[neutralino]

Originally Posted by dipayankar I think photon has mass. I really need to dig into it and find out if I am right...

Originally Posted by Lakshya Look, we are talking about the rest mass of photon and not the mass of photon. The mass of photon can be derived from the calculations of relativity but a particle to be able to travel at the speed of light then it should be massless.

Let's get the standard terminology correct here. Nowadays physicists use the term mass to mean the invariant/rest mass, even when talking about relativity. Whenever anyone talks about any other type of mass they need to use a different term; i.e. relativistic mass, or frame dependent mass.

dipayankar; the mass of a photon is zero. This is a result of special relativity, a theory that has held up under heavy scrutiny for over 100 years. There is nothing for you to "dig into" on this matter.

[dipayankar]

Light is photon. So when in rest (which is hypothetical) photon will evaporate, because the basic property of photon is motion. However having said this, there has been a case when photon has been stopped in the tracks in a Bose - Einstein condensate. I need to find out if they tried measuring the mass of the stopped photon..

Originally Posted by Lakshya Look, we are talking about the rest mass of photon and not the mass of photon. The mass of photon can be derived from the calculations of relativity but a particle to be able to travel at the speed of light then it should be massless.

[Profpat]

Was it stopped Dipayankar? I thought it was just really slowed down, Oops I shouldn't say slowed down just a whole lot of interaction with the medium.

Do you have the site I can view?

Thanks,

Pat

[neutralino]

Originally Posted by dipayankar Light is photon. So when in rest (which is hypothetical) photon will evaporate, because the basic property of photon is motion. However having said this, there has been a case when photon has been stopped in the tracks in a Bose - Einstein condensate. I need to find out if they tried measuring the mass of the stopped photon..

Note that, in Bose-Einstein condensates, the speed of light may appear to be slowed, but the actual speed of a photon does not change.

Here's the abstract to the article. For the full article, one would need to subscribe to Nature.

[Profpat]

[quote=neutralino;39901]Note that, in Bose-Einstein condensates, the speed of light may appear to be slowed, but the actual speed of a photon does not change.

Here's the abstract to the article. For the full article, one would need to subscribe to Nature.
[/quote

Thanks Neutralino for the abstract site. Once again you are very helpful.

Best,

Pat

[NotStein]

Originally Posted by Profpat Hi Lakshya and Neutralino; No offense taken here I know I am as dumb as a door knob. I'm like Sgt. Schultz " I KNOW NOTHING " But for your own enlightenment Lakshya, Neutralino is absolutely correct. It's not nice to insult people. If you only learn that at this forum you would have learned a lot indeed. Best to all, Pat

I can respect anyone that starts from the point of being 'dumb as a door knob'. It is the root point of all wisdom; all new paradigms start from this common point. Look, we're all passionate about our common interests, and passion is a strong emotion. We all get both estatic and irate about what we read here, and hold our own beliefs and visions dear. End result? We'll whack each others'extremities off at times; If you've read any histories of our common scientific discipline/endeavor, we're in pretty good company - Einstein & Bohr, Sandage & everybody else, & what about poor old Hans Alfven (gooood read; google him) - they certainly had their moments,often times not being able to even share an auditorium together. As long as can keep from taking it too personally & holding grudges (like some of them did, even for years), we can share our passions on both sides of the emotional aisle. Passionate dialogue, often emotionally distressing, is often responsible for the new insight/paradigms we experience.

Flame On!

Jeff

[NotStein]

[quote=Profpat;39928]

Originally Posted by neutralino Note that, in Bose-Einstein condensates, the speed of light may appear to be slowed, but the actual speed of a photon does not change. Here's the abstract to the article. For the full article, one would need to subscribe to Nature. [/quote Thanks Neutralino for the abstract site. Once again you are very helpful. Best, Pat

But in glass it does, otherwise a prism wouldn't work; water, too, otherwise spearing fish would be much easier. Different configurations and densities of matter (mass, and therefore energy, too) affect the speed of photons. Wouldn't then the configuration/density of the fabric of space be responsible for fixing the universal speed of photons (C)? If not, what would (something does). Or are you saying that all of this is simply due to curvature, and velocity remains constant?

Jeff

[neutralino]

Originally Posted by NotStein But in glass it does, otherwise a prism wouldn't work; water, too, otherwise spearing fish would be much easier. Different configurations and densities of matter (mass, and therefore energy, too) affect the speed of photons. Wouldn't then the configuration/density of the fabric of space be responsible for fixing the universal speed of photons (C)? If not, what would (something does). Or are you saying that all of this is simply due to curvature, and velocity remains constant? Jeff

Note my careful use of words in the above post. I said that the speed of a photon does not change, whereas the speed of the light through the medium appears to change.

To explain this phenomenon, we need to go back to basics. We imagine a solid medium as being made up of ions and electrons in a lattice structure. We know that these ions can vibrate (since this corresponds to the increase in kinetic energy of the solid). Now, the vibrational modes of the lattice are commonly called phonons: these phonons are the quanta of the vibrational modes. When a photon meets a solid, there are two things that can happen. Either it has an energy the same as one phonon mode; in which case it will interact with a phonon and then be absorbed and turned into heat. Or, the photon has an energy beyond the phonon spectrum. In this case the photon can disturb the lattice, but it cannot keep the vibrations up, since there is no available phonon mode. This photon is not absorbed and is emitted, but with some delay. As the photon continues to move down the medium, the same thing happens many times. It is this that gives us the apparent slowing of the light speed in the material.

[Lloyd Gillespie]

Hi Neutralino, good posts... I have a question I've pondered from time to time. Could you explain the physics of heat photons as they dissipate and cool from their sources, in the true physics analysis___Star, campfire, and/or candle...?

Regards,
Lloyd

[dipayankar]

Thanks ProfPat... I will have to check my source and see if I can add any value to this abstract..

[quote=Profpat;39928]

Originally Posted by neutralino Note that, in Bose-Einstein condensates, the speed of light may appear to be slowed, but the actual speed of a photon does not change. Here's the abstract to the article. For the full article, one would need to subscribe to Nature. [/quote Thanks Neutralino for the abstract site. Once again you are very helpful. Best, Pat