I made a statement a few days ago in another post to the effect that scientists are passionate about the real world as revealed by science. A commenter dubiously asked what, exactly, we really know.
The irony meter clanks loudly at a person expressing doubt in the verity or usefulness of scientific data only to promote supernatural explanations of natural phenomena instead. Claims of certainty where no knowledge actually exists is not a bad working definition of religion. Whatever the weaknesses of science, we know absolutely nothing whatsoever of any supernatural world (except that everybody's version of it is different and every attempt to verify "expertise" in the realm--or even the very existence of the realm--has been roundly debunked).
Still, questioning the verity of scientific results is absolutely fair game, even part and parcel of the methodology; and so, what of it? What DO we know (with an apologetic nod to those scientists who object to a lug with no science training such as myself attempting to answer)?
There are millions of scientific discoveries from the past century or two we might pick (it's always a shock to me to read history and see how utterly clueless we were--and not so long ago--about things which are now well in hand), but here's an especially good one: one established fact is that life exists on our planet in its present form by way of the process of evolution. We know this as surely as we know the constituent gases of our atmosphere or that the Earth is not flat. Indeed there is very little in our natural world which science has more thoroughly verified than the process of evolution. We don't yet understand every detail of the process (though we know a great many details), and we may not like the implications of it, but the fact that evolution has occurred--and is occurring--is beyond dispute.
Even the most fervent adherent to creation mythology (of which there are countless versions from which to choose) cannot dispute a few simple facts: that the characteristics of individuals of a given species occur with a natural degree of variance along a continuum of possibilities (people vary in their strength and stoutness, in their height, in their intelligence and keenness of smell and eyesight, in the length of their fingers and the cavity-resistance of their teeth, in the pigmentation of their skin, etc., etc.); that most of those characteristics are genetically heritable; that a species' environment is not static when looked at in geological timescales; and that the natural variation of a species makes certain individuals more suited to survival--and ergo reproduction--in a given environment than other individuals (especially in our ancestral environment--think 10,000 years ago). There are a million other details, but these above facts outline the whole banana. There's no getting around these, and with these you get evolution.
The reason the 747-being-blown-together-from-a-junkyard analogy (which is just an update of William Paley's original pocket-watch-in-the-woods scenario) does not hold water is twofold. First, it leaves the even larger question of where the watchmaker came from unanswered--indeed, blithely unaddressed. Thus our "answer" leaves us hanging with our original question and adds an additional problem to our roster, one which is inscrutable by design. (This is like drinking to make your problems go away. You wake up with the same unsolved problems, and now you have alcoholism to boot.) Some solution. Second, and more importantly, the demonstrated action of evolution shows that a "creator" is redundant (except perhaps as some ultimate prime-mover, though that only points us back to the futility of the plainly unknowable, at least at present).
Life takes an influx of energy from our sun--which is a finite resource, so the law of conservation of energy is not violated--and builds increasingly complex machinery by way of an arms race: the fitter variants bestow a survival advantage, and a population as a whole becomes statistically fitter for that environment over time. This happens gradually and continuously by tiny increments, and possibly occasionally by larger mutations. Look at the process closely and Darwin's discovery is undeniable. We debate some aspects Darwin's and other geneticists' works (gradualism versus punctuated equilibrium, for example), and scientists will continue to duly put these ideas in front of the firing squad as people test competing theories. But the mythologists' hopes that Darwin was wrong were dashed decades ago. (And it bears repeating that if creationist mythology is subjected to even a shred of the same scientific scrutiny that the doubters apply to Darwin their entire edifice disappears without so much as a puff of smoke.)
The complexities of life may LOOK like "design," but that illusion is precisely the point that Darwin, a fervent Christian, was making: what appears to have been designed is in fact the culmination of a very gradual process--a process we've each witnessed innumerable times even in our own lifetimes. We see variance everyday in disease resistance or vulnerability or in sports prowess or food tolerance, countless things. Look at dog breeding, at how trivially easy it is for us to artificially select characteristics we wish to favor (the whole panoply of dog breeds are a human contrivance). Natural selection works exactly the same way, except it's the environment that supplies the survival pressures.
The big picture of this process has not been easily won by humanity. Our brains are not equipped to process astronomical numbers, and it can be hard to wrap our intuitive heads around the work of billions of years. (One solution, of course, is to deny the billions of years--"if I can't grasp it it cannot be so;" this is called argument from personal incredulity.) But the logic of it is so well supported as to be irrefutable by any credible means.
There's no way for an untrained enthusiast such as myself to quickly summarize all this and do justice to the massive supporting data. Richard Dawkins, on the other hand, is a credentialed scientist, and he has done an astounding life's work of making this data clear to any who will read him. But there's the rub: it requires time and effort to work through this body of writings. Unfortunately, he is often criticized not by those who have troubled themselves to actually read what he has written but from a kind of creationist's Cliff-Notes summary of hoped-for weak points. Fundamentalists love to hate Richard Dawkins, as he has made a spectacular career of decimating the card-house of irrationality that their worldview requires. But Dawkins has a great talent for clarity and elucidation (making him uniquely suited to hold the position of Charles Simonyi Professor for the Public Understanding of Science at Oxford University, a position from which he has since retired after 13 brilliant years). I mention this because even if one discredits Dawkins (Darwin's discovery being now quite secure) one is only discrediting the popularization of the science and not the science itself. In that sense, this attention to Dawkins is misplaced. And I have yet to read a criticism of Dawkins (let alone Darwin) that floats a valid argument against his reasoning. Dawkins has been maliciously maligned now for a couple decades yet his position has never been stronger.
The march of rationality plods inexorably forward. As it does so, and as people see more and more the silliness of religious "authority" and the gaseousness of religious thinking, people are increasingly declaring themselves to be irreligious--"unaffiliated" is the largest growing religious group. This is good news--the sooner we leave religion behind, this artifact of humanity's childhood, the sooner we will solve our problems.