In the early 20th century, many astronomers believed the Milky Way was the entire Universe, 'spiral nebulae' included. In 1924, Edwin Hubble measured the distance to variable stars in Andromeda: far too remote to belong to our galaxy. Overnight, the Universe went from a single galaxy to an ocean of them.
A large share of Earth's water molecules formed in the interstellar cloud that existed before the Sun was even born, more than 4.6 billion years ago. You are literally drinking a cosmic fossil.
By day, the Martian sky looks butterscotch because of fine dust hanging in the air. But at dusk, those same grains scatter blue light forward, creating a bluish glow around the Sun. Rovers have photographed these blue sunsets: the exact reverse of what we see on Earth.