Shadowing Practice: What Would Happen If an Asteroid Hit the Ocean? - Learn English Speaking with Video
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70 % of this planet is water, which means that if something falls out of the sky and hits us,
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the odds are overwhelmingly that it lands in the ocean rather than on land.
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Most people find that reassuring.
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The ocean feels like a cushion.
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It is deep, it is empty, and there are no cities out there to destroy.
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If a mountain of rock is going to fall on the earth,
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surely the middle of the Pacific is the best possible place for it to land.
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That instinct is completely understandable, and it is wrong in a way that took scientists a surprisingly long time to work out.
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Because water does not absorb an impact like that.
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Water does something far worse.
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It takes the energy, holds onto it and then carries it thousands of kilometers to a coastline where people actually live.
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And that is only the first of the three separate disasters an ocean impact sets in motion.
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And it is not the one that kills the most people.
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By the end of this you will understand why the ocean is not a cushion at all.
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It is a delivery system.
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Before we drop anything, we have to be honest about scale.
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Because asteroid hits the ocean covers an enormous range of outcomes, from nothing at all to the end of civilization.
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Small objects hit our atmosphere constantly.
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Every single day, tons of material from space runs into the Earth, and almost all of it burns up long before it reaches the surface.
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Those are the shooting stars you see on a clear night, and they pose no threat to anyone.
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Push the scale up to a few meters across, and you get the events that occasionally make the news.
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An object explodes in the upper atmosphere, produces a spectacular fireball, rattles some windows,
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and scatters fragments across a landscape.
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Anything landing in the ocean at that size vanishes without a single person noticing.
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The situation changes at somewhere in the region of a hundred meters.
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An object that size carries enough energy to survive the atmosphere and deliver a serious impact.
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And if it lands in water, it starts generating waves that matter.
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At around a kilometer, you are looking at a genuine global threat, regardless of where it hits.
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And at 10 to 15 kilometers, which is roughly the size of the object that ended the dinosaurs, the location almost stops mattering.
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That is not a regional disaster, that is a planetary reset.
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For most of this video, we are going to focus on the range that is actually most likely to happen in a human lifetime,
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which is the few hundred meter object, because that is where the odds and the consequences intersect most uncomfortably.
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But we will come back to the big one, because the day the dinosaurs died was an ocean impact,
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and what happened next is genuinely difficult to imagine.
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Picture a rocky object 300 meters across on a collision course with the middle of an ocean.
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It is traveling somewhere in the region of 20 kilometers per second.
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The first thing to understand is that at that speed our atmosphere barely exists.
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A hundred kilometers of air, the thing that protects every living creature on this planet, is crossed in a handful of seconds.
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The object compresses the air in front of it so violently that the air itself glows white -hot,
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and anyone within sight of the sky sees a light brighter than the sun tearing across it.
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Then it reaches the water and here is where our intuition fails us completely.
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When you imagine something falling into the sea, you probably picture a splash.
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Something enters, water parts, water closes over it, ripples spread out.
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That image is based on a lifetime of watching objects drop into water at ordinary speeds.
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At 20 km per second, water does not behave like a liquid at all.
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It does not have time to flow out of the way.
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On the time scale of the impact,
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seawater behaves more like a solid and the collision is closer to rock striking rock than to a stone hitting a pond.
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The object does not sink.
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It is.. destroyed.
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It is annihilated on contact, converting an enormous quantity of kinetic energy into heat and pressure in an instant,
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and in the process it vaporizes a colossal volume of seawater around it.
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What opens up in the ocean at that moment is not a splash.
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It is a crater in the water itself, A transient cavity that can be several kilometers across and,
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in deeper water, may reach all the way to the sea floor.
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For a brief moment, there is a hole in the ocean with steam -filled walls, and you could look down through it and see the seabed.
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The ocean, of course, does not tolerate that for long.
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The cavity begins collapsing almost immediately, and this is the moment that creates the disaster.
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Billions of tons of seawater rush inward from every direction to fill the hole.
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And all of that water arrives at the center at the same time, with nowhere left to go but up.
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It rebounds, forming an enormous column of water that rises high into the atmosphere before falling back and collapsing again.
