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Does math always predict physics? Diracs equation predicted anti-matter and SU(3) symmetry additional baryons. Einsteins GR equation has oscillatory solutions.

Does math always predict physics? Diracs equation predicted anti-matter and SU(3) symmetry additional baryons. Einsteins GR equation has oscillatory solutions. But no experiment has seen gravity waves yet.

evanb 11y ago
* Maybe. http://www.skyandtelescope.com/astronomy-news/about-this-weeks-gravitational-wave-rumor/ http://www.skyandtelescope.com/astronomy-news/about-this-wee...
rotorblade 11y ago
Well, it is a good feature of a theory. Imagine that you would have two competing theories but they give different predictions, then a measurement on those predictions would determine which is which. (If they give the same predictions, an interesting questions would be 'is there a mathematical proof that they are the same?'.) For example with GR, it explained for example the precession of Mercury's elliptical orbit, and predicted time dilation (used now in GPS for example) and bending of light. It is true that gravity waves remains to be directly detected. This is how physics have usually progressed in the past: Have an old theory, have some experiments not explained by that theory, invent new theory that can be reduced to the old theory and explains these new experiments and give new predictions. (The subject of string theory is somewhat different however.)
marcosdumay 11y ago
We keep the math that predicts physics, and throw everything else away. So, it's too easy to assemble a small narrative of history that gives this impression, and forget every other model that people crated trying to get to those ones that hold.
cozzyd 11y ago
Even though (LIGO's rumored result notwithstanding) there is no direct evidence for gravity waves, the Hulse-Taylor binary pulsar was good enough indirect evidence for the Nobel committee.
Steuard 11y ago
We haven't seen direct evidence of gravitational waves yet (unless the current LIGO rumors pan out!), but there's already compelling indirect evidence. The most specific example I know of comes from the Hulse–Taylor binary system (https://en.wikipedia.org/wiki/PSR_B1913%2B16 https://en.wikipedia.org/wiki/PSR_B1913%2B16), in which a pulsar and another neutron star orbit each other every 7.75 hours (separated by a variable distance of roughly the diameter of our Sun). The period of their orbit is decaying over time, at a rate that is in precise agreement with the predicted energy loss due to gravitational radiation in such a system (the observed rate of energy loss is 99.7% +/- 0.2% of the gravitational wave prediction). So while we haven't seen them directly yet (they're really, really hard to detect!), there's very little doubt that they're out there more or less exactly as Einstein predicted.
empath75 11y ago
You have some theory x. Based on that theory, you can use math and logic to predict what else should be true. As a consequence of x, let's say that following the math predicts that y should exist. We already know that y exists, so we have some reason for believing x to be true. x also predicts that z exists, but we haven't discovered that z exists -- based on that should we assume that z exists but we haven't discovered it, or that x is wrong? I think probably either conclusion is fine. But if we later discover that z exists, that gives us _really_ strong evidence that x is true. It's not exactly that math always predicts science, but that math allows us to filter theories based on what we else we know to be true. If working out the math based on your theory gives us answers that don't match reality, then there's probably something wrong with your theory.
mikeash 11y ago
That's a pretty deep question that a lot of smart people have tried to address. For example: https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness...

evanb 11y ago

* Maybe. http://www.skyandtelescope.com/astronomy-news/about-this-weeks-gravitational-wave-rumor/ http://www.skyandtelescope.com/astronomy-news/about-this-wee...

rotorblade 11y ago

Well, it is a good feature of a theory. Imagine that you would have two competing theories but they give different predictions, then a measurement on those predictions would determine which is which. (If they give the same predictions, an interesting questions would be 'is there a mathematical proof that they are the same?'.) For example with GR, it explained for example the precession of Mercury's elliptical orbit, and predicted time dilation (used now in GPS for example) and bending of light. It is true that gravity waves remains to be directly detected. This is how physics have usually progressed in the past: Have an old theory, have some experiments not explained by that theory, invent new theory that can be reduced to the old theory and explains these new experiments and give new predictions. (The subject of string theory is somewhat different however.)

marcosdumay 11y ago

We keep the math that predicts physics, and throw everything else away. So, it's too easy to assemble a small narrative of history that gives this impression, and forget every other model that people crated trying to get to those ones that hold.

cozzyd 11y ago

Even though (LIGO's rumored result notwithstanding) there is no direct evidence for gravity waves, the Hulse-Taylor binary pulsar was good enough indirect evidence for the Nobel committee.

Steuard 11y ago

We haven't seen direct evidence of gravitational waves yet (unless the current LIGO rumors pan out!), but there's already compelling indirect evidence. The most specific example I know of comes from the Hulse–Taylor binary system (https://en.wikipedia.org/wiki/PSR_B1913%2B16 https://en.wikipedia.org/wiki/PSR_B1913%2B16), in which a pulsar and another neutron star orbit each other every 7.75 hours (separated by a variable distance of roughly the diameter of our Sun). The period of their orbit is decaying over time, at a rate that is in precise agreement with the predicted energy loss due to gravitational radiation in such a system (the observed rate of energy loss is 99.7% +/- 0.2% of the gravitational wave prediction). So while we haven't seen them directly yet (they're really, really hard to detect!), there's very little doubt that they're out there more or less exactly as Einstein predicted.

empath75 11y ago

You have some theory x. Based on that theory, you can use math and logic to predict what else should be true. As a consequence of x, let's say that following the math predicts that y should exist. We already know that y exists, so we have some reason for believing x to be true. x also predicts that z exists, but we haven't discovered that z exists -- based on that should we assume that z exists but we haven't discovered it, or that x is wrong? I think probably either conclusion is fine. But if we later discover that z exists, that gives us _really_ strong evidence that x is true. It's not exactly that math always predicts science, but that math allows us to filter theories based on what we else we know to be true. If working out the math based on your theory gives us answers that don't match reality, then there's probably something wrong with your theory.

mikeash 11y ago

That's a pretty deep question that a lot of smart people have tried to address. For example: https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness...