[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.42,0:00:09.78,Default,,0000,0000,0000,,Consider the spot where you’re sitting.
Dialogue: 0,0:00:09.78,0:00:11.64,Default,,0000,0000,0000,,Travel backwards in time
Dialogue: 0,0:00:11.64,0:00:15.50,Default,,0000,0000,0000,,and it might’ve been submerged at \Nthe bottom of a shallow sea,
Dialogue: 0,0:00:15.50,0:00:17.29,Default,,0000,0000,0000,,buried under miles of rock,
Dialogue: 0,0:00:17.29,0:00:21.72,Default,,0000,0000,0000,,or floating through a molten, \Ninfernal landscape.
Dialogue: 0,0:00:21.72,0:00:23.57,Default,,0000,0000,0000,,But go back far enough—
Dialogue: 0,0:00:23.57,0:00:26.50,Default,,0000,0000,0000,,about 4.6 billion years,
Dialogue: 0,0:00:26.50,0:00:30.91,Default,,0000,0000,0000,,and you’d be in the middle of an enormous \Ncloud of dust and gas
Dialogue: 0,0:00:30.91,0:00:34.43,Default,,0000,0000,0000,,orbiting a newborn star.
Dialogue: 0,0:00:34.43,0:00:39.84,Default,,0000,0000,0000,,This is the setting for some of the \Nbiggest, smallest mysteries of physics:
Dialogue: 0,0:00:39.84,0:00:43.41,Default,,0000,0000,0000,,the mysteries of cosmic dust bunnies.
Dialogue: 0,0:00:43.41,0:00:47.22,Default,,0000,0000,0000,,Seemingly empty regions \Nof space between stars
Dialogue: 0,0:00:47.22,0:00:51.35,Default,,0000,0000,0000,,actually contain clouds of gas and dust,
Dialogue: 0,0:00:51.35,0:00:54.70,Default,,0000,0000,0000,,usually blown there by supernovas.
Dialogue: 0,0:00:54.70,0:00:59.34,Default,,0000,0000,0000,,When a dense cloud reaches a certain \Nthreshold called the Jeans mass,
Dialogue: 0,0:00:59.34,0:01:02.22,Default,,0000,0000,0000,,it collapses in on itself.
Dialogue: 0,0:01:02.22,0:01:06.76,Default,,0000,0000,0000,,The shrinking cloud rotates faster \Nand faster, and heats up,
Dialogue: 0,0:01:06.76,0:01:11.54,Default,,0000,0000,0000,,eventually becoming hot enough to burn \Nhydrogen in its core.
Dialogue: 0,0:01:11.54,0:01:14.13,Default,,0000,0000,0000,,At this point a star is born.
Dialogue: 0,0:01:14.13,0:01:16.69,Default,,0000,0000,0000,,As fusion begins in the new star,
Dialogue: 0,0:01:16.69,0:01:21.98,Default,,0000,0000,0000,,it sends out jets of gas that blow \Noff the top and bottom of the cloud,
Dialogue: 0,0:01:21.99,0:01:28.91,Default,,0000,0000,0000,,leaving behind an orbiting ring of gas \Nand dust called a protoplanetary disk.’
Dialogue: 0,0:01:28.91,0:01:31.96,Default,,0000,0000,0000,,This is a surprisingly windy place;
Dialogue: 0,0:01:31.96,0:01:36.94,Default,,0000,0000,0000,,eddies of gas carry particles apart, \Nand send them smashing into each other.
Dialogue: 0,0:01:36.94,0:01:43.57,Default,,0000,0000,0000,,The dust consists of tiny metal fragments,\Nbits of rock, and, further out, ices.
Dialogue: 0,0:01:43.57,0:01:46.69,Default,,0000,0000,0000,,We’ve observed thousands of these disks \Nin the sky,
Dialogue: 0,0:01:46.69,0:01:48.95,Default,,0000,0000,0000,,at various stages of development
Dialogue: 0,0:01:48.95,0:01:53.76,Default,,0000,0000,0000,,as dust clumps together\Ninto larger and larger masses.
