Apart from anything else, if you were to crop out or otherwise have shot the pic to eliminate the sky, you would have lost the entire dynamic of the tube, the claustrophobic quality of which only adds to the overall power of the image. For God's sake, why can't people see that? It's obvious, it's visceral: back to the fight to quitting the womb, or out of the egg or even the escape of the maggot from the bowels of the Earth!
It proves yet again what some of us here keep repeating: first impressions are very often the valid ones.
Rob C