[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:11.72,0:00:14.32,Default,,0000,0000,0000,,Okay, this is going to be\Nso much fun!
Dialogue: 0,0:00:14.36,0:00:15.36,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:00:15.44,0:00:16.86,Default,,0000,0000,0000,,I'm really glad to be here.
Dialogue: 0,0:00:17.52,0:00:19.20,Default,,0000,0000,0000,,I'm glad you're here,
Dialogue: 0,0:00:19.23,0:00:21.06,Default,,0000,0000,0000,,because that would be a little weird.
Dialogue: 0,0:00:21.96,0:00:24.06,Default,,0000,0000,0000,,I'm glad we're all here.
Dialogue: 0,0:00:24.80,0:00:27.66,Default,,0000,0000,0000,,And by "here," I don't mean here.
Dialogue: 0,0:00:29.62,0:00:30.77,Default,,0000,0000,0000,,Or here.
Dialogue: 0,0:00:32.53,0:00:33.68,Default,,0000,0000,0000,,But here.
Dialogue: 0,0:00:33.70,0:00:34.85,Default,,0000,0000,0000,,I mean Earth.
Dialogue: 0,0:00:35.83,0:00:39.77,Default,,0000,0000,0000,,And by "we," I don't mean\Nthose of us in this auditorium,
Dialogue: 0,0:00:41.29,0:00:42.76,Default,,0000,0000,0000,,but life,
Dialogue: 0,0:00:42.79,0:00:44.24,Default,,0000,0000,0000,,all life on Earth --
Dialogue: 0,0:00:44.26,0:00:49.04,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:00:49.08,0:00:51.07,Default,,0000,0000,0000,,from complex to single-celled,
Dialogue: 0,0:00:51.10,0:00:53.42,Default,,0000,0000,0000,,from mold to mushrooms
Dialogue: 0,0:00:53.44,0:00:54.82,Default,,0000,0000,0000,,to flying bears.
Dialogue: 0,0:00:54.84,0:00:56.21,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:00:58.54,0:01:00.04,Default,,0000,0000,0000,,The interesting thing is,
Dialogue: 0,0:01:00.07,0:01:03.10,Default,,0000,0000,0000,,Earth is the only place\Nwe know of that has life --
Dialogue: 0,0:01:03.12,0:01:05.00,Default,,0000,0000,0000,,8.7 million species.
Dialogue: 0,0:01:05.46,0:01:06.71,Default,,0000,0000,0000,,We've looked other places,
Dialogue: 0,0:01:06.74,0:01:08.84,Default,,0000,0000,0000,,maybe not as hard\Nas we should or we could,
Dialogue: 0,0:01:08.86,0:01:10.79,Default,,0000,0000,0000,,but we've looked and haven't found any;
Dialogue: 0,0:01:10.81,0:01:13.09,Default,,0000,0000,0000,,Earth is the only place\Nwe know of with life.
Dialogue: 0,0:01:14.12,0:01:15.39,Default,,0000,0000,0000,,Is Earth special?
Dialogue: 0,0:01:16.39,0:01:18.84,Default,,0000,0000,0000,,This is a question I've wanted\Nto know the answer to
Dialogue: 0,0:01:18.87,0:01:20.12,Default,,0000,0000,0000,,since I was a small child,
Dialogue: 0,0:01:20.15,0:01:22.18,Default,,0000,0000,0000,,and I suspect 80 percent\Nof this auditorium
Dialogue: 0,0:01:22.20,0:01:25.21,Default,,0000,0000,0000,,has thought the same thing\Nand also wanted to know the answer.
Dialogue: 0,0:01:25.68,0:01:27.85,Default,,0000,0000,0000,,To understand whether\Nthere are any planets --
Dialogue: 0,0:01:27.87,0:01:30.15,Default,,0000,0000,0000,,out there in our solar system or beyond --
Dialogue: 0,0:01:30.17,0:01:31.63,Default,,0000,0000,0000,,that can support life,
Dialogue: 0,0:01:31.65,0:01:34.85,Default,,0000,0000,0000,,the first step is to understand\Nwhat life here requires.
Dialogue: 0,0:01:35.38,0:01:38.94,Default,,0000,0000,0000,,It turns out, of all of those\N8.7 million species,
Dialogue: 0,0:01:38.96,0:01:41.16,Default,,0000,0000,0000,,life only needs three things.
Dialogue: 0,0:01:42.53,0:01:45.38,Default,,0000,0000,0000,,On one side, all life\Non Earth needs energy.
Dialogue: 0,0:01:45.41,0:01:48.89,Default,,0000,0000,0000,,Complex life like us derives\Nour energy from the sun,
Dialogue: 0,0:01:49.82,0:01:51.92,Default,,0000,0000,0000,,but life deep underground\Ncan get its energy
Dialogue: 0,0:01:51.94,0:01:53.66,Default,,0000,0000,0000,,from things like chemical reactions.