Dialogue: 0,0:01:53.76,0:01:59.40,Default,,0000,0000,0000,,Dust grains 100 times smaller than the \Nwidth of a human hair stick to each other
Dialogue: 0,0:01:59.40,0:02:02.32,Default,,0000,0000,0000,,through what’s called \Nthe van der Waals force.
Dialogue: 0,0:02:02.32,0:02:06.71,Default,,0000,0000,0000,,That’s where a cloud of electrons \Nshifts to one side of a molecule,
Dialogue: 0,0:02:06.72,0:02:11.55,Default,,0000,0000,0000,,creating a negative charge on one end, \Nand a positive charge on the other.
Dialogue: 0,0:02:11.55,0:02:16.85,Default,,0000,0000,0000,,Opposites attract, but van der Waals can \Nonly hold tiny things together.
Dialogue: 0,0:02:16.85,0:02:21.16,Default,,0000,0000,0000,,And there’s a problem: once dust \Nclusters grow to a certain size,
Dialogue: 0,0:02:21.16,0:02:25.06,Default,,0000,0000,0000,,the windy atmosphere of a disk should \Nconstantly break them up
Dialogue: 0,0:02:25.06,0:02:26.98,Default,,0000,0000,0000,,as they crash into each other.
Dialogue: 0,0:02:26.98,0:02:33.19,Default,,0000,0000,0000,,The question of how they continue to grow\Nis the first mystery of dust bunnies.
Dialogue: 0,0:02:33.19,0:02:37.42,Default,,0000,0000,0000,,One theory looks to electrostatic charge \Nto answer this.
Dialogue: 0,0:02:37.42,0:02:41.54,Default,,0000,0000,0000,,Energetic gamma rays, x-rays, \Nand UV photons
Dialogue: 0,0:02:41.54,0:02:45.29,Default,,0000,0000,0000,,knock electrons off of gas \Natoms within the disk,
Dialogue: 0,0:02:45.29,0:02:49.10,Default,,0000,0000,0000,,creating positive ions \Nand negative electrons.
Dialogue: 0,0:02:49.10,0:02:52.12,Default,,0000,0000,0000,,Electrons run into and stick to dust,
Dialogue: 0,0:02:52.12,0:02:54.44,Default,,0000,0000,0000,,making it negatively charged.
Dialogue: 0,0:02:54.44,0:02:57.46,Default,,0000,0000,0000,,Now, when the wind pushes \Nclusters together,
Dialogue: 0,0:02:57.46,0:03:02.30,Default,,0000,0000,0000,,like repels like \Nand slows them down as they collide.
Dialogue: 0,0:03:02.30,0:03:04.92,Default,,0000,0000,0000,,With gentle collisions \Nthey won’t fragment,
Dialogue: 0,0:03:04.92,0:03:08.68,Default,,0000,0000,0000,,but if the repulsion is too strong, \Nthey’ll never grow.
Dialogue: 0,0:03:08.68,0:03:12.02,Default,,0000,0000,0000,,One theory suggests that high energy \Nparticles
Dialogue: 0,0:03:12.02,0:03:15.54,Default,,0000,0000,0000,,can knock more electrons off of some \Ndust clumps,
Dialogue: 0,0:03:15.54,0:03:17.82,Default,,0000,0000,0000,,leaving them positively charged.
Dialogue: 0,0:03:17.82,0:03:22.70,Default,,0000,0000,0000,,Opposites again attract, \Nand clusters grow rapidly.
Dialogue: 0,0:03:22.70,0:03:26.32,Default,,0000,0000,0000,,But before long we reach \Nanother set of mysteries.
Dialogue: 0,0:03:26.32,0:03:28.98,Default,,0000,0000,0000,,We know from evidence found in meteorites
Dialogue: 0,0:03:28.98,0:03:33.34,Default,,0000,0000,0000,,that these fluffy dust bunnies \Neventually get heated, melted
Dialogue: 0,0:03:33.34,0:03:38.61,Default,,0000,0000,0000,,and then cooled into solid \Npellets called chondrules.
