[HerenIstarion]

Though not at knives with Kransha's and Boromir's posts as a whole, I feel obliged to add up a bit
Though in our world the terms at some points in history might have been interchangeable, it is not true for Middle Earth

Looking into etymology first (it can tell you a lot):

Religion: from Latin religare to tie back. With a meaning of 'to rely'
Science: from Latin scientia, from scient-, sciens ‘having knowledge’

Now it me be argued that whilst both religion and science are in possession and in search of knowledge, the types of knowledge they are after, and ends they try to achieve are quite different. Here and after,when I name both terms I mean some ideal type of both - ideal religion and ideal science.

For one, and as mentioned by Fordim, science seeks 'how'. Religion seeks 'why'
For two, finding out each and particular 'how', science seeks to increase man's control over object/principle studied. It is a proud trade. And it has same goals as magic may have had. Religion, in finding out 'why', dicreases the sense of control man may have had, teaching him to rely (to trust – estel). It is a humble trade
For three, object of science is Nature, it is locked withing the system it studies, hence it can not possibly learn anything about what is outside (and don’t feed me with parallel universes and M-theory, it still does not explain the Why, it simply moves it further back), object of religion is what is outside Nature, and can not be worked out by science as it is locked within.
And four – whilst science does not necessarily allow for the universe to be created, but is not able to prove/disprove it, the basic fact under religion is that universe is created, by rational Being, which is called God/Allah/Eru etc.

Indeed, science may be traced back to Aristotle’s empirism, and religion back to Plato. But it may be traced even further back, for, I suppose, since the very beginning the clash of two worldviews – the ‘materialistic’ and ‘idealistic’ one, must have been afoot

So far with preliminaries. Let us move to ME, now.

Funnily enough, situation as described, which is natural to our world, in Middle –Earth applies to ‘baddies’. Baddies of higher up (I would not be mistaken in naming Fili and Ki, blah, I meant, Morgoth and Sauron), strangely enough, as they’ve seen Him with their very eyes, cease to believe in Eru. At least, they cease to trust in Him, the do not rely on Him any more. Both loose their ‘religion’, but acquire ‘science’ – they learn how to control and manipulate. And truly, their ‘science’ is verily advanced. They use the control they gain against principle they forgot. The worship they request from their followers is not ‘religion’ either – as it is not based on trust but on fear.

‘Goodies’, on the other hand, have both, and in harmony. They retain ‘religion’ – knowledge of ‘why’, and rely on, trust in, if I may coin such an expression – the “Primaeval Why behind of all Hows”. Their ‘science’ and ‘religion’ are not at odds in their society, as they know that those two branches of knowledge do not intercept, really. The control they gain is used to support the principle they remember (That's why Galadriel rebukes Sam for terming her and Sauron's powers 'magick' alike)

So, the ‘interchange’, all of the ‘battles’ of science and religion in the past and in present are based on mere misunderstanding. It is like fighting over the question like to, say: Is my car faster or is you milk whiter?. How can you compare those two things? Both, both, your car is faster, and your milk is whiter, and they do not thread on each others toes at all

cheers