# light propagates at c + v?

Discussion in 'Alternative Theories' started by BdS, Nov 21, 2015.

1. ### BdSRegistered Senior Member

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https://en.wikipedia.org/wiki/Galactic_year

“The Solar System is traveling at an average speed of 828,000 km/h (230 km/s)”

1 / 299792458m = 0.0000000033356 sec (time it takes light to travel 1 metre)
230km * 1000 = 230000m (Solar System average speed around the galaxy in metres)
230000m * 0.0000000033356 = 0.000767188m = 0.767188mm (distance Earth moved in orbit around the galaxy in the time it took light to travel 1 metre)

If light travels at only c and not c + v (where v is the velocity of the emitter) then we should measure a drift of 0.767188mm over a 1 metre distance and a 230km drift over 299792458m.

Take a mounted laser and shine it against the wall from a distance of 1 metre. Draw a dot on the wall where the laser light is and keep it on for a year. If light travels at only c then we should detect a drift of up to 0.767188mm from the dot we drew on the wall. The Earth is spinning and orbiting the sun so as it spins the drift will change direction depending on the direction we are facing relative to the galactic year orbit direction/speed of 230km/s. If the orbit speed is to our left we should detect a drift to the right of our dot and in 12 hours when the orbit speed is to our right the drift should be to the left of the dot.

If we don’t detect a drift then light travels at c + v

3. ### rpennerFully WiredValued Senior Member

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That's not how relativity (our best theory of space and time) works.

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5. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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This is a cut and past from your thread in 'gravitational field...' in psuedo-science, which is against forum rules on multiple posts. No matter where you post this or how often you post this, the posts will only highlight your ignorance of the properties of EM radiation.

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7. ### exchemistValued Senior Member

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I really do not know what you hope to gain from this. This sort of thing has all been done, a century ago and the results are unequivocal. You will always measure c, irrespective of the relative speeds of emitter and receiver. The observed fact that c , i.e. length/time is always measured to be the same is the reason why the only possible conclusion is that apparent lengths and durations of time must be observer-dependent, in such a way as to keep their ratio, c, constant. In other words, it's the whole point behind special relativity. Is it not?

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8. ### Janus58Valued Senior Member

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We would not detect such a drift. But then from your conclusion we should measure the speed of a light emitted by a source moving towards us at v as being c+v with respect to ourselves, and we don't do that either, we still measure it as c with respect to us.
And while this may seem contradictory, a hoard of experiments/observations back this up. So here's the thing, it turns out that the "rules" of time and space that we have come to think of as "natural" due to our everyday experiences are incorrect and only give us close approximations of what is really happening when dealing with small velocities. For instance, to us it seems natural that adding two velocities such as u and v should result in a total equal to u+v, but it turns out that it doesn't. Instead the answer is
$\frac{u+v}{1+\frac{uv}{c^2}}$

As long and u and v are both small compared to c, you will get an answer that it very, very close to u+v. (This not too different from the idea that over small distances you can treat the path of a projectile like a tossed ball as a parabola with the force of gravity being parallel at all points of its path, and get an accurate enough answer of where it will land, however, over long distances, such as long range artillery, you have to account for the fact that the path is really a section of an ellipse and the Earth curves and the Earth rotates to get an accurate answer.)

Relativity deals with the new "rules" that time and space follow that differ from the old rules. Arguing against it based on the old rules is like arguing against orbital mechanics because it's conclusions don't line up with those made by assuming a flat Earth cosmology.

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9. ### Farsight

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The speed of the emitter doesn't matter, because light has an E=hf wave nature. The speed of the wave depends on the properties of space, not on the speed of the emitter. However there is such a thing as the Sagnac effect. See this Baez/PhysicsFAQ article and note this:

"That the speed of light depends on position when measured by a non-inertial observer is a fact routinely used by laser gyroscopes that form the core of some inertial navigation systems. These gyroscopes send light around a closed loop, and if the loop rotates, an observer riding on the loop will measure light to travel more slowly when it traverses the loop in one direction than when it traverses the loop in the opposite direction. This is known as the Sagnac Effect. The gyroscope does employ such an observer: it is the electronics that sits within the gyro. This electronic observer detects the difference in those light speeds, and attributes that difference to the gyro's not being inertial: it is accelerating within some inertial frame. That measurement of an acceleration allows the body's orientation to be calculated, which keeps it on track and in the right position as it flies..."

