# The Naked Scientists Forum

### Author Topic: What is the difference between Mass and Matter?  (Read 8937 times)

#### Farsight

• Sr. Member
• Posts: 396
##### What is the difference between Mass and Matter?
« Reply #25 on: 21/01/2010 17:24:44 »
Sigh...  more nonsense. The reason that E=mc2 cannot be applied to photons is because [the photon], as you eventually point out, [is massless], so of course if you tried to apply E=mc2 to a photon you'd end up with a big fat 0.  It's got nothing to do with whether the photon is 'still' or not.
I'm afraid this really is how it works Lee. It lies at the heart of relativity, is the very basis of E=mc2, and dates back to 1905. It certainly isn't nonsense. If a body emits radiation, it loses mass. That body can be a mirrored box containing photons.

Run the scenario in reverse and trap a photon in a mirrored box, and the mass of the system is increased. Think about the expression E2 = (mc2)2 + (cp)2, and consider the initial photon in pair production. It has no mass, so E2 = (cp)2. After pair production, examine the electron, considering it to have zero velocity with respect to you. Then E2 = (mc2)2. Annihilate the electron and you've flip-flopped back to E2 = (cp)2. Pair production and annihilation demonstrate the symmetry between momentum and inertia by creating and destroying a system called an electron, along with another system called a positron. In such a system, the photon is still moving at c, but it is no longer moving in aggregate with respect to you. Hence its energy/momentum is exhibited as inertia. Mass.

#### LeeE

• Neilep Level Member
• Posts: 3382
##### What is the difference between Mass and Matter?
« Reply #26 on: 22/01/2010 00:55:53 »
Sigh...   a little knowledge...

#### Farsight

• Sr. Member
• Posts: 396
##### What is the difference between Mass and Matter?
« Reply #27 on: 22/01/2010 01:40:31 »
It really is like this Lee. Please refer to a trusted expert on relativity, who will confirm that the mass of a system is a measure of energy content, and a trapped photon increases the mass of the system that traps it.

#### Joe L. Ogan

• Sr. Member
• Posts: 476
##### What is the difference between Mass and Matter?
« Reply #28 on: 22/01/2010 02:08:58 »
I ain't gonna argue with either one of you guys, you are too damn smart for me.  Regards, Joe L. Ogan

#### The Naked Scientists Forum

##### What is the difference between Mass and Matter?
« Reply #28 on: 22/01/2010 02:08:58 »