What would be the biggest threat if gravity stopped? [closed]

Question

Suppose that the law of gravitation suddenly “stops working” one day, and all gravitational forces cease to exist. What would this mean for people on Earth? Could we survive for very long? If not, what would kill us?

Here are a few possible disruptions that come to mind that could potentially result from a sudden absence of gravity. You’ll have to help me gauge how feasible and dangerous each of these are for the future of humanity, as well as determine whether I’ve left anything important out:

• Everyday life would be hard without gravity. Cars would fly off of the road, people would float into space, etc. Sure, a considerable number of people would probably die as a result of this and the ensuing societal chaos, but people are smart and resilient. I don’t think this is enough to finish humanity off.
• Planets would fly out of their orbits and away from the Sun. This could result in a collision, but I’m guessing that this would be unlikely given how much empty space there is. However, one Earth gets far out enough, it will get very cold. Collisions with other celestial bodies might also be a problem if humans survive long enough for the Earth to reach, say, the Oort cloud.
• The Sun might explode violently without gravity to hold all of its gases together. At the very least, it will slowly disintegrate. The Sun exploding could easily destroy the Earth very quickly, but I don’t know enough astrophysics to know whether the absence of gravity would result in an explosion or a slow erosion of the Sun.

What do you think?

Answer 1

Remember the relative motions. The Earth is rotating at pretty close to 1000 mph at the equator. That motion is not cancelled. The Earth is moving around the sun at round-about 30 km per second. That motion is not cancelled. Without gravity, everything that is not solidly fixed to the mantle of the Earth wants to travel in a straight line, not continue in a curve that is currently imposed by gravity.

Quite rapidly the atmosphere mostly goes away. Only traces left within seconds. Any objects not solidly fixed down are going to fly off quite quickly. Oceans, most loose soil or rocky bits not actually part of the crust. The sky is quite suddenly full of a lot of loose stuff. In many cases, this means most things building-sized or smaller, since lots of buildings are built on non-rock foundations.

So anything that was not previously attached to the Earth's mantle starts flying away. Little bit of geometry, and ignoring air pressure which will speed things, it takes about 310 seconds to get 1 mile vertical from the surface. By then, the air pressure has long since dropped below where humans can breathe. So the first thing to get you is probably low pressure. It's not quite explosive, but it's very fast.

Predicting how the material of the sun would expand would be a monumental task. The sun gets colder because it gets bigger, and fusion stops quite soon. But the expanding and cooling cloud of recently-plasma would get here a long time after lack of air had gotten you. Light signals would not get here before eight minutes, and the stuff that used to make up the sun will get here a long time after that. Hours certainly, maybe days. As I said, a very difficult calculation. Need to work out the energy in a unit of plasma, and what it's equation of state is, and so what pressure it will have as a function of density. Then work out how fast it will expand. Very much work.

There would be a huge amount of debris. But most of it will be going (very nearly but not quite exactly) straight out from the sun or the planet it started on. Since there is no gravity, it is highly unlikely that any given chunk gets hit by another chunk. So collisions are unlikely to kill anybody who managed to be in some air tight container of some kind.

The people who might live longest might be those in some self-contained air tight thing that provides air, food, etc. Nuclear subs for example. Not sure it would be judged to be a good thing to be in that situation, since it is highly unlikely to be possible to do anything about it.

Answer 2

Everybody would die quite quickly

Gravity has it's influence everywhere. However you slice it, it is responsible for a lot of vital processes.

The sun and planets are held together by gravity. In the sun this creates such high pressures that the core heats up enough for fusion. If gravity is removed, the pressure holding it together is removed. It's like a container under too much pressure, or an explosive it'll release all pressure. It'll start expanding, trying to equalise the pressure. This will also remove the fusion and heat. In itself not a problem, as the earth is heated by the light, which can take many years after generation to be released from the sun. With the sun expanding, I ecpect much of this light to be released much earlier, bathing the Earth in so much extra light I expect everyone to turn blind if they aren't cooked first like from the flash if a nuclear explosion. Light takes about 8 minutes to reach us. Together with some leniency on the expension, I'll make a ball park estimate that the earth will be destroyed in an hour or so.

However, the earth would be in trouble regardless. Any (counter) pressure generated from gravity would be removed, allowing stuff to expand. With about 1 bar in the atmosphere, it’ll be about the same force it'll push itself off the earth until it reaches equilibrium. The sea is worse. Every 10m the pressure goes up with about a bar. That means that at 100m, the water pressure will suddenly push with 10 var upwards, as no gravity is pushing it and all the water and air on top down again.

Even worse is the ground. A mountain stays where it is because gravity pushes it down. The ground under it pushes with equal force up, giving it equilibrium. If you remove gravity it'll not necessarily explode with such force. However, the mountain will immediately change shape as it's not held down anymore, giving some pressurised material time to expand. If it's a vulcano, it'll be even worse.

I can go on with tectonic plates, magma streams and the iron core of the Earth, but it all comes down to this:

• A planet is only possible because gravity is holding it together. If gravity is negated, the planet will tear itself apart. That is not even considering the spin, which is detailed in a different answer here.

But even if you survive all that, you might get cavitations in the blood because of the pressure difference, creating deep-sea sickness, floating through the thin barely breathable air without food and possibly withing a huge pile of earth or water. I would say most die within the hour, if they're lucky.

Answer 3

It is like asking what would happen if Pi was suddenly 5. Good luck finding that out. Gravity is such a fundamental force of the Universe that by removing it, you practically have a new set of Laws regarding... everything. Not only would the Laws of Physics change, but every law that is even remotly related to something physical would change.

Since Gravity itself is calculated using the Constant G and some other stuff, i am assuming you speak of a Change in that constant. Just look up how many Laws have G in them.

So really, the only answer is "everything is different and probably stops exsisting". We are not talking about Stars exploding or so, stuff might just stop exsisting. If Gravity is gone, you could see Everything just sort of "flipping" to account for the missing force.

So in short, we cant tell. What you could do is look at all the Laws and try to come up with an Answer as to what would happen without Gravity.

Example: The Equation for the Escape Velocity is: v = sqrt(2GM / r). If Gravity is just sort of gone, we are left with v = sqrt(2M / r). So lets say we have a Planet with the Mass 100 and Radius 2. Normaly, the Escape Velocity would be 74.6 Unites. (Calculations without Unites in this case). But without G as a Constant, the Escape Velocity suddenly changes to 10. So around 1/7. Meaning pretty much every single body in the Solar System would shoot out in a line. But even this example is useless because Orbits themself are not a thing anymore. Everything everywhere just shoots of in a line.

And really, the example shows you how flawed it is. So yeah, only good answer is "Everything is different". Maybe with the addition of "To the point where you need to study physics to even come close to understanding it".