Pentcho Valev
2023-05-10 22:15:12 UTC
"But this seems to be nonsense. How can it happen that the speed of light relative to an observer cannot be increased or decreased if that observer moves towards or away from a light beam? Einstein states that he wrestled with this problem over a lengthy period of time, to the point of despair." https://history.aip.org/exhibits/einstein/essay-einstein-relativity.htm
Brian Greene: "Whether you run toward or away from a beam of light, its speed will be unchanged when you measure it...That's kind of crazy! How could a speed behave that way when it comes to the speed of light? And the answer is that space and time do not behave as we would think, based on everyday experience."
Brian Greene: "If space and time did not behave this way, the speed of light would not be constant and would depend on the observer's state of motion. But it is constant; space and time do behave this way. Space and time adjust themselves in an exactly compensating manner so that observations of light's speed yield the same result, regardless of the observer's velocity." http://www.pbs.org/wgbh/nova/physics/special-relativity-nutshell.html
For the sake of argument, I assume that "space and time do behave this way". Does this make the constancy of the speed of light plausible? No. An Achilles' heel remains.
An observer starts moving towards the light source, and the frequency at him shifts:
In accordance with the formula
(frequency) = (speed of light)/(wavelength),
either
(A) there is a shift in speed of light relative to the observer, proportional to the frequency shift,
or
(B) there is a shift in wavelength inversely proportional to the frequency shift.
The alternative (B) is obviously absurd so the speed of light remains variable, no matter how space and time are vandalized:
"Thus, the moving observer sees a wave possessing the same wavelength...but a different frequency...to that seen by the stationary observer." http://farside.ph.utexas.edu/teaching/315/Waveshtml/node41.html
Max Planck Institute for Gravitational Physics: "You can see for yourself that, once more, there is a blue-shift - the pulse frequency measured at the receiver is somewhat higher than the frequency with which the pulses are sent out. This time, the distances between subsequent pulses are not affected, but still there is a frequency shift." https://www.einstein-online.info/en/spotlight/doppler/
"Vo is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + Vo...The motion of an observer does not alter the wavelength. The increase in frequency is a result of the observer encountering more wavelengths in a given time." http://a-levelphysicstutor.com/wav-doppler.php
"The Doppler effect is the shift in frequency of a wave that occurs when the wave source, or the detector of the wave, is moving. Applications of the Doppler effect range from medical tests using ultrasound to radar detectors and astronomy (with electromagnetic waves)...Moving Observer. Let's say you, the observer, now move toward the source with velocity Vo. You encounter more waves per unit time than you did before. Relative to you, the waves travel at a higher speed: V' = V+Vo. The frequency of the waves you detect is higher, and is given by: f' = V'/λ = (V+Vo)/λ." http://physics.bu.edu/~redner/211-sp06/class19/class19_doppler.html
"The wavelength is staying the same in this [moving observer] case."
Pentcho Valev https://twitter.com/pentcho_valev
Brian Greene: "Whether you run toward or away from a beam of light, its speed will be unchanged when you measure it...That's kind of crazy! How could a speed behave that way when it comes to the speed of light? And the answer is that space and time do not behave as we would think, based on everyday experience."
Brian Greene: "If space and time did not behave this way, the speed of light would not be constant and would depend on the observer's state of motion. But it is constant; space and time do behave this way. Space and time adjust themselves in an exactly compensating manner so that observations of light's speed yield the same result, regardless of the observer's velocity." http://www.pbs.org/wgbh/nova/physics/special-relativity-nutshell.html
For the sake of argument, I assume that "space and time do behave this way". Does this make the constancy of the speed of light plausible? No. An Achilles' heel remains.
An observer starts moving towards the light source, and the frequency at him shifts:
In accordance with the formula
(frequency) = (speed of light)/(wavelength),
either
(A) there is a shift in speed of light relative to the observer, proportional to the frequency shift,
or
(B) there is a shift in wavelength inversely proportional to the frequency shift.
The alternative (B) is obviously absurd so the speed of light remains variable, no matter how space and time are vandalized:
"Thus, the moving observer sees a wave possessing the same wavelength...but a different frequency...to that seen by the stationary observer." http://farside.ph.utexas.edu/teaching/315/Waveshtml/node41.html
Max Planck Institute for Gravitational Physics: "You can see for yourself that, once more, there is a blue-shift - the pulse frequency measured at the receiver is somewhat higher than the frequency with which the pulses are sent out. This time, the distances between subsequent pulses are not affected, but still there is a frequency shift." https://www.einstein-online.info/en/spotlight/doppler/
"Vo is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + Vo...The motion of an observer does not alter the wavelength. The increase in frequency is a result of the observer encountering more wavelengths in a given time." http://a-levelphysicstutor.com/wav-doppler.php
"The Doppler effect is the shift in frequency of a wave that occurs when the wave source, or the detector of the wave, is moving. Applications of the Doppler effect range from medical tests using ultrasound to radar detectors and astronomy (with electromagnetic waves)...Moving Observer. Let's say you, the observer, now move toward the source with velocity Vo. You encounter more waves per unit time than you did before. Relative to you, the waves travel at a higher speed: V' = V+Vo. The frequency of the waves you detect is higher, and is given by: f' = V'/λ = (V+Vo)/λ." http://physics.bu.edu/~redner/211-sp06/class19/class19_doppler.html
"The wavelength is staying the same in this [moving observer] case."
Pentcho Valev https://twitter.com/pentcho_valev