What If? 2

What If? 2 Plot Summary

Introduction

Have you ever wondered what would happen if the Earth suddenly started spinning so fast that a day lasted just one second? Or how many snowflakes it would take to cover the entire world in six feet of snow? These are the types of delightfully bizarre questions that occupy curious minds everywhere, especially those of children and scientists with active imaginations. The beauty of such seemingly ridiculous inquiries is that they invite us to stretch our understanding of physics, biology, and mathematics in unexpected ways. When we explore these fantastical scenarios through the lens of real science, we discover that the same principles that govern our everyday reality can be applied to even the most outlandish situations. By calculating how many pigeons it would take to lift a person, or examining what would happen if the Moon were made entirely of electrons, we gain a deeper appreciation for the fundamental laws of our universe. This journey through cosmic questions will reveal how scientific reasoning can be both practical and playful, providing insights that help us better understand not just hypothetical scenarios but also the very real world around us.

Chapter 1: The Impossible Physics of Everyday Objects

What would happen if you filled the Solar System with soup out to Jupiter? This seemingly absurd question actually leads us into fascinating territory concerning black holes, gravity, and the limits of our universe. If someone like five-year-old Amelia decided to fill the space between the Sun and Jupiter with soup, they would need approximately 2 × 10^39 liters—more energy than the Sun has produced in its entire lifetime. The resulting mass would be so enormous that it would create a black hole with an event horizon extending to Uranus. Despite what science fiction might suggest, being inside this black hole wouldn't immediately tear you apart. For a brief period, you might feel fine floating in the soup, unaware of the gravitational catastrophe surrounding you. The tidal forces of such a massive black hole would be relatively weak at human scale, meaning different parts of your body would experience similar gravitational pull. However, this peaceful moment wouldn't last long. As the soup collapsed inward toward the center, pressure would build quickly. Within minutes, the compression would crush you, and within half an hour, everything inside the black hole would fall to the center, where our understanding of physics breaks down completely. From outside, this soup black hole would begin consuming the rest of the Solar System, starting with Pluto and eventually cutting a swath through the Milky Way over thousands of years. This scenario teaches us something interesting about black holes: regardless of what material creates them, they all become essentially identical. Physicists call this the "no hair theorem"—whether made of soup, stars, or anything else, black holes retain only a handful of characteristics like mass, spin, and charge. So if you're planning to make cosmic soup, remember that the recipe always turns out the same in the end.

Chapter 2: Strange Powers of Natural Phenomena

Some of the most fascinating scientific questions emerge from everyday observations—like what happens when sunlight bounces through a magnifying glass or how lasers interact with raindrops. These ordinary phenomena harbor extraordinary potential when pushed to extremes, revealing surprising insights about the physics of our world. Consider the question of starting a fire using moonlight focused through a magnifying glass. While we know sunlight through a magnifying glass can easily burn paper, moonlight seems to present a similar scenario at lower intensity. Intuition suggests that with a large enough magnifying glass—perhaps 400,000 times bigger than a normal one, since moonlight is about 400,000 times dimmer than sunlight—you should be able to concentrate enough lunar light to create fire. However, this turns out to be impossible due to a fundamental principle in thermodynamics and optics. The limitation stems from what physicists call "conservation of étendue"—essentially, you can't use passive optical systems like lenses to make something hotter than the source of the light itself. The Moon's sunlit surface is only about 100°C, so focused moonlight cannot heat something beyond this temperature regardless of how large your magnifying glass is. This temperature is too low to ignite most materials. The principle explains why you can't use mirrors and lenses to create perpetual motion machines or generate unlimited heat from limited sources. Another fascinating natural phenomenon involves triboluminescence—the light produced when certain materials are crushed. Wint-O-Green Life Savers candies famously produce bright blue flashes when crushed in the dark. This occurs because breaking the sugar crystals separates electrical charges, creating tiny sparks that excite methyl salicylate molecules in the mint flavoring, causing them to fluoresce. It's related to the same mechanism that produces lightning, though scientists still don't fully understand all the details of either process. These examples illustrate how everyday phenomena contain hidden complexities. When we investigate them using scientific principles, we often discover that nature imposes elegant limitations on what's possible, while simultaneously offering unexpected pathways for energy to transform from one form to another.

