Re: Is there a definite amount of moving mass for photons?

Hi Paul,
Good question. The best answer I can give involves a lot of high order 
mathematics (which I'm sure you don't want) so I'll try my best without, I 
am open to correction from field specific experts.

Properties of moving mass are as you suggest, momentum, kinetic energy, 
velocity, mass. 
Calculate the above using the frequency/energy of the photons from: 
velocity (3*10^8 m/s) equals frequency divided by wavelength
energy equals plancks constant times frequency
e.g. 100keV photons from an X-ray tube
then use the formula e=mc^2 to get a "mass" the mass you calculate is the 
mass of the photon only while it is travelling at exactly the speed of 
light.

The concept of "moving" mass stems from relativistic effects which become 
more noticable as velocity approaches c (velocity of light). For example:
measure the mass of a 1kg rock "at rest" then put the rock in the Concorde 
for a supersonic trip to Paris and measure the mass of the 1kg rock "at 
2500km/h" relative to yourself (who stays in Seattle), you will find 
virtually no measurable difference even though the rock is actually a 
poofteenth heavier at the fast velocity, the change in mass was so small 
you were unable to measure it. Now put the rock in a spaceship which can 
travel at 0.95*c (10.4*10^8km/h) and measure the mass (from earth where you 
stay). You will find the rock has about 10% more mass than before! It now 
weighs 1.1kg! If you make the rockets' speed even closer to that of light 
(0.99*c) the mass will be even more. Maybe 2kg. If you can make the rocket 
travel at exactly the speed of light the rock will weigh infinity kg's.

Now forget we are talking about a rock. What if we do the same experiment 
with a "photon" (a small packet of electromagnetic waves). We know that an 
electromagnetic wave has zero mass since it is just the fluctuation of an 
interconnected electric and magnetic field. But put a small group of them 
together and speed them up to the speed of light, then what used to be zero 
mass would increase by an absolutely huge amount and the "photon" would end 
up having some "mass".

Since we now have a "photon" with mass and momentum and kinetic energy and 
velocity, we should be able to aim it at an object and when it strikes the 
object it should "push" the object. Have you ever seen a "radiometer"? Have 
you ever felt the warmth of the suns' rays? Have you ever seen a car with 
"sun beaten" paintwork? How about a solar cell for producing electricity to 
drive a car? Isn't that just some photons pushing a car?

Photons are usually associated with an unstable high energy system 
giving off some excess energy to move to a more stable "low energy" 
state. I'm sorry but I can't explain the process of creation of a photon. 
All I can do is provide examples of systems which create photons.
White hot tungsten filament in a vacuum (light bulb).
Strong magnet on a spinning object (alternator, electric motor).
Fast electrons striking a heavy metal target (X-ray machine).
Human cellular biochemical reactions (heat/infa-red radiation).
Exothermic chain reaction oxidation of hydrocarbons (burning wood).
Thermonuclear reactions (sun H2+H3=He4+n).

Hope this was some help.
Regards
Ant
a.barber@qut.edu.au

[Moderator Note;  Here are some related articles on this subject from our Mad 
Scientist Archives:

References compiled by P. Barmby


Momentum and Photons


More on Energy and Mass

]