Theoretically, then, scientists don't 'prove' anything, not to the extent that they wouldn't change their mind, if new evidence showed that they were wrong. There is no 'ultimate truth' in science, no dogma that's safe from questioning, and no questions that can't be asked.
Furthermore, science reserves its highest tributes to people who demonstrate that mainstream science has been wrong, in some respect. There's always a tendency to "go along to get along" in every organization, but science combats that by honoring successful mavericks far above their peers.
That's a big incentive for scientists to look for evidence that other scientists are wrong. While no one - scientists included - likes to think that they've been wrong, human beings have absolutely no problem demonstrating that someone else is wrong. And since science is based on demonstrable evidence, that's exactly what scientists can do.
Often, they've been successful, and mainstream science has changed. We know a lot more today than we used to know, and some of what we thought we knew, especially centuries ago, has been shown to be wrong. That's how science advances.
For proof of that, proof that we do know quite a bit, just look around at modern technology, all developed from scientific discoveries. We know we know a great deal, because we successfully use what we know. We build computers. We cure diseases. We fly to the Moon.
But religious believers sometimes take that beneficial aspect of science and turn it around. Science has been wrong in the past, repeatedly wrong, they say, so scientists are likely to be wrong now, too. Who knows what they'll believe in the future, so how can you believe anything they say?
Believers already know the truth, or think they do (note that they don't all agree on what that 'truth' is), and they'll stick with their dogma no matter what the evidence indicates. So you can count on them believing the same thing tomorrow that they believed yesterday. Why would you put your faith in scientists, instead, who'll likely believe something entirely different tomorrow?
I've heard this kind of thing from Christian apologist Eric Hovind, among others. Admittedly, Hovind is the kind of guy who can be easily refuted by an intelligent 11-year-old, but he's a good example of many apologists for religion. He prospers with a slick, practiced patter and boundless optimism. Like others, he tries to monopolize any debate, leading opponents down a particular path he's carefully constructed.
Tell me, are you familiar with Zeno's dichotomy paradox? I remember hearing that when I was a kid, and it really stuck in my mind. I knew it was wrong - heck, I could walk from one side of a room to the other and prove that it was wrong - but I didn't know why.
Well, I'm frequently reminded of that when I hear religious apologists today, especially those who claim they can use logic to prove that God exists. There's always a logical fallacy in their argument, but if you haven't encountered an argument before, it can be hard for most of us to pinpoint where it is. (Note that IronChariots.org is a pretty good resource for such things.)
In this case, though, Isaac Asimov wrote a superb rebuttal in 1989 titled "The Relativity of Wrong." I recommend that you read the whole thing, since it's short and clearly written. But in summary, it came about because he received a letter from an English literature major who tried to lecture Asimov about science!
The young specialist in English Lit, having quoted me, went on to lecture me severely on the fact that in every century people have thought they understood the universe at last, and in every century they were proved to be wrong. It follows that the one thing we can say about our modern "knowledge" is that it is wrong.
Asimov pointed out the fallacy in that, using the shape of the Earth as an example. We used to believe that the Earth was flat. Well, that was reasonable, given the limits of ancient technology, and it worked well enough for most purposes. Heck, it still works today. You don't have to carry a globe with you to navigate around town. A flat paper map still works perfectly fine.
Later, scientists determined that the Earth was spherical, and that was very useful when traveling long distances. Without that, we wouldn't even have attempted to circumnavigate the globe in wooden ships. Of course, as Asimov points out, that turned out to be wrong, too.
Oh, it wasn't too wrong. We discovered that the Earth was more like an oblate spheroid, since it bulges in the middle. But we still use globes to teach geography, since that's close enough. The difference from a true sphere is very, very small.
And even that turned out to be wrong, technically speaking, since we later (in 1958, thanks to the Vanguard I satellite) discovered that the Southern hemisphere bulges just a bit more than the Northern hemisphere. We're talking a matter of yards here, not anything really significant. But you could still say we'd been "wrong" about that, couldn't you?
So, scientists have repeatedly been wrong about the shape of the Earth. Quite true, technically speaking. But... could you then assume that almost anything really could be true, that there's no telling what scientists might think about the shape of the Earth in the future? Of course not!
My answer to him was, "John, when people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together." ...
In short, my English Lit friend, living in a mental world of absolute rights and wrongs, may be imagining that because all theories are wrong, the earth may be thought spherical now, but cubical next century, and a hollow icosahedron the next, and a doughnut shape the one after.
What actually happens is that once scientists get hold of a good concept they gradually refine and extend it with greater and greater subtlety as their instruments of measurement improve. Theories are not so much wrong as incomplete.
This is "the relativity of wrong," and it's a good way to look at science. Eric Hovind claims that scientists don't know everything (true), so we can't know anything (false). In the future, scientists may well revise their idea of the shape of the Earth once again, but only in tiny ways. Expecting that they might suddenly decide that the Earth is a cube,... well, I think we can all agree that that's ridiculous.
There are many other examples which demonstrate both the self-correcting nature of science and the relativity of wrong. For example, when prions were first proposed as a possible cause of Mad Cow disease, mainstream scientists were skeptical. After all, such a thing had not been demonstrated before.
But scientists looked at the evidence, and it was persuasive enough that this became mainstream science. Scientists had been wrong, or at least incomplete.
Keep in mind that this did not disprove the germ theory of disease, not at all. Medical researchers didn't have to throw out everything they thought they knew about smallpox, for example. This didn't change that at all. It was just a minor revision, or addition, to mainstream science.
Likewise, when scientists first suggested that a bacterium caused stomach ulcers, that went directly against mainstream medicine, which had long blamed stress and diet. But, again, the evidence was there, so this is now mainstream medicine itself.
But doctors haven't had to throw out everything they though they knew about medicine. Even what they thought they knew about stress is still largely intact. This was just a slight revision in the particular circumstance of stomach ulcers.
This is how science advances. We can be reasonably certain that we're wrong about some things we think we know, while still being quite certain that we're right about most things. After all, science is backed up by evidence. There's always a relativity of wrong, as science continues to revise our knowledge.
And that's a strength, not a weakness. If you think we might discover that the Earth is really cubic, or that evolution doesn't happen, or that the universe isn't billions of years old, well, you just don't understand science.
Furthermore, even if this were the truth, it wouldn't demonstrate that your god exists. You can attack science all you want, but it doesn't get you any closer to proving your religious claims, not one bit. God isn't the default answer when you don't know something. If we don't know, we don't know.
If you think you do know, then you must demonstrate why you think so - or, at least, why we should think so. And please, don't try to baffle me with bullshit, just show me the evidence.
Note: The other posts in this series are here.