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(ominous music)
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From the drama of our planet's origins
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and the birth of our solar system
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comes one of the most startling revelations
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of modern science.
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The solar system we see today, quiet, stable,
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was once a battlefield.
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Newborn planets blasted through space,
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competing for stable, circularized orbits
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inside a grunge-style mosh pit of gas and dust.
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For those that find the right balance,
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the prize is survival;
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for the rest, world-shattering destruction.
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A new look at the chaos of creation
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and a frightening possibility in our distant future.
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(dramatic music)
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(ethereal music)
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Mars.
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The Curiosity rover is searching for clues
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about the origins of the red planet.
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It confirms the presence of oxygen and nitrogen isotopes
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hidden in the rocks and soil.
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We use isotopes to try to figure out
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the history of planets,
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partly because they are immune to many of the changes,
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the chemical changes that occur
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when you have things like collisions and so forth.
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Isotopes, the relative abundances of these isotopes
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are like fingerprints.
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Curiosity confirms a unique mix
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of isotope fingerprints.
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The isotopes indicate that Mars formed elsewhere
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in the solar system and moved into our neighborhood.
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(dramatic music)
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Our solar system is full of oddities
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pointing to an imperfect birth
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and a malformed evolution.
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All of our planets go around the sun
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in the same direction that the sun is spinning.
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This is the same direction that the clouds
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within our original nebula began to rotate.
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Six planets spin around their poles in the same direction.
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For them, the sun rises in the east
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and sets in the west.
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Yet two planets spin the opposite direction.
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For Venus and Uranus, the sun rises in the west
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and sets in the east.
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Uranus not only has a retrograde spin,
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it rolls on its side like a bowling ball.
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At Neptune, the icy moon Triton orbits backwards,
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opposite from the direction of Neptune's spin.
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Do these planets spin backwards
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because they were rocked by titanic collisions in the past?
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So we see evidence in the architecture of the solar system
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for not only collisions, like Earth's moon
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and the fact that Venus is rotating in the wrong direction
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and Uranus is on its side, and so forth,
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all these things are attribute to collisions.
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We also see in the Asteroid Belt and in the Kuiper Belt --
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the outer asteroid belt, if you like --
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we see that the orbits of these things
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look like they've been disturbed.
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(dramatic music)
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Closer to home, our own Earth
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has an inexplicable 23-and-a-half degree tilt.
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Its spin axis is radically misaligned
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from its magnetic pole.
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And our moon is comparatively large for a planet our size.
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Now, a new theory may be able to explain
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many of these oddities.
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It is called the grand tack hypothesis.
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(intriguing music)
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Four-and-a-half to five billion years ago,
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a gas giant planet arose inside a primordial disc
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of gas and dust.
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Jupiter didn't just form where it is,
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but formed then moved inward towards the sun.
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As it spirals toward the sun,
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Jupiter herds asteroids and rubble.
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Jupiter's natural tendency is to drift in slowly
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through this debris field that it's traveling around.
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The inner solar system is also thick
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with gas and dust.
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The birth of our planetary system is well underway.
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Numerous worlds are born in this region,
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including the Earth.
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Primordial skies are ruled by chaos.
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Jupiter's approach destabilizes these planets.
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Their orbits decay into wildly swinging ellipses.
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Some are tossed out.
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Others fall into the sun.
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Their numbers are unknowable.
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These are ghost worlds from a bygone age.
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Jupiter just causes all heck to break out
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in the solar system, and all that debris
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in the outer solar system gets flung inward
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towards the inner solar system.
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And it was a busy time in the very early acts
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of our system, and things were colliding
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with each other all the time.
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And then it stopped.
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Jupiter's invasion of the inner solar system
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is mysteriously halted.
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The planet makes turn;
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or, in sailor's parlance, a grand tack.
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(dramatic music)
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Lurking behind Jupiter is a second gas giant.
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Saturn.
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So as Jupiter was migrating inward,
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Saturn was following it and growing.
