PDF Summary:What If, by Randall Munroe

What wild scenarios might unfold if the laws of physics and nature were stretched to their limits? In What If, author Randall Munroe takes readers on an imaginative journey that explores mind-bending hypothetical situations. From the Earth suddenly stopping its spin to transferring every drop of ocean water to Mars, these thought experiments reveal the extraordinary forces that shape our world—and what could transpire should they be radically altered.

Turning to the cosmos beyond our planet, the book tackles the complexities of space travel, resource requirements for moving entire populations, and constructing a tangible version of the Periodic Table—complete with radioactive elements. While firmly rooted in science, this entertaining overview will leave you contemplating the incredible "what ifs" that lurk within physics, astronomy, chemistry, and beyond.

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The writer analyzes the likelihood of enduring a theoretical impact with the thirty-two largest bodies in our solar system. The discussion expands to encompass planets enveloped by thick atmospheres, highlighting the diverse challenges a spacecraft intended for travel between planets would face. The Sun's extreme heat would swiftly result in the complete destruction of any aircraft that ventures too close.

Explorations that encompass aspects of human health and physiology

Exploring hypothetical scenarios offers fascinating insights into human biology and the biological sciences, especially when evaluating the consequences of substantial reductions in genetic material and the impact of drastic alterations to the environment of Earth.

Exploring the consequences that would ensue should one's genetic data suddenly disappear.

The manifestations and expected outcomes could be comparable to those encountered from exposure to treatments such as radiation therapy and chemical-based cancer treatments, as both have the potential to harm DNA.

If a person's genetic material were to disappear suddenly, they would experience a weight loss of about one-third of a pound, feel a steady vibration from their cells contracting, and might observe a slight shudder due to the decrease in mass, following the principle that force is equal to mass multiplied by acceleration. This is somewhat comparable to the effects of DNA-targeting toxins like amatoxin in Amanita mushrooms, which hinder the functioning of cells' DNA-reading enzymes, causing significant damage to the hepatic or renal systems. Early signs such as gastrointestinal upset and loose stools may indicate cholera, which then leads to a period of apparent recovery even as the cells suffer permanent harm.

Chemotherapy substances such as Doxorubicin target DNA, leading to a complex state that culminates in cellular mortality. Radiation exposure can harm DNA and is particularly harmful to cells that undergo rapid division, primarily found in the bone marrow and the digestive tract. The disappearance of an individual's DNA could be equated to enduring the effects of radiation, which encompasses a stage known as the "walking ghost" phase before the immune system ultimately fails.

Exploring the pivotal part played by diverse genetic characteristics in the evolution process.

The well-being of a population is greatly dependent on the diversity of its genetics. Inbreeding may heighten the risk of progeny inheriting harmful characteristics, for instance, when they inherit two faulty gene variants, which can result in a condition known as spinal muscular atrophy. Genetic diversity acts as a safeguard, diminishing the impact of mutations that occur often. By steering clear of inbreeding, the likelihood of harmful mutations emerging is reduced.

Investigating the changes in biology that happen as a result of the Earth's constant growth.

Predicting the impacts on human physiology, infrastructure, and the environment

If the Earth were to suddenly expand, individuals might feel a sudden jolt with the capacity to disrupt their balance. In five years, the increased gravitational force would make a person who once weighed 70 kilograms perceive their weight as if it has increased to 88 kilograms. The growth of the landmass, rather than the gravitational pull alone, would lead to the collapse of most infrastructure.

Exploring the future of humanity and other species during such significant alterations of our world.

In an environment where gravity is substantially stronger, sustaining life becomes more difficult as breathing requires more effort and the air becomes denser. Outcomes vary from needing environments that sustain a regulated pressure to struggling unsuccessfully against powerful gravitational forces. Geological processes could contribute to the observed steadiness of Earth's climate, a phenomenon that is also apparent in larger exoplanets.

Ultimately, within a century, unsurvivable conditions would pervade due to gravitational forces surpassing a magnitude of sixfold that of Earth's gravity. Should humanity overcome the initial challenges, the continuous growth could lead to the conversion of Earth into a more compact astronomical object, such as a neutron star, or in cases of extreme mass accumulation, into a black hole.

Delving into the cosmos and contemplating voyages that transcend the confines of Earth's atmosphere.

Exploring the limits of current technology in relation to the energy requirements and capabilities of spacecraft for space travel.

Evaluating the feasibility and calculating the energy required to launch each person into outer space.

The writer examines the technical obstacles and power requirements necessary to launch every person into outer space.

Investigating the practical and technical challenges involved in relocating on such a grand scale.

Relocating every individual from our planet would present significant logistical and technological challenges. To escape Earth's gravitational force, an individual weighing 65 kilograms would need to utilize 4 gigajoules of energy. Globally, the necessary energy is 2.8 x 10^18 joules, which is about 8 petawatt-hours, representing a mere 5 percent of the planet's annual energy consumption.

