What Happens if the Moon Crashes into Earth?
Summary
TLDRこのビデオスクリプトでは、月が地球に衝突するという想像上のシナリオを科学的に分析しています。月がなぜ地球に向かって落ちてこないのか、そして実際に衝突した場合の地球への影響について、海の潮、地震、火山活動、さらには地球全体の気温変化までを詳述しています。最終的には、月が地球の大気圏内側に入って破砕され、地球の周りにリングを形成するという壮大な結末を想像しています。
Takeaways
- 🌕 地球の重力が月を引き寄せるが、月は軌道運動で地球に向かって落ちてこない。
- 💨 月が地球を27日間で3600km/hの速さで横方向に廻っているため、軌道を保っている。
- 🔄 月が地球に向かって落ちてくるためには、その軌道速度を変える必要があり、そのためには膨大な力が必要。
- 🌊 月が地球に近づくにつれて、潮汐が高くなる。最初はわずか数センチから始まり、月が地球に半分近づいた時には4メートルに達する。
- 🌐 月が地球に近づくことで、通信やナビゲーション衛星の軌道が乱れ、衛星が制御不能になる。
- 🏙️ 2ヶ月目に地球のインフラが崩壊し、海に近い1億人以上の人々が流離失所となる。
- 🌋 月が地球に近づくことで、地震や噴火が増加し、大気中の火山灰が地球の気温を下げる。
- 🌌 6ヶ月目に地球は半分が水没し、半分は水が海に戻る。月が地球に24時間で1周し、天頂に固定される。
- 🌗 月が地球から75,000km以内に近づくと、月が変形し始め、月顫えが発生する。
- 💥 1年の終わりに月はローシュ限界に達し、地球の重力により月は崩壊し、地球周りにリングシステムが形成される。
- 🌈 月が崩壊することで、地球の苦しみは終わる。しかし、その後の状況は不透明で、大気の熱化や急速な冷却が起こる可能性がある。
Q & A
地球が月を引き寄せる重力がなぜ月が地球に向かって落ちてこないのですか?
-月は地球を周りに「軌道」を描いているためです。これは「横方向」の動きで、地球への引き寄せ力に反対する力はありませんが、その速度と軌道の傾斜角が月を地球に向かって落ちないように保っています。
月が地球を回るスピードはどれくらいですか?
-月は地球を27日間で一周し、時速約3600kmで地球を軌道しています。
月が地球に向かって落下するにはどうすればよいですか?
-月の軌道を変更するには、その速度を変える必要があります。しかし、小さな変化にも膨大な力が必要です。
月が地球に近づくことで最初に変化するのは何ですか?
-月が地球に近づくと、月がわずかに明るくなり、潮位がわずかに変化し始めます。
月が地球に近づくにつれて潮位はどのように変化しますか?
-月が近づくにつれて、潮位は徐々に高くなり、月が地球から半分の距離になった時には4メートルに達します。
月が地球に近づくことで地球のインフラにどのような影響が及ぶのですか?
-月が近づくことで、潮位が10メートルを超えると、世界中のインフラが崩壊し、港が使えなくなり、通信網が混乱します。
月が地球に近づくことで通信衛星にどのような影響が及ぶのですか?
-月が近づくと、通信衛星の軌道が歪み、燃料がなくなると衛星は制御不能になります。
月が地球に近づくことで地震や火山活動はどのように変化しますか?
-月が近づくことで、地球のマグマ庫が圧迫され、大きな地震や火山活動が引き起こされます。
月が地球に近づくことで地球の気温はどのように変化しますか?
-火山活動により大量の火山灰が大気圏に上昇し、日射を反射させ、地球全体が急速に冷え込んでいきます。
月が地球に接触する直前に地球の状況はどうなりますか?
-月が地球に接触する直前に、地球は半分が水没し、半分は水が海に戻され、地球全体が最悪の出来事に備えているかのように見えます。
月が地球に接触する際のローシュ限界とは何ですか?
