Peacgirl
You keep coming back to a zero time delay.
Every day in electronics the speed of electromagnetic waves in slower mediums than space are measured, it i routine.
Keep in mid visible light is only a small fraction of the entire electromagnetic spectrum. Radio waves are 'light', with different frequencies/wavelengths.
In common usage light can refer to the entire spectrum with visible spectrum boning specif.
Radio and TV station transitions are the same phenomena as visible light. So your idea would have to apply to radio and TV receivers. And your cell phones.
en.wikipedia.org
The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications.
A fundamental principle is that nothing propagates faster than the speed of light. Maybe some day, as of today there is no known way to get around that limit.
When you say zero delay you violate C.
Yes science questions and evolves. Some theories can be demonstrated and succeed, others do not.
As to light in the 19th century there were competing theories to explain electric and magnetic phenomena. Maxwell put it all together and succeeded. He predicted how light would propagate and C the speed of light as a constant. Eventually as technology evolved his theory was demonstrated. The rsult all the electronic technology we have today.
I see no way to take your father's thought experiment to actual physical testing.
It is not jut science when an engineer designs something it has to be testable.
Theories about airplane wings and lift had to be tested.