General Question

GeorgeGee's avatar

Is it wrong to say that gravity is a kind of energy?

Asked by GeorgeGee (4895 points ) August 21st, 2010

That is technically, as on a physics exam.

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15 Answers

gggritso's avatar

I believe that is incorrect. Energy is defined as the capacity to do work; it is a property of an object. An object may have gravitational potential energy as a result of gravity acting on it, but gravity itself is not energy. Gravity is an interaction.

AstroChuck's avatar

Gravity is a force, as are electromagnetism and the strong and weak nuclear forces. A force is not energy.

Odysseus's avatar

I’m no Sci prof. but I would bet my ass that gravity is energy.
Of course it is energy,
I may be going against ‘science’ here, but they scientists ‘aint vury gud ut englush’. If Gravity is not energy then science needs to redefine the word ‘energy’.
@gggritso “Energy is defined as the capacity to do work”
I jumped out of an aeroplane a few months ago, gravity done its WORK on me sucking me towards her core @ 120mph creating heat /friction and sound . If gravity is not energy then modern science is as retarded as a flat earth state of mind.

Odysseus's avatar

hmm, I see. but as i see it the force was the guy pushing me out of the aeroplane and I felt the energy whilst falling, lol

Vortico's avatar

No. It would be technically incorrect to state that gravity is energy on your exam. However, the force field of gravity can be used to calculate the amount of energy stored as a potential on an object r distance away from another object. Once again, gravity is a field force, so no work can be done unless an external force moves an object away from the path of gravity’s field.

gggritso's avatar

@Odysseus Whoa there. You went and started talking about “work” and now it got all messy.

Just to clarify further: work is defined as a transfer of energy by a force. So yeah, when you jump out of a plane, the force of gravity is doing work on your body by transferring the gravitational potential energy into kinetic energy as you fall. So, that statement was completely correct after all. The force of gravity wouldn’t be doing anything if you didn’t have that potential energy that it could transfer.

Strict physical definitions may not feel intuitive at first, but after a while I found that they work well (haha!) and fit together nicely.

mammal's avatar

it’s not morally wrong, but scientifically you need to be able to demonstrate this concept with some formulaic theory.

Winters's avatar

Science can only descirbe what gravity does but not what it is, so who knows, perhaps it is.

jerv's avatar

I am with AstroChuck on this; gravity is a force, and force is not energy.

FireMadeFlesh's avatar

@Winters We know exactly what gravity is. Einstein told us in 1915 that it is the warping of space-time in response to the presence of mass, and every object falls in a straight line through warped space in the presence of a gravitational field.

hiphiphopflipflapflop's avatar

This gets a bit tricky semantically. There are forces in the common sense, which you could put into a free body diagram and plug into the equation F = m a (note bold letters, these represent vector rather than scalar quantities!). Then there are “forces of nature” in the grander sense which are the general and fundamental means by which particular forces in particular cases come about, the known and well-understood ones being the strong nuclear, weak nuclear, electromagnetic, and gravitational interactions.

Gravity is special among the grand-sense forces in that it acts directly on spacetime itself. A body in freefall doesn’t feel the force of gravity acting on it. The force only becomes apparent when something gets in the way of it following the spacetime geodesic.

Like the other forces, the influence of gravity through space is tabulated by the machinery of field theory. There is an energy density associated with this gravitational field. Interestingly, this turns out to be a negative quantity.

Vortico's avatar

…So in other words, gravity is just as much an “energy” as is inertia.

hiphiphopflipflapflop's avatar

@Vortico I wouldn’t put it that way. One can associate an energy with the influence of gravity in a particular region of space. But gravity is more than just this quantity.

kess's avatar

Gravity is the sum total of all energy in the negative.

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