Does light have a mass?

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Of course light does not have mass. What spins in the sun????? A lot of stuff. Look at it this way, If anything travles at C, it must have no mass, and anything below C MUST have mass. Light can be 'bent' by gravity, but it is not really the light beam that is bent, it is spacetime.:mad:
 
The energy to create a photon must be provided by some external source. The photon then carries the energy from one place to another at the speed of light.
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Thanks for the info JR.

WHat you're saying is that relativistic mass/energy is provided by an external source.. however, as that amount of energy is the same everytime... i.e. to speed the photon to C, then the source of energy must be the same as well??
1.--->if so what is the source

in that regard, is the reletivistic mass of different photons then at variance to each other, i.e photons emitted by the sun should have less RM when they reach earth than when thy reach further plantets?


2.Or is it that, the photon, as soon as conceived, travels the speed of light and thereby acquires the energy/reletivistic mass along the way??

--->if so what is the source here? is it EM fields? where does this additional mass come from that is used as relativistic mass?



huh???
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Light can be 'bent' by gravity, but it is not really the light beam that is bent, it is spacetime.
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a bit of bent spacetime never hurt anyone, but our heads, still, sounds a bit ether-rial to me.
 
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Well it is correct that it's Spacetime that makes it bend, but that is due to the quanta that makes up spacetime having the effect on it. Otherwise you would only have space.

The quanta acts like waves on the surface of water (This of course is at two dimensional analogy), a boat can move across the surface of a calm pond, but if it gets choppy and the waves start to roll, the boat is doesn't just pitch, it also can raise and since into this wave wells.

Of course the difference with light is it might not follow those wells, but have a habit of jumping like a speed boat from crest of wave to crest of wave. (okay the analogy is a bit useless for a straight path, but it gives you a kind of round about way of explaining it.)
 
"""Ehrrrr... no, an electric field has the magic property that it can add energy to charged particles and make them move. It's the source of that energy that I refer to (it is contained within the field itself). The photon only comes up in the interaction: if a particle absorbs energy from the field, then QED states that it cannot absorb just any amount of energy: the energy the particle absorbs comes in packets... It can absorb one packet (quantum) of energy, or more, but not half a packet of energy. One of those packets of energy is a photon. In other words: I think the photon, or better: the transmitted packet of energy, is created at the moment the particle "decides" to absorb energy from the field.""""

hum hum, how do you define the "electric <<FIELD>> then? I thought it all came down in that the field is just our imagination but that it is just the "lines" the photons follow. The source of the energy is contained in the field itself --> again, what is the field

"""You bet I am going the non-local way . I am referring to the non-locality of the electric field here. The field (and hence the energy of the field) is available at all locations we are interested in, and hence the particle can interact with the field everywhere."""

wanna know what I think of non-local stuff? I think it's not really non-local. that's the way it appears to us.

analogy: you put an iron thread in the ground in a way that one end sticks out on one side of a wall and the other end on the other side
now you push on one side of it, the other end on the other side will immediately go up
Imagine that we can only see the surface and have no notion of someting "under the ground" , it will appear to be some non-local aspect to us.
I think like D. Bohm that there are different layers of reality and that the non-local aspect is just like that in our layer but in deeper reality field it's all just connected to each other (and can also disconnect)
the results are seen in particular situations.

"""just think of the Young two slit experiment (and yes, I've seen the effect with my own eyes: it is real ). """

I know this double slit experiment
have seen different interpretations of it also
 
Mostly harmless:

<i>WHat you're saying is that relativistic mass/energy is provided by an external source.. however, as that amount of energy is the same everytime... i.e. to speed the photon to C, then the source of energy must be the same as well??</i>

I don't understand what you mean by that. What do you mean the energy is the "same everytime"?

<i>is the reletivistic mass of different photons then at variance to each other, i.e photons emitted by the sun should have less RM when they reach earth than when thy reach further plantets?</i>

No, the energy of a photon is constant (in an inertial reference frame). Photons emitted by the sun have the same energy from the time they are produced to the time they are absorbed.

<i>Or is it that, the photon, as soon as conceived, travels the speed of light and thereby acquires the energy/reletivistic mass along the way??</i>

The photon is created with a set energy, which does not change.
 
I don't understand what you mean by that. What do you mean the energy is the "same everytime"?
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what i mean is what you said later:

The photon is created with a set energy, which does not change.
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My question was, 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.
 