Dialogue: 0,0:01:53.69,0:01:55.84,Default,,0000,0000,0000,,There are a number\Nof different energy sources
Dialogue: 0,0:01:55.86,0:01:57.11,Default,,0000,0000,0000,,available on all planets.
Dialogue: 0,0:01:57.80,0:01:58.96,Default,,0000,0000,0000,,On the other side,
Dialogue: 0,0:01:58.98,0:02:01.68,Default,,0000,0000,0000,,all life needs food or nourishment.
Dialogue: 0,0:02:02.14,0:02:06.62,Default,,0000,0000,0000,,And this seems like a tall order,\Nespecially if you want a succulent tomato.
Dialogue: 0,0:02:06.64,0:02:08.35,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:02:08.38,0:02:11.44,Default,,0000,0000,0000,,However, all life on Earth\Nderives its nourishment
Dialogue: 0,0:02:11.47,0:02:13.50,Default,,0000,0000,0000,,from only six chemical elements,
Dialogue: 0,0:02:13.52,0:02:16.53,Default,,0000,0000,0000,,and these elements can be found\Non any planetary body
Dialogue: 0,0:02:16.55,0:02:17.89,Default,,0000,0000,0000,,in our solar system.
Dialogue: 0,0:02:18.94,0:02:22.16,Default,,0000,0000,0000,,So that leaves the thing\Nin the middle as the tall pole,
Dialogue: 0,0:02:22.19,0:02:24.14,Default,,0000,0000,0000,,the thing that's hardest to achieve.
Dialogue: 0,0:02:24.17,0:02:26.06,Default,,0000,0000,0000,,Not moose, but water.
Dialogue: 0,0:02:26.08,0:02:28.86,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:02:29.68,0:02:31.48,Default,,0000,0000,0000,,Although moose would be pretty cool.
Dialogue: 0,0:02:31.50,0:02:32.66,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:02:32.68,0:02:38.23,Default,,0000,0000,0000,,And not frozen water, and not water\Nin a gaseous state, but liquid water.
Dialogue: 0,0:02:38.45,0:02:40.90,Default,,0000,0000,0000,,This is what life needs\Nto survive, all life.
Dialogue: 0,0:02:41.38,0:02:44.72,Default,,0000,0000,0000,,And many solar system bodies\Ndon't have liquid water,
Dialogue: 0,0:02:44.74,0:02:46.38,Default,,0000,0000,0000,,and so we don't look there.
Dialogue: 0,0:02:46.40,0:02:49.39,Default,,0000,0000,0000,,Other solar system bodies\Nmight have abundant liquid water,
Dialogue: 0,0:02:49.42,0:02:50.75,Default,,0000,0000,0000,,even more than Earth,
Dialogue: 0,0:02:50.78,0:02:53.23,Default,,0000,0000,0000,,but it's trapped beneath an icy shell,
Dialogue: 0,0:02:53.25,0:02:55.51,Default,,0000,0000,0000,,and so it's hard to access,\Nit's hard to get to,
Dialogue: 0,0:02:55.54,0:02:58.25,Default,,0000,0000,0000,,it's hard to even find out\Nif there's any life there.
Dialogue: 0,0:03:00.68,0:03:02.72,Default,,0000,0000,0000,,So that leaves
Dialogue: 0,0:03:04.08,0:03:06.03,Default,,0000,0000,0000,,a few bodies that we should think about.
Dialogue: 0,0:03:06.09,0:03:08.52,Default,,0000,0000,0000,,So let's make the problem\Nsimpler for ourselves.
Dialogue: 0,0:03:08.55,0:03:11.89,Default,,0000,0000,0000,,Let's think only about liquid water\Non the surface of a planet.
Dialogue: 0,0:03:11.91,0:03:14.87,Default,,0000,0000,0000,,There are only three bodies\Nto think about in our solar system,
Dialogue: 0,0:03:14.89,0:03:17.47,Default,,0000,0000,0000,,with regard to liquid water\Non the surface of a planet,
Dialogue: 0,0:03:17.50,0:03:22.32,Default,,0000,0000,0000,,and in order of distance from the sun,\Nit's: Venus, Earth and Mars.
Dialogue: 0,0:03:22.86,0:03:26.24,Default,,0000,0000,0000,,You want to have an atmosphere\Nfor water to be liquid.
Dialogue: 0,0:03:26.26,0:03:28.64,Default,,0000,0000,0000,,You have to be very careful\Nwith that atmosphere.
Dialogue: 0,0:03:28.66,0:03:32.08,Default,,0000,0000,0000,,You can't have too much atmosphere,\Ntoo thick or too warm an atmosphere,
Dialogue: 0,0:03:32.10,0:03:35.00,Default,,0000,0000,0000,,because then you end up\Ntoo hot like Venus,
Dialogue: 0,0:03:35.03,0:03:36.76,Default,,0000,0000,0000,,and you can't have liquid water.
Dialogue: 0,0:03:36.79,0:03:40.74,Default,,0000,0000,0000,,But if you have too little atmosphere\Nand it's too thin and too cold,
Dialogue: 0,0:03:40.77,0:03:42.79,Default,,0000,0000,0000,,you end up like Mars, too cold.