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And as Saturn was growing it came to have a size
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that it had a gravitational impact on Jupiter,
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which became more important than the gravitational
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interaction between the gaseous disc and Jupiter.
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They reversed direction.
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In a sense you can think of Saturn and Jupiter
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feeding off one another and moving back out.
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Gravity tugs each passing planet.
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This transfers orbital energy from one world to another.
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All you have to do is exert a very subtle, little,
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periodic force at the right time,
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and you can have amazing changes in the motion
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of the object you're pushing on.
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Once enough energy has been transferred,
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the planets synchronize their orbits.
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They are said to be in a resonance.
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For planets, resonances are achieved and maintained
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through the mutual push and pull of gravity
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through the fabric of space.
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They're a key factor in the continuing evolution
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of our solar system.
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This effect can be duplicated in the lab.
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We have 10 metronomes here,
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set up on a swinging platform.
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They have little weights on pendulums here,
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but they've all been set at the same frequency.
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And I'm gonna try to start them as best I can
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completely out of phase, randomly,
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so their oscillation is going to transfer energy
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by the swinging of this plastic sheet
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to the other metronomes that are out of phase
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to get into phase with the majority.
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(metronome clicking)
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It's inevitable that there's going to be some majority group
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which starts out swinging more or less together,
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and they are eventually gonna win out.
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Just doing this as randomly as I can.
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(metronomes clicking)
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Aha!
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Maybe in this corner I see four
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that are pretty closely synced.
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Yes, now it's more like five.
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Six.
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Now you have one that's almost completely out of phase.
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Every time the majority hits a beat,
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it's going to give a little impulse,
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a little push to the platform, and that push is transferred
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to the metronome that's not in sync.
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Because the platform, you can actually see this platform
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vibrating back and forth in sync
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with the majority of these metronomes.
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Working on this one.
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So we're pretty close to resonance right now.
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As the metronomes achieve resonance,
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it's important to notice how the platform shakes.
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Now, it doesn't have to just be the force
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that's being transmitted by the plastic platform.
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It could be a force at a great distance,
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for example the force of gravity.
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Just the small, little, seemingly insignificant pushes
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building up over multiple cycles
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can have dramatic energy transfer.
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That is how planets do it.
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Like the metronomes,
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the two gas giants form a resonance.
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We don't know exactly how long that took.
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But we have some fiducial marks for timing
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in the solar system formation,
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and that means that the grand tack
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had to have occurred relatively quickly,
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talking hundreds of thousands of year, perhaps,
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to a million years.
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The two planets retreat
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until they reach their current positions.
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The sequence of planets as we find them today
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is based on Jupiter and Saturn's orbits.
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The planets eventually achieve a sequencing
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that many students learn through a mnemonic,
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such as "my very educated mother
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"just served us nine pizzas."
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Was there a time when the mnemonic was scrambled?
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Seems very likely the answer is yes,
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not to mention a lot of additional letters
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were probably in their as well.
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Jupiter's menace of the inner solar system
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is finally over.
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If Saturn had not formed at the right time
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and the sufficient size,
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Jupiter would have continued migrating in,
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throwing out objects, unfortunate objects
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in the inner solar system, and ending up
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very close to the sun, where it would stay.
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Yes, the Earth would be gone.
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Or the Earth would have had a terrifying encounter
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with Jupiter, and would have had its orbit
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changed dramatically to gosh knows what.
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There is mounting evidence
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that Earth had a terrifying visitor.
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Not Jupiter, but another world:
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Theia.
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Theia was essentially another proto-Earth,
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where there were a number of these object flying around,
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and Theia took time to grow, just like the Earth did.
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They probably had rather similar histories.
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And for one reason or another,
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the orbit of Theia was perturbed
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such that it collided with the Earth.
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(dramatic music)
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Theia was this planetary body
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that was roughly the size of Mars.
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And through this collision,
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a lot of particles were ejected.
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Probably completely destroyed.
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We don't really know how much of Theia was preserved.
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Earth is rocked off its axis.
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Its surface liquefied.
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Chunks of Earth's mantle are shoved into space.
