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Stephen Hawking’s Scientific Legacy

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Stephen Hawking died Wednesday morning, age 76. Plenty of memories and tributes have been written, including these by me:

I can also point to my Story Collider story from a few years ago, about how I turned down a job offer from Hawking, and eventually took lessons from his way of dealing with the world.

Of course Hawking has been mentioned on this blog many times.

When I started writing the above pieces (mostly yesterday, in a bit of a rush), I stumbled across this article I had written several years ago about Hawking’s scientific legacy. It was solicited by a magazine at a time when Hawking was very ill and people thought he would die relatively quickly — it wasn’t the only time people thought that, only to be proven wrong. I’m pretty sure the article was never printed, and I never got paid for it; so here it is!

(If you’re interested in a much better description of Hawking’s scientific legacy by someone who should know, see this article in The Guardian by Roger Penrose.)

Stephen Hawking’s Scientific Legacy

Stephen Hawking is the rare scientist who is also a celebrity and cultural phenomenon. But he is also the rare cultural phenomenon whose celebrity is entirely deserved. His contributions can be characterized very simply: Hawking contributed more to our understanding of gravity than any physicist since Albert Einstein.

“Gravity” is an important word here. For much of Hawking’s career, theoretical physicists as a community were more interested in particle physics and the other forces of nature — electromagnetism and the strong and weak nuclear forces. “Classical” gravity (ignoring the complications of quantum mechanics) had been figured out by Einstein in his theory of general relativity, and “quantum” gravity (creating a quantum version of general relativity) seemed too hard. By applying his prodigious intellect to the most well-known force of nature, Hawking was able to come up with several results that took the wider community completely by surprise.

By acclimation, Hawking’s most important result is the realization that black holes are not completely black — they give off radiation, just like ordinary objects. Before that famous paper, he proved important theorems about black holes and singularities, and afterward studied the universe as a whole. In each phase of his career, his contributions were central.

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Happy Birthday, Stephen Hawking

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Sorry for the light blogging of late. Actual work intervenes, and it might remain that way for a while. But I’ll try to pop in whenever I can.

Stephen Hawking is celebrating his 70th birthday today. That in itself is an amazing fact, just as it was amazing when he celebrated his 40th, and 50th, and 60th birthdays, as well as every other day he’s lived and thrived with a debilitating neuron disease. The extra fact that he continues to make contributions to science pushes beyond amazing to practically unbelievable.

Everyone likes to tell Hawking stories, and this blog is no exception. So here is mine, meagre as it is. I’ve gotten more than enough mileage out of this one in person, I might as well put it on the blog so I won’t be tempted to tell it any more.

At the end of 1992 I was a finishing grad student, applying for postdocs. One of the places I applied was Cambridge, to Hawking’s group at DAMTP. There is a slight potential barrier for American students to travel to the UK for postdocs, so they like to get out ahead of things and offer jobs early. Unfortunately I was out of my office the day Hawking called to offer me a position. Fortunately, my future-Nobel-Laureate officemate was there, and he took the call. He explained that Stephen Hawking had called to offer me a job — I was thrilled about the offer, but understood “Hawking called” as metaphorical. But no, Brian later convinced me that it actually was Hawking on the other end of the line, which he described as a somewhat surreal experience. Of course after the initial introduction the phone gets handed over to someone else, but still. …

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Live-Blogging Curiosity, Hawking, and God

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Tonight’s the premiere of Curiosity on the Discovery Channel, featuring Stephen Hawking talking about cosmology and God, followed by the “Curiosity Conversation” panel that I’m on along with David Gregory, Paul Davies, and John Haught. Hawking’s hour-long show is scheduled for 8pm Eastern/5pm Pacific, and will then repeat 3 hours later (11E/8P). Our half-hour panel discussion follows immediately afterward — you do the arithmetic.

