More trees on Earth than stars in the Milky Way

In 2015, a team coordinated from Yale University crossed satellite imagery with more than 400,000 measurements taken on the forest floor to answer a child's question: how many trees are there on Earth? The result, published in Nature, crushed every previous estimate: about three trillion trees. Three million million.

The Milky Way, by astronomers' best counts, holds between 100 and 400 billion stars. Do the division: for every star in our galaxy there are between ten and thirty trees. That comes to more than 400 trees per person.

The figure carries its shadow. The same study calculated that since the dawn of civilisation the Earth has lost nearly half of its trees, and that the count now drops by a net ten billion or so every year.

Even so, on the next clear night you have permission for a kind of reverse vertigo: for every point of light you see up there, there are ten trees down here, breathing in the dark.