A healthy person has 6,000 million, million, million haemoglobin molecules.

October 12th, 1999 was declared 'The Day of Six Billion' based on United Nations projections.

In the 14th century the Black Death killed 75,000,000 people. It was carried by fleas on the black rat.

Neutron stars are so dense that a teaspoonful would weigh more than all the people on Earth.

Inbreeding causes 3 out of every 10 Dalmation dogs to suffer from hearing disability.

Every second around 100 lightning bolts strike the Earth.

The speed of light is generally rounded down to 186,000 miles per second. In exact terms it is 299,792,458 m/s (metres per second – that is equal to 186,287.49 miles per second).

Microbial life can survive on the cooling rods of a nuclear reactor.