Sunday, August 23, 2015

Bekenstein black hole area and entropy

The NY Times obituary of Jacob Bekenstein says:
acob Bekenstein, a physicist who prevailed in an argument with Stephen Hawking that revolutionized the study of black holes, and indeed the nature of space-time itself, died on Sunday in Helsinki, Finland, where he was to give a physics lecture. He was 68. ...

Black holes are the prima donnas of Einstein’s general theory of relativity, which predicts that space wraps itself completely around some object, causing it to disappear as a black hole. Dr. Bekenstein suggested in his Ph.D. thesis that the black hole’s entropy, a measure of the disorder or wasted energy in a system, was proportional to the area of a black hole’s event horizon, the spherical surface in space from which there is no return. ...

Lee Smolin, a theorist at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, said, “No result in theoretical physics has been more fundamental or influential than his discovery that black holes have entropy proportional to their surface area.”

Dr. Bousso called Dr. Bekenstein “one of the very few giants in the field of quantum gravity.”
Really? Is this the best theoretical physics has to offer?

This formula is just a definition, with no observable consequences. The concept of entropy helps understand thermodynamic reactions, but black holes don't any observable thermodynamics. Hawking says that they will evaporate over the next trillion trillion years, but there is no known way to verify that.

45 years ago some grad student notices that area and entropy of a black hole can increase, so he speculates that there might be some relation. For that he became a giant in the field of quantum gravity? The obituary suggests that he might have won a Nobel Prize, if he had lived long enuf. Maybe if he had lived a trillion trillion years while we all watch a black hole evaporate.

I don't want to badmouth Bekenstein, but it shows the sorry state of theoretical physics and quantum gravity that a trivial definition with no observable consequences is hailed as the greatest achievement in the field.

The string theorists rave about this formula because they say that it is backed up by some calculations by some string theorists. The calculation does not even have much to do with string theory, but the string theorists brag about this as their greatest accomplishment, and their strongest experimental validation. Again, this only shows the sorry state of string theory.

Peter Woit exposes multiverse nonsense:
Susskind deals straightforwardly with the lack of scientific evidence problem by simply saying things that aren’t true:
This idea of a multiverse is not gratuitous speculation. No, it really comes out of both experiment or observational physics about the universe and the current theories as best we understand them.
He doesn’t explain what the experimental evidence for the multiverse is.
and points to this book review:
Physicists have a nerve. I know one (I’ll call him Mark) who berates every religious person he meets, yet honestly thinks there exist parallel universes, exactly like our own, in which we all have two noses. He refuses to give any credit to Old Testament creation myths and of course sneers at the idea of transubstantiation. But, without any sense of shame, he insists in the same breath that humans are made from the fallout of exploded stars; that it is theoretically possible for a person to decompose on one side of a black hole and recompose on the other, and that there are diamonds in the sky the size of the moon.
Physics is supposed to be the hardest of the hard sciences, and physicists the most level-headed. But physics has lost its way, and promotes stuff more outlandish than Biblical creation myths.

1 comment:

  1. >> I don't want to badmouth Bekenstein, but ...

    I don't wanna input 'X' into f(x) = nutskick(x) ... but, here goes my foot. :)