From the Extinction of the Dinosaurs to the Beginning of the Universe: 20 VAIENCE "What Ifs" and Mysteries

The first episode opens with a theory about why so many cultures have dragon legends: people mistook dinosaur fossils for dragon bones.

According to the video, about 66 million years ago an asteroid estimated at 10 km to several tens of kilometers in diameter struck near what is now Mexico's Yucatán Peninsula, and about 75% of Earth's species are thought to have died out. The video also presents a theory that a 1.5-km-high tsunami hit the Gulf of Mexico, and research estimating that even places more than 1,800 km from the impact site reached an average temperature of 155°C, and in some cases over 500°C. Afterward, sulfur-bearing dust blanketed the Earth, temperatures plunged, and plants withered. Herbivores starved, followed by carnivores, and the dinosaurs, many of which were large species needing vast amounts of food, died out. This is described as the leading theory.

However, the video also points out that birds branched off from dinosaurs, so strictly speaking the dinosaurs did not go extinct. That means "a world where the dinosaurs didn't go extinct is the world we live in now." Since that wouldn't be very interesting, the video moves on to a thought experiment in which Mr. Vaience diverts the asteroid's orbit.

What would have happened without the impact? The video notes that there are theories that dinosaurs were already in decline before the impact, and that volcanic activity in India on a scale rare in Earth's history played a role. On the other hand, some research holds that 66 million years ago the dinosaurs had spread to every continent and their diversity was at an all-time high. On that basis, the video says it is highly likely that, without the impact, nothing could have completely halted the dinosaurs' momentum.

What would change dramatically, it says, is the evolution of birds and mammals. The reasons they survived are given as their ability to dig burrows and hide, and their varied diets, which let them get through the era of famine. They then diversified to fill the ecological niches the dinosaurs had vacated. Citing Halszkaraptor, which is thought to have lived much like a waterbird, the video says dinosaurs once also filled the roles now played by birds and mammals. Furthermore, there is a theory that mammals were in fierce competition with their close relatives, the mammaliaforms, and won out amid the drastic environmental changes after the extinction, so it is impossible to say which would have prevailed without the impact.

As for whether a creature with human-like intelligence would have emerged, the video says many scientists believe advanced intelligence consumes a great deal of energy and is not necessarily advantageous, so the question remains open. If such a creature had emerged, one trait mentioned is color vision. Most mammals can distinguish only two colors, a remnant of their nocturnal past (the nocturnal bottleneck), whereas birds and reptiles see four and humans three. The video speculates that humans in a world where dinosaurs ruled the daytime might have remained dichromatic, seeing a washed-out world. On the other hand, it says that since humans have lived alongside dangerous animals such as elephants, lions and hippos, they probably would not have been hunted to extinction.

The next episode is structured to let viewers experience "that day" at the K-Pg boundary separating the Mesozoic and Cenozoic eras. At the time, carbon dioxide levels were high, average temperatures are thought to have been 5–10°C higher than today, and dinosaurs had spread to every continent, including Antarctica.

Iridium found in rock layers around the world is presented as evidence of the impact. Because iridium is heavy, it sank deep into the Earth when the planet formed and is almost absent at the surface, but asteroids contain relatively large amounts of it. In addition, the bones of fish from that time, such as sturgeon, show tree-ring-like patterns caused by seasonal differences in growth, and analysis of fossils from the impact layer reportedly shows that the impact occurred in the Northern Hemisphere's spring.

Some questions remain unresolved, however. Estimates of the asteroid's size range from 10 km to several tens of kilometers, and the impact energy has not been pinned down either, ranging from tens of millions to 100 million megatons of TNT. Comparing this with the Hiroshima bomb at 0.015 megatons and the Tsar Bomba at 50 megatons, the video says the only certainty is that it was on an entirely different scale.

The immediate aftermath is depicted as follows. A fireball several times brighter than the Sun appeared, and temperatures exceeded 100°C even 1,800 km away. The tsunami generated by the ocean impact is projected to have reached up to 1,500 m, and estimates suggest it penetrated more than 100 km inland from the coastline and exceeded 10 m even along the Pacific coast. Debris thrown up into space rained down across the globe, compressing the atmosphere and generating heat as it reentered. One theory puts the total energy at 20 million megatons of TNT, and large-scale wildfires are thought to have broken out in North America and in Australia and India, on the opposite side of the globe from the impact site.

The video emphasizes that this asteroid struck "in the worst possible place, in the worst possible way." Based on the density of the ground at the crater, it most likely hit at a shallow angle of 45–60 degrees, an angle at which more bedrock is ejected into the atmosphere. Moreover, the floor of the shallow sea contained a lot of gypsum, composed mainly of calcium sulfate, so huge amounts of sulfur-bearing dust were thrown up. This reacted in the stratosphere and blocked sunlight, and soot from the wildfires added to the effect. One theory holds that 100 billion tons of sulfur were released, temperatures dropped by more than 20°C, and extreme weather persisted for about 30 years. Simulations indicate that if plants died off and a food crisis lasted half a year, the food chain would collapse.

As for why the dinosaurs died out while other animals survived, the video says humanity still has no clear answer. On the dinosaur side, theories include that they were large and warm-blooded and needed a lot of food, and that because they laid eggs, adults and juveniles differed greatly in size and ecological role, making them vulnerable to environmental change. On the survivors' side, theories presented include that they could eat plant seeds, and that the mass of carcasses caused fungi to flourish, giving mammals with strong immune systems an advantage.

