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What Would Happen If The Sun Disappeared For One Week? — Transcript

by The Last Day · 3,049 words · 550 segments · language en · Watch on YouTube

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0:00S S for sun.
0:02>> S for sun.
0:03>> Very good. And [music] the sun gives us
0:04light. It gives us everything.
0:06Oh, I've got you. I've got you. Hold on
0:08to me.
0:09>> Mama, what is it?
0:11>> Don't look at it.
0:12>> Mama, the sun.
0:15>> Right now, the sun is shining on you.
0:18Or at least, it was 8 minutes [music]
0:20ago.
0:21That is how long sunlight takes to cross
0:24the 93 million miles between the sun and
0:27the earth.
0:298 minutes and 20 [music] seconds.
0:32So, the light hitting your window at
0:33this moment left the sun's surface
0:36before you started watching [music] this
0:38video.
0:39Which means something strange and rather
0:42unsettling.
0:44If the sun vanished right now,
0:46completely and instantly,
0:48>> [music]
0:48>> you would have no idea.
0:51For 8 minutes, the sky would stay blue.
0:54Shadows would fall exactly where they
0:57always do.
0:58Birds would keep singing. Satellites
1:01would keep tracking a star that no
1:03longer exists.
1:05Every plant on earth would keep
1:08photosynthesizing [music]
1:09using light from a sun that disappeared
1:12before the sentence [music] began.
1:14And then, at 8 minutes and 20 seconds,
1:18the sky would go out.
1:20Not dim, not fade,
1:23out.
1:24So, let's run the scenario properly.
1:27The sun disappears [music] completely
1:29for exactly 7 days, then returns
1:32unchanged, exactly [music] as it was.
1:36How cold does it get?
1:38What dies first? Does anything [music]
1:41survive?
1:42And does the earth even stay where it
1:44is?
1:45Let's find out.
1:47Before anything happens, we need to be
1:50clear about the rules.
1:52The sun does two things for earth.
1:55It provides light and heat, [music] and
1:58it provides gravity.
2:00Its gravitational pull is what holds our
2:03planet in [music] orbit, and both of
2:05those things travel at the same speed.
2:08The speed of light.
2:10This is one of the [music] most
2:11important results in physics.
2:14Gravity is not instantaneous.
2:17When Einstein published general [music]
2:19relativity, one of its predictions was
2:22that changes in gravity propagate
2:24[music] outward at exactly the speed of
2:26light, no faster.
2:29That prediction was confirmed [music] in
2:312015, when detectors on Earth measured
2:34gravitational [music] waves from two
2:36black holes colliding over a billion
2:39light-years away, arriving precisely as
2:42the theory said they should.
2:45So, in our scenario, the light and the
2:47gravity [music] disappear together. And
2:50they both stop reaching us after the
2:52same delay.
2:548 minutes and 20 seconds [music] of a
2:56completely normal afternoon.
2:59Then, everything changes at once.
3:03At 8 minutes and 20 seconds, [music]
3:05the last photons from the Sun arrive at
3:08Earth.
3:09And then, nothing.
3:11For anyone standing [music] on the
3:13daylight side of the planet, the
3:15experience would be instant and total.
3:19The sky does [music] not darken
3:20gradually because there is no light left
3:23to scatter.
3:25The blue sky you see is sunlight
3:27bouncing off air molecules.
3:29Remove the source, and the sky simply
3:32stops [music] existing as a bright
3:34thing.
3:36Daylight becomes night in less than a
3:38second.
3:39But here is the detail almost nobody
3:42expects. [music]
3:44It would not be properly dark.
3:47Because the stars are still there.
3:50Without the Sun washing out the sky, you
3:53would see the full night sky in the
3:55middle of the afternoon. And it would be
3:57the clearest, most brilliant sky any
4:00human has ever seen outside [music] a
4:03desert at new moon.
4:05You would also see the planets still
4:07shining. Venus, Jupiter, Mars, all of
4:12them still lit.
