シャドーイング練習: What If We Moved All 8 Billion People To Mars? - 動画で英語スピーキングを学ぶ

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War?

Environmental destruction?

Global warming?

Species extinction?

Spaceship Earth is being trashed by its crew.

It's looking like humanity.

It needs a plan B.

Fast.

And the obvious candidate?

Well, it's staring down at us every night.

Mars.

It has a total surface area almost equal to Earth's entire land area.

So there's room for all of us.

And unbelievably large sums of money are being directed to space exploration.

So it's not so out there to ask, what if we moved all 8 billion of us humans to Mars?

When you measure it, Earth is 71% ocean.

The livable area we live on is just a small part of the total.

So even though Mars is a planet with roughly half the diameter of Earth,

its livable surface area is strikingly similar to what we have on Earth.

So Mars has room for us.

Now, the most important element to sustain human life is water.

Wherever we move to, we're going to need lots of water.

And Mars may look like a dry rock, but unlike closer destinations like the Moon,

it secretly has water, and plenty of it.

Water on Mars exists as ice at the poles, or it's hidden in deep rock formations beneath the surface.

The scientists have estimated that there's enough subsurface water on Mars to cover the entire planet one to two kilometers deep.

Now, the next thing we'll need is air to breathe.

And Mars has air.

It's thin compared to Earth, but Mars has an atmosphere and weather systems to go along with it.

Currently, the air can't sustain human life without a space suit, but it is something to build on.

And given the choices of other close-by options, Mars is much better than the completely airless Moon,

or our closest neighborhood planet, Venus, where the atmosphere is mostly carbon dioxide and sulfuric acid.

It also has a surface temperature of a blistering 464 degrees Celsius.

That's 867 degrees Fahrenheit.

And an atmospheric pressure 93 times that of Earth.

So when you look at the hellscape that's Venus, Mars is pleasantly inviting.

And then there's light.

Wherever we go, we're going to need some sunlight.

Mars is only one and a half times the distance from the Sun as Earth is, so it's only a little farther away.

At that distance, Mars might seem like a cold environment compared to Earth, but it's close enough to the Sun to receive a useful amount of sunlight

that can be turned into solar power and to grow crops.

And Mars has seasons, like on Earth.

Mars' longer orbit means it takes longer to go around the Sun, so a Martian year is longer, at 687 Earth days.

But it has a similar rotation to Earth.

A day on Mars lasts 24.6 hours, compared to our 23.9.

Plus, it has a very similar axial tilt of 25 degrees, compared to Earth's 23.4 degrees.

And wherever we move to needs to be as close as possible.

There are closer destinations than Mars, like Venus or Mercury, but by any measure, they're completely unlivable.

So we're left with Mars as our closest habitable option.

Now, the Red Planet is the only logical next step after the Moon, which itself is an unimaginably harsh environment.

It's fit only as a launching pad to space.

The Moon is a great stepping stone to other places, maybe a small colony, but certainly not for 8 billion of us.

So Mars looks very promising.

And colonizing Mars isn't just wild speculation.

The race to Mars has already begun.

We're about to see one of the most technically ambitious and well-resourced space programs in human history shift into high gear.

The financial markets are already going there.

Just look at the valuation of SpaceX in 2026, which came in around $1.7 trillion.

Compare that with the operational budget of NASA's entire 13-year Apollo project in the 60s.

That cost around $300 billion, adjusted for inflation.

That shows that this is by far the most well-funded space project in human history, by a multiple of five.

This is getting real, real fast.

There's no question Earth is dying and Mars has space, Mars has water, Mars has an atmosphere and sunlight.

It's relatively nearby and we've already got remote rovers exploring it.

And one of the most valuable companies in the world is throwing all its capital and resources into getting there.

All that's left is to get all 8 billion of us off Earth and onto Mars.

So how many humans have we put into space so far?

10,000?

Maybe 1,000?

Nope, 781.

Not exactly an inspiring start.

SpaceX is leading the charge right now, constantly wrapping up its launch schedule.

But even with all that effort, the numbers are still tiny.

The SpaceX managed 96 launches in 2023, upping it to 134 launches in 2024,

and hit an all-time high of 165 launches in 2025, which was their busiest year ever.

But most of those launches have been without human passengers.

Of the 781 people who have left Earth and touched space, SpaceX has only lifted 78 of them.

Its Dragon spacecraft took six years and 20 different missions to get to that number, too.

That's the entire track record of the most active rocket company on Earth, set against our target of 8 billion people.