Chapter 3: Astronomical Thought Experiments

If you've ever gazed at the night sky and wondered about the true scale of cosmic objects, astronomical thought experiments can provide mind-expanding perspectives. Consider this question: if Earth were a massive eyeball, how far could it see? An Earth-sized eye would have a pupil thousands of kilometers wide, capable of gathering an extraordinary amount of light. This hypothetical eye would have resolution approximately half a billion times better than a human eye. The diffraction limit—a blurring caused by light's wave nature—would still exist, but would be vastly reduced. Such an eye could theoretically read a printed page on the Moon's surface or discern continental features on exoplanets orbiting nearby stars. It could detect objects across most of the observable universe, though extremely distant galaxies would appear blurred due to quantum fluctuations in space itself potentially distorting light from far away sources. Another captivating cosmic thought experiment involves national "ownership" of space. If every country's airspace extended upward forever, which nation would control the largest portion of our galaxy? Due to Earth's axial tilt relative to the Milky Way, countries in the southern hemisphere would have a distinct advantage. The galactic core would pass through the airspace of Australia, South Africa, Chile, and other southern nations during Earth's daily rotation. At its peak, Australia would command more of the galaxy's stars than any other country, with the supermassive black hole at the center passing through its jurisdiction daily near the town of Broadwater. Cosmic thought experiments also help us comprehend the immense distances in space. If you attempted to drive a car at highway speed to the edge of the observable universe, it would take you approximately 480,000,000,000,000,000,000 years—about 35 million times the current age of the universe. Even with unlimited fuel and snacks, you'd face the ultimate boredom problem: 24 billion light-years of monotonous driving with very little scenery change as stars burn out and galaxies recede. These astronomical scenarios do more than entertain—they provide conceptual frameworks that help us grasp scales and relationships far beyond our everyday experience, connecting human imagination to the vastness of cosmic reality.

Chapter 4: Human Bodies Under Extreme Conditions

What happens to the human body in truly extraordinary circumstances? From deep-sea pressures to vacuum exposure, our physical forms have remarkable but definite limitations. When subjected to extreme conditions, the human body reveals both its resilience and vulnerability in surprising ways. Consider what would happen if you attempted to drink another person's blood who was intoxicated—would you become drunk? The answer requires understanding both blood volume and alcohol distribution. An average person contains about 5 liters of blood, and if someone had a blood alcohol concentration of 0.40 (which is potentially lethal), drinking all 14 glasses of their blood would give you only about 20 grams of ethanol—equivalent to drinking a pint of beer. This would raise your own blood alcohol level to approximately 0.05, barely enough to feel effects and well below the legal limit in many places. However, attempting to drink this much blood would likely cause vomiting long before any alcohol effects could manifest, as the human digestive system isn't designed to process large quantities of blood. Another fascinating extreme scenario involves human acceleration tolerance. If all rules of car racing were stripped away, leaving only the requirement to get a human around a track as fast as possible, how quickly could we complete the race? The limiting factor turns out to be human biology. During turns, drivers experience powerful g-forces, and most humans can only tolerate sustained forces of 3-6 g's for periods lasting an hour or longer. At 4 g's, the fastest possible time around a track like Daytona would be just under 1 hour and 45 minutes—significantly faster than current race times, but still limited by our physical tolerances. Perhaps most intriguing is what happens when human bodies encounter unusual substances, like if you were to feed ammonia directly into your stomach through a tube. The ammonia would immediately react with stomach acid, neutralizing it and producing significant heat in the process. Once the acid was neutralized, the remaining ammonia would cause severe tissue damage, with medical literature describing effects including "liquefaction necrosis," "protein denaturation," and even "saponification"—the conversion of cell membranes to soap. These extreme scenarios highlight the delicate chemical balance that maintains our bodies and the catastrophic consequences of disrupting it. Through these explorations of human limits, we gain a deeper appreciation for how our bodies function under normal conditions and the remarkable adaptations that allow us to survive in our particular slice of cosmic conditions.

