How High Is the Sky? Can We Touch the Sky When We Ride in the Airplane?

When white clouds float in the sky, the blue sky looks very high.

But how high is it really?

The sky has no ceiling so no one can tell how high it is. The sun shines upon the air in the sky and makes it look blue. The blue sky is only 50 kilometres high. Beyond that there is very little air. Under a thousand kilometres, there is almost no air and the sky is very dark. Generally, an airplane can fly as high as over a dozen kilometres. if your each out for the sky when you ride in an airplane, you cannot touch anything.