Why Earth may someday look like Mars | Anjali Tripathi | TEDxBeaconStreet
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0:17 - 0:20So when you look out
at the stars at night, -
0:20 - 0:22it's amazing what you can see.
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0:22 - 0:23It's beautiful.
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0:23 - 0:26But what's more amazing
is what you can't see, -
0:26 - 0:28because what we know now
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0:28 - 0:31is that around every star
or almost every star, -
0:31 - 0:32there's a planet,
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0:32 - 0:33or probably a few.
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0:34 - 0:37So what this picture isn't showing you
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0:37 - 0:39are all the planets that we know about
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0:39 - 0:40out there in space.
-
0:41 - 0:44But when we think about planets,
we tend to think of faraway things -
0:44 - 0:46that are very different from our own.
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0:46 - 0:48But here we are on a planet,
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0:48 - 0:51and there are so many things
that are amazing about Earth -
0:51 - 0:56that we're searching far and wide
to find things that are like that. -
0:56 - 0:59And when we're searching,
we're finding amazing things. -
0:59 - 1:03But I want to tell you
about an amazing thing here on Earth. -
1:03 - 1:06And that is that every minute,
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1:06 - 1:09400 pounds of hydrogen
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1:09 - 1:11and almost seven pounds of helium
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1:11 - 1:14escape from Earth into space.
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1:15 - 1:19And this is gas that is going off
and never coming back. -
1:20 - 1:23So hydrogen, helium and many other things
-
1:23 - 1:26make up what's known
as the Earth's atmosphere. -
1:26 - 1:29The atmosphere is just these gases
that form a thin blue line -
1:30 - 1:33that's seen here from
the International Space Station, -
1:33 - 1:35a photograph that some astronauts took.
-
1:36 - 1:39And this tenuous veneer around our planet
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1:39 - 1:41is what allows life to flourish.
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1:41 - 1:44It protects our planet
from too many impacts, -
1:44 - 1:46from meteorites and the like.
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1:46 - 1:50And it's such an amazing phenomenon
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1:50 - 1:53that the fact that it's disappearing
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1:53 - 1:56should frighten you,
at least a little bit. -
1:56 - 2:00So this process is something that I study
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2:00 - 2:02and it's called atmospheric escape.
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2:03 - 2:08So atmospheric escape
is not specific to planet Earth. -
2:08 - 2:11It's part of what it means
to be a planet, if you ask me, -
2:11 - 2:16because planets, not just here on Earth
but throughout the universe, -
2:16 - 2:18can undergo atmospheric escape.
-
2:18 - 2:24And the way it happens actually tells us
about planets themselves. -
2:24 - 2:27Because when you think
about the solar system, -
2:27 - 2:29you might think about this picture here.
-
2:30 - 2:34And you would say, well,
there are eight planets, maybe nine. -
2:34 - 2:36So for those of you
who are stressed by this picture, -
2:36 - 2:37I will add somebody for you.
-
2:37 - 2:39(Laughter)
-
2:39 - 2:42Courtesy of New Horizons,
we're including Pluto. -
2:42 - 2:44And the thing here is,
-
2:44 - 2:46for the purposes of this talk
and atmospheric escape, -
2:46 - 2:48Pluto is a planet in my mind,
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2:48 - 2:52in the same way that planets
around other stars that we can't see -
2:52 - 2:54are also planets.
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2:54 - 2:57So fundamental characteristics of planets
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2:57 - 3:00include the fact that they are bodies
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3:01 - 3:02that are bound together by gravity.
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3:02 - 3:05So it's a lot of material
just stuck together -
3:05 - 3:06with this attractive force.
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3:07 - 3:10And these bodies are so big
and have so much gravity. -
3:10 - 3:11That's why they're round.
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3:11 - 3:13So when you look at all of these,
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3:13 - 3:14including Pluto,
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3:14 - 3:15they're round.
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3:16 - 3:19So you can see that gravity
is really at play here. -
3:19 - 3:22But another fundamental
characteristic about planets -
3:22 - 3:24is what you don't see here,
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3:24 - 3:25and that's the star,
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3:26 - 3:29the star is what all of the planets
in the solar system are orbiting around. -
3:30 - 3:34And that's fundamentally driving
atmospheric escape. -
3:35 - 3:40The reason that fundamentally stars
drive atmospheric escape from planets -
3:40 - 3:46is because stars offer planets
particles and light and heat -
3:46 - 3:49that can cause the atmospheres to go away.
