Petrichor | Hacker News Reader

Petrichor

en.wikipedia.org

151 pointstosh44 comments

It appears humans are more sensitive to fresh rain on dry soil than sharks are to blood in the water. Fun to think of the evolutionary pressures there.

From the wiki, humans detect at 0.4 ppb and it appears sharks are at about 1 ppm. I can't find a proper source, but several articles say about a teaspoon of blood to an olympic swimming pool. https://www.sharktrust.org/shark-senses

> Fun to think of the evolutionary pressures there.

Savannah hominids obviously needed to run to the parking and put up the tops on their convertibles as soon as they scented rain?

By etymology, I'd consider magma to be a good referent for petrichor. Or at least the salty deposits left along contact surfaces of strike-slip faults?

It's a neologism.

I imagine the evolutionary benefit of the sensitivity is in avoiding drinking stagnant water, where the compound is also present: https://en.wikipedia.org/wiki/Geosmin

Hominids traveling deserts may need to quickly climb when rain starts falling. If you're not prepared, you can get swept away and even drown by flash floods in the dryest places on earth.

The "more people drown in deserts than die of thirst" factoid is not entirely made up; flash floods are incredibly deadly, especially so in areas where it doesn't rain much. Modern humans are quite good at surviving such events but I can definitely see (early) mammals struggle to survive them.

Maybe we like the smell and are sensitive to it due to its association with arable land?

Real question:

Are individual scent receptors evolutionary preserved, or is there enough "cross-encoding" either at the genetic level or the receptor level itself that preservation of a small number of survival-correlated scent receptors will, coincidentally, cause preservation of other receptors as well?

Could this just be the fact that air is less dense than water so (due to the densities of particulate) sensitivities must be tuned differently?

While petrichor is pleasant after a rain, according to the wiki article on geosmin it appears to also indicate poor water quality [0].

So perhaps the evolved sensitivity is to avoid stagnant water, rather than to seek recent rainfall. After all, for prehistoric hominids local recent rainfall is pretty obvious, and traveling large distances to distant rainfall is not usually practical.

[0] https://en.wikipedia.org/wiki/Geosmin

I always hated this word — it was made up in the 1960s, and it sounds to me like it is describing something disgusting that you’d scrape off the ground.

The pleasant smell of rain deserves a better word than ”petrichor”.

Heh. To me is sounds like some Victorian-era disease that requires a suitable balancing of humors and maybe a touch of bloodletting to cure.

Hah! I like your interpretation as well. “I’m sorry sir, it appears you are suffering from a case of petrichor. A bracing draught of brandy ought to put this right!”

OMG, I'm Greek the word sounded awfully lot ancient Greek to me and I heard it a couple of times, even misattributed to Ancient Greek scholars etc.

It is a portmanteau of "πέτρα (petra)" meaning "rock" and "ιχώρ (ichor)" which is the mythological golden substance in the blood of the Ancient Greek Gods. So this sounds all pretty Greek to me with all the quirky mythological stuff that come with the Ancient Greek but here the thing.

The first time people (some Australians) came up with the work was in a 60s issue of Nature http://dx.doi.org/10.1038/201993a0

Looking forward to tease my acquaintances that claim "our ancestors had such a diverse dictionary they even had a word for the pleasant smell of rain".

Petrifying to the core.

Or a music genre. “I’m mainly listening to petrichor these days.”

A fancy name for liquor on the rocks.

Living in the semi-arid American Southwest (about 15" of rain a year), the occasional brief-but-heavy rainfalls during late summer can give an overwhelming scent of petrichor. If walking or hiking outside, it's inescapable, since it literally comes from every patch of ground; and while pleasant enough in small doses, it can get strong enough that it feels hard to breathe, like walking through a desperate Macy's.

> like walking through a desperate Macy's.

Such an fitting description

Petrichor: why does rain smell so good? - https://news.ycombinator.com/item?id=20429952 - July 2019 (34 comments)

Slow-motion video of raindrops reveals how rain gets its distinctive smell - https://news.ycombinator.com/item?id=8912933 - Jan 2015 (20 comments)

What Makes Rain Smell So Good? - https://news.ycombinator.com/item?id=5583575 - April 2013 (23 comments)

The official term for the smell after it rains - https://news.ycombinator.com/item?id=1006923 - Dec 2009 (36 comments)

I went on a road trip once with a person who was born and raised in a large city, and we drove out into the country just after a rainstorm. It was summer and we could smell the rain on green leaves and soil smell. She said, "what is that wonderful smell in the air? I've never smelled anything like this." It was a really cool experience to be there and sort of experience it for the first time vicariously.

You can buy pure geosmin: https://pellwall.com/products/geosmin-10

Can they put it in a candle?

As all Australian know, one of the nicest scents on earth is gum trees (eucalyptus) after rain.

So that's why the planet in Risk of Rain is called Petrichor V !

i was just gonna say!! and with the remaster of the first game also

To go along with this: Psithurism

https://www.dictionary.com/browse/psithurism

not just after rain. i've noticed it early in the morning because of dew, albeit milder.

I smell Petrichor when my whole-house humidifier starts running after having been off for a long time.

This reminded me of the great song of Sadistik named Petrichor. Great rapper and lyricist. Highly recommended.

https://www.youtube.com/watch?v=un2wO_v35_I

Recent discussion with friends on petrichor, many didn't like it, but most are also city dwellers that mistakenly associates it with wet concrete/building materials. Opinions flipped when explained it was wet nature/soil.

Funny timing that this particular topic made it to HN. From the recently-released Season 4 of The Dragon Prince, this is one of the reasons Claudia is so infatuated with Terry, an Earthblood elf.

Adam Ragusea has 8 minute video on the topic: https://www.youtube.com/watch?v=_8vHsY_QVHM

”“A little-known piece of trivia,” Altman announced. “This smell, after it rains for the first time. You know what’s that called?”
“Is this going to freak me out?” Williams said.
“Petrichor,” Altman said. “It’s my favorite smell. You only get to smell this once or twice a year, because it has to not rain for a while, and then rain. It’s the smell of summers in St. Louis.”
“Petrichor?” Williams said, uncertainly.

“Petrichor,” Altman said.”

https://www.nytimes.com/2013/05/05/magazine/y-combinator-sil...

wonder if there is a cologne / perfume version of this smell

But of course! https://demeterfragrance.com/petrichor.html

He totally stole that from Neil Gaiman’s episode of Doctor Who (who certainly stole it from elsewhere)

https://tardis.fandom.com/wiki/The_Doctor%27s_Wife_(TV_story...

Haha, don't be silly, I remember watching that episode, it only came out a few years ago...

...wait...

I learn a lot of new words from Hello Meteor

https://www.youtube.com/watch?v=H-Q5mgYEwjk

I've first encountered this word in a Calvin and Hobbes strip.

Interesting, I first found the word in a Doctor Who episode. It was the favorite smell of one of the main characters of that season.

I wonder how many other different pieces of media have introduced others to the word

Not really a favorite smell, it was part of a passcode.

Don't forget the Paul Kelly song of the same name.

Also Ludovico Einaudi, where I first encountered the word "petrichor". https://www.youtube.com/watch?v=-8xeStLTnhM

And a great Phish song by that name too https://www.youtube.com/watch?v=gbMTa1yeSyw

And the 1975!

https://m.youtube.com/watch?v=0E_uK01odHg

Based on the context of the title, I had just assumed petrichor was the name of an artist or something. Glad to know the real definition!

There actually is one, quite liked his debut when it came out.

https://www.discogs.com/de/artist/3536488-Petrichor

Good to learn this today.

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