The water in your glass is older than the Sun

The Sun is about 4.6 billion years old. And yet part of the water in your glass already existed before it ever lit up.

In 2014, a team led by astronomer Ilse Cleeves published an elegant calculation in the journal Science. Earth's water carries a telltale proportion of deuterium, a heavy form of hydrogen. That excess could only have been manufactured in one place: the extreme cold of the interstellar cloud that later gave birth to the solar system. Ice formed at some twenty degrees above absolute zero, molecule by molecule, on grains of dust.

The disc of gas surrounding the newborn Sun was too warm to produce it. The study's conclusion: between 30 and 50% of the water in our oceans predates the Sun itself. Orphaned ice that survived the birth of the star, travelled aboard comets and asteroids, and ended up raining down on a temperate rock.

Every time you fill a glass, you are pouring molecules that were already there before the first sunrise existed. Water doesn't belong to Earth: Earth is, in part, simply its latest stop.