This is Richard Feynman in 1964. Simple, isn't it?
From Robert Krulwich:
Think about what he's saying. Science is our way of describing — as best we can — how the world works. The world, it is presumed, works perfectly well without us. Our thinking about it makes no important difference. It is out there, being the world. We are locked in, busy in our minds. And when our minds make a guess about what's happening out there, if we put our guess to the test, and we don't get the results we expect, as Feynman says, there can be only one conclusion: we're wrong.
The world knows. Our minds guess. In any contest between the two, The World Out There wins. It doesn't matter, Feynman tells the class, "how smart you are, who made the guess, or what his name is, if it disagrees with the experiment, it is wrong."
This is why you can trust the scientific consensus - oh, not to be true, necessarily, because it's not always true. But scientists change their minds when the evidence indicates that they've been wrong. So the scientific consensus is always the best guess we've got.
Compare this to religion. Religion does the first part just fine, the guessing. Then it stops. If the evidence indicates that their guess was wrong, they cling to that guess anyway. They just know that guess was right, whatever the evidence indicates.
They accept any evidence that backs up their guess, but deny any contrary evidence. They rationalize it. They build great edifices of religious logic to explain it away. In religion, changing your mind is heresy. The guess is everything, the evidence nothing.
This is not just in organized religion, either. It's natural in human beings to want to be right. It's natural to cling to our guesses, despite the evidence. That's why the scientific method had to be invented, because it's not natural. And even scientists are human.
So you won't get every scientist to go along with the consensus. Partly, that's the natural human response to cling to our preconceived notions. But partly, it's the fact that science rewards heretics - successful heretics, at least. You become famous in science by overturning established orthodoxy.
It doesn't happen very often, but the rewards are great to a successful heretic. So that, too, helps keep a certain percentage of scientists doubtful, even when there's abundant evidence backing up the consensus. That's a good thing, because it keeps science honest.
But for us laymen, there is no better explanation than the scientific consensus. If there's a consensus, that's the best explanation we've got, and the only rational position is to accept it, tentatively (as all science is tentative).
It doesn't matter if the consensus is about evolution, global warming, the Big Bang, the age of the Earth, or... whatever. We laymen should accept the scientific consensus as the best answer we've got. (In cutting edge science, where there is no clear consensus, we should simply reserve judgement.)
Is this so hard to understand? I don't think so. But apparently, it's hard to accept. We just really, really like our guesses.
PS. If you're wondering what "Feynman Chaser" means (I was), check this out.