There’s a lot to say about these shows, and in particular there’s a huge amount that we didn’t have time to say during the panel. So as I sit in front of the TV, I’ll be live-blogging along by adding updates to this post. This will be the early show, so the fun will happen 8pm-9:30pm Eastern. Hey, Nathan Fillion live-tweets during Castle, so why not me? There is also a chat going on at the Discovery site.

The main attraction of Hawking’s program is not that he has disproven the existence of God. Certainly I don’t think he’s going to be changing the minds of many religious believers. His argument is essentially that the universe is self-contained, and doesn’t really have “room” for God (nor any need to invoke a creator). It’s very easy to wriggle free of that conclusion, if you are inclined not to accept it.

But “changing people’s minds” isn’t the only reason to talk about something, even about controversial issues. Religion, like sex and death, is one of those topics where it’s very difficult to simply have a dispassionate discussion without making people uncomfortable. It can happen within a group of similarly-minded people, of course, but once a wider range of views gets involved, it’s hard to maintain comity. (Comedy, on the other hand, is pretty easy.) I don’t mean everyone has to agree — just the opposite. We should be able to talk about things we completely disagree on, while still maintaining level heads.

That’s why I think this episode of Curiosity is potentially important. It’s a forthright statement of a view that doesn’t often get aired in American media. Even if nobody’s mind is changed, simply talking rationally about this issues would be a step forward.

Pre-show update: I should note ahead of time that I was not wearing a tie. Haught, Davies, and Gregory were all wearing ties. But Hawking wasn’t. Maybe atheists don’t wear ties? (Although I’m pretty sure Jesus never wore a tie, either.)

Start: We begin with a disclaimer! These are Stephen Hawking’s opinions, not those of Discovery. 🙂

4 minutes: I hope the analogy here is clear. “People who believe God made the universe are kind of like the Vikings shouting at the Sun to stop a solar eclipse.”

8 minutes: Snark aside, the message here is a fundamental one. Nature obeys laws! Something that’s certainly not a priori obvious or necessary, but a really profound truth.

14 minutes: I wasn’t able to find an independent confirmation of this story about Pope John XXI condemning the idea of “laws of nature.” (It’s true that he did die when the roof collapsed.) Presumably this refers to the Condemnations of 1277.

20 minutes: The universe is a big, messy, complicated, and occasionally quite intricate place. On the face of it, the idea that it’s all the working-out of some impersonal patterns of matter and energy, rather than being constructed by some kind of conscious intelligence, is pretty remarkable. (But true nonetheless.)

27 minutes: Hey, a tiny ad for Discovery Retreats!

28 minutes: Hawking says Einstein might be the greatest scientist ever. He has long favored Einstein over Newton, I’m not sure why. Hawking appeared on an episode of Star Trek: TNG, where he was a hologram playing poker with Einstein, Newton, and Data. He actually wrote the script, and Newton doesn’t come off well.

36 minutes: Ah, negative energy. Depends on what you mean by “energy,” but this isn’t the venue to get overly technical, obviously. Roughly, matter has positive energy and gravity has negative energy. That’s hopefully enough to help people swallow the crucial point: you can make a universe for nothing. There isn’t some fixed resource, out of which we can make a universe or two, before we hit Peak Universe. There can be an infinite number of universes.

41 minutes: People on Twitter are asking why Hawking doesn’t have a British accent. He easily could, of course; voice-synthesis technology has come quite a way since he first got the system. But he’s said that he now identifies with that voice he got years ago, and doesn’t want to change it; it’s identified with him.

47 minutes: Okay, here’s the payoff. He’s saying that generally we’re used to effects being caused by pre-existing events. (The first step toward a cosmological argument for God’s existence.) You might think that a chain of causation takes you back to the Big Bang, which then requires God as a cause. But no! The Big Bang can just … be.