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3:49 - 3:51So if you think of a hot-air balloon,
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3:51 - 3:55or you look at this picture
of lanterns in Thailand at a festival, -
3:55 - 3:58you can see that hot air
can propel gasses upward. -
3:58 - 4:01And if you have enough energy and heating,
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4:01 - 4:02which our Sun does,
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4:02 - 4:06that gas, which is so light
and only bound by gravity, -
4:06 - 4:08it can escape into space.
-
4:09 - 4:13And so this is what's actually
causing atmospheric escape -
4:13 - 4:16here on Earth and also on other planets...
-
4:16 - 4:18That interplay
between heating from the star -
4:18 - 4:22and overcoming the force
of gravity on the planet. -
4:22 - 4:24So I've told you that it happens
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4:24 - 4:28at the rate of 400 pounds
a minute for hydrogen -
4:28 - 4:30and almost seven pounds for helium.
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4:31 - 4:33But what does that look like?
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4:33 - 4:35Well, even in the '80s,
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4:35 - 4:36we took pictures of the Earth
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4:37 - 4:38in the ultraviolet
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4:38 - 4:41using NASA's Dynamic Explorer spacecraft.
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4:41 - 4:43So these two images of the Earth
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4:43 - 4:47show you what that glow
of escaping hydrogen looks like, -
4:47 - 4:48shown in red.
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4:48 - 4:52And you can also see other features
like oxygen and nitrogen -
4:52 - 4:53in that white glimmer
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4:54 - 4:56in the circle showing you the auroras
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4:56 - 4:59and also some wisps around the tropics.
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4:59 - 5:02So these are pictures
that conclusively show us -
5:02 - 5:06that our atmosphere isn't just
tightly bound to us here on Earth -
5:06 - 5:09but it's actually
reaching out far into space, -
5:10 - 5:11and at an alarming rate, I might add.
-
5:12 - 5:16But the Earth is not alone
in undergoing atmospheric escape. -
5:16 - 5:20Mars, our nearest neighbor,
is much smaller than Earth, -
5:20 - 5:24so it has much less gravity
with which to hold on to its atmosphere. -
5:24 - 5:26And so even though Mars has an atmosphere,
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5:26 - 5:28we can see it's much thinner
than the Earth's. -
5:28 - 5:30Just look at the surface.
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5:30 - 5:33You see craters indicating
that it didn't have an atmosphere -
5:33 - 5:35that could stop those impacts.
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5:35 - 5:38Also, we see that it's the "red planet,"
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5:38 - 5:40and atmospheric escape plays a role
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5:40 - 5:42in Mars being red.
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5:42 - 5:46That's because we think
Mars used to have a wetter past, -
5:46 - 5:50and when water had enough energy,
it broke up into hydrogen and oxygen, -
5:50 - 5:54and hydrogen being so light,
it escaped into space, -
5:54 - 5:56and the oxygen that was left
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5:56 - 5:58oxidized or rusted the ground,
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5:58 - 6:02making that familiar
rusty red color that we see. -
6:03 - 6:04So it's fine to look at pictures of Mars
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6:05 - 6:07and say that atmospheric escape
probably happened, -
6:07 - 6:11but NASA has a probe that's currently
at Mars called the MAVEN satellite, -
6:11 - 6:15and its actual job
is to study atmospheric escape. -
6:15 - 6:19It's the Mars Atmosphere
and Volatile Evolution spacecraft. -
6:19 - 6:23And results from it have already
shown pictures very similar -
6:23 - 6:25to what you've seen here on Earth.
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6:25 - 6:27We've long known that Mars
was losing its atmosphere, -
6:27 - 6:29but we have some stunning pictures.
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6:29 - 6:32Here, for example,
you can see in the red circle -
6:33 - 6:34is the size of Mars,
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6:34 - 6:38and in blue you can see the hydrogen
escaping away from the planet. -
6:38 - 6:42So it's reaching out more than 10 times
the size of the planet, -
6:42 - 6:45far enough away that it's
no longer bound to that planet. -
6:45 - 6:47It's escaping off into space.
