00:00Hey, listen up. There's a red alert.
00:03NASA supercomputers have calculated that there are only 2,021 years left until the end of the Earth.
00:10Our planet is about to...
00:12Oh, wait a minute.
00:14Oops, I'm sorry.
00:15I thought these zeros were a mistake.
00:17Well, the research actually says 1,000,000,000,000, 2021 years in the future.
00:22Woo, that's a relief.
00:24Breathe normally.
00:25Still, this means that our planet officially has an expiration date.
00:32And no, this is not science fiction.
00:34It's a very real study that shows how, why, and when life on Earth will end.
00:41So, thanks to NASA and Japan's Toho University, we can now mark the calendar.
00:47It'll happen in around a billion years.
00:49But what about how and why?
00:52Well, even as recently as the early 20th century, scientists still didn't know what powered the Sun.
00:58One of the first big ideas was that the Sun was basically a giant piece of charcoal.
01:03Just a huge ball of fire burning some kind of fuel.
01:07But that was easy to rule out.
01:09At the rate the Sun puts out energy, it would have burned through that kind of fuel in just a few thousand years.
01:14And even back then, geologists and paleontologists already agreed that Earth was at least 100 million years old, if not more.
01:23That meant the chemical burning couldn't have possibly kept the Sun shining for that long.
01:30So, scientists turned to another, more nerdy theory.
01:34Gravitational contraction.
01:35This idea was that the Sun shines because of its own weight.
01:40Its gravity pulls all the gas inward, squeezing itself tighter and tighter.
01:45It's kind of like warming your hands by rubbing them together.
01:49We know that gas giants like Jupiter and Saturn are slightly contracting under their own weight and giving off more heat than they get from the Sun.
01:57So, yeah, gravitational contraction, also known as the Kelvin-Hemmholtz mechanism, is very much real.
02:04But it's not what powers the Sun.
02:07When researchers did the math, it showed the Sun could only shine like that for about 20 to 30 million years.
02:14Eventually, scientists learned that the real secret behind the Sun's power and longevity was something way more powerful.
02:21Nuclear fusion.
02:23Now, deep inside the Sun, it's unbelievably hot.
02:26We're talking 27 million degrees Fahrenheit.
02:29And it's under crazy pressure, because the Sun is so big and heavy.
02:33All that heat and pressure squashes hydrogen atoms and forces them to stick together.
02:39When four hydrogen atoms get squished hard enough, they turn into something new, a helium atom.
02:46When that happens, a little bit of their mass turns into energy, and that's what becomes sunlight and heat.
02:52For centuries, people feared the Sun would someday go cold.
02:57And that will happen.
02:58Eventually.
03:00About 5 billion years from now, our star will run out of hydrogen, and gravity will take over.
03:06But long before that, Earth will already be toast.
03:09According to a NASA life extinction prediction, our planet will become a scorched, uninhabitable rock, not because the Sun will go out, but because it will burn too hot.
03:20It turns out that those old apocalyptic ideas were not completely off.
03:25The Sun will destroy life on Earth, just not by going cold.
03:30But why?
03:31Well, it's because, with time, the Sun is getting brighter.
03:35And I'm not talking about its mood.
03:37It releases more energy.
03:39It's a slow, natural side effect of the nuclear fusion we just mentioned.
03:44Deep in the core, the Sun has been fusing hydrogen into helium for billions of years.
03:49But as more helium piles up, the core gets denser and hotter.
03:55Think of it like a pressure cooker.
03:57The more pressure builds up inside, the more heat rises from within.
04:01That extra heat speeds up fusion, which means more energy gets released, and the Sun starts shining just a little bit brighter.
04:09It's not dramatic.
04:10We won't notice it in a lifetime.
04:12But the future-proof androids we're going to build just might.
04:16With time, the extra heat adds up.
04:19The Sun is already about 30% brighter than when the Earth was born.
04:24But life decline is going to happen much, much earlier, even before the given deadline.
04:29As the Sun keeps cranking up the heat, Earth is gonna sweat.
04:34The extra sunlight raises global temperatures to the point where the ocean surfaces hit around 117 degrees Fahrenheit.
