[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.94,0:00:02.36,Default,,0000,0000,0000,,I'm really glad to be here.
Dialogue: 0,0:00:03.02,0:00:04.70,Default,,0000,0000,0000,,I'm glad you're here,
Dialogue: 0,0:00:04.73,0:00:06.56,Default,,0000,0000,0000,,because that would be a little weird.
Dialogue: 0,0:00:07.46,0:00:09.56,Default,,0000,0000,0000,,I'm glad we're all here.
Dialogue: 0,0:00:10.30,0:00:13.16,Default,,0000,0000,0000,,And by "here," I don't mean here.
Dialogue: 0,0:00:14.83,0:00:15.98,Default,,0000,0000,0000,,Or here.
Dialogue: 0,0:00:16.73,0:00:17.88,Default,,0000,0000,0000,,But here.
Dialogue: 0,0:00:17.90,0:00:19.05,Default,,0000,0000,0000,,I mean Earth.
Dialogue: 0,0:00:19.63,0:00:23.57,Default,,0000,0000,0000,,And by "we," I don't mean\Nthose of us in this auditorium,
Dialogue: 0,0:00:23.59,0:00:25.06,Default,,0000,0000,0000,,but life,
Dialogue: 0,0:00:25.09,0:00:26.54,Default,,0000,0000,0000,,all life on Earth --
Dialogue: 0,0:00:26.56,0:00:31.94,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:00:32.28,0:00:34.27,Default,,0000,0000,0000,,from complex to single-celled,
Dialogue: 0,0:00:34.30,0:00:36.62,Default,,0000,0000,0000,,from mold to mushrooms
Dialogue: 0,0:00:36.64,0:00:38.02,Default,,0000,0000,0000,,to flying bears.
Dialogue: 0,0:00:38.04,0:00:39.41,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:00:41.74,0:00:43.24,Default,,0000,0000,0000,,The interesting thing is,
Dialogue: 0,0:00:43.27,0:00:46.30,Default,,0000,0000,0000,,Earth is the only place\Nwe know of that has life --
Dialogue: 0,0:00:46.32,0:00:48.20,Default,,0000,0000,0000,,8.7 million species.
Dialogue: 0,0:00:48.66,0:00:49.91,Default,,0000,0000,0000,,We've looked other places,
Dialogue: 0,0:00:49.94,0:00:52.04,Default,,0000,0000,0000,,maybe not as hard\Nas we should or we could,
Dialogue: 0,0:00:52.06,0:00:53.99,Default,,0000,0000,0000,,but we've looked and haven't found any;
Dialogue: 0,0:00:54.01,0:00:56.29,Default,,0000,0000,0000,,Earth is the only place\Nwe know of with life.
Dialogue: 0,0:00:57.32,0:00:58.59,Default,,0000,0000,0000,,Is Earth special?
Dialogue: 0,0:00:59.59,0:01:02.04,Default,,0000,0000,0000,,This is a question I've wanted\Nto know the answer to
Dialogue: 0,0:01:02.07,0:01:03.32,Default,,0000,0000,0000,,since I was a small child,
Dialogue: 0,0:01:03.35,0:01:05.38,Default,,0000,0000,0000,,and I suspect 80 percent\Nof this auditorium
Dialogue: 0,0:01:05.40,0:01:08.41,Default,,0000,0000,0000,,has thought the same thing\Nand also wanted to know the answer.
Dialogue: 0,0:01:08.88,0:01:11.05,Default,,0000,0000,0000,,To understand whether\Nthere are any planets --
Dialogue: 0,0:01:11.07,0:01:13.35,Default,,0000,0000,0000,,out there in our solar system or beyond --
Dialogue: 0,0:01:13.37,0:01:14.83,Default,,0000,0000,0000,,that can support life,
Dialogue: 0,0:01:14.85,0:01:18.05,Default,,0000,0000,0000,,the first step is to understand\Nwhat life here requires.
Dialogue: 0,0:01:18.58,0:01:22.14,Default,,0000,0000,0000,,It turns out, of all of those\N8.7 million species,
Dialogue: 0,0:01:22.16,0:01:24.36,Default,,0000,0000,0000,,life only needs three things.
Dialogue: 0,0:01:25.03,0:01:27.88,Default,,0000,0000,0000,,On one side, all life\Non Earth needs energy.
Dialogue: 0,0:01:27.91,0:01:31.39,Default,,0000,0000,0000,,Complex life like us derives\Nour energy from the sun,
Dialogue: 0,0:01:31.42,0:01:33.52,Default,,0000,0000,0000,,but life deep underground\Ncan get its energy
Dialogue: 0,0:01:33.54,0:01:35.26,Default,,0000,0000,0000,,from things like chemical reactions.
Dialogue: 0,0:01:35.29,0:01:37.44,Default,,0000,0000,0000,,There are a number\Nof different energy sources
Dialogue: 0,0:01:37.46,0:01:38.71,Default,,0000,0000,0000,,available on all planets.
