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Somewhere out there in that vast universe
there must surely be countless other planets teeming with life,
but why don't we see any evidence of it?
Well, this is the famous question asked by Enrico Fermi in 1950:
"Where is everybody?"
Conspiracy theorists claim that UFOs are visiting all the time
and the reports are just being covered up,
but honestly, they aren't very convincing.
But that leaves a real riddle.
In the past year, the Kepler space observatory has found
hundreds of planets just around nearby stars,
and if you extrapolate that data,
it looks like there could be half a trillions planets
just in our own galaxy.
If any one in 10,000 has conditions
that might support a form of life, that's still
50 million possible life-harboring planets
right here in the Milky Way.
So here's the riddle.
Our Earth didn't form until about 9 billion years after the Big Bang.
Countless other planets in our galaxy
should have formed earlier and given life a chance to get underway
billions, or certainly many millions, of years
earlier than happened on Earth.
If just a few of them had spawned intelligent life
and started creating technologies,
those technologies would have had millions of years
to grow in complexity and power.
On Earth,
we've seen how dramatically
technology can accelerate in just 100 years.
In millions of years, an intelligent alien civilization
could easily have spread out across the galaxy,
perhaps creating giant energy-harvesting artifacts
or fleets of colonizing spaceships
or glorious works of art that fill the night sky.
At the very least, you'd think they'd be revealing their presence,
deliberately or otherwise,
through electromagnetic signals
of one kind or another. And yet we see no convincing evidence of any of it.
Why?
Well, there are numerous possible answers,
some of them quite dark.
Maybe a single, super-intelligent civilization
has indeed taken over the galaxy,
and has imposed strict radio silence
because it's paranoid of any potential competitors.
It's just sitting there ready to obliterate
anything that becomes a threat.
Or maybe they're not that intelligent,
or perhaps the evolution of an intelligence
capable of creating sophisticated technology
is far rarer than we've assumed.
After all, it's only happened once on Earth in 4 billion years.
Maybe even that was incredibly lucky.
Maybe we are the first such civilization in our galaxy.
Or perhaps civilization carries with it
the seeds of its own destruction
through the inability to control the technologies it creates.
But there are numerous more hopeful answers.
I mean, for a start, we're not looking that hard. And we're spending a pitiful amount of money on it.
Only a tiny fraction of the stars in our galaxy
have really been looked at closely for signs of interesting signals.
And perhaps we're not looking the right way.
Maybe as civilizations develop,
they quickly discover communication technologies
far more sophisticated and useful than electromagnetic waves.
Maybe all the action takes place
inside the mysterious recently discovered dark matter,
or dark energy, that appear to account for most of the universe's mass.
Or maybe we're looking at the wrong scale.
Perhaps intelligent civilizations come to realize
that life is ultimately just complex patterns of information
interacting with each other in a beautiful way,
and that that can happen more efficiently at a small scale.
So, just as on Earth clunky stereo systems
have shrunk to beautiful, tiny iPods, maybe intelligent life itself,
in order to reduce its footprint on the environment,
has turned itself microscopic,
so the Solar System might be teeming with aliens, and we're just not noticing them.
Maybe the very ideas in our heads are a form of alien life.
Well, okay, that's a crazy thought.
The aliens made me say it.
But it is cool that ideas do seem to have a life all of their own
and that they outlive their creators.
Maybe biological life is just a passing phase.
Well, within the next 15 years,
we could start seeing real spectroscopic information
from promising nearby planets that will reveal just how life-ready they might be.
And meanwhile SETI, the Search for Extra-Terrestrial Intelligence,
is now releasing its data to the public
so that millions of citizen scientists, maybe including you,
can bring the power of the crowd to join the search.
And here on Earth, amazing experiments are being done
to try to create life from scratch,
life that might be very different from the DNA forms we know.
All of this will help us understand
whether the universe is teeming with life
or whether, indeed, it's just us.
Either answer, in its own way,
is awe-inspiring,
because even if we are alone,
the fact that we think and dream and ask these questions
might yet turn out to be one of the most important facts about the universe.
And I have one more piece of good news for you.
The quest for knowledge and understanding never gets dull.
It doesn't. It's actually the opposite. The more you know,
the more amazing the world seems.
And it's the crazy possibilities, the unanswered questions,
that pull us forward. So stay curious.
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【TED-Ed】 為什麼我們就是無法看到外星人存在的線索呢? Why can't we see evidence of alien life? - Chris Anderson

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VoiceTube 發佈於 2013 年 3 月 23 日
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