Patsy Tollington, age 13, of Powell River, B.C., for her question:

Does air have weight?

Air is very light, but even a small amount of it has some weight. The air in a box one foot long, one foot high and one foot wide weighs about one ounce. This is at sea level. The higher we go, the lighter the air becomes because it gets thinner. One cubic foot of air is slightly heavier than a large feather. A sizeable roomful of air weighs about 200 pounds.

Now imagine the vastness of the whole atmosphere. It blankets the entire earth and reaches hundreds of miles above our heads. The tremendous weight of this air presses down on the whole earth. The air pressure over one square inch at sea level is over 142 pounds.

We live with this weight of the air pressing down on our bodies day and night. A fair sized man lives under air pressure of about 14 tons. We are so used to this weighty burden that our bodies do not notice it.