Dialogue: 0,0:01:39.40,0:01:40.56,Default,,0000,0000,0000,,On the other side,
Dialogue: 0,0:01:40.58,0:01:43.28,Default,,0000,0000,0000,,all life needs food or nourishment.
Dialogue: 0,0:01:43.74,0:01:48.22,Default,,0000,0000,0000,,And this seems like a tall order,\Nespecially if you want a succulent tomato.
Dialogue: 0,0:01:48.24,0:01:49.96,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:01:49.98,0:01:53.04,Default,,0000,0000,0000,,However, all life on Earth\Nderives its nourishment
Dialogue: 0,0:01:53.07,0:01:55.10,Default,,0000,0000,0000,,from only six chemical elements,
Dialogue: 0,0:01:55.12,0:01:58.13,Default,,0000,0000,0000,,and these elements can be found\Non any planetary body
Dialogue: 0,0:01:58.15,0:01:59.49,Default,,0000,0000,0000,,in our solar system.
Dialogue: 0,0:02:00.54,0:02:03.76,Default,,0000,0000,0000,,So that leaves the thing\Nin the middle as the tall pole,
Dialogue: 0,0:02:03.79,0:02:05.74,Default,,0000,0000,0000,,the thing that's hardest to achieve.
Dialogue: 0,0:02:05.77,0:02:07.66,Default,,0000,0000,0000,,Not moose, but water.
Dialogue: 0,0:02:07.68,0:02:10.46,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:02:11.28,0:02:13.08,Default,,0000,0000,0000,,Although moose would be pretty cool.
Dialogue: 0,0:02:13.10,0:02:14.26,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:02:14.28,0:02:19.82,Default,,0000,0000,0000,,And not frozen water, and not water\Nin a gaseous state, but liquid water.
Dialogue: 0,0:02:20.75,0:02:23.20,Default,,0000,0000,0000,,This is what life needs\Nto survive, all life.
Dialogue: 0,0:02:23.68,0:02:27.02,Default,,0000,0000,0000,,And many solar system bodies\Ndon't have liquid water,
Dialogue: 0,0:02:27.04,0:02:28.68,Default,,0000,0000,0000,,and so we don't look there.
Dialogue: 0,0:02:28.70,0:02:31.69,Default,,0000,0000,0000,,Other solar system bodies\Nmight have abundant liquid water,
Dialogue: 0,0:02:31.72,0:02:33.05,Default,,0000,0000,0000,,even more than Earth,
Dialogue: 0,0:02:33.08,0:02:35.53,Default,,0000,0000,0000,,but it's trapped beneath an icy shell,
Dialogue: 0,0:02:35.55,0:02:37.81,Default,,0000,0000,0000,,and so it's hard to access,\Nit's hard to get to,
Dialogue: 0,0:02:37.84,0:02:40.55,Default,,0000,0000,0000,,it's hard to even find out\Nif there's any life there.
Dialogue: 0,0:02:41.48,0:02:44.47,Default,,0000,0000,0000,,So that leaves a few bodies\Nthat we should think about.
Dialogue: 0,0:02:44.49,0:02:46.92,Default,,0000,0000,0000,,So let's make the problem\Nsimpler for ourselves.
Dialogue: 0,0:02:46.95,0:02:50.29,Default,,0000,0000,0000,,Let's think only about liquid water\Non the surface of a planet.
Dialogue: 0,0:02:50.31,0:02:53.27,Default,,0000,0000,0000,,There are only three bodies\Nto think about in our solar system,
Dialogue: 0,0:02:53.29,0:02:55.87,Default,,0000,0000,0000,,with regard to liquid water\Non the surface of a planet,
Dialogue: 0,0:02:55.90,0:03:00.72,Default,,0000,0000,0000,,and in order of distance from the sun,\Nit's: Venus, Earth and Mars.
Dialogue: 0,0:03:01.26,0:03:04.64,Default,,0000,0000,0000,,You want to have an atmosphere\Nfor water to be liquid.
Dialogue: 0,0:03:04.66,0:03:07.04,Default,,0000,0000,0000,,You have to be very careful\Nwith that atmosphere.
Dialogue: 0,0:03:07.06,0:03:10.48,Default,,0000,0000,0000,,You can't have too much atmosphere,\Ntoo thick or too warm an atmosphere,
Dialogue: 0,0:03:10.50,0:03:13.40,Default,,0000,0000,0000,,because then you end up\Ntoo hot like Venus,
Dialogue: 0,0:03:13.43,0:03:15.16,Default,,0000,0000,0000,,and you can't have liquid water.
Dialogue: 0,0:03:15.19,0:03:19.14,Default,,0000,0000,0000,,But if you have too little atmosphere\Nand it's too thin and too cold,
Dialogue: 0,0:03:19.17,0:03:21.19,Default,,0000,0000,0000,,you end up like Mars, too cold.
Dialogue: 0,0:03:21.86,0:03:24.34,Default,,0000,0000,0000,,So Venus is too hot, Mars is too cold,
Dialogue: 0,0:03:24.36,0:03:25.53,Default,,0000,0000,0000,,and Earth is just right.
