What If? Serious Scientific Answers To Absurd Hypothetical Questions

What are the big ideas?

1. The Power of Imagination in Science: This book offers a unique perspective on the role of imagination in scientific exploration and discovery. For instance, it suggests creating hypothetical scenarios, such as draining the oceans or experiencing a sunless Earth, to better understand complex phenomena. By using humor and storytelling to illustrate these ideas, the author encourages readers to think creatively and challenge their assumptions about the world around them.
2. The Importance of Perspective in Understanding Complex Concepts: The book demonstrates how adopting different perspectives can help clarify complex scientific concepts. For example, it explores the concept of time by discussing various ways it can be measured and experienced, including the length of a sunset on different planets or the passing of generations. By using humor to illustrate these ideas, the author fosters a deeper understanding of these concepts.
3. The Role of Humor in Exploring Complex Scientific Topics: This book uses humor as a powerful tool for engaging readers in scientific topics that can be daunting or confusing. For instance, it explores complex phenomena like lightening all its water drops at once or the loneliest human experiences in history by using humorous narratives and jokes. These storytelling techniques make the otherwise dry scientific concepts more accessible to a broader audience.
4. The Impact of Contextual Understanding on Complex Science: This book highlights how understanding the contexts behind complex scientific phenomena can lead to a deeper comprehension of these topics. For example, it examines the concept of time from various perspectives, such as measuring it with clocks and pendulums or experiencing it through historical events. By using humor to clarify these ideas, the author encourages readers to delve deeper into scientific concepts, fostering a stronger foundation for future learning.
5. The Power of Storytelling in Popularizing Complex Science: This book illustrates how using storytelling techniques can help make complex scientific topics more accessible and enjoyable for broader audiences. For instance, it uses humor and anecdotes to discuss various scientific phenomena like draining the oceans or experiencing a sunset on different planets. By employing such storytelling methods, the author encourages readers to engage with these complex ideas in a more relaxed and entertaining manner, which ultimately fosters a stronger foundation for further exploration into these topics.

Chapter Summaries

Introduction

Takeaways

• The author, Randall Munroe, answers hypothetical questions through his website and in this book.
• Munroe has a background in physics and robotics, but now draws webcomics full-time.
• He uses math to answer questions, including one from his childhood about the number of soft and hard things in their house.
• The author finds that trying to answer seemingly stupid questions can lead to interesting discoveries.
• Munroe shares his favorite answers from his website and new answers in this book.

Quotes

“They say there are no stupid questions. That’s obviously wrong; I think my question about hard and soft things, for example, is pretty stupid. But it turns out that trying to thoroughly answer a stupid question can take you to some pretty interesting places.”

“I still don’t know whether there are more hard or soft things in the world,”

Global Windstorm

Takeaways

• If Earth stopped spinning and the atmosphere retained its velocity, nearly everyone on Earth would die due to supersonic winds.
• The equator would experience the highest winds, while those near the poles would still be devastating.
• Human structures would be destroyed, and even well-anchored bunkers wouldn't be safe if neighbors' bunkers were not.
• Some people below ground, such as those in deep basements or subway tunnels, might survive.
• The wind blast would lead to extreme temperature increases and global thunderstorms over land, as well as churned-up oceans with massive waves and storm surges.
• The Earth's rotation stopping would result in constant sunlight on one side and darkness on the other, causing extreme temperatures and convection on the day side.
• Venus serves as a comparison for this scenario due to its tidal locking, but the Moon's tides would act to reverse the damage if Earth stopped rotating.
• The Moon's gravity would gradually tug Earth back into rotation.

Quotes

“A. Nearly everyone would die. Then things would get interesting.”

Relativistic Baseball

Takeaways

• A baseball pitched at 90% the speed of light would result in "a lot of things" happening quickly and ending poorly for both the batter and pitcher
• The ball would be moving so fast that everything else would appear stationary, including air molecules
• Ideas of aerodynamics wouldn't apply as the ball would smack into air molecules and cause fusion, releasing gamma rays and debris
• This gamma ray and debris bubble would expand outward, tearing apart molecules in the air and creating an expanding bubble of incandescent plasma
• The ball would arrive at home plate as a bullet-shaped cloud of expanding plasma, carrying the batter, plate, and catcher backward through the backstop and surrounding neighborhood in the first microsecond
• Everything within roughly a mile of the park would be leveled, causing a firestorm and leaving a sizable crater behind
• Major League Baseball Rule 6.08(b) suggests that the batter would be considered "hit by pitch" and eligible to advance to first base.

Spent Fuel Pool

Takeaways

• A typical spent nuclear fuel pool is used for radiation shielding and cooling, with spent fuel stored at the bottom for decades.
• Swimming in a spent fuel pool could allow you to survive treading water for 10-40 hours before blacking out from fatigue and drowning.
• The most highly radioactive fuel rods are those recently removed from a reactor, and contact with them could be fatal.
• Outside the danger zone, swimming in a spent fuel pool may provide lower radiation exposure than walking on the street due to shielding effects of water.
• Human divers service spent fuel pools regularly, but accidents like encountering radioactive debris can occur, emphasizing the need for caution.

Quotes

“Q. What if I took a swim in a typical spent nuclear fuel pool? Would I need to dive to actually experience a fatal amount of radiation? How long could I stay safely at the surface? —Jonathan Bastien-Filiatrault A. Assuming you’re a reasonably good swimmer, you could probably survive treading water anywhere from 10 to 40 hours. At that point, you would black out from fatigue and drown. This is also true for a pool without nuclear fuel in the bottom.”

“You may actually receive a lower dose of radiation treading water in a spent fuel pool than walking around on the street.”

“Remember: I am a cartoonist. If you follow my advice on safety around nuclear materials, you probably deserve whatever happens to you.”

“That’s if everything goes as planned.”

“I got in touch with a friend of mine who works at a research reactor, and asked him what he thought would happen to someone who tried to swim in their radiation containment pool. “In our reactor?” He thought about it for a moment. “You’d die pretty quickly, before reaching the water, from gunshot wounds.”

New York–Style Time Machine

Takeaways

• Times Square 1000 years ago was part of a landscape of rolling hills, marshes, woodlands, lakes, and rivers, with large animals such as wolves, mountain lions, chestnut trees, and no earthworms.
• The Earth 10,000 years ago was emerging from an ice age and had a different climate than today.
• A billion years ago, the continents were joined into one supercontinent called Rodinia, and blue-green algae caused the oxygen catastrophe which led to the evolution of multicellular organisms.
• In a million years, humans may no longer exist, leaving behind only plastic waste as a lasting relic of civilization.
• The Sun will gradually brighten, causing Earth's climate to become uninhabitable in a billion years and eventually being consumed by the Sun.
• Our descendants may one day live on planets formed from the dust clouds created when the Earth is incinerated.

Quotes

“To see what Times Square looked like before a city was there, we turn to a remarkable project called Welikia, which grew out of a smaller project called Mannahatta. The Welikia project has produced a detailed ecological map of the landscape in New York City at the time of the arrival of Europeans. The interactive map, available online at welikia.org, is a fantastic snapshot of a different New York. In 1609, the island of Manhattan was part of a landscape of rolling hills, marshes, woodlands, lakes, and rivers.”

“There were no earthworms in New England when the European colonists arrived.”

“Blue-green algae, or cyanobacteria, were the first photosynthesizers. They breathed in carbon dioxide and breathed out oxygen. Oxygen is a volatile gas; it causes iron to rust (oxidation) and wood to burn (vigorous oxidation). When cyanobacteria first appeared, the oxygen they breathed out was toxic to nearly all other forms of life. The resulting extinction is called the oxygen catastrophe. After the cyanobacteria pumped Earth’s atmosphere and water full of toxic oxygen, creatures evolved that took advantage of the gas’s volatile nature to enable new biological processes. We are the descendants of those first oxygen-breathers. Many details of this history remain uncertain; the world of a billion years ago is difficult to reconstruct.”

