<p>&quot;<a href="https://en.wikipedia.org/wiki/Exosphere" rel="noreferrer">Exosphere</a>&quot; and &quot;upper <a href="https://en.wikipedia.org/wiki/Atmosphere_of_Earth" rel="noreferrer">atmosphere</a>&quot; are not always the same. When using the word &quot;exosphere&quot; certain properties are implied which are not necessarily implied by &quot;upper atmosphere&quot;.</p>
<p>Usually exosphere is used when referring to the outer most layer of Earth's atmosphere where the molecules are already in the free molecular regime with negligible collisions between them. When talking about other solar system bodies the exosphere might even the only existing atmospheric layer the whole atmosphere comprises of which extends directly to the surface of the body (e.g. when talking about the Moon) - but it has there again fundamentally the same properties as Earth's exosphere.</p>
<p>Similar argument on physical grounds applies to the other commonly-used atmospheric layers, the thermosphere, mesophere, stratosphere and troposphere. E.g. the upper boundary of the troposphere depends on geographical latitude, thus the definition of &quot;low&quot; would depend on where you are on Earth.</p>

CC BY-SA 4.0
2024-10-24T14:25:21.920Z
This pattern appears quite often in medical and scientific literature.  The words get their definitions from the needs of experts, and often lead to confusion for those who have not yet reached that point.   Scientific names for animals are a good example.  Another good example might be the "distal head of the ulna" rather than "forearm bone near the wrist."  The former is confusing to many (including myself!), but is very helpful for doctors, especially when conveying medical records *unambiguously* to another doctor.
Cort Ammon
CC BY-SA 4.0
2024-10-25T16:56:40.410Z
Vice versa, the exosphere might not even properly exist within the planetary gravity well - for exoplanets with vigorously escaping and ionized (hence collisional) atmospheres, the gas mean free path might never reach the local scale height.
AtmosphericPrisonEscape
CC BY-SA 4.0
2024-10-23T13:57:09.787Z
2024-10-23T13:57:09.787Z
planetmaker
<blockquote>
<p>Wouldn't it be simpler to just say &quot;low atmosphere&quot; (for non-exosphere atmosphere layers) and &quot;high atmosphere&quot; (for exosphere)?</p>
</blockquote>
<p>While this might be simpler, it is not at all useful. It is not that hard to learn a new word. It is important to distinguish that the Earth's atmosphere has multiple layers, with the exosphere being the highest layer.</p>

CC BY-SA 4.0
2024-10-23T07:31:43.990Z
I didn't say or thought that learning a new word is hard (in a language I speak good enough at least). What I say is that often times, longer terms are much more clear or accurate and cause less confusion or disagreement, take for example the term `work`: Is prostitution work? For many it isn't but for some it is, but no one will disagree that prostitution is an `income source`, so in this case more is less. Anyway, if the exosphere is the highest layer of the atmosphere, then I think that I just misunderstood the original parcellation of the term atmosphere.
not_a_scientist
CC BY-SA 4.0
2024-10-23T07:33:09.870Z
I did hear an aeronautics PhD saying "lower atmosphere" and "upper atmosphere"  once, but that was probably done practically because he spoke to a general audience.
not_a_scientist
CC BY-SA 4.0
2024-10-23T07:44:13.173Z
@not_a_scientist If it was indeed an aeronautics PhD, that person probably lumped the thermosphere and exosphere into one category ("upper atmosphere") and everything else into another category ("lower atmosphere"). A large number of artificial satellites orbit in the thermosphere.
David Hammen
CC BY-SA 4.0
2024-10-23T06:15:27.793Z
2024-10-23T09:44:09.813Z
2024-10-23T09:44:09.813Z
David Hammen
<p>I get the impression that the term exosphere only complicates the already complex discourse around how to define the layers of earth's atmosphere (and atmospheres in general), and more so, the work of teaching and accessing knowledge about them to general audience, hence I ask: Wouldn't it be simpler to just say &quot;low atmosphere&quot; (for non-exosphere atmosphere layers) and &quot;high atmosphere&quot; (for exosphere)?</p>

CC BY-SA 4.0
2024-10-23T12:00:36.707Z
Upper/lower or high/low are probably quite ambiguous... Where would the limit between the two be? "Lower atmosphere" often means just the troposphere, but different people probably place the limit at different places depending on their use. There's a clear and well-defined term, why not use it? And why focus on just exosphere? Why don't you have a problem with the other layers' names?
jcaron
CC BY-SA 4.0
2024-10-24T22:59:50.743Z
What kind of "harm" might it do? This seems akin to the discussion about whether the word construction "quantum supremacy" has somehow mysteriously bad attributes that influence the listener, and demands that it be replaced with "quantum advantage", which sounds like a washing powder.
David Tonhofer
<atmosphere><terminology>
Are there planetary scientists who suggest that the term "exosphere" does more harm than good?
not_a_scientist
# Are there planetary scientists who suggest that the term "exosphere" does more harm than good?

