Exactly How Much Life Is on Earth?

According to a new study, living cells outnumber stars in the universe, highlighting the deep, underrated link between geophysics and biology.

What’s in a number?

According to a recent calculation by a team of biologists and geologists, there are a more living cells on Earth — a million trillion trillion, or 10^30 in math notation, a 1 followed by 30 zeros — than there are stars in the universe or grains of sand on our planet.

Which makes a certain amount of sense. The overwhelming majority of these cells are microbes, too small to see with the unaided eye; a great many are cyanobacteria, the tiny bubbles of energy and chemistry that churn away in plants and in the seas assembling life as we know it and mining sunlight to manufacture the oxygen we need to breathe.

Still, it boggled my mind that such a calculation could even be performed. I’ve been pestering astrobiologists lately about what it means. Could Earth harbor even more life? Could it have less? How much life is too much?

“The big take-home is this really sets up Earth as a benchmark for comparative planetology,” Peter Crockford, a geobiologist at Carleton University in Ottawa and the lead author of the report, which was published last month in the journal Current Biology, said in an email. The finding “allows us to more quantitatively ask questions about alternative trajectories life could have taken on Earth and how much life could be possible on our planet.”
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https://www.nytimes.com/2023/12/01/science/space/earth-biology-life.html?smid=em-share