2017-02-12 09:51:44 UTC
Albert Einstein, ON THE ELECTRODYNAMICS OF MOVING BODIES, 1905: "...light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body."
This means that, when the initially stationary light source ("emitting body") starts moving towards the stationary observer (receiver) with speed v, the speed of the light relative to the observer will remain constant, c - it will NOT become greater, c'=c+v.
The constant (independent of the speed of the source) speed of light sounds reasonable insofar as this constancy characterizes all other waves. However, while for other waves the independence is compatible with any other feature of those waves, in the case of light the assumption that the speed of light is independent of the speed of the light source leads to contradictions and is therefore unacceptable. Consider the following detailed quotation:
"We will start with a very simple set-up, which you can see in the following animation. On the right-hand side, drawn in green, there is a sender that emits pulses in regular succession. On the left-hand side there is a receiver, drawn in blue. The pulses themselves are drawn in red, and they all travel at the same speed from right to left. Every time the sender emits a new pulse, a yellow indicator light flashes once. Likewise, a flashing light indicates when a pulse has reached the receiver:
Next, let us look at a slightly different situation, where the source is moving towards the detector. We assume that the motion of the sender does not influence the speed at which the pulses travel, and that the pulses are sent with the same frequency as before. Still, as we can see in the following animation, the motion influences the pulse pattern:
The distance between successive pulses is now smaller than when both sender and receiver were at rest. Consequently, the pulses arrive at the receiver in quicker succession. If we compare the rates at which the indicator lights at the receiver and at the sender are flashing, we find that the indicator light at the receiver is flashing faster. [...] Due to the sender's motion, the distance between two successive pulses in this case is not d, but d-D." [END OF QUOTATION]
The last sentence in the quotation above implies that, as the light source starts moving, it actually starts catching up with the pulses, and if its speed gets close to c, the pulses will be almost immobile in its reference frame (d-D will be almost zero). In other words, the speed of the pulses relative to the moving light source DECREASES. This does happen in the case of other waves but for light this decrease is an obviously false consequence of the assumption that the speed of light is independent of the speed of the source.
Conclusion: The speed of light does depend on the speed of the light source. The moving source sends faster light, not shorter wavelength. Insofar as its speed is concerned, both in gravitation-free space and in a gravitational field, light behaves like particles, not like waves:
Richard Feynman, "QED: The strange theory of light and matter", p. 15: "I want to emphasize that light comes in this form - particles. It is very important to know that light behaves like particles, especially for those of you who have gone to school, where you probably learned something about light behaving like waves. I'm telling you the way it does behave - like particles. You might say that it's just the photomultiplier that detects light as particles, but no, every instrument that has been designed to be sensitive enough to detect weak light has always ended up discovering the same thing: light is made of particles."
Banesh Hoffmann, Relativity and Its Roots, p.92: "Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether."
University of Illinois at Urbana-Champaign: "Consider a falling object. ITS SPEED INCREASES AS IT IS FALLING. Hence, if we were to associate a frequency with that object the frequency should increase accordingly as it falls to earth. Because of the equivalence between gravitational and inertial mass, WE SHOULD OBSERVE THE SAME EFFECT FOR LIGHT. So lets shine a light beam from the top of a very tall building. If we can measure the frequency shift as the light beam descends the building, we should be able to discern how gravity affects a falling light beam. This was done by Pound and Rebka in 1960. They shone a light from the top of the Jefferson tower at Harvard and measured the frequency shift. The frequency shift was tiny but in agreement with the theoretical prediction. Consider a light beam that is travelling away from a gravitational field. Its frequency should shift to lower values. This is known as the gravitational red shift of light."
Albert Einstein Institute: "One of the three classical tests for general relativity is the gravitational redshift of light or other forms of electromagnetic radiation. However, in contrast to the other two tests - the gravitational deflection of light and the relativistic perihelion shift -, you do not need general relativity to derive the correct prediction for the gravitational redshift. A combination of Newtonian gravity, a particle theory of light, and the weak equivalence principle (gravitating mass equals inertial mass) suffices. (...) The gravitational redshift was first measured on earth in 1960-65 by Pound, Rebka, and Snider at Harvard University..."