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TEDxBoulder 2011

Phil Plait: How to defend Earth from asteroids

Filmed:

What's six miles wide and can end civilization in an instant? An asteroid -- and there are lots of them out there. With humor and great visuals, Phil Plait enthralls the TEDxBoulder audience with all the ways asteroids can kill, and what we must do to avoid them. (Filmed at TEDxBoulder.)

- Astronomer
Phil Plait blogs at Bad Astronomy, where he deconstructs misconceptions and explores the wonder of the universe. Full bio

I want to talk to you about something
00:16
kind of big.
00:18
We'll start here.
00:21
65 million years ago
00:24
the dinosaurs had a bad day.
00:27
(Laughter)
00:30
A chunk of rock six miles across,
00:33
moving something like 50 times
00:36
the speed of a rifle bullet,
00:38
slammed into the Earth.
00:40
It released its energy all at once,
00:42
and it was an explosion that was
00:44
mind-numbing.
00:46
If you took every nuclear weapon ever built
00:48
at the height of the Cold War,
00:50
lumped them together and blew them up
00:52
at the same time,
00:54
that would be one one-millionth
00:56
of the energy released at that moment.
00:58
The dinosaurs had a really bad day.
01:02
Okay?
01:05
Now, a six-mile-wide rock is very large.
01:07
We all live here in Boulder.
01:09
If you look out your window and you can see
01:11
Long's Peak, you're probably familiar with it.
01:13
Now, scoop up Long's Peak, and put it out
01:15
in space.
01:17
Take Meeker, Mt. Meeker. Lump that in there,
01:19
and put that in space as well,
01:21
and Mt. Everest, and K2,
01:23
and the Indian peaks.
01:25
Then you're starting to get an idea of
01:27
how much rock we're talking about, okay?
01:29
We know it was that big because of
01:31
the impact it had and the crater it left.
01:33
It hit in what we now know as Yucatan,
01:35
the Gulf of Mexico.
01:37
You can see here, there's the
01:39
Yucatan Peninsula, if you recognize Cozumel
01:41
off the east coast there.
01:43
Here is how big of a crater was left.
01:45
It was huge. To give you a sense of the scale,
01:48
okay, there you go. The scale here is
01:50
50 miles on top, a hundred kilometers
01:52
on the bottom. This thing was
01:54
300 kilometers across -- 200 miles --
01:56
an enormous crater that excavated out
01:58
vast amounts of earth that splashed around
02:00
the globe and set fires all over the planet,
02:03
threw up enough dust to block out the sun.
02:06
It wiped out 75 percent of all species
02:09
on Earth.
02:11
Now, not all asteroids are that big.
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Some of them are smaller.
02:16
Here is one that came in
02:18
over the United States
02:21
in October of 1992.
02:23
It came in on a Friday night.
02:25
Why is that important?
02:27
Because back then, video cameras were
02:29
just starting to become popular, and people
02:31
would bring them, parents would bring them,
02:33
to their kids' football games to film their kids
02:35
play football. And since this came in on a Friday,
02:37
they were able to get this great footage
02:40
of this thing breaking up as it came in
02:42
over West Virgina, Maryland, Pennsylvania
02:44
and New Jersey until it did that
02:46
to a car in New York.
02:48
(Laughter)
02:50
Now, this is not a 200-mile-wide crater,
02:52
but then again you can see the rock
02:55
which is sitting right here,
02:57
about the size of a football, that hit
02:59
that car and did that damage.
03:01
Now this thing was probably about the size
03:03
of a school bus when it first came in.
03:05
It broke up through atmospheric pressure,
03:07
it crumbled, and then the pieces fell apart
03:09
and did some damage.
03:11
Now, you wouldn't want that falling on your foot
03:13
or your head, because it would do that to it.
03:15
That would be bad.
03:17
But it won't wipe out, you know, all life
03:19
on Earth, so that's fine. But it turns out,
03:21
you don't need something six miles across
03:23
to do a lot of damage.
03:26
There is a median point between tiny rock
03:28
and gigantic rock, and in fact, if any of you
03:30
have ever been to near Winslow, Arizona,
03:32
there is a crater in the desert there that is
03:35
so iconic that it is actually called Meteor Crater.
03:38
To give you a sense of scale, this is about a mile wide.
03:42
If you look up at the top, that's a parking lot,
03:45
and those are recreational vehicles right there.
03:48
So it's about a mile across, 600 feet deep.
