You need energy to produce a force that compensates gravity. So if you apply that force for a huge amount of time, will gravity ever be depleted?
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You don’t need energy to compensate gravity. If a rock lies on a table it doesn’t consume any energy to stay up there. Only moving further up takes energy.
You do not need energy to create a force. Energy is expended (or reversely: freed) when an object is moved by a force for a distance. A stationary object with forces acting upon it is energy-neutral.
You’re referring to gravitational potential energy, which is made from the kinetic energy used to move something into a useful position, it’s not infinite for the same reason that a rubber band snapping back isn’t infinite, eventually you will get to a resting position.
Mass is energy. You cannot create or destroy mass/energy. What happens is that when two objects attract each other and meet, other forces within the masses (nuclear, electromagnetic) negate the acceleration of gravity, and the system settles into a basicslly static energy state.
Remember to, that objects in gravitational free fall experience no force. Time gradients that surround all masses change the path through spacetime that objects follow, which gives the illusion of attraction or acceleration . But what actually happens is that the spacetime curvature the objects follow bend until they meet. Only when the objects meet do forces manifest and exchange energy.
Even an apparently motionless object follows a path through spacetime.
So to answer your question directly, yes, gravity requires energy, which it has by virtue of the fact that mass is energy.
Eventually entropy will cause all mass/energy to disperse.
Applying a force only requires energy if that force moves something (or at least pushes along the way something is moving). Think of setting a mousetrap. The spring will be applying a force on the bar, but until the trap is triggered, the bar will stay held in place. It can stay like that forever; there’s no battery to recharge or key to wind until the bar is actually released. Then, since the spring is *moving* the bar, the spring’s energy is released.
Same thing with gravity. Gravity might be pulling on a rock, but unless the rock is moving up or down, no energy is being stored or released by gravity.
You do not need energy to produce a force that compensates gravity. A table does not use energy when it prevents your dinner plate from crashing onto the floor. Energy is force times distance. So you need energy to lift something up against gravity because you are moving it across a certain distance. But you do not need energy to keep something stationary, even if you need to use a force to do this.
The confusion comes from peoples own experiences. Even though you do not put energy into holding on to something your muscles need energy in order to generate that static force. This energy does not get converted into the object you are holding but end up as heat in the muscles.
If you hold an object at a certain height, you are holding potential energy. As long as that object remains at that height, that potential energy never changes, even if you hold it there forever. You are not considered doing any work on it, no longer how long you hold it.
No. In order to use the energy that potential energy from gravity can provide, that object must first be “raised up” by other forces, which requires energy. Since transfer of energy is not 100% efficient, some of the energy will be lost to heat etc, preventing the creation of a perpetual motion machine.
Potentially. Gravity goes on forever but gets weaker with distance as it goes out in all directions. So the farther from the gravity source the less energy you need to keep going further, but the less energy it exerts on you as well. Assuming am infinite expanse of just a gravitational body and something with energy to go away from that body, you will always feel gravity on into infinity.
I think it’s important to clarify what energy is. You do NOT need energy to compensate gravity. A force diagram of the computer on your desk right now would show: gravity pointing down, and the “normal force” pointing up the exact same amount. The “normal force” seems like a weird force – how can it be exerting constant force without expending energy? For that matter, how can gravity or magnets do this too? It’s because force is VERY DIFFERENT than energy. Force gradients (like gravity from a planet) can exist in a steady state. Then objects can move up and down the gradient, and in so doing expend or release energy. But the gradient itself doesn’t require energy to maintain. The “normal” force I mentioned is actually simply the force exerted by objects that don’t want to be in the same place at the same time. Call it the Pauli exclusion principle if you want to sound fancy. But that tendency of nature to not let most things be in the same place at the same time is expressed as a force when you try to smoosh two things into the same place, like gravity.
So you’re left with gravity, a force gradient with no energy requirement, and the fact that your computer and desk can’t be in the same place at the same time (which can also be expressed as a force gradient, since they’ll push each other away harder if you try to smoosh them closer together), and they find their balance and there your computer sits.
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