4:14For about 8 minutes, because sunlight
4:16[music] takes different amounts of time
4:18to reach each of them, and then to
4:20bounce back to us.
4:22So, the planets would go out one by one
4:25in order of their distance, like someone
4:28walking down a corridor switching off
4:30lamps.
4:32The moon would be the first to go within
4:34a second or two.
4:36Venus a few minutes later, then Mars,
4:39then Jupiter half an hour or more after
4:42the sun vanished.
4:44Imagine standing outside and watching
4:46the planets extinguish one at a time in
4:50a sky full of stars.
4:52It would be the most beautiful thing any
4:55human being will ever see.
4:58Now, the other half of the problem. The
5:01sun's [music] gravity is gone, too.
5:04And at that same instant, Earth stops
5:07orbiting.
5:08Here is [music] what people usually get
5:10wrong. The Earth does not fall toward
5:13where the sun used to be, and it does
5:16not fly away at random.
5:18It simply obeys Newton's first law.
5:22An object in motion stays in motion
5:25unless a force acts on it.
5:28The force is [music] gone.
5:30So, the Earth travels in a perfectly
5:32straight line in whatever direction it
5:35happened to [music] be moving at that
5:37moment at the speed it was already
5:39going.
5:41That speed is about 30 [music] km/s,
5:44roughly 107,000
5:46km/h.
5:49We would be flying off at a tangent
5:51[music]
5:51straight out of the solar system.
5:54But over the course of 1 week, [music]
5:56how far is that?
5:58About 18 million kilometers.
6:01Which sounds enormous, but in solar
6:04system [music] terms, it is nothing.
6:06It is around 12% of the distance to the
6:09sun.
6:10Not far enough to matter [music] for
6:12temperature because the sun is gone
6:15anyway.
6:16So, after 7 days, we are 18 million
6:20kilometers off course, moving in a
6:22straight line through empty space, and
6:25we would need the sun to come back in
6:27exactly the right [music] place to
6:29resume our orbit. In our scenario, it
6:32does, but hold that thought because it
6:35becomes important later.
6:37Meanwhile, on the surface, nobody is
6:39thinking about orbital mechanics. They
6:42are thinking about the temperature. This
6:44is the question everyone asks, and the
6:46answer is more [music] interesting than
6:48you might expect because the cooling is
6:50not steady at all. Earth's surface stays
6:54warm in two ways. It absorbs sunlight,
6:57and it is wrapped in an atmosphere and
6:59oceans that store enormous [music]
7:02amounts of heat. Remove the sunlight and
7:04the planet starts radiating its stored
7:07heat [music] into space without anything
7:09replacing it.
7:10Within the first 24 hours, average
7:13global surface temperature would drop by
7:15roughly [music] 18° C.
7:19That is a dramatic fall,
7:22>> [music]
7:22>> but it is survivable almost everywhere.
7:25A warm summer day [music] becomes a cold
7:27winter day.
7:29And here is where the cooling slows
7:31down. As the surface gets colder, it
7:34radiates heat more slowly. The rate of
7:37heat loss depends very strongly [music]
7:38on temperature, so the colder Earth
7:41becomes, the longer it takes to lose the
7:43next degree. [music]
7:45So, the first day is brutal. The second
7:48day is worse. But, after that, the curve
7:50starts to flatten. Estimates [music]
7:53suggest that within a week, average
7:55surface temperatures would fall to
7:57somewhere around -40°C.
8:00[music]
8:01Within a year, somewhere around -70.
8:05So, let's be precise about our scenario.
8:087 days without the sun
8:09>> [music]
8:10>> does not freeze the Earth solid. It does
8:12not boil off the atmosphere [music] or
8:15turn the oceans to ice. What it does is
8:18deliver the most severe [music] and
8:20sudden winter in the history of the
8:22planet. And that is more than enough.
