# Thread: Does light have a mass?

1. 137 (Why 137? Fine structure constant springs to mind):

<i>...3. My trigger to release the light signal causes the BEC to emit a light signal equivalent to the one absorbed.
Or is the claim that it is the EXACT light signal, frozen in time?</i>

The light signal is stored in the atomic ensemble. The signal which is released is like a read-out of that information. So, I guess your first sentence is closer to the mark.

<i>Why was it necessary for Einstein to pick up the contraction formulation from Lorenz[and rework it to his own ends, of course?] My reading is that the Michelson-Morley concluded that the "null" result obtained by Michelson and Morley was caused by a effect of contraction made by the ether on their apparatus [Michelson interferometer]...and therefore introduced the the length contraction equation.</i>

No. The null result of the M-M experiment is due to the invariance of the speed of light in the two directions of the interferometer arms. In the rest frame of the interferometer, there is no length contraction of the interferometer.

2. ## Yes indeed

It is a mighty fine structure...your springing mind is correct, James R

I will reread the Lorentz again and see what he actually said and either type up the sequence with comment/question or fess up that I read sloppily.

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3. I am still in the mulling over stage of the Lorentz, but I had a thought. James R, your answer is based on the relativistic understanding of the experiment as opposed to the understanding of M-M and Lorentz's attempt to reconcile their experimental results, no?
My attempt is to understand the understanding within the framework of M-M and Lorentz's analysis so that I fully understand this proto-Relativity phase of physics [Another generality, but I will assume everyone knows what I mean.]

One of the points I am focussing on in Lorentz's little paper is his description of the possible scientific basis of the shortening of 'rods' in the direction of motion, light being used as a measuring tool and his era which was still hunting for the aether in the mist, though aether, and its effects, did not seem to be manifesting itself experimentally leaving aetherlings puzzled...

Michelson's Interference Experiment

I resisted the urge to reprint any of the text at this time.

4. Hi, anyone wanna help me out here. I'd posed a question:

"... if a photon is created with a set energy, then how does it/from where does it acquire the 'extra' energy, that mkes a 0 rest mass photon into a photon with X reletavistic mass.

taht extra energy which converts 0restmass to an increased XRel.mass must be comming from somwhere.

if that energy is comming from some source, then the source must be the same no matter where you 'weigh' the photon, since every photon's energy (relativistic mass) is the same no matter where u measure it."

anyone, BUT c'est moi in case she banishes me to the beginning of the thread which i have painstakingly trugded through. And no, i dont think the formulas help, they may help prove or disprove the theory, but i would prefer, if anyone chooses to take up the gauntlet, to have it explained in plain english. maybe i should just write to Stevie H., he'd know.

c'est moi,
dont hide behind formulas, they're not all what science is made of. science is an attempt to explain life, to anyone that is, not just another physicist.

5. Hi Mostly Harmless,

The photon has (relativistic) relativistic mass because it has momentum. This is more conveniently expressed by the fact that a photon has a higher energy if it propagates light of a higher frequency.

Bye!

Crisp

6. (had to correct my name)

another interesting article i read was about the propagation of light from sound

http://www.sciam.com/news/052201/3.html

here is a newer article, with links to the one i read last year. i'm not trying to add more confusion here, but its all related. great thread! i'll have to catch up on the middle

7. ## massy light

Crisp [or anyone else who wants to venture an explanation],

Can it be understood that the idea of light having a rest mass of zero is unemitted light, and the the relativistic mass of propagated light is considered a property of the total energy of any given 'amount' of propagated light? By extension, that a photon's energy is measured by the energy which can [potentially] be absorbed by an atom?

137

In the Lorentz paper, previously referenced in a post, he [Lorentz] is deparately trying to fit experimental results within the framework of the 'resting aether.' There is a figurative head scratching [and references to predesessor head scratching] that is going on trying to figure out how to create a formula which does not abandon the ether:
One would have to imagine that the motion of a solid body(such as brass rod or stone disc employed in the later experiments) through the resting ether exerts upon the dimensions of that body an influence which varies according to the direction of motion.
the above is from Lorentz in 1895.