Finally, the video quotes science fiction writer Larry Niven: "The dinosaurs became extinct because they didn't have a space program." It closes by noting that one estimate puts the chance of a 10-km-class asteroid impact at 1 in 10,000 per century, and that with current technology we could detect one but not change its orbit.

Point Nemo is the point in the world's oceans farthest from any land. It was calculated in 1992 using a computer program by Croatian-Canadian surveyor Hrvoje Lukatela, who did not actually visit the spot. Its name comes from "nemo," Latin for "no one," and from Captain Nemo of Twenty Thousand Leagues Under the Seas. A 2018 study placed it at approximately 49°S, 123°W. The nearest land is Ducie Island, Motu Nui and Maher Island, each about 2,700 km away. The video illustrates this isolation with a circle whose radius is the straight-line distance from Miyakojima to Wakkanai in Japan (about 2,720 km), with no land at all inside it. The nearest humans would be either residents of Easter Island or the crew of the International Space Station passing about 400 km overhead.

That said, it is not as if no one has ever been there: round-the-world yacht races pass nearby, and a small number of cargo ships also sail in the vicinity. The fastest recorded trip by boat is said to be 15 days, 10 hours and 37 minutes. Once past the often-stormy South Pacific, the wind and waves calm down inside the South Pacific Gyre. The average annual water temperature is 7°C and the depth is about 4 km, so swimming is not recommended.

As for life, because of the gyre and the distance from land, the seawater is poor in nutrients, plankton is scarce, and so is marine snow. Microorganisms on the seafloor number only about 1/1,000 to 1/10,000 of those outside the gyre, and the area is sometimes described as "the deadest place in Earth's oceans." On the other hand, around hydrothermal vents there are ecosystems that do not depend on sunlight, and crustaceans of the genus Kiwa, known as "yeti crabs," have been found there. It is also where decommissioned satellites are brought down; the former Soviet Union's Mir, among others, fell there. Since there are plans to bring down the International Space Station nearby in 2031, it is also called the "spacecraft cemetery."

The whale shark, the world's largest fish, typically grows to around 10 m, and up to about 20 m at most. The video first looks at its reproduction. Most fish use external fertilization, but whale sharks use internal fertilization, with the male inserting reproductive organs called claspers, of which it has two. A mother shark found in Taiwan in 1995 reportedly suggested that whale sharks may store sperm they receive and use it gradually to become pregnant repeatedly.

To the main question, "Can you be eaten?", the video's answer is no. Whale sharks feed on plankton and have a gentle temperament. Their mouths contain more than 8,000 small teeth, but these are vestigial and smaller than grains of rice, and a large human who got inside would simply be spat out.

So, as a thought experiment, Mr. Vaience is shrunk to about 1 cm and placed on a krill to be swallowed. Plankton sucked in along with seawater is filtered out by the gill rakers, concentrated, and sent into a narrow esophagus only a few centimeters in diameter. In the stomach, the krill are broken down. Because whale sharks swim vertically to suck in food at the surface, the inside of the stomach keeps rocking during a meal. The intestine has spiral folds that improve digestion and absorption, and anything drifting through bumps against them as it moves along. Whale sharks are also said to turn their intestines inside out through the anus to flush out undigested material. If you make it through all that, the journey ends with you expelled through the cloaca along with feces.

Easter Island lies about 2,000 km from the nearest inhabited island (Pitcairn Island, population under 50). According to the video, the leading theory is that the moai began to be built around 1200 AD and peaked around 1500. Most were carved from soft rock near the crater of one of the island's volcanoes. Even the statues that appear to be only heads mostly just have their upper bodies buried in the soil, and they are thought to have once had eyes made of coral and obsidian. The average statue is about 4 m tall and weighs about 10 tons, and some approach 10 m in height and 80 tons in weight.

How they were transported is not clear, but one hypothesis is that ropes were tied around the head and the statues were moved upright by rocking them side to side. Relatively small statues could reportedly be moved long distances by about 18 people. This is said to match well with the indigenous oral tradition that "the moai walked to their platforms."

The reasons for building them are explained in terms of both religion and politics. The moai embodied ancestors and were believed to gain spiritual power if made in the proper way, so they were erected facing inland, as if watching over the inhabitants. They were believed to bring fertility to the fields, and a recent study reportedly suggests that carving the rock may in fact have added nutrients to the surrounding soil and improved harvests. Politically, at least two factions coexisted on an island about a quarter the size of Tokyo's 23 wards. The moai may have been symbols of those in power, and the very act of mobilizing many skilled specialists to build them is said to have served to demonstrate a ruler's strength.

The second half examines the well-known "civilizational collapse" theory. According to a hypothesis put forward in the early 21st century, excessive deforestation to build moai led to soil erosion, a food crisis and a dramatic population decline, and the religion was forgotten. This was told as a warning about global environmental problems and became a subject in Japanese textbooks.