04:41That's hot enough to mess with the planet's entire climate system.
04:45Water vapor begins to rise from the oceans and accumulate in the upper atmosphere.
04:51This causes even more heat to be trapped, creating a thick, humid layer around Earth.
04:56Scientists refer to this ongoing cycle as the moist greenhouse effect.
05:01The rising temperatures aren't just drying out our planet.
05:04They're also harming plants.
05:06Plants rely on carbon dioxide from the air to grow and thrive.
05:10However, as Earth warms up, certain natural processes can take too much carbon dioxide out of the atmosphere.
05:18When that happens, there won't be enough CO2 left for plants to survive.
05:23Forests will disappear first, then grasslands, bushes, and even the toughest plants that usually handle extreme heat.
05:31This all will lead to oxygen collapse, because plants and CO2 are crucial for photosynthesis.
05:37In simple terms, this is how plants use sunlight, along with water and carbon dioxide,
05:43to create their own energy and produce oxygen as a waste product.
05:47Right now, oxygen makes up about 21% of Earth's atmosphere.
05:52But once it drops below even 1%, complex life as we know it will most likely disappear.
05:58Earth's biosphere will shrink to just a few microbes and extremophiles, hiding deep underground.
06:06But even they won't last long.
06:08It's worth noting that scientists ran two versions of the simulation,
06:12one with life like we have today, and one with none at all.
06:16Surprisingly, both worlds lost their oxygen at about the same time, around 1 billion years from now.
06:23That means plant life and photosynthesis do help, but they're not the main thing keeping oxygen in the atmosphere.
06:30It's actually a long-term chemical battle between volcanic gases and rocks that gradually soak up oxygen like a sponge.
06:38And even after most life is gone, the heat will keep going, causing oceans to boil.
06:44Not all at once, but slowly and steadily, the oceans will begin to evaporate into the atmosphere.
06:50But that vapor won't just come back down as rain like it does now.
06:55Why?
06:56The atmosphere will be too hot and thick for that.
06:59Instead, sunlight will start breaking the water apart, and hydrogen will escape into space permanently.
07:05Once it's gone, it's gone for good.
07:08Basically, instead of raining back down, Earth's water will slowly leak into space until there's nothing left.
07:15Even before the last puddles vanish, life under the sea will be long gone.
07:21Once the balance of temperature and oxygen is lost, not even the hardiest ocean life can hold on.
07:27In the end, Earth will become something we can barely recognize – a dry, lifeless rock.
07:33There will be no water, no oxygen, and no life left.
07:37The oceans will be gone.
07:39The atmosphere will be thin and toxic.
07:41Even the most resilient microbes will have disappeared.
07:45However, the Sun will still shine in the sky.
07:48Earth will keep orbiting, just like always.
07:51It'll still be a planet, just without life.
07:54But long before that cosmic finale, Earth will already be uninhabitable.
07:59Which raises the big question.
08:01So, what could future humans do about all this?
08:05Well, escaping sun radiation and extinction might end up being humanity's biggest engineering challenge yet.
08:11Maybe we'll build massive space colonies and leap from planet to planet, staying just ahead of the Sun's deadly heat.
08:19Even if we terraform Mars, making it more Earth-like so we can inhabit it, it'll still be cooking in the same solar oven, just on a lower shelf.
08:28Or maybe we'll live in giant rotating space habitats, like O'Neill Cylinders, floating mini-worlds with gravity and recycled air, water, and energy to support long-term survival.
08:41Those could drift farther and farther from the Sun as things heat up.
08:44Or who knows?
08:46Maybe we'll upload our minds to the cosmic cloud or hop into a higher dimension and watch the universe like it's, you know, Netflix.
08:53Okay, this is definitely too nerdy, and we're going deep into sci-fi territory.
08:59But whatever the solution may be, humankind has a long time ahead to figure out how to survive the eventual end of Earth and life.
09:08Or maybe even preserve it, in whatever form it takes.
09:11That's it for today.
09:15So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
09:20Or if you want more, just click on these videos and stay on the bright side!
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