50 minutes: The point of the black hole discussion is to get to the idea of a singularity, a conjectural point of infinite curvature and density. The Big Bang, in classical general relativity, is also a singular moment. But classical GR isn’t right. We need quantum gravity. Hawking believes that quantum gravity smooths the singularity and explains how there was no pre-existing time. (At least in the TV show, unlike A Brief History, he doesn’t start talking about “imaginary time.”)

56 minutes: Ultimately Hawking’s argument against God is pretty simplistic. He assumes that if God created the Big Bang, God must have existed before the Big Bang, but there was no “before the Big Bang,” QED. It’s easy enough to simply assert that God doesn’t exist “within time” (if that means anything). It would have been better (IMHO) to emphasize that modern cosmology has many good ideas about how the universe could have come to be, so there’s no need to rely on a divine creator.

58 minutes: Final thought from SWH: no life after death! Enjoy it while you’re around, folks. An important message.

Panel discussion starts: Forgot to mention that Paul Davies has shaved off his moustache. Disconcerting.

4 minutes: Also disconcerting: watching myself on TV. Hate it. But I persevere for the greater good.

5 minutes: Here’s Michio Kaku, not saying very much.

7 minutes: Jennifer Wiseman and I were actually grad students together! She’s good people, even if we disagree about the whole God thing.

9 minutes: I come out in favor of basing purpose and meaning on reality. But I’m pretty sure a longer remark was cut off there. Arrrrgh! Nothing nefarious, we intentionally recorded a bit more than they had time to show. But enormously frustrating that there was so little time.

13 minutes: Not sure why we kept talking about the multiverse. Hawking didn’t bring it up, did he?

17 minutes: I thought a lot of what Haught said was not even really trying to argue in favor of God’s existence, but simply expressing a desire that he exist. “God is the grounding of hope” isn’t evidence for God’s existence.

22 minutes: Haven’t said anything completely silly yet, so that’s good. But so little time…

27 minutes: Always time for more Michio!

30 minutes: Arrrrgh again, this time for real: in the live conversation, I had the last word and it was a pretty good one. In the televised program, not so much. Had to end wishy-washy.

Thanks for tuning in. Wouldn’t it have been wonderful to have the time for a real conversation? But big ups to Discovery for hosting the panel at all — it’s a rare event on TV.

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Hawking and God on the Discovery Channel

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Last week I got to spend time in the NBC studio where they record Meet The Press — re-decorated for this occasion in a cosmic theme, with beautiful images of galaxies and large-scale-structure simulations in the background. The occasion was a special panel discussion to follow a Stephen Hawking special that will air on the Discovery Channel this Sunday, August 7. David Gregory, who usually hosts MTP, was the moderator. I played the role of the hard-boiled atheist; Paul Davies played the physicist who was willing to entertain the possibility of “God” if defined with sufficient abstraction, while John Haught played the Catholic theologian who is sympathetic to science.

The Hawking special is the kick-off episode to a major new Discovery program, called simply Curiosity. I predict it will make something of a splash. The reason is simple: although most of the episode is about science, Hawking clearly goes all-in with “God does not exist.” It’s not a message we often hear on American TV.

The atheistic conclusion is really surprisingly explicit. I had a chance to talk to someone at Discovery, who explained a little about how the program came about. The secret is that it was originally produced by the BBC — British audiences have a different set of expectations than American ones do. My completely fictional reconstruction of the conversation would go something like this. Discovery: Hey, blokes! Do you have any programs we could use to launch our major new series? BBC: Sure, we have a new special narrated by Stephen Hawking. Discovery: Perfect! That’s always box office. What’s it about? BBC: It’s about how there is no God. Discovery: Ah.

[Update: Alas, reality is intruding upon my meant-to-be-funny imaginary dialogue. The episode was actually originally commissioned by Discovery, not by the BBC, although it was produced in the UK. More power to Discovery!]