The video, however, notes that this theory has many critics. Even granting that forests existed, that they disappeared after humans arrived, and that rainfall may have decreased around 1500, a study of the genes of descendants of the indigenous people found an extreme population decline unlikely, and the population was likely growing gradually until Westerners arrived. There is also a theory that moai and platforms were still being built until the 18th century. Under the theory that what destroyed the society was disease and slave raiding brought by Westerners, more than 1,000 people were taken away in the 1860s, and by the 1870s only about 100 indigenous people remained. Recent mainstream thinking also holds that the loss of forests was driven more by the rats that arrived with humans. The video says that even explanations that seem logical need to be checked against the facts, and concludes that learning about the past without oversimplifying it broadens our options for the future.

The Great Sphinx is 73 m long and 20 m tall, and unlike the pyramids, which were built by stacking millions of stones, it was carved from a single mass of limestone on the Giza Plateau. Geologically, the rock can be divided into three layers: the feet were carved from the lower layer, the body from a middle layer of alternating soft and hard rock, and the head from the hard upper layer. The video sees the craftsmen's ingenuity in using the hard, weather-resistant layer for the head, which required fine detailing. The body, meanwhile, has weathered considerably. Rock from the middle layer was also used as building material for two temples planned in front of the Sphinx, but the temples were reportedly left unfinished.

Over roughly 4,500 years, the Sphinx was repeatedly buried in sand and dug out again. In an early-19th-century drawing, it is buried up to its shoulders. Some scientists have estimated past rainfall from the weathering of the body and claim it was built more than 7,000 years ago, but most archaeologists dismiss this, and the mainstream view is that it dates from the same period as the three great pyramids.

The mainstream theory is that it was built by King Khafre, and several pieces of evidence are given. The face is said to resemble Khafre (though some say it resembles his father Khufu, so this alone is not sufficient). Khafre's pyramid stands directly behind the Sphinx. And at sunset on the spring and autumn equinoxes, viewed from the temple in front, the sun sets at a point between the Sphinx's shoulder and the base of the pyramid.

Its involvement with later eras is also covered. About 3,400 years ago, Thutmose IV carried out a major restoration and erected a 3.6-m stele. Its inscription says that when he was a prince napping in the Sphinx's shadow, the sun god appeared in the form of the Sphinx and told him that if he dug it out, he would be made king. Thutmose IV, who was not first in line to the throne, is thought to have used this to lend prestige to his accession. He is also thought to have added a stone beard, and part of a beard was found near the front paws in 1817.

As for the missing nose, the theory that Napoleon's army shot it off is ruled out on chronological grounds, since drawings from the early 18th century already show the Sphinx without a nose. The leading theory dates it to the late 14th century: a Muslim, angered that farmers were making offerings to pray for good harvests, is said to have chiseled off the nose.

The proposal to measure the development of cosmic civilizations by their energy consumption was made in 1964 by Soviet astronomer Nikolai Kardashev. His argument was that no civilization can ignore the laws of physics and energy conversion can never be 100% efficient, so other civilizations could be found by observing the energy they emit.

The original scale had three levels: Type I is a civilization close to Earth at the time, Type II uses the energy of a star, and Type III harnesses energy on a galactic scale. However, the Type I benchmark was based on Earth in 1964 and differs from today, and the Type II value varies greatly depending on the star. Kardashev himself reportedly stated clearly in his paper that the scale was provisional. The formula most commonly used today is the one proposed by Carl Sagan: "take the logarithm of power consumption (in watts), subtract 6, and divide by 10." Under this formula, 10¹⁶ W corresponds to Type I.

Applying this formula, a civilization using all the solar energy reaching Earth would rate about 1.1, while present-day humanity is just over 0.7; reaching Type I would require increasing our energy use about 500-fold. Even so, global energy consumption is growing by 1–2% a year, and one study reportedly projects that we will reach Type I in 2371. The video adds that aggressively using fossil fuels might speed this up, but in that case we should probably worry more about civilizational collapse from climate change.

Type II uses 10 billion times the energy of Type I. Using all of the Sun's energy would rate just over 2.0. Such civilizations are imagined to build structures like Dyson spheres around their stars; the video cites an astronomer's description that these should glow "like ornaments on a Christmas tree," and Freeman Dyson's argument that they could be found by searching for infrared sources. For a Type II civilization, the only existential threat is said to be something like a nearby supernova. A Type III civilization (10³⁶ W) could prevent even that, and in the distant future when stars have dwindled, it might even build Dyson spheres around black holes.

However, even a Type III civilization cannot get past the light-speed barrier. The Milky Way is about 100,000 light-years in diameter. The proposed solution is self-replicating spacecraft that spread by building copies of themselves from the resources of each star system they reach, and they are estimated to be able to cover the entire galaxy in about 500,000 years. The video ends with a flight of fancy: a machine that finds an immature civilization might lie dormant on one of its moons and activate when that civilization reaches it, so the possibility that a robot is sleeping on our Moon is not zero.

At the start, the video says that as of 2022, there were an estimated 13,000 nuclear weapons in the world. As an example of the brink of nuclear war, it takes up the 1962 Cuban Missile Crisis. A Soviet submarine being chased with depth charges by the US military was carrying a nuclear weapon, which could be launched with the agreement of all three officers. The captain and one other officer agreed, but Vasily Arkhipov firmly refused. After a heated argument in the sub, whose air conditioning had broken down and which had become extremely hot, his refusal prevailed and the submarine surfaced.