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6:47 - 6:49And this helps us confirm ideas,
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6:49 - 6:52like why Mars is red,
from that lost hydrogen. -
6:53 - 6:55But hydrogen isn't
the only gas that's lost. -
6:55 - 6:58I mentioned helium on Earth
and some oxygen and nitrogen, -
6:58 - 7:02and from MAVEN we can also look
at the oxygen being lost from Mars. -
7:02 - 7:05And you can see
that because oxygen is heavier, -
7:05 - 7:08it can't get as far as the hydrogen,
-
7:08 - 7:10but it's still escaping
away from the planet. -
7:10 - 7:13You don't see it all confined
into that red circle. -
7:14 - 7:18So the fact that we not only see
atmospheric escape on our own planet -
7:18 - 7:21but we can study it elsewhere
and send spacecraft -
7:21 - 7:25allows us to learn
about the past of planets -
7:25 - 7:27but also about planets in general
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7:27 - 7:29and Earth's future.
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7:29 - 7:31So one way we actually
can learn about the future -
7:31 - 7:34is by planets so far away
that we can't see. -
7:35 - 7:38And I should just note though,
before I go on to that, -
7:39 - 7:41I'm not going to show you
photos like this of Pluto, -
7:41 - 7:42which might be disappointing,
-
7:42 - 7:44but that's because we don't have them yet.
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7:44 - 7:48But the New Horizons mission
is currently studying atmospheric escape -
7:48 - 7:49being lost from the planet.
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7:49 - 7:51So stay tuned and look out for that.
-
7:52 - 7:54But the planets
that I did want to talk about -
7:54 - 7:56are known as transiting exoplanets.
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7:56 - 8:00So any planet orbiting a star
that's not our Sun -
8:00 - 8:03is called an exoplanet,
or extrasolar planet. -
8:03 - 8:05And these planets that we call transiting
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8:05 - 8:07have the special feature
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8:07 - 8:09that if you look
at that star in the middle, -
8:09 - 8:11you'll see that actually it's blinking.
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8:11 - 8:13And the reason that it's blinking
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8:13 - 8:17is because there are planets
that are going past it all the time, -
8:17 - 8:19and it's at special orientation
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8:19 - 8:22where the planets are blocking
the light from the star -
8:22 - 8:24that allows us to see that light blinking.
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8:24 - 8:27I'll show that one more time,
you can see that blinking light. -
8:28 - 8:31And by surveying the stars
in the night sky -
8:31 - 8:32for this blinking motion,
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8:32 - 8:34we are able to find planets.
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8:34 - 8:38This is how we've now been able
to detect over 5,000 planets -
8:38 - 8:40in our own Milky Way,
-
8:40 - 8:42and we know there are
many more out there, like I mentioned. -
8:42 - 8:45When we look at the light
from these stars, -
8:45 - 8:48what we see, like I said,
is not the planet itself, -
8:48 - 8:50but you actually see
a dimming of the light -
8:50 - 8:52that we can record in time.
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8:52 - 8:55So the light drops as the planet
decreases in front of the star, -
8:55 - 8:57and that's that blinking
that you saw before. -
8:57 - 8:59So not only do we detect the planets
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8:59 - 9:02but we can look at this light
in different wavelengths. -
9:02 - 9:06So I mentioned looking at the Earth
and Mars in ultraviolet light. -
9:06 - 9:10If we look at transiting exoplanets
with the Hubble Space Telescope, -
9:10 - 9:12we find that in the ultraviolet,
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9:12 - 9:16you see much bigger blinking,
much less light from the star, -
9:16 - 9:17when the planet is passing in front.
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9:18 - 9:21And we think this is because you have
an extended atmosphere of hydrogen -
9:21 - 9:22all around the planet
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9:22 - 9:24that's making it look puffier
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9:24 - 9:26and thus blocking
more of the light that you see. -
9:27 - 9:30So using this technique,
we've actually been able to discover -
9:30 - 9:34a few transiting exoplanets
that are undergoing atmospheric escape. -
9:34 - 9:37And these planets
can be called hot Jupiters, -
9:37 - 9:39for some of the ones we've found.