Dialogue: 0,0:03:38.61,0:03:42.59,Default,,0000,0000,0000,,And we have no idea how \Nor why that happens.
Dialogue: 0,0:03:42.59,0:03:47.47,Default,,0000,0000,0000,,Furthermore, once those pellets do form,\Nhow do they stick together?
Dialogue: 0,0:03:47.47,0:03:50.98,Default,,0000,0000,0000,,The electrostatic forces from before \Nare too weak,
Dialogue: 0,0:03:50.98,0:03:55.30,Default,,0000,0000,0000,,and small rocks can’t be held together \Nby gravity either.
Dialogue: 0,0:03:55.30,0:04:00.25,Default,,0000,0000,0000,,Gravity increases proportionally to the \Nmass of the objects involved.
Dialogue: 0,0:04:00.25,0:04:05.19,Default,,0000,0000,0000,,That’s why you could effortlessly escape \Nan asteroid the size of a small mountain
Dialogue: 0,0:04:05.19,0:04:08.58,Default,,0000,0000,0000,,using just the force generated \Nby your legs.
Dialogue: 0,0:04:08.58,0:04:11.55,Default,,0000,0000,0000,,So if not gravity, then what?
Dialogue: 0,0:04:11.55,0:04:13.73,Default,,0000,0000,0000,,Perhaps it’s dust.
Dialogue: 0,0:04:13.73,0:04:17.92,Default,,0000,0000,0000,,A fluffy dust rim collected around the \Noutside of the pellets
Dialogue: 0,0:04:17.92,0:04:19.75,Default,,0000,0000,0000,,could act like Velcro.
Dialogue: 0,0:04:19.75,0:04:22.37,Default,,0000,0000,0000,,There’s evidence for this in meteors,
Dialogue: 0,0:04:22.37,0:04:28.12,Default,,0000,0000,0000,,where we find many chondrules surrounded\Nby a thin rim of very fine material–
Dialogue: 0,0:04:28.12,0:04:31.47,Default,,0000,0000,0000,,possibly condensed dust.
Dialogue: 0,0:04:31.47,0:04:36.78,Default,,0000,0000,0000,,Eventually the chondrule pellets get \Ncemented together inside larger rocks,
Dialogue: 0,0:04:36.78,0:04:39.26,Default,,0000,0000,0000,,which at about 1 kilometer across
Dialogue: 0,0:04:39.26,0:04:43.89,Default,,0000,0000,0000,,are finally large enough to hold \Nthemselves together through gravity.
Dialogue: 0,0:04:43.89,0:04:48.49,Default,,0000,0000,0000,,They continue to collide and grow \Ninto larger and larger bodies,
Dialogue: 0,0:04:48.49,0:04:51.21,Default,,0000,0000,0000,,including the planets we know today.
Dialogue: 0,0:04:51.21,0:04:54.36,Default,,0000,0000,0000,,Ultimately, the seeds of \Neverything familiar–
Dialogue: 0,0:04:54.36,0:04:57.45,Default,,0000,0000,0000,,the size of our planet, its position \Nwithin the solar system,
Dialogue: 0,0:04:57.45,0:04:59.94,Default,,0000,0000,0000,,and its elemental composition–
Dialogue: 0,0:04:59.94,0:05:05.79,Default,,0000,0000,0000,,were determined by an uncountably large \Nseries of random collisions.
Dialogue: 0,0:05:05.79,0:05:08.18,Default,,0000,0000,0000,,Change the dust cloud just a bit,
Dialogue: 0,0:05:08.18,0:05:10.81,Default,,0000,0000,0000,,and perhaps the conditions wouldn’t \Nhave been right
Dialogue: 0,0:05:10.81,0:05:13.60,Default,,0000,0000,0000,,for the formation of life on our planet.