WEIGHT AND SEE
Wayne HarrisWyrick discusses the sky's weight in his Stargazing column
As the director of the Kirkpatrick Planetarium for several decades, I received many questions from kids on school field trips. They often centered around aliens: Do I believed they exist (I do), and do I believe they visit Earth (I don't).
One of the more interesting questions I ever received was, “How much does the sky weigh?” At first blush, it might seem that the answer is simple: nothing. That is not correct.
First, we need to define “the sky.” To answer this question, I count as “sky” our atmosphere and all the water vapor it contains. The Karman line, 60 miles above Earth's surface, defines the official boundary between our atmosphere and the edge of space, so that is what we have to weigh.
Sea level atmospheric pressure is 15 pounds per square inch, meaning every square inch of our planet's surface has 15 pounds of air above it. One square inch is roughly one-third to one-half the size of an adult thumb. That corresponds 60,217,344,000 pounds of air for every square mile. Earth has a total surface area of 201,061,929 square miles. Do the math. Our atmosphere weighs 12,107,415,343,900,000,000 pounds.
According to meteorologists, water vapor averages 0.04% of the volume of Earth's atmosphere. That means the sky holds 4,824,146,196 gallons of water. At eight pounds per gallon, that's another 38,593,169,564 pounds of water in the air.
Add it all up, and the total weight of our sky is 12,107,415,382,493,169,564 pounds, more than 12 quintillion pounds! I didn't say all of that at the time, because I can't multiply that quickly in my head. I simply told the child that it's more than all of us could hold.
Meteor shower: The Perseid meteor shower, one of the most active each year, peaks during the early morning hours of the 13th. It has a normal activity level of one or two meteors every minute, but a nearly full moon will block all but the brightest meteors.
Planet Visibility Report: As the month begins, Venus hides close the sun. Mars sits in the evening sky and Mercury in the morning sky. All three remain lost in the sun's glare all month. On the 30th, all three of those planets, plus the moon, cluster together within the span of a fist's width around the sun, whose light totally obscures the tight grouping. Jupiter and Saturn both rise during daylight and are visible after sunset for most of the night. Full Moon occurs on the 15th with new moon following on the 30th.