At first, I will confess to a smidgin of annoyance that an opportunity to talk about fascinating science was being sacrificed to yet another discussion about religion. But quickly, even before anyone else had the joy of pointing it out to me, I realized how spectacularly hypocritical that was. I talk about religion all the time — why shouldn’t Stephen Hawking get the same opportunity?

The more I thought about it, the more appropriate I thought the episode really was. I can’t speak for Hawking, but I presume his interest in the topic stems from similar sources as my own. It’s not just a coincidence that we are theoretical cosmologists who happen to go around arguing that God doesn’t exist. The question of God and the questions of cosmology arise from a common impulse — to understand how the world works at its most fundamental level. These issues naturally go hand-in-hand. Pretending otherwise, I believe, probably stems from a desire on the part of religious believers to insulate their worldview from scientific critique.

Besides, people find it interesting, and rightfully so. Professional scientists are sometimes irritated by the tendency of the public to dwell on what scientists think are the “wrong” questions. Most people are fascinated by questions about God, life after death, life on other worlds, and other issues that touch on what it means to be human. These might not be fruitful research projects for most professional scientists, but part of our job should be to occasionally step back and look at the bigger picture. That’s exactly what Hawking is doing here, and more power to him. (In terms of his actual argument, I’m sympathetic to the general idea, but would take issue with some of the particulars.)

Nevertheless, Discovery was not going to feature an hour of rah-rah atheism without a spoonful of sugar to help the medicine go down. Thus, our panel discussion, which will air immediately after the debut of Curiosity (i.e., 9pm Eastern/Pacific). The four of us had fun, and I think the result will be an interesting program — and hopefully I did the side proud, as the only legit atheist participating. Gregory seemed to enjoy himself, and joked that he might have to give up politics to do a weekly show about cosmology. (A guy can dream…) But we all agreed that it was incredibly frustrating to have so little time to talk about such big issues. The show will run for half an hour; subtract commercials, and we’re left with about 21 minutes of substance. Then subtract introduction, questions, some background videos that were shown … we three panelists had about five minutes each of speaking time. Not really enough to spell out convincing answers to the major questions that have troubled thinkers for centuries. Hopefully some of the basic points came across. Let us know what you think.

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Stephen Hawking Settles the God Question Once and For All

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Stephen Hawking has a new book coming out (The Grand Design, with Leonard Mlodinow). Among other things, he points out that modern physics has progressed to the point where we don’t need to invoke God to explain the existence of the universe. This is not exactly a hot flash — I remember writing an essay making the same point for a philosophy class my sophomore year in college — but it makes news because it’s Hawking who says it. And that’s absolutely fine — Hawking has a track record of making substantial intellectual contributions, there’s every reason to listen to him more than random undergraduates waxing profound.

This issue is, of course, totally up my alley, and I should certainly blog about it. But I can’t, because I’m on hiatus! (Right?) So, as an experiment, I made a video of myself talking rather than simply typing my words into the computer. Radical! Not sure the amount of information conveyed is anywhere near as large in this format, and obviously I didn’t sweat the production values. I fear that some subtleties of the argument may be lost. But if we’re lucky, other people elsewhere on the internet will also talk about these questions, and we’ll get it all sorted out.

Let me know if the Grand Video Experiment is worth repeating and improving, or whether it’s just a waste of time.

Something that I should have said, but didn’t: there doesn’t need to be some sophisticated modern-physics answer to the question “Why is there something rather than nothing?” The universe can simply exist, end of story. But it’s still fun to think carefully about all the possibilities, existence and non-existence both included.

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Hawking: Beware the Alien Menace!

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Okay, that’s a bit alarmist. But Stephen Hawking has generated a bit of buzz by pointing out that contact with an advanced alien civilization might not turn out well for us backward humans. In fact, we should just try to keep quiet and avoid being noticed.

“If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,” he said.

Prof Hawking thinks that, rather than actively trying to communicate with extra-terrestrials, humans should do everything possible to avoid contact.

He explained: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet.”

