xkcd

I’ve linked to the webcomic xkcd.com in passing before, but it’s so full of science-geeky awesomeness that I thought I’d advertise it more explicitly, in case there’s anyone out there who would like it but doesn’t know about it.  Here are a couple of examples; if you like them, go there and waste an hour or two clicking “Random.”

Oh, and be sure to mouse over each comic.  There’s some extra text for each one, and often it’s the best part.  (The ones embedded in this post don’t have the extra bits; go to the web site to see them.)

brontosaurus.png

beliefs.jpg

And the geekiest for last:

kepler.jpg

Will we find extraterrestrial life?

My friend Tim asked me this question:

What do you think are the chances that we’ll detect (not necessarily physically encounter, but detect) life on another planet by the end of the century?

I think the odds are quite good, actually.

First, here’s something that I’m pretty confident is true: Within a few decades, we will have figured out how to measure the chemical composition of the atmospheres of other planets.  We’re moving fast in that direction right now, and while it’s a hard technical problem, I don’t see any show-stopping reasons why we can’t do it.  Basically, you have to have telescopes with sharp enough resolution to see the planet separately from its star, and then you just do spectroscopy.

I’ll be very surprised if we haven’t done this to hundreds and hundreds of planets within the next few decades.  We’ll know what molecules are in the atmospheres of those planets.  That means that we’ll detect life if a couple of conditions are satisfied:

  1. Extraterrestrial life is not very rare.
  2. Extraterrestrial life leaves identifiable chemical signatures in the atmospheres of host planets.

That’s as much as I can say with confidence.  From here on it’s guesswork.  Regarding #2, one important question is what would count as an identifiable signature.  People will naturally look at first for the chemicals that we find in our own atmosphere but that would not be there if there weren’t life.  I think that plain old oxygen (O2) is one of the main ones here: the oxygen would all be in other forms such as CO2 if it weren’t constantly replenished by biological processes.  I have no idea whether extraterrestrial life will be based on similar chemistry to ours, so maybe O2 won’t be the signature we’ll see.  But it does seem likely to me that, if a planet has life on it, there’ll be molecules in its atmosphere that you wouldn’t expect to see in a dead planet, and once we get good at doing spectroscopy, we’ll find them if they’re there.  So I’m not too worried about #2.

#1 is the one nobody knows about.  Is extraterrestrial life found on lots of planets, or is it a one-in-a-trillion shot?  Here, you just have to make your best guess.  Personally, I don’t think it’s likely to be incredibly rare, so once we’re mass-producing spectroscopy of other planets, we’ve got a good shot at finding it.  But that claim is based on no data — it’s a Bayesian prior probability — so feel free to disbelieve me.

I think this life is far more likely to be simple microbes than big intelligent things.  I doubt we’ll be hearing messages from ET any time soon.  That doesn’t mean that I think searches for intelligent life like SETI are a bad idea, though: they’re quite cheap compared to lots of scientific research, and the payoff if they succeed is so huge that I think it’s worth throwing a little bit of resources their way, despite the long odds.

Bragging

My colleague Jerry Gilfoyle and I were just awarded an NSF grant to buy a new computing cluster.  In the past, my students and I have mostly worked on problems that could be attacked with ordinary desktop computers.  This grant means that we’ll be able to go after more computationally intensive problems.  It also means I’ll have to learn about supercomputing techniques.  Fortunately, Jerry’s very experienced at this.

This has been a good funding year for me: I submitted three NSF proposals, and all three were funded. That’s at least partly due to the federal stimulus bill: only one of the three is officially stimulus money, but no doubt all the stimulus money washing around freed up more non-stimulus money for other grants.

Correction: Actually, two out of the three, including the computing cluster, are stimulus funds.  I’m nothing if not shovel-ready.

Whither human space flight?