Dialogue: 0,0:03:43.46,0:03:45.94,Default,,0000,0000,0000,,So Venus is too hot, Mars is too cold,
Dialogue: 0,0:03:45.96,0:03:47.13,Default,,0000,0000,0000,,and Earth is just right.
Dialogue: 0,0:03:47.15,0:03:50.63,Default,,0000,0000,0000,,You can look at these images behind me\Nand you can see automatically
Dialogue: 0,0:03:50.65,0:03:53.25,Default,,0000,0000,0000,,where life can survive\Nin our solar system.
Dialogue: 0,0:03:53.90,0:03:55.50,Default,,0000,0000,0000,,It's a Goldilocks-type problem,
Dialogue: 0,0:03:55.52,0:03:58.01,Default,,0000,0000,0000,,and it's so simple\Nthat a child could understand it.
Dialogue: 0,0:04:00.05,0:04:01.23,Default,,0000,0000,0000,,However,
Dialogue: 0,0:04:02.05,0:04:04.98,Default,,0000,0000,0000,,I'd like to remind you of two things
Dialogue: 0,0:04:05.00,0:04:07.96,Default,,0000,0000,0000,,from the Goldilocks story\Nthat we may not think about so often
Dialogue: 0,0:04:07.98,0:04:10.08,Default,,0000,0000,0000,,but that I think are really relevant here.
Dialogue: 0,0:04:10.66,0:04:11.81,Default,,0000,0000,0000,,Number one:
Dialogue: 0,0:04:12.91,0:04:15.70,Default,,0000,0000,0000,,if Mama Bear's bowl is too cold
Dialogue: 0,0:04:16.43,0:04:18.44,Default,,0000,0000,0000,,when Goldilocks walks into the room,
Dialogue: 0,0:04:19.24,0:04:21.38,Default,,0000,0000,0000,,does that mean it's always been too cold?
Dialogue: 0,0:04:22.42,0:04:25.69,Default,,0000,0000,0000,,Or could it have been just right\Nat some other time?
Dialogue: 0,0:04:26.25,0:04:29.93,Default,,0000,0000,0000,,When Goldilocks walks into the room\Ndetermines the answer
Dialogue: 0,0:04:29.96,0:04:31.29,Default,,0000,0000,0000,,that we get in the story.
Dialogue: 0,0:04:31.71,0:04:33.44,Default,,0000,0000,0000,,And the same is true with planets.
Dialogue: 0,0:04:33.47,0:04:35.49,Default,,0000,0000,0000,,They're not static things. They change.
Dialogue: 0,0:04:35.52,0:04:37.26,Default,,0000,0000,0000,,They vary. They evolve.
Dialogue: 0,0:04:37.28,0:04:39.33,Default,,0000,0000,0000,,And atmospheres do the same.
Dialogue: 0,0:04:40.55,0:04:42.25,Default,,0000,0000,0000,,So let me give you an example.
Dialogue: 0,0:04:43.18,0:04:45.18,Default,,0000,0000,0000,,Here's one of my favorite\Npictures of Mars.
Dialogue: 0,0:04:45.20,0:04:48.33,Default,,0000,0000,0000,,It's not the highest resolution image,\Nit's not the sexiest image,
Dialogue: 0,0:04:48.36,0:04:49.86,Default,,0000,0000,0000,,it's not the most recent image,
Dialogue: 0,0:04:49.88,0:04:53.38,Default,,0000,0000,0000,,but it's an image that shows riverbeds\Ncut into the surface of the planet;
Dialogue: 0,0:04:54.52,0:04:57.10,Default,,0000,0000,0000,,riverbeds carved by flowing, liquid water;
Dialogue: 0,0:04:59.12,0:05:04.00,Default,,0000,0000,0000,,riverbeds that take hundreds or thousands\Nor tens of thousands of years to form.
Dialogue: 0,0:05:04.02,0:05:05.64,Default,,0000,0000,0000,,This can't happen on Mars today.
Dialogue: 0,0:05:05.67,0:05:08.15,Default,,0000,0000,0000,,The atmosphere of Mars today\Nis too thin and too cold
Dialogue: 0,0:05:08.17,0:05:10.31,Default,,0000,0000,0000,,for water to be stable as a liquid.
Dialogue: 0,0:05:10.34,0:05:14.68,Default,,0000,0000,0000,,This one image tells you\Nthat the atmosphere of Mars changed,
Dialogue: 0,0:05:14.71,0:05:16.74,Default,,0000,0000,0000,,and it changed in big ways.
Dialogue: 0,0:05:17.31,0:05:22.12,Default,,0000,0000,0000,,And it changed from a state\Nthat we would define as habitable,
Dialogue: 0,0:05:22.15,0:05:25.74,Default,,0000,0000,0000,,because the three requirements\Nfor life were present long ago.
