Originally Posted by Aloysius

What you describe is not what happens when viewing ships. The ship disappears from the bottom up - with a large ship and calm sea you can see this with the naked eye. Use binoculars and you will see the ship as if it were closer, but the same amount of the bottom of the ship will be out of view. I strongly encourage you to try this yourself if you live close enough to a port - this is science from first principles, and all science is ultimately based on common sense and first principles.

The issue of atmosphere shouldn't be hard to understand - even if you don't like the term gravity you will notice that you don't float off into space, and neither does your car, nor the air that surrounds us. These things have mass. We can see that things with mass don't float off into space, and we call that gravity, but if you don't like that term you can call it Fred.