In 1904, Lorentz is still trying to cram the ether into observed results: ELECTROMAGNETIC PHENOMENA IN A SYSTEM MOVING WITH ANY VELOCITY LESS THAN THAT OF LIGHT ---I am going to read this in depth next.

Within 1 year of Lorentz's previously mentioned paper, in 1905, Einstein[who supposedly was unaware of the 1904 Lorentz paper] will be tossing out the ether [the 'light medium'] saying,
'The introduction of a "lumeniferous ether" will prove to be superfluous inasmuch as the view here to be developed will not require an "absolute stationary space" provided with special properties, nor assign a velocity-vector to a point of the empty space in which electromagnetic processes take place."
the above quote is from Einstein's ON THE ELECTRODYNAMICS OF MOVING BODIES.
This paper is the pivotal point in physics which gave birth to the uses, abuses and questions of Relativity on this forum [and beyond.]

--> I am putting these links as a chronology of the theoretical development, a record of my re-reading the source material and as a service for everyone who may want to begin by learning from the source material. Also, I make no claims to the accuracy or validity of the texts which I have found and I do not vouch for the websites. I merely did a search and used the first site that apeared to have the full text. Personally, I use THE PRINCIPLE OF RELATIVITY a collection of original memoirs on the special and general theory of relativity by Lorentz, Einstein, Minkowski, and Weyl from 1923 as a baseline of the theories being discussed.

see ya...
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8. Mostly Harmless,

<i>if that energy is comming from some source, then the source must be the same no matter where you 'weigh' the photon, since every photon's energy (relativistic mass) is the same no matter where u measure it.</i>

That's not true. A photon's energy varies depending on from which reference frame you measure it. What doesn't change is the photon's <b>speed</b>.

Photons get the energy they have when they are created, according to the properties of the source creating them. Photons are created travelling at the speed of light. They don't sit stationary with their zero rest mass waiting for something to give them energy (and hence relativistic mass). There's no such thing as a stationary photon.

9. ## mass of photon information

What is the Mass of a photon

Would love to hear commentary on this... it brings up an issue on correct[modern] terminology to use regarding the 'mass' of a photon.

Q: I looked at the Crank site. Pretty fun stuff. My only issue with the site is that it merely links to claims and labels the site/author with various 'crank' terms but leaves the visitor with no countering argument[maybe I am missing this part of the web site...I cannot spend ALL my time surfing and reading.]
It is a given that if a site claims that 'space monkeys are continually throwing energy balls back and forth and the the waves caused by their screeches of delight create a wavefront upon which existence emerges,' that by an order of many magnitudes, this is a ridiculous theory at worst, or a silly fable at best. But not every argument can be satisfied by merely labeling crank.

137

10. We space monkeys only throw energy balls back and forth when paid to do so, and we make no claims regarding such activities and the nature of physics.

11. ## At least now we know there are space monkeys

Damn, now I've gotta read Einstein's lost paper,
ON THE ELECTRODYNAMIC WAVEFRONT GENERATED BY SPACE MONKEYS 1907 [published in the lost memoirs] covers his interviews of space monkeys. The theory generated would have changed the history of physics...perhaps a little...The little capitalist space monkeys could have cornered the market, instead, well, you know the rest....

137

12. ## Einstein in the original German

Has anyone on the forum [or any of these forums] read Einstein in the original German? I would like to ask some questions. I would like to ask via email first and then decide whether to post any light/mass related shenanigans!

thanks,
137

13. thanks for the info, Crisp/JR.

by the way, when they screach do the Space Monkeys go ... OMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM?
aparently, accordingto the hindu religion, all life emanated from the first Sound OMMMMMMMMMMMM.

you think maybe the monkeys are responsible for all this confusion? figures.

