Cleopatra (born 69 BC) lived about 450 years closer in time to the Moon landing than to the completion of the Great Pyramid of Giza (c. 2560 BC).
Atoms are mostly empty. Squeeze every human on Earth to the density of an atomic nucleus and all 8 billion of us would fit in about 2 cubic centimetres, the size of a sugar cube.
The oldest known living tree is Old Tjikko, a Norway spruce in Sweden whose root system has been dated to about 9,550 years. The trunk you see is much younger; the roots keep sprouting new ones.
A shuffled deck of 52 cards has about 8 × 10⁶⁷ possible orderings. The Big Bang was about 4 × 10¹⁷ seconds ago.
A day on Venus is longer than its year. Venus takes 243 Earth days to rotate once but only 225 to orbit the Sun.
The Great Wall of China cannot be seen from space with the naked eye. It is only 5 to 8 metres wide and roughly the colour of the land around it.
There are more possible chess games (Shannon's estimate: about 10¹²⁰) than atoms in the observable universe (about 10⁸⁰).
The Eiffel Tower is up to 15 cm taller in summer than in winter, because its iron expands in the heat.
Pi is transcendental: it is not the root of any polynomial with rational coefficients. That is why 'squaring the circle' with compass and straightedge is impossible.
Woolly mammoths were still alive when the Great Pyramid was built. The last population, on Wrangel Island, died out about 4,000 years ago, some 500 years after the pyramid was finished.
The human eye can register a single photon. In a 2016 experiment, people detected single photons slightly better than chance.
A single grain of sand contains around 10¹⁹ atoms, more than the number of grains on a large beach.