The Augustine panel, the blue-ribbon (whatever that means) commission charged with assessing options for the future of human space exploration in the US, released the executive summary of its report today.  (The full report is coming soon.) So what did it say?  Here’s what the first two hits on Google News say.

First sentences of the Washington Post piece:

Don’t try to put astronauts on Mars yet — too hard, too costly. Go to the moon — maybe.

Headline of the Reuters piece:

NASA strategy proposal aims for Mars over moon.

So who’s right?  The Post is closer than Reuters. The summary lays out three possible strategies, which they call “Mars first,” “Moon first,” and “flexible path.”  The last one involves starting with “inner system locations such as lunar orbit, Lagrange points, near-Earth objects and the moons of Mars.” After describing all three options, “the Committee finds that both Moon First and Flexible Path are viable exploration strategies.” (I’ve argued before that the Flexible Path combines all the disadvantages of human spaceflight with none of the advantages.)

But the real takeaway from the summary, it seems to me, is not these three paths; it’s this:

Human exploration beyond low-Earth orbit is not viable onder the FY 2010 budget guideline.

That is, we either need to spend substantially more money or decide that human space exploration isn’t a priority at the moment.  This sounds right to me.

A few miscellaneous observations:

1. Early on, the summary says something that should be obvious but often seems not to be:

Planning for a human spaceflight program should begin with a choice about its goals — rather than a choice of possible destinations.

I’m really glad to hear them say this: I’m sick of people saying “we need to go to Mars” without saying why.  I don’t think that the rest of the summary always lives up to this laudable goal, but maybe I’m not being fair to the panel: the full report may do better.

2. The summary recommends keeping the international space station going for another five years (to 2020 instead of 2015 as currently scheduled).

It seems unwise to de-orbit the Station after 25 years of assembly and only five years of operational life.

This is true, if the Station is actually useful, a claim that has not been demonstrated to my satisfaction.  Otherwise, the 25 years is a sunk cost, and extending the operational life is throwing good money after bad.

3. The panel has good things to say about the idea of contracting out some of our space flight to the commercial sector:

As we move from the complex, reusable Shuttle back to a simpler, smaller capsule, it is an appropriate time to consider turning this transport service over to the commercial sector.

…

In the 1920s, the federal government awarded a series of guaranteed contracts for carrying airmail, stimulating the growth of the airline industry.  The Committee concludes that an architecture for exploration employing a similar policy of guaranteed contracts has the potential to stimulate a vigorous and competitive commercial space industry.

…

This would have the benefit of focusing NASA on a more challenging role, permitting it to concentrate its efforts where its inherent capability resides: for example, developing cutting-edge technologies and concepts, and defining programs and overseeing the development and operation of exploration systems, particularly those beyond low-Earth orbit.

I think this approach is well worth considering.

Want to be a lawyer? Study physics.

Well, maybe.  I learned via Sean Carroll about a study showing that physics and math majors get better LSAT scores than people who study any other subject.  The top 5 disciplines, with mean LSAT scores:

  1. Physics/Math (160.0)
  2. Economics (157.4)
  3. Philosophy/Theology (157.4)
  4. International Relations (156.5)
  5. Engineering (156.2)

In some cases, disciplines with smaller numbers of students were lumped together, so Physics/Math were treated as one category.  Pre-law ranked 28th out of 29, with an average score of 148.3.

It’s tempting for us physicists to use this as propaganda to convince people that studying physics is good preparation for a variety of careers, including law.  Although I suspect that that proposition is true, this study probably doesn’t provide strong evidence for it, for the usual correlation-is-not-causation reasons.  Students may self-select into physics and math based on qualities that correlate with doing well on the LSAT, but that doesn’t mean that a given student would do better on the LSAT if she studied physics as opposed to something else.

Still, it’s always nice to have bragging rights over other disciplines.

