# Is energy required for gravity to have effect, or is it an energy itself?

If magnetism requires some energy to exert change of motion to attract ferrous metals, then, does gravity require energy to exert attraction, or is gravity energy itself, creating attraction through centrifugal force from the earth?

• There is a question on physics.stackexchange.com/questions/75222/… that is similar to this, with the top answer most relevant. Here's a quote that's particularly relevant: "When you do work against gravity, you store energy in the gravitational field as gravitational potential energy, which then gravity uses to do work on that object." – Dean Jan 23 '17 at 11:32
• This is a physics question, not astronomy. recommend migration – Carl Witthoft Jan 23 '17 at 13:28
• Okay, thank you for this. Therefore, do I close the question? – Declan Jan 25 '17 at 16:43
• I'm voting to close this question as off-topic because physics question – James K Jan 26 '17 at 22:22

Gravity is an effect of the stress-energy tensor. Put differently, energy and momentum (they're related concepts) are the cause of gravity in general relativity. A fully charged electric battery has a very slightly stronger gravitational field than a depleted one. You may have heard that $E = mc^2$ or in as the terms are more descriptively defined in modern usage, $E^2 = m^2c^4 + p^2c^2$ . Just thinking about these equations from special relativity, you can see that more energy means more mass, which means more gravity.