In the short human history of space travel, the single best year on record put about 70 people into space,

which was a record set by a combination of NASA and other countries during the peak of the space shuttle program.

And that was back in 1985.

Now, the record for the most people in space at the same time was set much more recently, in 2023.

And that record was tied again in 2024 when, drumroll please, Eleven people were on the International Space Station,

three on China's Tiangong Space Station, and six were aboard Virgin Galactic's VSS Unity space plane,

which spent only part of its hour-long flight in suborbital space.

So the record is 20 people, and it lasted less than an hour.

Humans establishing a permanent presence in orbit is an incredible achievement, and more are on their way,

but we're talking about evacuating Earth's entire population.

So how difficult is this really going to be?

SpaceX's most favorable projections for its Starship have a goal between 100 and 200 passengers per launch.

For argument's sake, let's be incredibly generous.

Elon loves to plan big and go even bigger, so let's give him the benefit of the doubt and multiply the high end of those numbers by 10.

So every launch would have 2,000 passengers.

Well, even at that accelerated rate, you'd need 4 million launches to move 8 billion people.

Okay, let's frame this from the perspective of a human lifespan,

not some abstract future, but as a project that someone born today has a chance of seeing reach completion.

At 4 million launches spread across a century of continuous non-stop launching,

that works out to about 110 launches of 2,000 person starships every single day for 100 years straight.

100

Put that beside the actual record, SpaceX's busiest year ever was about 165 launches.

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Moving everyone within a century means sustaining roughly 240 times that annual rate.

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Not for one record-setting year, but for every single year, 100 years straight.

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And there's a huge complication to this scenario.

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They can't launch every day.

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Because Mars and Earth are moving in relation to one another, they only line up for an efficient journey every 26 months.

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So launches can't be spread out.

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They need to be crammed into the 46 or so windows of opportunity that occurred during that 100-year period.

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Okay, well, that would be 87,777 launches during those precious windows and a standing fleet of ships ready to go,

109

numbering in the tens of thousands.

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Now, if we were to dial back this hypothetical fantasy

111

and use the number of ships that Elon Musk himself floated as an eventual goal of SpaceX,

112

a fleet of 1,000 ships carrying 100 passengers each, launching during the windows of opportunity,

113

well, the job would take 173,300 years.

114

we're definitely going to need a bigger lifeboat.

115

Let's take our number and multiply it by 100, a measure of scale that's way beyond our current thinking,

116

but also still inside the bubble of what's conceivably possible.

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Let's imagine that we can build ships that could carry 20,000 people per launch, a design that has no real engineering behind it.

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But to get a sense of this scale, think of the world's largest cruise ship, Royal Caribbean's icon of the seas.

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It's 365 meters long.

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That's 1,200 feet long, longer than three football fields.

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And it weighs 250,000 gross tons.

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Between the crew and the passengers, it holds about 10,000 people.

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So double that, stand it on end and shoot it into space.

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Even at this gargantuan size, we would need 400,000 launches to get everyone off Earth.

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That's 11 launches a day for a century.

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And again, you can't launch every day.

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Even carrying 20,000 passengers each trip, the size of the fleet would still need to be enormous.

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A quick trip to Mars, given current technology, would take 200 days one way, a 400 days round trip,

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with no time for turnaround.

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But the ship that went to Mars would have to wait there for a window of opportunity to return to Earth,

131

so they wouldn't get back in time for the next launch window 26 months later.

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We'd have to maintain a fleet double the amount.

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That's 17,390 ships to keep to this launch schedule.

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And here's the kicker.

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Even if we start with a static base figure of 8 billion people, that figure is going to rise daily.

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To make it simple, let's say we stick with the wildly optimistic figure of 11 launches of 20,000 people a day.

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So that's 220,000 people a day leaving Earth.

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But there are approximately 360,000 births a day on Earth and about 160,000 deaths for a daily population gain of around 200,000.

139

To get everyone off Earth and to safety, we'd have to launch a minimum of 10 ships with 20,000 people on them every day

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before we even started to evacuate any of the waiting 8 billion people alive today.

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And all this is without getting into the mind-numbing cost of lifting that much tonnage into space.

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The per kilogram cost of energy spent to send payloads into space is just the start.

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Humans need incredibly complex life support equipment, food and waste management systems.

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So unless we build a fleet of thousands of gigantic ships

145

and focus all of humanity's resources on this project for over a century, we won't be moving to Mars.

