January 2008

arxiv Find: What is the Entropy of the Universe?

And the answer is: about 10102, mostly in the form of supermassive black holes. That’s the entropy of the observable part of the universe, at any rate. Or so you will read in this paper by Paul Frampton, Stephen D.H. Hsu, Thomas W. Kephart, and David Reeb, arxiv:0801.1847:

Standard calculations suggest that the entropy of the universe is dominated by black holes, although they comprise only a tiny fraction of its total energy. We give a physical interpretation of this result. Statistical entropy is the logarithm of the number of microstates consistent with the observed macroscopic properties of a system, hence a measure of uncertainty about its precise state. The largest uncertainty in the present and future state of the universe is due to the (unknown) internal microstates of its black holes. We also discuss the qualitative gap between the entropies of black holes and ordinary matter.

It’s easy enough to plug in the Hawking formula for black-hole entropy and add up all the black holes; but there are interesting questions concerning the connection between the entropy of matter configurations and black-hole configurations. They are explored in an earlier paper by Hsu and Reeb, “Black hole entropy, curved space and monsters,” which Steve blogged about here.

arxiv Find: What is the Entropy of the Universe? Read More »

13 Comments

Make the World Better … For Science!

A couple of simple ways you can make the world a better place without leaving the comfort of your keyboard.

First, the American Physical Society has set up a convenient web page from which you can write to your representatives in Congress to voice your displeasure concerning the unexpected budget cuts that have decimated U.S. physics, particle physics and fusion research especially. As APS President Arthur Bienenstock writes:

Congress wrapped up the Fiscal Year 2008 (FY08) budget just before adjourning for the year. The budget, which wipes out $1 billion in increases approved last summer for the National Science Foundation (NSF), the Department of Energy’s Office of Science (DOE Science) and the NIST laboratories, does irreparable damage to science and abandons the Innovation/Competitiveness initiatives of Congress and the Administration.

While DOE Science programs received a 2.5 percent increase overall (exclusive of earmarks), they will decline by about one percent after inflation. High-energy physics and fusion will feel the greatest pain. High energy physics will likely have to eliminate hundreds of jobs, halt work on both the NOvA, the next step in neutrino physics at FermiLab and partially furlough many remaining employees. The Omnibus bill for FY08 also stopped R&D on the International Linear Collider project, an international high-precision step beyond the Large Hadron Collider, and zeroed out the U.S. contribution to the international ITER project, designed to demonstrate the scientific and technological feasibility of fusion energy. These actions are severely damaging to the U.S. standing in the international scientific community.

Second, Steinn has come up with the clever idea of making our own Presidential Science Debate (just in case the official one doesn’t come to pass, or at least while we’re waiting). There are a pair of upcoming primary debates January 30/31, one for each party, and the Politico is soliciting questions to be asked of the candidates. So let’s flood their inbox with sensible questions! Nothing about boxers v. briefs or whether they believe in the literal reality of transubstatiation — let’s ask about their commitment to basic research, their views on manned vs. robotic exploration of space, the promise of alternative energy sources, what have you.

Make the World Better … For Science! Read More »

6 Comments

Is the Universe a Computer?

Via the Zeitgeister, a fun panel discussion at the Perimeter Institute between Seth Lloyd, Leonard Susskind, Christopher Fuchs and Sir Tony Leggett, moderated by Bob McDonald of CBC Radio’s Quirks & Quarks program. The topic is “The Physics of Information,” and as anyone familiar with the participants might guess, it’s a lively and provocative discussion.

A few of the panel members tried to pin down Seth Lloyd on one of his favorite catchphrases, “The universe is a computer.” I tackled this one myself at one point, at least half-seriously. If the universe is a computer, what is it computing? Its own evolution, apparently, according to the laws of physics. Tony Leggett got right to the heart of the matter, however, by asking “What kind of process would not count as a computer?” To which Lloyd merely answered, “Yeah, good question.” (But he did have a good line — “If the universe is a computer, why isn’t it running Windows?” Insert your own “blue screen of death” joke here.)

So I tried to look up the definition of a “computer.” You can open a standard text on quantum computation, but “computer” doesn’t appear in the index. The dictionary is either unhelpful — “a device that computes” — or too specific — “an electronic device designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of these operations.” Wikipedia tells me that a computer is a machine that manipulates data according to a list of instructions. Again, too specific to include this universe, unless you interpret “machine” to mean “object.”

