Photons

[questor]

In thinking about light a few questions occurred to me.

1. since light has mass, how are photons produced? are they everlasting, or do they degenerate into something else?

2. light travels. where is it going? does it stop when it hits an object such as earth, or does it rebound or deflect and continue on?

3. is there a finite amount of light in the universe, or is it constantly created?

4. if light travels, what fills the void as a photon moves by?

5. if the universe is spherical, do the photons move in a circular path so that we may see the same photon twice?

6. if the universe is finite, what happens to a photon when it hits the edge?

[Eclogite]

1. since light has mass, how are photons produced? are they everlasting, or do they degenerate into something else?

I am not sure how the statement since light has mass leads to the question how are photons produced, nevertheless:

 

a) Photons are massless, at least that is the assumption made by most physicists:

A new limit on photon mass, less than 10-51 grams or 7 x 10-19 electron volts, has been established by an experiment in which light is aimed at a sensitive torsion balance; if light had mass, the rotating balance would suffer an additional tiny torque. This represents a 20-fold improvement over previous limits on photon mass.

 

Photon mass is expected to be zero by most physicists, but this is an assumption which must be checked experimentally. A nonzero mass would make trouble for special relativity, Maxwell's equations, and for Coulomb's inverse-square law for electrical attraction.

From:http://www.aip.org/pnu/2003/split/625-2.html

.

:) They are emitted by atoms in a couple of processes. The most common is when an electron shifts from one orbital to a lower energy orbital. It does this by emitting a photon whose energy reflects the difference in energy between these two orbitals.

 

c) Photons do not decay into anything else. They last until they interact with matter by absorbtion or reflection. [some opponents of the Big Bang argue that the observed red shift of light is not a Doppler effect, but is related to decay of light wave amplitude and frequency over time (with a half life of several billion years). This is discussed in this article. http://members.chello.nl/~n.benschop/introduc.htm]

 

2. light travels. where is it going? does it stop when it hits an object such as earth, or does it rebound or deflect and continue on?

It is going nowhere in particular. It travels in a straight line. (Though around massive objects, which distort the shape of space-time, it may appear to curve.) When it strikes an object it will either be absorbed or reflected. I am 99% certain that reflection is just a form of absorbtion: the photon raises an electron to a higher energy orbital. The photon no longer exists. The electron drops back to the lower energy orbital, emitting a photon. To the external observer it appears that the same photon has been reflected.

 

3. is there a finite amount of light in the universe, or is it constantly created?

If the Universe is finite, then there is a finite amount of light, but this amount is not necessarily constant. Light (i.e. photons) is continually being created and destroyed.

 

4. if light travels, what fills the void as a photon moves by?

More void.

 

5. if the universe is spherical, do the photons move in a circular path so that we may see the same photon twice?

If it is spherical the same photon could, in theory, pass us by twice. We could not see it twice, since seeing involves the absorbtion of the photon, so that it ceases to exist.

 

6. if the universe is finite, what happens to a photon when it hits the edge?

It can't. There is no edge, even to a finite Universe.

[arkain101]

A photon is the current name for a wave front of light. It does not carry data, it simply is a form of motion which can be manipulated into data.

 

For example, If I paint a painting of a field and a river with a few birds flying, it is not a real river it is not a real field... It is a massive ammount of light frequencies (color) coming from multiple different sizes of source. When we zoom out and zoom out it becomes an interpratation of an image. The real world can be looked at it this way aswell. A photon does not carry a picture, it can only be interprated in massive quantities with specific frequencies as an image. But all images are interpratations from frequencies of many kinds from things invisible to our vision.

 

It seemed to me that you had confusion in this part.

[Racoon]

I heard that bosons - like photons and pions - carry the interactions between/within the families of particles.

 

Richard Feynman wrapped up all electromagnetic phenomena in Quantum Electrodynamics (QED). with follow up work by Weinberg, Glashow, and Salam.

 

Cup of anti-matter, :)

[anglepose]

Photons must have mass or they would escape the event horizon of a black hole But it is a minute amount of mass.

[InfiniteNow]

Photons must have mass or they would escape the event horizon of a black hole But it is a minute amount of mass.

Some do escape... even with that miniscule mass.

 

Welcome to the site anglepose... enjoy.

 

 

Cheers. :hihi:

[anglepose]

light is pure energy it isnt as such "created" more transformed from another sorce of energy then makes its journey till it hits an object it cannot pass then the photon discharges its energy

[ldsoftwaresteve]

In thinking about light a few questions occurred to me.

