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  • Could human civilization eventually spread across the whole Milky Way galaxy?

  • Could we move beyond our small blue planet

  • to establish colonies in the multitude of star systems out there?

  • This question's a pretty daunting one.

  • There are around 300 billion stars in the galaxy,

  • which is about 160,000 light-years across.

  • So far we've sent a single spacecraft outside our solar system,

  • trudging along at 0.006% of the speed of light.

  • At that rate, it would take over 2.5 billion years

  • just to get from one end of the galaxy to the other.

  • And then there's the question of human survival.

  • The gulf between stars is simply enormous.

  • We couldn't live sustainably on most planets,

  • and we require a lot of resources to stay alive.

  • And yet, decades ago, scholars found that it's theoretically possible

  • to not just spread human civilization across the galaxy,

  • but to do so quite quickly,

  • without breaking any known laws of physics.

  • Their idea is based on the work of a mathematician named John von Neumann,

  • who designed on paper machines that could self-replicate

  • and create new generations of themselves.

  • These would later come to be known as von Neumann machines.

  • In the context of space exploration,

  • von Neumann machines could be built on Earth

  • and launched into space.

  • There, the self-sufficient machines would land on distant planets.

  • They would then mine the available resources and harvest energy,

  • build replicas of themselves,

  • launch those to the nearest planets,

  • and continue the cycle.

  • The result is the creation of millions of probes

  • spreading outwards into the universe like a drop of ink in a fishbowl.

  • Scholars crunched the numbers and found that a single von Neumann machine

  • traveling at 5% of the speed of light

  • should be able to replicate throughout our galaxy in 4 million years or less.

  • That may sound like a long time,

  • but when you consider that our universe is 14 billion years old,

  • on a cosmic scale, it's incredibly fast -

  • the equivalent of about 2.5 hours in an entire year.

  • Creating von Neumann machines would require a few technologies

  • we don't have yet,

  • including advanced artificial intelligence,

  • miniaturization,

  • and better propulsion systems.

  • If we wanted to use them to spread actual humans throughout the galaxy,

  • we would need yet another technological leap -

  • the ability to artificially grow biological organisms and bodies

  • using raw elements and genetic information.

  • Regardless, if in the last billion years

  • an alien civilization created such a machine

  • and set it multiplying its way toward us,

  • our galaxy would be swarming with them by now.

  • So then where are all these machines?

  • Some astronomers, like Carl Sagan,

  • say that intelligent aliens wouldn't build self-replicating machines at all.

  • They might hurtle out of control,

  • scavaging planets to their cores in order to keep replicating.

  • Others take the machines' absence as proof

  • that intelligent alien civilizations don't exist,

  • or that they go extinct before they can develop the necessary technologies.

  • But all this hasn't stopped people from imagining

  • what it would be like if they were out there.

  • Science fiction author David Brin

  • writes about an universe in which many different von Neumann machines exist

  • and proliferate simultaneously.

  • Some are designed to greet young civilizations,

  • others to locate and destroy them before they become a threat.

  • In fact, in Brin's story "Lungfish,"

  • some von Neumann machines are keeping a close watch over the Earth right now,

  • waiting for us to reach a certain level of sophistication

  • before they make their move.

  • For now, all we have is curiosity and theory.

  • But the next time you look at the night sky,

  • consider that billions of self-replicating machines

  • could be advancing between stars in our galaxy right now.

  • If they exist, one of them will eventually land on Earth,

  • or maybe, just maybe, they're already here.

Could human civilization eventually spread across the whole Milky Way galaxy?


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TED-ED】人類の文明は銀河系全体に広がるのか?- ロエイ・ツェザナ (【TED-Ed】Could human civilization spread across the whole galaxy? - Roey Tzezana)

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    何庭昀 に公開 2021 年 01 月 14 日