Thanks to weather and the water cycle, you are likely drinking water that has passed through a dinosaur. Thanks to the water cycle that moves water in and through the air and the ground, it is very likely your next sip of water will have passed through the mouth of a dinosaur too.

Getting very technical, the atomic mass of hydrogen is 1.00784 u and that of oxygen is 15.9994 u. Therefore, the molecular mass of water with formula H2O is (2 × 1.00784 u) + 15.9994 u = 18.01508 u. Therefore, one molecule of water weighs 18.01508 u, and one mole of water weighs 18.01508 grams. A mole is defined as Avogadro’s number of particles of any kind of substance (atoms, molecules, or ions). Avogadro’s number is approximately 6.022 × 1023. Thus 18.01508 grams of water contain 6.022 × 1023 water molecules. A glass of water, or 200 grams of water, therefore contains 6.6855 × 1024 water molecules. The total mass of the hydrosphere is about 1.4 × 1024 grams, and thus the total hydrosphere contains about 7 × 1021 glasses of water (with 200 grams of water in each).

Therefore, if the water molecules in a glass of water were spread evenly throughout the entire hydrosphere, you would find around 1000 of those molecules in any glass of water. As a result, it’s nearly 100% likely that water that moved around during the age of dinosaurs is in that glass of water you’re drinking.

Dinosaurs roamed the earth during the Mesozoic era which lasted roughly 186 million years. This is in sharp contrast to the relatively short period human beings have been around, which is about 200,000 years.  Because of that time span, statistically, it is many more times likely that you’ve sipped water that passed through a dinosaur than water passed through another human being.