See the thing about the horses. If you send two horses in opposite directions around the same race track, then the horse that crosses the finish line first must have run faster.

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10. ### rpennerFully WiredValued Senior Member

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Non sequitur. All phenomena which convey energy and momentum have a wave nature by the deBroglie hypothesis which is incorporated into relativistic quantum mechanics and quantum field theories: $E = \hbar \omega = hf = \sqrt{m^2 c^4 + c^2 \vec{p}^2}, \; \vec{p} = \hbar \vec{k} = c^{-2} E \vec{v} = h \lambda^{-1} \hat{v}$ but if $m>0$ then it follows that $E > c | \vec{p} |$ thus $| \vec{v} | = \frac{c^2 | \vec{p} |}{E} \lt c$ and so the 1-dimensional composition of velocities is: $v' = \frac{u + v}{1 + \frac{u v }{c^2}} = c \tanh \left( \tanh^{-1} \frac{u}{c} + \tanh^{-1} {v}{c} \right)$ so if both v and u are in $\left( -c, \; c \right)$ then so is $v'$.

But if $m=0$ then $E = c | \vec{p} |$ and $|\vec{v}| = c$ so when u is in $\left( -c, \; c \right)$, and $v= \pm c$ we have $v' = \frac{u + v}{1 + \frac{u v }{c^2}} = \frac{u \pm c }{1 \pm \frac{u}{c}} = c \frac{ u \pm c }{c \pm u} = c \times \frac{\pm 1 \times \left( c \pm u \right) }{c \pm u} = c \times \pm 1 = \pm c = v$.

So the speed of the emitters doesn't matter because light is has zero rest mass and therefore is measured as traveling at light speed in all inertial reference frames.

(The General Relativity version of this is demonstrating that a portion of null geodesic in one coordinate system is still a null geodesic in another coordinate system.)

As demonstrated above, the speed is a function of the mass of the phenomena which carries energy and momentum and sometimes the speed of the emitter or observer. (Or in General Relativity, the coordinate speed depends on the choice of coordinates.)

Which is proportional to the violation of the assumption that the measurement system is based on an inertial coordinate system.

The analogy is inapposite in that horse speed is determined relative to the racetrack and even if the race track were some sort of moving belt, horses don't achieve speeds comparable to the speed of light and to good approximation $v' = \frac{u + v}{1 + \frac{u v }{c^2}} \approx u + v - v \frac{u^2}{c^2} \approx u + v$ when $0 \leq |u| \lt |v| \lt \lt c$.

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11. ### brucepValued Senior Member

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Nice work. I especially like the comment about the method for GR.

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12. ### Farsight

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Oh please, don't try to kid anybody that you know better than the PhysicsFAQ website. It's perfectly clear that you don't understand the speed of light in the slightest. Throwing out specious spoiler objections whilst trying to disguise your lack of content with a smokescreen of mathematical handwaving is not a useful contribution to the thread. Oh, and do pay attention to your first line and recall how you objected repeatedly to my post about the wave nature of matter on this thread.

13. ### rpennerFully WiredValued Senior Member

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Here I pointed out that your reason for the speed of the emitter not mattering was not a valid argument. That has nothing to do with the PhysicsFAQ website. And while you quoted that part of my post (through laziness) you did not actually respond to it.
You have claimed there is a lack of content, but factually there is content. Original content, not quoting verbatim or repeating analogies from other authors. Arguably, better content. And well-received content. Your objection to the math of relativity as "handwaving" I will put down to an unprincipled position predicated on your math envy. You don't recognize it by name but $v' = \frac{u + v}{1 + \frac{u v }{c^2}}$ is a form of the Einstein law of composition of velocities in the same direction given in his first 1905 paper on special relativity (See the last equation of Part I, Section 5 of On the Electrodynamics of Moving Bodies ). I saw no need to derive my point directly from the Lorentz transformation of a light signal, but that method is also valid.