Dialogue: 0,0:05:27.15,0:05:29.22,Default,,0000,0000,0000,,Where did that atmosphere go
Dialogue: 0,0:05:29.24,0:05:32.06,Default,,0000,0000,0000,,that allowed water\Nto be liquid at the surface?
Dialogue: 0,0:05:32.08,0:05:35.43,Default,,0000,0000,0000,,Well, one idea is it escaped\Naway to space.
Dialogue: 0,0:05:35.46,0:05:38.12,Default,,0000,0000,0000,,Atmospheric particles\Ngot enough energy to break free
Dialogue: 0,0:05:38.15,0:05:39.80,Default,,0000,0000,0000,,from the gravity of the planet,
Dialogue: 0,0:05:39.82,0:05:42.51,Default,,0000,0000,0000,,escaping away to space, never to return.
Dialogue: 0,0:05:43.04,0:05:45.72,Default,,0000,0000,0000,,And this happens with all bodies\Nwith atmospheres.
Dialogue: 0,0:05:45.75,0:05:46.92,Default,,0000,0000,0000,,Comets have tails
Dialogue: 0,0:05:46.94,0:05:50.20,Default,,0000,0000,0000,,that are incredibly visible reminders\Nof atmospheric escape.
Dialogue: 0,0:05:50.23,0:05:53.64,Default,,0000,0000,0000,,But Venus also has an atmosphere\Nthat escapes with time,
Dialogue: 0,0:05:53.66,0:05:55.32,Default,,0000,0000,0000,,and Mars and Earth as well.
Dialogue: 0,0:05:55.34,0:05:58.31,Default,,0000,0000,0000,,It's just a matter of degree\Nand a matter of scale.
Dialogue: 0,0:05:58.69,0:06:01.37,Default,,0000,0000,0000,,So we'd like to figure out\Nhow much escaped over time
Dialogue: 0,0:06:01.39,0:06:03.51,Default,,0000,0000,0000,,so we can explain this transition.
Dialogue: 0,0:06:05.03,0:06:07.64,Default,,0000,0000,0000,,How do atmospheres\Nget their energy for escape?
Dialogue: 0,0:06:07.67,0:06:09.80,Default,,0000,0000,0000,,How do particles get\Nenough energy to escape?
Dialogue: 0,0:06:09.82,0:06:13.01,Default,,0000,0000,0000,,There are two ways, if we're going\Nto reduce things a little bit.
Dialogue: 0,0:06:13.03,0:06:14.18,Default,,0000,0000,0000,,Number one, sunlight.
Dialogue: 0,0:06:14.21,0:06:17.62,Default,,0000,0000,0000,,Light emitted from the sun can be absorbed\Nby atmospheric particles
Dialogue: 0,0:06:17.64,0:06:19.36,Default,,0000,0000,0000,,and warm the particles.
Dialogue: 0,0:06:19.38,0:06:21.49,Default,,0000,0000,0000,,Yes, I'm dancing, but they --
Dialogue: 0,0:06:21.51,0:06:22.98,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:06:23.79,0:06:25.70,Default,,0000,0000,0000,,Oh my God, not even at my wedding.
Dialogue: 0,0:06:25.73,0:06:27.22,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:06:27.24,0:06:30.25,Default,,0000,0000,0000,,They get enough energy\Nto escape and break free
Dialogue: 0,0:06:30.27,0:06:32.77,Default,,0000,0000,0000,,from the gravity of the planet\Njust by warming.
Dialogue: 0,0:06:32.80,0:06:35.96,Default,,0000,0000,0000,,A second way they can get energy\Nis from the solar wind.
Dialogue: 0,0:06:36.48,0:06:41.51,Default,,0000,0000,0000,,These are particles, mass, material,\Nspit out from the surface of the sun,
Dialogue: 0,0:06:41.53,0:06:43.94,Default,,0000,0000,0000,,and they go screaming\Nthrough the solar system
Dialogue: 0,0:06:43.96,0:06:45.74,Default,,0000,0000,0000,,at 400 kilometers per second,
Dialogue: 0,0:06:45.77,0:06:48.36,Default,,0000,0000,0000,,sometimes faster during solar storms,
Dialogue: 0,0:06:48.39,0:06:51.11,Default,,0000,0000,0000,,and they go hurtling\Nthrough interplanetary space
Dialogue: 0,0:06:51.13,0:06:53.58,Default,,0000,0000,0000,,towards planets and their atmospheres,
Dialogue: 0,0:06:53.60,0:06:55.23,Default,,0000,0000,0000,,and they may provide energy
Dialogue: 0,0:06:55.25,0:06:57.38,Default,,0000,0000,0000,,for atmospheric particles\Nto escape as well.
Dialogue: 0,0:06:57.78,0:06:59.75,Default,,0000,0000,0000,,This is something that I'm interested in,
Dialogue: 0,0:06:59.78,0:07:01.49,Default,,0000,0000,0000,,because it relates to habitability.