Mostly Harmless, you should look back to page 4,5 or 6 where James R (and Thed) gave a set of formulas which exactly explain that. You should read a whole thread before throwing yourself into it, especially with such a long one ;)
 
spacetime shmacetime

The whole magic trick of spacetime as gravity bending light smacks of an irrational component of a theory of physics being accepted de facto due to an idolization of Einstein.
There were some vocal critics of components of Relativity including Herbert Dingle www.heretical.org/science/dingle2.html and Louis Essen http://www.btinternet.com/~time.lord/index.html (who was instrumental in developing the atomic clock. )
Many critiques of these guys use the term crackpot, as opposed to analyzing the arguments and illustrating where they went wrong in the brain.
The two qualities that seems common in a lot of post-Einsteinian purveying of Relativity is a lack of ability to distinguish between a metaphor and reality AND the pushing of questionable interpretaions of the GR and SR as facts of modern science that should not be questioned.
Any thoughts? More randoms later. I enjoy the thread greatly
 
You're right. "Spacetime" is not a physical existence, but a property of gravity feild. Einstein defined gravity as curved spacetime, and if light in a vacuum cannot be slowed, then this warped spacetime is the only way to describe it.

Space is not made of quanta, energy and matter are. While gravity *may* be made of quanta, space itself is not.

137, uh, no. The turning point in Einstein's life, when people finally begain noticing that relativity might be correct, was when light from a star was bent when passing near the sun. This proved for the first time that light can be bent, and while we can bend light here on earth by slowing it through a medium, here, there was no medium, only space and a minute cloud of hydrogen. Since light <I>in a vacuum</I> is a constant, how can it bend? One part MUST go faster than the other for anything to bend. Thus the conclusion is that the light goes striaght, but the path it takes (spacetime) bends.
 
absolute proof as turning point..maybe?

Uh, huh??, maybe?
Sir Arthur Eddington measured the deflection of a grazing star during a total eclipse. The result was closer to Einstein's prediction than it was to Newton's. This single instance had not proved Einstein to be entirely right, only righter than the now refuted Newton. Since there were only two eligible competitors[Newton & Einstein], Einstein's theory was declared the winner, but not unquestionably or conclusively.
In 1859 Fizeau found that the speed of a beam of light which was passed through a stream of water was affected by the speed of the water and that this effect could be explained by classical physics.
However, the effect can equally be well explained by the Theory of Relativity. By making approximations and discarding certain small terms as negligible, Einstein was able to show that it was in accord with his theory. However, he did not stop there. Lorentz had shown many years before that the effect was perfectly explicable by the classical laws. Nevertheless, Einstein boldly claimed that this "...DOES NOT IN THE LEAST DIMINISH THE CONCLUSIVENESS OF THE EXPERIMENT AS A CRUCIAL TEST IN FAVOUR OF THE THEORY OF RELATIVITY", and that 'RELATIVITY HAD BEEN DEVELOPED FROM THE HYPOTHESIS OF ELECTRODYNAMICS'.
Columbia University astronomer C.L. Poor in 1922,'26 & '30 gave unassailable refutations of the claims of Eddington
"Thirty-three photographic plates taken during the eclipse of 1919 show star images; of these thirty-three, seven only give results even approximating towards the Einstein predictions. And to make even these seven fit the hypothesis, the relativist is forced to invoke the aid of the Sun to distort the camera in a particular way and by just the right amount!" ..... "The relativity theory may be true, but no substantial experimental proofs have yet [1922-1990] been submitted by any of its adherents."
There is quite a bit of 'soup' for physical interaction surrounding the sun and emanating from the sun. The sun emits streams of ionized gas, electrons, protons, and helium nuclei, all of which makes up solar wind. There is an interaction of the earths atmosphere with solar wind.
The fact that there are other variables which can be studied leads to the legitimate scientific questioning of each component of Einstein's theories, to advance true science and not just to adhere to a popular theory as fact.
Two tracks in physics[and all science] are necessary, the theorizers and the experimenters. Theories must be tested and challenged for proof and disproof. Repeatability is the bulwark for a theory to be considered valid. This case must be built not once, but continually. The 'proof' from 1919 is always used as the major proof of Relativity. If I had a theory I purveyed as true and my favorite proof of this was over 80 years old, wouldn't it make you a wee bit skeptical? Where are the consistent, repeated verifications and the desire to intelligently debate the validity or falsity of theories. I seek to understand light thoroughly, not just accept that a popular theory is true. "Prove it to me" is the proper mantra of scientific study, not "just accept it.' Cheers! 137
 