The fact that pre-law ranks near the bottom sounds embarrassing, but I suspect there’s not too much significance to it.  Pre-law is a funny category: at many institutions (including, I think, every one I’ve ever taught at or attended), pre-law isn’t a major: a pre-law student majors in something else.  So I’ll speculate that the students counted as pre-law in this study are a non-representative sample: they come from a different (and plausibly biased in various ways) subset of universities than the others.

One last thing.  Sean observes

The obvious explanation: physics and math students get to be really good at taking tests like the LSAT. I don't imagine this correlates very strongly with "being a good lawyer." Then again, I don't think that good scores on the physics GRE correlate very strongly with "being a good physicist," over and above a certain useful aptitude at being quick-minded.

Regarding the physics GRE, I seem to recall some actual data showing that scores correlate extremely poorly with a variety of measures of success in and after graduate school, but I can’t seem to find it, so maybe I hallucinated it.  If anyone remembers what I’m thinking of and can point me to a citation, I’d appreciate it.

Robert Wright on God and Darwin

It’s probably a mistake to wade into such a controversial topic, but anyway, here are some thoughts on Robert Wright’s Op-Ed in Sunday’s NY Times.  Wright’s clearly a thoughtful guy who knows about both science and theology.  I haven’t read his book, but I have read a number of reviews of it, heard interviews with him, and read his guest blog posts on Andrew Sullivan. He seems to be someone worth paying attention to. But …

The  headline of the piece is “A Grand Bargain Over Evolution.” The goal seems to be to lay out a stance that will turn down the heat in the evolution wars and help everyone to get along.  An excerpt:

The first step toward this more modern theology is for them [religious believers who have problems with Darwinian evolution] to bite the bullet and accept that God did his work remotely €” that his role in the creative process ended when he unleashed the algorithm of natural selection (whether by dropping it into the primordial ooze or writing its eventual emergence into the initial conditions of the universe or whatever).

Essentially, he’s proposing Deism, justified by a sort of God-of-the-gaps approach.  I’m sure he would say that’s an oversimplification.  Read his piece for yourself and see whether you think I’ve characterized it fairly.

I have two thoughts on this attitude (neither original, I’m sure, given the vast amount that’s been written on these subjects):

  1. If presented with such a bargain, I would strongly urge my fellow scientists to accept it.  By this I mean not that you have to believe in it: go ahead and be a hard-core atheistic materialist if you want.  But don’t put any significant effort into convincing Deists that they’re wrong.  They’re not doing science any significant harm, and if you try to persuade people like this that believing in science means giving up all notions of religion, you’re going to do far more harm by hardening them against your point of view.
  2. But this thought experiment is completely irrelevant to the battle as it’s being fought in the US.  The forces of good (i.e., science) in this battle are not confronting Deists.  If you think that the defendants in the Dover case, or the anti-evolution folks running for school boards around the country, are anywhere near being persuaded of Wright’s Deism, you just haven’t been paying attention. Try telling any of the anti-evolution activists that God’s “role in the creative process” of human development ended 14 billion years ago if you don’t believe me.

Science and human space flight

President Obama’s commission to examine possible options for the future of human space flight is getting ready to issue its final report.  They are apparently discussing seven different possible options, some that involve going to Mars, and some that don’t.  There was an interesting report in Nature last week about a recent public meeting held to discuss the various options. (Thanks to my brother Andy for pointing this out.)

Of course, I’m most interested in the implications for science, so this caught my eye:

The panel plans to cost out the scenarios by next week, and also to assess the benefits of each for 12 key areas.

One of those areas is the potential to gain scientific knowledge from each strategy, says panel member and astrophysicist Christopher Chyba, of Princeton University in New Jersey.

To that end, yesterday’s meeting was mostly devoted to presentations from scientists representing four communities supported by NASA: Earth sciences, space-borne biological and physical science, astrophysics and planetary science.