“Maybe civilization will collapse, we’ll all succumb to disease and famine, and the last of us will be eaten by cats. Maybe we’ll all be killed by nanobots hours after you read this sentence. There’s no way to know.”

“Without us, Earth’s geology will grind on. Winds and rain and blowing sand will dissolve and bury the artifacts of our civilization. Human-caused climate change will probably delay the start of the next glaciation, but we haven’t ended the cycle of ice ages. Eventually, the glaciers will advance again. A million years from now, few human artifacts will remain.”

“If humans escape the solar system and outlive the Sun, our descendants may someday live on one of these planets. Atoms from Times Square, cycled through the heart of the Sun, will form our new bodies. One day, either we will all be dead, or we will all be New Yorkers.”

“I mean, I guess it's just me who argues that; but I'm very vocal.”

Soul Mates

Takeaways

• The concept of having a random, unique soul mate raises questions and issues.
• Most of our potential soul mates would be dead or inaccessible due to age, gender, culture, language, and other demographics.
• The odds of finding your soul mate through chance encounters are extremely low.
• Society might try to increase opportunities for eye contact to find soul mates, but it may not be feasible or effective for everyone.
• A world with random soul mates would result in a significant number of people being unable to find their soul mates and experiencing loneliness.
• Some people might fake having found their soul mate to fit in with others.

Quotes

“As Tim Minchin put it in his song “If I Didn’t Have You”: Your love is one in a million; You couldn’t buy it at any price. But of the 9.999 hundred thousand other loves, Statistically, some of them would be equally nice.”

“For starters, would your soul mate even still be alive? A hundred billion or so humans have ever lived, but only seven billion are alive now (which gives the human condition a 93 percent mortality rate). If we were all paired up at random, 90 percent of our soul mates would be long dead.”

“But what about gender and sexual orientation? And culture? And language? We could keep using demographics to try to narrow things down further, but we would be drifting away from the idea of a random soulmate. In our scenario, you wouldn’t know anything about who your soulmate was until you looked into their eyes. Everybody would have only one orientation: towards their soulmate.”

“Given all the stress and pressure, some people would fake it. They’d want to join the club, so they’d get together with another lonely person and stage a fake soul mate encounter. They’d marry, hide their relationship problems, and struggle to present a happy face to their friends and family.”

“A world of random soul mates would be a lonely one. Let’s hope that’s not what we live in.”

Laser Pointer

Takeaways

• A laser pointer cannot change the Moon's color if everyone aims it at the Moon at the same time because sunlight is much brighter than the laser light.
• With a 1-watt green laser, everyone could collectively illuminate about half of the Moon's surface with more light than moonlight, but it would not be visible from Earth or have any effect on the dark side of the Moon.
• To effectively illuminate the entire Moon's surface, using a high-performance flashlight, Nightsun, IMAX projector array, or even a megawatt laser is not feasible due to insufficient power and other practical limitations.
• A megawatt laser mounted on every square meter of Asia's surface would require all of Earth's oil reserves in just two minutes and make the Moon as bright as the midmorning sun, potentially causing catastrophic consequences for both the Moon and Earth.
• Laser ablation, a promising method for spacecraft propulsion, could be achieved by using lasers to vaporize lunar bedrock, creating a rocket engine effect that would push the Moon away from Earth over months or years, potentially leading to unpredictable orbital perturbations or collisions with other planets.

Quotes

“A 1-watt laser is an extremely dangerous thing. It’s not just powerful enough to blind you—it’s capable of burning skin and setting things on fire. Obviously, they’re not legal for consumer purchase in the US. Just kidding! You can pick one up for $300. Just do a search for “1-watt handheld laser.” So, suppose we spend the $2 trillion to buy 1-watt green lasers for everyone. (Memo to presidential candidates: This policy would win my vote.)”

Periodic Wall of the Elements

Takeaways

• Building a periodic table out of cube-shaped bricks made of each element is an intriguing concept, but some elements pose significant risks.
• Elements like hydrogen and helium rise and disperse, while lithium tarnishes and beryllium is toxic. Fluorine is extremely reactive and corrosive.
• Phosphorus, especially white phosphorus, ignites on contact with air and produces toxic smoke. Sulfur catches fire when exposed to fluorine gas.
• The third row contains toxic arsenic, which releases large amounts of arsenic trioxide when burned. Gallium melts and soaks into aluminum, disrupting its structure.
• Row four includes the unstable astatine, which turns into a column of superheated gas and causes third-degree burns, building demolition, and radioactive fallout.
• The fifth row contains technetium-99, our first radioactive brick, which can kill with a substantial dose even if it's not lethal in an experiment.
• Row six includes several radioactive elements like promethium, polonium, astatine, and radon, with astatine being the most dangerous due to its instability and short half-life.
• The seventh row contains transuranic elements that don't exist for long because they decay radioactively. A cube of these highest-numbered elements would release a tremendous amount of energy in a nuclear explosion-like event, causing widespread devastation.
• Collecting all elements is not recommended due to the significant risks associated with many of them.

Quotes

“Do not build the seventh row.”

“We don’t know what astatine looks like, because, as Lowe put it, “that stuff just doesn’t want to exist.” It’s so radioactive (with a half-life measured in hours) that any large piece of it would be quickly vaporized by its own heat. Chemists suspect that it has a black surface, but no one really knows. There’s no material safety data sheet for astatine. If there were, it would just be the word “NO” scrawled over and over in charred blood.”

“The explosion would be just the right size to maximize the amount of paperwork your lab would face. If the explosion were smaller, you could potentially cover it up. If it were larger, there would be no one left in the city to submit paperwork to.”

“Think of the elements as dangerous, radioactive, short-lived Pokémon.”

Everybody Jump

Takeaways

• The entire Earth's population jumping at once has no significant effect on the planet.
• The energy released from everyone jumping creates a loud roar and slight pressure wave that dissipates quickly.
• The cell networks collapse under the unprecedented load, leaving everyone without communication.
• Rhode Island's infrastructure, including airports, light rail system, and cars, becomes overwhelmed and unable to support the crowd.
• The edge of the crowd spreads outward, resulting in chaos, violence, and a graveyard of billions.
• Survivors struggle to build a new civilization on the ruins of the old.
• Earth's orbit remains unaffected by the jump.

A Mole of Moles

Takeaways

• A mole is a unit of measurement representing 6.022 × 1023 items, often used for counting molecules.
• Moles are also small burrowing mammals with various species and sizes.
• One mole of moles would weigh over half the mass of Earth's moon (4.52 × 10²² kg).
• The volume occupied by one mole of moles is approximately 3562 km³, equivalent to a sphere with a radius of 2210 kilometers or a cube with sides of 2213 miles.
• A pile of moles on Earth would smother and destroy most life due to its massive size and weight.
• In interplanetary space, moles would form a spherical planet slightly larger than the moon, with low surface gravity and temperatures.
• The mole planet's interior would lack microorganisms for decomposition due to extreme pressure and lack of oxygen, leading to self-limiting anaerobic decomposition.
• Eventually, the mole planet would freeze from the inside out, forming exotic forms of ice and cooling down over centuries or millennia.
• To obtain a mole of moles, consider building a spaceship for interplanetary exploration and colonization instead.

Quotes

“But this is where it gets weird. The mole planet would be a giant sphere of meat.”

