# Energy And Rest

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### #1 hazelm

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Posted 20 February 2019 - 07:19 AM

Question:  Does everything - even at rest - have some energy?

### #2 hazelm

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Posted 20 February 2019 - 08:32 AM

Yes it does.

If it has any heat in it, it has thermal energy. Even if it is not moving it has rest mass, https://www.physlink...perts/ae161.cfm . There are loads of forms of potential energy which are derived from stationary things. Think Batteries, hydro electric damns etc, until someone throws the switch they are at rest, but can release lots of energy. Coal produces power by burning fossil fuels that havent moved for millions of years etc etc

Good Question

Thank  you.  I beg your patience because I am going somewhere with this.  But I'm going stumblingly.  Question:  Does a photon allegedly have no rest mass because a photon is never at rest?  It starts its existence moving?

Maybe I can speed this up.  E=mc2.    Energy = Mass times speed of light (velocity) squared.  If a photon has no rest mass, then in this equation, Mass = 0.  Now we have E = 0 times x 186,000 squared.  Therefore, in the case of photons, Energy = zero.  In other words, in the case of this equation, photons have no energy because zero times 186,000 = zero.  But we know photons certainly do have energy.  They came into existing moving.

And is this why Einstein found it necessary to create a special equation for photons?  Photons were/are never at rest.  They start their existence moving - at, of course, their own light speed.

Does that make sense?  I know I repeated myself a bit there but I think I got it.  I am not sure special relativity would even apply.  Buy that is another question that I will leave at rest for now.

### #3 hazelm

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Posted 20 February 2019 - 09:26 AM

You are using the pop science E=mc2 the full equation has a pc term with p = inertia c speed of light. Photons have inertia.

Here is utube link explaining it

He is going faster than the speed of light.  I can't follow that fast.  :-(

That said,  I had tossed out all the other things to talk about photons because of my thoughts about Einstein creating a special equation for photons.  Now I see why.  But I am still at everything else having zero energy because of that (pop) equation.  I'll go looking for the rest.  I'd never heard of that.  Thank you again.

### #4 Dubbelosix

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Posted 20 February 2019 - 03:23 PM

Yes Hazel, but an intricacy to remember is that rest is an approximation, rest is really the motion of a system in the ground state.