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that's kind of crazy

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to think that you make something cold by

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shining light on it normally we think

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about shining light on something and

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making it hot laser cooling does

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something quite counterintuitive it

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makes something cold by shining light on

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temperature is about motion the

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molecules in the air in this room are

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moving really fast about 300 meters per

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second if you cool down a gas you're

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making the atoms and molecules move more

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slowly and getting to the lowest

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possible temperatures that's the extreme

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that we're trying to go to on cow and we

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learn something new when we go to those

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extremely low temperatures we start with

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atoms that are actually room temperature

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even a little bit hotter than room

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temperature we just have a vapor of them

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in a glass cell where we use radiation

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pressure from lasers to slow down atoms

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as it turns out white pushes on stuff we

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don't feel it when we walk out in the

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sunlight but for something as light as

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an atom the push that you can exert by

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shining light on the atom in our case

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laser light can be really significant we

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don't actually use two lasers we

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actually use six and there's two this

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way - vertical - in and out and so no

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matter which way the atoms moving it's

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always moving towards one of the lasers

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and that causes low down and cools them

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down to one thousandth of the degree

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above absolute zero

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but eventually to get to the

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temperatures that we need for cow we

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actually have to turn off the lasers and

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what we do is we move the atoms so the

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held by magnetic forces and what we can

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do now is we can just adjust the

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magnetic field so that this trap that

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they're held in is not very deep so we

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can make it so that the most energetic

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atoms just have enough energy to just

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move off and escape and they fly away we

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can actually pull out just the hot atoms

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leaving the rest of them at a colles of

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temperature this is called a rapid of

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cooling it's essentially the same as

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when you blow on your coffee cup the

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hottest molecules make it out of the

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water and if you can constantly be

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blowing those away you can cool down and

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that gets us all the way down to these

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temperatures for micro Kelvin millionth

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of a degree above absolute zero but it

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turns out you can get even colder by

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using another really old trick called

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about expansion if you take any gas and

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you expand it it'll get colder so we're

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doing the same thing on a sort of small

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scale we have this little small sample

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of atoms that are confined by magnetic

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fields and what we're doing is we're

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reducing the strength of that magnetic

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field which lets the atoms expand out

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something like a factor of a thousand

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which causes them to cool off by a

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factor of a thousand this trick works so

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well we get down to temperatures below

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one nano tip one billionth of a degree

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above absolute zero and it's being done