What would happen if gravity became 5 percent stronger right now? originally appeared on Quora: the place to gain and share knowledge, empowering people to learn from others and better understand the world. Answer by Thomas Ulrich, Electrical engineering grad student at Stanford University, on Quora: What would happen if gravity became 5 percent stronger right now? Other answers massively underestimate the gravity of this situation. This is a clear "everyone dies" scenario. On second thought, maybe I should say "everyone fries" instead. This is pretty cataclysmic. Anyway, the point is that humans won’t make it very long. Let’s start with the effect on the earth’s orbit around the sun. An orbit is a delicate balance between gravity, which pulls a planet toward its star, and the planet’s velocity, which tends to carry it away into space. A sudden change in gravity disrupts the balance, resulting in Earth moving into a new, tighter elliptical orbit. At its closest, Earth will pass about 9% to 10% closer to the sun than it does today. (You can find the exact number using the vis-viva equation — it depends on where Earth is in its orbit when the laws of physics change.) That should be enough to trigger catastrophic climate change, leading to widespread famines and probably the collapse of the global economy, but it might not kill everyone. The next thing to consider is the impact on the sun. The sun also hangs in a balance: the pressure from the hot plasma in the interior tries to tear it apart, while gravity pulls it together. Again, a sudden change in the strength of gravity disrupts this equilibrium. Hydrogen gas from the sun’s surface falls toward the core, fusing into helium and explosively releasing vast amounts of energy. Is this enough to kill all life on Earth? I’m not entirely sure. As in a helium flash, most of the energy released gets converted into heat and doesn’t reach the sun’s surface. In the most optimistic scenario, we might not notice anything at all here on Earth. In fact, the increase in gravity does its worst damage deep beneath the earth’s surface. The earth’s core bears an immense load: the entire weight of our planet, about 6.6 x 10 21 tons of rock. Thanks to the new gravitational constant, all of this rock suddenly becomes 5% heavier. Unable to carry the extra burden, the core collapses inward, causing the rest of the planet to fall down on top of it. A quick estimate suggests that the surface might drop only about 10–20 km, but the exact number doesn’t matter so much: "everyone dies", either directly in the fall or shortly afterwards from the heat released as the crust buckles and collapses. Depending on the details of the collapse process, it’s conceivable that the entire surface of the planet could melt. Conclusion: don’t mess with gravity. This question originally appeared on Quora - the place to gain and share knowledge, empowering people to learn from others and better understand the world. You can follow Quora on Twitter, Facebook, and Google+. More questions:
This depends on exactly what you mean by this. Acceleration due to gravity is given by : $$g=\frac {GM} {r^2}$$ And note that $G$ is a universal constant, $M$ is the mass doing the attracting and $r$ is the distance from the object's center of mass. Let's assume you simply move twice as far away as $r$, then the gravitational acceleration you feel will be quartered - that power of two ! But if you made the Earth twice and big kept it's density the same - so you filled the extra space, what would happen ? Well : $$M=\frac 4 3 \pi r^3 \rho$$ Where $\rho$ is average density. That makes : $$g = \frac 4 3 G \pi \rho r$$ So in this case ( doubling the radius and filling the space ), the gravitational acceleration at the new radius would be twice as large - a completely different result from the first interpretation of your question. So, as always in physics, you need to be very precise in describing what you mean. (Image credit: Karl Tate / Life's Little Mysteries) During the new DC Comics Universe series "Flashpoint," in which a time-traveling supervillain alters the past to warp the present, Life's Little Mysteries presents a 10-part series that examines what would happen if a major event in the history of the universe had gone just slightly different. Part 7: What if ... Earth were twice as big? If Earth's diameter were doubled to about 16,000 miles, the planet's mass would increase eight times, and the force of gravity on the planet would be twice as strong. Life would be: Built and proportioned differently. If gravity were twice as strong , bodies possessing the same construction and mass as our flora and fauna would weigh twice as much and would collapse. It'd be "timber!" for tall, thick trees such as redwoods. Large, sunward-reaching plants might still develop, but would require stiffer architectures of cellulose fibers or another material altogether. Animals would have to be thicker-legged to support their weight. As for humans, our appearance would depend on the evolutionary demands placed on our biological forebears in a higher-gravity world, said Neil Comins, a professor of physics at the University of Maine. "If our ancestors had to run fast and fight hard, then we would be burly, but if not, we could be thin and light," Comins told Life's Little Mysteries. Previously: What would life be like if the moon had never formed ? Next: What would life be like if the sun were half its size ? Head to Newsarama.com for complete Flashpoint coverage. |