-ローシュ限界とは、地球の重力が月の重力を上回るポイントで、月の表面の物体が地球に向かって落下し始め、最終的に月が崩壊する地点を指します。
月が地球に接触した後、地球の状況はどうなるのですか?
-月が崩壊し、地球に大きな輪状システムを形成します。その後、地球の状況は月塵の雨や大気圏の反応によって変わり、海が沸騰したり、地球表面が凍結するような過冷却期が始まる可能性があります。
Outlines
🌕 月が地球に落ちる可能性とその影響
この段落では、月がなぜ地球に落ちていないのか、そしてもし月が地球に落ちる場合の過程と影響について説明しています。月は地球の重力に引き寄せられながらも、水平方向の速度を保ちながら軌道を描いており、そのため落ちてきません。しかし、もし月の軌道速度を変える大きな力を加えると、月は地球に向かって螺旋状に近づいてくるでしょう。その過程で、月の接近により引き起こされる潮の高さの変化や地震、火山活動などの地球環境への影響が徐々に増していきます。
🌊 月の接近による地球の天変地異
この段落では、月の接近が地球の潮汐に与える影響が中心です。月の近づきにより、潮汐の高さが徐々に増大し、最終的には地球上の多くの地域が水没するでしょう。また、月の重力が引き起こす地震や火山活動も増加し、地球の環境は極端な変化を遂げます。さらに、月の近づきが進むにつれて、通信や衛星の軌道も影響を受け、人間の生活インフラに大きな影響を及ぼすことが予想されます。
🌗 月の崩壊と地球への最終的な影響
最後の段落では、月が地球に到達する直前に起こる出来事と、その後の地球の状態について語られています。月が地球のローシュ限界に達すると、自らが崩壊し、地球周りにリングシステムを形成するでしょう。その結果、地球上の酷い状況は一時停止しますが、その後の地球環境は依然として不透明です。月の塵が大気中に降り注ぐことで、大気を加热し海洋を沸騰させる可能性も考えられます。しかし、それでも生き残った人々は、再び文明を築き上げる試みを始め、美しいリングが空に輝く中での新たな生活を目指すことでしょう。
Mindmap
Keywords
💡重力
💡軌道
💡速度
💡満潮
💡羅氏限界
💡地震
💡火山
💡地球温暖化
💡地球
💡月
Highlights
The moon doesn't crash into Earth due to its sideways orbiting motion at high speed, counteracting Earth's gravity.
Orbits occur when an object like a thrown ball moves fast enough to continuously fall around Earth without hitting the ground.
To crash the moon into Earth, its orbit would need to be altered by changing its speed, requiring enormous forces.
The moon's mass is so large that even billions of rocket engines would barely move it.
A hypothetical scenario involves using a 'magic spell' to slow the moon, causing it to spiral towards Earth over a year.
As the moon gets closer, the tides on Earth increase due to the stronger gravitational pull, initially by half a meter.
Tides are caused by the gravitational interaction between the Earth and the moon, with different parts of Earth experiencing varying pulls.
Within a month, the moon's closer approach raises ocean tides to 4 meters, flooding coastal cities daily.
By the end of month 2, tides exceed 10 meters, displacing a billion coastal residents and disrupting global infrastructure.
Communications and shipping are severely impacted as ports become inoperable and internet cables fail.
Tidal bores cause rivers to reverse flow, contaminating freshwater with saltwater and leading to gas shortages.
As the moon approaches, it disrupts satellite orbits, causing navigation and communication issues.
Tides grow to 30 meters and then 100 meters, exposing continental shelves and causing massive flooding.
The moon's gravitational squeeze on Earth triggers earthquakes and volcanic eruptions, altering the climate.
At 75,000 km from Earth, the moon illuminates the night sky like twilight, with daily phase cycles.
Approaching the Roche limit, the moon disintegrates into a ring system around Earth, ending the apocalyptic events.
The moon's disintegration leads to a cessation of the extreme tides and weather events, though challenges remain.
Survivors may emerge to rebuild civilization under a sky illuminated by the moon's ring, facing an uncertain future.
