0:00:16.200,0:00:19.383
Somewhere out there in that vast universe,

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there must surely be countless[br]other planets teeming with life,

0:00:22.541,0:00:24.972
but why don't we see any evidence of it?

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Well, this is the famous question[br]asked by Enrico Fermi in 1950:

0:00:28.855,0:00:30.089
"Where is everybody?"

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Conspiracy theorists claim[br]that UFOs are visiting all the time

0:00:35.310,0:00:37.352
and the reports are just being covered up,

0:00:37.376,0:00:39.952
but honestly, they aren't very convincing.

0:00:40.508,0:00:42.106
But that leaves a real riddle.

0:00:42.879,0:00:45.269
In the past year,[br]the Kepler space observatory

0:00:45.293,0:00:49.060
has found hundreds of planets[br]just around nearby stars,

0:00:49.084,0:00:50.935
and if you extrapolate that data,

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it looks like there could be[br]half a trillion planets

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just in our own galaxy.

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If any one in 10,000 has conditions[br]that might support a form of life,

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that's still 50 million possible[br]life-harboring planets

0:01:04.823,0:01:06.378
right here in the Milky Way.

0:01:07.074,0:01:08.320
So here's the riddle.

0:01:08.853,0:01:10.290
Our Earth didn't form

0:01:10.314,0:01:13.294
until about 9 billion years[br]after the Big Bang.

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Countless other planets in our galaxy[br]should have formed earlier

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and given life a chance to get underway

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billions or certainly[br]many millions of years

0:01:23.391,0:01:25.019
earlier than happened on Earth.

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If just a few of them[br]had spawned intelligent life

0:01:28.493,0:01:31.118
and started creating technologies,

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those technologies[br]would have had millions of years

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to grow in complexity and power.

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On Earth,

0:01:39.394,0:01:41.984
we've seen how dramatically[br]technology can accelerate

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in just 100 years.

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In millions of years,[br]an intelligent alien civilization

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could easily have spread out[br]across the galaxy,

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perhaps creating giant[br]energy-harvesting artifacts,

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or fleets of colonizing spaceships,

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or glorious works of art[br]that fill the night sky.

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At the very least, you'd think[br]they'd be revealing their presence,

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deliberately or otherwise,

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through electromagnetic signals[br]of one kind or another.

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And yet we see no convincing[br]evidence of any of it.

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Why?

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Well, there are numerous possible answers,

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some of them quite dark.

0:02:19.931,0:02:23.002
Maybe a single,[br]superintelligent civilization

0:02:23.026,0:02:25.545
has indeed taken over the galaxy,

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and has imposed strict radio silence

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because it's paranoid[br]of any potential competitors.

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It's just sitting there[br]ready to obliterate

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anything that becomes a threat.

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Or maybe they're not that intelligent.

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Or perhaps, the evolution[br]of an intelligence

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capable of creating[br]sophisticated technology

0:02:45.863,0:02:47.639
is far rarer than we've assumed.

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After all,

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it's only happened once on Earth

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in 4 billion years.

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Maybe even that was incredibly lucky.

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Maybe we are the first[br]such civilization in our galaxy.

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Or, perhaps, civilization carries with it

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the seeds of its own destruction

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through the inability to control[br]the technologies it creates.

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But there are numerous[br]more hopeful answers.

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For a start, we're not looking that hard,

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and we're spending a pitiful[br]amount of money on it.

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Only a tiny fraction[br]of the stars in our galaxy

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have really been looked at closely[br]for signs of interesting signals.

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And perhaps, we're not looking[br]the right way.

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Maybe as civilizations develop,

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they quickly discover[br]communication technologies

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far more sophisticated and useful[br]than electromagnetic waves.

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Maybe all the action takes place

0:03:38.737,0:03:42.087
inside the mysterious[br]recently discovered dark matter,

0:03:42.111,0:03:43.534
or dark energy,

0:03:43.558,0:03:46.364
that appear to account[br]for most of the universe's mass.

0:03:47.742,0:03:50.535
Or maybe we're looking at the wrong scale.

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Perhaps intelligent civilizations[br]come to realize

0:03:53.467,0:03:56.537
that life is ultimately just complex[br]patterns of information

0:03:56.561,0:03:58.752
interacting with each other[br]in a beautiful way,

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and that can happen[br]more efficiently at a small scale.

0:04:01.847,0:04:06.243
So just as on Earth, clunky stereo systems[br]have shrunk to beautiful, tiny iPods,

0:04:06.267,0:04:08.032
maybe intelligent life itself,

0:04:08.056,0:04:10.492
in order to reduce its footprint[br]on the environment,

0:04:10.516,0:04:12.125
has turned itself microscopic,

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so the Solar System[br]might be teeming with aliens,

0:04:14.461,0:04:16.103
and we're just not noticing them.

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Maybe the very ideas in our heads[br]are a form of alien life.

0:04:19.998,0:04:22.389
Well, okay, that's a crazy thought.

0:04:22.413,0:04:24.116
The aliens made me say it.

0:04:24.982,0:04:28.828
But it is cool that ideas do seem[br]to have a life all of their own,

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and that they outlive their creators.

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Maybe biological life[br]is just a passing phase.

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Well, within the next 15 years,

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we could start seeing[br]real spectroscopic information

0:04:42.723,0:04:44.106
from promising nearby planets

0:04:44.130,0:04:46.720
that will reveal just how[br]life-friendly they might be.

0:04:47.055,0:04:48.205
And meanwhile SETI,

0:04:48.229,0:04:50.721
the Search for[br]Extra-Terrestrial Intelligence,

0:04:50.745,0:04:52.672
is now releasing its data to the public

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so that millions of citizen scientists,[br]maybe including you,

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can bring the power of the crowd[br]to join the search.

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And here on Earth,[br]amazing experiments are being done

0:05:02.015,0:05:03.976
to try to create life from scratch,

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life that might be very different[br]from the DNA forms we know.

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All of this will help us understand

0:05:10.204,0:05:12.378
whether the universe is teeming with life

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or, whether indeed,

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it's just us.

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Either answer, in its own way,

0:05:20.763,0:05:22.995
is awe-inspiring,

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because even if we are alone,

0:05:25.692,0:05:28.168
the fact that we think and dream,

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and ask these questions

0:05:30.057,0:05:32.677
might yet turn out to be[br]one of the most important facts

0:05:32.701,0:05:33.903
about the universe.

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And I have one more piece[br]of good news for you.

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The quest for knowledge[br]and understanding never gets dull.

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It doesn't. It's actually the opposite.

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The more you know,

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the more amazing the world seems.

0:05:46.301,0:05:49.746
And it's the crazy possibilities,[br]the unanswered questions,

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that pull us forward.

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So, stay curious.