Why the World Smells Different After It Rains

Behold, the wonders of petrichor.

"Petrichor" is the wonderful word that describes the wonderful scent of the air after a rain shower. It comes, like so many wonderful words do, from the ancient Greek: a combination of ichor, the "ethereal essence" the Greeks believed flowed through the veins of their gods, and petros, the stones that form the surface of the Earth. 

In the video above, PBS's Joe Hanson describes the biology that leads to petrichor. "When decomposed organic material is blown airborne from dry soil," he explains, "it lands on dirt and rock where it's joined by minerals. And the whole mixture is cooked in this magical medley of molecules. Falling raindrops then send those chemicals airborne, right into your nostalgic nostrils."

When it's not raining, though, that molecular mixture serves a different purpose: signaling plants to keep their roots from growing and their seeds from sprouting. No use wasting energy on all that, after all, when there's no water to be drunk. (Or, as Hansen puts it, "Petrichor: it's for the plant that's tired of waiting … to germinate.")

So why does the world smell different to humans after it rains? Because of plants, basically. 

Presented by

Megan Garber is a staff writer at The Atlantic.

How to Cook Spaghetti Squash (and Why)

Cooking for yourself is one of the surest ways to eat well. Bestselling author Mark Bittman teaches James Hamblin the recipe that everyone is Googling.

Join the Discussion

After you comment, click Post. If you’re not already logged in you will be asked to log in or register.

blog comments powered by Disqus

Video

How to Cook Spaghetti Squash (and Why)

Cooking for yourself is one of the surest ways to eat well.

Video

Before Tinder, a Tree

Looking for your soulmate? Write a letter to the "Bridegroom's Oak" in Germany.

Video

The Health Benefits of Going Outside

People spend too much time indoors. One solution: ecotherapy.

Video

Where High Tech Meets the 1950s

Why did Green Bank, West Virginia, ban wireless signals? For science.

Video

Yes, Quidditch Is Real

How J.K. Rowling's magical sport spread from Hogwarts to college campuses

Video

Would You Live in a Treehouse?

A treehouse can be an ideal office space, vacation rental, and way of reconnecting with your youth.

More in Technology

Just In