John Baez hosts the Physics FAQ, as do a lot of people. But Don Koks is the editor and most recent author of the page you quoted. Steve Carlip and Philip Gibbs were responsible for earlier versions.

Did I object to the claim matter has a wave nature? No. Here I pointed out that BOTH light and matter have a wave nature so the wave nature cannot be the reason for the speed of light being independent from its emitter since baseballs and electrons fired from moving platforms show no such independence.

Here I was claiming the analogy (which is about measuring average speed about a closed track, as in the Sagnac effect) is not directly applicable to the thread's question of "v + c?". The horse presumably has a characteristic speed associated with and relative to the substrate of the racetrack and is governed by non-relativistic mechanics which would lead you astray on the question of "v + c?".

Just because the second sentence is the verbatim last part of a sentence from the webpage does not mean it is a good analogy for the discussion in this thread. You have not argued that it is.

Last edited: Nov 23, 2015
14. ### Aqueous Idflat Earth skepticValued Senior Member

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Why argue? Simply build the experiment which shows a rolling fringe on the interferometer as the source approaches or leaves the field of view at a high rate of speed. See, for example,

http://www.math.wichita.edu/MEDIA/phys516.pdf

This gets you to about 1850 techolnology, when Hippolyte (sounds funny if you say "lite") Fitzeau discovered that you are incredibly wrong.

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15. ### river

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Tesla contradicts a part of the relativity theory emphatically, holding that mass is unalterable; otherwise, energy could be produced from nothing, since the kinetic energy acquired in the fall of a body would be greater than that necessary to lift it at a small velocity.

Just saying

16. ### river

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Further

veryday Science & Mechanics
November, 1931
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Faster Than Light!
by

Hugo Gernsback
It may come as a shock, to most students of science, to learn that there are still in the world some scientists who believe that there are speeds greater than that of light.

Since the advent of Einstein, most scientists and physicists have taken it for granted that speeds greater than 186,300 miles per second are impossible in the universe. Indeed, one of the principal tenets of the relativity theory is that the mass of a body increases with its speed, and would become infinite at the velocity of light. Hence, a greater velocity is impossible.

Among those who deny that this is true, there is Nikola Tesla, well known for his hundreds of important inventions. The induction motor and the system of distributing alternating current are but a few of his great contributions to modern science. In 1892, he made his historic experiments in Colorado; where he manufactured, for the first time, artificial lightning bolts 100 feet long, and where he was able, by means of high-frequency currents, to light electric lamps at a distance of three miles without the use of any wires whatsoever.

Talking to me about these experiments recently, Dr. Tesla revealed that he had made a number of surprising discoveries in the high-frequency electric field and that, in the course of these experiments, he had become convinced that he propagated frequencies at speeds higher than the speed of light.

In his patent No. 787,412, filed May 16, 1900, Tesla showed that the current of his transmitter passed over the earth’s surface with a speed of 292,830 miles per second, while radio waves proceed with the velocity of light. Tesla holds, however, that our present “radio” waves are not true Hertzian waves, but really sound waves.

He informs me, further, that he knows of speeds several times greater than that of light, and that he has designed apparatus with which be expects to project so-called electrons with a speed equal to twice that of light.

Coming from so eminent a source, the statement should be given due consideration. After all, abstract mathematics is one thing, and actual experimentation is another. Not so many years ago, one of the world’s greatest scientists of the time proved mathematically that it is impossible to fly a heavier-than-air machine. Yet we are flying plenty of airplanes today.

Tesla contradicts a part of the relativity theory emphatically, holding that mass is unalterable; otherwise, energy could be produced from nothing, since the kinetic energy acquired in the fall of a body would be greater than that necessary to lift it at a small velocity.

