Stephen Hawking brought his famous wit to a star-struck audience of students and postdocs yesterday afternoon at Caltech.
With a couple of lewd jokes and several quips on how he should win a Nobel Prize, Hawking talked about black holes, Hawking radiation–in which quantum effects can cause black holes to radiate and eventually evaporate–and the information paradox, which made news a while ago when Hawking admitted he was wrong (and subsequently lost a bet with physicist John Preskill).
The issue of information loss in a black hole was a major puzzle in the physics community. In the 1997 bet, Hawking and Kip Thorne contended that objects that fell into a black hole were lost forever, and with them any trace of what they were. Hawking compared it to burning an encyclopedia. Even if you burn an encyclopedia, you’re still left with the “information” it contained, only in the form of ashes and smoke. Everything’s there–it’s just a little hard to read. But if that encyclopedia was thrown into a black hole, all of its information would be lost forever, and any Hawking radiation wouldn’t contain any signature of the encylopedia’s existence. Preskill, on the other hand, bet that information could be recovered.
In 2005, Hawking conceded that he was probably wrong, and found a way for information to escape a black hole. Suffice to say, it’s complicated, so I’ll leave it at that. As the winner of the bet, Preskill received a baseball encyclopedia. Hawking joked that maybe he should’ve given Preskill the book’s ashes, instead.
For me, and probably for most of the audience, the coolest part of the lecture was just to see the famous scientist in person. When he first rolled into the auditorium behind the audience, chatter immediately ceased and all heads silently turned toward the science and pop-culture icon. He looked like what you’d think he’d look like: an old guy in a wheelchair. His well-known robotic voice boomed across the auditorium, and everyone patiently waited while he selected his pre-programmed sentences.
In his introductory remarks, Thorne described how Hawking controls his computer–and his speech–with his cheek muscles. Apparently, a bout with pneumonia led to a tracheotomy that left Hawking without his voice box. His computer was specially built for him, and detects twitches and flexing of his cheeks. Instead of a mouse, he moves his cheeks to control the computer. Since he uses the same muscles to scroll for words as he does to eat, Thorne said a meal with Hawking often results in some interesting conversations. Hawking might fire off stray words while zipping over little bumps on the campus grounds. He also communicates with facial expressions, and a heated argument with him can lead to some “vile” expressions, Thorne said.
Hawking, on his annual month-long visit to Caltech, will give the same lecture tonight for the public.
(Given that the most popular search word that leads to this site is “steven hawking”–surprising that all of the searches are for an incorrect spelling–I wonder how this post will fare…).
