The magical creation of the photon.

[CraigD]

If I calculate the mass of a gamma ray it turns out to be 2.21 X 10^-30 kg. It's relatively close to the mass of the electron at 9.11 X 10^-31kg. Someone check my numbers on the mass of the gamma ray please.

Your result looks OK to me.

 

From [math]hv = E = mc^2[/math], [math]v = \frac{mc^2}{h}[/math].

 

So, given a mass of [math]m=2.21 \times 10^{-30} \,\mbox{kg}[/math], I get a frequency [math]v=3.07 \times 10^{20} \,\mbox{hz}[/math] (307 EHz), which is near the top of the gamma band of EM radiation, and, as best I understand, about as high a frequency photon as can be produced by any known physical phenomenon.

Since gamma rays are EMR and travel at c, would they not be massless (or a rest mass of zero [M₀])?

Yes. The rest mass of a photon, regardless of its frequency, is, according to best theory, zero.

 

What LB has calculated is the relativistic mass of the photon.

 

As various folk have pointed out, this is a rather weird calculation, since according to Special Relativity,

[math]m = \frac{m_0 c^2}{\sqrt{1-\left(\frac{v}{c} \right)^2}}[/math], leading to a mathematically nonsensical [math]m = \frac{0}{0}[/math].

 

Nonetheless, as best I understand the theory involved, photons should interact with massive bodies gravitationally. However, even the most energetic photons, such as the one in LB’s calculation, has only a tiny mass, and thus has only a tiny gravitational effect.

 

Since photons don’t obey Fermi-Dirac statistics, however, one can in principle pack an arbitrarily large number of them in an arbitrarily small volume (uncertainty being significant, not truly an arbitrarily small volume, but this isn’t in principle a significant limitation), so, given sufficiently energies and optics, it may actually be possible to confirm these predictions experimentally.

[Little Bang]

M=hf/C^2, gamma ray frequency of 3 X 10^20, Planck's constant of 6.636 X 10^-34. Photons (EMR) have zero rest mass but they are never at rest. Does anyone know the average frequency of detected gamma rays? I used the highest frequency on the chart and was surprised that the calculated mass was greater than the electron.

[freeztar]

Craig, thanks for the clarification regarding relativistic mass (and the problems associated with the theoretical determination of it in regards to photons).

 

I'm aware of the experiments performed in an attempt to prove/disprove GR using a distant star and the sun to show that the light was slightly bent by the gravitational influence of the sun. So, obviously, I should have known better.

 

I used the highest frequency on the chart and was surprised that the calculated mass was greater than the electron.

 

This is surprising, for me, intuitively.

If an electron-positron annihilation can emit a gamma ray that is more massive than the electron, then where does the extra mass come from?

[Little Bang]

Good question Freez. You would think that each of the two gamma rays should have the same mass as the electron. That implies there is something wrong with my logic.

[Qfwfq]

If an electron-positron annihilation can emit a gamma ray that is more massive than the electron, then where does the extra mass come from?

From the kinetic energy of the electron and positron.

 

This whole thing is confusing because so many people insist on outdated terminology which is misleading. What so many still call "relativistic mass" is really just total energy, mass is synonymous with rest energy and there is no difference between mass and "rest mass". It is equivalent to say:

 

• The photon has zero mass
  
• The photon has zero rest energy
  
• The free photon's energy is purely kinetic
  

[Moontanman]

I'm not sure if this has anything to do with this but an intense energy feild like say a black hole radiates electron positron pairs. there are other exaples but I'm eating and I can't think of them right now. But it does mean energy can condense into matter.

[Little Bang]

Gamma ray's frequencies lie between 3X10^18 & 10^20Hz. So the annihilation would produce gamma rays with the correct (calculated) mass.

Moon that's a good point but I'm not sure that it counts. First I have no way of going to a black hole to check Hawking's prediction. Second virtual particles are theory, as far as I know none have ever been detected directly.

[Moontanman]

Gamma ray's frequencies lie between 3X10^18 & 10^20Hz. So the annihilation would produce gamma rays with the correct (calculated) mass.