Hair Dryer

Takeaways

• A hair dryer draws 1875 watts of power and will generate heat if used in an airtight box.
• If a device is using power, it will produce heat. An unused charger is not using significant electricity.
• Heat flow analysis provides a simple rule of thumb for determining if a device is using power: if it's warm to the touch, it's using power.
• The equilibrium temperature inside an airtight box with a hair dryer will depend on the box's material and thickness.
• Increasing the power output of a hair dryer in an airtight box will result in higher temperatures and potential damage or destruction to the box and surrounding area.
• An indestructible hair dryer could potentially generate enough heat to melt various materials and even start a fire if used in an airtight box.
• The temperature inside an airtight box with a hair dryer will continue to rise until it reaches equilibrium with the surrounding environment or the hair dryer is destroyed.
• The potential danger of a hair dryer in an airtight box increases with the power output and duration of use.
• A high-power hair dryer could potentially be used as a destructive device if used in an airtight container, generating significant heat and potentially causing damage to surrounding areas or even the planet.

Quotes

“For a small smartphone charger, if it’s not warm to the touch, it’s using less than a penny a year. This is true of almost any powered device.1”

“The official record for the fastest manmade object is the Helios 2 probe, which reached about 70 km/s in a close swing around the Sun. But it’s possible the actual holder of that title is a two-ton metal manhole cover. The cover sat atop a shaft at an underground nuclear test site operated by Los Alamos as part of Operation Plumbbob. When the 1-kiloton nuke went off below, the facility effectively became a nuclear potato cannon, giving the cap a gigantic kick. A high-speed camera trained on the lid caught only one frame of it moving upward before it vanished—which means it was moving at a minimum of 66 km/s. The cap was never found. Now, 66 km/s is about six times escape velocity, but contrary to common speculation, it’s unlikely the cap ever reached space. Newton’s impact depth approximation suggests that it was either destroyed completely by impact with the air or slowed and fell back to Earth. When we turn it back on, our reactivated hair dryer box, bobbing in lake water, undergoes a similar process. The heated steam below it expands outward, and as the box rises into the air, the entire surface of the lake turns to steam. The steam, heated to a plasma by the flood of radiation, accelerates the box faster and faster. Photo courtesy of Commander Hadfield Rather than slam into the atmosphere like the manhole cover, the box flies through a bubble of expanding plasma that offers little resistance. It exits the atmosphere and continues away, slowly fading from second sun to dim star. Much of the Northwest Territories is burning, but the Earth has survived.”

The Last Human Light

Takeaways

• Most artificial light sources would go out within days or months due to power grid failures.
• Some power sources like geothermal plants, wind turbines, and hydroelectric dams can run for years without human intervention but will eventually fail.
• Batteries gradually discharge and have limited shelf life.
• Nuclear reactors could continue running indefinitely if fuel doesn't deplete but would shut down due to external power loss or control system failure.
• Spacecraft might be the longest-lasting human artifacts, but most won't have lights and will eventually fail due to other reasons.
• Solar panels can last a long time when kept free of dust and debris.
• Cherenkov radiation from radioactive waste products can cause a blue glow that may last for centuries in deep concrete vaults.

Quotes

“In the Clarendon Library at Oxford University sits a battery-powered bell that has been ringing since the year 1840. The bell “rings” so quietly it’s almost inaudible, using only a tiny amount of charge with every motion of the clapper. Nobody knows exactly what kind of batteries it uses because nobody wants to take it apart to figure it out.”

“The Mars rover Curiosity, for example, is powered by the heat from a chunk of plutonium it carries in a container on the end of a stick.”

“We keep trying to make our units of measurement make sense. But the truth is that the world is an absurd place; why not embrace it? It’s true, unit conversion errors have caused us to lose space probes once in a while. But isn’t that a small price to pay for silliness?”

Machine-Gun Jetpack

Takeaways

• To build a jetpack using downward-firing machine guns, it's necessary to calculate the thrust-to-weight ratio of the specific gun model.
• The AK-47 has a thrust-to-weight ratio of around 2 and could potentially take off but can only lift a minimal weight.
• Multiple guns increase thrust proportionally, making the weight of the passenger irrelevant with a sufficient number of guns.
• However, ammunition limits the practical application as fuel adds weight.
• Optimal craft would consist of a large number of AK-47s carrying 250 rounds each.
• Heavier machine guns like MG-42 and GAU-8 Avenger have higher thrust-to-weight ratios but also more ammunition requirements, making them less practical for jetpack applications.
• The most effective engine for a jetpack is the Gryazev-Shipunov GSh-6-30 with an extremely high thrust-to-weight ratio and acceleration, but it requires extensive engineering solutions to handle the intense force and heat.

Quotes

“Q. Is it possible to build a jetpack using downward-firing machine guns? —Rob B A. I WAS SORT OF surprised to find that the answer was yes! But to really do it right, you’ll want to talk to the Russians.”

“Actually, what I’m confused about is how.”

Rising Steadily

Takeaways

• If rising steadily at 1 foot per second, you would die around the seven-hour mark due to lack of oxygen in the Death Zone.
• At two hours and two kilometers, the temperature would drop below freezing and frostbite could be a concern.
• Air pressure changes rapidly with height, causing ears to pop and making it harder to breathe at higher altitudes.
• Wearing appropriate clothing can help extend survival time in cold temperatures.
• Human bodies can handle small air pressure changes but struggle in the Death Zone where oxygen content is too low to support life.

Orbital Submarine

Takeaways

• A nuclear submarine's hull is strong enough to contain air, but the crew would face a significant problem of running out of oxygen in space.
• Nuclear submarines extract oxygen from water for survival, which is not available in space. They carry reserves but would eventually run out.
• Space is not as thermally conductive as water, so individual molecules have high average kinetic energy but don't affect temperature much. Humans lose heat faster in space due to lack of convection and radiation.
• A submarine would need to slow down and hit the atmosphere to get out of orbit, but its rockets are not useful for that purpose.
• If a nuclear submarine were to attempt de-orbiting using its ballistic missiles, it could survive the speed change required, but it would tumble and break up in the air, making survival unlikely.
• Disabling the detonators on the missiles is crucial before attempting any maneuvers in space.

Quotes

“the ocean is colder than space.”

Short-Answer Section

Takeaways

• A printer capable of producing one page per minute of full-color high-quality prints could generate $200 million dollars a year, but this amount is insufficient to make a noticeable impact on the world economy.
• Setting off a nuclear bomb in a hurricane is not advisable as it will not immediately vaporize the storm cell and may have disastrous consequences.
• A house with a footprint of 1500 square feet and gutters 5 meters off the ground can generate less than a watt of power from rainfall, making it unlikely to offset the cost of turbine generators.
• It would take a name longer than the estimated number of stars in the universe (approximately 21 quintillion quintillion) to give each star a unique one-word name if we use only pronounceable letter combinations.
• Reaching a speed of 200 meters per second on a bicycle, necessary for skin warming similar to spacecraft during reentry, is beyond the capabilities of human-powered vehicles due to the increasing drag at higher speeds.
• The Internet can be estimated to occupy less than an oil tanker's worth of storage based on the amount of hard drive production per second.
• Attempting to use a boomerang with C4 attached as a weapon may not yield significant tactical advantages due to aerodynamic limitations and safety concerns.

Quotes

“It makes me happy that an arm of the US government has, in some official capacity, issued an opinion on the subject of firing nuclear missiles at hurricanes.”

“I like doing math that involves measuring the lengths of numbers written out on the page (which is really just a way of loosely estimating log10x). It works, but it feels so wrong.”

Lightning

Takeaways

• Roll an imaginary 60-meter sphere across the landscape to identify potential lightning targets.
• Places where the surface makes contact with the sphere are potential lightning targets.
• Standing near a tall object does not make you safe from lightning; the current may travel through the object and into the ground, posing a risk to those nearby.
• Water is conductive and increases the danger of being struck by lightning.
• Boats without cabins or lightning protection systems are as unsafe as being on a golf course.
• Bullets do not affect the path of a lightning bolt.
• Copper, a conductor found in bullets, may allow electricity to take a shortcut through them.
• The bullet may handle the electrical current well due to its speed.
• Flashing the BIOS during a thunderstorm increases the risk of being struck by lightning.