Dialogue: 0,0:07:03.28,0:07:06.41,Default,,0000,0000,0000,,I mentioned that there were two things\Nabout the Goldilocks story
Dialogue: 0,0:07:06.43,0:07:09.42,Default,,0000,0000,0000,,that I wanted to bring to your attention\Nand remind you about,
Dialogue: 0,0:07:09.44,0:07:11.68,Default,,0000,0000,0000,,and the second one\Nis a little bit more subtle.
Dialogue: 0,0:07:12.40,0:07:15.19,Default,,0000,0000,0000,,If Papa Bear's bowl is too hot,
Dialogue: 0,0:07:16.78,0:07:20.01,Default,,0000,0000,0000,,and Mama Bear's bowl is too cold,
Dialogue: 0,0:07:21.66,0:07:24.77,Default,,0000,0000,0000,,shouldn't Baby Bear's bowl be even colder
Dialogue: 0,0:07:25.68,0:07:27.48,Default,,0000,0000,0000,,if we're following the trend?
Dialogue: 0,0:07:28.80,0:07:31.11,Default,,0000,0000,0000,,This thing that you've accepted\Nyour entire life,
Dialogue: 0,0:07:31.13,0:07:34.20,Default,,0000,0000,0000,,when you think about it a little bit more,\Nmay not be so simple.
Dialogue: 0,0:07:35.11,0:07:39.14,Default,,0000,0000,0000,,And of course, distance of a planet\Nfrom the sun determines its temperature.
Dialogue: 0,0:07:39.16,0:07:41.43,Default,,0000,0000,0000,,This has to play into habitability.
Dialogue: 0,0:07:41.46,0:07:44.38,Default,,0000,0000,0000,,But maybe there are other things\Nwe should be thinking about.
Dialogue: 0,0:07:44.41,0:07:46.02,Default,,0000,0000,0000,,Maybe it's the bowls themselves
Dialogue: 0,0:07:46.05,0:07:49.10,Default,,0000,0000,0000,,that are also helping to determine\Nthe outcome in the story,
Dialogue: 0,0:07:49.13,0:07:50.43,Default,,0000,0000,0000,,what is just right.
Dialogue: 0,0:07:51.36,0:07:54.23,Default,,0000,0000,0000,,I could talk to you about a lot\Nof different characteristics
Dialogue: 0,0:07:54.25,0:07:55.40,Default,,0000,0000,0000,,of these three planets
Dialogue: 0,0:07:55.43,0:07:56.100,Default,,0000,0000,0000,,that may influence habitability,
Dialogue: 0,0:07:57.08,0:07:59.39,Default,,0000,0000,0000,,but I would like to talk\Nfor just a minute or two
Dialogue: 0,0:07:59.42,0:08:00.71,Default,,0000,0000,0000,,about magnetic fields.
Dialogue: 0,0:08:01.32,0:08:03.85,Default,,0000,0000,0000,,Earth has one; Venus and Mars do not.
Dialogue: 0,0:08:04.42,0:08:07.55,Default,,0000,0000,0000,,Magnetic fields are generated\Nin the deep interior of a planet
Dialogue: 0,0:08:07.57,0:08:11.29,Default,,0000,0000,0000,,by electrically conducting\Nchurning fluid material
Dialogue: 0,0:08:11.31,0:08:14.22,Default,,0000,0000,0000,,that creates this big old magnetic field\Nthat surrounds Earth.
Dialogue: 0,0:08:14.24,0:08:16.64,Default,,0000,0000,0000,,If you have a compass,\Nyou know which way north is.
Dialogue: 0,0:08:16.66,0:08:18.16,Default,,0000,0000,0000,,Venus and Mars don't have that.
Dialogue: 0,0:08:18.18,0:08:20.09,Default,,0000,0000,0000,,If you have a compass on Venus and Mars,
Dialogue: 0,0:08:20.12,0:08:21.51,Default,,0000,0000,0000,,congratulations, you're lost.
Dialogue: 0,0:08:21.54,0:08:23.44,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:08:23.46,0:08:25.50,Default,,0000,0000,0000,,Does this influence habitability?
Dialogue: 0,0:08:26.78,0:08:28.08,Default,,0000,0000,0000,,Well, how might it?
Dialogue: 0,0:08:29.72,0:08:32.33,Default,,0000,0000,0000,,Many scientists think\Nthat a magnetic field of a planet
Dialogue: 0,0:08:32.35,0:08:34.75,Default,,0000,0000,0000,,serves as a shield for the atmosphere,
Dialogue: 0,0:08:34.77,0:08:38.13,Default,,0000,0000,0000,,deflecting solar wind particles\Naround the planet
Dialogue: 0,0:08:38.15,0:08:39.96,Default,,0000,0000,0000,,in a bit of a force field-type effect
Dialogue: 0,0:08:39.99,0:08:42.69,Default,,0000,0000,0000,,having to do with electric charge\Nof those particles.
Dialogue: 0,0:08:43.06,0:08:46.69,Default,,0000,0000,0000,,I like to think of it instead\Nas a salad bar sneeze guard for planets.
