They are admitting that aircraft "contrails" are gumming up the skies and
become indistinguishable from clouds. We will be stuck on this planet
without any knowledge of other worlds or stars or anything beyond our
chemmy skies ... But because of mind-conditioning, we will think we are in
a wonderful place and everything is just swell!

"Ground-based astronomy could be impossible in 40 years because of
pollution from aircraft exhaust trails and climate change, an expert says. 
Aircraft condensation trails - known as contrails - can dissipate, becoming
indistinguishable from other clouds."

http://news.bbc.co.uk/2/hi/science/nature/4755996.stm