[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.66,0:00:12.10,Default,,0000,0000,0000,,Could human civilization eventually spread\Nacross the whole Milky Way galaxy?
Dialogue: 0,0:00:12.10,0:00:15.25,Default,,0000,0000,0000,,Could we move beyond \Nour small blue planet
Dialogue: 0,0:00:15.25,0:00:19.70,Default,,0000,0000,0000,,to establish colonies in the multitude\Nof star systems out there?
Dialogue: 0,0:00:19.70,0:00:21.96,Default,,0000,0000,0000,,This question's a pretty daunting one.
Dialogue: 0,0:00:21.96,0:00:25.94,Default,,0000,0000,0000,,There are around 300 billion stars\Nin the galaxy,
Dialogue: 0,0:00:25.94,0:00:29.49,Default,,0000,0000,0000,,which is about 160,000 light-years across.
Dialogue: 0,0:00:29.49,0:00:34.02,Default,,0000,0000,0000,,So far we've sent a single spacecraft\Noutside our solar system,
Dialogue: 0,0:00:34.02,0:00:39.21,Default,,0000,0000,0000,,trudging along at 0.006% of \Nthe speed of light.
Dialogue: 0,0:00:39.21,0:00:42.62,Default,,0000,0000,0000,,At that rate, it would take over \N2.5 billion years
Dialogue: 0,0:00:42.62,0:00:45.76,Default,,0000,0000,0000,,just to get from one end of the galaxy\Nto the other.
Dialogue: 0,0:00:45.76,0:00:48.33,Default,,0000,0000,0000,,And then there's the question \Nof human survival.
Dialogue: 0,0:00:48.33,0:00:51.46,Default,,0000,0000,0000,,The gulf between stars is simply enormous.
Dialogue: 0,0:00:51.46,0:00:54.17,Default,,0000,0000,0000,,We couldn't live sustainably \Non most planets,
Dialogue: 0,0:00:54.17,0:00:57.88,Default,,0000,0000,0000,,and we require a lot of resources\Nto stay alive.
Dialogue: 0,0:00:57.88,0:01:01.88,Default,,0000,0000,0000,,And yet, decades ago, scholars found\Nthat it's theoretically possible
Dialogue: 0,0:01:01.88,0:01:05.18,Default,,0000,0000,0000,,to not just spread human civilization\Nacross the galaxy,
Dialogue: 0,0:01:05.18,0:01:07.61,Default,,0000,0000,0000,,but to do so quite quickly,
Dialogue: 0,0:01:07.61,0:01:10.98,Default,,0000,0000,0000,,without breaking any known \Nlaws of physics.
Dialogue: 0,0:01:10.98,0:01:15.14,Default,,0000,0000,0000,,Their idea is based on the work\Nof a mathematician named John von Neumann,
Dialogue: 0,0:01:15.14,0:01:18.89,Default,,0000,0000,0000,,who designed on paper machines \Nthat could self-replicate
Dialogue: 0,0:01:18.89,0:01:21.68,Default,,0000,0000,0000,,and create new generations of themselves.
Dialogue: 0,0:01:21.68,0:01:25.57,Default,,0000,0000,0000,,These would later come to be known\Nas von Neumann machines.
Dialogue: 0,0:01:25.57,0:01:27.53,Default,,0000,0000,0000,,In the context of space exploration,
Dialogue: 0,0:01:27.53,0:01:30.04,Default,,0000,0000,0000,,von Neumann machines could be\Nbuilt on Earth
Dialogue: 0,0:01:30.04,0:01:32.18,Default,,0000,0000,0000,,and launched into space.
Dialogue: 0,0:01:32.18,0:01:36.24,Default,,0000,0000,0000,,There, the self-sufficient machines\Nwould land on distant planets.
Dialogue: 0,0:01:36.24,0:01:40.44,Default,,0000,0000,0000,,They would then mine the available\Nresources and harvest energy,
Dialogue: 0,0:01:40.44,0:01:42.69,Default,,0000,0000,0000,,build replicas of themselves,
Dialogue: 0,0:01:42.69,0:01:44.63,Default,,0000,0000,0000,,launch those to the nearest planets,
Dialogue: 0,0:01:44.63,0:01:46.45,Default,,0000,0000,0000,,and continue the cycle.
Dialogue: 0,0:01:46.45,0:01:49.49,Default,,0000,0000,0000,,The result is the creation \Nof millions of probes
Dialogue: 0,0:01:49.49,0:01:54.11,Default,,0000,0000,0000,,spreading outwards into the universe\Nlike a drop of ink in a fishbowl.
Dialogue: 0,0:01:54.11,0:01:57.72,Default,,0000,0000,0000,,Scholars crunched the numbers and found\Nthat a single von Neumann machine
Dialogue: 0,0:01:57.72,0:02:00.40,Default,,0000,0000,0000,,traveling at 5% of the speed of light
Dialogue: 0,0:02:00.40,0:02:06.12,Default,,0000,0000,0000,,should be able to replicate throughout\Nour galaxy in 4 million years or less.
Dialogue: 0,0:02:06.12,0:02:07.97,Default,,0000,0000,0000,,That may sound like a long time,
Dialogue: 0,0:02:07.97,0:02:11.55,Default,,0000,0000,0000,,but when you consider that our universe\Nis 14 billion years old,
Dialogue: 0,0:02:11.55,0:02:14.32,Default,,0000,0000,0000,,on a cosmic scale, it's incredibly fast -
Dialogue: 0,0:02:14.32,0:02:19.76,Default,,0000,0000,0000,,the equivalent of about 2.5 hours\Nin an entire year.
