[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.72,0:00:10.40,Default,,0000,0000,0000,,The coldest materials in the world \Naren’t in Antarctica.
Dialogue: 0,0:00:10.40,0:00:12.52,Default,,0000,0000,0000,,They’re not at the top of Mount Everest
Dialogue: 0,0:00:12.52,0:00:14.38,Default,,0000,0000,0000,,or buried in a glacier.
Dialogue: 0,0:00:14.38,0:00:15.90,Default,,0000,0000,0000,,They’re in physics labs:
Dialogue: 0,0:00:15.90,0:00:20.38,Default,,0000,0000,0000,,clouds of gases held just fractions\Nof a degree above absolute zero.
Dialogue: 0,0:00:20.38,0:00:25.37,Default,,0000,0000,0000,,That’s 395 million times colder \Nthan your refrigerator,
Dialogue: 0,0:00:25.37,0:00:28.07,Default,,0000,0000,0000,,100 million times colder \Nthan liquid nitrogen,
Dialogue: 0,0:00:28.07,0:00:31.24,Default,,0000,0000,0000,,and 4 million times colder\Nthan outer space.
Dialogue: 0,0:00:31.24,0:00:35.90,Default,,0000,0000,0000,,Temperatures this low give scientists a\Nwindow into the inner workings of matter,
Dialogue: 0,0:00:35.90,0:00:39.44,Default,,0000,0000,0000,,and allow engineers to build \Nincredibly sensitive instruments
Dialogue: 0,0:00:39.44,0:00:41.29,Default,,0000,0000,0000,,that tell us more about everything
Dialogue: 0,0:00:41.29,0:00:43.13,Default,,0000,0000,0000,,from our exact position on the planet
Dialogue: 0,0:00:43.13,0:00:46.14,Default,,0000,0000,0000,,to what’s happening in \Nthe farthest reaches of the universe.
Dialogue: 0,0:00:46.14,0:00:48.93,Default,,0000,0000,0000,,How do we create such \Nextreme temperatures?
Dialogue: 0,0:00:48.93,0:00:51.99,Default,,0000,0000,0000,,In short, by slowing down \Nmoving particles.
Dialogue: 0,0:00:51.99,0:00:55.95,Default,,0000,0000,0000,,When we’re talking about temperature,\Nwhat we’re really talking about is motion.
Dialogue: 0,0:00:55.95,0:00:57.72,Default,,0000,0000,0000,,The atoms that make up solids,
Dialogue: 0,0:00:57.72,0:00:58.46,Default,,0000,0000,0000,,liquids,
Dialogue: 0,0:00:58.46,0:00:59.34,Default,,0000,0000,0000,,and gases
Dialogue: 0,0:00:59.34,0:01:00.87,Default,,0000,0000,0000,,are moving all the time.
Dialogue: 0,0:01:00.87,0:01:05.62,Default,,0000,0000,0000,,When atoms are moving more rapidly,\Nwe perceive that matter as hot.
Dialogue: 0,0:01:05.62,0:01:09.15,Default,,0000,0000,0000,,When they’re moving more\Nslowly, we perceive it as cold.
Dialogue: 0,0:01:09.15,0:01:12.56,Default,,0000,0000,0000,,To make a hot object \Nor gas cold in everyday life,
Dialogue: 0,0:01:12.56,0:01:15.96,Default,,0000,0000,0000,,we place it in a colder environment, \Nlike a refrigerator.
Dialogue: 0,0:01:15.96,0:01:20.50,Default,,0000,0000,0000,,Some of the atomic motion in the hot\Nobject is transferred to the surroundings,
Dialogue: 0,0:01:20.50,0:01:22.25,Default,,0000,0000,0000,,and it cools down.
Dialogue: 0,0:01:22.25,0:01:23.79,Default,,0000,0000,0000,,But there’s a limit to this:
Dialogue: 0,0:01:23.79,0:01:27.86,Default,,0000,0000,0000,,even outer space is too warm\Nto create ultra-low temperatures.
Dialogue: 0,0:01:27.86,0:01:32.82,Default,,0000,0000,0000,,So instead, scientists figured out a way \Nto slow the atoms down directly –
Dialogue: 0,0:01:32.82,0:01:34.20,Default,,0000,0000,0000,,with a laser beam.
Dialogue: 0,0:01:34.20,0:01:35.75,Default,,0000,0000,0000,,Under most circumstances,
Dialogue: 0,0:01:35.75,0:01:38.46,Default,,0000,0000,0000,,the energy in a laser beam \Nheats things up.
Dialogue: 0,0:01:38.46,0:01:40.53,Default,,0000,0000,0000,,But used in a very precise way,
Dialogue: 0,0:01:40.53,0:01:44.81,Default,,0000,0000,0000,,the beam’s momentum can stall \Nmoving atoms, cooling them down.
Dialogue: 0,0:01:44.81,0:01:49.40,Default,,0000,0000,0000,,That’s what happens in a device \Ncalled a magneto-optical trap.
Dialogue: 0,0:01:49.40,0:01:51.95,Default,,0000,0000,0000,,Atoms are injected into a vacuum chamber,
Dialogue: 0,0:01:51.95,0:01:55.42,Default,,0000,0000,0000,,and a magnetic field \Ndraws them towards the center.
Dialogue: 0,0:01:55.42,0:01:58.09,Default,,0000,0000,0000,,A laser beam aimed \Nat the middle of the chamber
Dialogue: 0,0:01:58.09,0:02:00.62,Default,,0000,0000,0000,,is tuned to just the right frequency
Dialogue: 0,0:02:00.62,0:02:06.17,Default,,0000,0000,0000,,that an atom moving towards it will absorb\Na photon of the laser beam and slow down.
