SCIENCE
The smell of rain: is it really possible to smell it before it comes?
Many people claim to be able to sense the arrival of rain before it actually starts to fall. The reason, they explain, is in the smell in the air, different from all others, that lets them know when a storm is imminent. But is this really possible?
Surprisingly, when we ask science, we find that there is indeed evidence to support this claim. The reasons are basically chemical in nature, as IFLScience well explains, and have to do with rain particles in the soil and the wind.
It is therefore not a question of a super power or a superior perceptive ability but, according to the current data, merely a natural effect.
The smell of rain: is it really possible to smell it before it comes?
Many people claim to be able to sense the arrival of rain before it actually starts to fall. The reason, they explain, is in the smell in the air, different from all others, that lets them know when a storm is imminent. But is this really possible? Surprisingly, when we ask science, we find that there is indeed evidence to support this claim. The reasons are basically chemical in nature, as IFLScience well explains, and have to do with rain particles in the soil and the wind.
The importance of the "petrichor"
The word petrichor comes directly from the Greek 'petros', meaning stone, and 'ichor', the fluid that flowed through the veins of ancient pagan deities. The word refers to that familiar and inexplicably satisfying scent that is released from the ground after a heavy rainstorm, especially after a long dry spell. The term was first coined in 1964 by mineralogists Isabel Joy Bear and Richard Thomas. Until recently, it was not clear why this smell was satisfying. Then, in 2020, a team of researchers discovered that animals also love this smell.
Why do we find it so attractive?
The scientific reason is that a very normal soil bacterium, Streptomyces, produces a substance called geosmin. It is precisely this smell that attracts us so strongly. In fact, the noses of humans are so well trained to pick up traces of this substance that it is better than the ability of sharks to smell blood in the water. Bacteria therefore create geosmin to attract animals - especially insects and other invertebrates, but also larger animals - which coat themselves with its spores and then disperse them over wider distances.
How does it work at the chemical level
During a thunderstorm, as researchers studied in 2015, water droplets hit a surface and then flatten out, trapping pockets of air in the pores of the earth. These pockets escape from the water and turn into aerosols. In the process, they pick up everything on the ground, including our geosmin, which can be transported enormous distances by air, even kilometres away. It is plausible to think that it is these specific particles that are perceived by our noses when smelling the rain on the horizon. This explanation would also be perfect for understanding the reason why bacteria have been detected very high up in the atmosphere, as the tiny microorganisms are carried by the winds.
The importance of the ozone
The presence of ozone in the wind is another indicator that helps us notice an impending storm. This specific chemical element has a much sweeter smell than the vaguely earthy one usually associated with petrichor.
Why does ozone alert our noses to rain?
Ozone is made up of three oxygen atoms (O3). It occurs naturally, but can also be created by electricity, such as lightning or an artificial source, which separates the nitrogen in the atmosphere from the oxygen molecules. The smell of ozone in the air can indicate the approach of a thunderstorm, as the atmospheric current of the disturbance sends ozone down to ground level, where humans can pick it up.
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It may sound like a trivial question, but in fact it is not trivial at all; on the contrary, it holds within it very important physical and philosophical questions. The Washington Post noted that this question is stirring up some of the people on Twitter these days.
The debate was generated by a tweet from journalist Jacqui Deevoy, who wondered how it was possible that the sun had 'changed colour' from what she remembered as a child. The answer, however, is one that leaves one somewhat appalled, as there is no real unequivocal answer.
After all, children do not make a mistake by drawing the sun as a big yellow ball, but it is not a completely right answer. After all, light is just the perception of the wavelength of radiation emitted by the sun, and therein lies the whole secret.