03:51
The object that formed this was probably about
03:54
30 to 50 yards across, so roughly the size
03:57
of Mackey Auditorium here.
04:00
It came in at speeds that were tremendous,
04:03
slammed into the ground, blew up,
04:06
and exploded with the energy of roughly
04:08
a 20-megaton nuclear bomb --
04:10
a very hefty bomb.
04:12
This was 50,000 years ago, so it may have
04:14
wiped out a few buffalo or antelope,
04:16
or something like that out in the desert,
04:18
but it probably would not have caused
04:21
global devastation.
04:23
It turns out that these things don't have to
04:25
hit the ground to do a lot of damage.
04:27
Now, in 1908, over Siberia, near the
04:30
Tunguska region -- for those of you who are
04:32
Dan Aykroyd fans and saw "Ghostbusters,"
04:34
when he talked about the greatest cross-dimensional rift
04:36
since the Siberia blast of 1909, where he got
04:39
the date wrong, but that's okay. (Laughter)
04:42
It was 1908. That's fine. I can live with that.
04:44
(Laughter)
04:47
Another rock came into the Earth's atmosphere
04:50
and this one blew up above the ground, several
04:53
miles up above the surface of the Earth.
04:55
The heat from the explosion set fire to the
04:58
forest below it, and then the shock wave
05:01
came down and knocked down trees for
05:04
hundreds of square miles, okay?
05:06
This did a huge amount of damage.
05:09
And again, this was a rock probably roughly
05:11
the size of this auditorium that we're sitting in.
05:13
In Meteor Crater it was made of metal,
05:15
and metal is much tougher, so it made it
05:17
to the ground.
05:19
The one over Tunguska was probably made
05:21
of rock, and that's much more crumbly, so it
05:23
blew up in the air. Either way, these are
05:25
tremendous explosions, 20 megatons.
05:27
Now, when these things blow up, they're not
05:30
going to do global ecological damage.
05:32
They're not going to do something like
05:35
the dinosaur-killer did.
05:37
They're just not big enough.
05:39
But they will do global economic damage,
05:41
because they don't have to hit, necessarily,
05:43
to do this kind of damage.
05:45
They don't have to do global devastation.
05:47
If one of these things were to hit
05:49
pretty much anywhere, it would cause a panic.
05:51
But if it came over a city, an important city --
05:53
not that any city is more important than others,
05:55
but some of them we depend on them more
05:57
on the global economic basis -- that could do
05:59
a huge amount of damage to us
06:02
as a civilization.
06:05
So, now that I've scared the crap out of you ...
06:07
(Laughter)
06:10
what can we do about this? All right?
06:12
This is a potential threat.
06:14
Let me note that we have not had
06:16
a giant impact like the dinosaur-killer
06:18
for 65 million years. They're very rare.
06:20
The smaller ones happen more often, but
06:23
probably on the order of a millennium,
06:26
every few centuries or every few thousand
06:28
years, but it's still something to be aware of.
06:30
Well, what do we do about them?
06:33
The first thing we have to do is find them.
06:35
This is an image of an asteroid that passed
06:37
us in 2009.
06:39
It's right here.
06:41
But you can see that it's extremely faint.
06:43
I don't even know if you can see that
06:45
in the back row. These are just stars.
06:47
This is a rock that was about 30 yards across,
06:49
so roughly the size of the ones that blew up
06:51
over Tunguska and hit Arizona 50,000 years ago.
06:53
These things are faint.
06:56
They're hard to see, and the sky is really big.
06:58
We have to find these things first.
07:00
Well the good news is, we're looking for them.
07:02
NASA has devoted money to this.
07:04
The National Science Foundation, other
07:06
countries are very interested in doing this.
07:08
We're building telescopes that are looking
07:10
for the threat. That's a great first step,
07:12
but what's the second step? The second step
07:14
is that we see one heading toward us,
07:16
we have to stop it. What do we do?
07:18
You've probably heard about the asteroid
07:20
Apophis. If you haven't yet, you will.
07:22
If you've heard about the Mayan 2012
07:25
apocalypse, you're going to hear about Apophis,
07:27
because you're keyed in to all the doomsday
07:29
networks anyway.
07:31
Apophis is an asteroid that was discovered in 2004.
07:34
It's roughly 250 yards across, so it's
07:37
pretty big -- big size, you know,
07:40
bigger than a football stadium -- and it's going to
07:42