To which I can only say: yeah. Sounds about right. If aliens were sufficiently enlightened to be utterly peace-loving and generous, it would be great to have back-and-forth contact with them. But it’s also possible that they would simply wipe us out — not necessarily in a Mars Attacks! kind of invasion, but almost without noticing (as we have done to countless species here on Earth already). So how do you judge the risk? (Dan Drezner gives the interplanetary-security perspective.)

It’s like the LHC doomsday scenarios, but for real — the sensible prior on “murderous aliens” is much higher than on “microscopic black hole eats the Earth.” Happily, a face-to-face chat seems unlikely anyway. Nothing wrong with listening in, on the unlikely chance that the aliens are broadcasting their communications randomly throughout the galaxy. Besides, a little advance warning wouldn’t hurt.

Update: I had forgotten that we had already discussed this a couple of years ago. Old bloggers tend to repeat themselves.

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Stephen Hawking Hospitalized

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As you may have heard, Stephen Hawking has been rushed to the hospital after falling very ill. He has been struggling with a chest infection for several weeks, and has had to cancel some public appearances. A press officer from Cambridge University later added that he has improved, and is now in comfortable condition.

Not much to add, except that we all hope for a speedy recovery, and that is back writing papers and giving lectures before too long.

Update: Associated Press, reporting from another statement released by Cambridge, says Hawking is expected to make a complete recovery.

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Guest Post — Kip Thorne on Stephen Hawking

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Most physics fans out there have probably heard of Kip Thorne, author of Black Holes and Time Warps and some other books. If you polled physicists to find out who they thought had been the most influential American scientist doing research in general relativity over the past several decades, Thorne would win hands-down. (Here’s a recent interview in Discover.)

And if you dropped the delimiter “American” from the question above, the winner would undoubtedly be Stephen Hawking. So we’re very happy to have a guest post from Kip, announcing an upcoming talk by Hawking.

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Left to right: John Preskill, Kip Thorne, and Stephen Hawking.

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Stephen Hawking is coming to town – to Pasadena, that is.

Caltech, in Pasadena, California, is Hawking’s home away from home. Since 1991 he has spent roughly a month a year here as our Sherman Fairchild Distinguished Scholar. This year he flies in from his English home at the end of February, then heads off to Texas in early April.

He arrives with an entourage of five care givers to tend to his physical needs, one or two family members, several graduate students, and a “graduate assistant” who handles logistics and serves as general fixit-person for his computer system and mechanized wheel chair. His current chair is new and sophisticated. At the flick of a switch, its hydraulics can lift him up to a standing person’s eye level or slide him down near ground level for high-speed chases — he has been known to take pleasure from running over the toes of university presidents.

Hawking’s Pasadena sojourns are rather like Einstein’s in the 1930s. Caltech is an intellectual magnet – a crossroad for ideas about the cosmos and the fundamental laws of nature, which are Hawking’s passion. He contributes mightily to the ferment, and partakes. Our California night life (LA, not Caltech!) is also pretty good; and Hawking, like Einstein, is a party animal, only more so. During his annual month here, my own social life intensifies five-fold just from being his closest California friend. He loves opera, theater, jazz clubs, barbecues that he hosts in the patio of his Pasadena home, and dinners with fine wine – especially an Indian Feast prepared for him by Caltech undergraduates. Yes, we geeks can cook up a storm – well, not me, but the younger generation.

Conversation with Stephen is slow, about 3 words a minute, produced by Stephen moving a muscle in his face (imaged by a lens and photodetector) to control a cursor on his computer screen. It’s slow, but rewarding. You never know, until his sentence is complete, whether it will be a pearl of wisdom or an off-the-wall joke. Faster speeds are on the horizon: computer control via brane waves, without drilling a hole in his head (he’s opposed to that). But he resists changing technology, even without drilling, until forced to. “I can’t believe it’s as good as what I have.” (It actually is; my wife has a friend with ALS who proves it so.)