Quotes

“Do not try any of this at home. The author of this book is an Internet cartoonist, not a health or safety expert. He likes it when things catch fire or explode, which means he does not have your best interests in mind. The publisher and the author disclaim responsibility for any adverse effects resulting, directly or indirectly, from information contained in this book.”

Human Computer

Takeaways

• Humans and computers do different types of thinking, making direct comparison challenging.
• Humans can outperform computers in tasks like interpreting images or understanding context.
• According to computer scientist Hans Moravec, a human running through computer chip benchmark calculations by hand is equivalent to one full instruction every minute and a half.
• A midrange mobile phone could carry out these calculations about 70 times faster than the entire world population, while a new high-end desktop PC chip could do so 1500 times faster.
• The first typical desktop computer surpassed the combined processing power of humanity in 1994.
• The complexity of brains is more sophisticated than any supercomputer but measuring human computing power is difficult and comparing methods may not be fair.
• Estimates suggest human brains clock in at about 30,000 MIPS and Earth's digital complexity overtook its human neurological complexity around 2004.
• Ants have a brain complexity similar to humans, indicating we've caught up to ants but not computers in terms of complexity.
• We should not worry about when computers will catch up with us in complexity as humans seem more likely to still be around in a million years than computers.

Quotes

“To test this theory, I sent this picture to my mother and asked her what she thought had happened. She immediately replied,2 “The kid knocked over the vase and the cat is investigating.” She cleverly rejected alternate hypotheses, including: The cat knocked over the vase. The cat jumped out of the vase at the kid. The kid was being chased by the cat and tried to climb up the dresser with a rope to escape. There’s a wild cat in the house, and someone threw a vase at it. The cat was mummified in the vase, but arose when the kid touched it with a magic rope. The rope holding the vase broke and the cat is trying to put it back together. The vase exploded, attracting a child and a cat. The child put on the hat for protection from future explosions. The kid and cat are running around trying to catch a snake. The kid finally caught it and tied a knot in it.”

“Sure, we seem like we’ve taken over the planet, but if I had to bet on which one of us would still be around in a million years—primates, computers, or ants—I know who I’d pick.”

“Red Delicious apples, whose misleading name is a travesty.”

Little Planet

Takeaways

• The Little Prince, a children's book by Antoine de Saint-Exupéry, imagines a tiny planet-asteroid with gravity, air, and other properties.
• Such an asteroid with Earthlike gravity (500 million tons) would result in tidal forces and unusual escape velocity (about 5 m/s).
• Escape velocity doesn't depend on direction; one might leave the asteroid by running horizontally and jumping off a ramp.
• Orbits around such an asteroid could be chaotic due to tidal forces, making space transportation projects challenging.
• The Little Prince story has been criticized for its depiction of the protagonist's interactions with other characters.
• The term "escape speed" should correctly be called "escape velocity," emphasizing it has no direction.

Steak Drop

Takeaways

• A steak needs to reach an altitude of about 30-50 kilometers for the air to start slowing it down, and then it will steadily drop towards the ground at terminal velocity.
• For much of the fall, the steak will be subjected to subzero temperatures and hurricane-force winds.
• The steak will not be cooked by the fall alone, even if it reaches supersonic or hypersonic speeds.
• Dropping a steak from extremely high altitudes presents challenges related to heating and structural integrity due to charring.
• Pittsburgh Rare steaks are allegedly cooked by searing the outside while leaving the inside raw on glowing metal surfaces coming out of foundries.

Quotes

“As far as I know, this steak question originally came up in a lengthy 4chan thread, which quickly disintegrated into poorly informed physics tirades intermixed with homophobic slurs. There was no clear conclusion.”

“At supersonic and hypersonic speeds, a shockwave forms around the steak that helps protect it from the faster and faster winds. The exact characteristics of this shock front—and thus the mechanical stress on the steak—depend on how an uncooked 8-ounce filet tumbles at hypersonic speeds. I searched the literature, but was unable to find any research on this.”

Hockey Puck

Takeaways

• A puck cannot knock a goalie backward into the net by human means due to their significant weight difference.
• Goalies can brace hard against the ice and stop quickly, making it difficult for a puck to knock them back.
• Estimates suggest that a 165-gram puck would need to move between Mach 2 and Mach 8 to knock a goalie back.
• Firing a puck at Mach 8 is technically possible but not practical due to the rapid compression and heating of air ahead of it, causing it to melt or char, and the significant air resistance slowing it down quickly.
• A puck moving at Mach 8 would likely burst apart on impact with minimal force, similar to a ripe tomato hitting a cake when thrown hard.

Quotes

“Hockey players can also brace pretty hard against the ice. A player skating at full speed can stop in the space of a few meters, which means the force they’re exerting on the ice is pretty substantial. (It also suggests that if you started to slowly rotate a hockey rink, it could tilt up to 50 degrees before the players would all slide to one end. Clearly, experiments are needed to confirm this.)”

Common Cold

Takeaways

• The common cold is caused by various viruses, primarily rhinoviruses.
• Rhinoviruses infect cells in the nose and throat, reproduce, and are then destroyed by the immune system.
• After infection, individuals develop immunity to that particular strain of rhinovirus for years.
• A global quarantine to eliminate the common cold would have significant economic and practical consequences.
• The world's food reserves may not be enough for a prolonged quarantine, and it may not be feasible for everyone to maintain a sufficient separation from one another.
• Rhinoviruses do not persist in the body after infection and are not transmitted to animals.
• Isolated populations, such as St. Kilda's residents, have experienced viral extinction due to the absence of new hosts.
• If all humans were isolated from one another, the common cold would likely die out, but a small group of immunocompromised individuals could serve as reservoirs for the virus.
• The absence of colds might be detrimental to human health, as they may help train and calibrate our immune systems.

Quotes

“If we divide up the world’s land area evenly, there’s enough room for each of us to have a little over 2 hectares each, with the nearest person 77 meters away.”

Glass Half Empty

Takeaways

• In a traditional glass of water, the pessimist and optimist have different perspectives on the amount of liquid present.
• If the empty half of a glass were actually a vacuum, it would not last long due to the effects of air molecules and water vapor.
• Air molecules move quickly enough to enter a vacuum, causing the water in the glass to boil and fill the space with water vapor.
• The vacuum collapse sends a pressure wave through the liquid and the glass, potentially leading to a water hammer effect and glass breakage.
• The forces involved in a vacuum collapse are strong enough to destroy even heavy drinking glasses.

Quotes

“The lesson: If the optimist says the glass is half full, and the pessimist says the glass is half empty, the physicist ducks.”

Alien Astronomers

Takeaways

• Radio transmissions from Earth, such as TV and early-warning radar, are unlikely to be detectable by alien astronomers due to their short duration and decreasing power.
• The most powerful radio signal from Earth is the beam from the Arecibo telescope, but it transmits only occasionally and in a narrow beam.
• Visible light reflecting off Earth could potentially be detected by alien astronomers, revealing information about our atmosphere and possibly even our water cycle and oxygen-rich atmosphere.
• If we want to make contact with alien civilizations, we could send probes out of the solar system using advanced propulsion methods and try to guide them towards inhabited planets. However, landing safely would require a large amount of fuel and slowing down, which would also require significant resources.

No More DNA

Takeaways

• Losing your DNA would cause a third of a pound weight loss and instant twitching.
• Movement may accelerate body parts due to changed mass.
• Destroying angel mushroom poisoning causes irreversible cell damage leading to death from organ failure or infection.
• Chemotherapy and radiation harm DNA, causing similar symptoms such as nausea, vomiting, diarrhea, immune system collapse, and death.
• Severe radiation poisoning results in a latent period where the body is still functioning but vulnerable to infections leading to death.
• Losing your DNA would likely cause abdominal pain, nausea, dizziness, rapid immune system collapse, and death within days or hours from infection or organ failure.
• In a dystopian future with Orwellian governments collecting genetic information, losing your DNA would make you invisible.

