Turtles and Strings: Where Does Science Stop?

The infamous Davies op-ed has been collected together with some responses at edge.org, and one of the responses is by Sean Carroll, who reproduces his response at Cosmic Variance. Sean's a smart guy, and I basically agree with his argument, but I'm a contrary sort, and want to nitpick one thing about his response.

He builds his response around the question, raised by Davies, "Why do the laws of physics take the form they do?" He considers and discards a few responses, before writing:

The final possibility, which seems to be the right one, is: that's just how things are. There is a chain of explanations concerning things that happen in the universe, which ultimately reaches to the fundamental laws of nature and stops.

That's fine, as far as it goes. My nit-pick is that this isn't helpful. More importantly, it's not even consistent with other things that Sean has written in the past.

Way, way back in 2005, Sean wrote a passionate argument for string theory, which starts off with:

String theory, with all of its difficulties, is by far the most promising route to one of the most long-lasting and ambitious goals of natural science: a complete understanding of the microscopic laws of nature. In particular, it is by far the most promising way to reconcile gravity and quantum mechanics, the most important unsolved problem in fundamental physics.

He's made essentially the same argument many times since. We need string theory, he argues (as do many others), because general relativity and quantum mechanics do not play well together. They work on completely different theoretical bases, and string theory may be the best hope of bringing them together into a single theoretical framework.

My question is, if "that's just the way it is" is sufficient to cut off inquiry into fundamental questions of natural law before the level where Davies wants to operate, why isn't it also sufficient to cut off inquiry before you get to string theory? Why do general relativity and quantum mechanics have such different bases? That's just the way it is. Drive home safely.

Sean's response is very well-written, and presented with great conviction. It is not, however, a useful principle for deciding what questions are open to scientific inquiry. Unless I missed a memo over the holiday weekend, and Sean is now the ultimate arbiter of what is and is not science (and wouldn't that make Peter Woit and Lubos Motl both froth at the mouth...).

If we're going to say that there are certain questions about which science can't say anything meaningful, and thus head off Paul Davies's arguments about emergent natural laws and consciousness, we need some more useful way to make a determination of what science can and can't talk about. I wish I had one to offer, but I'm not even willing to offer myself in Sean's place as the Ultimate Arbiter-- I have a book to write.

A tentative step in the right general direction might be to say that for something to be a legitimate subject of scientific inquiry, there has to be a model (or set of models) that makes some useful prediction of observable phenomena from the theory. If there's no conceivable way to distinguish between models, then it's not really a scientific subject, and it's ok to stick with "that's just how things are," at least until somebody comes up with a model predicting observable phenomena.

That way lies the swamp of "Is string theory really science?," though, so maybe we're better off with letting Sean decide, after all.

More like this

I woke up yesterday, made myself a cup of coffee and sat down with the New York Times, and a left over piece of corn bread from Thanksgiving. It was a beautiful morning and I was at peace. Then I read this (I will try to be polite) by Paul Davies. Apparently scientists operate on faith. Faith that…
There's a piece by Michael Dine in Physics Today this month with the ambitious title "String theory in the era of the Large Hadron Collider, thus combining two of my very favorite topics... I was going to give it a pass, but I was surprised to discover that it's freely available-- most of their…
Paul Davies essay in the New York Times on "Taking Science on Faith" is sure to raise some hackles from the science community. Me, I'd just like to point out how silly some of Davies arguments specifics are. Yes, its another edition of "Nitpickers Paradiso." Davies begins with a mantra yelled by…
"You build on failure. You use it as a stepping stone. Close the door on the past. You don't try to forget the mistakes, but you don't dwell on it. You don't let it have any of your energy, or any of your time, or any of your space." -Johnny Cash This past week at Starts With A Bang saw quite a lot…

I didn't get that at all.

From what Sean wrote, I got the message that we shouldn't dictate the requirement for something to be explained before we have a reason to believe it can be. Doesn't mean we shouldn't search for explanations, but we shouldn't assume that every possible question has an answer.

Using string theory, we have a definite question - are general relativity and quantum mechanics just aproximations to a deeper theory? We have reasons to believe those two theories are only aproximations to something. We also have a rough outline of what such a unified theory would look like. We should run with that and find out if that answer actually materialises.