14. ## ether or

OK...I have not read the Lorentz and Einstein papers [ELECTROMAGNETIC PHENOMENA IN A SYSTEM MOVING WITH ANY VELOCITY LESS THAN THAT OF LIGHT & ON THE ELECTRODYNAMICS OF MOVING BODIES, respectively] as thouroughly as I want, but here is a little tidbit for discussion.
How does this statement strike people:

Einstein did not throw out the ether, he merely renamed it SPACE-TIME. ------ I am sure that this statement has been made before...but I do not think I have come across it------

Basically his theory states that the endless succession of an innumerable number of events and interactions in the universe gives you a continually moving 'ether' or rather an ever changing arrangement of the universe...no set coordinate system and, thus, any calculation that is to truly predict interacting systems must take time/space changes into consideration.
The speed of light is given the job of being the yardstick of the universe due to its top speed in a vacuum and its emitted speed. Due to light's [just a generalization as usual] instantaneous top speed at emission[in a vacuum] it is not subject to any coordinate system[I'm a gonna do a thought experiment in the next post to illustrate this.]
Knowing there will be 'pashas' of the learned, rolled eyes with 'he just doesn't get it' from the all-knowing and yaps of 'crank' from the gods of relativity, I would still like to see anyone who gives a damn about really knowing and describing relativity to chime in.

As with many prose approximations of a theory, the calculations are not taken into account, but it does help me to rethink the mindset of Einstein's attempt to conceive of a universal framework which will guide physics in the correct direction to answer the previous 'troubling results' of physics theory versus experimental results.
None of this changes the conversation, here, of whether the resulting calculations for STR and GTR and ramifications of the two Relativities have gone off of the deep end or truly live up to the acolytes' praise.
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
If we on the forum are truly trying to understand, transfer an understanding or helping folks develop an ability to understand this topic, then there must be a way to at least build a common understanding based on the latest understanding in physics. The paper linked in a previous post on WHAT IS THE MASS OF A PHOTON seems to be valid in its llustration of the different ways in which a photon is discussed and which is the preferred term in contempory physics.
There are plenty of people, including those who are probably lumped into crank category on this forum, that would appreciate the link. Due to the fact that the paper relegates the counter-intuitive concept of 'massless particle' as unnecessary, this is one less 'strange' concept that the 'cranks,' as many call them[perhaps I am one of them due to the fact that there are too many oddities being proported to be fact,] will be need to argue about.

!!!!!!!!!!!!!!!!!!!!
The resultant wavefront created by the Space monkeys screams of delight are 'MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMO' after calculations to account for Doppler effect, velocities and time, one can find a midpoint which shows that there is a symmetry between space monky scream and wavefront. It is quite an elegant formula. By the way, the screams are massless.

137

15. That's basically a misunderstanding. The universe is cyclic. At the end of the last one, we space monkeys were sitting about bored, and someone asked "So, what are we gonna do now?" Someone replied "Ummm, dunno." So "UM" was the first, and "DUNNO" was the second. The third sound, you may be interested to know, was "Scrabble?"

16. ## Re: ether or

137,

<i>Einstein did not throw out the ether, he merely renamed it SPACE-TIME.</i>

Wrong. The "luminiferous aether" was a postulated substance which allowed light to propagate in a vacuum. However, the work of Maxwell and the Michelson-Morley experiment clearly showed that no such medium was theoretically necessary, or experimentally detectable.

Spacetime is a geometrical construct which allows us to label events with coordinates. It has no substance, but it does have a concept of "length", which is measurable using something called a <b>metric</b>. It is quite different to the ether.

<i>The speed of light is given the job of being the yardstick of the universe due to its top speed in a vacuum and its emitted speed.</i>

The speed of light is special in relativity because, along with a few other things, it is a <b>frame independent</b> quantity (i.e. one whose value is constant in all inertial frames of reference).

<i>Due to light's [just a generalization as usual] instantaneous top speed at emission[in a vacuum] it is not subject to any coordinate system[I'm a gonna do a thought experiment in the next post to illustrate this.]</i>

Light can be described in coordinate systems just like any other thing which participates in events in spacetime.

<i>Knowing there will be 'pashas' of the learned, rolled eyes with 'he just doesn't get it' from the all-knowing and yaps of 'crank' from the gods of relativity, I would still like to see anyone who gives a damn about really knowing and describing relativity to chime in.</i>

*chimes in*

<i>If we on the forum are truly trying to understand, transfer an understanding or helping folks develop an ability to understand this topic, then there must be a way to at least build a common understanding based on the latest understanding in physics. The paper linked in a previous post on WHAT IS THE MASS OF A PROTON seems to be valid in its llustration of the different ways in which a photon is discussed and which is the preferred term in contempory physics.</i>

Yes, that link is a good one. To avoid confusion, though, it is titled WHAT IS THE MASS OF A <b>PHOTON</b>, not "proton".

