Since 1969, scientists have bounced lasers off reflectors left on the Moon to measure its distance to the centimeter. The verdict: it's receding by about 3.8 cm a year, roughly the rate your fingernails grow. Tides are to blame, and they're slowly lengthening Earth's days too. In a few hundred million years, total solar eclipses will be gone for good.
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.