Im actually not a very good at physics, but I was playing with this functions (just for fun and education, so this question might end at the Scifi forum), and would like to know if this logic is wrong(or right):

  1. $E=mc^2$ --> $E = m(r/t)^2$ --> $t = \sqrt{\frac{mr^2}{E}}$

  2. $F = G\frac{m_1m_2}{r^2}$ --> $r^2 = \frac{Gm_1m_2}{F}$

Is it possible to state something like $t = \sqrt{\frac{(m_1+m_2)Gm_1m_2}{EF}}$ ?

  • $\begingroup$ It's really not clear what you think these expressions mean. I assume $r$ is some distance? Distance from what, to what? What would that last expression mean? It relates some time interval to a function of two masses, an energy, and a force. What force? which masses? The energy of what? $\endgroup$
    – Colin K
    Commented Jun 4, 2012 at 14:38

1 Answer 1


In the first equation $r$ is the distance light would (hypothetically) travel in a vacuum in a span of time $t$. In the second equation $r$ is the distance between two point masses. So the third equation would make sense, I guess, if you shot a single photon between two point masses separated in a vacuum by a distance $r$ with exactly total energy $E$ and gravitational attraction $F$ and wanted to figure out the time $t$ it would take for the photon to close that distance, but you have no idea what the speed of light in a vacuum ($c$) is.

This is the sort of equation someone would come up with while on a bad acid trip.

Is there anything you'd like to tell us?


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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