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This is all may be true (hey I'm not getting up off my lazy ass to research it), but they also proved other parts of Einstein's theory. Such as time dialation. They put an atomic clock on a plane and flew it around the world, and compared it to an equivalant atomic clock on the ground. The difference was exactly that predicted by Einstein's theory. So how does lens distortion fit into this one?
I'm not saying Einstein was completely right. He was wrong about plenty of things. (Cosmological Constant anyone? Actually some people think he was right about this, but I haven't been following it enough to say for sure.) I just think that if his theory was as flawed as you claim, people wouldn't use it so much.
And for the record, there are countless experiments that can be explained by both classical and relativity physics. That doesn't really prove anything.
 
time dilation questionable, too

Louis Essen discussed the development of the atomic clock and the actual relationship to relativity.
Basically, after an initial time adjustment prior to launch, GPS system clocks are synchronized, and relativistic calculations can be ignored. The understanding of relativity by most people seems to be a misunderstanding between appearances and physics. Clocks may move slower due to a decrease in gravity, interaction with magnetic field of the earth in a different manner, or converse to the usual formula, the clocks run faster on earth due to the effects of gravity or sub-atomic interaction. What is usually left out of the conversation of time dilation is that it is intricately dependent upon a standardized measures and its associated measuring device. The question isn't necessarily 'is time dilated', but are clocks, whether based on mechanical devices or on atomic qualities, affected by the physics of their location, velocity,[fill in the variable.] Time, or succession of existence, is not necessarily dependent upon the devices used for its measurment or delineation. My atomic interaction with my wristwatch [I hold the second hand from moving] does not affect time nor effect a time dilation. An authoritative relativist like Nobel laureate Max Born clearly expressed this when he wrote: the (length) contraction, (and time dilation), are "only a way of our way of regarding things and is not a change of a physical reality. Hence (they) do not come within the scope of the concepts of cause and effect". They are "circumstantial companions of motion."
The time dilation component of relativity also falls under the category of 'they once did this experiment and it was found to be true' argument used to poo poo anyone who questions relativity's truth.The Global Positioning System works and ignores the 'Laws of Relativity'. The GPS community uses a frame fixed to the Earth but not rotating with it. And that is the only way the atomic clocks can be coordinated.
Any scientific theory may predict physical phenomena. If it is a good theory its pattern of prediction will stand the test of experimentation over time.
Hafele-Keating eastbound airplane showed retarded clock readings when compared with ground clocks, as expected. But then the westbound flying clocks showed... increased time readings! The latter totally contradicts Einstein's reciprocal symmetries. One has to explain this by saying that the ABSOLUTE rotational velocity of the three set of clocks is what determines their clock rates. Thus considered, the eastbound plane had earth rotation plus its speed V, (say E+V); the ground clock had only the earth's rotational speed, E; and the westbound clock had obviously E-V. So that order: E+V, E and E-V, must be strictly kept to "explain" the observed rates. You cannot say, following Einstein, that respect to the ground both planes had velocity V, (one eastward and another westward) so that BOTH planes should have had retarded time readings.
Whenever relativistic effects are observed, IF they are observed at all, the reports show ASYMMETRICAL results. Never a symmetrical relativistic effect have been observed.
These thoughts are not just my own, but of scientists/physicists rightfully responding to and expecting a theory to stand the test of experimentation and analysis. The desire is to continually develop a deeper understanding...each theory acts as a catalyst for the next. Historically, sucessive theories are not diminished, but built upon, revised, improved, and clarified. Much like metal is melted down and the dregs and dross are removed as our understanding is purified. Hows that for a lovely metaphor.
I would be ecstatic to hear the counter-arguments to the legitimate critiques of Relativity..or point me to the web sites, journals, physicists, etc., To investigate is to learn and understand, to repeat a mantra is to enter into the mystical.
137
 
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The Global Positioning System works and ignores the 'Laws of Relativity'. The GPS community uses a frame fixed to the Earth but not rotating with it. And that is the only way the atomic clocks can be coordinated.

We have in the Global Positioning System (GPS) an example of an actual engineering system in which the special and general theories of relativity are not merely of scientific interest, but rather are essential to its operation.
 
