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  • You probably don't want to mess with the Mantis Shrimp.

  • Its claws have inspired modern body armor and it strikes with 1500 newtons of force despite being quite tiny,

  • what you would need to bench press around 150 kilograms.

  • That strike is so powerful that it creates an unusual effect,

  • one that physicists still haven't quite figured out.

  • When the claws snap, the motion creates small, hot bubbles that collapse to release a powerful shock wave, and even produce a small pulse of light.

  • It's called sonoluminescence.

  • Researchers can create sonoluminescence in the lab to study how exactly the collapsing bubbles produce light and why they are so hot.

  • Because these bubbles aren't just a little warm - they are about as hot as the surface of the Sun.

  • All it takes to produce sonoluminescence is sound with the right frequency moving through water.

  • Sound waves are really just molecules that oscillate back and forth, creating areas of higher and lower pressure.

  • When sound moves through water, the water can get pulled apart enough that the areas of low pressure create a small bubble of water vapor in a process called cavitation.

  • Cavitation bubbles aren't like the regular bubbles you're used to.

  • Regular bubbles are made by releasing gas under water, like when you exhale.

  • Cavitation creates bubbles because the very low pressure essentially tears a gap in the water.

  • Some molecules quickly evaporate into the bubble so it's not a vacuum or anything,

  • but these bubbles do have much lower air pressure than a regular bubble.

  • So they collapse.

  • The walls of the bubble push the inside smaller and smaller so the pressure begins to rapidly increase.

  • There are a couple of ways that the bubbles collapsing could produce heat.

  • One option is that as the pressure increases, so does the temperature, all the way up to several thousand degrees.

  • But it's also possible that it's not just the increase in pressure.

  • The gas inside the bubble might quickly turn back into liquid, which could also release a lot of heat.

  • Either way, the collapse also helps explain why we see a flash of light.

  • Though again, physicians have come up with a few different possible explanations for what's happening.

  • As the bubble gets hotter, different chemical reactions start taking place.

  • Most of the molecules actually react with one another.

  • These chemical reactions could be releasing a small burst of energy.

  • For example, at high enough temperatures, water vapor dissociates. Meaning energy absorbed as the molecule is ripped apart into hydrogen and hydroxide.

  • Then, when these parts recombine again, they release that energy.

  • The light of sonoluminescence could be that released energy.

  • Another possibility has to do with other substances inside the bubbles.

  • If, say, argon is dissolved in the water (which it can be in seawater) then there might also be some argon inside the bubble.

  • And the thing about argon is that it is very stable, it wouldn't react at all.

  • So as the bubble collapsed, everything would react except for argon.

  • The argon would just get hotter and hotter and some of this thermal energy might turn into light.

  • There is some evidence to back this idea up.

  • When scientists tried making cavitation bubbles in water that had extra argon dissolved inside, the light became longer and brighter.

  • Yet another option is that the bubble has enough energy to cause some of the electrons to break free of their atoms.

  • So the bubble ends up with negatively charged electrons separated from positively charged molecules.

  • In other words - plasma.

  • And when the charged molecules vibrate, they release radiation, like light

  • So it's possible that the gas inside the bubble is briefly turning into plasma, releasing light, and then turning back into gas again.

  • And the process of plasma turning back into gas could also caused energy to be released in the form of light.

  • So there are plenty of possible explanations for how a collapsing bubble produces heat and even more for how it produces light.

  • This flash of light only lasts for about 10 billionths of a second, and it's hard to know what's going on in that tiny fraction of a piece of time.

  • But no matter how it happens, understanding a little bit more about sonoluminescence definitely makes me respect mantis shrimp more.

  • Thanks for watching this episode of SciShow, which was brought to you by our Patrons on Patreon.

  • If you want to help support this show,

  • help us keep making this stuff, learning about weird shrimp,

  • you can go to patreon.com/scishow

  • And don't forget to go to youtube.com/SciShow and subscribe.

  • ...if you look at a zebra fish, you probably just see a cute tiny fish that's smaller than your pinky finger,

  • but this little fish is so much more than that. You're looking at an amazing scientific tool...

You probably don't want to mess with the Mantis Shrimp.

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B1 中級 美國腔

声致发光(Sonoluminescence: When Sound Creates Light)

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    joey joey 發佈於 2021 年 05 月 19 日
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