Dialogue: 0,0:03:25.55,0:03:29.03,Default,,0000,0000,0000,,You can look at these images behind me\Nand you can see automatically
Dialogue: 0,0:03:29.05,0:03:31.65,Default,,0000,0000,0000,,where life can survive\Nin our solar system.
Dialogue: 0,0:03:32.30,0:03:33.90,Default,,0000,0000,0000,,It's a Goldilocks-type problem,
Dialogue: 0,0:03:33.92,0:03:36.41,Default,,0000,0000,0000,,and it's so simple\Nthat a child could understand it.
Dialogue: 0,0:03:37.45,0:03:38.63,Default,,0000,0000,0000,,However,
Dialogue: 0,0:03:39.45,0:03:42.38,Default,,0000,0000,0000,,I'd like to remind you of two things
Dialogue: 0,0:03:42.40,0:03:45.36,Default,,0000,0000,0000,,from the Goldilocks story\Nthat we may not think about so often
Dialogue: 0,0:03:45.38,0:03:47.48,Default,,0000,0000,0000,,but that I think are really relevant here.
Dialogue: 0,0:03:48.06,0:03:49.21,Default,,0000,0000,0000,,Number one:
Dialogue: 0,0:03:50.31,0:03:53.10,Default,,0000,0000,0000,,if Mama Bear's bowl is too cold
Dialogue: 0,0:03:53.83,0:03:55.84,Default,,0000,0000,0000,,when Goldilocks walks into the room,
Dialogue: 0,0:03:56.64,0:03:58.78,Default,,0000,0000,0000,,does that mean it's always been too cold?
Dialogue: 0,0:03:59.82,0:04:03.09,Default,,0000,0000,0000,,Or could it have been just right\Nat some other time?
Dialogue: 0,0:04:03.65,0:04:07.33,Default,,0000,0000,0000,,When Goldilocks walks into the room\Ndetermines the answer
Dialogue: 0,0:04:07.36,0:04:08.69,Default,,0000,0000,0000,,that we get in the story.
Dialogue: 0,0:04:09.11,0:04:10.84,Default,,0000,0000,0000,,And the same is true with planets.
Dialogue: 0,0:04:10.87,0:04:12.89,Default,,0000,0000,0000,,They're not static things. They change.
Dialogue: 0,0:04:12.92,0:04:14.66,Default,,0000,0000,0000,,They vary. They evolve.
Dialogue: 0,0:04:14.68,0:04:16.73,Default,,0000,0000,0000,,And atmospheres do the same.
Dialogue: 0,0:04:16.75,0:04:18.45,Default,,0000,0000,0000,,So let me give you an example.
Dialogue: 0,0:04:18.48,0:04:20.48,Default,,0000,0000,0000,,Here's one of my favorite\Npictures of Mars.
Dialogue: 0,0:04:20.50,0:04:23.63,Default,,0000,0000,0000,,It's not the highest resolution image,\Nit's not the sexiest image,
Dialogue: 0,0:04:23.66,0:04:25.16,Default,,0000,0000,0000,,it's not the most recent image,
Dialogue: 0,0:04:25.18,0:04:28.68,Default,,0000,0000,0000,,but it's an image that shows riverbeds\Ncut into the surface of the planet;
Dialogue: 0,0:04:29.32,0:04:31.90,Default,,0000,0000,0000,,riverbeds carved by flowing, liquid water;
Dialogue: 0,0:04:33.52,0:04:38.40,Default,,0000,0000,0000,,riverbeds that take hundreds or thousands\Nor tens of thousands of years to form.
Dialogue: 0,0:04:38.42,0:04:40.04,Default,,0000,0000,0000,,This can't happen on Mars today.
Dialogue: 0,0:04:40.07,0:04:42.55,Default,,0000,0000,0000,,The atmosphere of Mars today\Nis too thin and too cold
Dialogue: 0,0:04:42.57,0:04:44.71,Default,,0000,0000,0000,,for water to be stable as a liquid.
Dialogue: 0,0:04:44.74,0:04:49.08,Default,,0000,0000,0000,,This one image tells you\Nthat the atmosphere of Mars changed,
Dialogue: 0,0:04:49.11,0:04:51.14,Default,,0000,0000,0000,,and it changed in big ways.
Dialogue: 0,0:04:51.71,0:04:56.52,Default,,0000,0000,0000,,And it changed from a state\Nthat we would define as habitable,
Dialogue: 0,0:04:56.55,0:05:00.14,Default,,0000,0000,0000,,because the three requirements\Nfor life were present long ago.
Dialogue: 0,0:05:01.05,0:05:03.12,Default,,0000,0000,0000,,Where did that atmosphere go
Dialogue: 0,0:05:03.14,0:05:05.96,Default,,0000,0000,0000,,that allowed water\Nto be liquid at the surface?
Dialogue: 0,0:05:05.98,0:05:09.33,Default,,0000,0000,0000,,Well, one idea is it escaped\Naway to space.