It is within the bounds of possibility that Einstein’s mathematics of speeds greater than light may be wrong. Tesla has been right many times during the past, and he may be proven right in the future. In any event, the statement that there are speeds faster than light is a tremendous one, and opens up entirely new vistas to science.

While it is believed by many scientists, today, that the force of gravitation is merely another manifestation of electromagnetic waves, there have, as yet, been no proofs of this. There are, of course, many obscure things about gravitation that we have not, as yet, fathomed.

At one time, it was believed by many scientists that the speed of gravitation is instantaneous throughout the universe. This is simply another way of putting it that there are speeds greater than light.

Yet, from a strictly scientific viewpoint, no one today has any idea how fast gravitational waves — always providing that the force is in waves — travel. If the moon, for instance, were to explode at a given moment, how long would it be before the gravitational disturbance would be felt on earth? Would the gravitational impulse or waves travel at the speed of light — that is, 186,000 miles per second — or would the effect be instantaneous? We do not know.

The entire subject will no doubt arouse a tremendous interest in scientific circles. It is hoped that other scientists will be encouraged to investigate Dr. Tesla’s far-reaching assertions; either to definitely prove or to disprove them.

17. ### rpennerFully WiredValued Senior Member

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Disproven or shown to be irrelevant. There are superluminal phase velocities in relativity, but not superluminal group velocities. The result is no signal can be sent faster than light.

The rates of momentum loss from binary neutron stars closely matches the predictions of GR which says gravitational waves with a certain velocity carry away that momentum. Until an experiment proves that wrong or a better theory replaces GR with better predictions of everything that GR says, then the GR speed of gravity is the only evidenced speed of gravity.

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18. ### BdSRegistered Senior Member

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when you calculate the orbit of the earth do you calculate the gravitational attraction to where the sun was 8 min ago?
230km * 60sec * 8 = 110400km away from where the sun would currently be.

19. ### PhysBangValued Senior Member

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One can't help but agree and see that the individual you are discussing still hates the actual work of Einstein.

20. ### brucepValued Senior Member

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That's irrelevant regardless which theory of gravity you use to determine the orbit. The entire solar system orbits the galaxy at the same speed as the Sun. The solar system is gravitationally bound. For Newton the rate of angular velocity and radial oscillation is M_sun/r^3. Newton's theory says the gravitational interaction is instantaneous [action at a distance] while GR is a local theory of gravity where the orbital path is determined by the local spacetime curvature. So you can derive the naturally processing Einstein orbits from the effective potential component of the main equation of motion and the metric. Without showing you the derivation the rate of angular velocity for Einstein orbits is = M_sun/r^2(r-3M_sun) and the rate of radial oscillation = M_sun(r-6M_sun/r^3(r-3M_sun). From this you can derive the natural precession rate for any orbit. The famous test being the natural precession of Mercury.

Last edited: Nov 29, 2015
21. ### BdSRegistered Senior Member

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So in both theories the gravitational field is moving at v the velocity of the object thats creating it. In GR the gravity travels at c + v and a change in gravity would take time to configure, in Newton's theory the configuration is instant but still at v. If the object accelerates in GR the already existing gravity would then drift from the object that creates it and could never catch up to the new speed of the object. In GR the object would be leaving behind gravity pings in space by the amount of the acceleration causing a doppler type shift as the object accelerates to new speeds, every new pulse or curve segment would be traveling at the new v. In Newton's theory the whole field will instantly reconfigure to the new speed, so the existing field will accelerate with the object?

Last edited: Nov 29, 2015
22. ### brucepValued Senior Member

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No it doesn't travel at c+v. It's not like this is impossible to learn. I guarantee whatever you imagine it to be is bullshit.

23. ### BdSRegistered Senior Member

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So why do you say its irrelevant? if it doesnt travel at c + v then you must calculate the orbit off the 8 min curve ping in GR.