<i>There are plenty of people, including those who are probably lumped into crank category on this forum, that would appreciate the link.</i>

I should point out that the information in the link has already been carefully explained several times to some of the people vying for a place in the "crank" category.

17. ## but what of the sources

James R,
Wrong. The "luminiferous aether" was a postulated substance which allowed light to propagate in a vacuum. However, the work of Maxwell and the Michelson-Morley experiment clearly showed that no such medium was theoretically necessary, or experimentally detectable.
In hindsight and in contemporary physics[our time] no ether is necessary. This is why I posted the links to Lorentz. He explicitly states his attempts to reconcile the experimental data with the existence of the ether. Either you are responding within the framework of contempory physics [which I have tried to explain that I am looking at a particular and historical pivot point of physics. Maxwell, Michelson & Morley, to name a few were working within the context of the existence of the ether. Einstein removed the need for an ether as necessary] or you have not read the Lorentz [his attempts to justify the M-M results with the existence of an ether are not implied, they are explicit.] My statement that Einstein renamed the ether is an attempt to describe the fact that he stated that universal substance was NOT necessary, BUT that the results of Einstein's space-time calculations seem to mirror anticipated results which were being sought by the aetherlings.

Also, thanks for the correction...I will edit my link to the correct title. My whoops
Light can be described in coordinate systems just like any other thing which participates in events in spacetime.
But it is not constrained to any coordinate system was my contention. Am I wrong? To elaborate: One light source is continuously emitting light and this light passes through 4 different, unrelated coordinate systems/frameworks which are going in different directions/velocities/accelerations. They are not interacting with each other at all[for the sake of this statement] - are unaware of each other -do not care one iota about each other. At varying times each coordinate system measures the speed of light and due to the 'timing' there is never any issue of the readings from one coordinate system interfering with the coordinate system of another. Given this long winded setup, my point was that in each coordinate system, they will all measure the speed of light as equivalent, no?
I should point out that the information in the link has already been carefully explained several times to some of the people vying for a place in the "crank" category.
I assume you mean the Crank site link? If so, my comment on the lack of explanation or refutation of the various theories was more aimed at the website itself. I just happened to find this forum...I could have just as easily, just happened to find that site.

137

18. ## What is the Mass of a photon link

What is the Mass of a Photon

19. ## 137

As you are particularly interested in the pivotal historical role of Maxwell, Lorentz and Einstein I notice there is something you appear to have missed.

The Maxwell equations are a superb description of how waves propagate throughout space without a need for some medium. If those equations where wrong then the later developement of the Telegraph and radio would not have happened. But, most importantly, the Maxwell Equations do not work with the earlier Galilean Transform. They are as incompatoble as Quantum Mechanics and Relativity are. In fact, the Lorentz transform was proposed as a new transform that worked with Maxwell and conformed with the Galilean transform in the limit of low velocities.

The problem is that you have to make an assumption that space (the dimensions x,y,z and time t) are interelated.

Just something to chew on.

20. ## I will now time travel through books

Thanks Thed,

You have pointed out something which I have been claiming to avoid. Outside of exposure to the practical Maxwell through electronics, I am not reading his work first hand. I will start going backward in time, again, through the only workable time portal...the original works. I am becoming more interested in the monkey on the back of physics which was called ether[aether]. There was so much time, historically, that was spent trying to prove what the ether did, how it was contructed, what its properties were, etc...This is why I found Fizeau's experiments interesting. [My understanding] He wanted to see if the motions of a medium would affect light...he was searching for the aether convection coefficient -- [he found partial convection in water(?)].

Slowly, experimental evidence was showing that you could remove calculations regarding the ether, rendering it as unecessary. I guess I will be adding Maxwell to my list of 'to study.'

thanks--->
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