The video says many experts believe that once nuclear weapons are used even once, a chain of retaliation is unavoidable. Russia is said to have an automatic retaliation system, commonly called the "Dead Hand," and the United States also maintains a rapid-response posture.

As a concrete example, the video presents "Plan A," a simulation published by Princeton University in 2019. Russia fires one weapon at a military base near the German-Polish border, and NATO retaliates with one. Next, Russia fires 300 and NATO 180, causing 2.6 million casualties in about three hours. The US fires 600 at Russian nuclear facilities, and Russia fires back at the US mainland: 3.4 million casualties in 45 minutes. In the final phase, both sides target each other's major cities: 85.3 million casualties in 45 minutes. In total, the estimate is 34.1 million dead and 57.4 million injured within about five hours.

The video gives three reasons why these figures may seem smaller than one might imagine: the scenario assumes cities are not targeted until the final stage, the war is limited to NATO and Russia, and only direct casualties from the nuclear explosions are counted. More serious, it says, is soot from urban fires. A 2019 University of Colorado study found that 150 million tons of soot would remain in the upper atmosphere for several years, temperatures would drop by 20–30°C across much of the Northern Hemisphere, and food production (in calories) over the five years after a nuclear war would fall by more than 97% in China, France, Russia, the UK and the US, and by more than 99% in some countries. The first to suffer would be countries with low food self-sufficiency, such as Japan and South Korea, and the video says more people would likely die from starvation than from the explosions themselves. One estimate also puts the loss of ozone at around 75%. The video mentions that in January 2022, the leaders of the US, Russia, China, France and the UK issued a joint statement on preventing nuclear war, and concludes by expressing the hope that it will not prove to be empty words.

By one estimate, fusion produces 20 million to 100 million times more energy than fossil fuels per unit weight of fuel. It emits no carbon dioxide, its fuel could potentially be extracted from water, and because the reaction is easy to stop, the risk of a major accident is thought to be low.

The fundamental difficulty is the repulsion between positively charged atomic nuclei. Causing fusion on Earth is said to require temperatures of at least 100 million degrees, and no solid can withstand that. Researchers are therefore pursuing magnetic confinement, which traps plasma in powerful magnetic fields, and inertial confinement, which uses lasers to create shock waves in fuel pellets. For the former, Europe's JET achieved an energy ratio of 0.67 in 1997, and ITER, in which Japan also participates, is being developed as its successor. For the latter, the US National Ignition Facility (NIF) was reported in 2022 to have achieved a ratio of 1.5, and private companies have been entering the field one after another.

Still, the video says the hurdles to practical use remain high. Converting the energy produced into electricity can never be 100% efficient, and the ratios for magnetic confinement do not include the energy used by the magnets. The question is whether it can be economically viable once these are subtracted.

As for the effects if it were achieved, the video first points out that it would come too late to address climate change. About half of industrial carbon dioxide comes from power generation and heating, but meeting the 1.5°C target requires a 43% cut by 2030, and fusion, which will arrive decades from now at the earliest, would be too late. In addition, fusion itself does not produce long-lived radioactive waste, but depending on the fuel, it releases large numbers of neutrons that could make the surrounding materials radioactive. On the other hand, if a method using only deuterium became practical, fuel could be obtained from seawater, which might reduce conflicts over oil and water and make desalination realistic. The video also mentions that one participating country's acts of aggression have put its future contributions to ITER in doubt, and says that if fusion reduces conflict, we can look forward to humanity's subsequent development.

In 1812, Charles Redheffer of Philadelphia exhibited a "perpetual motion machine" and charged admission, but it was a fraud. The video first defines work in physics (force × distance; lifting 1 kg by 1 m takes about 9.8 J) and energy (the capacity to do work). It then defines a perpetual motion machine as "a device that performs work on the outside world forever without any external energy supply." Wind power does not qualify because it derives from solar energy, and an object moving by inertia in space does not qualify either, because it slows down if energy is extracted from it. Da Vinci also sketched designs for weighted wheels, but no one has ever succeeded. The explanation is that such machines violate the first law of thermodynamics (conservation of energy) and the second law (heat flows from hot to cold).

Still, if one were completed as a thought experiment, using perpetual motion machines to build more perpetual motion machines would yield unlimited energy without fuel. Desalinating seawater and transportation would become easy. Firing carbon or neon nuclei at high speed into lead or bismuth produces gold with a certain probability, so resource shortages would also move toward a solution.

What the video emphasizes is that the effects would extend to the entire universe. If energy could be created from nothing, the amount of matter, which is equivalent to energy, would also increase. The currently favored future for the universe is the Big Freeze, but it is conceivable that several billion years or more from now, the gravity of the added matter could overcome expansion and cause the universe to start contracting.

The Sahara Desert covers about 9 million km², roughly 24 times the area of Japan. Some areas in the center and toward the east receive just 0.5 mm of rain a year. Annual sunshine exceeds 3,600 hours, and 4,000 hours in some places, compared with 1,600–2,400 hours in Japan, making it well suited to solar power. Solar panel efficiency also long hovered in the 10–20% range, but as of 2022 over 20% had become standard, and prices had fallen sharply.