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near the impact point we are potentially talking about waves hundreds of meters high
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now this is the point where most explanations of ocean impacts go badly wrong
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and I want to correct it carefully because the correction is actually more interesting than the myth
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The common claim is that an ocean impact produces a wall of water hundreds of meters tall
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that sweeps across the entire ocean and washes over continents.
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That version is not what the physics predicts, and it is worth understanding exactly why.
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Impact waves and earthquake tsunamis are not the same animal.
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An earthquake tsunami is generated when a long section of the seafloor, sometimes hundreds of kilometers of it, shifts vertically all at once.
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That displaces an enormous volume of water along a very long front, and it produces a wave with a very long wavelength.
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Long wavelength waves are extraordinarily efficient at crossing oceans, losing very little energy on the way,
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which is why a quake off one coast can devastate a shoreline on the far side of the world many hours later.
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An impact wave is generated by a single point and the waves it produces have much shorter wavelengths.
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Short wavelength waves lose energy far more rapidly as they spread.
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The wavefront expands outward as a growing circle and the same energy is distributed across an ever larger circumference,
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so the height falls off quickly with distance.
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So the honest picture is this.
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Close to the impact, the waves are apocalyptic and nothing survives.
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At intermediate distances, they are still catastrophic, and by the time they reach a distant continent, they may be far smaller than the myth suggests,
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though still large enough to be a serious coastal disaster.
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That sounds like good news, and up to a point it is, but there is a detail hiding in that reassurance that turns it around completely,
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and it has to do with where we choose to live.
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Here is the uncomfortable arithmetic.
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Something in the region of 40 % of humanity lives within 100 kilometers of a coast.
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The great cities of the world are overwhelmingly coastal because for the whole of human history,
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access to the sea has meant access to trade, food and travel.
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We built our civilization at the water's edge on purpose.
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That means the specific weakness of an ocean impact, its ability to convert energy into moving water,
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is aimed directly at where we keep almost half our population and a large fraction of our infrastructure.
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And there is a second problem that makes the wave heights out in the open ocean misleading.
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When a wave moves into shallow water near a coastline, it slows down and the energy it carries has to go somewhere.
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It goes upward.
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The wave grows dramatically as it approaches the shore, a process called shoaling.
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A wave that seems modest in deep water can become something entirely different when it arrives at a continental shelf.
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Local geography then makes it worse or better in ways that are extremely difficult to predict.
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A wave funneled into a narrowing bay is amplified.
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A wave arriving at a gently sloping shelf pushes much further inland.
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A map meeting a steep coastline may reflect and dissipate.
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So the real answer to how bad an ocean impact would be depends enormously on where in the ocean it lands,
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which coastlines face it, and the shape of the seabed leading up to them.
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An impact in the middle of the South Pacific and an impact in the North Atlantic are entirely different events for humanity.
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And all of that is still only the first of the three disasters.
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Because there is something else coming out of that impact site, and unlike the waves, it does not weaken with distance.
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Remember what happened in the first second.
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A colossal volume of seawater was vaporized instantly.
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That water does not disappear.
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It is thrown into the atmosphere as steam, along with pulverized rock and dust, and, if the impact reaches the sea floor,
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material excavated from the crust itself.
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An ocean impact injects an enormous quantity of water vapor into the upper atmosphere.
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Water vapor is a greenhouse gas.
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Large quantities of it high in the atmosphere can affect the planet's energy balance, and researchers studying ocean impacts have pointed out
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that this is a genuinely distinctive feature of a water strike compared to a land strike.
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There is also the question of what such an injection does to the ozone layer, which shields the surface from ultraviolet radiation.
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So you get competing effects, and the net outcome depends on the size of the impact and the specific conditions.
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The exact magnitude of all this is an area of active research rather than settled fact, And the honest position is
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that the climate consequences of a mid -sized ocean impact are less well understood than the wave effects.
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But the principle is clear.
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An ocean impact is not just a wave -making machine.
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It is also an atmospheric event, and the atmosphere does not stop at any coastline.
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And then there is the third disaster,
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which is the one that would probably kill the most people and it involves no water and no dust at all.
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Imagine the wave has come and gone.
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Imagine it struck a stretch of coastline somewhere in the world, destroying ports, cities, refineries, airports and rail links.
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Now think about what a modern civilization actually is.
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It is a network.
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Food is grown in one place and eaten thousands of kilometers away.
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Medicines are manufactured in a handful of facilities and distributed globally.
