I rest my case. At least Rig Navigator answered my question rationally.
So based on that...
Because NASA says that space flight is possible, which I consider a reputable source along with a significant portion of the world's people, and that other reputable sources (Russian Space Agency, European Space Agency, Chinese Space Agency, Indian Space Agency, the Australian military, Fox News, CNN, Reuters, etc) say that it is possible and men have walked on the Moon; I accept that as valid evidence that it is true.