pass by the Earth in April of 2029.
07:44
And it's going to pass us so close that it's
07:47
actually going to come underneath
07:49
our weather satellites.
07:51
The Earth's gravity is going to bend the orbit
07:53
of this thing so much that if it's just right,
07:55
if it passes through this region of space,
07:58
this kidney bean-shaped region called
08:01
the keyhole, the Earth's gravity will bend it
08:03
just enough that seven years later
08:05
on April 13, which is a Friday, I'll note,
08:07
in the year 2036 ... (Laughter)
08:09
-- you can't plan that kind of stuff --
08:12
Apophis is going to hit us. And it's
08:15
250 meters across, so it would do
08:17
unbelievable damage.
08:19
Now the good news is that the odds of it
08:21
actually passing through this keyhole and
08:23
hitting us next go-around are one in a million,
08:25
roughly -- very, very low odds, so I personally
08:27
am not lying awake at night worrying about this at all.
08:29
I don't think Apophis is a problem.
08:31
In fact, Apophis is a blessing in disguise,
08:33
because it woke us up to the dangers
08:35
of these things.
08:37
This thing was discovered just a few years
08:39
ago and could hit us a few years from now.
08:41
It won't, but it gives us a chance to study
08:43
these kinds of asteroids. We didn't really
08:45
necessarily understand these keyholes, and
08:47
now we do and it turns out
08:49
that's really important, because how do you
08:51
stop an asteroid like this?
08:53
Well, let me ask you, what happens if you're
08:55
standing in the middle of the road and a car's
08:57
headed for you? What do you do? You do this.
08:59
Right? Move. The car goes past you.
09:01
But we can't move the Earth, at least
09:03
not easily, but we can move a small asteroid.
09:05
And it turns out, we've even done it.
09:07
In the year 2005, NASA launched a probe
09:09
called Deep Impact, which slammed into --
09:12
slammed a piece of itself into the nucleus of a comet.
09:15
Comets are very much like asteroids.
09:18
The purpose wasn't to push it out of the way.
09:20
The purpose was to make a crater to excavate
09:22
the material and see what was underneath
09:24
the surface of this comet, which we learned
09:26
quite a bit about.
09:28
We did move the comet a little tiny bit,
09:30
not very much, but that wasn't the point.
09:32
However, think about this.
09:34
This thing is orbiting the sun at
09:36
10 miles per second, 20 miles per second.
09:38
We shot a space probe at it and hit it. Okay?
09:40
Imagine how hard that must be, and we did it.
09:42
That means we can do it again.
09:45
If we need, if we see an asteroid that's coming
09:48
toward us, and it's headed right for us,
09:50
and we have two years to go, boom! We hit it.
09:52
You can try to -- you know, if you watch
09:55
the movies, you might think about,
09:57
why don't we use a nuclear weapon?
09:59
It's like, well, you can try that, but the problem is timing.
10:01
You shoot a nuclear weapon at this thing,
10:03
you have to blow it up within a few milliseconds
10:05
of tolerance or else you'll just miss it.
10:07
And there are a lot of other problems
10:09
with that. It's very hard to do.
10:11
But just hitting something? That's pretty easy.
10:13
I think even NASA can do that,
10:15
and they proved that they can. (Laughter)
10:17
The problem is, what happens if you hit
10:19
this asteroid, you've changed the orbit,
10:21
you measure the orbit and then you find out,
10:23
oh, yeah, we just pushed it into a keyhole,
10:25
and now it's going to hit us in three years.
10:27
Well, my opinion is, fine. Okay?
10:29
It's not hitting us in six months. That's good.
10:31
Now we have three years to do something else.
10:33
And you can hit it again. That's kind of
10:36
ham-fisted. You might just push it into a third
10:38
keyhole or whatever, so you don't do that.
10:40
And this is the part, it's the part I just love.
10:42
(Laughter)
10:46
After the big macho "Rrrrrrr BAM! We're
10:48
gonna hit this thing in the face,"
10:50
then we bring in the velvet gloves.
10:52
(Laughter)
10:55
There's a group of scientists and engineers
10:58
and astronauts and they call themselves
11:00
The B612 Foundation. For those of you
11:02
who've read "The Little Prince,"
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you understand that reference, I hope. The little prince
11:06
who lived on an asteroid, it was called B612.
11:08
These are smart guys -- men and women --
