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August 5, 2011 9:20 AM   Subscribe

Old Theories As Limits of New Ones -- Theoretical physicist, Lubos Motl, takes a brief tour through the history of physics, and explains the simple mathematical relationship of old theories to the theories that replace them.
posted by empath (16 comments total) 11 users marked this as a favorite

If you define the universe as a zero-dimensional sphere of infinite size, then all theories about it are both true and untrue simultaneously.
posted by blue_beetle at 9:46 AM on August 5, 2011 [1 favorite]

LuboŇ° Motl is a total jerk.
posted by alby at 10:01 AM on August 5, 2011


(Not safe for people with eyes.)
posted by ZenMasterThis at 10:33 AM on August 5, 2011 [2 favorites]

I feel like I ought to support my assertion that Motl is a jerk so see here and here for examples.
posted by alby at 10:35 AM on August 5, 2011 [1 favorite]

Yeah, politically, he's an asshole, but that has nothing to do with this.
posted by empath at 11:16 AM on August 5, 2011

Although I don't know a lot about physics, my understanding is that Motl's ideas are often . . . controversial, to say the least. He is also, as alby points out, not just a jerk but actively dangerous to science.
posted by Frobenius Twist at 11:17 AM on August 5, 2011

Sigh. Could have been interesting if remarks here hadn't sensitized me to notice that he's claiming Galileo as a CWM (conservative white male), and thus less likely to be fooled by the climate change hoax. (Also, as a NoScript extension user, I have never seen a site pull in javascript from so many other different sites.)
posted by benito.strauss at 12:19 PM on August 5, 2011

Yeah, to be fair, the fact that he's an unpleasant person doesn't necessarily mean that this article is bad or wrong. He was, to be fair, employed for a time at Harvard. (Although he was also fired from Harvard for being an asshole).
posted by Frobenius Twist at 1:39 PM on August 5, 2011

posted by XMLicious at 2:09 PM on August 5, 2011

I had a really brilliant friend who became schizophrenic.

At some point early in the process, the scales fell from his eyes and very simple ideas were seen to explain all previously baffling complexities.

I can't really tell if this is happening to Motl, but the rants against his enemies linked by alby are anything but reassuring.
posted by jamjam at 3:26 PM on August 5, 2011

There's nothing schizophrenic about this. This is just standard dimensional analysis and physics.
posted by empath at 3:59 PM on August 5, 2011

Is this really standard dimensional analysis? In what sense did flat-earthers think the earth was a sphere of infinite radius, or Aristotle, in claiming that objects are naturally at rest, think that friction was infinite? This all sounds totally quackish to me. My suspicion is that this is someone good at a particular area of physics inappropriately applying his tools to develop a huge and all-encompassing theory of scientific progress and revolution.
posted by painquale at 4:20 PM on August 5, 2011

The idea isn't that Aristotle thought that friction was infinite. The idea is that if you want to refute Aristotle, and everyone accepts that Aristotle was right, you need to explain why he was wrong in a way that doesn't make him (and everyone else) look like a complete idiot. One way to do this is to show that there is this thing called friction, and if this friction-thing was limitless then it would explain Aristotle's conclusion. You then show that's it's not limitless, but that it can appear limitless under the conditions Aristotle studied. So you show that Aristotle was wrong, but was still a reasonable guy. Aristotle's theory is really just a special case of your theory.

This is an interesting way to look at the history of physics, but it's not at all how the people doing the history looked at it.
posted by wheloc at 9:26 PM on August 5, 2011 [1 favorite]

Is this really standard dimensional analysis? In what sense did flat-earthers think the earth was a sphere of infinite radius

They didn't. The point is that for the distances they were measuring, it didn't matter, because for all intents and purposes it was infinite, just like special relativity doesn't matter when the speed of light is effectively infinite.
posted by empath at 10:44 PM on August 5, 2011

In fact a big test of a new theory is proving that at certain limits, it reduces to the currently accepted theory. If it doesn't, then there's a big problem with your theory. Imagine if special relativity didn't reduce to Newtonian physics when the speed of light was effectively infinite? It would mean there was something incredibly wrong with the theory.
posted by empath at 10:48 PM on August 5, 2011 [1 favorite]

I'm not objecting to his treating old theories as special cases of new ones. It's his treating old theories as special cases that implicitly set a parameter to infinite or limitless. This is true of Newtonian physics --> relativistic physics, but he's overapplying the notion. Limitless friction means no force can move anything, not that things rest unless acted on by a force, right? And flat-earthers thought the earth had zero curvature because the earth has very low positive curvature. Saying that their theory was "a limit" that set the radius of the earth to infinite is true in no sense, unless you make the "for all intents and purposes" move empath did. But it's also true that "for all intents and purposes" we could have been living on the inside of a hollow earth with enormous radius" (i.e. one with low negative curvature). Motl should just say that they assumed curvature of the ground is zero. But because he's on an infinity kick and wants to find a value that can be infinite, he chose radius of the earth, ignoring that this dumps other theoretical commitments onto the previous theory (i.e. curvature is positive).

I guess he does just say "those parameters were undetermined and often considered zero or infinite in the older theories." But all his examples push on the idea that we previously were implicitly setting the value of variables to infinity, so it seemed he was building something stronger. If all he's saying is that old theories are sometimes special cases, then ok.
posted by painquale at 12:34 AM on August 6, 2011

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