Chapter 5: Mathematical Oddities in Our Universe

Numbers and mathematical relationships underpin reality in ways that often defy our intuition. From exponential growth to statistical improbabilities, mathematics reveals both the structure and strangeness of our universe when applied to unusual scenarios. Consider this question: If every person who owns a dog suddenly had that dog reproduce once yearly with five puppies, how long would it take for dogs to overrun Earth? Starting with about 2 billion dogs (assuming one-quarter of humans own one), the exponential growth becomes staggering. After just five years, every human would have 6-7 dogs. By year eleven, we'd reach the "101 Dalmatians point" with 101 dogs per person. After twenty years, dogs would be shoulder-to-shoulder across all land, and after forty years, skyscrapers would disappear beneath the barking ocean of fur. By year 55, dogs would outweigh the Moon, and around year 65, they would collectively outweigh Earth itself. This mathematical modeling demonstrates how exponential growth quickly creates physically impossible situations—a principle that applies to many real-world systems from population dynamics to viral spread. Another mathematical oddity arises when we consider our ancestral connections. Each person has 2 parents, 4 grandparents, 8 great-grandparents, and so on—an exponentially growing family tree as we look backward. But this can't continue indefinitely, as we'd eventually need more ancestors than humans who ever lived. The solution to this paradox is that our family trees overlap and intertwine. Research suggests that all living humans share identical ancestors from around 5000-2000 BCE—everyone alive today is descended from approximately 10-15 billion humans out of the 120 billion who have ever lived. This means roughly 10% of all humans who ever existed are your direct ancestors. Scale and proportion create further mathematical peculiarities. If we scaled down the Milky Way galaxy to a beach with sand grains proportionate to stars, what would that beach look like? While main-sequence stars like our Sun might indeed be sand-grain sized, enormous red giants would appear as baseballs or even beach balls scattered among the grains. Though these massive stars make up a tiny percentage of the galaxy's star count, they would constitute the majority of the beach's volume. Our familiar sandy Milky Way would actually resemble a field of boulders with patches of sand between them—revealing how our perception of cosmic structure often misses its true proportions. These mathematical thought experiments help us recognize patterns and relationships that extend beyond our immediate experience, showing how numerical analysis can transform our understanding of everything from family connections to galactic structure.

Chapter 6: Technological What-Ifs and Their Consequences

What if everyday technology operated on entirely different principles? From smartphones built with vacuum tubes to houses heated by toasters, these technological thought experiments reveal the constraints and efficiencies of modern engineering while highlighting the remarkable progress we've made. Imagine if your smartphone contained vacuum tubes instead of transistors. In principle, any computer built from transistors could be replicated with vacuum tubes, which perform the same basic function of controlling electrical signals. However, the size difference would be staggering. An iPhone 12 contains approximately 11.8 billion transistors packed into an 80 mL case. If built with vacuum tubes at the density used in early computers like UNIVAC, your phone would expand to the size of five city blocks. Beyond the size issue, your vacuum tube phone would consume a staggering amount of electricity—around 10^11 watts of power, generating enough heat to potentially melt granite. The comparison illustrates how miniaturization and energy efficiency have made modern computing possible. Another fascinating technological what-if explores alternative energy systems. If you wanted to heat your house using only toasters, how many would you need? Surprisingly, not that many. An average toaster uses about 1,200 watts, and a typical northern US home heating system produces about 25,000 watts of heat. This means about 20 toasters could theoretically heat your home. This calculation reveals an important thermodynamic principle: all electrical devices ultimately convert 100% of their energy to heat. Whether it's a toaster, light bulb, or computer, every watt of electricity eventually becomes a watt of heat in your home. Transportation technology offers particularly rich ground for speculation. If we stripped away all racing regulations and simply tried to get a human around a track as quickly as possible, what would the ultimate racing vehicle look like? The limiting factor isn't engineering but human biology—our bodies can only withstand certain g-forces before losing consciousness. At turns, drivers would experience forces that limit speeds to those creating no more than about 4-6 g's of sustained acceleration. Even with a perfectly engineered vehicle, the fastest possible time around a track like Daytona would still take about an hour, highlighting how human physiological limits often constrain technological advancement. These technological what-ifs do more than entertain—they demonstrate fundamental principles of physics, thermodynamics, and engineering while giving us greater appreciation for the elegant solutions that modern technology represents.