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Fuel moves by sea.
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Electronics move by sea.
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A staggering share of everything you own passed through a port at some point.
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And those ports are precisely what a tsunami destroys most efficiently.
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Modern supply chains are also optimized for efficiency rather than resilience.
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Most of what you buy is not sitting in a warehouse waiting for you.
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It is scheduled to arrive shortly before it is needed, because storage costs money.
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That system is extraordinarily efficient and extraordinarily fragile.
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Take out a cluster of major ports on one side of an ocean
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and the effects propagate through that network in ways
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that reach people who never saw the wave and live nowhere near the sea.
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Shortages appear in places that were physically untouched.
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Prices spike.
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Manufacturing stalls because a single component is no longer available.
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We have watched smaller versions of this happen in living memory,
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when a single blocked shipping route or one disrupted factory sent measurable ripples through the global economy for months.
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So the death toll from an ocean impact is not really a question about the height of a wave.
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It is a question about how well a globally interconnected civilization handles losing a section of its coastline.
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And the honest answer is that we do not know, because we have never tested it.
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Now, let us go back to the one that we know actually happened.
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66 million years ago, an object somewhere in the range of 10 to 15 km
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across across struck the earth near what is now the Yucatan Peninsula.
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That was an ocean impact.
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It landed in a shallow sea.
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At that scale, everything I have described stops being a regional disaster and becomes something else entirely.
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The waves generated were beyond anything in human experience,
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and evidence of enormous disturbance in the sediments around the Gulf region records their passage.
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But the waves were not what ended the dinosaurs, and this is the detail that matters most for understanding impact risk.
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The rock at that particular site was rich in sulfur -bearing minerals, and the impact vaporized it and threw it into the atmosphere,
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where it formed a haze that reflected sunlight away from the surface.
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Combined with soot from global wildfires and enormous quantities of dust, the result was a collapse in the sunlight reaching the ground.
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When sunlight fails, photosynthesis fails.
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And when photosynthesis fails, every food chain on the planet that depends on it comes apart from the bottom up.
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Around three -quarters of species on Earth died and every dinosaur larger than a house cat disappeared.
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So the lesson from the only large ocean impact in the record is a strange one.
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The water was not the main weapon, the atmosphere was.
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And that is worth holding on to because it means that when we assess the risk from a future impact,
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the question of what the object hits and what that material does
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when it is thrown into the sky may matter more than whether it lands on land or at sea.
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Here is the genuinely hopeful part, and it is not a small one.
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We are, as far as we know, the first species in the history of this planet with the ability to see one of these coming
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and do something about it.
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There are ongoing
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The following survey programs mapping near -earth objects and the large ones, the civilization -ending kilometer -plus objects,
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are the easiest to find because they are the brightest.
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A substantial proportion of that population has been catalogued
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and none of the known ones are on a collision course in the foreseeable future.
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Objects in the 100 to 300 meter range are much harder to spot, far more numerous and entirely capable of destroying a coastline.
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Those are the ones that could genuinely surprise us.
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That is not a complete planetary defense system, but it is a proof of concept,
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and it moves the whole problem out of the category of things we simply endure.
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The catch is time.
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Deflection works by making a very small change to an object's path a very long way in advance
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so that the tiny nudge compounds into a large miss by the time it reaches us.
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That requires years of warning, which requires finding the object first,
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which brings the entire subject back to something unglamorous.
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The single most valuable thing we can do about asteroid impacts is not build weapons.
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It is look.
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So what would happen if an asteroid hit the ocean.
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For a small object, nothing at all, and nobody would ever know.
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For something a few hundred meters across, a regional catastrophe aimed squarely at the coastlines where we have concentrated our cities,
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our ports, and nearly half of our species,
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followed by an economic disruption that would reach far inland to people who never saw a drop of the water.
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If you enjoyed this, subscribe, because we are only getting started.
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And tell us in the comments whether you think we would actually be ready.
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Watch next as we reconstruct the day the dinosaurs died, hour by hour.
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Vocabulary and speaking notes for this lesson
This speaking lesson is built on the video “What Would Happen If an Asteroid Hit the Ocean?”. The speaker keeps coming back to these words: impact, ocean, wave, object, atmosphere. This video has 193 sentences and 2662 words to shadow. The speech runs for 19:59. The speaker talks at a steady 133 words per minute, a comfortable pace for shadowing. Only 79% of the words are among the 3,000 most common in English, so the vocabulary is demanding.
