Space
Saturn would float in water
Saturn is mostly hydrogen and helium, giving it a density lower than water. Find a bathtub big enough and the ringed planet would bob on the surface.
More in Space
A day on Venus is longer than its year
Venus takes 243 Earth days to spin once, but only 225 to orbit the Sun — so a single Venusian day outlasts its year.
The Moon drifts 3.8 cm away every year
Tidal friction slowly pushes the Moon outward and lengthens our days. In the age of dinosaurs a day lasted about 23 hours.
The first photo of a black hole used an Earth-sized telescope
In 2019 eight radio observatories across the planet were linked into one virtual dish the width of Earth. It imaged M87*, a black hole 55 million light years away.
Time itself slows down near a black hole
Gravity stretches time. Watch someone fall toward the event horizon and they appear to slow, redden and freeze forever — while for them, the fall takes only moments.
Black holes slowly evaporate
Stephen Hawking showed black holes leak faint radiation and shrink. A stellar-mass one would take about 10^67 years to vanish — far longer than the universe has existed.
The farthest human object is still talking to us
Voyager 1 launched in 1977 and crossed into interstellar space in 2012. Its signal now takes over 22 hours to reach Earth.