Assuming 1 kW/m² of sunlight, 20% efficiency and 3,600 hours a year, the output would be 6.48 million TWh a year. Even halving this to account for efficiency losses from heat (0.4–0.5% per degree Celsius) and data showing sand reduces efficiency by 19% after one month, it would still be 3.24 million TWh, far exceeding humanity's annual consumption (assumed to be 173,000 TWh).

But the video goes on to say it's not that simple. Based on a 2016 study, manufacturing emissions come to about 20 g of CO₂-equivalent per kWh, which for the whole Sahara would be about 1.5 trillion tons, roughly 37 years' worth of humanity's current emissions. Also, panels absorb more sunlight than sand, warming the surroundings. In a simulation replacing up to 50% of the Sahara, the Earth's average temperature rose by about 0.4°C, some places at high northern latitudes warmed by more than 2°C, and rainfall in the Amazon fell by several hundred millimeters a year. Furthermore, the Sahara spans many countries, and there are concerns about political instability and terrorism (citing the 2016 attack on a gas facility in Algeria). There is also reportedly strong opposition to using local resources for the benefit of other regions. The video concludes that making this happen would require not only technology but also social transformation.

Monticello Dam in Napa County, California, has a giant spillway hole that takes in water once the water level rises above a certain point; it is called the "Glory Hole," after the English name for the morning glory. Because the canyon is narrow and there was no room for other spillway facilities, it was built by connecting it to the channel used to divert the river during construction. At its widest point it is 22 m in diameter, making it one of the largest in the world.

Only one person, a woman in 1997, has reportedly been sucked in. She approached the hole despite people around her calling out to her, clung to the edge for about 20 minutes, and then fell. The video also says, however, that the hole is not unreasonably dangerous. It has functioned only about 25 times in the past 60 years (most recently in 2019), and there is a no-swimming barrier around it. The water flowing over the lip on the day of the accident is estimated to have been less than 10 cm deep, and there are rumors that the woman fell in deliberately.

In the thought experiment, rain is brought down to raise the water level to its maximum, with 1.37 million liters per second pouring in. The streamlined hole makes no sound and looks calm until you get close, but once you enter the point where the water surface becomes a slope, being sucked in is certain. Inside, it narrows from 22 m in diameter to 8.5 m at its narrowest, with a 60-m drop and an 84-degree incline. The world's tallest water slide (51 m high, 60-degree incline) doesn't compare. After that, you would be slammed into the horizontal diversion tunnel and killed. When no water is flowing, local young people use this tunnel to practice skateboarding. In 2019, a cormorant that had been sucked in was reported to have shot out of the spillway exit like a bullet. The water flows into Putah Creek, and the body of the woman from 1997 was also found downstream.

With Atlantis's landing on July 21, 2011, the Space Shuttle ended 30 years of service spanning 135 missions and a total flight distance of about 870 million km. There was no successor, and the United States lost its means of sending astronauts into space. The shuttle consisted of a winged orbiter, two solid rocket boosters and an orange external fuel tank, and its accomplishments include launching and repairing the Hubble Space Telescope and building the International Space Station.

The video gives three direct reasons. The first is cost. In the early 1970s, NASA told Congress it could launch about 50 times a year at $15 million per launch. In reality, however, about 24,000 heat-resistant tiles, each with a different shape, had to be replaced by hand, the engines had to be disassembled and inspected, and the boosters that fell into the sea had to be recovered and cleaned, while the external tank was expendable. The most flights in a year was nine, in 1985, and the average was four to five. One estimate put the cost per flight at about $1.2 billion over the operational period, or $1.5 billion including periods when the fleet was grounded.

The second is safety. The 1986 Challenger disaster was caused by O-rings in the joints of a booster hardening in the cold; the launch was forced through despite engineers' objections, and the shuttle exploded 73 seconds later. In 2003, Columbia broke apart during reentry after falling insulation foam damaged the RCC panels on the leading edge of its wing. The investigation board concluded that foam had been falling off on almost every flight, but management had left it alone as an acceptable risk.

The third is a political decision. In January 2004, President Bush announced the Vision for Space Exploration, setting out a policy of retiring the shuttle once the ISS was completed and redirecting resources to Moon and Mars programs. At the time, the shuttle accounted for about a quarter of NASA's budget.

As the root cause, the video points to the political circumstances of the 1970s. After Apollo's success, the motivation to boost national prestige had faded, and the Vietnam War had strained finances. What NASA originally envisioned was a fully reusable two-stage spacecraft with both stages returning to a runway, but its development budget was slashed, and faced with the choice of "building nothing or building a compromise," it chose the latter. As a result, solid-fuel rockets, which cannot be shut down, were adopted; because they were too large to transport in one piece, they had joints, and those joints caused the Challenger disaster. As launch frequency fell, costs rose and the workforce came under even more pressure, creating a vicious cycle.

The video quotes a line from the Challenger accident report: "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." It adds that the economic side, in the form of budgets, is also reality. Finally, it notes that three of the four RS-25 engines on the SLS rocket for Artemis II, launched on April 2, 2026 (Japan time), had flown on the shuttle, concluding that the shuttle's engines are still flying in space.

The introduction cites the Metropolitan Area Outer Underground Discharge Channel in Kasukabe, Saitama Prefecture (50 m underground), saying humans can already build huge underground facilities. As examples where people have actually lived underground, the video introduces the Derinkuyu underground city in Turkey (deepest point over 85 m, capacity of 20,000 people, used from thousands of years ago until the 1920s, mainly as a shelter) and Coober Pedy in Australia (population around 2,000, more than half of whom live in underground homes called "dugouts").

