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00:00The asteroid that ultimately killed the dinosaurs was 6 to 9 miles wide.
00:04When it struck Earth, it left a crater 93 miles wide.
00:09It released the energy equivalent of 10 billion Hiroshima bombs,
00:14triggered near-constant fires, and possibly plunged the world into a years-long darkness.
00:21Do you think we could survive the same again?
00:25CAST YOUR IMAGINATION BACK TO EARTH 66 MILLION YEARS AGO
00:31It's a tricky task, because really, we need to think of a very different planet.
00:35The climate, the atmosphere, the basic layout of land and water⊠nothing is like it is today.
00:41There are long stretches of extreme heat, far outstripping even the hottest conditions in
00:46modern times. The humidity is also extreme, and the air is choked with four times the amount
00:52of carbon dioxide. There are complete land bridges, connecting whole regions that have
00:57since been covered over with the water of the oceans. If you were to somehow be magically
01:01transported back to then, it's a fair bet that you might not even recognize Earth at all,
01:06that it might just as well double up as an alien planet, thanks to the many,
01:10many changes that have happened in the millions of years between then and now.
01:14Nevertheless, and according to most models, we do know of at least one key aspect,
01:20one key moment, from all those years ago. We know that at some stage, Earth experienced a very
01:26bad day. An asteroid, at least six miles wide, slammed into what's now Mesoamerica.
01:33This was the Chicxulub impactor, and when it hit, it unleashed unimaginable energy,
01:38equivalent to millions of atomic bomb detonations. Much of the local area was instantly vaporized.
01:45Huge shockwaves rippled across the globe. At the time, the dinosaurs were the undisputed
01:51rulers of our planet, towering over every other living thing, at the top of a food chain that
01:57may well never have crumbled if Chicxulub hadn't happened. But it did happen, and history shows
02:03how it triggered a monumental shift. It wasn't that the asteroid instantly killed all the
02:08dinosaurs. Although it's often misunderstood to have been a true before-and-after moment,
02:13in reality it wasn't quite so quick. The impact triggered unprecedented weather events,
02:18which over time caused the atmosphere to settle back differently. Some of the dinosaurs did
02:23perish within just weeks, months, and years. But many clung on, perhaps for as long as 10,000 or
02:30even 100,000 years post-asteroid. Ultimately, though, the ongoing, lingering, and in many
02:36cases irreversible effects of the rock did make it impossible for the dinosaurs to continue.
02:42They went extinct, and while we do have crocodiles, some ocean creatures, and most
02:48birds who are directly related, as a whole, they never came back. In their place, Earth witnessed
02:54the rise of the mammals. It was a rapid ascension from small, shrew-like creatures to a constantly
03:00expanding, rich, and diverse new class of animal. They could thrive in a new world without the
03:06energy-consuming, nature-shifting, mammal-eating dinosaurs of before. And of course, from there,
03:11eventually, we were born. The timeline of humankind is long and complicated in itself,
03:17with offshoots all over the place, and various other key moments that combine to form our story.
03:23But the long and the short of it is that had the asteroid not hit, then we wouldn't be here. We
03:29effectively owe our lives to the asteroid that killed the dinosaurs. So, with all of that
03:35considered, what would unfold if the same thing really were to happen again? What if the universe
03:40had another cosmic bullet in the barrel? And what if one day it were sent hurtling towards us
03:46for a second time? Thanks to modern technology, we likely would at least know that it was coming.
03:51Our skies are now constantly scanned with an ever-increasing arsenal of cutting-edge telescopes.
03:56But nevertheless, upon arrival the immediate scene would be much the same as it was for the
04:02dinosaurs. The sky erupts in a blinding flash that's far brighter than the sun, or even multiple suns.
04:09The light engulfs the landscape, breaches the horizon, and spreads. The asteroid has entered
04:15into our atmosphere and is burning at temperatures exceeding thousands of degrees. Seconds later,
04:20and there's a deafening roar, a sound unlike anything that humanity has ever heard. It rolls
04:26across the planet, permeating everything that's around you at the time. Then, if you're close to
04:32the impact zone then, well your life is already in extreme danger. If you're on the other side of
04:37Earth, then perhaps you'd feel a little safer. But really, everyone should be terrified. The
04:43shockwaves of the strike reverberate. It levels buildings, shatters glass, rips through roads,
04:49houses, towns, and cities. There's a long sequence of massive and devastating earthquakes and
04:54tsunamis. Coastal cities would be wiped off the map within minutes. Tectonic fault lines would
05:00break. A huge number of volcanoes would be at risk of eruption. The unimaginable energy involved
05:05means that an endless stream of superheated dust and debris is launched into the sky.
05:10There's a growing and deadly cloud of choking material that soon infiltrates the atmosphere
05:14properly. And if it wasn't bad before, now is when things really heat up. In the very worst
05:20case scenarios, the scorching ejecta blocks out the sun. And not just for a couple of hours,
05:26as they were for the dinosaurs, these terrible changes are for the very long term. We know that
05:32Earth is resilient, and that over thousands or millions of years, it will survive. But the new
05:37conditions would certainly be a death knell for the vast majority of life on it. Mammals,
05:42while reasonably hardy, are in many ways less prepared for global disaster than the dinosaurs
05:48would have been. Humans, for all of our supposed intelligence, would also be at a complete loss
05:53in the face of a new normal that simply wouldn't accommodate us. With the new atmosphere thickening
05:58into something like a toxic soup to drown in, even once the initial temperatures post-event
06:04start to fall, there still isn't much hope. With the life-giving sun now struggling to break
06:09through, it should actually get colder and colder across the centuries that follow. A phenomenon
06:15otherwise known as an impact winter. Any crops that did survive the strike itself would ultimately
06:20fail. Forests would wither. Photosynthesis would shut down. The delicate balance of the food chain
06:27as we know it would collapse. Human society, which is ultimately built upon all the expected
06:33patterns of the current natural world, could never hold up, even if there were surviving
06:37humans to populate it. Supply chains, travel links, communications networks, clean water systemsâŠ
06:43they all would break, and would soon be forgotten. In their place, and over time, Earth would play
06:49host to new fundamentals. New soils, forever peppered with the burning ash of the asteroid
06:54strike. New land masses, freshly shaped following the initial turmoil of the event. Unknown air,
07:01breathable to some, perhaps, but not to most. How do you see it going from there? Let us know
07:07in the comments. Importantly, humankind does possess an ingenuity that the dinosaurs didn't,
07:13so perhaps there is some hope that if anyone survives, then they might be able to build our
07:18species back up. In the style of science fiction, though, the last humans would need to escape
07:23underground. They'd have to, in some way, live below the surface that could now offer them very,
07:28very little. The once sprawling cities are gone. Because, while most probably would survive the
07:34asteroid itself, none could carry on operating under Earth's new rules. To our minds, it would
07:40be an apocalypse, just as it was for the dinosaurs. For Earth as a whole, an asteroid strike is
07:47something like a hard reset. In all likelihood, new forms of life would emerge, just as they
07:53did during the rise of the mammals. But the details of that life are impossible to know.
07:58Perhaps, in another 66 million years or so, evolution will have continued in such a way to
08:04spawn another species that's intent on finding out more. But, in truth, there's little reason
08:10to believe that anything even like a human would happen again. What do you think? Is there anything
08:16we missed? Let us know in the comments, check out these other clips from Unveiled,
08:20and make sure you subscribe and ring the bell for our latest content.