0
$\begingroup$

To move any stationary object a force has to be applied and applying force needs energy. So how are objects pulled towards each other by gravity without any use of energy?

$\endgroup$
1
$\begingroup$

Your premise that no energy is involved is false. Two point masses, with masses $M$ and $m$, separated by a distance $r$, have a gravitational energy associated with them given by: $$ U=-{GMm\over r} $$

$\endgroup$
  • $\begingroup$ Where does that energy come from? $\endgroup$ – Hark Mar 6 '18 at 5:06
  • $\begingroup$ That energy is gravity. It doesn't really "come from" anywhere: it is just a mathematical way of expressing the fact that objects with mass fall towards each other. $\endgroup$ – Chris Mar 6 '18 at 5:14
  • 2
    $\begingroup$ @Hark Present potential energies, all the energy of the universe , was provided at the original big bang . en.wikipedia.org/wiki/Big_Bang . It is more complicated due to General relativity where energy conservation is not a law, but after nucleosynthesis the models that are based on the standard models of particle , nuclear, and classical physics fit all the data. So the statement "from the big bang" holds. $\endgroup$ – anna v Mar 6 '18 at 5:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.