The author of the text below has unwittingly exposed a simple truth which is heresy in post-truth (Einsteinian) science. Speed of light and frequency vary proportionally (accordingly, the wavelength of light remains constant):
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." https://courses.physics.illinois.edu/phys419/sp2011/lectures/Lecture13/L13r.html
If a light source emits equidistant pulses and an observer moves towards the source
exactly the same conclusion can be reached. Speed of light and frequency vary proportionally for the observer, the distance between subsequent light pulses obviously remains constant.
It can be shown (I have done this elsewhere) that variations of the wavelength of light allegedly occurring in the Doppler-moving-source scenario and in the cosmological-redshift scenario are absurd:
Stephen Hawking, "A Brief History of Time", Chapter 3: "Now imagine a source of light at a constant distance from us, such as a star, emitting waves of light at a constant wavelength. Obviously the wavelength of the waves we receive will be the same as the wavelength at which they are emitted (the gravitational field of the galaxy will not be large enough to have a significant effect). Suppose now that the source starts moving toward us. When the source emits the next wave crest it will be nearer to us, so the distance between wave crests will be smaller than when the star was stationary." http://www.fisica.net/relatividade/stephen_hawking_a_brief_history_of_time.pdf
"The universe is expanding, and that expansion stretches light traveling through space in a phenomenon known as cosmological redshift." https://www.nasa.gov/feature/goddar...lore-galaxies-from-cosmic-dawn-to-present-day
"As light travels towards us from the distant galaxies, it is stretched over time by the ever expanding space it is travelling through. The longer it travels, the more the wavelengths are increased (reddened)." https://www.wwu.edu/astro101/a101_hubble_redshift.shtml
So there is enough evidence supporting the fundamental axiom of future, Einstein-free physics:
The wavelength of light is constant.
Here are corollaries of "The wavelength of light is constant":
Corollary 1: Any frequency shift entails (is caused by) a proportional speed-of-light shift.
Corollary 2: If the emitter and the observer travel towards each other with relative speed v, the speed of light relative to the observer is c' = c+v, as posited by Newton's theory.
Corollary 3: Spacetime and gravitational waves (ripples in spacetime) don't exist. LIGO's "discoveries" are fakes.
Corollary 4: Light falls in a gravitational field with the same acceleration as ordinary falling bodies - near Earth's surface the accelerations of falling photons is g = 9.8 m/s^2. Accordingly, there is no gravitational time dilation.
Corollary 5: The so-called cosmological (Hubble) redshift is due to the speed of light gradually slowing down as light travels through vacuum, in a non-expanding universe.
Corollary 6: The dark sky in the Olbers' paradox can be explained by two facts. 1. Low-speed, high-redshifted light (known as CMB), coming from very distant sources, is invisible. 2. Beyond a certain distance, the star light does not reach us at all (its speed relative to us is reduced to zero).