"Scientists" once thought the earth was flat too remember twink?
Did they? I don't think that any serious scientist believed the earth to be flat, especially since around 300BC when the ancient Greeks showed not just that the earth was, in fact, (roughly) spherical, but actually calculated its circumference, with theoretical/philosophical arguments in support of a spherical earth date back to around 600BC.
But even if scientists did once think the earth was flat, so what? Scientists - the real kind, not the ones with quotes - don't claim to be infallible. They observe physical phenomena, formulate theories to explain them and use the theories to make predictions. If the predictions hold, the scientific community gains confidence in the theory. If the predictions don't hold, the theory is either adjusted to account for or explain the discrepancy, or it is abandoned if it cannot be fixed.
That's how science works. Mistakes don't doom science - they promote it, because they cause science to advance.