A Canary

Neither seen nor touched. Generally colorless, odorless, and tasteless. Neither solid nor liquid. Difficult to detect. We believe it exists.

It has a very low density and viscosity. As the ratio of its components change we sicken. Most changes in it are detrimental to our health.

It makes our biosphere possible. Its name is a word for breath.

We know that we can do better than to judge it by our sickness and death. We have used the sickening and death of animals to judge it, but know that we can do better.

We know that changes in its temperature causes great changes in its density, diffusion, and distribution, but are often careless of this knowledge.

We know elements of it are very reactive and are constantly interacting with everything in our biosphere.

It carries matter and material, bacteria and virus. It carries vapor, water, and ice. You are putting stuff into it now.

It changes form moment to moment and eon to eon.

Within a narrow range it supports human life and nearly all life here.

We have describe its pure nature and now a bit about its optimum nature.