# Does Earth have a certain smell that we are used to, and cannot smell?

**URL:** <https://boards.straightdope.com/t/does-earth-have-a-certain-smell-that-we-are-used-to-and-cannot-smell/835925>\
**Category:** Factual Questions\
**Created:** [June 23, 2019, 10:08am UTC](https://boards.straightdope.com/t/does-earth-have-a-certain-smell-that-we-are-used-to-and-cannot-smell/835925 "2019-06-23T10:08:38Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\
**Post date:** [June 24, 2019, 12:34pm UTC](https://boards.straightdope.com/t/does-earth-have-a-certain-smell-that-we-are-used-to-and-cannot-smell/835925/21 "2019-06-24T12:34:25Z")

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> [@Just\_Asking\_Questions](#):
>
> Oxygen. You know how recognizable ozone smells? To someone not used to breathing it everyday, our planet must smell horrible

Oxygen is toxic to anything not adapted to it, just like chlorine and fluorine are to us. If they aren’t used to the oxygen our air it probably not only smells bad but is rapidly fatal at normal concentrations.

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**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\
**Post date:** [June 24, 2019, 1:13pm UTC](https://boards.straightdope.com/t/does-earth-have-a-certain-smell-that-we-are-used-to-and-cannot-smell/835925/22 "2019-06-24T13:13:23Z")

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> [@Riemann](#):
>
> What OP is (in part) referring to is habituation, a reduction in response to persistent presentation of a stimulus.
> 
> [Habituation - Wikipedia](https://en.wikipedia.org/wiki/Habituation)
> 
> But you also have to consider the evolutionary context. As Colibri points out, “Earth” is not one smell. There has obviously been no explicit selective pressure to distinguish between planets, but rather to distinguish (to whatever extent) among different smells that we encounter on earth. Still, given that we can distinguish a wide variety of smells, a strange planet would probably contain many distinctive smells that we could recognize; and habituation would certainly reduce our sensitivity to those smells if we lived there.

Just exactly right.

There is no selective pressure to develop the receptors and to devote the brain real estate to detecting the presence or absence of something that is _always_ the same (different than if its amount varies at least, the variation has been of some significance to actions made, and ultimately to better “fitness” reproductively).

And there is pressure to notice novelty, to notice that the concentration of certain potentially salient substances that do sometimes change has suddenly changed.

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**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\
**Post date:** [June 25, 2019, 1:27pm UTC](https://boards.straightdope.com/t/does-earth-have-a-certain-smell-that-we-are-used-to-and-cannot-smell/835925/23 "2019-06-25T13:27:12Z")

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You know how laundry detergent manufacturers like to claim they’re using a scent that mimics the scent of clothes dried outside on a line. What _is_ that scent of clothes dried outdoors? Like the scent of outside air that you can notice when someone comes in from outside.

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**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\
**Post date:** [June 25, 2019, 4:54pm UTC](https://boards.straightdope.com/t/does-earth-have-a-certain-smell-that-we-are-used-to-and-cannot-smell/835925/24 "2019-06-25T16:54:02Z")

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Sounds like a variation of the "If a tree falls in a forest … " thing. What if someone was around but they are deaf? Does it make a sound?

What if something is producing molecules that we are used to? Does it make a smell?

Like the tree falling thing, my answer is “Of course!”

Take a person and isolate them in an ultra-clean room for a week. Then let them go outside. They’ll smell stuff others around them won’t.

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