I think the most general definition of “computer” that would be useful is “a system that takes a set of input and deterministically produces a set of output.” The big assumption being that the same input always produces the same output, but I don’t think that’s overly restrictive for our present purposes. In that sense, the laws of physics act as a computer: given some data in the form of an initial configuration, the laws of physics will evolve the configuration into some output in the form of a final configuration. Setting aside the tricky business of wavefunction collapse, you have something like a computer. I suppose you could argue about whether the laws of physics are “the software” or the computer itself, but I think you are revealing the limitations of the metaphor rather than learning something interesting.

But if we take the metaphor at face value, it makes more sense to me to think of the universe as a calculation rather than as a computer. We have input data in the form of the conditions at early times, and the universe has calculated our current state. It could have been very different, with different input data.

And what precise good does it do to think in this way? Yeah, good question. (Which is not to imply that there isn’t an answer.)

Is the Universe a Computer? Read More »

68 Comments

Again with the De-Lurking

Posting is slow, partly because of other commitments, and also because my co-bloggers are poopyheads. So this is as good a time as any to resurrect our occasional de-lurking threads, in which loyal readers who tend not to comment on ordinary posts can peek their heads up and introduce themselves. If you see your shadow, it’s six more weeks of winter.

Don’t worry, there are great things ahead, including some potentially very cool guest blogging (you know who you are). And you are welcome to take the opportunity here to advertise important events or links that you think people should know about — for example, Chanda points us to the 2008 joint annual meeting of the National Society for Black Physicists and the National Society of Hispanic Physicists to be held in Washington DC on February 20-24, 2008. And I can point you to the upcoming Categorically Not in Santa Monica on January 27, featuring what promises to be a lively discussion on Hollywood Physics. Stuff like that.

Again with the De-Lurking Read More »

75 Comments

Code Words

One of the skills that many successful politicians have is the ability to speak separately to two audiences using the same words. It used to be that you could speak to different groups by just saying different things — go visit them, and tell them what you want them to hear. But these days, the default assumption is that everything you say in every context is up on YouTube the next day, so you have to be more subtle. A great strategy, if you can master it, is to use code words — language that seems sensible but unremarkable to the majority of listeners, but carries special meaning for a particular audience. George W. Bush is a master of the technique, but both winners of last week’s Iowa caucuses have also demonstrated the ability.

For Barack Obama, the particular audience is African-Americans. He rarely brings up race directly, but continually hammers on the theme of bridging divides and bringing people together. The surface appeal is to overcoming the tensions between Blue and Red America, but the parallels with Black and White America are pretty clear. More subtly, he borrows phrases from the civil rights movement — “the fierce urgency of now” — that have powerful resonance for the people who fought in those struggles.

For Mike Huckabee, the particular audience is evangelical Christians. A good example of Huckabee’s use of code words was flagged by Josh Marshall, who picked up on the repeated use of a notion of “vertical thinking.” Without much explanation, Huckabee drops this phrase liberally into his speeches, and it is displayed prominently on his website.

Huckabee vertical thinking

What’s going on there? Marshall found explanations here and here. I suppose context has given away the secret by now, but “vertical thinking” refers to how we conceptualize the role of God as the origin of all things.

vertical thinking

“Horizontal thinking,” meanwhile, is what happens when you leave “Man” to figure it all out by himself.

horizontal thinking

Count me as a committed horizontal thinker. There’s a great benefit to recognizing that it’s we human beings who are conducting an ongoing conversation about how the world works and how we should live our lives, rather than taking instructions from a (literally) higher authority — namely, we can change our minds when we realize that we’ve been making a mistake. If we’re beholden to a set of ancient cryptic mythological texts that were all about reinforcing the prevailing norms at the time, we get stuck with vertical thinking of the form “Wives are to voluntarily submit themselves to their husbands as the head in their marriage.”

Most of we horizontal thinkers didn’t even notice Huckabee’s formulation, I’m sure. It will be interesting to see what happens if he wins another primary or two.

Code Words Read More »

31 Comments

G’Kar

Andrew Olmsted was a U.S. soldier who occasionally posted at Obsidian Wings as G’Kar. He was killed yesterday in Iraq. Andrew (who I didn’t know personally) had written a piece with the specific intention of having it posted only in the event of his death. It was posted today by hilzoy.

