00:00Tidal locking is when a moon or a planet always shows the same face to another celestial body.
00:05I know I do.
00:07The moon, for instance, always shows one side to Earth.
00:11It doesn't matter if you use binoculars or a telescope,
00:14you'll see the same craters and planes every time.
00:18This happens with many big moons in space.
00:20Take Jupiter's moon, Io, or Saturn's moon in Cetalus.
00:24Even Mercury, which rotates three times around its axis for every two leaps around the Sun,
00:30is almost tidally locked to our star.
00:33Now, here on our planet, the moon's pull creates tides on Earth,
00:37making the water rise about a foot.
00:39This pull also stretches the moon, making it slightly football-shaped.
00:44Many years ago, the moon spun way faster than it does today.
00:48This made its protruding part shift constantly, like the Earth's tides.
00:51But the moon's bulges didn't align with Earth's pull.
00:55Soon enough, the Earth's gravity pulled them in closer,
00:58slowing the moon's spin until it stopped.
01:01But if we look at the grand scheme of things,
01:04we'll see that our planet isn't tidally locked to the Sun.
01:07Earth rotates on its axis, completing one rotation roughly every 24 hours,
01:13while orbiting its star.
01:14This rotation creates day and night.
01:17Lots of things prevent our planet from constantly showing the same face to the Sun.
01:21First, Earth's rotation rate isn't perfectly synchronized with its orbit around the star.
01:27The presence of the moon also plays a crucial role.
01:30Our satellite's gravitational pull creates tides on Earth,
01:33which slightly slows down Earth's rotation over time and balances things out.
01:38There's also quite an impressive distance between the Sun and the Earth – 93 million miles.
01:43So, even if the Sun's gravitational force is intense,
01:47it's far enough away to prevent tidal locking.
01:53Now, what if space travel gets advanced enough that we end up visiting such a tidally locked planet?
01:59One that is constantly trapped between two extremes – eternal darkness and constant sunshine?
02:05We can gather some data by figuring out what would happen if the Earth suddenly stopped spinning on its axis.
02:11Bad news is, the consequences would be devastating.
02:15Right now, we're all moving along with Earth's rotation, even if we don't feel it.
02:20If the planet stopped, everything on its surface would be launched eastward.
02:24People, buildings, and natural features hurtling sideways at high speeds.
02:29Afterward, the remaining high-speed winds, still rotating nearly as fast as the planet,
02:34would damage its surface, acting as a cosmic nail file.
02:37Even if the slowdown happened gradually, the effects would still be dramatic.
02:43The first noticeable change would be the Sun's motion across the sky.
02:47Without Earth's rotation, a day would last a half a year.
02:51This disruption would throw off our biological rhythms,
02:54affecting sleep dynamics and daily activities for many species.
02:58Earth's rotation also influences atmospheric patterns, which affect the weather and climate.
03:03Air currents would change too, leading to extreme events like desertification or the melting of polar ice caps.
03:11Hurricanes, reliant on Earth's rotation to form, would cease to exist.
03:16A motionless Earth would likely translate to the loss of our magnetic field,
03:20which shields us from harmful cosmic rays and solar storms.
03:24Boy, we in trouble now, huh?
03:25In the same thought experiment, let's say oceans won't freeze where it's cold or evaporate where it's hot.
03:35Because of its spin, there's a centrifugal force that has made our planet a bit wider around its middle.
03:41If we measure the Earth around the equator, it's about 13 miles wider than if we measure it from pole to pole.
03:47This widening of the solid Earth happened very slowly over billions of years.
03:52But the liquid water in the oceans would move more easily.
03:56Because of the spin, the water around the equator is about 5 miles higher than it would be on a still planet.
04:03If the Earth stopped spinning, the oceans would start moving towards the poles.
04:08At first, only some areas around the equator would become land.
04:11But eventually, a big continent would form in the middle, like a belt.
04:16You could walk around the Earth at the equator without getting wet,
04:19even though it would be really cold on one side and really hot on the other.
04:24The water that might move away from the equator would end up at the poles.
04:28There would be two separate oceans around each of these points,
04:31with no connection to the equatorial continent.
04:34In the north, Canada, Greenland, Asia, and Europe would all be underwater,
04:39following a line similar to the border between the US and Canada.
04:43But countries like Spain, for instance, would mostly stay above water.
04:47Despite these extremes, some say life could still exist in the twilight zone between light and dark.
04:54If we could draw it, it would be this softly illuminated region,
04:58looking like it's always on the brink of a sunset.
05:01This in-between domain could potentially offer the ideal conditions for life,
05:06with temperatures balanced between extremes.
05:08The planet would end up resembling an eye.
05:11Its sunward-facing hemisphere would look like a parched pupil,
05:14encircled by a blue-green iris, the place with lots of water and vegetation.
05:22Now, it's not all that grim.
05:24Since there's liquid water on our planet's surface,
05:27sunlight could turn it into clouds that could help us control the temperature,
05:31should it stop spinning.
05:32Also, the way heat moves around in the air could make the climate nicer overall.
05:38Winds could carry warmth from the sunny side to the dark side,
05:41similar to how ocean currents warm up Europe and cool down Africa.
05:46Plus, the way gases move in the air might stop a planet from getting stuck facing one way all the time.
05:52Venus, for instance, should be locked in place facing the sun,
05:55but its atmosphere helps keep it turning.
05:59Our planet might end up pulling a similar trick.
06:02Rainfall on a tidally locked planet could further regulate temperatures,
06:06especially if there's enough land.
06:07On Earth, rain interacts with rocks, trapping carbon and cooling the atmosphere.
06:13This process could also help manage carbon dioxide levels.
06:17If we were to prepare for a tidally locked world,
06:21the Sahara Desert would be a good place to start the boot camp.
06:25Located in North Africa, it is the biggest hot desert globally.
06:29It covers a vast area from the Atlantic Ocean to the Red Sea
06:32and from the Mediterranean Sea to the Sahel region.
06:35During the day, the temperatures get really hot, up to 122 degrees Fahrenheit,
06:41and at night, it can get as cold as 41 degrees.
06:45That is a wide swing.
06:46You might stumble upon a sandstorm here and there, but rain is very rare.
06:51When it does happen, though, it's intense and can cause flash floods,
06:55making the area dangerous.
06:57Despite the tough conditions, some animals manage to survive here.
07:01One such creature is the Kennec fox, which is the smallest fox to exist on our planet.
07:06It has big ears that help it handle the heat,
07:09and its environment stretches from Morocco to Egypt,
07:12and even down south to northern Niger and east to Kuwait.
07:16It eats whatever birds, insects, and rodents it can find in the sand.
07:20As for the coldest place on Earth, data suggests it's located in the eastern Antarctic plateau.
07:28Research indicates that the air temperature there can drop to minus 137 degrees Fahrenheit.
07:34Now, if we need to find animals that have adapted well to living in
07:38refrigerator with built-in ice maker-like conditions,
07:41we just need to look at the emperor penguins.
07:44They gather in tight groups, sometimes with huge numbers of these birds, to keep warm.
07:48They can't stay in these huddles for too long, though, because they get too hot.
07:53Scientists found out in 2015 that it can get as hot as 100 degrees Fahrenheit
07:58in the middle of the penguin mosh pit.
08:01These birds are the only animals that produce offspring during the Antarctic winter.
08:06They travel quite far, somewhere around 50 to 100 miles, to lay just one egg.
08:12While the dad keeps the egg warm for about two months,
08:15mom goes back to the edge of the ice to find food.
08:18It's a routine that usually works well, as long as the weather is consistent.
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