Hawking changes his mind about black holes


Aside from the fact that this revelation apparently cost Hawking an encyclopedia, how significant an impact will this development have on our study of the evolution of the universe?

This seems like more of a GD question, but…

In a practical sense, it won’t affect our understanding of the evolution of the Universe all that much. A “very long time”, in this context, is many, many times the age of the Universe; how long exactly depends on the black hole, but for a black hole with the mass of the sun (and our understanding of black holes suggests that a black hole would need to be larger than that to actually form out of conventional matter), the time scale we’re talking about is about 21 million trillion trillion trillion trillion trillion years. (Or 2.09 x 10[sup]67[/sup] years for those who like scientific notation.) In contrast, the Universe is currently a “mere” 13 billion years old (or so.)

Now, if we start talking about “primordial black holes” which were formed at the Big Bang, or producing microscopic black holes in particle colliders, then such things might enter the realm of observation; but the former have never been observed; you have to make some non-trivial modifications to our model of the Universe before any particle collider that the folks at Fermilab or CERN could dream up could actually produce microscopic black holes.

I’ll be attending the Dublin conference mentioned in the article, and I’ll try to remember to pop back in here when I get back and summarize.

While you’re waiting, here’s an article about Hawking radiation, which was the first inkling that physicists had that black holes might not actually be black. From this article, it would appear that I messed up my calculation somewhere above, and that it would take a mere three thousand trillion trillion trillion trillion trillion years for a solar-mass black hole to evaporate. Mea culpa.

Irony, here… Hawking also used similar terminology in A Brief History of Time, that because black holed radiate, they aren’t actually all that black. But in a sense, it’s because they’re so black that they radiate. The radiation from a black hole is as near a perfect blackbody spectrum as you’re ever likely to find in this Universe. Now, these recent ideas do seem to be suggesting that a black hole isn’t completely black, which is to say that the radiation from a black hole in some way carries information about what fell into the hole. But this is still far from definite.

I did wonder myself if it wouldn’t be better suited for GD, but for reasons not even known to myself, I decided to put it in GQ. (Mods, please feel free to move)

This is all fascinating stuff (the numbers involved are mind-boggling). I, unfortunately, don’t have anything to add to this erudite discussion, but am quite interested to learn what those in the field think about it.

Again, thanks for your contribution and…happy conference! (I’d LOVE to be there during the coffee breaks! :smiley: )

Oh, please do. I’ve recently rediscovered my interest in cosmology, and have just gotten done reading A Brief History of Time. I’d love to hear the latest and greatest on black holes.

Well, there’s always this