I write this in part, admittedly, because I would like to think that there’s at least a little something out there to remember me by. Granted, this site will eventually vanish, being ephemeral in a very real sense of the word, but at least for a time it can serve as a tiny record of my contributions to the world. But on a larger scale, for those who knew me well enough to be saddened by my death, especially for those who haven’t known anyone else lost to this war, perhaps my death can serve as a small reminder of the costs of war. Regardless of the merits of this war, or of any war, I think that many of us in America have forgotten that war means death and suffering in wholesale lots. A decision that for most of us in America was academic, whether or not to go to war in Iraq, had very real consequences for hundreds of thousands of people. Yet I was as guilty as anyone of minimizing those very real consequences in lieu of a cold discussion of theoretical merits of war and peace. Now I’m facing some very real consequences of that decision; who says life doesn’t have a sense of humor?

I don’t think the war in Iraq was a good idea. But I have enormous respect and admiration for the people who volunteer and put their lives on the line to serve in the military; they’re not the ones who decide what wars to get into. My heart goes out to Andrew’s friends, colleagues, and family.

G’Kar Read More »

23 Comments

A Form of Not Being Sure

I bought this print to decorate the wall of my office. I like the art, and the title is “Time’s Arrow,” so how could I resist?

Time’s Arrow by Costa

But I did have a worry: the painting clearly involved text, which I tend to think is an aesthetic mistake — it brings a depressing specificity to what should be an open-ended interpretive process. And here the resolution of the online image was too small for me to make out the words, so what if the text was completely dopey?

Now it has arrived, and here is the main text:

Living is a form of not being sure, not knowing what next or how. The moment you know how, you begin to die a little.

The artist never entirely knows. We guess; we may be wrong, but we take leap after leap in the dark.

I kind of like it.

A Form of Not Being Sure Read More »

15 Comments

What Have You Changed Your Mind About?

This year, the Edge World Question Center asks people what they have changed their minds about. Here are excerpts from some of the most interesting answers. (Not that I necessarily agree with them.)

Joseph LeDoux changed his mind about how memories are accessed in the brain.

Like many scientists in the field of memory, I used to think that a memory is something stored in the brain and then accessed when used. Then, in 2000, a researcher in my lab, Karim Nader, did an experiment that convinced me, and many others, that our usual way of thinking was wrong. In a nutshell, what Karim showed was that each time a memory is used, it has to be restored as a new memory in order to be accessible later. The old memory is either not there or is inaccessible. In short, your memory about something is only as good as your last memory about it. This is why people who witness crimes testify about what they read in the paper rather than what they witnessed. Research on this topic, called reconsolidation, has become the basis of a possible treatment for post-traumatic stress disorder, drug addiction, and any other disorder that is based on learning.

Tor Nørretranders now thinks that it’s more appropriate to think of your body as software, rather than hardware.

What is constant in you is not material. An average person takes in 1.5 ton of matter every year as food, drinks and oxygen. All this matter has to learn to be you. Every year. New atoms will have to learn to remember your childhood.

Helen Fischer now believes that human beings are serial monogamists.

Perhaps human parental bonds originally evolved to last only long enough to raise a single child through infancy, about four years, unless a second infant was conceived. By age five, a youngster could be reared by mother and a host of relatives. Equally important, both parents could choose a new partner and bear more varied young.

Paul Steinhardt is now skeptical about inflation.

Most cosmologists would say the answer is “inflation,” and, until recently, I would have been among them. But “facts have changed my mind” — and I now feel compelled to seek a new explanation that may or may not incorporate inflation.

John Baez is no longer enthusiastic about working on quantum gravity.

Jaron Lanier put it this way: “One gets the impression that some physicists have gone for so long without any experimental data that might resolve the quantum-gravity debates that they are going a little crazy.” But even more depressing was that as this debate raged on, cosmologists were making wonderful discoveries left and right, getting precise data about dark energy, dark matter and inflation. None of this data could resolve the string-loop war! Why? Because neither of the contending theories could make predictions about the numbers the cosmologists were measuring! Both theories were too flexible.

