A question about gravity and photons

reply to post by Moduli


mo·men·tum/mōˈmentəm/
Noun:
The quantity of motion of a moving body, measured as a product of its mass and velocity.

Light or Photons do not have mass thus they cannot obtain momentum.

Gravity effects Light or Photons in the sense that Light with travel the SPACE/TIME CURVATURE created by a Celestial Bodies Gravity Well. In a Black Hole...Light will travel such a great curvature that Light will be directed into a Black Hole and never escape.

Split Infinity

text·book [tekst-boo k]
noun

a book used by students as a standard work for a particular branch of study.

edit:
Hint: Also c.f. the complaint in the other thread on syntax!

syn·tax [sin-taks]
noun
1.
Linguistics .
a.
the study of the rules for the formation of grammatical sentences in a language.
b.
the study of the patterns of formation of sentences and phrases from words.
c.
the rules or patterns so studied: English syntax.
d.
a presentation of these: a syntax of English.
e.
an instance of these: the syntax of a sentence.

I would like to thank everyone for their time and patience with what may be obvious for you all but still new and fascinating to me. Have to head off to work but will pick this up later.

Again, a humble thank you.

Originally posted by beezzer

Originally posted by OccamsRazor04

Originally posted by beezzer
reply to post by CLPrime

 

If photons have momentum, does that mean they accelerate?

PS, thanks for the answer.

Photons do not accelerate. They have a set speed and they begin and start at that speed (only the medium they travel through alters it). Their behavior is counterintuitive in fact. Imagine for a minute you are on a train going 30mph and throw a baseball 10mph. The ball will be going 40mph correct? So what happens when you shine your flashlight? It should go the speed of light + 30mph like the ball right? Seems like we just found a way to break the speed of light! Only it doesn't. The speed of the train does not impact the speed the light goes. So if you had a train going 5 mph less than the speed of light and you turned the flashlight on, the light coming out would appear to only be going 5mph! Kind of mindblowing.

As others have pointed out, photons have no rest mass.

edit on 31-10-2012 by OccamsRazor04 because: (no reason given)

Now THAT is a brilliant concept!

Very glad I could help! Now here is something to think about .. nothing can accelerate to the speed of light. What happens when you are on a vehicle going JUST under the speed of light and then you throw something?

I don't have the answer.

reply to post by beezzer


Oh crap! Someone has been going to school.

This can't end well.

Originally posted by CLPrime
reply to post by chr0naut

 

It depends what's meant by "collects." Any material "collects" photons to some extent when electrons in the material absorb them. When this happens, the material does gain mass. That's the exact opposite of what happens when a flashlight converts electricity to photons that are then released, causing a reduction in the mass of the flashlight.

You cannot sensibly apply mass/energy equivalence to Photons as they are constrained from expressing their energy as mass. At the speed of light, the mass of the Photon is too small to be detected. At rest, the mass MUST be even smaller.

If Photons had any mass, they simply could not travel at the speed of light. If they could not travel at the speed of light (I'm talking propagating in a vacuum, here. I am aware that light propagation by absorption/emission can be very much slower), then they would not be Photons. The equations are clear and supported by observation and experiment.

Even from a quantum view (and remember that a Photon IS an indivisible, fundamental, quantum entity), the Photon is constrained from having a Higgs field interaction.

It is a nonsense and misleading to say that Photons have mass (even a "relativistic" one), so I must disagree, sorry.

reply to post by beezzer


Well, its another day so thought I'd take a look to see how this thread was going.

Go on Beez, ask another question

Nice thread going on beezzer! I double-dare you to ask about the shape of a photon

I'm just throwing this in .....


Chapter 9.6 of "Principles of Physics, A calculus based text." 4th edition, by Serway & Jewett, is titled; "Relativistic momentum and the relativistic form of Newton's laws".

Chapter 9.7 is titled "Relativistic energy".

Light, is not a particle travelling at speed of light. If it was, it would answer to E=mc^2 and have mass. Instead, it's a particle that shakes ... you can make an electron, do the same thing ... shake, until it emits light ... but we measure light in waveforms.

This paper is like eating ice cream. Science may have been rigorous, at one time but that is long gone in the mainstream. Scientists work for TPTB and produce what they are told to. Science has become a religion.

www.gsjournal.net...

reply to post by chr0naut


Apparently, I need to remove "relativistic mass" from my vocabulary. Am I the only only who understands that this "mass" is not truly mass but a colloquial way of referring to the momentum gained by a photon (and any other object at or approaching the speed of light)? I even said so in my original post in this thread.

Need I mention again that I was leading to the complete form of "E=mc^2"? My mistake was I didn't anticipate being hijacked. In my second post, I wrote out the process of getting from standard momentum to photon momentum through E=mc^2, giving p = E/c. This is the second half of the equation, rearranged. Had I been allowed to follow this through, I was fully intending to put the two together and make it clear that photons have momentum but no mass.

