Three valid (truthfulness of the premises guarantees truthfulness of the conclusion) arguments:

Premise 1: The wavelength of light is invariable.

Premise 2: The formula (frequency) = (speed of light)/(wavelength) is correct.

Conclusion 1: If the emitter and the observer (receiver) travel towards each other with relative speed v, the speed of light as measured by the observer is c' = c+v.

Conclusion 2: 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. Gravitational time dilation does not exist - Einstein's general relativity is absurd.

Conclusion 3: The Hubble redshift is due to light slowing down as it travels through vacuum. The universe is STATIC, not expanding.

Pentcho Valev