Quotes

“If you eat a destroying angel, for the rest of the day you’ll feel fine. Later that night, or the next morning, you’ll start exhibiting cholera-like symptoms—vomiting, abdominal pain, and severe diarrhea. Then you start to feel better. At the point where you start to feel better, the damage is probably irreversible. Amanita mushrooms contain amatoxin, which binds to an enzyme that is used to read information from DNA. It hobbles the enzyme, effectively interrupting the process by which cells follow DNA’s instructions. Amatoxin causes irreversible damage to whatever cells it collects in. Since most of your body is made of cells,4 this is bad. Death is generally caused by liver or kidney failure, since those are the first sensitive organs in which the toxin accumulates. Sometimes intensive care and a liver transplant can be enough to save a patient, but a sizable percentage of those who eat Amanita mushrooms die.”

Interplanetary Cessna

Takeaways

• An electric motor is necessary for interplanetary flight due to the absence of oxygen on most solar system bodies.
• Most solar system bodies lack sufficient atmosphere for planes to fly, resulting in crashes or falling straight to the ground.
• Mars presents a significant challenge for aviation due to its thin atmosphere and high gravity.
• Venus has an extremely dense and hot atmosphere that would cause a plane to melt and fail rapidly.
• Jupiter's strong gravity makes it impossible for planes to fly.
• Saturn's weaker gravity and slightly denser atmosphere may allow for limited flight but still presents challenges due to cold temperatures and high winds.
• Uranus and Neptune are inhospitable to aviation due to their extreme cold temperatures and lack of features.
• Titan, with its thick atmosphere and low gravity, could provide an environment for humans and planes to fly, but the extreme cold temperature remains a challenge.

Quotes

“X-Plane tells us that flight on Mars is difficult, but not impossible. NASA knows this, and has considered surveying Mars by airplane. The tricky thing is that with so little atmosphere, to get any lift, you have to go fast.”

“Your plane would fly pretty well, except it would be on fire the whole time, and then it would stop flying, and then stop being a plane.”

“In fact, humans on Titan could fly by muscle power. A human in a hang glider could comfortably take off and cruise around powered by oversized swim-flipper boots—or even take off by flapping artificial wings. The power requirements are minimal—it would probably take no more effort than walking.”

“But I’ve never seen the Icarus story as a lesson about the limitations of humans. I see it as a lesson about the limitations of wax as an adhesive.”

Yoda

Takeaways

• Yoda's greatest display of Force power in the original trilogy was lifting an X-wing from a swamp.
• The energy required to lift an object is equal to its mass, gravity, and height.
• The X-wing weighed around 5 metric tons (12,000 pounds).
• The X-wing rose at approximately 0.39 m/s.
• Gravity on Dagobah is 0.9g.
• Yoda's peak power output was about 19kW or 25 horsepower, enough to power a block of suburban homes and equivalent to the power of a Smart Car motor.
• Telekinesis is one type of Force power; other types include lightning.
• The Emperor's lightning display was around 10 kilowatts.
• Luke's peak output with the Force was 400 watts, sustained for only a fraction of a second.
• It would take 100 million Yodas to meet current global electricity demands.

Quotes

“Lastly, we need to know the strength of gravity on Dagobah. Here, I figure I’m stuck, because while sci-fi fans are obsessive, it’s not like there’s gonna be a catalog of minor geophysical characteristics for every planet visited in Star Wars. Right? Nope. I’ve underestimated the fandom. Wookieepeedia has just such a catalog,”

“So Yoda sounds like our best bet as an energy source. But with world electricity consumption pushing 2 terawatts, it would take a hundred million Yodas to meet our demands. All things considered, switching to Yoda power probably isn't worth the trouble — though it would definitely be green.”

Flyover States

Takeaways

• Virginia is the most flown-over state in the US, despite having several major airports and being home to two airports serving Washington D.C.
• Hartsfield-Jackson Atlanta International Airport is a major contributor to the high number of flights over Virginia due to its status as Delta Air Lines' hub airport and the large volume of northeastern US bound flights passing through it.
• Toronto Pearson International Airport (YYZ) is another significant source of flights over Virginia, thanks to its many direct flights to the Caribbean and South America that cross US airspace on their way to their destinations.
• Delaware has the highest ratio of flights-over-to-flights-to among all states due to having no commercial airports.
• Hawaii is the least flown-over state in terms of total number of flights, while California holds that position when considering ratio of flights-over-to-flights-to.
• Most international travelers avoid flying over California since jet-fuel-laden planes were used as weapons on 9/11 and the FAA has tried to limit unnecessary fuel-heavy flights crossing the US.
• Hawaii is the most flown-under state due to its location opposite Central Africa, where there are fewer commercial flights compared to other continents.

Falling with Helium

Takeaways

• Falling from great heights is dangerous, but a large balloon can act as a parachute and help ensure a non-fatal landing.
• A balloon filled with air rather than helium would need to be 10-20 meters across to act as a parachute.
• Helium makes it easier to lift objects, but a relatively small helium balloon will only slow your fall, not support your weight.
• To fill a large enough helium balloon for safety, you would need many tanks and quick inflation.
• The terminal velocity of compressed helium cylinders is high, giving you limited time to empty them all before landing.
• It's impossible to avoid a sudden stop at the end of a fall, making controlling your descent crucial for survival.
• Falling from a great height isn't inherently dangerous; rather, it's the rapid deceleration that can be deadly.
• Avoid medical examiners if you don't want stern lessons!

Quotes

“It’s not the fall that kills you, it’s the sudden stop at the end.”

“While researching this answer, I managed to lock up my copy of Mathematica several times on balloon-related differential equations, and subsequently got my IP address banned from Wolfram|Alpha for making too many requests. The ban-appeal form asked me to explain what task I was performing that necessitated so many queries. I wrote, “Calculating how many rental helium tanks you’d have to carry with you in order to inflate a balloon large enough to act as a parachute and slow your fall from a jet aircraft.” Sorry, Wolfram.”

Everybody Out

Takeaways

• Moving one person out of Earth's gravity requires at least 4 gigajoules of energy, equivalent to a megawatt-hour or 90 kg of gasoline
• Lifting all 7 billion people would require 2.8×1018 joules, about 5% of the world's annual energy consumption
• Traditional rocket fuels require significant amounts of fuel due to the need to lift their own weight
• Space elevators with strong tethers or nuclear pulse propulsion are alternative launch systems proposed to overcome Earth's gravity
• Sending all humans into space would tax resources heavily and potentially destroy the planet.

Quotes

“There are hopes that carbon nanotube-based materials could provide the required strength—adding this to the long list of engineering problems that can be waved away by tacking on the prefix “nano-.”

Self-Fertilization

Takeaways

• Humans require two sets of DNA from two different individuals to create a new organism.
• Stem cells, which can form any type of tissue, have the potential to produce sperm or eggs.
• In 2007, researchers made progress in turning bone marrow stem cells into spermatogonial stem cells, but they couldn't fully develop them into sperm.
• In 2009, these same researchers claimed to have produced functioning sperm cells, but the paper was retracted due to plagiarism.
• Creating a human from a single individual would result in an organism with severe genetic damage and a high inbreeding coefficient, leading to various health issues and decreased survival chances.
• Humans have 23 chromosomes, each containing a large amount of genetic information that affects numerous traits through various mutations and variations.
• Genetic diversity is important because it reduces the odds of rare and harmful mutations appearing in the same place on both sides of the chromosome.
• Biologists use the inbreeding coefficient to measure the percentage of identical chromosomes, with a child from unrelated parents having a coefficient of 0 and a completely duplicated set of chromosomes having a coefficient of 1.
• Self-fertilization is rare among complex organisms due to its risks, but it does occur in some species under specific conditions.