Dialogue: 0,0:08:46.71,0:08:48.99,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:08:49.66,0:08:53.04,Default,,0000,0000,0000,,And yes, my colleagues\Nwho watch this later will realize
Dialogue: 0,0:08:53.07,0:08:55.61,Default,,0000,0000,0000,,this is the first time in the history\Nof our community
Dialogue: 0,0:08:55.64,0:08:57.91,Default,,0000,0000,0000,,that the solar wind has been\Nequated with mucus.
Dialogue: 0,0:08:57.94,0:08:59.59,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:09:02.38,0:09:05.85,Default,,0000,0000,0000,,OK, so the effect, then, is that Earth\Nmay have been protected
Dialogue: 0,0:09:05.88,0:09:07.04,Default,,0000,0000,0000,,for billions of years,
Dialogue: 0,0:09:07.07,0:09:08.92,Default,,0000,0000,0000,,because we've had a magnetic field.
Dialogue: 0,0:09:08.94,0:09:11.12,Default,,0000,0000,0000,,Atmosphere hasn't been able to escape.
Dialogue: 0,0:09:11.15,0:09:13.25,Default,,0000,0000,0000,,Mars, on the other hand,\Nhas been unprotected
Dialogue: 0,0:09:13.28,0:09:15.12,Default,,0000,0000,0000,,because of its lack of magnetic field,
Dialogue: 0,0:09:15.14,0:09:17.10,Default,,0000,0000,0000,,and over billions of years,
Dialogue: 0,0:09:17.12,0:09:19.30,Default,,0000,0000,0000,,maybe enough atmosphere\Nhas been stripped away
Dialogue: 0,0:09:19.32,0:09:21.92,Default,,0000,0000,0000,,to account for a transition\Nfrom a habitable planet
Dialogue: 0,0:09:21.94,0:09:23.61,Default,,0000,0000,0000,,to the planet that we see today.
Dialogue: 0,0:09:24.46,0:09:27.45,Default,,0000,0000,0000,,Other scientists think\Nthat magnetic fields
Dialogue: 0,0:09:27.47,0:09:29.64,Default,,0000,0000,0000,,may act more like the sails on a ship,
Dialogue: 0,0:09:30.66,0:09:35.70,Default,,0000,0000,0000,,enabling the planet to interact\Nwith more energy from the solar wind
Dialogue: 0,0:09:35.72,0:09:38.99,Default,,0000,0000,0000,,than the planet would have been able\Nto interact with by itself.
Dialogue: 0,0:09:39.02,0:09:41.51,Default,,0000,0000,0000,,The sails may gather energy\Nfrom the solar wind.
Dialogue: 0,0:09:41.53,0:09:44.20,Default,,0000,0000,0000,,The magnetic field may gather\Nenergy from the solar wind
Dialogue: 0,0:09:44.22,0:09:47.46,Default,,0000,0000,0000,,that allows even more\Natmospheric escape to happen.
Dialogue: 0,0:09:47.49,0:09:49.74,Default,,0000,0000,0000,,It's an idea that has to be tested,
Dialogue: 0,0:09:49.77,0:09:51.65,Default,,0000,0000,0000,,but the effect and how it works
Dialogue: 0,0:09:51.68,0:09:52.83,Default,,0000,0000,0000,,seems apparent.
Dialogue: 0,0:09:52.85,0:09:54.00,Default,,0000,0000,0000,,That's because we know
Dialogue: 0,0:09:54.02,0:09:57.10,Default,,0000,0000,0000,,energy from the solar wind\Nis being deposited into our atmosphere
Dialogue: 0,0:09:57.12,0:09:58.28,Default,,0000,0000,0000,,here on Earth.
Dialogue: 0,0:09:58.30,0:10:00.70,Default,,0000,0000,0000,,That energy is conducted\Nalong magnetic field lines
Dialogue: 0,0:10:00.73,0:10:02.08,Default,,0000,0000,0000,,down into the polar regions,
Dialogue: 0,0:10:02.10,0:10:04.24,Default,,0000,0000,0000,,resulting in incredibly beautiful aurora.
Dialogue: 0,0:10:04.26,0:10:06.92,Default,,0000,0000,0000,,If you've ever experienced them,\Nit's magnificent.
Dialogue: 0,0:10:06.94,0:10:08.95,Default,,0000,0000,0000,,We know the energy is getting in.
Dialogue: 0,0:10:08.97,0:10:12.00,Default,,0000,0000,0000,,We're trying to measure\Nhow many particles are getting out
Dialogue: 0,0:10:12.03,0:10:15.06,Default,,0000,0000,0000,,and if the magnetic field\Nis influencing this in any way.
Dialogue: 0,0:10:16.42,0:10:18.80,Default,,0000,0000,0000,,So I've posed a problem for you here,
Dialogue: 0,0:10:18.83,0:10:20.37,Default,,0000,0000,0000,,but I don't have a solution yet.
Dialogue: 0,0:10:20.40,0:10:21.67,Default,,0000,0000,0000,,We don't have a solution.
Dialogue: 0,0:10:22.40,0:10:24.76,Default,,0000,0000,0000,,But we're working on it.\NHow are we working on it?
