The presence and frequency of cosmic background radiation was suggested by calculations of the cooling of a black body. It was accidentally validated by Bell lab technicians puzzled that they couldn’t get rid off all the hiss in their horn antenna. The presence and frequency of this radiation points right back to the Big Bang. At some point, the evidence becomes so strong that we think we know something.
In the above case, the Steady-State theory was blown out of the water.
The argument that it is not possible for us to “know” anything as the term is operationally defined has merit, but leaves civilization blind and in chaos. One does what one can, and so far, we’ve done some amazing stuff with what ‘knowledge’ we’ve developed.
That is true. To quote David Bowie as Nikola Tesla from “The Prestige,” exact science is not an exact science. What is indisputable scientific fact one day is a laughable myth the next, as we stumble our way towards the truth over the generations. We laugh at what scientists used to believe, but future scientists will probably laugh at what we believe today.