JUL 25, 2017 07:24 AM PDT
Lasers Can Be Really Cool Too...
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When you think of lasers, most think of intense heat. Lasers can be used to break up tumors and stones, they can cut through metal and wood, and they can even burn your hair off. Ouch. However, they can be used to cool things off as well. The difference between something being hot or cold is essentially about how fast the molecules in that substance are moving. In a hot liquid, the molecules are moving around, creating energy and heat. In something that is cold, or even frozen, there's not much movement in the molecules, thus less energy, and less heat.

So how does adding energy, via a laser, make things cooler, if energy causes molecules to move around and heat up? Well, light in addition to having energy, has momentum, even without mass. So when a molecule in motion is going in one direction, light, with its momentum, can be focused on it by pushing against the direction it's going in and shoving it back, slowing its motion down. Slowing down the motion of a molecule will cool it off. Of course, molecules don't just move in a linear path, they bounce all over the place, so multiple lasers are needed from every direction to slow the roll of a fast moving molecule and cool it down. They won't completely stop, but they will be affected enough to have temperatures drop.

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