However, when we get to deep enough questions, we have absolutely no way of knowing whether such a question even could have an answer or not. The question "Why do the laws of physics take the form they do?" might not even make any sense once we understand what those laws are, assuming such laws exist even. Contained within the question is an assumption that we will, even must be able to understand or know the origins of those laws. An assumption that comes from philosophical errors made by Davies.

By Paul Schofield (not verified) on 26 Nov 2007 #permalink

I don't think I get it either. General relativity and quantum mechanics are mutually incompatible, so they can't both be right. But most scientists operate under the assumption that there is a set of laws that is consistent and correct, although we haven't found them yet. My point was that this ultimate set of laws is likely to be fundamentally contingent, not derivable from anything within itself, whatever that might possibly mean. Not sure how this makes me the arbiter of anything.

How does string theory differ from the biggest hit, 50 points for #37?

Both GR and QFT are wrong as Newton and Euclid were wrong. They are restricted subsets of a more inclusive whole. (Thurston did a 3-D gotcha! on Euclid, Riemann, Bolyai, and Lobechevsky all.) You have postulated something simplifying to be true that isn't true at all - but its divergence is empirically invisible to date.

Christmas 2007 Uncle Al's folks will look at the center of the block where the light is dim but the dollar was dropped. The rest of you will continue searching at the corner under the streetlight. We'll see who goes for ice cream afterward, if anybody.

I'm siding with Sean here. If the physics is consistent than both GR and quantum mechanics can't be right. They must both derive as approximations of something else (maybe string theory, maybe not) which is consistent. The apparent inconsistency is resolved since they are never simultaneously valid approximations. Now the theory that GR and QM derive from doesn't need a further explanation; it could just be a "that's how it is".

If physics isn't ultimately consistent, then I'm not sure how science doesn't lapse into complete solipsism. Then again, that could just be "how it is".

The question "where do the natural laws come from" is not unscientific - though it is being asked too early. But from the experience it seems more productive to look for a non-mystical explanation of things.

I think Davies is trying to make a controversial argument but he does not appreciate how the discovery process really works. There has been lots of hype about esoteric proposals in cosmology and theoretical physics - and maybe from there Davies got the fuzzy idea that our explanations depend on postulates analogous to the church articles of faith.

I think milkshake is on to something. It probably doesn't make sense to ask where the laws of physics come from until we know what they are. I suspect that will give us some breathing room.

The question "where do the natural laws come from" is not unscientific - though it is being asked too early.

Depends on what you mean by "the natural laws". If you're referring to things like quantum chromodynamics, then sure, those laws may one day be explained by science. But the explanation is liable to be in the form of more fundamental laws, which in their turn will call for explanation. If you're referring to natural laws of the universe in the abstract, the only answer science will be able to provide will be in terms of more fundamental laws, of, say, "the" multiverse. And if you're referring to natural laws in the full generality of the term, then no, I don't think science can provide an answer other than the tautological one.

By Andrew Wade (not verified) on 27 Nov 2007 #permalink

*sigh* My initial suspicion from many years ago is manifested in the responses to this blog entry: Atheists will go to any length to avoid accepting a contingent, created universe.

By J. Snavely (not verified) on 09 Dec 2007 #permalink

Atheists will go to any length to avoid accepting a contingent, created universe.

It's called 'Occam's Razor', Snavely. And extra-universal entities are always unnecessary.

By Caledonian (not verified) on 09 Dec 2007 #permalink

*sigh* My initial suspicion from many years ago is manifested in the responses to this blog entry: Atheists will go to any length to avoid accepting a contingent, created universe.

I for one am perfectly happy to accept a contingent, created universe once a good theory of that creation comes along. So far such theories have been lacking. You're not upset we're disregarding the weird and wacky scenarios string theorist have come up with for the creation of the universe, you're upset we're rejecting your particular "Godditit" theory. Tough: you have no cause to complain until your theory starts putting out more in terms of empirical predictions than is put into it in terms of ad-hoc hypotheses and parameter tuning.

By Andrew Wade (not verified) on 13 Dec 2007 #permalink