Education and Communications

Everything, The Universe…And Life: Crash Course Astronomy #46

Hey everyone. Phil Plait here with Crash Course
Astronomy…for one last time. We’ve come a long way together, you and
I, from the banging beginning of the Universe to its far, far, future; from subatomic scales
to superclusters of galaxies. We’ve watched the sky, mapped how it looks to us from the
ground, and then sailed out into the black to investigate its denizens up close. And — one of my favorite parts — we’ve
seen how human beings, people like you and me, have worked over the centuries to figure
all this stuff out. We’re pretty clever for a bunch of apes who only recently figured
out how to walk upright. But after all the topics we’ve covered here,
all the space we’ve explored, there’s still one more thing I want to talk about
that didn’t quite fit anywhere else in the series. It’s yet another fascination of
mine, and judging from talking to so many people over the years, it’s something important
to a lot of us. Which doesn’t surprise me. I think asking
this question is a deeply human thing to do, perhaps ironically part of what makes us who
we are. And it’s simply put, too. Are we alone? When people ask me what field of
astronomy is the most exciting right now,
I don’t even hesitate: Exoplanets. I talked about these back in Episode 27; alien worlds,
planets orbiting other stars. The first were discovered in 1992, and now we know of THOUSANDS,
with many thousands more awaiting confirmation. Most of these exoplanets are giants, far more
massive than Earth and likely to have very thick atmospheres like Neptune or Jupiter.
They also orbit so close to their host stars that they’re hotter than Venus. But as our techniques got better, we started
finding smaller planets farther out, and now we have a short list of planets that could
very well be Earth-like in many ways. Close to our size, density, temperature, surface
gravity…but that’s all we know. With our current abilities, these planets are on the
thin bleeding edge of what we can observe. Do they have atmospheres? If they do, do they
have a copious amount of oxygen in their atmospheres? That would be a critical observation: In Earth-like
atmospheres, oxygen molecules are extremely reactive chemically, and won’t last long
without being replenished. The easiest way we know to do that is biology. It’s not the only way, so it’s no guarantee
— there are some other processes that can produce and maintain oxygen in a planet’s
atmosphere — but seeing it would be a good sign, and there are other fragile molecules
that, if detected, would strengthen the idea of biological activity. Detecting the presence of O2 in an exoplanet’s
atmosphere is just tantalizingly out of reach right now. We can almost do it. We may not have to wait too much longer, though.
The James Webb Space Telescope, the successor to Hubble, is a gigantic infrared space telescope
currently scheduled to launch in late 2018. It should be able to tease apart the light
from some of the nearer and brighter of these distant worlds and look for the signature of oxygen,
as well as other biologically produced gases. Still, finding them in an Earth-sized planet
may be beyond James Webb, too. NASA has studies looking into space telescopes specifically designed
to look for alien Earths, but that’s a ways off yet. But think of it. When I was a kid there were
nine planets — OK, eight. Now we have thousands, and they’re not at all what we expected.
The diversity of worlds is stunning, with some hot, some cold, some big, some little,
some in solar systems so compact they can fit five planets inside the orbit of Mercury,
and some with planets far-flung. Nature is more clever than we are. Sometimes,
I think that if something’s possible to do, Nature’s done it somewhere. But what’s more amazing to me is that we
now think that most — MOST — stars in the galaxy have planets. Given that multiple
planets orbiting each star is common, that means there are likely more planets than stars
in our galaxy. And there are over 200 billion stars in our
galaxy. I also want to point out that we see traces
of life on Earth going back nearly 4 billion years. There was certainly life before that, but didn’t
leave evidence we can find so many eons later. That timing is interesting: This means life
existed on Earth not too long after it cooled enough to have liquid water on its surface.
That in turn strongly implies getting life started on planets is easy. The ancient Earth
was a tough place to live, yet life took hold within a few hundred million years after it
formed. Put this all together, and what do you get? If the galaxy is filled with planets and life
gets its start so easily, the galaxy may be filled with life! We need more evidence, more
observations, but that’s the way the numbers lean. Mind you, I’m not talking about intelligent
life — just life itself. But still, that’s just about the coolest thing I can imagine. So, are they out there? This is a question I am always asked when
I give public talks. “Do you believe in UFOs and aliens?” My answer is always the
same: No, and yes. Given what I just said, it seems inevitable
that life exists out there in the Universe. The conditions for life to arise are easy
to make, and there are a lot of chances for it out there. On the other hand, for most
of Earth’s history the most advanced life was basically algae. Complex life, life capable
of intelligent thought, is a relatively recent development. So alien life, sure. But aliens sophisticated
enough that they can come here to pose for blurry photos, abduct people, and slice up
cows? I’m not buying it. The evidence just isn’t there, and now that so many people
walk around with cameras, we see even fewer reports of mysterious lights in the sky than
we used to – or, at least, most of these lights seen are explainable. Wedding lanterns,
balloons, Venus, meteors, the Moon, satellites, and so on. I’ll note astronomers are watching
the skies literally all the time. If UFOs were real WE’D be reporting the vast majority
of them! That doesn’t mean aliens aren’t out there,
though. Space is big – remember, folks, that’s why we call it “space” – and
getting here is a huge pain in the butt…or whatever aliens use to excrete waste matter. It takes a vast amount of energy to accelerate
a spaceship to the speeds needed to travel to other planets. Even then, that’s slow
compared to the speed of light. Not only that, light is easy to make. You don’t need a
lot of super sophisticated tech to make radio waves, and it’s easy to embed a lot of information
in them. After all, that’s how radios and wifi work. So why go to all the trouble of meeting other
life forms in person when you can chat via radio? This is the premise behind SETI. The Search for Extraterrestrial Intelligence,
that is. This is based on a simple idea: If aliens are out there, it’s easier to stay
home and talk via radio than through the interstellar version of the Pony Express. There are a lot of assumptions built into
this idea, of course. One is that, well, aliens exist. The next is that they’re much more
technologically advanced than we are. But that makes sense. Any aliens that don’t
have tech can’t communicate with us, so they don’t play into this. And we know how
quickly our technology advances; we’re just starting out and already have some pretty cool gizmos.