Dialogue: 0,0:05:09.36,0:05:12.02,Default,,0000,0000,0000,,Atmospheric particles\Ngot enough energy to break free
Dialogue: 0,0:05:12.05,0:05:13.70,Default,,0000,0000,0000,,from the gravity of the planet,
Dialogue: 0,0:05:13.72,0:05:16.41,Default,,0000,0000,0000,,escaping away to space, never to return.
Dialogue: 0,0:05:16.44,0:05:19.12,Default,,0000,0000,0000,,And this happens with all bodies\Nwith atmospheres.
Dialogue: 0,0:05:19.15,0:05:20.32,Default,,0000,0000,0000,,Comets have tails
Dialogue: 0,0:05:20.34,0:05:23.60,Default,,0000,0000,0000,,that are incredibly visible reminders\Nof atmospheric escape.
Dialogue: 0,0:05:23.63,0:05:27.04,Default,,0000,0000,0000,,But Venus also has an atmosphere\Nthat escapes with time,
Dialogue: 0,0:05:27.06,0:05:28.72,Default,,0000,0000,0000,,and Mars and Earth as well.
Dialogue: 0,0:05:28.74,0:05:31.71,Default,,0000,0000,0000,,It's just a matter of degree\Nand a matter of scale.
Dialogue: 0,0:05:32.09,0:05:34.77,Default,,0000,0000,0000,,So we'd like to figure out\Nhow much escaped over time
Dialogue: 0,0:05:34.79,0:05:36.91,Default,,0000,0000,0000,,so we can explain this transition.
Dialogue: 0,0:05:36.93,0:05:39.54,Default,,0000,0000,0000,,How do atmospheres\Nget their energy for escape?
Dialogue: 0,0:05:39.57,0:05:41.70,Default,,0000,0000,0000,,How do particles get\Nenough energy to escape?
Dialogue: 0,0:05:41.72,0:05:44.91,Default,,0000,0000,0000,,There are two ways, if we're going\Nto reduce things a little bit.
Dialogue: 0,0:05:44.93,0:05:46.08,Default,,0000,0000,0000,,Number one, sunlight.
Dialogue: 0,0:05:46.11,0:05:49.52,Default,,0000,0000,0000,,Light emitted from the sun can be absorbed\Nby atmospheric particles
Dialogue: 0,0:05:49.54,0:05:51.26,Default,,0000,0000,0000,,and warm the particles.
Dialogue: 0,0:05:51.28,0:05:53.39,Default,,0000,0000,0000,,Yes, I'm dancing, but they --
Dialogue: 0,0:05:53.41,0:05:54.88,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:05:55.69,0:05:57.60,Default,,0000,0000,0000,,Oh my God, not even at my wedding.
Dialogue: 0,0:05:57.63,0:05:59.12,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:05:59.14,0:06:02.15,Default,,0000,0000,0000,,They get enough energy\Nto escape and break free
Dialogue: 0,0:06:02.17,0:06:04.67,Default,,0000,0000,0000,,from the gravity of the planet\Njust by warming.
Dialogue: 0,0:06:04.70,0:06:07.86,Default,,0000,0000,0000,,A second way they can get energy\Nis from the solar wind.
Dialogue: 0,0:06:07.88,0:06:12.91,Default,,0000,0000,0000,,These are particles, mass, material,\Nspit out from the surface of the sun,
Dialogue: 0,0:06:12.93,0:06:15.34,Default,,0000,0000,0000,,and they go screaming\Nthrough the solar system
Dialogue: 0,0:06:15.36,0:06:17.14,Default,,0000,0000,0000,,at 400 kilometers per second,
Dialogue: 0,0:06:17.17,0:06:19.76,Default,,0000,0000,0000,,sometimes faster during solar storms,
Dialogue: 0,0:06:19.79,0:06:22.51,Default,,0000,0000,0000,,and they go hurtling\Nthrough interplanetary space
Dialogue: 0,0:06:22.53,0:06:24.98,Default,,0000,0000,0000,,towards planets and their atmospheres,
Dialogue: 0,0:06:25.00,0:06:26.63,Default,,0000,0000,0000,,and they may provide energy
Dialogue: 0,0:06:26.65,0:06:28.78,Default,,0000,0000,0000,,for atmospheric particles\Nto escape as well.
Dialogue: 0,0:06:29.18,0:06:31.15,Default,,0000,0000,0000,,This is something that I'm interested in,
Dialogue: 0,0:06:31.18,0:06:32.89,Default,,0000,0000,0000,,because it relates to habitability.
Dialogue: 0,0:06:33.38,0:06:36.51,Default,,0000,0000,0000,,I mentioned that there were two things\Nabout the Goldilocks story
Dialogue: 0,0:06:36.53,0:06:39.52,Default,,0000,0000,0000,,that I wanted to bring to your attention\Nand remind you about,
Dialogue: 0,0:06:39.54,0:06:41.78,Default,,0000,0000,0000,,and the second one\Nis a little bit more subtle.