1. since light has mass, how are photons produced? are they everlasting, or do they degenerate into something else?

2. light travels. where is it going? does it stop when it hits an object such as earth, or does it rebound or deflect and continue on?

3. is there a finite amount of light in the universe, or is it constantly created?

4. if light travels, what fills the void as a photon moves by?

5. if the universe is spherical, do the photons move in a circular path so that we may see the same photon twice?

6. if the universe is finite, what happens to a photon when it hits the edge?

Good questions. The answers depend on what ends up being true about the nature of matter. I'll come at it from my understanding of McCutcheon's point of view, some stuff I'll just take a guess at and well, see what happens. B)

 

1. Light is made up of configurations of the smallest particles, call them photons for drill. Different colors are different configurations. Light with higher energy is made up of configurations with more photons. Light can degenerate. It can lose photons and we'd see this as a shift toward the red end of the spectrum.

2. Light moves, bounces, can be absorbed and can lose particles. But one thing about its motion is different than the motion of bigger and denser configurations: it seems to move in a frictionless environment.

3. We don't know.

4. Not much in space. Lots in a star.

5. We don't know the shape of the Universe. We don't know how much matter is in it. We don't know how 'long' it's been around. We don't know when matter started behaving with the physical characteristics we observe today. We assume it has always been the way it is now and I think that is a very bad assumption.

6. A photon traveling past the 'edge' of the universe might just act as a new edge to the universe. Space is just space and when it becomes occupied by particles, then it is part of the universe. But this is just conjecture. I don't think we'll every really know. By the time we would get to the 'edge', how could we be sure that something else hadn't beaten us there and was now totally out there even further. Unless, of course, space is something rather than nothing.

[Boerseun]

Photons must have mass or they would escape the event horizon of a black hole But it is a minute amount of mass.

Nope. Light follows the curvature of space.

 

The event horizon at a black hole defines the point where space is curved to such an extent that even light won't escape - regardless of whether the photon has any mass or not.

[Boerseun]

In thinking about light a few questions occurred to me.

1. since light has mass, how are photons produced? are they everlasting, or do they degenerate into something else?

To the best of my knowledge, photons are massless. They are quanta (packets) of energy released as electrons bounce between orbitals, as described above. They are essentially 'everlasting', until they interact with matter, at which point the energy is transferred to the matter the photon interacts with. 'Everlasting' is a relative term - seeing as a photon travels at c, it has no experience of time. The Big Bang and the end of the universe (and all the billions of years inbetween) is one and the same moment to a photon.

2. light travels. where is it going? does it stop when it hits an object such as earth, or does it rebound or deflect and continue on?

It travels in what appears from the photon's perspective to be a straight line. Mass around the universe like stars and galaxies might make the line look a little wonky, but only from a objective observer's point of view. The photon sees it as perfectly straight - even orbiting forever around a black hole.

3. is there a finite amount of light in the universe, or is it constantly created?

Seeing as a photon is a packet of energy, and the amount of energy in the universe depends on mass (the two are interchangeable, essentially two aspects of the same thing) the amount of light in the universe depends on the amount of matter. If the universe has a finite mass, then, yes - there must be finite light. But I don't think you should worry too much about the lights going off anytime soon.

4. if light travels, what fills the void as a photon moves by?

There was nothing in front of the photon, and nothing to take it's place behind it as it passes by. More of the same - nothingness.

5. if the universe is spherical, do the photons move in a circular path so that we may see the same photon twice?

Nope. The universe is expanding at the speed of light, and the photons currently at the edge of the expansion, are the first photons to be emitted by the Big Bang. They should just keep on travelling forever, leaving an expanding universe in their wake.

6. if the universe is finite, what happens to a photon when it hits the edge?

Same as above - the universe is finite right now, if you could freeze the whole thing in place. But it is expanding, so that every second that goes by, the universe inflates radially by 300,000 kilometers. So that even the very first photon to lead the pack can't reach it - they're chasing something that only exist in the minds of men. Beyond the edge of the universe, there's nothing - but there's also nothing to stop a photon from being there. 'Cept, of course, the finite speed of light.

[Erasmus00]

Photons must have mass or they would escape the event horizon of a black hole But it is a minute amount of mass.

 

Not true. You do not need rest mass to be effected by gravity in Einstein's theory.

-Will