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

The dangers of extrapolation

[phamlen]

Mark Twain wrote on nearly this exact topic in 1883. He wrote a great essay on extrapolation , basing his conclusions on the fact that the Missippi between Cairo and New Orleans was shortening an average of a mile per year for the last two hundred years or so....

To quote:
"Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upward of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact."

-Peter

Re:Shot in the dark

[You're All Wrong]

Probably true within the bounds of the situations the experiments were testing, yes, probably. That's _interpolation_ and is pretty safe for most physics.

However, making prediction what happens outside those bounds is _extrapolation_, and almost all extrapolation is wrong.

Newtonian laws of motion? Extrapolate to high velocities, and you incorrectly predict the orbit of mercury. (Add SR to fix.)

Classical models of black body radiation? Extrapolate to very short wavelengths, and you get the ultraviolet catastrophe. (Add Planck to fix).

However, all these fixes still have _their_ bounds, and you can't use NM+SR to predict behaviour of particles small-enough to have wavelike behaviour.

Extrapolation is what you do when you desperately need more funding...

YAW.

The actual journal article

[Noren]

The journal article that the New Scientist article has made a journalistic hack job of is here. The actual article is not presented as future history; it presents a possibility, a consequence of making an explicitly stated assumption about the nature of dark energy (about which very little is known.)

I also wish to point out that extrapolation can be useful for precisely the reason many are criticizing it: it can reveal where current theories are wrong.