The biggest advantage is temperature stability. Underground temperatures rise by about 25°C per kilometer, but at depths well shallower than that, a comfortable temperature is maintained year-round. In Coober Pedy, the surface temperature is 2–3°C in winter and over 50°C in summer, while dugouts naturally stay at 19–25°C, and living above ground would mean unrealistic electricity bills. Since 10–15% of the world's energy consumption is said to go toward regulating indoor temperatures, the savings would be significant. Underground spaces are also cited as candidate sites for small modular reactors.

There are many problems, too. Ventilation is difficult (Derinkuyu has more than 50 ventilation shafts), and radon, a radioactive gas released from bedrock, can reach several times surface levels, raising the risk of lung cancer. Humidity encourages mold, which, unlike in dry Coober Pedy, would be a major problem in Japan. One estimate puts construction costs at about twice those of an above-ground high-rise, smoke spreads quickly in a fire, and underground spaces are extremely vulnerable to flooding. The lack of sunlight is also serious: deficiencies of serotonin and vitamin D could lead to depression and bone and sleep disorders.

On the other hand, besides relieving congestion above ground and demonstrating underground farming and small modular reactors, there is the advantage of an environment that cosmic rays have difficulty reaching. Components such as copper used in dark matter detection experiments are manufactured and stored underground to avoid activation by cosmic rays, so an underground city could make them cheaply, potentially contributing to advances in astronomy.

About 200 million years ago, Antarctica formed the supercontinent Gondwana together with South America, Africa, India, Australia and other landmasses, and there were periods when it was warm and covered in forests. After it separated, the Antarctic Circumpolar Current formed and blocked heat from other oceans, and by 30 million years ago at the latest it was heading toward its current state.

Today, you can travel on tourist ships from Argentina, Chile, Australia and New Zealand, mainly to the Antarctic Peninsula (around 63°S, closer to the pole than the northern tip of Greenland), and there are also flight packages to the South Pole. With thorough preparation, returning alive is not difficult.

For going without preparation, the video first takes up the Antarctic Peninsula. In midsummer, the average high is 1°C and the average low −2°C, but winds can reach 40 m/s (with records exceeding 80 m/s), making it feel much colder. In winter, even the high falls below −10°C, and the polar night leaves it pitch dark. The interior is at high elevation because of the ice sheet: the South Pole is about 2,830 m above sea level, and its average winter air pressure of about 675 hPa, owing to the contraction of the atmosphere under extreme cold, rivals that at the summit of Mount Fuji, which is about 900 m higher. The annual average temperature is −49°C, and even the highest temperature ever recorded is only around −12°C. The lowest temperature ever recorded on Earth, −89.2°C, was measured at Vostok Station, about 1,300 km from the South Pole at an elevation of 3,488 m. Satellite observations have also recorded −98°C near the surface, and with wind factored in, it would not be surprising for the perceived temperature to fall below −100°C.

As for the effects on the human body, the video explains that frostbite from constricted blood vessels, oxygen deprivation from low air pressure, and dehydration from the extreme dryness of 0.03% humidity would combine, so frostbite could set in within minutes. According to doctors, the human body is not built to function below −40°C, and a single error of judgment can be fatal. Research indicates that at −50°C, unless you are extremely bundled up, your body temperature will fall below 30°C within a few hours. The video ends by noting that the bodies of people who fell during expeditions in the early 20th century still lie in Antarctica.

Aokigahara, known as the Sea of Trees, is a forest spreading over about 30 km² northwest of Mount Fuji, and it is said to be named for the way the trees, seen from above, seem to undulate like the sea. Lava from the Jōgan eruption, which began in 864, filled a lake called "Senoumi," and its remnants are Lake Shōji and Lake Sai. Trees grew after pioneer plants, but because they cannot root into the hard lava, their roots still snake across the surface.

Its image as a suicide spot is said to stem from Seichō Matsumoto's novel Nami no Tō (The Tower of Waves), published around 1960. Today, exact numbers are not made public, and local authorities speak to visitors. In fiscal 2020, they reportedly spoke to 346 people.

Simply walking the trails is not dangerous, and you can enjoy plants such as moss, ferns and ghost plants, as well as caves formed when the interior of lava flows drained out. Fugaku Wind Cave averages 3°C even in summer. But once you leave the trails, you are surrounded by extremely uneven ground and forest that looks the same in every direction. In 2025, a man gathering mushrooms got lost in just 10 minutes and was rescued by police. The video introduces a study published in 2009. When subjects were made to walk in a German forest and in the Sahara Desert, they could walk relatively straight if they could see the sun or moon, but under cloudy or blindfolded conditions they walked in irregular circles less than 20 m in diameter and on average got no farther than 100 m away. In Aokigahara, the trees make it hard to see the sun or Mount Fuji, and the uneven ground throws off your sense of direction, so this weakness tends to come out.

On the other hand, the video says the idea that "compasses go haywire" is a myth. A compass needle is affected if brought close to magnetic minerals in the lava, but held properly it works well enough. Mobile phones are also less of a problem than before, as more cell towers have been installed. What the video cites as the real dangers are loss of judgment from panic (there are cases of people moving as if to avoid rescue teams) and wild animals such as Asian black bears and deer charging at high speed. The video says the frightening thing about Aokigahara is not something mysterious, but that human weakness is laid bare in nature. It concludes by asking viewers to see the forest as a symbol of vitality, where life took root after the lava.

