I don't know if this is right place to ask this question but its bugging me for a while. Quick Google search gives me values of density ($kg/m^3$) of some normal gases:

$O_2 (1.429), N_2(1.1651), CO_2(1.977), O_3(2.14),H_2O(0.013, \text{vapour})$

So we an see that $O_3$ is much denser than every other abundant gases. However we know that most of $O_3$ is found high up in stratosphere, while our abundant, less dense gases reside(mostly) comfortably in troposphere including water vapour which is least dense (than abundant gases). So it seems contradictory to me.

However if we treat gases as fluids, obviously according to fluid mechanics, more dense things should stay at bottom, and least dense things should stay at top (atleast hydrogen and helium stay at top.)

So please help me clear the confusion, and tell me if I misunderstood something!

  • 1
    $\begingroup$ physics.stackexchange.com/q/34733 and physics.stackexchange.com/q/460018 $\endgroup$
    – BowlOfRed
    Commented Dec 11, 2021 at 6:04
  • $\begingroup$ @BowlOfRed Thanks! It answered my question, now should I delete my own question? $\endgroup$ Commented Dec 11, 2021 at 6:29
  • $\begingroup$ @KshitijKumar there should be a "delete" choice at the "Share Cite...." line . The article in wikipedia makes it clear en.wikipedia.org/wiki/Ozone $\endgroup$
    – anna v
    Commented Dec 11, 2021 at 13:29
  • $\begingroup$ There's clearly an error in stating the density of carbon dioxide. The given value is for the solid phase, not the gaseous one. $\endgroup$
    – J.G.
    Commented Dec 11, 2021 at 13:32
  • $\begingroup$ Note that ozone is also found at ground level on sunny days when there are volatile organic pollutants present. $\endgroup$ Commented Dec 11, 2021 at 17:12

1 Answer 1


The natural production of ozone $O_3$ is with $O_2$ interacting with the ultraviolet radiation from the sun. And the amount of ultraviolet is very high in the upper atmosphere. Therefore, $O_3$ generation happens in the stratosphere. $O_3$ is unstable and will decay with a half life that has been measured from about 5 hours to as low as 30 minutes. So as the $O_3$ created in the stratosphere falls to the earth it decays rather rapidly. This results in a high concentration at the point of creation and roughly $0$ by the time it get to the surface.


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