The thermodynamic arrow
Both this video:
and this one are compatible with the fundamental laws of physics.
The question of why we can be certain that the first video is time-reverse is one of the deepest questions in foundations of physics.
Archive
You are currently browsing the (Pseudo-)Science Blog blog archives for July, 2013.
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“UFOs are Real”
"UFOs are real phenomena. They are artificial objects under intelligent control. They're definitely the craft of a supremely advanced technology," says physicist Eric Davis, a researcher of light-speed travel."
http://www.huffingtonpost.com/2013/07/20/physicist-eric-davis-mufon-symposium_n_3620126.html
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When is doubt reasonable?
An interesting perspective from the legal standpoint: http://www.bloomberg.com/news/2013-07-15/reasonable-doubt-is-central-to-zimmerman-verdict.html
Apparently the standard of reasonable doubt was first introduced to assuage jurors concerned with condemning innocent people.
Jul
16
Antipiphany and Socratic Humility
http://blogs.plos.org/citizensci/2013/07/15/that-moment-when-you-realize-how-little-you-actually-know/
It takes a fair bit of knowledge and intelligence to realize just how little you know. This is a common feature that one finds in people swept up by pseudoscience and denialism: they don’t know enough to realize that they don’t understand the science.
This is why, for example, it’s fairly common to see cranks challenging evolution by natural selection and Einstein’s theory of relativity. These are simple enough that people can think they get the argument (typically a nonrigorous popularization of the argument), and then when they don’t quite understand some important feature of it, they think they’ve found a flaw in modern biology or modern physics, rather than recognizing it as a flaw in their own understanding.
(And don't forget to discuss conservapedia on relativity at some point.)
Jul
15
Geocentrism in the 21st Century
Back in 2010, there was a conference that I dearly wanted to attend. In the back yard of Notre Dame (where I got my PhD), a bunch of Catholics were gathering to push back against the Copernican heliocentric model of the solar system, and to defend geocentrism -- that is, the view that the Earth is at the center of the universe.
It was supposed to be the first annual conference on the topic. I'm very disappointed that it apparently turned out to be the only "annual" meeting.
Now this is juicy bit of crack-pottery, but as is the case with most examples of pseudoscience, there is a germ of truth underlying their madness. In particular, we can't legitimately use modern science to say that Earth is not at the center of the universe, if by that we mean to imply that something else might be at that location. Scientists will typically say that this is because there is no "center of the universe", but one could instead say (without being completely wrong) that each location has an equal claim to be considered the "center". But obviously it would be misguided to suppose that this supports geocentrism.
I haven't taken the time to read through their arguments, but at a glance it seems that they have some people with some genuine scientific knowledge generating some of their arguments. And again, there are some germs of truth that could be extracted.
In particular, there is a way of reading Einstein's theory of general relativity (which tells us that gravity is really the curvature of spacetime) as saying that there are no objective facts of the matter about whether a particular object is moving or is stationary. Galileo and Newton had already established that constant motion in a straight line was physically the same as being at rest, but Einstein showed that (in a sense) this is also true of accelerated motion.
That is, Einstein's physics can be used even in systems that are changing their speed and/or direction. So a case could be made for saying that just as when two spacecraft approach one another there's no objective fact about which one is moving and which is standing still (each can legitimately say, "I'm standing still, and she's moving toward me), so too there's no objective fact about whether the Earth is at rest and the sun is moving around it, or whether the the Earth is in motion around a stationary sun.
But (at least) two points need to be made here:
(1) At best, this argument will establish that nothing is objectively in orbit around anything else -- it won't show that the Earth is in any way privileged (which is what geocentrism requires).
(2) The way that Einstein's general theory of relativity allows us to treat the Earth as stationary is that it allows us to treat the motions of everything else in the universe as being affected by a universal gravitational field that moves everything around. Geocentrism would require us to suppose that these fictitious gravitational forces are real, and this conclusion is quite absurd.