Dialogue: 0,0:06:41.80,0:06:44.59,Default,,0000,0000,0000,,If Papa Bear's bowl is too hot,
Dialogue: 0,0:06:46.18,0:06:49.41,Default,,0000,0000,0000,,and Mama Bear's bowl is too cold,
Dialogue: 0,0:06:51.06,0:06:54.17,Default,,0000,0000,0000,,shouldn't Baby Bear's bowl be even colder
Dialogue: 0,0:06:55.08,0:06:56.88,Default,,0000,0000,0000,,if we're following the trend?
Dialogue: 0,0:06:58.20,0:07:00.51,Default,,0000,0000,0000,,This thing that you've accepted\Nyour entire life,
Dialogue: 0,0:07:00.53,0:07:03.60,Default,,0000,0000,0000,,when you think about it a little bit more,\Nmay not be so simple.
Dialogue: 0,0:07:04.51,0:07:08.54,Default,,0000,0000,0000,,And of course, distance of a planet\Nfrom the sun determines its temperature.
Dialogue: 0,0:07:08.56,0:07:10.83,Default,,0000,0000,0000,,This has to play into habitability.
Dialogue: 0,0:07:10.86,0:07:13.78,Default,,0000,0000,0000,,But maybe there are other things\Nwe should be thinking about.
Dialogue: 0,0:07:13.81,0:07:15.42,Default,,0000,0000,0000,,Maybe it's the bowls themselves
Dialogue: 0,0:07:15.45,0:07:18.50,Default,,0000,0000,0000,,that are also helping to determine\Nthe outcome in the story,
Dialogue: 0,0:07:18.53,0:07:19.83,Default,,0000,0000,0000,,what is just right.
Dialogue: 0,0:07:20.76,0:07:23.63,Default,,0000,0000,0000,,I could talk to you about a lot\Nof different characteristics
Dialogue: 0,0:07:23.65,0:07:24.80,Default,,0000,0000,0000,,of these three planets
Dialogue: 0,0:07:24.83,0:07:26.40,Default,,0000,0000,0000,,that may influence habitability,
Dialogue: 0,0:07:26.42,0:07:29.02,Default,,0000,0000,0000,,but for selfish reasons related\Nto my own research
Dialogue: 0,0:07:29.04,0:07:32.63,Default,,0000,0000,0000,,and the fact that I'm standing up here\Nholding the clicker and you're not --
Dialogue: 0,0:07:32.65,0:07:33.66,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:07:33.68,0:07:35.79,Default,,0000,0000,0000,,I would like to talk\Nfor just a minute or two
Dialogue: 0,0:07:35.82,0:07:37.11,Default,,0000,0000,0000,,about magnetic fields.
Dialogue: 0,0:07:37.72,0:07:40.25,Default,,0000,0000,0000,,Earth has one; Venus and Mars do not.
Dialogue: 0,0:07:40.82,0:07:43.95,Default,,0000,0000,0000,,Magnetic fields are generated\Nin the deep interior of a planet
Dialogue: 0,0:07:43.97,0:07:47.69,Default,,0000,0000,0000,,by electrically conducting\Nchurning fluid material
Dialogue: 0,0:07:47.71,0:07:50.62,Default,,0000,0000,0000,,that creates this big old magnetic field\Nthat surrounds Earth.
Dialogue: 0,0:07:50.64,0:07:53.04,Default,,0000,0000,0000,,If you have a compass,\Nyou know which way north is.
Dialogue: 0,0:07:53.06,0:07:54.56,Default,,0000,0000,0000,,Venus and Mars don't have that.
Dialogue: 0,0:07:54.58,0:07:56.49,Default,,0000,0000,0000,,If you have a compass on Venus and Mars,
Dialogue: 0,0:07:56.52,0:07:57.91,Default,,0000,0000,0000,,congratulations, you're lost.
Dialogue: 0,0:07:57.94,0:07:59.84,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:07:59.86,0:08:01.90,Default,,0000,0000,0000,,Does this influence habitability?
Dialogue: 0,0:08:03.18,0:08:04.48,Default,,0000,0000,0000,,Well, how might it?
Dialogue: 0,0:08:05.02,0:08:07.63,Default,,0000,0000,0000,,Many scientists think\Nthat a magnetic field of a planet
Dialogue: 0,0:08:07.65,0:08:10.05,Default,,0000,0000,0000,,serves as a shield for the atmosphere,
Dialogue: 0,0:08:10.07,0:08:13.43,Default,,0000,0000,0000,,deflecting solar wind particles\Naround the planet
Dialogue: 0,0:08:13.45,0:08:15.26,Default,,0000,0000,0000,,in a bit of a force field-type effect
Dialogue: 0,0:08:15.29,0:08:17.99,Default,,0000,0000,0000,,having to do with electric charge\Nof those particles.
Dialogue: 0,0:08:18.36,0:08:21.99,Default,,0000,0000,0000,,I like to think of it instead\Nas a salad bar sneeze guard for planets.
