Simon Caldwell, has taken this to inevitable conclusion and suggested the expansion will eventually reach a point where the expansion rate is so high that any surviving people will ripped apart, followed a millisecond later by the destruction of all the atoms in the universe. Ouch. New Scientist says we may only have 22 billion years left. Almost enough time for a quick game of Everquest then."

Comments

Re:New Scientist

[Goldsmith]

Black holes have already been shown to "evaporate". That's Stephan Hawking's claim to fame really. Basically, by using conservation of energy and quantum mechanics, he was able to show that black holes would convert mass into very high energy light waves, which would then tunnel out. Small black holes could then potentially evaporate away.

Re:New Scientist

[looseBits]

The other mechanisim for black whole evaporation concerns virtual particles. If a e-/e+ pair get created right on the event horizon, the positron can possibly fall beyond the horizon and the electron could escape. The positron would then destroy an electron inside the backhole and decrease its mass. The reverse situation is forbidden as the electron wouldn't be elliminated inside the black whole and the positron may exist for a decent amount of time before coliding with another electron, thus breaking dE*dT = Hbar.

That's the way I understand but I may be an idiot.

Universal expansion doesn't mean *we* expand!

[astroboscope]

Any reasonably dense collection of matter (like a planet, our solar system, and our galaxy) is gravitationally bound and stays together. Universal expansion means that the galaxies get farther apart, not that they get bigger.

Shame on New Scientist.

And now the above, with (a little) math. The gravitational force between two objects is basically (leaving out mass)

F = -k / r^2 + L * r

where k is a constant, r is the separation between the 2 objs, and L is either a constant or a function of time (we don't know yet).

The k term is good old Newtonian (or even Einsteinian up until a couple of years ago) gravity. Strong for small r, weak for low r.

The L term represents the new discovery that the universal expansion is accelerating. It is (unnoticeably) weak on small scales, and only important for large r (i.e. size of the visible universe). For the L term to matter on planetary scales, it would have to become much larger in the future. But we just discovered that it even exists - how it behaves with time is the next thing to find. So don't worry (yet ;-).