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As a planetary body, Theia ceases to exist.
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Its remains are absorbed by the Earth
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and intermingled with the debris field.
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A new planetary body is formed:
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the moon.
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Further evidence is found in rock samples
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from the Apollo moon landings.
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This is a sample from the moon, if you can see it.
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This was collected by the Apollo 15 mission.
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Moon rocks contain isotopes
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identical to those found on Earth.
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When the moon arose, it is first covered with a magma ocean.
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People imagine the lunar magma ocean
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to be like this magmatic chamber I am describing,
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but at the surface and covering a whole planet.
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I see it as this ocean, like the Pacific,
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but this has to be completely magmatic orange
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and probably floating around and probably moving.
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Conditions in the lunar magma
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are as hellish as we can imagine.
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But a microscopic treasure forms in the magma:
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crystal zircons.
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These are the same gemstones used in jewelry,
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but the zircons in the Apollo moon rocks
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yield a different treasure.
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So those zircon are very important
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because we know they crystallized
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in this lunar magma ocean.
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We know roughly when they crystallized
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in the lunar magma ocean.
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So they are one of these old piece of the moon
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that we are looking for, one of these old piece
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that we can use to date the origin of the moon.
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Zircons not only give the age of the moon,
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they set a specific date for the collision.
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The age of the moon is 4.51 billion years old.
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4.51 billion years ago,
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Theia becomes part of Earth and forms the moon.
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But the story is not over.
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Space probes measure the moon
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slipping 3.8 centimeters further away each year.
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One day, the moon will break free.
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When that day comes, there will be no more tides,
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no more romantic moonlit nights.
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Could planetary orbits be inherently unstable?
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Could the chaos of planetary migration return?
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Haute-Provence Observatory, France.
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It's here that a discovery from a faraway star
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gives one of the biggest revelations
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about our own solar system.
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The story begins when Swiss astronomers, Didiet Queloz
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00:17:08,287 --> 00:17:11,449
and Michel Mayor, notice something unusual
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about a star 50 light-years away,
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in the constellation of Pegasus.
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Everything about this star is ordinary,
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a main sequence midlife yellow dwarf
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00:17:23,594 --> 00:17:28,527
just like our sun, but with one strange difference.
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The star at Pegasus 51 is rocking back and forth.
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It's a weird anomaly astronomers have never seen before.
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They check their instruments.
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Everything is working, including their new spectrograph,
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a device that splits the starlight from Pegasus
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into rainbow colors.
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Hidden inside the colors are patterns of lines.
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By tracking the day-to-day movement of these lines,
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astronomers make a startling discovery:
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Pegasus 51 has a planet.
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But no one has ever seen a world like this.
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It's half the mass of Jupiter,
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yet it's extremely close to its star;
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nine times closer than Mercury is to the sun.
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The planet at 51 Pegasus must be inside the corona,
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boiling at temperatures over a million degrees Fahrenheit.
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Soon, another planet is found around another star.
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And then another.
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And another.
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Astronomers have now confirmed over 3,700 exoplanets
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beyond our solar system, nearly all of them
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are Jupiter-class planets grazing their host star.
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They're a new, previously unknown type
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called hot Jupiters.
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They're so numerous, hot Jupiters challenge theories
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about the origins of planetary systems.
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It's very difficult to make a planet close to the star,
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because there isn't enough mass to build a giant planet
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very close to the star, and there's gravitational
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frustrations for trying to build a planet
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very close to the star.
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00:19:20,074 --> 00:19:24,241
Astronomy is shaken with a new revelation.
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Planets do not stay put where they're born.
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When they're big enough, they migrate.
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It's a process called planetary migration.
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00:19:35,657 --> 00:19:39,740
And yet, our own solar system has no hot Jupiter.
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Astronomers realize the Jupiter in our solar system
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00:19:50,321 --> 00:19:53,010
was once on the move as well.
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But its migration was halted by a resonance with Saturn.
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Pegasus 51 shows where a planet lands
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when its migration is not blocked.