Present-day Mars has an atmospheric pressure less than 1% of Earth's, an atmosphere made up mostly of carbon dioxide, and a surface bombarded by radiation that living things could not withstand for long. The video traces Mars's appearance by going back in time.

Mars 100 million years ago was not much different from today. However, Olympus Mons, over 20 km high, is thought to have still had small-scale activity. Also, perchlorates in the soil, especially calcium perchlorate, can lower the freezing point of water to about −75°C, so salty water may have existed for short periods. One study reportedly found minerals in Martian meteorites that had been altered by liquid water within the last 170 million years, so you might witness water as fleeting as a mirage.

Two to three billion years ago, atmospheric pressure was about the same as today, but water that had lain dormant underground burst out through volcanic activity, causing catastrophic floods. The flow rate is said to have reached up to 1 billion m³ per second, more than 3,000 times that of the Amazon River (maximum about 300,000 m³).

Between 3.7 and 4.3 billion years ago, an ocean is thought to have covered nearly the entire northern hemisphere, with depths of up to more than 1.6 km. Some research suggests there was an atmosphere of at least 0.5 bar 4 billion years ago, so there may have been three blue planets: Venus, Earth and Mars. However, over hundreds of millions of years, particles from the solar wind gave energy to molecules in the atmosphere and let them escape into space; as a result, the atmosphere thinned and the oceans evaporated. Water vapor was broken down by ultraviolet light, the light hydrogen escaped into space, and the remaining oxygen reacted with iron to form red rust. The change from blue to red is said to have taken place between about 3.9 and 3.0 billion years ago.

The difference from Earth is the magnetic field. Many scientists believe that sustaining a magnetic field requires a liquid metal core and convection driven by temperature differences. On Earth, as the solid inner core grows, lighter components are pushed out into the outer core, generating buoyancy-driven convection. Mars is about half Earth's diameter and about a tenth of its mass, so it cools easily, and a liquid layer covering the core like a blanket is thought to have reduced the temperature difference between inside and outside, so its magnetic field stopped about 3.9 billion years ago. The video says Earth, too, is thought to lose its water several billion years from now as the Sun expands.

The video begins by clarifying that a black hole is not "a hole in space." When a star with roughly eight or more times the mass of the Sun runs out of fuel, its iron core collapses and triggers a supernova, and the remaining core can become a black hole. Black holes can also form from collisions between neutron stars. There is also a theory of primordial black holes formed directly right after the Big Bang, but none have yet been found.

Escape velocity is about 11 km/s for Earth and about 600 km/s for the Sun; for a black hole, it exceeds the speed of light. The black holes found so far are stellar black holes ranging from a few to about 100 times the mass of the Sun, and supermassive black holes of hundreds of thousands of times or more; nothing in between has been definitively found. Nothing can return from inside the event horizon. For a non-rotating black hole, its radius is called the Schwarzschild radius, which is about 3 km for one solar mass. The video explains this as the Sun's mass fitting within an area centered on Tokyo Station and extending roughly to Tokyo Tower or the Ryōgoku Kokugikan. The horizon is not a surface, and you most likely wouldn't feel anything as you crossed it.

If the Sun were replaced with a black hole of the same mass, the planets' orbits would not change. But if you approached a stellar black hole of about five solar masses feet first, at 20 km from the center (5 km from the horizon), a difference of 1 mm would produce tidal forces 17,000 times Earth's gravity, and your body would be stretched (spaghettification). With a supermassive black hole, by contrast, the tidal forces are slight and you could cross the horizon without incident. Inside, according to the description given by general relativity, moving toward the center becomes as unavoidable as the passage of time, and you are predicted to eventually reach the singularity.

At the singularity, density becomes infinite in the calculations, but many scientists believe this simply means general relativity has gone beyond its range of applicability. Candidates presented include loop quantum gravity, which holds that spacetime has a smallest unit (some physicists think what lies beyond the singularity connects to a white hole), and the fuzzball hypothesis from string theory. However, none have observational support.

In the history of observations, an X-ray source in Cygnus was found in 1964, and in 1971 the wobble of its companion star revealed the existence of an invisible, massive object. In 2019, the Event Horizon Telescope imaged the supermassive black hole at the center of M87, about 6.5 billion times the mass of the Sun (Schwarzschild radius: 18 billion km). The nearest, Gaia BH1, is about 1,560 light-years away, has 9–10 times the mass of the Sun, and quietly orbits with a Sun-like star at roughly the Earth-Sun distance. It is hard to explain how such a tidy binary could survive a supernova, and the video suggests there may still be much humanity doesn't understand about how black holes form and evolve. The James Webb Space Telescope (JWST) has found disproportionately large supermassive black holes in galaxies only about 700 million years after the universe's birth, forcing a revision of the conventional hypothesis that they grew alongside their galaxies.

Finally, Hawking radiation is introduced. The time it takes to evaporate is predicted to be about 10⁶⁷ years for a stellar black hole and about 10¹⁰⁰ years for a supermassive one. The video says that in the distant future when the stars are gone, black holes, from which it is theoretically possible to extract energy by throwing objects into them, may become life's last refuge.