8:25In the first hours, the most dangerous
8:28thing is not the cold. It is the
8:30darkness
8:31>> [music]
8:31>> arriving instantly across half the
8:33world. Every aircraft in flight on the
8:36daylight side loses visual reference
8:39without warning.
8:40>> [music]
8:41>> Every road suddenly has no light. Power
8:44grids face an immediate and catastrophic
8:46problem because solar generation
8:49vanishes worldwide in the same [music]
8:51second. And demand for heating and
8:53lighting spikes at once. Grids are
8:56balancing acts. A sudden massive
8:59imbalance triggers protective [music]
9:01shutdowns, and those cascade. Large
9:04portions of the world lose power within
9:07hours. Meanwhile, [music]
9:09the temperature is dropping by roughly a
9:11degree every 80 minutes. By the end of
9:14the first day, surviving in most of the
9:16world means having heat that does not
9:18[music] depend on the grid. Gas, wood,
9:22oil, anything that burns. And something
9:25else is happening quietly that will
9:27matter enormously later. Photosynthesis
9:31has stopped. Every plant on Earth, every
9:34tree, every crop, every blade of grass,
9:38and critically, every microscopic plant
9:40[music] in the ocean has stopped
9:42converting light into energy.
9:45The entire food [music] chain of this
9:46planet has been unplugged at the source.
9:50Plants do not die [music] immediately.
9:52Most can survive days of darkness using
9:55stored energy. A week of [music]
9:57darkness alone would not kill a mature
9:59tree.
10:01But the cold is a different matter.
10:03By the second day, average temperatures
10:05[music]
10:05are approaching minus 20.
10:08Something is now happening to the
10:10weather that is genuinely strange. Our
10:13atmosphere moves because of uneven
10:15heating. The equator receives more
10:18energy than the poles. Warm air rises,
10:21cold air sinks, [music] and the whole
10:23system churns. Every wind, every storm,
10:28every weather system on this planet is
10:30ultimately driven by sunlight. With the
10:33sun gone, that engine switches off. The
10:37existing weather does not stop instantly
10:39because the atmosphere still holds
10:41momentum, and the oceans still hold
10:44heat. But the temperature difference
10:46that drives it begins to collapse,
10:49>> [music]
10:49>> and the global circulation starts
10:51winding down. In many places, [music]
10:54the wind simply dies.
10:56Alongside that, something else begins.
11:00The oceans are [music] now far warmer
11:02than the air above them, and that
11:04difference drives enormous evaporation
11:06and condensation.
11:08Heavy snowfall would develop over
11:10coastal regions and [music] across the
11:12seas as warm ocean moisture meets
11:15freezing air.
11:17Here is where we need to be honest about
11:20casualties, [music]
11:21and the order may surprise you.
11:24The first things to go [music] in large
11:26numbers are the smallest. Phytoplankton,
11:29the microscopic photosynthetic life in
11:31the ocean surface waters are responsible
11:34for a huge proportion of the planet's
11:36oxygen production and sit at the base of
11:39the marine food web.
11:41Many have very short lifespans measured
11:44[music] in days.
11:46A week without light causes a severe
11:48collapse in their numbers.
11:50On land, most plants survive a week of
11:53darkness, but not necessarily a week of
11:55[music] extreme cold.
11:57Tropical plants, which have no
11:59adaptation to frost at all, would be
12:01devastated. Crops in the field would
12:04[music] be lost worldwide.
12:06Temperate and polar plants, already
12:09built for winter,
12:10>> [music]
12:10>> would mostly survive.
12:12Insects, being small and cold-blooded,
12:15would suffer enormously outside of
12:17shelter.
12:18Large mammals, including humans, are in
12:21a strange position.
12:23We can survive minus 40 as long as we
12:26[music] have insulation and heat. Our
12:28problem is not biology. It is
12:31infrastructure.
12:33And here is the point worth dwelling on.
12:36Where you are matters far more than what
12:39you are.
12:40If you are in the deep ocean, nothing
12:42happens.
12:43The abyss [music] is permanently dark
12:45and close to freezing already.
