For many years now, I could not believe in gravity as much as light from the sun. If gravity is for real, why are the oceans, seas and big lakes form a dome or an arc? Water is supposed to seek its own level but an arc or dome is not a is not a level or flat as we are supposed to perceive!
Newton said it was due to gravity why the apple fell from the tree. Gee, the apple probably was ripe and due for harvest. That's the reason it fell because it could no longer sustain the atmospheric pressure compared to when it was still raw!
Remember that while you go higher into the atmosphere or higher from sea level your weight goes down. It is because there is less atmospheric pressure pressing you down on earth! When you go into outer space you are weightless, right? Why? There is no atmosphere or air pressure in the same way things are weightless in a vacuum!
Atmosphere is also related to having light from the sun or sunshine. We only have light as the other planets and satellites because they have some atmosphere! Have you ever wondered why it is dark at night when the sun is supposed shine on our entire planetary system? Light or sunshine only goes through when there is 'atmosphere'.
The speed of light will be correct when there is atmosphere. It goes a lot faster invisible and immeasurable to us in vacuum or when there is no atmosphere. This is the point where I contest existence of gravity and the alleged speed of light.