Xeni Jardin is depressed by the lack of spontaneous self-moderation in online communities…

But then, the audience grew. Fast. And with that, grew the number of antisocial actors, “drive-by trolls,” people for whom dialogue wasn’t the point. It doesn’t take many of them to ruin the experience for much larger numbers of participants acting in good faith.

…but Kevin Kelly is impressed by the success of Wikipedia.

How wrong I was. The success of the Wikipedia keeps surpassing my expectations. Despite the flaws of human nature, it keeps getting better. Both the weakness and virtues of individuals are transformed into common wealth, with a minimum of rules and elites. It turns out that with the right tools it is easier to restore damage text (the revert function on Wikipedia) than to create damage text (vandalism) in the first place, and so the good enough article prospers and continues. With the right tools, it turns out the collaborative community can outpace the same number of ambitious individuals competing.

Oliver Morton has changed his mind about human spaceflight.

I have, falteringly and with various intermediary about-faces and caveats, changed my mind about human spaceflight. I am of the generation to have had its childhood imagination stoked by the sight of Apollo missions on the television — I can’t put hand on heart and say I remember the Eagle landing, but I remember the sights of the moon relayed to our homes. I was fascinated by space and only through that, by way of the science fiction that a fascination with space inexorably led to, by science. And astronauts were what space was about.

Jonathan Haidt no longer believes that sports and fraternities are entirely bad. (This is my favorite.)

I was born without the neural cluster that makes boys find pleasure in moving balls and pucks around through space, and in talking endlessly about men who get paid to do such things. I always knew I could never join a fraternity or the military because I wouldn’t be able to fake the sports talk. By the time I became a professor I had developed the contempt that I think is widespread in academe for any institution that brings young men together to do groupish things. Primitive tribalism, I thought. Initiation rites, alcohol, sports, sexism, and baseball caps turn decent boys into knuckleheads. I’d have gladly voted to ban fraternities, ROTC, and most sports teams from my university.

I came to realize that being a successful scientific heretic is harder than it looks.

Growing up as a young proto-scientist, I was always strongly anti-establishmentarian, looking forward to overthrowing the System as our generation’s new Galileo. Now I spend a substantial fraction of my time explaining and defending the status quo to outsiders. It’s very depressing.

Stanislas Deheane now thinks there may be a unified theory of how the brain works.

Although a large extent of my work is dedicated to modelling the brain, I always thought that this enterprise would remain rather limited in scope. Unlike physics, neuroscience would never create a single, major, simple yet encompassing theory of how the brain works. There would be never be a single “Schrödinger’s equation for the brain”…

Well, I wouldn’t claim that anyone has achieved that yet… but I have changed my mind about the very possibility that such a law might exist.

Brian Eno’s disillusionment with Maoism changed his views on how politics can be transformative.

And then, bit by bit, I started to find out what had actually happened, what Maoism meant. I resisted for a while, but I had to admit it: I’d been willingly propagandised, just like Shaw and Mitford and d’Annunzio and countless others. I’d allowed my prejudices to dominate my reason. Those professors working in the countryside were being bludgeoned and humiliated. Those designers were put in the steel-foundries as ‘class enemies’ — for the workers to vent their frustrations upon. I started to realise what a monstrosity Maoism had been, and that it had failed in every sense.

Anton Zeilinger now believes that you should never describe your own research as “useless.” (Hmmm…)

When journalists asked me about 20 years ago what the use of my research is, I proudly told them that it has no use whatsoever. I saw an analog to the usefulness of astronomy or of a Beethoven symphony. We don’t do these things, I said, for their use, we do them because they are part of what it means to be human. In the same way, I said, we do basic science, in my case experiments on the foundations of quantum physics. it is part of being human to be curious, to want to know more about the world. There are always some of us who are just curious and they follow their nose and investigate with no idea in mind what it might be useful for.

Martin Rees thinks we need to take the “Posthuman Era” seriously.

Public discourse on very long-term planning is riddled with inconsistencies. Mostly we discount the future very heavily — investment decisions are expected to pay off within a decade or two. But when we do look further ahead — in discussions of energy policy, global warming and so forth — we underestimate the possible pace of transformational change. In particular, we need to keep our minds open — or at least ajar — to the possibility that humans themselves could change drastically within a few centuries.

It might sound a little crazy, but betting against Sir Martin is a bad idea.

What Have You Changed Your Mind About? Read More »

66 Comments
Scroll to Top