The answer would be Nicholas Coperniucus
Most likely gravity, because the gravity would pull it off course or wobble.
Answer:
You take the light from a star, planet or galaxy and pass it through a spectroscope, which is a bit like a prism letting you split the light into its component colours. "It lets you see the chemicals being absorbed or emitted by the light source. From this you can work out all sorts of things," says Watson
The ratio of the speed of light v in a medium to the speed of light in a vacuum c is called its Refractive Index n
v/c=n
Different substances have different Refractive Indices (plural of Index). Values are always bigger than 1.
Refractive index of water is 1.33
Refractive index of glass is about 1.4
Sometimes, because acceleration due to gravity on Earth depends on how close you are to the Earth's center.