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00:20:06,019 --> 00:20:09,174
The strongest evidence for the grand tack hypothesis
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comes not from our solar system
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but from exo-worlds charted around other stars.
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Planetary migration is a universal concept.
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We see it, evidence of it, out there
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in extra-solar planets, other solar systems.
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There's no reason why planet migration
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00:20:26,914 --> 00:20:30,914
shouldn't have operated in our own solar system.
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00:20:32,306 --> 00:20:34,973
(intense music)
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The New Horizons probe finds evidence
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00:20:41,183 --> 00:20:44,766
for roving planets within our solar system.
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While charting ancient craters on Pluto
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and on the surfaces of its moons,
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00:20:51,448 --> 00:20:56,399
the science team discovered many craters are the same age.
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This suggests that they were formed by a single event.
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00:21:00,317 --> 00:21:03,624
Even way out here, tiny Pluto was smashed
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by a wandering planet.
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The Pluto catastrophe may be related
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to other planetary migrations in the outer solar system.
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It was noticed that the exact orbits of the giant planets,
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particularly the outer giant planets,
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00:21:22,979 --> 00:21:25,547
the icy planet, Uranus and Neptune,
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00:21:25,547 --> 00:21:29,214
can be explained by their migration outward.
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There's a point in time about 3.8 billion years ago,
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where Uranus and Neptune trade.
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And it's because of what some of these mean motion resonance
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00:21:38,469 --> 00:21:41,269
interactions that we were talking about earlier.
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00:21:41,269 --> 00:21:42,630
So this mean motion resonance
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00:21:42,630 --> 00:21:44,285
involving Jupiter and Saturn and so forth
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just causes all heck to break out in the solar system.
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Uranus and Neptune all of a sudden
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at 3.8 billion years, they literally swap places
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and all that debris in the outer solar system
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gets flung inward towards the inner solar system.
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The disruption in the outer solar system
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causes a new wave of violence.
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Astronomers call this epic the late heavy bombardment.
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(dramatic music)
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Much of the cratering we see on our moon today
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is from this period.
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It may be possible that swapping orbits with Uranus
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is how Neptune got its moon.
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(ominous music)
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Today, the epic of planetary migration appears to be over.
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The solar system seems stable.
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But what does the future hold?
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Computer simulations reveal what may be
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the greatest threat to the solar system
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in over four billion years.
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It comes from a very special relationship
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between Jupiter and Mercury.
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Mercury's orbit is slowly perturbed
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thanks to a subtle but constant
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gravitational nudge from Jupiter.
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A new resonance like the one between Saturn and Jupiter
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that saved the inner solar system
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is forming between Jupiter and Mercury.
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In 2001, computer models for the solar system
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were run 2,500 times.
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They plug in the positions and the orbits
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00:23:38,322 --> 00:23:41,614
of all the planets in the solar system in a computer.
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And they just let it run through time,
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through millions of years, hundreds of millions of year,
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00:23:48,013 --> 00:23:50,075
billions of years, to find out whether or not
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these orbits are stable.
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Change the location of one planet, say Mercury,
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by one millimeter, and you find that that change
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00:24:03,528 --> 00:24:07,386
will give completely different predictions
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about where everything is going to be
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millions of years in the future.
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To see how quickly and easily things can change
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we have only to go back to our metronomes.
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All I have to do is stop this platform
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from moving so that it cannot swing freely.
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00:24:28,304 --> 00:24:30,765
Now there's no way for the metronomes
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to influence each other.
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They're good metronomes, but they're not perfect;
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they can't be going at exactly the same frequency
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and the same phase, and they're just going to fall apart,
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00:24:41,903 --> 00:24:45,006
because they have no way of forcing the others
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to go to resonance.
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00:24:48,129 --> 00:24:50,502
The same applies to planets.
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Any small change can disrupt their harmony
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00:24:53,249 --> 00:24:54,980
or restore it.
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Now that the platform is free to swing again,
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it can again transfer energy and sync them up
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just like we saw the first time.
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Scientists want to understand the consequences
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of a destabilized planet Mercury.
