# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: yamo on 28/02/2010 19:12:49

Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: yamo on 28/02/2010 19:12:49
can e=mc˛ be solved to give a value for t, time and d, space?  what are the values of time and space?

mod edit: Please make your topic titles a question. Because i'm simply gorgeous I have done it for you.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: Bored chemist on 28/02/2010 21:22:36
No.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: flr on 28/02/2010 22:36:00
The relation e=mc2 is valid for any value of t and d.
In other words, it was valid yesterday and so it is today.
It is valid here in my place and everywhere in universe.
Or, if you wish, if I move an object with rest mass m from here to there,
the total energy stored in the rest mass will still be e=mc2.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: LeeE on 28/02/2010 23:45:06
Umm.. e=mc2 is not valid for any value of t & s (where s= displacement) because the result of s/t must always be <= 'c'

However, t & s are just different qualities of space-time, where t can be equated to s, so you essentially end up trying to deal with s/s.  The difference between s & t is really just down to our point of view.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: JP on 01/03/2010 02:44:54
E=mc2 just tells you how to relate mass and energy for a stationary object (one that isn't moving) at a single point in space-time.  It's valid for any single point in space-time that you want to choose, as long as the object isn't moving, so that you can't tell the exact position and time just by looking at the equation.

By the way, the full equation is E2=m2c4+p2c2,
where p is momentum, which tells you about how the object is moving in space.  This is usually the one you want to use, since it's valid no matter how fast you or the object is moving.  If the object isn't moving, p=0 and this equation becomes E=mc2.

Edit: to fix a sign error.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: yamo on 01/03/2010 06:18:08
well c is a velocity delta d over delta t.  so what i am looking for is a definition for t or d in terms of e and m.  mebbe the limit as delta t(or d) approaches 0.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: JP on 01/03/2010 06:55:14
If you care about velocity, which is delta d/delta t, then you can get it from the energy and momentum: v=pc2/E.  You can't get position of time themselves because the equations are valid at any space-time point you want to choose, so there's nothing to tell you which one you're using.
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: Ron Hughes on 01/03/2010 15:08:42
Try working with this one,  M = hf/c^2
Title: can e=mc˛ be solved to give a value for t, time and d, space?
Post by: Farsight on 02/03/2010 00:24:58
Yamo: no, you can't "solve" this. That's because c is just a conversion factor between our measures of space and time. It's the speed of light, so it's a speed, which is distance over time, and both of these measures are defined using light.

JP: pair production and annihilation demonstrates a kind of "flip flop" between the p2c2 and the m2c4