In 1936, Einstein worked out that a star could bend the light of another star behind it, even into a ring. He concluded there was little chance of ever observing it. But he was thinking of stars: with whole galaxies acting as magnifying glasses, the effect is spectacular. Today those rings and arcs help weigh dark matter and reveal very distant galaxies.
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.