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In one case, Mercury leaves the solar system.
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The loss of its gravitational pull
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disrupts the balance of both Venus and the Earth.
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00:25:25,233 --> 00:25:27,566
Earth and Venus swap orbits.
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The super-heated atmosphere of Venus cools.
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Massive rains pour onto the face of the desert planet.
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Oceans arise.
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00:25:45,128 --> 00:25:46,378
The land cools.
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00:25:47,380 --> 00:25:48,880
And the air thins.
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00:25:50,118 --> 00:25:54,285
Even the remains of an ancient visitor begin to cool off.
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00:25:57,773 --> 00:25:59,856
Venus becomes like Earth.
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00:26:02,886 --> 00:26:06,635
But the reverse happens to the Earth.
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00:26:06,635 --> 00:26:10,802
As Earth settles into Venus's orbit, temperatures rise.
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00:26:11,745 --> 00:26:14,955
The air becomes unbreathable.
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00:26:14,955 --> 00:26:16,122
Glaciers melt.
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00:26:17,265 --> 00:26:18,265
Oceans boil.
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00:26:20,012 --> 00:26:22,312
The sun looms larger in the sky,
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00:26:22,312 --> 00:26:26,312
only to be obscured by a thickening cloud cover.
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00:26:27,327 --> 00:26:29,722
Suffering will be great,
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00:26:29,722 --> 00:26:30,555
but brief.
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00:26:32,176 --> 00:26:36,401
The entire four-billion-year pageant of life
436
00:26:36,401 --> 00:26:38,901
is cooked in a matter of days.
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00:26:41,419 --> 00:26:43,327
Complete and utter destruction
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00:26:43,327 --> 00:26:45,710
and elimination of all life on Earth.
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00:26:45,710 --> 00:26:47,481
I'm not just talking about higher life,
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00:26:47,481 --> 00:26:49,399
I'm not just talking about civilization,
441
00:26:49,399 --> 00:26:52,992
but everything, a sterilization of the planet
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00:26:52,992 --> 00:26:57,159
is something that I would want to think about a bit.
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00:26:59,331 --> 00:27:03,498
Sterilized, uninhabitable, and quiet.
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00:27:07,376 --> 00:27:11,543
There is another possibility, equally dark and apocalyptic.
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A runaway Mercury is deflected by the gravity of Venus
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00:27:19,412 --> 00:27:21,829
and barrels toward the Earth.
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00:27:23,427 --> 00:27:25,500
It may be a frightening encore
448
00:27:25,500 --> 00:27:28,750
to the opening act of our solar system.
449
00:27:30,348 --> 00:27:33,348
The equilibrium of the ages is over.
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00:27:37,800 --> 00:27:41,967
If this scenario is correct, Mercury crashes into the Earth
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00:27:43,084 --> 00:27:46,501
just as Theia did four billion years ago.
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00:27:50,224 --> 00:27:53,676
The question is: could it happen today?
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00:27:53,676 --> 00:27:56,343
(intense music)
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Or is it a fate far away in the future,
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at a time when mankind itself is but a distant memory?
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00:28:14,461 --> 00:28:17,833
The problem is that, even with a perfect computer
457
00:28:17,833 --> 00:28:20,784
that understands all of the laws of motion perfectly,
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00:28:20,784 --> 00:28:23,194
not just gravity but all the other subtle forces
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00:28:23,194 --> 00:28:27,810
that go into it, you cannot give it accurate enough
460
00:28:27,810 --> 00:28:30,431
initial information about the locations,
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00:28:30,431 --> 00:28:32,873
the masses, the sizes, the speeds
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00:28:32,873 --> 00:28:36,373
of all of the objects in the solar system.
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00:28:37,289 --> 00:28:41,573
Odds are we may never see such a calamity.
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00:28:41,573 --> 00:28:46,002
And yet, among the billions of stars in our galaxy,
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00:28:46,002 --> 00:28:49,226
how many worlds are on the move?
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How many will share this fate?
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(ominous music)
36282
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