Roemer was the first to measure the speed of light.
The two observers would each measure light to be the same. The speed of light is the same for all observers, regardless of their frames of reference.
That, no matter who measured the speed of a beam of light, the result would be the same. In other words, someone travelling at 99% the speed of light would measure the same speed as someone standing still (all realtive to the light source).
First of all, the conditions you suppose in the question aren't possible. You do not go faster than the speed of light. But to answer the question, I would remind you that one of the most impoortant foundations of the Theory of Relativity is that no matter how an observer is moving, and no matter where the light is coming from, every observer measure the same speed of light. So no matter how you were moving, light from the usual sources would pass by you at the speed of light. (That's the speed you would measure as the light sailed past you.)
Galileo attempted to measure the speed of light using lanterns positioned at known distances and observing the time it took for light to travel between them. He would uncover the lanterns simultaneously and use a telescope to try and detect any delay in the light reaching his eyes. However, his methods were not sensitive enough to accurately measure the speed of light.
No, a megaphone is a device used to amplify sound, particularly human speech. It does not measure light or speed.
Yes. If I saw you move past me at the speed of light, and at the same time, you were measuring the speed of light with instruments that you were carrying, you would measure the same speed of light that everybody always does, regardless of whatever speed you were zooming past me. And as you passed by a star or a street light, you would cast just as good a shadow as you ever did. Physics 101, Introduction to Relativity. Wierd stuff.
by getting boners.
Roughly speaking, light moves about a million times faster than sound in air.
Light is faster because speed does not move. Speed is a measure of the rate of movement but, in itself, it does not move - at all!
Light travels at about 186,000 miles per second
The speed of light isn't a distance so it has no length it is a measure of speed, which is roughly 186000 miles per second.