Odorless gases, the atmosphere and sense of smell.
Our atmosphere is odorless. And no I dont mean the smells you get in polluted areas, or around agricultural land or near the sea where the salt and seaweed... these are chemicals floating through the air. I mean that nitrogen, oxygen and carbon dioxide (in its present minimal concentration) are odorless gases which constitute the majority of the atmosphere.
But is it really odorless? When you sit in a room with a certain smell, at first it is strong and after a while you adapt and cannot perceive it anymore. What if that room was a room you have been in your whole life. If nitrogen or oxygen or carbon dioxide or water vapour had a smell we wpuldnt even know. Our olfactory brain requires a "baseline" from which to detect other smells. This baseline I would imagine is perceived as "odorless" to maximise other smell sensations by contrast.
But, that does not mean this baseline is in fact without smell but rather this smell is undetectable.
My support for the argument is that;
a). If you increase the concentration of carbon dioxide (such as dry ice) to a quantity much greater than what is normally expired (roughly 4%) .... you can "smell" the carbon dioxide. But because oxygen and nitrogen are already present at high concentrations I would say it's hard to get the same effect.
b). Consider an alien lifeform that comes from a planet made of 60% ammonia gas, 25% chlorine and 15% CO2 (assuming hypothetical that a type of life could exist in such conditions). It arrives on earth having an olfactory "baseline" odourlessness from its atmosphere. It cannot smell ammonia or chlorine. Whilst to us ammonia and chlorine have very distinct and harsh smells. Would they perceive oxygen and nitrogen to have a strange smell?
I would imagine yes. I see no reason why at first encounter with a chemical that your brain has never registered before it will come as a sensation which can only be known as a sort of smell.
But is it really odorless? When you sit in a room with a certain smell, at first it is strong and after a while you adapt and cannot perceive it anymore. What if that room was a room you have been in your whole life. If nitrogen or oxygen or carbon dioxide or water vapour had a smell we wpuldnt even know. Our olfactory brain requires a "baseline" from which to detect other smells. This baseline I would imagine is perceived as "odorless" to maximise other smell sensations by contrast.
But, that does not mean this baseline is in fact without smell but rather this smell is undetectable.
My support for the argument is that;
a). If you increase the concentration of carbon dioxide (such as dry ice) to a quantity much greater than what is normally expired (roughly 4%) .... you can "smell" the carbon dioxide. But because oxygen and nitrogen are already present at high concentrations I would say it's hard to get the same effect.
b). Consider an alien lifeform that comes from a planet made of 60% ammonia gas, 25% chlorine and 15% CO2 (assuming hypothetical that a type of life could exist in such conditions). It arrives on earth having an olfactory "baseline" odourlessness from its atmosphere. It cannot smell ammonia or chlorine. Whilst to us ammonia and chlorine have very distinct and harsh smells. Would they perceive oxygen and nitrogen to have a strange smell?
I would imagine yes. I see no reason why at first encounter with a chemical that your brain has never registered before it will come as a sensation which can only be known as a sort of smell.
Comments (4)
There's two factors to consider:
1. Genetic propensity to overemphasise smells of dangerous smells;
2. Familiarity with abundant smells.
As an example of [1], humans have a considerable overreaction to the smells of human and pig faeces, a mild reaction to dog and cat faeces, and very little reaction to the faeces of other animals. This correlates to the fact that we are much more likely to catch diseases from human and pig faeces than dog and cat faeces, and somewhat more likely to catch diseases from dog and cat faeces than other mammals. Much of this increased likelihood is down to increased exposure (and the similarity of pigs to humans), but the trend is the exact opposite of the one you describe.
I just want to say faeces one more time before I finish up here.
I'm not so sure this is true. Parasites like round worm, guardiasis, cryptosporidium, toxoplasma gondii, ticks, fleas, cat scratch fever and the bacterial infections caused by the genera canimorsus, Pasteurella, Salmonella, Brucella, Yersinia enterocolitica, Campylobacter, Capnocytophaga, Bordetella bronchiseptica, Coxiella burnetii, Leptospira and Staphylococcus intermedius, as well as noroviruses, rabies and severe allergic reactions to hair, urine and skin are all transmitted/induced to humans via cats/dogs.
Considering the substantially greater time we spend in close contact to domestic dogs and cats than to pigs one would imagine the incidences of transmission are relatively high.
The issue is not our proximity to pigs, but the commonality between human and porcine digestive systems and diets and our proximity to humans. The pig thing is just a byproduct of the fact that we're overwhelmingly more likely to catch disease from human faeces than from that of dogs and cats: that's why wr have sanitation.
And likewise overwhelmingly more likely to catch disease from dogs and cats than, e.g. farmyard animals, including pigs, unless we happen to be farmers.
I will say it again.
Faeces.