Dialogue: 0,0:10:24.78,0:10:27.08,Default,,0000,0000,0000,,Well, we've sent spacecraft\Nto all three planets.
Dialogue: 0,0:10:27.10,0:10:28.58,Default,,0000,0000,0000,,Some of them are orbiting now,
Dialogue: 0,0:10:28.60,0:10:31.68,Default,,0000,0000,0000,,including the MAVEN spacecraft\Nwhich is currently orbiting Mars,
Dialogue: 0,0:10:31.70,0:10:35.23,Default,,0000,0000,0000,,which I'm involved with\Nand which is led here,
Dialogue: 0,0:10:35.26,0:10:37.07,Default,,0000,0000,0000,,out of the University of Colorado.
Dialogue: 0,0:10:37.09,0:10:39.37,Default,,0000,0000,0000,,It's designed to measure\Natmospheric escape.
Dialogue: 0,0:10:39.72,0:10:42.20,Default,,0000,0000,0000,,We have similar measurements\Nfrom Venus and Earth.
Dialogue: 0,0:10:42.65,0:10:44.32,Default,,0000,0000,0000,,Once we have all our measurements,
Dialogue: 0,0:10:44.34,0:10:47.22,Default,,0000,0000,0000,,we can combine all these together,\Nand we can understand
Dialogue: 0,0:10:47.24,0:10:50.66,Default,,0000,0000,0000,,how all three planets interact\Nwith their space environment,
Dialogue: 0,0:10:50.68,0:10:51.84,Default,,0000,0000,0000,,with the surroundings.
Dialogue: 0,0:10:51.87,0:10:55.39,Default,,0000,0000,0000,,And we can decide whether magnetic fields\Nare important for habitability
Dialogue: 0,0:10:55.41,0:10:56.57,Default,,0000,0000,0000,,or not.
Dialogue: 0,0:10:57.60,0:10:59.86,Default,,0000,0000,0000,,Once we have that answer,\Nwhy should you care?
Dialogue: 0,0:10:59.88,0:11:01.18,Default,,0000,0000,0000,,I mean, I care deeply ...
Dialogue: 0,0:11:02.83,0:11:04.83,Default,,0000,0000,0000,,And financially as well, but deeply.
Dialogue: 0,0:11:04.86,0:11:06.70,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:11:07.46,0:11:09.38,Default,,0000,0000,0000,,First of all, an answer to this question
Dialogue: 0,0:11:09.40,0:11:11.51,Default,,0000,0000,0000,,will teach us more\Nabout these three planets,
Dialogue: 0,0:11:11.53,0:11:12.69,Default,,0000,0000,0000,,Venus, Earth and Mars,
Dialogue: 0,0:11:12.72,0:11:15.63,Default,,0000,0000,0000,,not only about how they interact\Nwith their environment today,
Dialogue: 0,0:11:15.65,0:11:17.58,Default,,0000,0000,0000,,but how they were billions of years ago,
Dialogue: 0,0:11:17.60,0:11:19.66,Default,,0000,0000,0000,,whether they were habitable\Nlong ago or not.
Dialogue: 0,0:11:19.69,0:11:21.33,Default,,0000,0000,0000,,It will teach us about atmospheres
Dialogue: 0,0:11:21.36,0:11:23.35,Default,,0000,0000,0000,,that surround us and that are close.
Dialogue: 0,0:11:23.83,0:11:26.01,Default,,0000,0000,0000,,But moreover, what we learn\Nfrom these planets
Dialogue: 0,0:11:26.04,0:11:28.06,Default,,0000,0000,0000,,can be applied to atmospheres everywhere,
Dialogue: 0,0:11:29.18,0:11:32.10,Default,,0000,0000,0000,,including planets that we're now\Nobserving around other stars.
Dialogue: 0,0:11:32.12,0:11:33.88,Default,,0000,0000,0000,,For example, the Kepler spacecraft,
Dialogue: 0,0:11:33.90,0:11:37.11,Default,,0000,0000,0000,,which is built and controlled\Nhere in Boulder,
Dialogue: 0,0:11:37.13,0:11:40.42,Default,,0000,0000,0000,,has been observing\Na postage stamp-sized region of the sky
Dialogue: 0,0:11:40.44,0:11:41.69,Default,,0000,0000,0000,,for a couple years now,
Dialogue: 0,0:11:41.71,0:11:43.94,Default,,0000,0000,0000,,and it's found thousands of planets --
Dialogue: 0,0:11:43.96,0:11:46.88,Default,,0000,0000,0000,,in one postage stamp-sized\Nregion of the sky
Dialogue: 0,0:11:46.90,0:11:50.99,Default,,0000,0000,0000,,that we don't think is any different\Nfrom any other part of the sky.