Dialogue: 0,0:08:22.01,0:08:24.29,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:08:24.96,0:08:28.34,Default,,0000,0000,0000,,And yes, my colleagues\Nwho watch this later will realize
Dialogue: 0,0:08:28.37,0:08:30.91,Default,,0000,0000,0000,,this is the first time in the history\Nof our community
Dialogue: 0,0:08:30.94,0:08:33.21,Default,,0000,0000,0000,,that the solar wind has been\Nequated with mucus.
Dialogue: 0,0:08:33.24,0:08:34.89,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:08:36.98,0:08:40.45,Default,,0000,0000,0000,,OK, so the effect, then, is that Earth\Nmay have been protected
Dialogue: 0,0:08:40.48,0:08:41.64,Default,,0000,0000,0000,,for billions of years,
Dialogue: 0,0:08:41.67,0:08:43.52,Default,,0000,0000,0000,,because we've had a magnetic field.
Dialogue: 0,0:08:43.54,0:08:45.72,Default,,0000,0000,0000,,Atmosphere hasn't been able to escape.
Dialogue: 0,0:08:45.75,0:08:47.85,Default,,0000,0000,0000,,Mars, on the other hand,\Nhas been unprotected
Dialogue: 0,0:08:47.88,0:08:49.72,Default,,0000,0000,0000,,because of its lack of magnetic field,
Dialogue: 0,0:08:49.74,0:08:51.70,Default,,0000,0000,0000,,and over billions of years,
Dialogue: 0,0:08:51.72,0:08:53.90,Default,,0000,0000,0000,,maybe enough atmosphere\Nhas been stripped away
Dialogue: 0,0:08:53.92,0:08:56.52,Default,,0000,0000,0000,,to account for a transition\Nfrom a habitable planet
Dialogue: 0,0:08:56.54,0:08:58.21,Default,,0000,0000,0000,,to the planet that we see today.
Dialogue: 0,0:08:59.06,0:09:02.05,Default,,0000,0000,0000,,Other scientists think\Nthat magnetic fields
Dialogue: 0,0:09:02.07,0:09:04.24,Default,,0000,0000,0000,,may act more like the sails on a ship,
Dialogue: 0,0:09:04.96,0:09:09.100,Default,,0000,0000,0000,,enabling the planet to interact\Nwith more energy from the solar wind
Dialogue: 0,0:09:10.02,0:09:13.29,Default,,0000,0000,0000,,than the planet would have been able\Nto interact with by itself.
Dialogue: 0,0:09:13.32,0:09:15.81,Default,,0000,0000,0000,,The sails may gather energy\Nfrom the solar wind.
Dialogue: 0,0:09:15.83,0:09:18.50,Default,,0000,0000,0000,,The magnetic field may gather\Nenergy from the solar wind
Dialogue: 0,0:09:18.52,0:09:21.76,Default,,0000,0000,0000,,that allows even more\Natmospheric escape to happen.
Dialogue: 0,0:09:21.79,0:09:24.04,Default,,0000,0000,0000,,It's an idea that has to be tested,
Dialogue: 0,0:09:24.07,0:09:25.95,Default,,0000,0000,0000,,but the effect and how it works
Dialogue: 0,0:09:25.98,0:09:27.13,Default,,0000,0000,0000,,seems apparent.
Dialogue: 0,0:09:27.15,0:09:28.30,Default,,0000,0000,0000,,That's because we know
Dialogue: 0,0:09:28.32,0:09:31.40,Default,,0000,0000,0000,,energy from the solar wind\Nis being deposited into our atmosphere
Dialogue: 0,0:09:31.42,0:09:32.58,Default,,0000,0000,0000,,here on Earth.
Dialogue: 0,0:09:32.60,0:09:35.00,Default,,0000,0000,0000,,That energy is conducted\Nalong magnetic field lines
Dialogue: 0,0:09:35.03,0:09:36.38,Default,,0000,0000,0000,,down into the polar regions,
Dialogue: 0,0:09:36.40,0:09:38.54,Default,,0000,0000,0000,,resulting in incredibly beautiful aurora.
Dialogue: 0,0:09:38.56,0:09:41.22,Default,,0000,0000,0000,,If you've ever experienced them,\Nit's magnificent.
Dialogue: 0,0:09:41.24,0:09:43.25,Default,,0000,0000,0000,,We know the energy is getting in.
Dialogue: 0,0:09:43.27,0:09:46.30,Default,,0000,0000,0000,,We're trying to measure\Nhow many particles are getting out
Dialogue: 0,0:09:46.33,0:09:49.36,Default,,0000,0000,0000,,and if the magnetic field\Nis influencing this in any way.
Dialogue: 0,0:09:50.72,0:09:53.10,Default,,0000,0000,0000,,So I've posed a problem for you here,
Dialogue: 0,0:09:53.13,0:09:54.67,Default,,0000,0000,0000,,but I don't have a solution yet.
Dialogue: 0,0:09:54.70,0:09:55.97,Default,,0000,0000,0000,,We don't have a solution.
