Naked Science Forum

On the Lighter Side => New Theories => Topic started by: talanum1 on 12/02/2021 14:32:38

Title: Why is energy positive?
Post by: talanum1 on 12/02/2021 14:32:38

For massless particles we have:

E^2 = (pc)^2.

This has solution:

E = +/- pc.

So why does nature choose only positive values?

This is at odds with:

E = |p|c.

Title: Re: Why is energy positive?
Post by: Bored chemist on 12/02/2021 21:14:55

It doesn't.
What you get isn't an absolute energy, but a change in energy (associated with a change in mass).
And a change in energy is positive or negative depending on which way you look at it.

Title: Re: Why is energy positive?
Post by: talanum1 on 19/02/2021 15:30:37

Quote from: Bored chemist on 12/02/2021 21:14:55

And a change in energy is positive or negative depending on which way you look at it.

That's not compatible with:

E = |p|c

even if p is change in momentum: "sizeof a vector" is always positive.