Dialogue: 0,0:02:19.76,0:02:23.25,Default,,0000,0000,0000,,Creating von Neumann machines\Nwould require a few technologies
Dialogue: 0,0:02:23.25,0:02:24.89,Default,,0000,0000,0000,,we don't have yet,
Dialogue: 0,0:02:24.89,0:02:27.05,Default,,0000,0000,0000,,including advanced \Nartificial intelligence,
Dialogue: 0,0:02:27.05,0:02:28.55,Default,,0000,0000,0000,,miniaturization,
Dialogue: 0,0:02:28.55,0:02:30.79,Default,,0000,0000,0000,,and better propulsion systems.
Dialogue: 0,0:02:30.79,0:02:34.25,Default,,0000,0000,0000,,If we wanted to use them to spread actual\Nhumans throughout the galaxy,
Dialogue: 0,0:02:34.25,0:02:37.01,Default,,0000,0000,0000,,we would need \Nyet another technological leap -
Dialogue: 0,0:02:37.01,0:02:41.60,Default,,0000,0000,0000,,the ability to artificially \Ngrow biological organisms and bodies
Dialogue: 0,0:02:41.60,0:02:44.93,Default,,0000,0000,0000,,using raw elements \Nand genetic information.
Dialogue: 0,0:02:44.93,0:02:47.43,Default,,0000,0000,0000,,Regardless, if in the last billion years
Dialogue: 0,0:02:47.43,0:02:50.22,Default,,0000,0000,0000,,an alien civilization \Ncreated such a machine
Dialogue: 0,0:02:50.22,0:02:53.12,Default,,0000,0000,0000,,and set it multiplying its way toward us,
Dialogue: 0,0:02:53.12,0:02:56.37,Default,,0000,0000,0000,,our galaxy would be \Nswarming with them by now.
Dialogue: 0,0:02:56.37,0:02:58.98,Default,,0000,0000,0000,,So then where are all these machines?
Dialogue: 0,0:02:58.98,0:03:01.08,Default,,0000,0000,0000,,Some astronomers, like Carl Sagan,
Dialogue: 0,0:03:01.08,0:03:06.03,Default,,0000,0000,0000,,say that intelligent aliens wouldn't\Nbuild self-replicating machines at all.
Dialogue: 0,0:03:06.03,0:03:07.77,Default,,0000,0000,0000,,They might hurtle out of control,
Dialogue: 0,0:03:07.77,0:03:11.52,Default,,0000,0000,0000,,scavaging planets to their cores\Nin order to keep replicating.
Dialogue: 0,0:03:11.52,0:03:13.73,Default,,0000,0000,0000,,Others take the machines absence as proof
Dialogue: 0,0:03:13.73,0:03:17.12,Default,,0000,0000,0000,,that intelligent alien civilizations \Ndon't exist,
Dialogue: 0,0:03:17.12,0:03:21.68,Default,,0000,0000,0000,,or that they go extinct before they can\Ndevelop the necessary technologies.
Dialogue: 0,0:03:21.68,0:03:25.06,Default,,0000,0000,0000,,But all this hasn't stopped people from\Nimagining what it would be like
Dialogue: 0,0:03:25.06,0:03:27.10,Default,,0000,0000,0000,,if they were out there.
Dialogue: 0,0:03:27.10,0:03:28.86,Default,,0000,0000,0000,,Science fiction author David Brin
Dialogue: 0,0:03:28.86,0:03:33.01,Default,,0000,0000,0000,,writes about a universe in which\Nmany different von Neumann machines exist
Dialogue: 0,0:03:33.01,0:03:35.19,Default,,0000,0000,0000,,and proliferate simultaneously.
Dialogue: 0,0:03:35.19,0:03:38.27,Default,,0000,0000,0000,,Some are designed \Nto greet young civilizations,
Dialogue: 0,0:03:38.27,0:03:41.86,Default,,0000,0000,0000,,others to locate and destroy them\Nbefore they become a threat.
Dialogue: 0,0:03:41.86,0:03:44.82,Default,,0000,0000,0000,,In fact, in Brin's story "Lungfish,"
Dialogue: 0,0:03:44.82,0:03:50.38,Default,,0000,0000,0000,,some von Neumann machines are keeping\Na close watch over the Earth right now,
Dialogue: 0,0:03:50.38,0:03:53.20,Default,,0000,0000,0000,,waiting for us to reach a certain level\Nof sophistication
Dialogue: 0,0:03:53.20,0:03:55.74,Default,,0000,0000,0000,,before they make their move.
Dialogue: 0,0:03:55.74,0:03:59.03,Default,,0000,0000,0000,,For now, all we have is curiosity \Nand theory.
Dialogue: 0,0:03:59.03,0:04:01.14,Default,,0000,0000,0000,,But the next time \Nyou look at the night sky,
Dialogue: 0,0:04:01.14,0:04:04.08,Default,,0000,0000,0000,,consider that billions of\Nself-replicating machines
Dialogue: 0,0:04:04.08,0:04:09.52,Default,,0000,0000,0000,,could be advancing between stars\Nin our galaxy right now.
Dialogue: 0,0:04:09.52,0:04:13.30,Default,,0000,0000,0000,,If they exist, one of them will eventually\Nland on Earth,
Dialogue: 0,0:04:13.30,0:04:17.12,Default,,0000,0000,0000,,or maybe, just maybe,\Nthey're already here.