Or is it weightless?
The sky does have weight. It is made of air and air is made of all kinds of gas molecules. Those gas molecules have weight!
If sky has weight, then how is earth carrying that weight?
Weight of the air is evenly distributed over the earth’s surface. Since air moves around easily, it presses on us from all the directions. If it was to be only on top of our heads, it would knock us down to the ground.
How much does air weigh?
The average weight of air that presses down on us (called air pressure) is 14.7 lbs (6.6 Kg) per square inch of earth’s surface. Which is roughly more than 11 billion billion pounds (5.2 million billion metric tonnes)
This means the sky weighs 14.7 lbs per square inch of earth surface which is roughly 11 billion billion pounds.
So, you can say that sky weighs one millionth of the mass of the Earth.
Which equals to 570,000,000,000,000 adult Indian elephants!