Moon that's a good point but I'm not sure that it counts. First I have no way of going to a black hole to check Hawking's prediction. Second virtual particles are theory, as far as I know none have ever been detected directly.

 

Check this out, matter actually made from an energy feild!

Scientists Use Light to Create Particles

[Little Bang]

good article Moon. The experiment appears to confirm the equation we've been using.

[Qfwfq]

...they had created two tiny specks of matter -- an electron and its antimatter counterpart, a positron -- by colliding two ultrapowerful beams of radiation.

As may be expected from quantum field theory. It's an interesting demonstration of slight non-linearity of EM in vacuo, at high intensity.

 

BTW virtual particles have never been detected directly because the moment you detect them they are not virtual. :phones:

[Little Bang]

The photon (carrier of the electromagnetic force) interacts ( in some unknown way) with the electron and knocks it into a higher energy level, it then falls back to it’s original energy level and emits a photon with the same energy. Another possible method. A hydrogen atom collides with another atom. The resulting collision accelerates the proton and electron of opposite charge in the magnetic field that permeates all of space. This acceleration creates an electromagnet wave (EMW with electric and magnetic components ) in that field . If that EMW passes through the space occupied by another hydrogen atom that atom produces another EMW of equal energy. I'm no sure what a comparison of the spectrum of hydrogen and deuterium would show but it's possible that it could prove or disprove my idea. The extra mass baggage of the neutron should cause a drastic change.

[Little Bang]

Craig used the equation M=hf/C^2 to calculate the mass of a specific photon. I think the real significance of it as f=MC^2/h is more important because it implies that at the right frequency we could produce an electron positron pair which apparently has just recently occurred. This suggests at the right frequency we could also produce an electron proton pair. The creation of the electron proton pair shows that the magnetic and electric components of electromagnetic radiation can be turned into a positive and negative charge. Don't these items taken together show that we need to rethink our understanding of the atom?

[Qfwfq]

This suggests at the right frequency we could also produce an electron proton pair.

You can get particle-antiparticle. Electron and proton aren't antiparticles of each other.

 

The creation of the electron proton pair shows that the magnetic and electric components of electromagnetic radiation can be turned into a positive and negative charge.

So would the electron-positron case, they have opposite charges, but there are no grounds to associate them with electric and magnetic fields.

[Little Bang]

No grounds to associate them except two waveforms that are electric and magnetic produce two particles of opposite charge. Ok I guess there is no reason to associate them.

[Little Bang]

 

 

To the best of my knowledge, what we lack experimental evidence for is another major theoretical prediction: that photons exert gravitational force, as opposed to only experiencing it, of which we do have ample, clear evidence.

 

For example, a single photon of visible light ([math]5 times 10^{14} ,mbox{hz}[/math]) passing a single hydrogen atom at a distance of 1 cm should be accelerated by about [math]10^{-46} ,mbox{m/s}[/math] – an undetectably small but physically real amount.

 

Craig would it be possible to use this,

F=G[{(hf/C^2)sub1(hf/C^2)sub2}/r^2]

[Little Bang]

The relationship between frequency and matter that we have discovered, (and I say we because I would not have thought of it without the discussions of the members) needs to have some meaning with respect to our observations. Therefore I am going to take a stab at explaining how the concept could show the evolution of the universe.

Some event, and we can’t know what that event was, caused a vibrating point to form with infinite frequency. That point began to expand at C and the wave length started to get longer. When the frequency became equal to the frequency of the proton, using the equation f=MC^2/h, all of the protons that we see today formed. and immediately started rushing away from each other because of their charge. The universe continued it’s expansion until the frequency was equal to that of the electron at which point all the electrons formed. Then they united with the protons to form hydrogen and gravity switched on. The resulting collisions between the hydrogen atoms created the light elements and from there we went on to stars and galaxies.

The first question that pops to mind is why wouldn’t anti-protons and anti-electrons form and I think if they did why wouldn’t they have exactly the same number as protons and electrons and annihilate the entire universe. Maybe the event that started our point started another point that became an anti-matter universe.

[freeztar]

Interesting thoughts LB.

 

Question: Why wouldn't gravity "kick in" when the protons formed? Why would it "wait" for hydrogen?