Quotes

“Even calling DNA “source code” sells it short—compared to DNA, our most complex programming projects are like pocket calculators.”

“Self-fertilization is a risky strategy, which is why sex is so popular among large and complex organisms.”

High Throw

Takeaways

• Humans are the only animals that can reliably throw objects at targets.
• Throwing requires precise timing and timing errors can cause missed targets.
• Humans are better at throwing things forward than upward.
• Using devices or tools to redirect objects upward can help achieve greater heights.
• A golf ball might be a superior projectile for throwing due to its lighter weight allowing for faster pitching arm movement.
• Aroldis Chapman could potentially throw a golf ball sixteen giraffes high based on aerodynamic calculations.
• Using techniques like a five-year-old may result in surpassing all recorded throwing records.

Quotes

“Horned lizards shoot jets of blood from their eyes for distances of up to 5 feet. I don’t know why they do this because whenever I reach the phrase “shoot jets of blood from their eyes” in an article I just stop there and stare at it until I need to lie down.”

“To put that in perspective, it takes about five milliseconds for the fastest nerve impulse to travel the length of the arm. That means that when your arm is still rotating toward the correct position, the signal to release the ball is already at your wrist. In terms of timing, this is like a drummer dropping a drumstick from the tenth story and hitting a drum on the ground on the correct beat.”

Lethal Neutrinos

Takeaways

• Neutrinos are ghostly particles that barely interact with matter and mostly ignore ordinary atoms.
• Supernovae release huge amounts of energy and neutrinos during a core collapse.
• The dose of neutrino radiation at a distance of 1 parsec from a supernova would be around half a nanosievert, which is much less than a fatal dose (4 sieverts).
• If you observed a supernova from 1 AU away and avoided being incinerated or vaporized, the neutrino radiation alone could still kill you.
• Neutrinos are unimaginably insubstantial compared to supernovae's immense size.

Quotes

“Here’s a question to give you a sense of scale. Which of the following would be brighter, in terms of the amount of energy delivered to your retina: A supernova, seen from as far away as the Sun is from the Earth, or the detonation of a hydrogen bomb pressed against your eyeball?”

Speed Bump

Takeaways

• Speed bumps are designed to make drivers slow down, and hitting one at recommended speed results in a gentle bounce.
• Hitting a speed bump too fast can damage your car or cause injury to passengers, but most injuries occur to people in hard seats on buses, not car drivers.
• The typical sedan has a top speed of around 120 miles per hour and hitting a small speed bump at that speed won't likely result in injury.
• Larger speed bumps or speed humps can cause more damage to the car, but the jolt itself is not typically fatal for the driver.
• At high speeds, cars generate lift forces that can cause the car to lift off the ground and crash before hitting a bump.
• There is no known limit to how fast a car can go without crashing or being destroyed by other forces before reaching the speed of light.

Lost Immortals

Takeaways

• Two immortal people on an uninhabited Earthlike planet would take approximately 3000 years to find each other based on simple assumptions, but this model has several problems.
• Visibility and geography are major challenges in finding each other.
• The optimal strategy for the lost immortals depends on whether they have time to plan beforehand or not.
• Following coastlines is a sensible approach, but it may not guarantee meeting the other person.
• Marking trails and following them when found increases the chances of finding each other.
• Ant-like behavior, leaving a trail and following it when found, is an effective strategy for finding a partner on an uninhabited planet.

Orbital Speed

Takeaways

• Space is closer than many people think, about 100 kilometers away
• Getting to space is relatively easy, but staying there requires going really fast (about 8 km/s) to avoid falling back into the atmosphere
• The majority of a rocket's energy is used to gain orbital speed, making it difficult and fuel-intensive to reach orbit
• Every spacecraft entering an atmosphere has used a heat shield instead of rockets to slow down due to practicality and fuel requirements
• 8 km/s is extremely fast, equivalent to moving more than 2 miles with every beat of a 131.9 beats-per-minute song like "I'm Gonna Be (500 Miles)" by The Proclaimers.

Quotes

“Space is about 100 kilometers away. That’s far away—I wouldn’t want to climb a ladder to get there—but it isn’t that far away. If you’re in Sacramento, Seattle, Canberra, Kolkata, Hyderabad, Phnom Penh, Cairo, Beijing, central Japan, central Sri Lanka, or Portland, space is closer than the sea.”

FedEx Bandwidth

Takeaways

• If transferring large amounts of data, it's faster to use physical storage devices sent via FedEx than sending files over the Internet (dubbed "SneakerNet").
• Currently, FedEx is capable of transferring 150 exabytes of data per day, while the Internet currently averages 167 terabits per second.
• Using microSD cards instead of hard drives could increase FedEx's data transfer capacity to 177 petabits per second or 2 zettabytes per day.
• Based on current growth rates, the Internet will reach FedEx's transfer capacity in 2040.
• Technologically, it is possible to build a connection that surpasses FedEx's bandwidth.
• The virtually infinite bandwidth of a FedEx-based Internet would come at the cost of long ping times (80,000,000-milliseconds).

Quotes

“IF YOU WANT TO transfer a few hundred gigabytes of data, it’s generally faster to FedEx a hard drive than to send the files over the Internet. This isn’t a new idea—it’s often dubbed “SneakerNet”—and it’s even how Google transfers large amounts of data internally.”

Free Fall

Takeaways

• The largest purely vertical drop on Earth is Canada's Mount Thor, allowing for a free fall of about 26 seconds.
• A human reaches terminal velocity at around 55 meters per second.
• Falling from Ireland's Cliffs of Moher results in only about eight seconds of free fall.
• Skilled skydivers can glide at almost a 45-degree angle, extending the fall.
• Wingsuits let you fall more slowly, potentially allowing for a minute or longer falls.
• The record for longest wingsuit BASE jump is three minutes and twenty seconds.

Sparta

Takeaways

• In order to blot out the sun with arrows, archers would need to fire extremely quickly and densely, but even then, it would only result in a slight dimming, not complete blackout.
• Assuming an average of 150 millihertz frequency (8-10 arrows per minute), each arrow blocking about 20 cm2 of sunlight, and archers packed tightly with a density of 130 per meter, it would still only cover 1.56% of the sunlight passing through them.
• Attempts to use Gatling bows or unrealistic fire rates to achieve complete shadowing are not feasible due to the physical limitations of covering large areas with arrows and the logarithmic nature of how we perceive brightness.
• An alternative explanation could be that the Spartans made their boast based on attacking at dawn when the sun would be low on the horizon, potentially multiplying the shadow effect significantly.
• The key to achieving a perceived "blotting out" of the sun with arrows may not have been an actual goal, but rather a psychological advantage in confusing and demoralizing the enemy.

Drain the Oceans

Takeaways

• Creating a circular portal leading into space at the bottom of Challenger Deep would not cause rapid draining of the oceans, even if the portal is far away from Earth.
• The ocean level would drop less than a centimeter per day, and there wouldn't be a noticeable whirlpool at the surface.
• If the draining is sped up by opening more drains, some countries like the Netherlands would become high and dry, while others would gain new land.
• Some bodies of water like the Black Sea would stop shrinking when they are cut off from the drain.
• New islands would appear as the sea level drops, and some major oceans would become disconnected and stopped draining.
• Vacuuming up half the oceans would have massive impacts on climate and ecosystems, potentially causing a collapse of the biosphere and mass extinctions.
• Surviving humans after draining the oceans would face challenges like managing shallow seas, dealing with deep trenches, and adapting to a drastically changed world.
• Remember to clean the whale filter every few days if opening more drains.