Dialogue: 0,0:09:56.70,0:09:59.06,Default,,0000,0000,0000,,But we're working on it.\NHow are we working on it?
Dialogue: 0,0:09:59.08,0:10:01.38,Default,,0000,0000,0000,,Well, we've sent spacecraft\Nto all three planets.
Dialogue: 0,0:10:01.40,0:10:02.88,Default,,0000,0000,0000,,Some of them are orbiting now,
Dialogue: 0,0:10:02.90,0:10:05.98,Default,,0000,0000,0000,,including the MAVEN spacecraft\Nwhich is currently orbiting Mars,
Dialogue: 0,0:10:06.00,0:10:09.53,Default,,0000,0000,0000,,which I'm involved with\Nand which is led here,
Dialogue: 0,0:10:09.56,0:10:11.37,Default,,0000,0000,0000,,out of the University of Colorado.
Dialogue: 0,0:10:11.39,0:10:13.67,Default,,0000,0000,0000,,It's designed to measure\Natmospheric escape.
Dialogue: 0,0:10:14.02,0:10:16.50,Default,,0000,0000,0000,,We have similar measurements\Nfrom Venus and Earth.
Dialogue: 0,0:10:16.95,0:10:18.62,Default,,0000,0000,0000,,Once we have all our measurements,
Dialogue: 0,0:10:18.64,0:10:21.52,Default,,0000,0000,0000,,we can combine all these together,\Nand we can understand
Dialogue: 0,0:10:21.54,0:10:24.96,Default,,0000,0000,0000,,how all three planets interact\Nwith their space environment,
Dialogue: 0,0:10:24.98,0:10:26.14,Default,,0000,0000,0000,,with the surroundings.
Dialogue: 0,0:10:26.17,0:10:29.69,Default,,0000,0000,0000,,And we can decide whether magnetic fields\Nare important for habitability
Dialogue: 0,0:10:29.71,0:10:30.87,Default,,0000,0000,0000,,or not.
Dialogue: 0,0:10:30.90,0:10:33.16,Default,,0000,0000,0000,,Once we have that answer,\Nwhy should you care?
Dialogue: 0,0:10:33.18,0:10:34.48,Default,,0000,0000,0000,,I mean, I care deeply ...
Dialogue: 0,0:10:36.13,0:10:38.13,Default,,0000,0000,0000,,And financially as well, but deeply.
Dialogue: 0,0:10:38.16,0:10:40.00,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:10:40.76,0:10:42.68,Default,,0000,0000,0000,,First of all, an answer to this question
Dialogue: 0,0:10:42.70,0:10:44.81,Default,,0000,0000,0000,,will teach us more\Nabout these three planets,
Dialogue: 0,0:10:44.83,0:10:45.99,Default,,0000,0000,0000,,Venus, Earth and Mars,
Dialogue: 0,0:10:46.02,0:10:48.93,Default,,0000,0000,0000,,not only about how they interact\Nwith their environment today,
Dialogue: 0,0:10:48.95,0:10:50.88,Default,,0000,0000,0000,,but how they were billions of years ago,
Dialogue: 0,0:10:50.90,0:10:52.96,Default,,0000,0000,0000,,whether they were habitable\Nlong ago or not.
Dialogue: 0,0:10:52.99,0:10:54.63,Default,,0000,0000,0000,,It will teach us about atmospheres
Dialogue: 0,0:10:54.66,0:10:56.65,Default,,0000,0000,0000,,that surround us and that are close.
Dialogue: 0,0:10:57.13,0:10:59.31,Default,,0000,0000,0000,,But moreover, what we learn\Nfrom these planets
Dialogue: 0,0:10:59.34,0:11:01.36,Default,,0000,0000,0000,,can be applied to atmospheres everywhere,
Dialogue: 0,0:11:02.48,0:11:05.40,Default,,0000,0000,0000,,including planets that we're now\Nobserving around other stars.
Dialogue: 0,0:11:05.42,0:11:07.18,Default,,0000,0000,0000,,For example, the Kepler spacecraft,
Dialogue: 0,0:11:07.20,0:11:10.41,Default,,0000,0000,0000,,which is built and controlled\Nhere in Boulder,
Dialogue: 0,0:11:10.43,0:11:13.72,Default,,0000,0000,0000,,has been observing\Na postage stamp-sized region of the sky
Dialogue: 0,0:11:13.74,0:11:14.99,Default,,0000,0000,0000,,for a couple years now,
Dialogue: 0,0:11:15.01,0:11:17.24,Default,,0000,0000,0000,,and it's found thousands of planets --
Dialogue: 0,0:11:17.26,0:11:20.18,Default,,0000,0000,0000,,in one postage stamp-sized\Nregion of the sky
Dialogue: 0,0:11:20.20,0:11:24.29,Default,,0000,0000,0000,,that we don't think is any different\Nfrom any other part of the sky.
