Thursday, April 29, 2010

Controllably Morphable

We occasionally joke about the looming robot menace, but seriously. Discoblog has picked out the Niftiest Robots of 2009, but “Scariest” would have been an equally appropriate appellation.

Yes, there is a robot that crawls around inside your colon, not to mention a Japanese emobot, but the one I would least like to meet in a dark alley is Chembot. It’s a blob-shaped thing that uses jamming in granular materials to make a robot that can alter its shape.

Still pretty primitive, but you can see where we’re headed here. Don’t say we didn’t warn you.

This Week on ?In Retrospect, Not the Best Comparison?

Here are the opening sentences of Chapter Five of my book:

When most people hear ?scientist,? they think ?Einstein.? Albert Einstein is an iconic figure; not many theoretical physicists attain a level of celebrity where their likeness appears regularly on T-shirts. But it?s an intimidating, distant celebrity. Unlike, say, Tiger Woods, the precise achievements that Einstein is actually famous for remain somewhat mysterious to many people who would easily recognize his name.

And now we can add, “and some achievements should really stay mysterious, thanks just the same.”

Tuesday, March 30, 2010

Who Are You?

Last week I Twittered/Facebooked some provocative results from a poll of philosophers. In particular, this little tidbit:


Teletransporter (new matter): survival or death?













Accept or lean toward: survival337 / 931 (36.1%)
Other304 / 931 (32.6%)
Accept or lean toward: death290 / 931 (31.1%)


Yes, that’s all the detail presented in the question: “Teletransporter (new matter): survival or death?” As a professional philosopher, you’re supposed to be familiar with the issue, which I reconstruct as follows. Imagine that someone has invented a working teleportation device. You step in the box, lights flash and sparks fly, and “you” rematerialize in another box, exactly the same in every way, but constructed out of a completely new collection of atoms. The original version of you is destroyed. Did you die? (And then, what if a million years passed in between the two events?)


It would probably be annoying to real philosophers, but I personally put this question in the category of “Not that hard.” And I would phrase my answer as: “Who cares?” What we should care about is how well the teleporter actually works — is the reconstructed person really in exactly the same quantum state as the original one was in? Same memories, feelings, etc? That’s an interesting technology question.


But there’s no interesting question associated with “Did you really die when you were teleported?”, or “Are you really the same person after being teleported?” These are just bad questions. They assume a certain way of looking at the world that ceases to be useful once we’ve invented teleportation. Namely, they assume that there’s a certain “essence of you-ness” that is (somehow) associated with your physical body and continues through time. That’s a perfectly sensible way of talking in the real world, where we don’t have access to duplicator devices or transporter machines. But if we did, that conception would no longer be very useful. There is a person who stepped into the first box, and a person who stepped out of the second box, and obviously they have a lot in common. But to sit down and demand that we decide whether they are “really” the same person is just a waste of time — there is no such “really.”


Which isn’t to say there aren’t interesting questions along these lines, but they are operational questions — how should I actually act, or what should I actually expect to happen, in these situations? — rather than arid metaphysical ones. What if you murdered someone, and then teleported — would the reconstructed person still be guilty of murder? That’s not quite the right question, because it still relies on the slippery essence of continuous personhood, but there’s a closely related sensible question — should we treat the reconstructed person as if they had committed murder? And it seems to me that the answer is clearly “yes” — whatever good reasons we had for treating the pre-teleportation person in a certain way, those reasons should still apply to the post-teleportation person.


The issue of duplication seems much thornier to me than the issue of teleportation. If someone made an exact copy of a known murderer, should we treat both the original and the copy as murderers? (I vote “yes.”) Fine, but what about the view from the inside? Let’s say you have an offer to get paid $100 if you let yourself be copied, with the proviso that after being copied one of the two of you will randomly be chosen for immediate painless execution. Do you take that deal?


I think problems like that are legitimately interesting, although to a great extent their mystery relies on the inadequacy of our conceptions of death. Most of us don’t want to die, at least not right away. But if we did die, we’d be gone, and wouldn’t have any wants or desires any more — but it’s very hard to consistently reason that way. Note that if we replaced “immediate painless execution” with “prolonged torture,” it seems like a much more straightforward question.


This showed up in our long-ago discussion of the quantum suicide experiment. In the many-worlds interpretation of quantum mechanics, you can make measurements that split the wave function of the universe into distinct branches. In some sense, then, you really do have a duplicator machine — it’s just that the whole universe gets duplicated, not just you. Some folks have tried to argue against this idea by pushing adherents into a logical cul de sac. You shouldn’t (to make a long story short) be averse to bargains that leave you dead with large probability, as long as there exist branches of the wave function where you are alive and flourishing — after all, in the branches where you are dead you don’t care any more, right?


My point in that earlier post — a point I somehow managed to completely obscure — was that these are misleading thought experiments, because very few of us would take seriously the corresponding classical suicide experiment. “Here, I’ll flip a coin, and give you $100 if it’s heads and shoot you instantly dead if it’s tails. Deal?” Very little temptation to take that offer. But the logic is essentially the same — if you’re dead you don’t care, right? (For purposes of these thought experiments we always assume you have no friends or loved ones who would miss you; it’s just part of the philosophical game, not a comment on your actual social situation.)


