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The last major prediction of Einstein's theory of General Relativity, gravitational waves, was the most controversial and difficult to verify of them all. It wasn't until 1993 that gravitational waves were indirectly observed in the behaviour of neutron star binaries, and not until 2015 that they were finally directly detected. Even Einstein himself for a time had doubts that they were real, and he even attempted to publish a paper that tried to argue that gravitational waves were a mere artefact of the mathematics, which turned out to be flawed. Oddly enough, it was Richard Feynman, who is much better known for his work on quantum electrodynamics, who came up with an argument that convinced many of the doubters. Rather than arguing the mathematical subtleties of relativity, he came up with a physical explanation that not only demonstrated that gravitational waves must carry energy, but later inspired the design of LIGO, the first apparatus that detected gravitational waves directly. Paul Halpern has an article where he tells the whole story. From the article:
Enter Richard Feynman, who had distaste for unnecessary abstraction. If gravitational radiation is real, it must convey energy. Rather than debating the technical question of whether or not the pseudotensor definition of gravitational energy was correct, he turned instead to a far more intuitive line of reasoning, what has come to be known as the "sticky bead argument."
In his thought experiment, Feynman imagined a thin stick on which one mass is fixed and a second mass, slightly separated from the first, is free to slide back and forth, like a curtain on a rod. These two masses would be analogous to a pair of charges embedded in a vertical receiving antenna used to pick up radio signals. Just as a pulse of electromagnetic radiation would cause such charges to oscillate, the same would happen in the "gravitational antenna" if a gravitational wave passed through—with the maximum effect occurring if the wave were transverse: at right angles to the stick. Upon the impact of a gravitational wave, one of the masses would accelerate relative to the other, sliding back and forth along the stick. The rubbing movement would generate friction between the free mass and the stick, releasing heat in the process. Therefore the gravitational radiation must convey energy. Otherwise, how else did the energy arise?
(Score: 0) by Anonymous Coward on Thursday March 09 2017, @08:06AM (2 children)
I think I agree with you, but I find your view unclear.
"intuition", in this context, is our ability to assign value to a mathematical statement before understanding all the details of the construction of that mathematical statement.
our brains have intuition for euclidian geometry and constant gravitational fields. we spent millions of years climbing trees, we spent hundreds of thousands of years throwing rocks and balancing ourselves on two legs, I find it very likely that some of the relevant physics is actually hard wired in our nervous system.
to be successful in classical physics, we just need to be able to properly associate the relevant math to this existing intuition.
however, we are also able to develop intuition about phenomena outside of regular human experience.
I was told explicitely that people who work on quantum physics experiments develop intuition about quantum physics after a reasonable amount of time.
also, when someone is working on quantum physics, they are using mathematical objects defined in different contexts, for which they probably already have an intuition (for instance complex numbers are quite natural for talking about plain old electricity, which again you can do in the lab).
I'm not sure my comment makes it clear enough, but I think it's different enough from yours to matter.
(Score: 0) by Anonymous Coward on Thursday March 09 2017, @02:15PM
The intuition that you describe goes back to the days of Euclid and was, in fact, so hard wired into our guts that we were locked into that mode of thinking and mathematics for a thousand years. Around Galileo's time people started trying to work in observations, but we were still locked into our intuitive view of the universe. It wasn't until people like Riemann said "Because we can't make a self-consistent geometry with only those five axioms, what happens if we take that troublesome one and consider what happens if parallel lines do intersect . . ."
(Score: 2) by Immerman on Thursday March 09 2017, @03:26PM
>"intuition", in this context, is our ability to assign value to a mathematical statement before understanding all the details of the construction of that mathematical statement.
I disagree. I would say intuition in this context is developing an understanding of the mechanisms in play, independent of the mathematics. A hunter doesn't need to understand the mathematics of the aerodynamic and gravitational influences on his arrow, he just needs to develop a reliable intuition of how he's required to aim to hit the desired target.
Similarly when solving a physics problem, well-developed intuition will let you know roughly where the solution lies and what it will look like before you've done any of the math. Mathematics is then the path taken to verify that you're actually correct, and get the precise details of the solution.
Now, knowing how to do the math reliably can be an valuable path to developing that intuition, to say nothing of pushing past it into the unknown. But a selection of good illustrative examples can also go a surprisingly long way toward developing that intuition, even without knowing any of the math.