“It’s a brilliant surface in that sunlight. The horizon seems quite close to you because the curvature is so much more pronounced than here on earth. It’s an interesting place to be. I recommend it.” -Neil Armstrong
There are many impressive optical phenomena that we can see with our own eyes here on Earth. The right configuration of raindrops or ice crystals can produce rainbows, shining light through a prism will separate it into its individual wavelengths, and from high altitudes in the pre-sunrise or post-sunset skies, a full spectrum of colors become visible.
Yet despite the beauty and similarities of these phenomena, they don’t arise from the same physics. While ice, water, glass or acrylic will slow down light to anywhere from 66% to 76% of its vacuum speed, air itself will only knock it down to 99.97% of its initial value. In fact, you have to look extremely hard — and under ideal conditions — to see any evidence of atmospheric refraction at all.