12:48Life down there, much of which depends
12:50on chemical energy from hydrothermal
12:52vents rather than sunlight,
12:54>> [music]
12:54>> would not register the event at all.
12:57If you are in a cave system, [music] in
12:59deep soil, or in a hot spring, you would
13:02likely be fine.
13:04If you are a microbe several kilometers
13:06underground, drawing energy from rock
13:08chemistry, the sun disappearing is not
13:11an event in your life.
13:13Those organisms would never know.
13:16>> [music]
13:16>> The deeper and darker your home, the
13:19safer you are.
13:20By day four, average [music]
13:22temperatures are falling toward minus
13:2430.
13:25The oceans are now doing something
13:26[music] important, and it is the reason
13:29the Earth does not simply freeze.
13:32Water has an extraordinarily high heat
13:34capacity. It takes an enormous amount of
13:37energy to change its temperature, which
13:40means it also releases that energy
13:42slowly.
13:43The oceans hold a vast reservoir of heat
13:46accumulated over a very long time, and
13:49they do not give it up quickly.
13:51Sea ice begins forming far outside its
13:54usual range, spreading across the
13:56surface [music] of seas that have never
13:58frozen.
13:59But that ice then acts as insulation,
14:02slowing further heat loss from the water
14:04below.
14:05So, beneath the ice, the ocean stays
14:08liquid and [music] relatively warm.
14:10Life in the water column continues, for
14:13now.
14:14On land, by day [music] six and seven,
14:17we are approaching minus 40 on average,
14:20far colder in continental interiors.
14:23>> [music]
14:23>> This is comparable to an Antarctic
14:25winter, except it is everywhere at once.
14:29Anyone still alive is alive because they
14:32have fuel, shelter, and [music] food
14:34stored indoors, and because they stopped
14:36relying on anything that requires
14:38electricity days ago.
14:41The night sky is still spectacular.
14:42[music]
14:44That has not changed.
14:46Seven days of the clearest stars ever
14:48seen from the surface of this planet,
14:51over a world that is slowly freezing
14:53beneath them.
14:55On day seven, the sun comes back, and it
14:58does not announce itself.
15:00For 8 minutes [music] and 20 seconds,
15:03nothing happens, because the light is
15:05still in [music] transit.
15:07The world remains dark and frozen, while
15:1093 million kilometers away, a star is
15:13already shining.
15:15Then dawn arrives everywhere at once, in
15:18the middle of whatever hour it happens
15:20to be, [music]
15:21with no warning and no horizon glow.
15:25The sky simply switches back on.
15:28It would be the single most emotional
15:29moment in human history.
15:32But the return is not gentle. [music]
15:35The planet is now covered in fresh snow
15:37and ice over an enormous area.
15:40And ice reflects sunlight rather [music]
15:42than absorbing it.
15:44This is called albedo.
15:46A bright planet absorbs less energy than
15:48a dark one. Which means the newly frozen
15:51Earth would warm back up more slowly
15:53than it cooled.
15:55At the same time, the atmosphere that
15:57had wound down is suddenly given energy
16:00again. And the temperature differences
16:02driving circulation are now extreme and
16:05chaotic.
16:07The restart would bring violent storms
16:09worldwide. Recovery to normal global
16:12temperatures would take weeks to months,
16:15not days.
16:16And the ecological damage would last
16:18[music] far longer.
16:20A collapsed plankton population takes
16:23time to rebuild. A lost global harvest
16:26means [music] a food crisis that
16:28outlives the event by a year or more.
16:31The week [music] of darkness ends. The
16:34consequences do not.
16:36Now the detail that makes this [music]
16:38scenario genuinely strange, and it has
16:41nothing to do with temperature.
16:45>> [music]
16:48>> When the sun reappears, its gravity has
16:50to travel to us as well, taking another
16:538 minutes to arrive.
16:55And when it does, Earth is in the wrong
16:57place, moving in the wrong direction.