This episode, without a story, introduces 24 planets out of more than 6,000 confirmed planets (with more than 8,000 candidates). The video says that from these, it becomes clear our solar system is not the cosmic standard.

The first one featured is Poltergeist (PSR B1257+12 c), one of the earliest exoplanets, found in 1992 around the pulsar "Lich." It was discovered from deviations in the regular signal of the pulsar, which rotates about 160 times per second. Next is the nearest, Proxima Centauri b (4.2 light-years away). It was found in the habitable zone in 2016, but it may be exposed to 30 times Earth's extreme ultraviolet radiation and 250 times its X-rays. LHS 1140 b is estimated to be 9–19% water by mass and may be an "eyeball" world where only the dayside remains unfrozen. Teegarden's Star b is nearly the same size and mass as Earth and ranks among the highest on the Earth Similarity Index. Kepler-37b is about 0.3 times Earth's diameter, and the video describes it as the smallest exoplanet as of 2025.

Examples of extreme environments follow. 55 Cancri e has a surface covered in lava, and its dayside may exceed 3,000°C. The former "diamond planet" theory has now reportedly been rejected. Among hot Jupiters, HD 189733 b is presented as a blue planet where silicate glass rains sideways in 2,000 m/s winds, WASP-76b as a planet where iron vaporizes into clouds and falls as iron rain, and TrES-2b as a black planet that reflects less light than coal for reasons that can't be explained. In contrast for density, WASP-127b is 0.1 g per cubic centimeter, comparable to Styrofoam, while TOI-4603b is about 14 g, denser than lead. WASP-12b is stretched into a rugby-ball shape by its star's gravity and is estimated to be swallowed in 3 to 5 million years. Gliese 436b trails a tail of hydrogen like a comet.

Some planets have astronomical significance. 51 Pegasi b was the first planet found around a main-sequence star and overturned the theory of the time that gas planets could not form very close to their stars. GJ 1214b is considered a representative "mini-Neptune," a type not found in our solar system. Gliese 900 b takes more than 1.26 million Earth years to orbit and was discovered through citizen science. Kepler-1625b has an exomoon candidate, and the free-floating planet PSO J318.5−22 has no host star. In addition, Kepler-16b is a "Tatooine" orbiting a binary star, and HD 100546 b is the largest exoplanet according to Guinness World Records. J1407b was thought to have giant rings, but its very existence has come into question.

The last one featured is WD 1202−232 b, directly imaged by JWST. It orbits a white dwarf on an orbit similar to those Jupiter and Saturn will have after the Sun becomes a white dwarf, and the video says Jupiter and Saturn may survive even after the Sun's life ends.

The closing episode deals with the origin of the universe. In 1917, Einstein wrote a paper assuming a static universe, but in 1929 Hubble showed that it is expanding. The Big Bang theory holds that going back in time, the universe becomes extremely hot and dense, and its age is put at about 13.8 billion years.

The video emphasizes, however, that the moment of birth is not understood. As an analogy, it notes that if you went back in time using only the rule that children grow bigger every year, you would reach the mistaken conclusion that "people are born from nothing." It is unknown whether general relativity and the Standard Model hold in the early universe, and nothing at all is known about the time before 10⁻⁴³ seconds.

The rest is explained in chronological order. In the grand unification epoch, the three forces other than gravity were one. In the subsequent inflation, the universe expanded by a factor of 10²⁶ or more (10⁴⁰ by one theory) in an extremely short time, and today's observable universe became about 10 cm across. The reason is unknown, but based on the characteristics of the cosmic background radiation, it is considered highly likely that something like this occurred. After the electroweak epoch, the four forces separated in the quark epoch. Matter and antimatter annihilated each other, but because matter outnumbered antimatter by about 1 in 2 billion, the present universe remained. The reason for this is also unknown. After the hadron epoch (up to about 1 second) and the lepton epoch (up to about 3 minutes), Big Bang nucleosynthesis produced the nuclei of hydrogen and helium, but fusion stopped after about 20 minutes. About 380,000 years later, when the universe had cooled to about 3,000°C and atoms formed, light could travel in straight lines (recombination), and this became the cosmic background radiation. Its uniformity is considered strong evidence for inflation.

During the dark ages, between about 10 million and 17 million years after the birth of the universe, temperatures were 0–100°C, and liquid water could have existed if there had been pressure. The video also touches on the panspermia hypothesis, which holds that life arose at that time and reached Earth mixed in with dust. Between 100 million and 500 million years later, galaxies formed along the web of dark matter, and first-generation stars hundreds of times the mass of the Sun scattered heavy elements in supernova explosions. The Sun is said to be a third-generation star that formed about 9 billion years after the universe's birth. Around the same time, the universe's expansion began to accelerate. Dark energy was proposed as the cause, but its nature is unknown.

The leading scenario for the future is the Big Freeze: accelerating expansion continues, stars burn out in 1 trillion to 100 trillion years, and after 10¹⁰⁰ years only dark matter and a small number of electrons drift about. The possibilities of a Big Rip or Big Crunch also remain. The video concludes that everything depends on dark matter, dark energy and the laws of the universe, which are not yet understood, and that the quest to learn how the world began and where it is headed continues.