Measured from the Big Bang's afterglow, the Universe expands at about 67 km/s per megaparsec. Measured with nearby stars and supernovae, it's about 73. Despite ever more precise instruments, the gap persists, though some teams dispute it. This 'Hubble tension' may hide a subtle error, or physics we don't know yet.
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.