Chapter 7: Earth's Hidden Scientific Wonders

Our planet harbors countless scientific marvels operating quietly beneath our awareness. From the mysterious forces shaping our atmosphere to the surprising consequences of everyday substances, Earth itself is a laboratory of continuous natural experiments. Consider the seemingly simple question of where tire rubber goes as it wears down. When tires lose approximately half an inch of tread over their lifetime, that rubber—about 1.6 liters per tire—doesn't just disappear. If all this material remained on roads, highways would rise by about a third of a millimeter yearly. Instead, tire particles become airborne or wash away, entering our air, soil, and water systems as microplastics. These particles drift into rivers and oceans, affecting water chemistry and marine life. Recent studies have even linked chemicals from tire rubber in stormwater to salmon die-offs in the Pacific Northwest. This invisible pollution stream represents a significant environmental challenge without an obvious solution. Earth's oceans hold their own scientific wonders. If you placed an indestructible glass tube extending from the surface to the deepest part of the Mariana Trench, what would it be like to stand at the bottom? The air pressure inside would be nearly four times higher than at sea level, not from the surrounding water pressure (which the tube would hold back) but simply from being so far below sea level. The tube would create other fascinating effects—including the potential for a perpetual flow of water. Due to differences in temperature and salinity between deep and surface waters, oceanographer Henry Stommel suggested in 1956 that water flowing through such a tube might continue indefinitely, driven by these natural gradients. Perhaps most fascinating are Earth's optical phenomena. When light passes through our atmosphere, it bends slightly depending on air density. This creates mirages over hot surfaces and, more spectacularly, the Fata Morgana effect—where islands, ships, or coastlines appear to float above the horizon. These "floating castles" were named after Morgan le Fay, the sorceress of Arthurian legend, because people thought they resembled magical floating structures. The same principles explain why you feel colder looking at the night sky (your body heat radiates away into space) and why snowfalls can occur even when air temperatures remain above freezing. These hidden scientific wonders remind us that even familiar aspects of our planet operate according to complex physical principles. By examining these everyday phenomena through scientific inquiry, we discover that Earth itself remains our most accessible and fascinating laboratory.

Summary

At the heart of scientific exploration lies the courage to ask outlandish questions and the discipline to pursue their answers with rigorous methodology. The most seemingly ridiculous queries—from what would happen if you filled the Solar System with soup to how many dogs it would take to outweigh the Earth—serve as gateways to profound understanding. By pushing familiar concepts to their logical extremes, we illuminate the boundaries of physical possibility and reveal the elegant principles that govern our universe at all scales. The next time you encounter a strange "what if" scenario, consider approaching it as a scientist would—breaking it down into knowable components, applying established principles, and following the evidence wherever it leads. You might discover that answering questions about impossible scenarios helps clarify your understanding of possible ones. What would happen if all rainfall became candy? How would Earth change if gravity suddenly doubled? These playful thought experiments not only sharpen critical thinking but also remind us that curiosity itself—that distinctly human trait of wondering "what if"—remains our greatest scientific instrument.

About Author

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Randall Munroe

Randall Munroe, a former NASA roboticist, is the creator of the webcomic xkcd and the author of xkcd: volume 0. The International Astronomical Union recently named an asteroid after him; asteroid 4942 Munroe is big enough to cause a mass extinction if it ever hits a planet like Earth. He lives in Cambridge, Massachusetts.

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