Earth Is Not Wandering Today—How to Destroy It in Three Elegant Steps
Author: A Millisecond of Eternity
For years, certain mad scientists have dreamed of threatening government officials with doomsday schemes to obtain wealth, power, fame, and the fearful respect of the public. In the film The Wandering Earth, meanwhile, humanity chooses to wander through the universe with the entire planet—and its hopes—in tow. Today, however, we will not discuss how to make Earth wander. We will do the opposite and consider how to destroy it simply and elegantly.
Destroying Earth is no easy task. You could, of course, destroy human civilization, wipe out every higher life form with a super-plague, or invent nanomachines with extreme instructions that eliminate the entire biosphere. In every one of those cases, however, the ground beneath our feet would remain. It would continue orbiting the Sun for billions of years. Let us be serious: if you want to destroy the planet, you must truly make the whole planet your target.
Step One: Do the Math Correctly
Our planet is held together by its own gravity. You can imagine it as an enormous “onion” made of rock and magma. The innermost core uses gravity to hold the next layer of magma against it. Their combined gravity holds the next layer, and their total weight attracts the layer beyond that. You get the idea. The process repeats until it includes Earth’s entire mass—all 5.97×10^24 kilograms of it—whose gravity keeps you sitting in your chair instead of floating away.
If you want to destroy Earth, then, you could consider peeling this “onion” one layer at a time. You would need to send every layer, every rock, every speck of dust, and a vast quantity of molten magma into space. And merely putting them in space temporarily would not be enough: you would have to ensure that all this material escaped Earth’s gravity completely and forever.
In other words, every part of Earth that you discard must be accelerated to escape velocity. That is not easy. We generally use gigantic rockets merely to send a spacecraft weighing a few tonnes into orbit or beyond.
Once the process begins, however, it becomes progressively easier. Every piece of matter removed reduces Earth’s total mass and weakens its gravitational binding. As you peel away one layer after another, gravity grows weaker, making every layer easier to launch than the one before it. The whole process can be estimated with the formula for the gravitational binding energy of a uniform sphere, which relates the energy needed to destroy—or, more politely, “liberate”—a planet to its mass and radius. Earth would require roughly 10^32 joules.
Step Two: Find an Energy Source
That is a substantial amount of energy. In all of 2013, every human on Earth consumed a mere 10^20 joules to power everything humanity used: wood fires, engines, alarm clocks, televisions, electronic readers, and so on. Even if you somehow captured the complete output of every nuclear, hydroelectric, and fossil-fuel power station, every solar panel, every wind farm, and every other energy source—leaving none for anyone else—you would still need to collect it for a trillion years to reach the energy scale under discussion.
If you want to be taken seriously as a world-destroying mad scientist, you need a new plan. After all, in only about five billion years the Sun may evolve into a red giant and engulf Earth. There would be little point in destroying the planet after that, would there?
The Sun? It is enormous and bright, releasing vast quantities of energy every moment. Our star consumes about 400 million kilograms of hydrogen in nuclear fusion reactions every second, and that energy eventually travels into space as radiation. Most of the energy in sunlight is simply lost without doing anything interesting or useful; only a tiny fraction shines on Earth. Billions of years ago, algae and plants learned to use this energy through photosynthesis and put it to work for their own survival. It eventually passes through the food chain into the meal you are preparing to eat. But is that enough?
Step Three: Wait
If you covered Earth’s entire surface with solar panels and captured all the radiation reaching the planet, you would need … about 18 million years to collect enough energy to overcome Earth’s gravitational binding. That is certainly a major improvement on the trillions of years required when relying on human-made energy, but it remains a very long undertaking. Let us hope no superhero discovers your secret base in the meantime.
Only a small fraction of the Sun’s energy reaches Earth, however. What if you could somehow capture the Sun’s entire output? In that case, you would need only one week to collect enough energy for the job. One week! Not bad at all. Everyone on Earth would finally take your threats seriously. Then again, if you can build a device capable of collecting all the Sun’s energy … what are you still doing on Earth?
References
爱发电(点击图片跳转)