A one-ton spacecraft would require between 20 and 50 tons of traditional rocket fuel. Launching the entire human population into space, with a combined weight of approximately 400 million tons, would require a fuel mass that is several magnitudes greater, measured in the tens of trillions of tons. Rockets must transport their own propellant, which greatly increases their total weight and the energy required for liftoff. The logistics involved necessitate a level of adaptability that our present technology cannot provide.

Considering alternative propulsion methods beyond conventional rocket technology

Other methods for propelling spacecraft beyond Earth's atmosphere include the idea of a space elevator and the use of atomic detonation for thrust. These technologies, while promising, also encounter their own set of obstacles. Technological advancements in carbon nanotubes could provide the required durability for the creation of a lift designed to operate between Earth and space. Utilizing nuclear explosions to propel a spacecraft might enable the deployment of significant payloads into orbit.

Exploring the furthest distance and longest time a nuclear submarine could operate if it were in the emptiness of outer space.

Operating a nuclear submarine in the immense expanse of space presents significant challenges in maintaining life support systems and managing the vessel's functions.

Identifying the technical challenges of maintaining life support and avoiding orbital decay

In the vacuum of space, a nuclear submarine would find its usual method of generating oxygen inoperative, necessitating dependence on a finite oxygen reserve that would only support the crew for a very limited period. In the vacuum of space, where water is not available for cooling and heat disperses poorly, the submarine's personnel would need to manage the reactor's activity to generate the necessary heat.

Assessing the options for a safe reentry and landing

One could contemplate using the ship's torpedoes to exit orbit securely. If the deployment channels were reversed, this could create enough change in velocity to propel the submarine out of its established path. The return to Earth is perilous due to the absence of essential ablative tiles on the spacecraft, which are necessary for heat dissipation, and its design not being conducive to re-entry, creating the hazard of the craft losing stability and disintegrating. Survival depends on being firmly strapped into a seat designed for high-speed collisions and successfully ejecting clear of the wreckage, while also making sure the missiles are deactivated to prevent explosions.

Hypothetical natural disasters and catastrophic events

Exploring the implausible but intellectually engaging scenarios of extreme natural catastrophes can reveal the sheer forces of nature and their potential consequences on our world. Imagine two hypothetical situations: one where the earth shakes with a force measuring 15 on the Richter scale, and another where a colossal raindrop is formed.

Investigating the catastrophic outcomes that would result from a major urban area being struck by an earthquake of magnitude 15.

Exploring the disastrous outcomes that could ensue from a seismic event of that magnitude.

An earthquake registering 15 on the Richter scale would represent a disastrous event, releasing energy almost equal to that needed to overcome Earth's gravitational binding—around a hundred nonillion joules. An earthquake of this magnitude would be catastrophic, resulting in the total destruction of our planet akin to the fate of Alderaan in "Star Wars," and would pulverize all matter into swiftly expanding gas, including instruments that detect ground motion. In this overwhelming hypothesis, our planet could reflect the devastation of Alderaan, encircled by a more intense and widespread ring of wreckage than any catastrophe ever observed.

Evaluating how minor seismic occurrences differently affect individuals' daily experiences.

Seismic activities that are measured at less than zero on the Richter scale, while not as devastating as a significant earthquake, can nonetheless have minor but noticeable effects. For instance: The outcome would resemble the entire Dallas Cowboys squad running at full speed into a garage wall. A collision between a football player and a tree occurs with an intensity equivalent to an impact rated at magnitude -1.

• Magnitude A cat losing its footing and descending from a cabinet. Magnitude -3: Similar to a feline nudging a mobile phone until it tumbles from the top of a bedside table. Magnile -4: As trivial as a coin slipping from a canine.

Analyzing the scenario of a rainstorm condensing into a single massive droplet

The collision of such a colossal water mass unleashes extreme forces and causes immense destruction.

In this speculative scenario, the moisture amassed within a storm cloud could potentially merge into a solitary raindrop weighing an immense 600 million tons. As it descends from the cloud base, the droplet would swell at the bottom, turning into a frightening sight, and then it would convert into a high-energy plasma on its way to the ground. Upon collision at velocities surpassing 450 mph, the object would ignite flammable substances it encounters, yet the extreme chill of its considerable mass, moving faster than the speed of sound, would extinguish the fire. The surrounding area would be devastated by an immense explosion, releasing potent energies that obliterate all in their wake, leveling and erasing every trace of the terrain over a vast area, and forming a crater that in time becomes filled with murky water.

Exploring the potential atmospheric outcomes of envisioning such an extreme weather event.

The book, while not exploring the wider effects on climate, suggests that the immediate physical destruction would likely result in significant alterations to the local weather and climatic conditions. The mental impact of such a phenomenon worldwide would be significant, creating a widespread dread that any cloud might herald a new perplexing disaster, with flash floods impacting regions across extensive territories. Following this severe meteorological occurrence, the way humans interact with rainfall would be irrevocably changed.