17:01We would not simply resume our old
17:03orbit. We would fall into a new one, an
17:07[music] ellipse shaped by our position
17:09and velocity at that moment.
17:12Depending on the direction we happen
17:13[music] to be traveling when the sun
17:15vanished, that new orbit could bring us
17:17closer to the Sun at some points and
17:19further away at others.
17:22In other words, a week without the Sun
17:24>> [music]
17:24>> would permanently change the shape of
17:26our year.
17:28The seasons would be different. The
17:30length of the year would be different.
17:33Not catastrophically, perhaps, but
17:35measurably and forever.
17:38And we would not be alone. Every planet,
17:41every moon, every asteroid in the solar
17:45system would have done the same thing.
17:47Each flying off on its own tangent for a
17:50week before being recaptured into a new
17:53orbit.
17:54The entire solar system would be
17:56reshuffled and the long-term [music]
17:58stability of those new orbits would be
18:00an open question.
18:02The Sun returning would not restore the
18:04solar system. It would create a new one.
18:08No.
18:08>> [music]
18:09>> And the reason is worth explaining.
18:11Mass cannot simply vanish.
18:14Conservation of energy is one of the
18:16most thoroughly tested principles in all
18:18of physics and nothing in the known
18:21universe allows an object of 2 billion
18:24billion billion tons to stop existing.
18:28The Sun also cannot switch off. It
18:31shines because of nuclear fusion in its
18:33core, converting hydrogen into helium
18:36and releasing energy. And that process
18:39is self-regulating and remarkably
18:41stable.
18:42It has been running for around 4 and 1/2
18:45billion years and has roughly 5 billion
18:48left. And even if fusion somehow stopped
18:51today, the Sun [music] would not go
18:53dark.
18:55The energy generated in its core takes
18:57an extraordinarily long time to work its
19:00way to the surface [music]
19:01with estimates ranging from thousands to
19:04hundreds of thousands of years.
19:07The Sun would keep shining for a very
19:09long time on energy [music] already in
19:12transit.
19:13There is also no plausible way to remove
19:16its gravity. Gravity is produced by
19:18mass, and the mass is not going
19:21anywhere.
19:22So, the sun disappearing is not a risk.
19:25It is a thought experiment, and a useful
19:28one, because it reveals how much of our
19:30world is quietly held up by something 93
19:33million kilometers away.
19:36Here is what I find remarkable about
19:38this scenario. We tend to think of the
19:41sun as something that lights our days, a
19:44thing that rises and sets and makes the
19:46[music] weather pleasant.
19:48It is not. It is the engine that runs
19:51this entire planet.
19:54Every wind that has ever blown was
19:56driven by solar heating. Every ocean
19:59current, every storm, every rain shower,
20:03every plant, every animal, and every
20:06human being on Earth runs on energy that
20:09originated in that star.
20:12The food you ate today was sunlight a
20:14few months ago. The fuel in a car was
20:17sunlight that fell on this planet
20:19hundreds of millions of years ago.
20:22Take it away for 1 week,
20:24>> [music]
20:24>> and the planet does not explode or
20:26shatter. It simply stops.
20:29The wind drops, [music]
20:30the temperature falls, the food chain
20:33unplugs at the base, and the Earth
20:35drifts off in a straight line through
20:38the dark.
20:39And the most unsettling part is the
20:41[music] 8-minutes.
20:43The gap between the sun ending and us
20:46finding out, a window in which
20:48everything is already over and nothing
20:51has happened yet.
20:53>> [music]
20:53>> So, the next time you step outside and
20:55feel the warmth on your face, remember
20:57that it is 8-minutes old, that it
21:00traveled 93 million miles to reach you,
21:03and that it is doing far more than
21:06keeping you warm.
21:07It is holding the entire system
21:09together.
21:11Thanks for watching. If you enjoyed
21:14this, subscribe [music]
21:15and let us know in the comments which
21:17impossible scenario we should explore
21:19next.

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