Key vocabulary in this video
15 words from the video worth learning, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| atmosphere noun | /ˈætməsˌfɪɹ/ | The gases surrounding the Earth or any astronomical body. |
| coastline noun | The shape, outline, or boundary of a coast. (The term coastline is generally used to describe the approximate boundaries at relatively large spatial scales.) | |
| disaster noun | /dɪˈzɑːs.təː/ | An unexpected natural or man-made catastrophe of substantial extent causing significant physical damage or destruction, loss of life or sometimes permanent… |
| enormous adjective | /ɪˈnɔː.məs/ | Extremely large; greatly exceeding the common size, extent, etc. |
| meter noun | /ˈmitəɹ/ | A device that measures things. |
| civilization noun | /ˌsɪv.ɪ.laɪˈzeɪ.ʃən/ | An organized culture encompassing many communities, often on the scale of a nation or a people; a stage or system of social, political, or technical… |
| arrive verb | /əˈɹaɪv/ | To reach; to get to a certain place. |
| generate verb | /ˈd͡ʒɛn.ə.ɹeɪt/ | To bring into being; give rise to. |
| genuinely adverb | /ˈd͡ʒɛn.ju.ɪn.li/ | In a genuine manner; truthfully, truly. |
| quantity noun | /ˈkwɑn(t)ɪti/ | A fundamental, generic term used when referring to the measurement (count, amount) of a scalar, vector, number of items or to some other way of denominating… |
| dinosaur noun | /ˈdaɪnəsoɹ/ | Those animals of the clade Dinosauria that existed during the Triassic, Jurassic and Cretaceous periods and are now extinct. |
| dust noun | /dʌst/ | Fine, dry particles of matter found in the air and covering the surface of objects, typically consisting of soil lifted up by the wind, pollen, hair, fiber… |
| collapse verb | /kəˈlæps/ | To break apart and fall down suddenly; to cave in. |
| collision noun | /kəˈlɪʒn̩/ | An instance of colliding. |
| sunlight noun | /ˈsʌnˌlaɪt/ | All the electromagnetic radiation given off by the Sun; especially, that in the visible spectrum and that bathes the Earth. |
Phrasal verbs you will hear
| Word | Meaning |
|---|---|
| burn up verb | To catch fire and burn until destroyed. |
| fall back verb | To retreat. |
| fall off verb | To become detached or to drop from. |
| go back to verb | To stem from; to originate in. |
| lead up to verb | To set in motion; to act as a causal or preparatory event or sequence of events. |
| look down verb | To lower one's eyes; to direct one's look downwards. |
| pass through verb | To go through, to travel through, to transit or lie across a place or from one place to another. |
| point out verb | To identify among a group of similar subjects, or in a scene where the subject might not be readily seen or noticed, with a gesture of the body. |
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Passive voice be + past participle — the focus is on what happens, not who does it | is crossed · is based · is annihilated |
| Present perfect have/has + past participle — a past action that still matters now | has meant · have pointed · has come |
| Relative clauses who / which + clause — extra information about a person or thing | water, which means · kilometers, which is · people who never |
Pronunciation to watch
- The “th” sounds: earthquake /ˈɝθkweɪk/, myth /mɪθ/, wavelength /ˈweɪvˌlɛŋ(k)θ/, photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/
- The “sh” and “zh” sounds: civilization /ˌsɪv.ɪ.laɪˈzeɪ.ʃən/, collision /kəˈlɪʒn̩/, efficient /ɪˈfɪʃənt/, shallow /ˈʃæloʊ/, shelf /ʃɛlf/
- Long words — get the stress right: civilization /ˌsɪv.ɪ.laɪˈzeɪ.ʃən/, genuinely /ˈd͡ʒɛn.ju.ɪn.li/, humanity /hjuˈmænɪti/, planetary /ˈplænɪˌtɛəri/, overwhelmingly /ˌəʊ.vəˈwɛl.mɪŋ.lɪ/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Shadow it sentence by sentence at normal speed, repeating each one until your rhythm matches the speaker.
- Record yourself and compare with the original, paying attention to words like atmosphere, coastline, disaster.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.