Transcripts
Today we are answering an age-old very scientific and important question:
What if the moon crashes into earth? It’s more interesting and weird than you probably think.
Let's start with the basics: Why isn't the Moon on its way to crash into us already?
We know that earth’s gravity pulls everything towards it, including the Moon, but somehow,
it stays up, as if suspended by some opposite force. But there is no other force countering
gravity - instead, the trick to staying up is a ‘sideways’ motion that we call an orbit.
You see orbits every day: when you throw a ball it makes a tiny little orbit.
The only difference between that ball’s orbit and the moon’s is that the ball
eventually hits the ground. Basically, the reason is speed.
If you could throw your ball fast enough, it would bend around the world and come back to you.
If there was no air slowing it down, it could orbit forever. And this is what the moon does:
Falling sideways around earth, very fast, with no air slowing it down. Orbiting earth every 27 days,
at 3600 km/h. So for the moon to just stop in its orbit and plummet to the earth would
break more laws of physics than we have time to explain. So how do we crash it into earth?
In a nutshell, to change an object’s orbit, you need to change its speed,
which changes where gravity takes it. But even small changes require enormous forces,
which is why all the large objects in the solar system are so stable nowadays.
According to science, the moon is big and very massive. Even igniting billions of rocket engines
all over its surface would barely move the Moon. It looks like nothing short of magic will make
the moon fall. So we’ll use a magic spell that slows down the moon so much
that it changes its orbit and spirals towards earth. To get the most from the experience,
the moon will take exactly one year before it hits earth. Ready? 3. 2. 1. *Magic
Month 1
For the first few days, nothing really changes. The moon gets a tiny bit brighter
and scientists get confused, but the rest of us don’t notice anything different.
The only noticeable real effect of the moon on the earth are the tides.
Tides exist because while earth pulls on the moon, the moon’s gravity pulls back on the earth.
Since the strength of gravity gets weaker with distance, different parts of the earth
feel a slightly different pull. Which causes the earth, especially the oceans,
to bulge when the moon is above them, and contract a little on the sides when it’s
not. As earth rotates every day underneath the moon, the moon’s influence fluctuates,
causing the water-level of the oceans to rise and fall by about half a meter twice a day.
But with the moon drawing ever closer, high tide gets higher every day. At first barely noticeable,
within a month the moon has covered half the distance to the earth and ocean tides have
grown to 4 meters. Everyday high tide comes and waves flood coastal cities.
And there is no end in sight. With the moon drawing ever closer, tides rise ever higher,
inundating another city and more inhabited land with salty water every day.
Month 2
By the end of month 2 the moon has covered two-thirds of the distance to earth,
and global infrastructure is crumbling as tides rise above ten meters – displacing up
to a billion people who happen to live near the coastlines.
As ports become inoperable shipping grinds to a halt. Not only will it slow down the
delivery of Kurzgesagt products but also less exciting things like food.
Global communications fall into disarray – 95% of the internet is carried by ocean-crossing cables,
and while these largely don’t mind the water, their terminals on land do. Living inland
doesn’t guarantee safety either, tidal bores cause rivers to flow backwards,
carrying saltwater to contaminate surface and groundwater supplies.
Gas shortages follow, as oil refineries near the coast are abandoned. Countries are left
with the supplies they had on their shelves and strict rationing will begin. In the cities,
chaos reigns during the scavenging hours of low tide,
while survivors take refuge in highrises when the water returns.
Month 3
Three months in and the moon is close enough to disrupt communication
and navigation satellites. While it is normally far too distant for its gravity to cause any
major problems for our satellites, the closer it gets the more warped their orbits become.
As their fuel for orbital corrections runs out, satellites careen out of control.
Month 4 - 5 On earth, the tides are
rapidly growing to about 30 meters and will be reaching 100 m in height in a few short weeks.
At low tide, the ocean recedes hundreds of kilometers, exposing the continental shelf
like vast deserts, while at high tide walls of water drown agriculture, houses and skyscrapers.
And now, almost five months in, the apocalypse has finished its warm-up act.