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9:39 - 9:41And that's because
they're gas planets like Jupiter, -
9:41 - 9:43but they're so close to their star,
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9:43 - 9:45about a hundred times closer than Jupiter.
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9:45 - 9:49And because there's all this
lightweight gas that's ready to escape, -
9:49 - 9:51and all this heating from the star,
-
9:51 - 9:54you have completely catastrophic rates
of atmospheric escape. -
9:54 - 9:59So unlike our 400 pounds per minute
of hydrogen being lost on Earth, -
9:59 - 10:00for these planets,
-
10:00 - 10:04you're losing 1.3 billion
pounds of hydrogen every minute. -
10:05 - 10:10So you might think, well,
does this make the planet cease to exist? -
10:10 - 10:12And this is a question
that people wondered -
10:12 - 10:14when they looked at our solar system,
-
10:14 - 10:16because planets
closer to the Sun are rocky, -
10:16 - 10:19and planets further away
are bigger and more gaseous. -
10:19 - 10:21Could you have started
with something like Jupiter -
10:21 - 10:23that was actually close to the Sun,
-
10:23 - 10:25and get rid of all the gas in it?
-
10:25 - 10:28We now think that if you start
with something like a hot Jupiter, -
10:28 - 10:31you actually can't end up
with Mercury or the Earth. -
10:31 - 10:33But if you started with something smaller,
-
10:33 - 10:36it's possible that enough gas
would have gotten away -
10:36 - 10:38that it would have
significantly impacted it -
10:38 - 10:42and left you with something very different
than what you started with. -
10:42 - 10:43So all of this sounds sort of general,
-
10:44 - 10:46and we might think about the solar system,
-
10:46 - 10:49but what does this have to do
with us here on Earth? -
10:49 - 10:51Well, in the far future,
-
10:51 - 10:53the Sun is going to get brighter.
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10:53 - 10:54And as that happens,
-
10:54 - 10:57the heating that we find from the Sun
is going to become very intense. -
10:58 - 11:02In the same way that you see
gas streaming off from a hot Jupiter, -
11:02 - 11:05gas is going to stream off from the Earth.
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11:05 - 11:07And so what we can look forward to,
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11:07 - 11:09or at least prepare for,
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11:09 - 11:11is the fact that in the far future,
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11:11 - 11:14the Earth is going to look more like Mars.
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11:14 - 11:16Our hydrogen, from water
that is broken down, -
11:16 - 11:19is going to escape
into space more rapidly, -
11:19 - 11:23and we're going to be left
with this dry, reddish planet. -
11:23 - 11:26So don't fear, it's not
for a few billion years, -
11:26 - 11:28so there's some time to prepare.
-
11:28 - 11:29(Laughter)
-
11:29 - 11:31But I wanted you
to be aware of what's going on, -
11:32 - 11:33not just in the future,
-
11:33 - 11:36but atmospheric escape
is happening as we speak. -
11:36 - 11:40So there's a lot of amazing science
that you hear about happening in space -
11:40 - 11:41and planets that are far away,
-
11:42 - 11:45and we are studying these planets
to learn about these worlds. -
11:45 - 11:49But as we learn about Mars
or exoplanets like hot Jupiters, -
11:49 - 11:52we find things like atmospheric escape
-
11:52 - 11:56that tell us a lot more
about our planet here on Earth. -
11:56 - 12:00So consider that the next time
you think that space is far away. -
12:00 - 12:02Thank you.
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12:02 - 12:05(Applause)
- Title:
- Why Earth may someday look like Mars | Anjali Tripathi | TEDxBeaconStreet
- Description:
-
Every minute, 400 pounds of hydrogen and almost 7 pounds of helium escape from Earth's atmosphere into outer space. Astrophysicist Anjali Tripathi studies the phenomenon of atmospheric escape, and in this fascinating and accessible talk, she considers how this process might one day (a few billion years from now) turn our blue planet red.
This talk was given at a TEDx event using the TED conference format but independently organized by a local community. Learn more at http://ted.com/tedx
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDxTalks
- Duration:
- 12:13
TED Translators admin edited English subtitles for Your Atmosphere is Escaping | Anjali Tripathi | TEDxBeaconStreet | ||
TED Translators admin edited English subtitles for Your Atmosphere is Escaping | Anjali Tripathi | TEDxBeaconStreet |