Drain the Oceans: Part II

Takeaways

• Draining the oceans and filling Gale Crater on Mars with water would create a lake
• As more water accumulates, Mount Sharp becomes an island and eventually submerges
• Water spills over the north rim of the crater and begins to fill the North Polar Basin
• The map of Mars shows that there is still a lot of land far from the water, even after most of it has been covered
• Olympus Mons and other volcanoes remain uncovered despite being much smaller than on Earth
• Water filling in Noctis Labyrinthus creates bizarre islands
• The oceans on Mars would be transient as they would eventually freeze over and migrate to the poles.

Quotes

“the Curiosity rover is working so hard to find evidence of water, so I figured we could make things easier for it.”

“If you set out a cup of warm water on Mars, it’ll try to boil, freeze, and sublimate, practically all at once. Water on Mars seems to want to be in any state except liquid.”

Twitter

Takeaways

• Twitter allows 140 characters per tweet, but Unicode offers over a million possible character combinations.
• The number of meaningful English tweets is estimated to be around 2 × 10^46, based on the information content of typical written English.
• Reading all meaningful English tweets would take one person nearly 10^47 seconds (ten thousand eternal years).
• Information theory suggests that every message carries a certain amount of uncertainty and can convey multiple meanings.
• The number of distinct sentences in a language is much smaller than the total number of possible character combinations.

Quotes

“High up in the North in the land called Svithjod, there stands a rock. It is a hundred miles high and a hundred miles wide. Once every thousand years a little bird comes to this rock to sharpen its beak. When the rock has thus been worn away, then a single day of eternity will have gone by. —Hendrik Willem Van Loon”

Lego Bridge

Takeaways

• It would take approximately 350 million Lego bricks to connect New York and London, but this bridge wouldn't be able to support traffic or hold itself together.
• There are over 400 billion Lego pieces produced, but not all of them are usable for building a bridge.
• Assuming we build our bridge out of the most common 2x4 brick, there are around 5-10 billion of these bricks in existence, enough for a one-block-wide bridge.
• To support traffic, the bridge would need to be wider and possibly float on water.
• Lego bricks don't make a watertight seal when connected and aren't dense enough to displace enough water to carry weight, so a layer of sealant is necessary.
• The bridge would need to displace around 10 cubic meters of water per passenger car to stay afloat.
• Building a Lego bridge across the Atlantic Ocean faces challenges like wind and wave forces, needing extensive anchoring and buoyancy systems, and potential negative environmental impacts.
• The cost of building a Lego bridge across the Atlantic Ocean is prohibitively expensive compared to other options, such as buying and shipping London real estate.

Longest Sunset

Takeaways

• Sunset begins when the Sun touches the horizon and ends when it disappears completely.
• The longest sunsets occur near the poles, especially at the South Pole where the sunset can last for hours.
• To experience a long sunset on a paved road, wait for a day when the terminator just barely reaches your position, then drive north to stay ahead of it and U-turn to head south once you've passed it.
• This strategy can result in sunsets lasting approximately 95 minutes inside the Arctic Circle.
• Spinning counterclockwise in Svalbard can add a negligible amount of time to the Earth's clock, but may be worth it depending on who you're with.

Random Sneeze Call

Takeaways

• The chances of calling a random person who has just sneezed is approximately 1 in 40,000.
• Before making such a call, be aware of the extremely low chance (1 in 1,000,000,000,000) that you might accidentally catch someone who has murdered someone.
• The average person sneezes around 400 times per year.
• If you dial a random number, there's about a 1 in 10,000,000 chance that the person you reach has published an article on sneezing that day.
• Five people trying this experiment simultaneously have a very low probability (1 in 30,000) of getting a busy signal from each other and a virtually impossible chance (1 in 10,000,000,000,000,000,000) of both being struck by lightning.

Expanding Earth

Takeaways

• If the Earth's mean radius expanded by 1cm every second, people would notice a slight jolt at first but wouldn't feel any ongoing acceleration.
• After one day, the Earth would have expanded by 864 meters and gravity would only slightly increase.
• Roads and bridges could handle the expansion easily.
• GPS systems would stop working within hours due to precise timing disruptions.
• After a month, the Earth would have expanded by 26 kilometers, surface gravity would increase by 0.4 percent, and most structures would start failing.
• Astronauts on the ISS would need to evacuate within a few months as the ground rose toward them and gravity increased.
• The atmosphere would either put pressure on the expanding land and water or expand alongside it.
• After five years, gravity would be 25 percent stronger, most infrastructure would have collapsed, and skyscrapers would still hold up under wind stress.
• After ten years, gravity would be 50 percent stronger and breathing would become difficult due to the increased weight and decreasing oxygen levels.
• The Earth would eventually collapse into a black hole after reaching a point where adding more mass causes it to contract rather than expand.
• Before that happens, the Moon would spiral inward and break apart at the Roche limit, creating rings around the Earth for a short time.

Quotes

“GPS timing is incredibly precise; of all the problems in engineering, it’s one of the only ones in which engineers have been forced to include both special and general relativity in their calculations.”

“If you liked it, then you should have moved a mass inside its Roche limit.”

Weightless Arrow

Takeaways

• In a zero-gravity environment with Earth's atmosphere, air resistance would slow down an arrow and eventually cause it to come to a standstill after traveling very long distances.
• An arrow fired at 85 m/s would travel 400 meters in ten seconds and be much less dangerous due to its reduced speed.
• At walking speed, the arrow would experience very little drag and fly much farther than an Earth arrow.
• Airflow around a slow-moving arrow would behave more like honey than water, causing it to gradually come to a stop after several hours.
• The only sustained zero-gravity environment with an Earth-like atmosphere is the International Space Station, limiting the experiment's potential results.

Sunless Earth

Takeaways

• If the Sun went out, we would eliminate the risk of solar flares causing damage to electrical grids and communications systems.
• Satellite service would improve as the Sun's signal would no longer interfere with their radio signals.
• Ground-based observatories would benefit from cooler air and less atmospheric noise, resulting in sharper images.
• Dust could be placed into stable orbits around the Sun without decaying.
• Infrastructure costs for repairing and maintaining bridges over water could be reduced significantly.
• Trade would become cheaper as time zones would no longer be necessary.
• Children would be safer from sunlight-related health risks.
• Combat pilots would be safer from the sneezing reflex caused by bright sunlight.
• The parsnip threat, caused by phytophotodermatitis, would be eliminated.
• However, we would all eventually freeze and die as there would be no source of heat from the Sun.

Quotes

“Cheaper trade: Time zones make trade more expensive; it’s harder to do business with someone if their office hours don’t overlap with yours. If the Sun went out, it would eliminate the need for time zones, allowing us to switch to UTC and give a boost to the global economy.”

“A darkened Sun would liberate us from the parsnip threat.”

“In conclusion, if the Sun went out, we would see a variety of benefits across many areas of our lives. Are there any downsides to this scenario? We would all freeze and die.”

Updating a Printed Wikipedia

Takeaways

• The English Wikipedia receives approximately 125,000 to 150,000 edits each day.
• One page per edit is a reasonable estimate for keeping up with changes.
• Six printers running at once could keep pace with the edits, but it would be expensive.
• The inkjet printer's ink cost is high: around 30 cents per page for photos.
• A laser printer is recommended due to lower ink costs and durability.
• Wikipedia can go dark as a form of protest, requiring manual modifications to printed copies.
• The filing system required for printing the entire Wikipedia would be complex.

Facebook of the Dead

Takeaways

• Facebook currently has fewer dead users than living ones due to its young user base and growth rate.
• The number of dead Facebook users is projected to increase significantly in the coming decades as the generation who used Facebook in their youth grows older.
• Whether or not dead users will outnumber living users depends on how quickly Facebook can add new young users.
• Facebook may evolve into a piece of infrastructure that lasts for generations, but it's uncertain how long it will remain popular.
• Decisions about the fate of deceased users' accounts, such as access to private data and memorial pages, are currently being sorted out through trial and error.