Dialogue: 0,0:11:24.82,0:11:26.62,Default,,0000,0000,0000,,We've gone, in 20 years,
Dialogue: 0,0:11:26.65,0:11:30.69,Default,,0000,0000,0000,,from knowing of zero planets\Noutside of our solar system,
Dialogue: 0,0:11:30.71,0:11:32.46,Default,,0000,0000,0000,,to now having so many,
Dialogue: 0,0:11:32.49,0:11:35.63,Default,,0000,0000,0000,,that we don't know\Nwhich ones to investigate first.
Dialogue: 0,0:11:37.27,0:11:38.73,Default,,0000,0000,0000,,Any lever will help.
Dialogue: 0,0:11:40.54,0:11:44.12,Default,,0000,0000,0000,,In fact, based on observations\Nthat Kepler's taken
Dialogue: 0,0:11:44.15,0:11:46.28,Default,,0000,0000,0000,,and other similar observations,
Dialogue: 0,0:11:46.30,0:11:47.47,Default,,0000,0000,0000,,we now believe that,
Dialogue: 0,0:11:47.49,0:11:52.19,Default,,0000,0000,0000,,of the 200 billion stars\Nin the Milky Way galaxy alone,
Dialogue: 0,0:11:52.79,0:11:57.39,Default,,0000,0000,0000,,on average, every star\Nhas at least one planet.
Dialogue: 0,0:11:58.82,0:12:00.32,Default,,0000,0000,0000,,In addition to that,
Dialogue: 0,0:12:00.35,0:12:06.05,Default,,0000,0000,0000,,estimates suggest there are somewhere\Nbetween 40 billion and 100 billion
Dialogue: 0,0:12:06.07,0:12:09.40,Default,,0000,0000,0000,,of those planets\Nthat we would define as habitable
Dialogue: 0,0:12:11.14,0:12:12.55,Default,,0000,0000,0000,,in just our galaxy.
Dialogue: 0,0:12:14.59,0:12:16.63,Default,,0000,0000,0000,,We have the observations of those planets,
Dialogue: 0,0:12:16.65,0:12:19.14,Default,,0000,0000,0000,,but we just don't know\Nwhich ones are habitable yet.
Dialogue: 0,0:12:19.16,0:12:22.76,Default,,0000,0000,0000,,It's a little bit like\Nbeing trapped on a red spot --
Dialogue: 0,0:12:22.79,0:12:23.96,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:12:23.98,0:12:25.22,Default,,0000,0000,0000,,on a stage
Dialogue: 0,0:12:26.18,0:12:29.74,Default,,0000,0000,0000,,and knowing that there are\Nother worlds out there
Dialogue: 0,0:12:31.04,0:12:33.82,Default,,0000,0000,0000,,and desperately wanting to know\Nmore about them,
Dialogue: 0,0:12:35.17,0:12:39.11,Default,,0000,0000,0000,,wanting to interrogate them and find out\Nif maybe just one or two of them
Dialogue: 0,0:12:39.13,0:12:40.74,Default,,0000,0000,0000,,are a little bit like you.
Dialogue: 0,0:12:42.24,0:12:44.80,Default,,0000,0000,0000,,You can't do that.\NYou can't go there, not yet.
Dialogue: 0,0:12:44.83,0:12:48.82,Default,,0000,0000,0000,,And so you have to use the tools\Nthat you've developed around you
Dialogue: 0,0:12:48.84,0:12:50.14,Default,,0000,0000,0000,,for Venus, Earth and Mars,
Dialogue: 0,0:12:50.16,0:12:52.98,Default,,0000,0000,0000,,and you have to apply them\Nto these other situations,
Dialogue: 0,0:12:53.00,0:12:57.70,Default,,0000,0000,0000,,and hope that you're making\Nreasonable inferences from the data,
Dialogue: 0,0:12:57.72,0:13:00.84,Default,,0000,0000,0000,,and that you're going to be able\Nto determine the best candidates
Dialogue: 0,0:13:00.86,0:13:03.26,Default,,0000,0000,0000,,for habitable planets,\Nand those that are not.
Dialogue: 0,0:13:04.14,0:13:06.85,Default,,0000,0000,0000,,In the end, and for now, at least,
Dialogue: 0,0:13:06.88,0:13:09.66,Default,,0000,0000,0000,,this is our red spot, right here.
Dialogue: 0,0:13:10.38,0:13:13.71,Default,,0000,0000,0000,,This is the only planet\Nthat we know of that's habitable,
Dialogue: 0,0:13:13.74,0:13:16.93,Default,,0000,0000,0000,,although very soon we may\Ncome to know of more.
Dialogue: 0,0:13:16.95,0:13:19.69,Default,,0000,0000,0000,,But for now, this is\Nthe only habitable planet,
Dialogue: 0,0:13:19.71,0:13:21.01,Default,,0000,0000,0000,,and this is our red spot.
Dialogue: 0,0:13:21.98,0:13:23.40,Default,,0000,0000,0000,,I'm really glad we're here.
Dialogue: 0,0:13:24.51,0:13:25.68,Default,,0000,0000,0000,,Thanks.
Dialogue: 0,0:13:25.71,0:13:28.94,Default,,0000,0000,0000,,(Applause)