So yes, you're right, photons have no mass, ever. I never said they did.
The post of mine that you're quoting is dealing with the absorption of photons by a material. When that happens, the material does gain mass, as the photons have added energy to electrons in the material.

Originally posted by Moduli

Originally posted by CLPrimeMy implication was that "relativistic mass" is illusory.

It's not "illusory" it's false. It's like trying to "simplify" an explanation of a disease by describing it as an imbalance of humors. It's indefensibly wrong.

Its actually not false, just a lot of controversy surrounding it.

en.wikipedia.org...


Why are you putting up definitions about text-books?

Originally posted by CLPrime
reply to post by chr0naut

 

Apparently, I need to remove "relativistic mass" from my vocabulary. Am I the only only who understands that this "mass" is not truly mass but a colloquial way of referring to the momentum gained by a photon (and any other object at or approaching the speed of light)? I even said so in my original post in this thread.

Need I mention again that I was leading to the complete form of "E=mc^2"? My mistake was I didn't anticipate being hijacked. In my second post, I wrote out the process of getting from standard momentum to photon momentum through E=mc^2, giving p = E/c. This is the second half of the equation, rearranged. Had I been allowed to follow this through, I was fully intending to put the two together and make it clear that photons have momentum but no mass.

So yes, you're right, photons have no mass, ever. I never said they did.
The post of mine that you're quoting is dealing with the absorption of photons by a material. When that happens, the material does gain mass, as the photons have added energy to electrons in the material.

Thanks you for your admission, and now one from me: I have also spoken of 'relativistic mass' in the past. It is a really convenient way to explain aspects of the Photon, without getting in to some longer and more complex definitions (a bit like the rubber sheet analogy - it helps in most cases but can also be a bit misleading if taken literally).

and I'm also in agreement that Photon energy is free to be expressed as mass once the speed of light constraint is removed (as in the Photoelectric effect). The actual mass, though, is usually very small in the scheme of things.

reply to post by beezzer


No, photons dont have mass.

Photons are not actually "affected" by gravity. Light propagates in empty space, large bodies compress or some say curve space. Since photons propogate in empty space they follow the curvature of space. It is not that gravity pulls on the photons, its just that photons follow the curved path through space. Hope that makes sense for you

reply to post by beezzer


I should also add, photons can eject electrons if they have the required energy, but the ejection of the electron is not due to a physical collision as such, rather the photon is kind of consumed for a time by the electron which then changes its orbital. The orbital change depends on the photons frequency. A high energy photon can energise an electron to the point at which it breaks free from the nucleus.

This got me thinking. How can some matter (ejections) escape from a black hole, while light typically falls in? Does this mean the ejected matter is moving faster than the speed of light? Your thoughts.

reply to post by Oannes


High-energy particles don't escape from inside black holes, they are actually ejected from near the event horizon at the poles. Black holes tend to rotate rapidly, generating complicated magnetic fields. These magnetic fields accelerate particles along the axis of rotation, forming particle jets.

Other particles theoretically escape via Hawking (black body) radiation.

Originally posted by VoidHawk

Has anyone seen those little rotating thingys inside what looks like a lightbulb? They have 4 little...reflecters?...that spin around when they are hit by light. One side of each reflecter is white and the other side is black. I always assumed it was light that caused them to spin but the fluffy ones question now causes me to doubt that, so what dDOES make them spin?

That's a Crookes Radiometer -

en.wikipedia.org...

Also worth looking at the Nichols Radiometer, which has proved light can produce a force via mechanical collision over 100 years ago:

"The fact that electromagnetic radiation exerts a pressure upon any surface exposed to it was deduced theoretically by James Clerk Maxwell in 1871 and Adolfo Bartoli in 1876, and proven experimentally by Russian physicist Peter Lebedev in 1900[1] and by Ernest Fox Nichols and Gordon Ferrie Hull in 1901.[2] The pressure is very feeble, but can be detected by allowing the radiation to fall upon a delicately poised vane of reflective metal in a Nichols radiometer (this should not be confused with the Crookes radiometer, whose characteristic motion is not caused by radiation pressure but by impacting gas molecules)."

See Radiation Pressure:
en.wikipedia.org...

Current theory wants to forget those types of experiments because giving mass to photons breaks many of the equations of the Standard Model. The reason mass is not given to photons in current theory has nothing to do with the physical properties of light - it has to do with fulfilling the requirements of the current set of (erroneous and heuristic) equations dealing with the innate motions of photons.

IMO photons do have mass, because my current (unorthodox) understanding is that photons are a spinning particle, and not some some crazy spooky dualistic wave particle. I don't really expect anyone to agree though.

reply to post by yampa


Thanks for the reply
I know very little about this subject but I'm always pleased when someone like you comes along offering new theories, thats how we progress