Bet 7

Duration ? years (02002-???)

“The universe will eventually stop expanding.”

Danny Hillis

Nathan Myhrvold

STAKES $2,000

will go to The Long Now Foundation if Hillis wins,
or The Institute for Advanced Study if Myhrvold wins.

Hillis's Argument

Cosmology is subject to fads. If at any other point in time I'd bet that the current scientific consensus was wrong, I would have been right. Certainly there's a lot of room for surprises. We already know that there are all kinds of dark matter, and there may be all kinds of dark energy out there too -- maybe including one that's pushing in the other direction. What I'm really betting on is that the universe will turn out to be complicated in directions we haven't even figured out yet.

For instance, I don't believe that the measurements that show the universal expansion is accelerating are necessarily true. There's a long chain of evidence leading up to that conclusion, and I suspect there are mistakes in that chain. We have to do an awful lot of extrapolating when we measure things like the redshifts of supernovae at the edge of the universe, and I don't think we have things as neatly figured out as some people seem to project. Maybe light actually loses energy as it propagates over long distances. I'm not saying this is true, but something like that would throw off redshift measurements entirely.

Even if the expansion is accelerating as the evidence currently suggests, it may not continue to do so. We do not have any good theory of why it should be accelerating at all, much less why it should do so in the future. To me, this unexplained acceleration is an indication that we do not have it all figured out yet. I am expecting surprises. Not only is the world more interesting than we expect, it's more interesting than we can expect.

Myhrvold's Argument

I think the evidence is pretty consistent [that we're going to end up in a cold, dark universe]. The reason to believe in a closed universe is either because you want to be contrary, or because you subscribe to an aesthetic notion of cosmology. I mean, it's kind of cool to think of the whole thing expanding and contracting: throbbing there for all time. [But appealing or not, most estimates about the pressure and critical mass of the universe right now make me win.] First, empirically, we have the fact that the universe is expanding right now. Also, in the past twenty years, astronomers have developed very clever, indirect ways of finding dark matter and they've discovered that there isn't nearly enough [to collapse the universe] -- not by a factor of ten. Finally, there are theories in cosmology that embrace the idea that the universe is a random accident, like a bubble in a bottle of fizzy water. In that scenario, bubbles like our universe form, and they expand, and they go away. [Take the evidence together and ] That's why I think I've got the upper hand here.