Since the oceans are on average only 3 kilometers deep, the tides have reached their maximum. Up
until now, the water in the oceans could flow, absorbing most of the moon's gravitational
squeezing, but now the earth itself is really feeling the squeeze of the ever approaching moon.
These aren’t so much tides of ‘water’, but tides of ‘rock.’ The squeezing of the planet,
combined with the weight of quintillions of tons of water sloshing on and off the tectonic plates,
creates enormous stresses below and begins to cause earthquakes of increasing magnitude and
intensity. It’s impossible to say how serious these earthquakes might be or where they occur,
but like a child jumping on their bed until it breaks, no good can come of it.
Strong tidal forces lead to volcanism on other planets and moons. On earth,
squeezing the planet disrupts the magma reservoirs inside the crust,
triggering sizable, climate-altering eruptions in Chile, New Zealand, Yellowstone, and elsewhere.
Meanwhile, watching patiently above is the moon. Still no bigger in the sky than a small cloud.
Within 75,000 km of earth, it is bright enough to illuminate the night sky like twilight.
Month 6 - 7
After half a year, the moon is entering the space once occupied by geosynchronous satellites where
it orbits earth every 24 hours. It appears to float at one spot in the sky, unmoving,
cycling through a full set of phases every day, but only visible to half the planet.
With the moon ‘stationary’ above the earth, the tides seem to freeze in
place – half the world flooded, half with its water seemingly returned to the sea,
as if Earth is holding its breath to prepare for the worst.
As the moon sinks further, you might wonder if its gravity would overpower Earth’s, pulling you
up and ending your misery? Fortunately not.
The earth’s surface gravity is about 6 times stronger than the moon’s,
so even if the moon were hovering right on top of you, you would still stay on the ground.
On the moon things are different though: the near side of the moon is more strongly affected by
earth’s gravity, so during the next few months, it starts to stretch forward towards the earth, into
something of an egg, triggering deep moonquakes as the lunar rock flexes and changes shape. Though
barely noticeable now, this ‘squish’ will grow to hundreds of kilometers in a matter of months.
Month 8 - 11
At this point the apocalypse has arrived and we can summarize the months before the crash
as “everybody left has a really bad time”. The tides sweeping over the Earth slow down
and then reverse their direction because the moon now orbits earth faster than it rotates.
The planet will experience an abundance of earthquakes and volcanism. Massive amounts of
volcanic aerosols rise high into the stratosphere, shiny enough to reflect sunlight back into space.
What little light gets through is rust-red and is periodically diminished by daily eclipses.
The result is a rapid global cooling, with acid rains and summer snows killing even
the hardiest plants.The clock runs out on civilization. Billions have perished
while an egg-shaped moon is still drawing closer. Let’s get ready for the grand finale.
Month 12
Finally, at the end of the year,, the moon has reached the Roche limit. That’s the point
where Earth’s gravitational pull on the Moon is stronger than the Moon’s own gravity. Things on
the lunar surface start falling towards Earth and by the time it crosses 10,000 km the entire
moon disintegrates into rubble, smearing itself into a massive ring system around the earth.
Fortunately, the moon’s disintegration means the misery on Earth has ended.
No moon means the general apocalyptic nature of things comes to a halt. The oceans recede,
flowing off the land one last time.
Any survivors are treated to a view of tremendous arches spanning the sky,
glimmering in the sunlight, illuminating the night sky more brilliantly than any
full moon ever could, while meteor showers of moondust fill the sky.
It’s hard to say what happens next, but the tranquility may be short-lived.
If too much moondust rains down, friction heats the atmosphere – possibly boiling the
oceans. If not, the enormous shadows cast by the rings,
combined with all the volcanic and meteoric aerosols, block even more sunlight,
and a period of runaway cooling could begin that freezes much of earth’s surface solid.
In any case, at some point people will emerge again – from submarines or bunkers
or mountaintops. They will not have a great time before rebuilding civilization and their success
is not guaranteed – but at least they will try to do so with beautiful rings in the sky.
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