So what did the scientists have to say? Well, according to Nature one of them didn’t have much of a case to make:

Anthony Janetos, representing Earth sciences, was hard-pressed to find an example. The director of the Joint Global Change Research Institute in College Park, Maryland, Janetos hedged when panel member and former astronaut Leroy Chiao asked if the thousands of pictures he took during shuttle flights were really all that useful. Janetos said they were “marginally” useful.

The others seem to have more sanguine views of the potential for getting science from human space flight.  The astronomer Marcia Rieke naturally and correctly pointed to the Hubble Space Telescope, which has been incredibly productive and has always depended on humans in space for support.  Planetary scientist Steven Squyres says there’d be a big scientific payoff from sending humans to Mars, comparing a human mission to the Spirit and Opportunity rovers:

He said that astronauts on Mars could do in a minute what his rovers averaged in a day, and pointed out that Spirit and Opportunity had covered less ground during their entire mission than Apollo astronauts in a lunar rover were able to travel in a day.

Of course, the fair comparison is between what humans could do and what a robotic mission could do if it had the same budget as a human mission (i.e., thousands of times what was spent on Spirit and Opportunity).  I doubt very much that the humans would win out in that comparison.

I doubt that you can ever justify sending humans into space on scientific grounds.  But that’s not and never has been the reason we send humans into space.  If we send humans to Mars, it’ll be for the intrinsic awesomeness of the achievement.  Personally, I don’t think that awesomeness is worth the price at the moment.  I think if we’re going to spend upwards of $1011 on engineering and R&D, it should be on a massive investment in energy technology for Earth.  If we do send humans to Mars, of course, I reserve the right to think it’s awesome and to be excited about it.

By the way, one of the Augustine panel’s seven options is particularly baffling to me:  “what the members called the "flexible path," which would avoid the "deep gravity wells" of the Moon and Mars, saving the time and cost of developing landers to carry astronauts to the surfaces of those bodies.”

A flyby of the moon might be followed by more distant trips to so-called Lagrange points, first to the location where the gravity of the Moon and the Earth gravity cancel each other out, then to where the gravity of the Earth and Sun cancel out. There could also be visits to asteroids or flybys of Mars leading to landings on one or both of the low-gravity moons of Deimos and Phobos.

This seems to me to have most of the disadvantages of human space flight but to cut way, way back on the advantages, i.e., both the scientific payoff and the intrinsic awesomeness.

Rejecta Mathematica

A new online journal that publishes only articles rejected by peer-reviewed journals. (HT: Freakonomics, which got it from the Economist.)

The obvious question is what’s the point of such a thing.  The editors address this in a letter accompanying the first issue, making a number of valid points: Good research is sometimes wrongly rejected.  Moreover, there’s value in publishing even results that turn out to be dead ends, if only to prevent other people from wandering down the same dead ends.  But here’s where they fail to convince me:

While such a project as Rejecta Mathematica would have been impracticable in the pre-internet age, the flood of resources available today begs another oft-posed question: "Why do we need a new journal? Isn't this what a preprint server (like the arXiv), a blog, or a personal website is for?"

My usage-pedant hackles get raised at the misuse of “beg the question,” but that’s not really the point.  Mostly, I just don’t think they have a good answer to this question.  This journal would solve some of the problems the editors have identified, if the right people would read it.  But I don’t see how that’s ever going to happen.  In particular, an author who wants to get people to notice his rejected paper can and should put it on the arXiv, which will be a much more effective strategy than publishing it here.  [Note:The arXiv does require an “endorsement,” but frankly, the bar there is set pretty low, and if you can’t get someone to endorse your paper, that’s a pretty solid indication that you need to fix either the work or your communication skills.]

Still, Rejecta Mathematica is an interesting experiment, and I hope it does prove useful to some people.  The editors did get one thing exactly right: along with each article, the authors must supply an open letter explaining the rejection history of the article.  These letters are extremely revealing: some contain reasoned discussion, while others are frankly rants.  If I were to look at this journal regularly, that would be my main guide as to which articles were worth a closer look.