Quotes

“The US isn’t a perfect model of the world,”

Sunset on the British Empire

Takeaways

• The British Empire spanned the globe, leading to the saying that the Sun never set on it since it was always daytime somewhere in the empire.
• The exact time when the Sun stopped setting on the entire British Empire is unclear, but it might have been around the late 1700s or early 1800s when Australian territories were added.
• Britain currently has 14 overseas territories as direct remnants of the British Empire.
• The Sun doesn't set on all 14 British territories at once, and if the UK loses one tiny territory, it will experience its first Empire-wide sunset in over two centuries.
• The Pitcairn Islands have a population of a few dozen people and are part of the British Empire, extending the daylight for the empire for now.
• An eclipse in April 2432 will end the streak of uninterrupted daylight for the British Empire if it occurs over the Pitcairn Islands at the right time, but no such eclipse is expected for the next thousand years.
• Eventually, an eclipse will come for the island and the Sun will finally set on the British Empire.

Quotes

“The whole process of claiming a colony (on land already occupied by other people) is awfully arbitrary in the first place. Essentially, the British built their empire by sailing around and sticking flags on random beaches.”

“Every night, around midnight GMT, the Sun sets on the Cayman Islands, and doesn’t rise over the British Indian Ocean Territory until after 1:00 a.m. For that hour, the little Pitcairn Islands in the South Pacific are the only British territory in the Sun. The Pitcairn Islands have a population of a few dozen people, the descendants of the mutineers from the HMS Bounty. The islands became notorious in 2004 when a third of the adult male population, including the mayor, were convicted of child sexual abuse. As awful as the islands may be, they remain part of the British Empire, and unless they’re kicked out, the two-century-long British daylight will continue.”

Stirring Tea

Takeaways

• Stirring a cup of tea adds negligible heat, approximately a ten-millionth of a watt.
• Boiling a cup of water requires a significant amount of energy, approximately 700 watts or the equivalent of one horsepower.
• Heating water from room temperature to nearly boiling in two minutes requires a powerful source.
• Microwaving a cup of water for two minutes at 700 watts delivers a large amount of energy.
• Stirring tea doesn't significantly affect its cooling rate compared to not stirring, dipping a spoon in and out, or lifting it.
• It is impossible to boil tea by stirring it hard enough due to the required power and fluid dynamics issues.

Quotes

“The amount of power in question, 700 watts, is about a horsepower, so if you want to boil tea in two minutes, you’ll need at least one horse to stir it hard enough.”

All the Lightning

Takeaways

• If all the world's lightning struck in the same place at once, it would deliver approximately two atomic bombs' worth of energy, enough to power a game console and plasma TV for several million years or support US electricity consumption for five minutes.
• A lightning bolt from this event would leave a crater the size of a basketball court and cause widespread destruction, including spontaneously igniting surfaces for miles around.
• Lightning rods cannot protect against such a massive lightning bolt due to the ground's poor conductivity at the impact point.
• Catatumbo lightning in Venezuela, which generates a flash every two seconds, could store enough power from one night to run a game console and plasma TV for roughly a century.
• Harvesting electricity from global or even localized lightning is impractical due to the difficulty of controlling where it strikes and the fact that sunlight delivers more energy than lightning in most areas.

Quotes

“THEY SAY LIGHTNING NEVER strikes in the same place twice. “They” are wrong. From an evolutionary perspective, it’s a little surprising that this saying has survived; you’d think that people who believed it would have been gradually filtered out of the living population.”

Loneliest Human

Takeaways

• The six Apollo command module pilots who stayed in lunar orbit during a Moon landing, such as Mike Collins and Dick Gordon, came the closest to achieving the farthest human isolation from every other living person, at about 3585 kilometers.
• Polynesians may have come close to achieving this feat but it is unlikely we'll ever know for sure.
• Antarctic explorers, such as Robert Falcon Scott and Pierre François Péron, came close to achieving this record but were not quite far enough from inhabited areas.
• Astronauts Mike Collins and Al Worden did not feel lonely during their isolated experiences in space.

Quotes

“There’s a thing about being alone and there’s a thing about being lonely, and they’re two different things.”

“Introverts understand; the loneliest human in history was just happy to have a few minutes of peace and quiet.”

Raindrop

Takeaways

• A hypothetical rainstorm could contain all its water in one giant drop instead of scattered rain.
• This giant drop would have a volume of 600 million tons and a diameter over a kilometer.
• The drop forms a few kilometers above the surface and falls at 90 meters per second (200 mph).
• Upon impact, the drop creates a supersonic omnidirectional jet that destroys everything in its path.
• The aftermath of the drop results in widespread destruction and fear, but eventually, scientists are unable to explain the phenomenon.

Quotes

“Eventually, they give up, and the unexplained meteorological phenomenon is simply called a “dubstep storm,” because—in the words of one researcher—“It had one hell of a drop.”

SAT Guessing

Takeaways

• If everyone taking the SAT guessed on every multiple-choice question, there would be no perfect scores due to the low probability of getting all questions right.
• In 2014 version of the SAT, there were 44 math, 67 critical reading, and 47 writing section multiple-choice questions.
• Probability of getting all 158 questions correct is extremely low (one in 27 quinquatrigintillion).
• If all 4 million 17-year-olds took the SAT and guessed randomly, no one would get a perfect score.
• The odds of getting a perfect SAT score by guessing are worse than the odds of an event with extremely low probability, like every living ex-President and Firefly main cast members being struck by lightning on the same day.

Quotes

“What if every day, every human had a 1 percent chance of being turned into a turkey, and every turkey had a 1 percent chance of being turned into a human?”

Neutron Bullet

Takeaways

• A bullet with the density of a neutron star would weigh as much as the Empire State Building.
• Neutron stars are some of the densest objects in the universe, formed when a giant star collapses under its own gravity.
• You cannot make a bullet from neutron star material as it will re-expand into superhot normal matter and release immense energy.
• If a neutron bullet were to hit the Earth's surface, it would create a huge crater with no entry hole and leave a trail of superhot plasma behind.
• To keep a neutron bullet near the surface, you would need an infinitely strong pedestal and a base large enough to spread the weight out.
• The gravity from the bullet would tug in the direction of the pedestal and create a perceived slope.
• To touch a neutron bullet, you would need a full-body support harness or at least a neck brace, and your fingertips would dislocate when they come into contact with it due to the overwhelming force.
• Surrounding the bullet with water allows you to touch it without any difficulty as the water is able to counteract the gravity of the bullet.
• Adding salt to the water makes it denser and helps your fingers buoyant enough to touch the bullet, while adding vodka makes the water less dense if your fingertips are getting sucked in.

Quotes

“This would be something never before seen in the history of the universe: an underground shooting star.”

Richter 15

Takeaways

• The Richter scale measures the energy released by an earthquake and goes beyond 10, with 9+ earthquakes altering Earth's rotation and length of the day.
• A magnitude 15 earthquake on Earth would release almost 1032 joules of energy, equivalent to the gravitational binding energy of the Earth or the energy from packing it with hydrogen bombs and detonating.
• Magnitude 0 earthquakes do exist, with examples ranging from a Dallas Cowback running into a garage to a penny falling off a dog.
• There are negative magnitudes, representing smaller seismic events like a cat falling off a dresser or a key press on a keyboard.
• The Richter scale has been replaced by the "moment magnitude" scale, with other units of measure also becoming obsolete in some cases.

Quotes

“two magnitude 9+ earthquakes this century both altered the length of the day by a tiny fraction of a second.”

“A magnitude 15 earthquake would involve the release of almost 1032 joules of energy, which is roughly the gravitational binding energy of the Earth. To put it another way, the Death Star caused a magnitude 15 earthquake on Alderaan.”

“Sometimes it’s nice not to destroy the world for a change.”

Discussion

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