(Asked by: username_0 on 2024-10-23)

I get the impression that the term exosphere only complicates the already complex discourse around how to define the layers of earth's atmosphere (and atmospheres in general), and more so, the work of teaching and accessing knowledge about them to general audience, hence I ask: Wouldn't it be simpler to just say "low atmosphere" (for non-exosphere atmosphere layers) and "high atmosphere" (for exosphere)?

**Tags:** atmosphere, terminology

> **Comments:**
> **username_1**: Upper/lower or high/low are probably quite ambiguous... Where would the limit between the two be? "Lower atmosphere" often means just the troposphere, but different people probably place the limit at different places depending on their use. There's a clear and well-defined term, why not use it? And why focus on just exosphere? Why don't you have a problem with the other layers' names?  
> **username_2**: What kind of "harm" might it do? This seems akin to the discussion about whether the word construction "quantum supremacy" has somehow mysteriously bad attributes that influence the listener, and demands that it be replaced with "quantum advantage", which sounds like a washing powder.  

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## 2 answers

### Answer by username_3 on 2024-10-23. Score: 9

"[Exosphere](https://en.wikipedia.org/wiki/Exosphere)" and "upper [atmosphere](https://en.wikipedia.org/wiki/Atmosphere_of_Earth)" are not always the same. When using the word "exosphere" certain properties are implied which are not necessarily implied by "upper atmosphere".

Usually exosphere is used when referring to the outer most layer of Earth's atmosphere where the molecules are already in the free molecular regime with negligible collisions between them. When talking about other solar system bodies the exosphere might even the only existing atmospheric layer the whole atmosphere comprises of which extends directly to the surface of the body (e.g. when talking about the Moon) - but it has there again fundamentally the same properties as Earth's exosphere.

Similar argument on physical grounds applies to the other commonly-used atmospheric layers, the thermosphere, mesophere, stratosphere and troposphere. E.g. the upper boundary of the troposphere depends on geographical latitude, thus the definition of "low" would depend on where you are on Earth.

> **Comments:**
> **username_4**: This pattern appears quite often in medical and scientific literature.  The words get their definitions from the needs of experts, and often lead to confusion for those who have not yet reached that point.   Scientific names for animals are a good example.  Another good example might be the "distal head of the ulna" rather than "forearm bone near the wrist."  The former is confusing to many (including myself!), but is very helpful for doctors, especially when conveying medical records *unambiguously* to another doctor.  
> **username_5**: Vice versa, the exosphere might not even properly exist within the planetary gravity well - for exoplanets with vigorously escaping and ionized (hence collisional) atmospheres, the gas mean free path might never reach the local scale height.  

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### Answer by username_6 on 2024-10-23. Score: 6

> Wouldn't it be simpler to just say "low atmosphere" (for non-exosphere atmosphere layers) and "high atmosphere" (for exosphere)?

While this might be simpler, it is not at all useful. It is not that hard to learn a new word. It is important to distinguish that the Earth's atmosphere has multiple layers, with the exosphere being the highest layer.

> **Comments:**
> **username_0**: I didn't say or thought that learning a new word is hard (in a language I speak good enough at least). What I say is that often times, longer terms are much more clear or accurate and cause less confusion or disagreement, take for example the term `work`: Is prostitution work? For many it isn't but for some it is, but no one will disagree that prostitution is an `income source`, so in this case more is less. Anyway, if the exosphere is the highest layer of the atmosphere, then I think that I just misunderstood the original parcellation of the term atmosphere.  
> **username_0**: I did hear an aeronautics PhD saying "lower atmosphere" and "upper atmosphere"  once, but that was probably done practically because he spoke to a general audience.  
> **username_6**: @username_0 If it was indeed an aeronautics PhD, that person probably lumped the thermosphere and exosphere into one category ("upper atmosphere") and everything else into another category ("lower atmosphere"). A large number of artificial satellites orbit in the thermosphere.  

---

