Friday, September 16, 2005

Horizon on Hawking

Last night Horizon was on the well chosen topic of information loss paradox in black holes. It chose to cover the story as Stephen Hawking's "greatest ever mistake", drawing unbidden parallels with Einstein's greatest mistake. It was hard not to get excited about a popularization of such a technical nature, and I felt somewhat let down when we were treated to the usual combination of ominous voice-over (why, oh why, must science be presented as if it's a horror movie?), violins playing purposeful music, dazzling graphics, and vague presentation of the story. In fact the story was shifted away from physics to one questioning Stephen Hawking's scientific reputation leading the Horizon team to entitle their programme not "The Information Loss Paradox" but "The Hawking Paradox".

I admit though that, before I watched the programme, I was excited about it all day; in the best of all worlds I was hoping to hear some commentary on Hawking's most recent paper, perhaps even some insights that might help me understand it. But alas not. The programme aired at 9pm on BBC2 yesterday, and my spirits immediately sank when the announcer introduced it as "the reputation of the world's most famous scientist at stake". The first images we see are from a beach and there's a wall with at least 6ft high graffiti on it, and the largest graffito of all is of Hawking's equation relating entropy and event-horizon area. Perhaps this was also meant to draw parallels with graffiti of E=mc^2, who knows? The voice over begins, and the camera ranges over the beach to an astrologer:
"What if the world were so strange we could never hope to understand it and science was wasting its time? It sounds like the sort of thing a mystic might say but this was a suggestion made three decades ago by the most famous scientist in the world, Stephen Hawking."
From then on one had the idea that the scientific story was going to lag behind the human story, but, for pity's sake, why?

The introduction focussed on Hawking's celebrity, with Kip Thorne saying of him:
"He's absolutely unique, and I think he has been a very important person in both the intellectual and the cultural life of the past century."
These fair comments were countered by the voice-over's,
"But recently doubts have been expressed by some physicists about Hawking's scientific reputation."
Thereby initiating the main story being addressed by Horizon, that perhaps Hawking ain't so great. Frankly this appeared as unfounded, unsupported and scurrilous journalism used to appeal to a wider audience, and at no stage were any of Hawking's conributions to physics not related to information loss discussed.

The information loss paradox was described as the result of a black-hole evaporating to nothing leaving behind only thermal radiation, i.e. carrying no information. That there would be a problem even if the black-hole didn't disappear was not made clear
(There is clarification about where this is a concern from Christophe Galfard in the comments). Without recourse to quantum mechanics this was described as a violation of one of the most fundamental principles of physics, that information is never destroyed. The voice over spookily summarised,
"Effectively bits of the universe are missing...nothing science knows not even our memories could be trusted."
Lawrence Krauss commented, probably to the delight of the Council for making Science Scary who seem to be in charge of Horizon,
"...at its most extreme scale what it means is everything you come to know and love would ultimately disappear."
This scary comment went without any guiding timescales.

Cue Leonard Susskind who was presented as Hawking's adversary in an immense intellectual battle. Susskind described how he felt a need to resolve how it was that one could watch someone cross into an event horizon and potentially be pulled apart, while the same person would feel no great change as they themselves fell across the horizon. Ah, a good old-fashioned change to Eddington-Finkelstein coordinates, at last some firm ground. The voice-over's interpretation of this coordinate change:
"The same equations were saying that someone could be both dead and alive."
Hmph. Susskind described his resolution that allowed both of these possibilities to coexist and resolved the information loss paradox: holography. That the black hole acts like an information projector and that anything that falls into it has its information "beamed" onto the lower-dimensional event-horizon, thus avoiding losing information inside the event horizon. Although quite what was going to happen to the information when the black hole evaporated was not addressed. Susskind's belief's were presented as being vindicated by Maldacena's paper, Eternal Black Holes in AdS. And finally the programme concluded after the Dublin conference where Hawking conceded that information was preserved. So, no chance of an explanation of the sum-over-topologies approach, ho-hum. There is some commentary by Lubos Motl on the paper Information Loss in Black Holes, and if you are interested in holography you could read TASI lectures on the Holographic PrincipleTASI lectures on holography by Bigatti and Susskind.

Of course despite my disappointment with the lack of theory, the human story was appealing. There were some very nice pieces of footage of Hawking working with his students. In one shot, prior to adopting his synthesiser, Hawking is seen talking to what looks like a seminar with the help of a student, Chris Hull. Chris Hull says that they happen to have a model of the universe with them and pulls out a cylinder and puts it on a table in front of the audience. Hawking makes some comments and grins, the student scratches his head and then turns the cylinder the other way up. It is identicle both ways.

Also, there were some encouraging comments about the trials of a student from Christophe Galfard, who, contrary to my earlier scandalous comments, has pointed out that he does not work in the signature (+---), described the start of his PhD with Hawking, saying:
"For the first year-and-a-half every sentence of Stephen's took me about six months to understand."
And of reading Maldacena's paper:
"I took a little while to read it, a little while being about a year-and-a-half."
Again: here, here!

The show ended with Hawking saying:
"I have no intention of stopping anytime soon. I want to understand the universe and answer the big questions, that is what keeps me going."
At no point did the programme mention the word string, nor topology! Is this really the best way to promote science to a popular audience? Could it not be done with at least a little humour, and less of the portentous voice over? Maybe even less of the human-interest story? After all the science is fascinating if communicated well. Oh for a more perfect world.

9 comments:

Simon said...

I agree with what you say, but having watched Horizon often, I was not too disappointed with this one - at least they picked a worthwhile topic. Better than when they did time machines.

BTW, I think the student with the cylinder in the old film clip is Chris Hull. I wasn't sure, but it sounds like him.

P.P. Cook said...

It was a great topic to pick...

Thanks for the id of Chris Hull, if I hadn't taped over my copy of the show in protest (I hope they're reading...) I would doublecheck.

Anonymous said...

A few comments:

The student with the cylinder is Chris Hull, that's correct. And I do not work in +--- signature. But even if I did, there's nothing appalling about that.
The paper by Maldacena is called Eternal black holes in AdS, not external.

In asymptotically flat space, there's no problem as long as the black hole is still there. The information paradox is due to the black hole complete disappearance. In asymptotically AdS spaces, a version of the paradox can be made even if balck holes do not evaporate completely, because
black holes can be eternal there.

P.P. Cook said...

Dear Christophe,

Thanks for your comments on my rant, I have made appropriate changes in the text - can you tell I wanted the Maldacena paper to be called Extremal black hole in AdS? I made a compromise between my wishes and "eternal" and got "external"!

I owe you an apology for my scandalous :) allegation that you might work in (+---): sorry, my mistake, there was an equation on a blackboard that I must have misread.

To all the good physicists who make an honest living using (+---), my apologies for saying it was an "appalling" choice. It's admirable and brave, and if I had the courage to put so many minus signs in my calculations I might even join you. It seems that the GR literature in general prefers (+---) so there are plenty of good reasons for a student to work in this choice. At least in four dimensions, of course in eleven dimensions it's less sane to pick mostly minus.

Best wishes,
Paul

cvj said...

Paul,

Thanks for the summary. Horizon sounds as awful and frustrating as I remember it being since way back. I never get excited any more when such programs are coming up, just a sense of dread.

-cvj

Craig said...

I found all the stupid graphics so annoying and patronising, for instance, when they displayed Hawking's equation and described c not as the speed of light but "the c from Einstein's famous equation," it was ridiculous.

Do they really think that somebody watching the show is going to say "well, I was going to switch channels to Bad Girls but now that they've mentioned that famous c, I'm hooked!"

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