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Elon Musk's aspiration is for a 1 million person city on Mars within 20 to 30 years.

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Even if we ran the numbers for a fraction of Earth's population, say 8 million, and we went back to the most optimistic numbers floated by Elon,

148

we would be looking at between 40,000 and 80,000 launches.

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But the math we're dealing with is for 1,000 times that population.

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But let's say human engineering, labor, and resource allocation all rise to the occasion,

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and humanity pulls together and commits to this project for a century, and we move the human population of Earth to Mars.

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What happens next?

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How do we survive?

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Okay, the problem with Mars is that when you shine a critical light on it, and look past the surface comparisons,

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It has none of the basics we humans need to survive.

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If you think Earth's resources are stretched thin, well, let's take a look at a planet that has virtually nothing to offer.

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The water on Mars is trapped in ice, the air is almost non-existent,

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there's no food source, the dust that covers the planet is toxic, radiation levels are sky-high, and the sunlight is weak.

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When it gets down to the simple facts, Mars is going to try and kill you over and over and over again.

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All that subsurface water is buried so deep that it's almost impossible to get to.

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Drilling a hole 10 km deep on Earth would be an engineering feat in and of itself.

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The air is too thin to breathe, so you need to wear a space suit at all times when outside.

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Even if you could go outside without a suit, the fine toxic dust that covers every inch of the planet will poison you.

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And even then, the planet doesn't have a global magnetic field blocking out radiation like Earth does.

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So the radiation bathing you is 100 times Earth's natural background level.

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Without protection, it will slowly and inevitably destroy your cells.

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So you need to be shielded more or less permanently.

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Plus, this barren planet would starve you.

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This would be the equivalent of having 8 billion people live in a submarine.

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Permanently.

171

Never surfacing.

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Sound like fun?

173

Well, there's more.

174

Let's take a closer look at what kind of resources we'd need to survive on Mars.

175

There's a parallel right here on Earth on Earth, the harsh, unforgiving conditions in Antarctic research stations.

176

Nearly everything for human survival there is shipped in from outside.

177

780 kilograms of food per person per year needs to be imported for the crew.

178

The state-of-the-art experimental mobile greenhouse Eden ISS,

179

built to grow food for crews on space stations grew 268

180

kilos of food over about 286 days for a crew of 10, working out to about 27 kilos per person,

181

roughly 3.4% of the 780 kilos a person actually eats every year.

182

Almost all of these stations' operational energy needs to be imported too.

183

184

Locally generated wind power covers only about a fifth of the two stations' needs.

185

The South Pole station runs on a lean few hundred kilowatts of power on average to support up to 150 people,

186

but it still burns about 1.7 million liters of fuel a year.

187

scale up this Antarctic math for 8 billion people, and stretch the supply line across 54.6 million kilometers,

188

and the numbers start looking impossible.

189

Nothing grows naturally on Mars.

190

There's no viable soil, other than what Matt Damon might have left up there.

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And you can't just add water to the dust that's on the ground, it's dead.

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Every single calorie of food would have to be shipped in or grown in artificial greenhouses with imported soil.

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Feeding everyone on Mars at the Antarctic per person rate would require 6.24 trillion kilograms,

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or 6.24 billion tons of food every year.

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An amount that grown indoors at the best Eden ISS greenhouse yield ever achieved would need a sealed,

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artificially lit farm about the size of the United Kingdom.

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The power for lighting and heat alone for 8 billion people on Mars, even at bare research station rates per person,

198

comes out to roughly 9 times all the electricity humanity currently generates worldwide.

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On a planet that receives less than half of Earth's sunlight, is prone to planet-wide dust storms, and has no natural fuel reserves.

200

And building up an industrial base in the long term on Mars would have severe challenges.

201

The simple fundamentals like no hydrocarbons for plastics,

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and no coking coal for conventional steel would leave Mars lacking industrial basics.

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Due to a lack of critical resources,

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Mars would never be able to sustain some of the simple industrial chains that are essential to our modern technological world.

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Not to mention the very complex technological chains that drive Earth's current economy and tech industry.

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Semiconductor supply chains that only a handful of Earth's most advanced economies manage would be almost impossible on a planet like Mars.

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Mars would likely remain highly dependent on Earth for many of the survival-level basics for centuries, and maybe forever.

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And unlike colonies of the past on Earth, Mars wouldn't be a source of new wealth for the colonial home country,

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but an incredible resource drain.

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In the case of a dying Earth, the resources expended on the Mars project would only speed up our decline.

