eli5: I saw a post on instagram saying “Sonoluminescence – If you collapse an underwater bubble with a soundwave, light is produced, and nobody knows why” is this true?
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I’m going to focus more on the “nobody knows why” bit for readers coming here.
Any time someone makes this claim, its good to be skeptical. In many cases, maybe even most, these are used as a sort of stawman argument: making up a claim in order to undermine an argument for someone else. I see this all the time in evolutionary biology where people trot out a similar argument (no one knows how such a complex structure evolved, therefore it is proof of intelligent design. In reality, we absolutely do know how the favourite straw-men evolved, and can trace it back billions of years ^/rant). On another note, things like this are also prime sources of disinformation to be wary of.
The reality is that, in most cases, we either do understand something, or at least have a good idea of the principles behind it. In the cases we don’t know, though, it doesn’t mean that something should be inferred (such as an unusual biological system being proof of god’s existence). Sometimes “I don’t know” is just as valid an answer on its own. That said, researchers will also probably be pretty annoyed at not knowing something about their field and already be figuring out ways to get that knowledge, so I’d also trust an expert opinion if they say “we think we’re looking at [X]”.
I’ve seen some good explanations so far, but since I have done this myself, I’ll throw my hat in the ring.
When you boil pure water, it creates very small bubbles. You can vibrate these bubbles using sound so that they expand, most effectively with resonance (think of being in tune with the water). Well, as the bubbles expand, they reach a tipping point (about 50x their original size). This tipping point is still exceedingly small. When the bubble passes this point, it collapses, or pops. This pop happens rapidly enough in such a small space that it has more energy than the surface of the sun. However, due to its constraints, the energy is only expressed as a very small flash of light (think about how when explosives “pop” there is a production of light).
There’s relatively limited research into the effect as far as I’m aware, but if you want to do some reading, I’d recommend looking at Seth Putterman’s papers.
Is this the same phenomenon as the mantis shrimp punch? that it’s so fast it boils the water and can cause this
Have you ever “sparked off” <grin> in a dark room by biting wintergreen lifesavers? The flashes in your mouth from biting them are impressive. Why only wintergreen?
Something to keep in mind on most of these “nobody knows why” questions.
99% of the time, its not that we have zero idea why something happens. Its that there are many different ways that it could have happened, and there has not been enough study done to identify which theory is correct.
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