At some point in thinking about the many-worlds interpretation, issues like this inevitably do come up. That’s what David Albert and I talked about a bit on Bloggingheads. There might be a certain measurement that yields result A 10% of the time, and result B 90% of the time. But in the MWI, the measurement splits the universe into two branches, and you end up either in the branch where you saw A or the branch where you saw B. What does it mean to say that you had a “10% chance of measuring A”? You either did or you didn’t — there is no ensemble of millions of you all doing the same experiment. People have made progress on these questions — here’s a talk by David Wallace on his work with David Deutsch in attacking this problem. (Don’t ask me why everyone who thinks about these issues is named “David.”) I haven’t ever looked at this work closely enough to have an informed opinion.


All I know is that being able to teleport around would be really cool.

Water water everywhere

Northern New Mexico is an absolutely fabulous place to live. But, on occasion, I wish I had a teleporter handy. One of those occasions would be when the “Swell of the Century” hits the Hawaiian Islands, as it did last week. It turned out to be more like the “Swell of the Decade”, but apparently was nonetheless quite spectacular. Spectacular enough to hold the Eddie, a big-wave contest that can only be held in epic conditions.

surf_drop

There’s some good video here and here. Conditions were apparently squirrely, so most of the footage consists of fairly spectacular drops leading to gnarly wipeouts. Every now and then someone (often Kelly Slater [at left above]) emerges intact. Unless you’ve been out in overhead+ surf, I think it’s hard to fathom just how powerful these waves can be. You’ve bodysurfed three footers, and you think you have a clue. But you don’t. For a little perspective, here’s an excellent video from a (professional) surfer who wiped out at Jaws (on the north shore of Maui; it only fires on big days [like last week]). He survived (more-or-less).


While Hawaii was being slammed by water horizontally, we got a vertical contribution (in the form of a couple of feet of snow). It’s time to go dust off my snowboard.

Sunday, February 28, 2010

Data, Skepticism, Judgment

In one of the comments to Daniel’s post on the stolen climate emails, techskeptic points to a wonderful chart at Information is Beautiful. The author did a great deal of gruntwork to lay out the various arguments of “The Global Warming Skeptics” vs. “The Scientific Consensus.” As far as I can tell, it’s a legitimately balanced view of both sides, complete with citations. If you’re confused about the various issues and accusations being bandied back and forth, there are worse places to start. This is a small piece of the full chart.


climatecomparison


Of course, there is no such thing as a purely objective and judgment-free presentation of data, no matter how scrupulously the data itself may be collected; if nothing else, we make choices about what data to present. And a side-by-side comparison chart like this can’t help but give a slightly misleading impression of the relative merits of the arguments, by putting the conclusions of an overwhelming majority of honest scientists up against the arguments of a fringe collection of politically-motivated activists. But it’s certainly good to see the actual issues arrayed in point-counterpoint format.


Still, there remains a somewhat intractable problem: when people are arguing about issues that necessarily require expert knowledge that not everyone can possibly take the time to acquire for themselves, how do we make judgments about who to believe?


This problem has been brought home by the incredibly depressing news that James Randi has come out in favor of global-warming denialism (via PZ Myers). Randi is generally a hero among fans of reason and skepticism, so it’s especially embarrassing to see how incredibly weak his reasoning is here. It basically amounts to: “The climate is complicated. And scientists don’t know everything. And I admit I don’t know much about the field. Therefore … we have good reason to distrust the overwhelming majority of experts!” Why Randi chose not to apply his vaunted powers of skepticism to the motivations behind the denialists remains a mystery.


This gets to the heart of why I’ve always been skeptical of the valorization of “skepticism.” I don’t want to be skeptical for the sake of being skeptical — I want to be right. To maximize my chances of being right, I will try to collect what information I can and evaluate it rationally. But part of that information has to include the nature of the people making arguments on either side of a debate. If one side consists of scientists who have spent years trying to understand a complicated system, and the other is a ragtag collection of individuals with perfectly obvious vested interests in the outcome, it makes sense to evaluate their claims accordingly.


By all means, we should apply our own powers of reason to every interesting problem. But when our reasoning leads to some conclusion at odds with the apparent consensus of a lot of smart people who seem to know what they’re talking about — whether it’s on the nature of dark energy, the best way to quantize gravity, the most effective route to health care reform, or the state of the environment — the burden is on us to understand the nature of that difference and try to reconcile it, not to take refuge in “experts don’t know everything” and related anti-intellectual piffle.

And the Eagerly-Awaited Dark Matter Result Is?

… not yet released, but we’ll find out in just a bit. 2:00 p.m. Pacific time, to be exact.


Last week we mongered the rumor that the CDMS experiment was going to announce an exciting new result soon — and that time is now. (My guess remains: some interesting data that falls well short of “we’ve discovered dark matter!”) If you’d like to watch the talks online, here you go:



Further bulletins as events warrant.