How so?

Q,

Could you elaborate on how both the special and general theories of relativity are essential to the operation of GPS?

137
 
Because an observer on the ground sees the satellites in motion relative to them, special relativity predicts that we should see their clocks ticking more slowly. A straightforward calculation using special relativity predicts that the on-board atomic clocks on the satellites would lose about 7 microseconds per day because of the slower ticking rate. A calculation using general relativity predicts that the clocks in each satellite would get ahead of ground-based clocks by 45 microseconds per day. The combination of these special and general relativistic effects means that, if not accounted for, the clocks on-board each satellite would tick faster than clocks on the ground by about 38 microseconds per day. Therefore, if these relativistic effects were not taken into account, the GPS system would be false within 2 minutes. Accumulated errors of this type would accumulate about 6 miles every day.
 
but...

Q,

Do you have the Relatavistic[or a] calculations/formulas and data that mathematically prove that the measurements made are due to Relatavistic Effects? A website link or reference to this information would be useful for everyone to read and evaluate.

But is this necessarily proof of Relativity as an accurate tool of science? That a force called gravity that is inherently bound with the mass of objects exerts a force upon the mass of other object is a baseline...whether this force involves spacetime contortions is in question.

At high altitude, where the GPS clocks orbit the Earth, it is known that the clocks run roughly 46,000 nanoseconds (one-billionth of a second) a day faster than at ground level, because the gravitational field is thinner 20,000 kilometers above the Earth. The orbiting clocks also pass through that field at a rate of three kilometers per second -- their orbital speed. For that reason, they tick 7,000 nanoseconds a day slower than stationary clocks.

To offset these two effects, the GPS engineers reset the clock rates, slowing them down before launch by 39,000 nanoseconds a day. They then proceed to tick in orbit at the same rate as ground clocks, and the system "works." Ground observers can indeed pin-point their position to a high degree of precision. In (Einstein) theory, however, it was expected that because the orbiting clocks all move rapidly and with varying speeds relative to any ground observer (who may be anywhere on the Earth's surface), and since in Einstein's theory the relevant speed is always speed relative to the observer, it was expected that continuously varying relativistic corrections would have to be made to clock rates. This in turn would have introduced an unworkable complexity into the GPS. But these corrections were not made. Yet "the system manages to work, even though they use no relativistic corrections after launch," Van Flandern said. "They have basically blown off Einstein." See http://www.ldolphin.org/vanFlandern/ for information on this mathematician/astronomer who worked on the GPS.

What seems the most illogical about your, Q's, explanation is that there are millions of observers who 'using straightforward calculations' of STR and GTR would be each calculating a completely different result for each and every GPS satellite. If this were true, NO computer in the world or network of computers in the world could manage the exponential number of self-contradictory results.
Where am I wrong in this conclusion, in your estimation?

137
 
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137

Whoooa! You're quoting from Van Flandern? And using his website as reference ?

Sorry bud, this is where the Q exits stage left. I will not debate anyone that references one of the most infamous of crackpots.
 
But why?

And this is the problem.

The issue is not whether someone is a crackpot [I do not consider Einstein a crackpot], but whether a person's theory or critique is correct or incorrect. If you can illustrate where the information I cited is in error, then you are obviously interested in pursuing and purveying physics as a science.

Can you or can you not counter the information that was cited?

Can you or can you not provide formulas or response as requested:
"Do you have the Relatavistic[or a] calculations/formulas and data that mathematically prove that the measurements made are due to Relatavistic Effects? A website link or reference to this information would be useful for everyone to read and evaluate. "

and
"What seems the most illogical about your, Q's, explanation is that there are millions of observers who 'using straightforward calculations' of STR and GTR would be each calculating a completely different result for each and every GPS satellite. If this were true, NO computer in the world or network of computers in the world could manage the exponential number of self-contradictory results.
Where am I wrong in this conclusion, in your estimation? "

If you have to resort to ad hominum "crackpot" retorts and cannot provide logical proofs to back up your claims then why bother.

I have nothing vested in any scientist or their theory, but I am willing to step through the logical process of understanding someone's argument, analyzing it and seeing if it holds up.

Anyone else care to respond, comment or 'learn me' on this that does not have to resort to 'crackpot' statements?

137
 
How so?

c'est moi,

How do you mean?...in the vein of 'Ours is not to question why, our is but to bend spacetime?'

137
 
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