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The most radical fix would be to terraform the entire planet, transforming the dry, barren rock that is Mars into a fertile,

212

green water world like Earth.

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But this process, even if it was possible, would take unimaginable resources and hundreds,

214

if not thousands, of years to achieve.

215

But let's say we did it.

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Humanity pulled together all its resources and achieved the unachievable.

217

And we moved all eight billion of us to Mars and we solved the problems of water, radiation, dust, food, and energy supply.

218

Well, we still have a bigger problem.

219

The problem is us.

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Because who's to say that the same 8 billion people who trashed Earth wouldn't do the same thing on Mars?

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Humans have reshaped Earth.

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We now live in the Anthropocene, a new geological epoch defined by human activity on Earth.

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We've changed the composition of the atmosphere.

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Atmospheric carbon dioxide is now 50% higher than it was before the Industrial Revolution.

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The ocean has absorbed enough carbon dioxide to increase its acidity by 30%.

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44% of Earth's habitable land has been turned into agricultural land.

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Humans have wiped out 60% of the planet's mammals, birds, fish and reptiles since 1970.

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In the past decades, these human impacts have accelerated at an unprecedented rate.

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Sometimes referred to as the Great Acceleration, we're increasing carbon dioxide emissions,

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ramping up global warming, speeding up ocean acidification, destroying habitats faster, killing off more species,

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and doubling down on natural resource extraction.

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This is our track record.

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This is what 8 billion humans are capable of.

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And there's no indication that we wouldn't just do the same thing again on a new planet.

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Same population, but in an even more fragile situation.

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It's hard to imagine how humanity will act living in an almost entirely artificial closed-in world on Mars.

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But given the evidence, the citizens of Mars are likely to exploit, deplete, degrade their home in the same way they did on Earth.

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To add to this, the fact

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that every colony a country has ever established has eventually turned away from its colonizer and fought for independence.

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many times violently.

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Just like when the American colonies turned against Britain,

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the interests of the Mars colony would eventually drift out of alignment with whatever political entity was left on Earth.

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But in this case, even a resource depleted

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and environmentally degraded Earth would still look like a green paradise compared to the harsh, barren surface of Mars.

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Even a half-dead Earth probably recovering after the exodus of humans, would be a strong temptation to a struggling Mars colony.

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Which leads us to the real deal.

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Any problem that's big enough to make us seriously consider fleeing the planet

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is far cheaper to fix here than to restart from nothing on Mars.

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That's a summary of Neil deGrasse Tyson's point of view on the matter.

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Neil, who is the director of the Hayden Planetarium, aka someone who really, really knows space.

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The harsh fact is that there is no plan B.

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But if we understand this profound truth, we might just have a chance.

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If we turned the resources we're currently committing to financial fantasies toward the real world problems we face,

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we wouldn't have to leave Earth.

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Ironically, the global cooperation needed to plan and pull off mass immigration to Mars

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would be exactly the international coming together we'd need to move towards sustainability and to reverse Earth's decline.

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Fixing our problems here is far more realistic and achievable than escaping to space.

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But there is one external existential threat that we can't fix by ourselves here on Earth.

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It's happened before, and we probably won't be able to do anything about it.

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That's a direct hit by an asteroid that could render Earth completely uninhabitable.

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Even a small asteroid impact could scramble the global climate and send our complex and fragile civilization back to the Stone Age.

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We might be able to deflect or destroy an approaching asteroid threat if we had enough early warning,

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but there's also a chance we don't see it coming in time.

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This is not a fantasy situation.

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One of these asteroids has already ended an entire era of life.

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But when the Chicxulub asteroid smashed into Earth, it changed the climate overnight,

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wiped out the dinosaurs, and redirected the trajectory of evolution.

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But that's a story for another WHAT IF.

