What Makes Rain Smell So Good? | Hacker News Reader

What Makes Rain Smell So Good?

blogs.smithsonianmag.com

107 pointsbigalo9323 comments

I grew up in the tropics. The coming rain is easily sensed -- there's so much rain falling that at actually drives air from the upper atmosphere downwards ahead of it. A blast of cool, sweet air is a sign that the rain drops will be arriving in a minute or two.

God I miss it.

When I had a motorcycle I could tell when rain was on the way using a similar method.

Most of the time I could be home by the time the rain started.

If you live in a cold climate you may notice the smell of snow before it snows especially the very first snowfall of winter. Maybe I'll create my own word and call it pnemakruos or "ice breath"

Petrichor is one of the great neologisms of the English lexicon. An excellent word for an excellent, trans-cultural sensation.

Never thought I'd actually see this word used outside of an episode[1] of Doctor Who. That or maybe an episode of Jeopardy. It certainly doesn't appear to be a well known word.

[1]: http://en.wikipedia.org/wiki/The_Doctor%27s_Wife_(Doctor_Who...

I first heard it in Aesop Rock's song Tetra [1]: "surface from the cellar door like worms into the petrichor".

[1] https://www.youtube.com/watch?v=vkHMn8q6Jlg

"If this hypothesis is correct, then the next time you relish the scent of fresh rain, think of it as a cultural imprint, derived from your ancestors."

This is challenging the intelligence of it's readers. I thought that was actually the whole point of the article, and the premise rather than a doubtful conclusion? It spends the majority of it's paragraphs discussing what compounds the smell, which while really interesting, does not at all help explain why it smells good. Oh, so it's some oils, so what? Oils can smell greasy and funny. There's no such thing as a scent being inherently "good." It's all a product of our evolution.

It also doesn't answer my main question: Why does the air smell good right before it rains. I'm sure being able to smell rain coming had evolutionary advantages...but how does it work?

It's probably the smell of ozone and ions causing particles in the air to adhere to surfaces, cleaning it like how electrostatic air filters work.

http://www.madsci.org/posts/archives/1998-08/897083302.Ch.r....

Moist air coming down. Has the same effect, just less so.

Such is the dangerous appeal of (neo)Lamarckism. Epigenetic changes by mechanisms such as imprinting can lead down that primrose path easily.

While reading this article I was reminded of my reading of a science fiction novel sometime in the past, the author of which escapes me, where it was noted that interstellar travelers could identify which planet they were on by its distinctive smell for a short time before it drifted into background sensory experience and disappeared. If I remember correctly in this novel, Earth had an odor similar to excrement ;-)

I wonder if it has any basis in reality, like for example if long-term residents of the space station notice smells differently briefly upon returning planetside?

Interesting that we can detect it at very small concentrations. Maybe this is an adaptation from some proto-mammal or even earlier ancestor whose environment had few pockets of fertile ground, and detecting this smell was a good way to find food by homing in on high concentrations of plants. (It would not necessarily be just for herbivores. You could be likely to find the plants themselves, but also to find creatures who fed on plants.)

That part set off my BS detector actually. The article claims some humans can detect it in 5 parts per TRILLION. Is that even POSSIBLE?

More detail here: http://www.metafilter.com/122295/The-rain-in-Spain-smells-ma...

Or why not just buy it in perfume form (#020 Soaked Earth)?

http://cbihateperfume.com/premium-accord-shop.html

I've never really noticed rain to have a smell. Maybe I need to live in a drier place and get out more.

I know this doesn't really add anything to the discussion, but if there is someone else here who has no concept of that "sweet, fresh, powerfully evocative smell" I don't want them to feel alone.

Sure: my girlfriend always mentions the nice smell when it has rained while all I smell is the nasty smell of wet concrete.

I've never noticed the rain having a nice smell but that might be because I live (and always have lived) in a densely populated area (The Hague area in the Netherlands).

After a storm it smells like dead worms to me.

Putting something into words is always a translation: a part of original idea becomes understandable to others, the rest is lost.

It's useful to think in words, as you can effortlessly communicate your thoughts—at a price of keeping thinking within ‘translatable’ range.

From another angle, things we can approximate verbally are tempting to think about. But can we fully experience things while thinking?

Smell of rain was one of those magical things I couldn't verbalize. Now I know a word for it, and the mechanism by which it works. Oh well…

Is there really smell of rain ? I think it's more like smell of rain and sand mixed .

In my place here in India people generally spread water in front of their home and shop and if there is sand it smells similar to when it rains .

On a related note, apparently the earthy smell that appears after it rains is caused by actinomycetes: http://birdandmoon.com/intheair.html

I have always lived in cities so have assumed in the past that the glorious smell was something to do with water coming into contact with the concrete/tarmac/stone around me.

and also, i often wonder, what makes that grassy smell before raining?

Sounds (smells?) like that's just petrichor from downwind.

Yes I think this is it!

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