Dialogue: 0,0:11:51.52,0:11:53.32,Default,,0000,0000,0000,,We've gone, in 20 years,
Dialogue: 0,0:11:53.35,0:11:57.39,Default,,0000,0000,0000,,from knowing of zero planets\Noutside of our solar system,
Dialogue: 0,0:11:57.41,0:11:59.16,Default,,0000,0000,0000,,to now having so many,
Dialogue: 0,0:11:59.19,0:12:02.33,Default,,0000,0000,0000,,that we don't know\Nwhich ones to investigate first.
Dialogue: 0,0:12:03.97,0:12:05.43,Default,,0000,0000,0000,,Any lever will help.
Dialogue: 0,0:12:07.24,0:12:10.82,Default,,0000,0000,0000,,In fact, based on observations\Nthat Kepler's taken
Dialogue: 0,0:12:10.85,0:12:12.98,Default,,0000,0000,0000,,and other similar observations,
Dialogue: 0,0:12:13.00,0:12:14.17,Default,,0000,0000,0000,,we now believe that,
Dialogue: 0,0:12:14.19,0:12:18.89,Default,,0000,0000,0000,,of the 200 billion stars\Nin the Milky Way galaxy alone,
Dialogue: 0,0:12:19.49,0:12:24.09,Default,,0000,0000,0000,,on average, every star\Nhas at least one planet.
Dialogue: 0,0:12:25.52,0:12:27.02,Default,,0000,0000,0000,,In addition to that,
Dialogue: 0,0:12:27.05,0:12:32.75,Default,,0000,0000,0000,,estimates suggest there are somewhere\Nbetween 40 billion and 100 billion
Dialogue: 0,0:12:32.77,0:12:36.10,Default,,0000,0000,0000,,of those planets\Nthat we would define as habitable
Dialogue: 0,0:12:37.04,0:12:38.45,Default,,0000,0000,0000,,in just our galaxy.
Dialogue: 0,0:12:40.49,0:12:42.53,Default,,0000,0000,0000,,We have the observations of those planets,
Dialogue: 0,0:12:42.55,0:12:45.04,Default,,0000,0000,0000,,but we just don't know\Nwhich ones are habitable yet.
Dialogue: 0,0:12:45.06,0:12:48.66,Default,,0000,0000,0000,,It's a little bit like\Nbeing trapped on a red spot --
Dialogue: 0,0:12:48.69,0:12:49.86,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:12:49.88,0:12:51.12,Default,,0000,0000,0000,,on a stage
Dialogue: 0,0:12:52.08,0:12:55.64,Default,,0000,0000,0000,,and knowing that there are\Nother worlds out there
Dialogue: 0,0:12:56.94,0:12:59.72,Default,,0000,0000,0000,,and desperately wanting to know\Nmore about them,
Dialogue: 0,0:13:01.07,0:13:05.01,Default,,0000,0000,0000,,wanting to interrogate them and find out\Nif maybe just one or two of them
Dialogue: 0,0:13:05.03,0:13:06.64,Default,,0000,0000,0000,,are a little bit like you.
Dialogue: 0,0:13:08.14,0:13:10.70,Default,,0000,0000,0000,,You can't do that.\NYou can't go there, not yet.
Dialogue: 0,0:13:10.73,0:13:14.72,Default,,0000,0000,0000,,And so you have to use the tools\Nthat you've developed around you
Dialogue: 0,0:13:14.74,0:13:16.04,Default,,0000,0000,0000,,for Venus, Earth and Mars,
Dialogue: 0,0:13:16.06,0:13:18.88,Default,,0000,0000,0000,,and you have to apply them\Nto these other situations,
Dialogue: 0,0:13:18.90,0:13:23.60,Default,,0000,0000,0000,,and hope that you're making\Nreasonable inferences from the data,
Dialogue: 0,0:13:23.62,0:13:26.74,Default,,0000,0000,0000,,and that you're going to be able\Nto determine the best candidates
Dialogue: 0,0:13:26.76,0:13:29.16,Default,,0000,0000,0000,,for habitable planets,\Nand those that are not.
Dialogue: 0,0:13:30.64,0:13:33.35,Default,,0000,0000,0000,,In the end, and for now, at least,
Dialogue: 0,0:13:33.38,0:13:36.16,Default,,0000,0000,0000,,this is our red spot, right here.
Dialogue: 0,0:13:36.88,0:13:40.21,Default,,0000,0000,0000,,This is the only planet\Nthat we know of that's habitable,
Dialogue: 0,0:13:40.24,0:13:43.43,Default,,0000,0000,0000,,although very soon we may\Ncome to know of more.
Dialogue: 0,0:13:43.45,0:13:46.19,Default,,0000,0000,0000,,But for now, this is\Nthe only habitable planet,
Dialogue: 0,0:13:46.21,0:13:47.51,Default,,0000,0000,0000,,and this is our red spot.
Dialogue: 0,0:13:48.48,0:13:49.90,Default,,0000,0000,0000,,I'm really glad we're here.
Dialogue: 0,0:13:51.01,0:13:52.18,Default,,0000,0000,0000,,Thanks.
Dialogue: 0,0:13:52.21,0:13:55.44,Default,,0000,0000,0000,,(Applause)