How big?

I like metrology, as you probably know. Knowing quantity is essential when making decisions: "You strain out a gnat but swallow a camel"(Matthew 23:23,24)
This is my latest problem:
How much air is there?

Is there more water in the hydrosphere* than dry air in the atmosphere**?

*1.35 × 10^21 kg

**5.1352×10^18 kg

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Yes, more than thousand times.

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You checked it out at Wikipedia's. I expected you to think for yourself. Anyway, what I did not say explicitly was that I asked for the mass in kilogrammes. If I had asked for the volume, it would have been a serious problem. There is a correlation between mass and volume called density. When the density is zero, there is no air. Obviously there is no limit. As you rise to the universe. the air pressure will decrease. Nowhere will it be zero. Even the moon has an atmosphere. If there is a void volume in space, how do we measure it? Normally it is hard to detect zero. What is 'darkness' and 'silence' in absolute terms? Of course we can say "there is zero rhino present in the room right now". But that is not a metrological statement.The non-existing rhino