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このレッスンの語彙とスピーキングのポイント

このB2レベルのスピーキングレッスンは、動画「What If We Moved All 8 Billion People To Mars?」を教材にしています。繰り返し出てくる語は次のとおりです：Mars, Earth, space, planet, billion。この動画には、シャドーイング用の文が268文、単語が3358語あります。音声の長さは26:43です。話す速さは1分あたり約126語で安定しており、シャドーイングしやすいペースです。英語の頻出3,000語に含まれる単語は81%だけなので、語彙は難しめです。

この動画の重要語彙

動画の中で特に難しい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
sunlight 名詞	/ˈsʌnˌlaɪt/	日光, 太陽光
asteroid 名詞	/ˈæst(ə)ɹɔɪd/	小惑星
dioxide 名詞	/daɪˈɑksaɪd/	二酸化物
harsh 形容詞	/ˈhɑɹʃ/	粗悪
barren 形容詞	/ˈbæɹən/	不妊の
import 名詞	/ˈɪm.pɔɹt/	輸入品
kilogram 名詞	/ˈkɪləɡɹæm/	キログラム, キロ
multiply 動詞	/ˈmʌltɪplaɪ/	掛ける
accelerate 動詞	/ɪkˈsɛl.əˌɹeɪt/	加速する
greenhouse 名詞	/ˈɡɹːnˌ(h)aʊs/	温室, ハウス
fragile 形容詞	/ˈfɹæd͡ʒəl/	壊れやすい, 脆い
optimistic 形容詞	/ˌɒptɪˈmɪstɪk/	楽観的
float 動詞	/fləʊt/	浮かぶ, 浮く
wipe 動詞	/waɪp/	拭く
orbit 名詞	/ˈɔɹ.bɪt/	軌道

動画に出てくる句動詞

単語	発音	意味
speed up 動詞	/spiːdˈʌp/	スピードを出す
wipe out 動詞		一掃する

繰り返し練習したい文

動画に出てくる短く完結した文です。日常会話でそのまま使えます。

Wherever we go, we're going to need some sunlight.
For argument's sake, let's be incredibly generous.
We'd have to maintain a fleet double the amount.
How do we survive?
We've changed the composition of the atmosphere.

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している	have estimated · has already begun · have been
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	being trashed · being directed · can be turned
関係詞節 who / which + 節 — 人や物について情報を加える	people who have · people who trashed · someone who really

注意したい発音

話し手はwe're, can't, wouldn'tなど、短縮形や弱形を34回使っています。聞こえたとおりの短い形で発音しましょう。

「sh」と「zh」の音: harsh /ˈhɑɹʃ/, emission /ɪˈmɪʃ.ən/, shuttle /ˈʃʌtəl/, ambitious /æmˈbɪʃ.əs/, fraction /ˈfɹæk.ʃən/
長い単語（アクセントの位置に注意）: habitable /ˈhæbɪtəbəl/, accelerate /ɪkˈsɛl.əˌɹeɪt/, atmospheric /ˌætməsˈfɛɹɪk/, optimistic /ˌɒptɪˈmɪstɪk/, technological /ˌtɛk.nəˈlɑ.dʒɪ.kəl/

日本語話者が苦手な音：

/r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: kilogram /ˈkɪləɡɹæm/, accelerate /ɪkˈsɛl.əˌɹeɪt/, fragile /ˈfɹæd͡ʒəl/, favourable /ˈfeɪv(ə)ɹəbəl/, secretly /ˈsiː.kɹɪt.li/
/v/ — /b/ にならないように、上の歯を下唇に当てる: favourable /ˈfeɪv(ə)ɹəbəl/, inevitably /ɪˈnɛvɪtəbli/, viable /ˈvaɪəbəl/, civilization /ˌsɪv.ɪ.laɪˈzeɪ.ʃən/, overnight /əʊvə(ɹ)ˈnaɪt/
/f/ — 「フ」ではなく、上の歯と下唇で出す: atmospheric /ˌætməsˈfɛɹɪk/, fragile /ˈfɹæd͡ʒəl/, float /fləʊt/, favourable /ˈfeɪv(ə)ɹəbəl/, drift /dɹɪft/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
通常の速度で一文ずつシャドーイングし、話し手のリズムに合うまで繰り返します。
自分の声を録音して元の音声と比べます。sunlight, asteroid, dioxideなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: What If We Moved All 8 Billion People To Mars? - 動画で英語スピーキングを学ぶ

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What Happened After the DEADLIEST Asteroid Hit Earth?

What If We Had To Rebuild Human Society From Scratch?

Unit 6: Living on Mars

5 "Impossible" Things That Can Happen On Other Planets

What If You Lived on Mars 1 Billion Years Ago?

Can Earth Run Out of Water?

The Planets In Our Solar System

Sometimes size does matter #stem #map #perception

What Would Happen If Earth Started to Spin Backwards

YOU Own the Moon. And Mars. And Venus.

What If The World Went Vegetarian?

Spending a Day on Earth 200 Million Years Ago

Artemis II Astronaut talks about being a Crew ✨🌎 #nasa #space #artemis