Give us a hundred years, a thousand, and where will we be? The Earth is over 4.5 billion years old, but
we’ve detected exoplanets far older than that. Life there might be that much more advanced
than we are. They might communicate with each other using neutrinos, or ripples in spacetime,
or quantum entanglement, or some method we can’t even imagine. But if they’re interested
in finding life in the galaxy that’s just starting to get their technological legs under
them, radio waves are the way to go. Even primitive societies like ours use radio
waves, and they can travel for thousands of light years. Aliens could broadcast radio
waves across the galaxy, or target likely stars, or wait for us to make enough noise
— and for those waves to travel outward at the speed of light long enough to reach a
listening post — and then aim a transmitter at us. So the folks at SETI scan the skies at various
radio wavelengths, hoping to hear a signal. So far, nothing yet. But they don’t despair. My friend, the astronomer
Seth Shostak, is a SETI scientist. He’s been doing this for years, and recently made
a bold, but logical claim. SETI tech is advancing rapidly, and they’re getting so good at
listening that they’ll be able to scan billions of stars. He predicts that, if anyone out
there is broadcasting, we’ll pick up the signal in the next 20 years. If we don’t, then, given the statistics,
it may very well mean that we’re alone in the galaxy. Or aliens might exist, but they’re
not broadcasting. Or, of course, that perhaps there’s another flaw in the chain in of
logic that we’ve missed. Either way – if they detect a signal, or
they don’t – the resulting conclusion is at least interesting, and at most terribly
profound. And it’s only our first, logical step in attempting to look for life Out There. I love astronomy. Maybe you’ve figured that
out over these past 46 episodes. I love it for so many reasons: The beauty, the grand
nature of it, the incredible vistas, the depth of the wonder and science of it. When I was little, the subtle profundity of
the questions related to astronomy were perhaps beyond me. But even then, the questions themselves
provoked a sense of wonder, of awe, so much so that even as a little kid, I could be stirred
by them. And now, as an adult, I grasp these questions
better. How did we come to be? What was it like in those first few fractions of a second
after the Big Bang? Is ours the only cosmos out there, or are we part of a much larger
multiverse, riding along with other Universes like bubbles in a sea of multidimensional
foam? What is the nature of stars? How do planets
form? Are there other Earths?
Are we alone? These are some of the grandest questions we
can ask, and in one shape or another have been asked by humans for thousands of years.
These are also questions that were once only in the purview of religion and philosophy,
but now we have observations to pursue them, evidence to back up our conditional answers. Because of astronomy, because of SCIENCE,
we now stand on the edge of understanding, our cleverness and brilliance having taken
us to the point where these questions, finally, have an answer we can almost touch. And the best part? As we investigate, as we
peek around the next corner, as we climb over the next hill, we find those answers… and
they reveal a host of more questions. The exploration never ends. There’s always
something else to discover. And that, THAT, is why I love astronomy. And so, it is not out of arrogance, not out
of false smugness, but out of pride and understanding hard-won by a legion of scientists who came
before me, who came before all of us, that I can now say: Let’s go explore the Universe. Thank you for watching. And, if I may indulge myself: my personal thanks to
Derek Muller of Veritasium for his hand in getting me set up with this dream gig, and course to Hank Green,
who wants to make the world a better place, and is doing a fine job at it. And to all of you who
have watched Crash Course Astronomy: Don’t forget to be awesome. Crash Course Astronomy is produced in association
with PBS Digital Studios. Head over to their YouTube channel to catch even more awesome
videos. This episode was written by me, Phil Plait. The script was edited by Blake de Pastino,
and our consultant is Dr. Michelle Thaller. It was directed by Nicholas Jenkins, edited
by Nicole Sweeney, the sound designer is Michael Aranda, and the graphics team is Thought Café.
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