Dialogue: 0,0:02:06.17,0:02:09.09,Default,,0000,0000,0000,,The slow down effect comes from\Nthe transfer of momentum
Dialogue: 0,0:02:09.09,0:02:11.11,Default,,0000,0000,0000,,between the atom and the photon.
Dialogue: 0,0:02:11.11,0:02:14.21,Default,,0000,0000,0000,,A total of six beams, \Nin a perpendicular arrangement,
Dialogue: 0,0:02:14.21,0:02:18.38,Default,,0000,0000,0000,,ensure that atoms traveling \Nin all directions will be intercepted.
Dialogue: 0,0:02:18.38,0:02:21.02,Default,,0000,0000,0000,,At the center, where the beams intersect,
Dialogue: 0,0:02:21.02,0:02:24.84,Default,,0000,0000,0000,,the atoms move sluggishly, \Nas if trapped in a thick liquid —
Dialogue: 0,0:02:24.84,0:02:29.92,Default,,0000,0000,0000,,an effect the researchers who invented it \Ndescribed as “optical molasses.”
Dialogue: 0,0:02:29.92,0:02:32.32,Default,,0000,0000,0000,,A magneto-optical trap like this
Dialogue: 0,0:02:32.32,0:02:35.40,Default,,0000,0000,0000,,can cool atoms down \Nto just a few microkelvins —
Dialogue: 0,0:02:35.40,0:02:38.78,Default,,0000,0000,0000,,about -273 degrees Celsius.
Dialogue: 0,0:02:38.78,0:02:41.61,Default,,0000,0000,0000,,This technique was developed in the 1980s,
Dialogue: 0,0:02:41.61,0:02:43.91,Default,,0000,0000,0000,,and the scientists \Nwho'd contributed to it
Dialogue: 0,0:02:43.91,0:02:47.93,Default,,0000,0000,0000,,won the Nobel Prize in Physics in 1997\Nfor the discovery.
Dialogue: 0,0:02:47.93,0:02:52.75,Default,,0000,0000,0000,,Since then, laser cooling has been \Nimproved to reach even lower temperatures.
Dialogue: 0,0:02:52.75,0:02:55.99,Default,,0000,0000,0000,,But why would you want \Nto cool atoms down that much?
Dialogue: 0,0:02:55.99,0:02:59.79,Default,,0000,0000,0000,,First of all, cold atoms can make\Nvery good detectors.
Dialogue: 0,0:02:59.79,0:03:01.53,Default,,0000,0000,0000,,With so little energy,
Dialogue: 0,0:03:01.53,0:03:04.96,Default,,0000,0000,0000,,they’re incredibly sensitive \Nto fluctuations in the environment.
Dialogue: 0,0:03:04.96,0:03:09.56,Default,,0000,0000,0000,,So they’re used in devices that find \Nunderground oil and mineral deposits,
Dialogue: 0,0:03:09.56,0:03:12.20,Default,,0000,0000,0000,,and they also make \Nhighly accurate atomic clocks,
Dialogue: 0,0:03:12.20,0:03:15.09,Default,,0000,0000,0000,,like the ones used \Nin global positioning satellites.
Dialogue: 0,0:03:15.09,0:03:18.15,Default,,0000,0000,0000,,Secondly, cold atoms hold \Nenormous potential
Dialogue: 0,0:03:18.15,0:03:20.24,Default,,0000,0000,0000,,for probing the frontiers of physics.
Dialogue: 0,0:03:20.24,0:03:22.66,Default,,0000,0000,0000,,Their extreme sensitivity \Nmakes them candidates
Dialogue: 0,0:03:22.66,0:03:27.30,Default,,0000,0000,0000,,to be used to detect gravitational waves \Nin future space-based detectors.
Dialogue: 0,0:03:27.30,0:03:31.62,Default,,0000,0000,0000,,They’re also useful for the study \Nof atomic and subatomic phenomena,
Dialogue: 0,0:03:31.62,0:03:35.89,Default,,0000,0000,0000,,which requires measuring incredibly \Ntiny fluctuations in the energy of atoms.
Dialogue: 0,0:03:35.89,0:03:38.05,Default,,0000,0000,0000,,Those are drowned out \Nat normal temperatures,
Dialogue: 0,0:03:38.05,0:03:41.09,Default,,0000,0000,0000,,when atoms speed around \Nat hundreds of meters per second.
Dialogue: 0,0:03:41.09,0:03:45.26,Default,,0000,0000,0000,,Laser cooling can slow atoms to just \Na few centimeters per second—
Dialogue: 0,0:03:45.26,0:03:49.12,Default,,0000,0000,0000,,enough for the motion caused by\Natomic quantum effects to become obvious.
Dialogue: 0,0:03:49.12,0:03:53.60,Default,,0000,0000,0000,,Ultracold atoms have already \Nallowed scientists to study phenomena
Dialogue: 0,0:03:53.60,0:03:56.15,Default,,0000,0000,0000,,like Bose-Einstein condensation,
Dialogue: 0,0:03:56.15,0:03:59.63,Default,,0000,0000,0000,,in which atoms are cooled almost \Nto absolute zero
Dialogue: 0,0:03:59.63,0:04:02.20,Default,,0000,0000,0000,,and become a rare new state of matter.
Dialogue: 0,0:04:02.20,0:04:05.79,Default,,0000,0000,0000,,So as researchers continue in their quest \Nto understand the laws of physics
Dialogue: 0,0:04:05.79,0:04:07.92,Default,,0000,0000,0000,,and unravel the mysteries of the universe,
Dialogue: 0,0:04:07.92,0:04:12.16,Default,,0000,0000,0000,,they’ll do so with the help \Nof the very coldest atoms in it.