How can you prove there is something in the air without being able to see it?

Answer 1

If you can smell it, hear it, or feel it.... it's there. Answer: As a starting point you can't see air so many of the tests to prove that there is air will serve to prove there is something in the air. Some pollutants are detectable using organoleptic analysis, that is, your senses can detect their presence. These would include coloured gases, dusts, and odorous materials. Others like the air's own components (e.g. radon and CO) are not visible or odorous. Plants react to contaminant as well. The whole sccience of phytotoxicology has grown to indicate long term impacts of pollutants (as an example ethylene is a growth hormone that impacts the length of stalks or the ripening rates of fruit). However, many impacts have impacts on the observer before these methods determine that there is a problem (You can be sick or dead from CO poisoning before you realize there is a problem.

Many chemical substances which might be present in the air react with other substances (e.g. hydrogen sulfide will react with silver to create black silver sulfide or sulfur dioxide will react with the water in your nose to create a burning sensation) but many chemical pollutants react too slowly to provide this type of maco effect and must be run through a sensitive analytical device to record their presence. Low level CO and hydrogen sulfide meters are examples of these. Interestingly enough these detectors sometimes employ laser beams which interact with the pollutants, either being reflected or absorbed, and these minute changes are recorded and analyzed to identify the contaminant. In a similar method, samples of the air can be collected in inert containers and run through laboratory equipment (GC/Mass Spectrophotometers) to identify the materials present

For lower levels the air is allowed to contact gels, filter or other collection systems to strip out small amounts of material over time until the concentration in the collecting medium is high enough to be identified by analytical methods.

Answer 2

You can prove that there is something in the air by conducting scientific experiments that measure changes in air pressure, composition, or movement. For example, using instruments like an anemometer to measure wind speed, or a barometer to measure air pressure, can provide evidence of the existence of air.