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Hank tells you about cavitation - the power of tiny bubbles to weaken metal, kill fish & maybe even cure cancer.

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Bubbles. They're awesome, beautiful, little, whimsical, magical pieces of fun. [Getting showered with bubbles] Hello! Hello everyone! It turns out, bubbles can be one of the most destructive forces in nature. And you may have never been injured by a bubble, and from this information I can glean that, one, you are not a boat propeller, and two, you are not a small fish about to be eaten by a pistol shrimp. [SciShow intro] Take a good look at a boat propeller that's been used for a while and you'll see little pits and scars in the propeller. But those pits and scars are made by what we call cavitation bubbles. Cavitation bubbles are bubbles that form when, uh, something disturbs water -- significantly. And it's not the bubbles themselves that do the damage: it's what happens when they pop. [Pops bubble directly in front of camera] That was a good one. She popped on the lens, I think. The instant after those bubbles come into existence, they collapse back upon themselves, and release tiny bolts of extremely violent energy. That could include shock waves, light, high-speed jets of energy, the temperature of the gas coming out of those bubbles can be as high as 15,000 K, which is twice the temperature of the surface of the Sun. All because of a tiny little bubble! It's those high-speed blasts of super-heated gas that cause the gauges in the propeller. And it's worth noting that the stuff we make boat propellers out of is some of the hardest material we know how to make as people. It's also interesting to note that the pistol shrimp, which may be the loudest animal in the ocean, uses its one gigantic claw to clamp down so fast that it causes a cavitation bubble. And when that bubble collapses, it makes a sound so loud that it can kill nearby fish. Scientists have spent decades developing materials that resist cavitation, with some successes. It's not just important for propellers on big boats; it's also a big deal for pumps, specifically like oil pumps, like, refinery stuff. Cavitation bubbles are obviously powerful, but does that mean that they're also useful? Well, a team at Duke University is trying to figure out a way to use cavitation bubbles to help cure cancer. But instead of creating the bubbles with propeller blades or giant pistol shrimp claws, they're creating them with laser guns. Unsurprisingly, I support them fully in this effort -- to use laser guns to create high-speed bubble gas. What the Duke Team did was, one, isolate a cancer cell, two, zap a laser near that cancer cell, creating a tiny bubble, then, four milliseconds later, they created another tiny bubble with another laser beam, very close by to the first bubble. As the second bubble expands, it moves into the first one and then they pop. They can direct where the tiny jet of gas goes, and they can use it to cut a tiny hole in the side of the cancer cell. After about a minute, molecules of colored dye can then seep into the cancer cell. They can pick and adjust that bubble scalpel however they want to. Scientists can use this to do extremely precise cellular surgery that they've never been able to do before. Eventually, researchers hope that they can deliver drugs directly to cells this way, or a simpler possibility: just use those bubble bombs to blow the cancer cells up. This is Hank Green. Thanks for joining us, we hope that you learned something.