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 trillion 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,
superintelligent 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. 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 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-friendly 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.