Most of Hawking’s Pasadena time is spent thinking, conversing, and working on projects. Jim Hartle drives down from Santa Barbara to continue their decades-long research collaboration on the birth of the Universe. Leonard Mlodinow, a Pasadena-based free-lance writer, toils with him on a book: in the past, A Briefer History of Time; now, their forthcoming The Grand Design. And there are drives to Hollywood to film for Star Trek or the Simpsons or the forthcoming Stephen Hawking’s Beyond the Horizon.

On each Pasadena visit, Hawking gives a lecture for the general public – always before in Caltech’s limited-seating Beckman Auditorium, but this year in the newly renovated Pasadena Convention Center, at 8PM, Monday March 9. “Why We [the human race] Should Go into Space” is his title. It’s an opportunity to see him in action, be immersed in his mind’s world, and – if last year’s lecture is any indication – participate in a happening. Tickets are available from the Caltech ticket office, (626) 395-4652, at $10 each.

The last time I saw Hawking speak to such a large audience, thousands, was in a converted railway station in Santiago Chile, soon after General Pinochet’s regime gave way to civilian rule. It was quite a show. Hawking made a grand entrance to rock music and charmed the crowd. The President of Chile and other civilian officials sat on one side of the giant stage, the military brass on the other, with enormous tension between them; they were hardly speaking to each other in those days. Only Hawking could bring them into the same room. His aura works magic. The next day the military flew us to Antarctica: a C130 cargo plane filled with TV cameras, journalists and physicists. It was August, the Antarctic winter, the first flight to Antarctica in more than a month due to winter storms. It was a Hawking Adventure, one among many. He lives life to the fullest. He will fly on a rocket into space soon.

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Hawking bests Beckham

… as a role model for British youth. But Hawking didn’t take first prize; he lost out to rugby hero Johnny Wilkinson. What all this means, I have no idea.

Hawking speaks

As anticipated, Stephen Hawking gave his talk on black hole information loss at the GR17 conference in Dublin today; newspaper stories are already popping up, although they don’t tell us much we didn’t already know. I’ll try to have some incisive commentary soon; in the meantime, why not just get right to the heart of the matter? Here are the press release and transcript for Hawking’s talk.

Judge for yourselves! At least, if you’re up on the background reading about Euclidean quantum gravity and the AdS/CFT correspondence. Thanks to Dennis Overbye of the New York Times for forwarding the material.

Update: Peter Woit has a parsing of what Hawking is trying to say. I think the most direct paragraph is probably this one:

So in the end, everyone was right, in a way. Information is lost in topologically non trivial metrics, like the eternal black hole. On the other hand, information is preserved in topologically trivial metrics. The confusion and paradox arose because people thought classically, in terms of a single topology for spacetime. It was either R4, or a black hole. But the Feynman sum over histories, allows it to be both at once. One can not tell which topology contributed the observation, any more than one can tell which slit the electron went through, in the two slits experiment. All that observation at infinity can determine, is that there is a unitary mapping from initial states, to final, and that information is not lost.

The idea seems to be that, so far as information measured at infinity is concerned, when we integrate over all possible geometries the relevant ones are those that don’t have black holes at all, merely apparent horizons. Some evidence for this point of view is adduced from AdS/CFT (the connection, first discovered by Juan Maldacena, between certain configurations of quantum gravity and certain field theories in one less spacetime dimension).

When we ultimately agree on the resolution of the information paradox, this idea may very well be part of the story. For the moment, it doesn’t seem like a very practical suggestion, to say the least; it amounts to a promise that, if only we could actually do the path integral for Euclidean quantum gravity, all the information would be preserved and end up in the outgoing Hawking radiation. It remains the case that most people are quite skeptical that we will ever make sense of the Euclidean path integral, especially in the semi-classical regime Hawking makes use of. So one way or another, there’s still a lot of work to be done!

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