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astronauts, like I said, engineers.
11:12
Rusty Schweickart, who was an Apollo 9
11:14
astronaut, is on this. Dan Durda, my friend
11:16
who made this image, works here at
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Southwest Research Institute in Boulder,
11:20
on Walnut Street. He created this image for this,
11:22
and he's actually one of the astronomers
11:24
who works for them. If we see an asteroid
11:26
that's going to hit the Earth and we have
11:28
enough time, we can hit it to move it into
11:30
a better orbit. But then what we do is we launch
11:33
a probe that has to weigh a ton or two.
11:36
It doesn't have to be huge -- couple of tons,
11:38
not that big -- and you park it near the asteroid.
11:41
You don't land on it, because these things are
11:44
tumbling end over end. It's very hard to land on them.
11:46
Instead you get near it.
11:48
The gravity of the asteroid pulls on the probe,
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and the probe has a couple of tons of mass.
11:52
It has a little tiny bit of gravity, but it's enough
11:55
that it can pull the asteroid, and you have your
11:57
rockets set up, so you can -- oh, you can barely
11:59
see it here, but there's rocket plumes -- and you
12:01
basically, these guys are connected by their
12:03
own gravity, and if you move the probe very
12:05
slowly, very, very gently, you can very easily
12:08
finesse that rock into a safe orbit.
12:12
You can even put in orbit around the Earth
12:15
where we could mine it, although that's a
12:17
whole other thing. I won't go into that.
12:19
(Laughter)
12:21
But we'd be rich!
12:23
(Laughter)
12:25
So think about this, right?
12:30
There are these giant rocks flying out there,
12:32
and they're hitting us, and they're doing
12:34
damage to us, but we've figured out how to do
12:36
this, and all the pieces are in place to do this.
12:38
We have astronomers in place with telescopes
12:41
looking for them. We have smart people,
12:43
very, very smart people, who are concerned
12:45
about this and figuring out how to fix the
12:47
problem, and we have the technology to do this.
12:49
This probe actually can't use chemical rockets.
12:52
Chemical rockets provide too much thrust, too
12:54
much push. The probe would just shoot away.
12:56
We invented something called an ion drive,
12:58
which is a very, very, very low-thrust engine.
13:00
It generates the force a piece of paper would
13:03
have on your hand, incredibly light,
13:05
but it can run for months and years,
13:07
providing that very gentle push.
13:10
If anybody here is a fan of the original "Star Trek,"
13:13
they ran across an alien ship that had
13:15
an ion drive, and Spock said,
13:17
"They're very technically sophisticated.
13:19
They're a hundred years ahead of us with this drive."
13:21
Yeah, we have an ion drive now. (Laughter)
13:23
We don't have the Enterprise, but
13:25
we've got an ion drive now.
13:27
(Applause)
13:29
Spock.
13:32
(Laughter)
13:34
So ...
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that's the difference, that's the difference
13:39
between us and the dinosaurs.
13:41
This happened to them.
13:43
It doesn't have to happen to us.
13:45
The difference between the dinosaurs and us
13:47
is that we have a space program
13:50
and we can vote,
13:52
and so we can change our future.
13:54
(Laughter)
13:57
We have the ability to change our future.
13:58
65 million years from now,
14:01
we don't have to have our bones
14:03
collecting dust in a museum.
14:05
Thank you very much.
14:07
(Applause)
14:09

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About the Speaker:

Phil Plait - Astronomer
Phil Plait blogs at Bad Astronomy, where he deconstructs misconceptions and explores the wonder of the universe.

Why you should listen

Phil Plait is the Bad Astronomer. Not a bad astronomer, but a blogger for Slate who debunks myths and misconceptions about astronomy -- and also writes about the beauty, wonder and importance of fundamental research.

He worked for six years on the Hubble Space Telescope, and directed public outreach for the Fermi Gamma-ray Space Telescope. He is a past president of the James Randi Educational Foundation, and was the host of Phil Plait's Bad Universe, a documentary series on the Discovery Channel.

Read more from Phil Plait in the Huffington Post's special TEDWeekends feature, "Asteroids: Getting Ready" >>

More profile about the speaker
Phil Plait | Speaker | TED.com