The terms "faith" and "proof" have come up again and again, and they have been quite abused, so let's take just a moment to clear up those waters.
First, faith. The problem here stems from our usage of different definitions of the same word. In my context, and what I think should be the proper context for this discussion, this is the definition of faith:
Belief that does not rest on logical proof or material evidence.
Using that definition, there is a tremendous difference in a belief that is supported by logic or evidence (such as the belief that the Earth is round), and one that is not supported by logic or evidence (such as the belief that God created the Earth and all living things 10000 or less years ago). Some of you insist that you must have "faith" that the observations are correct, that the equations are accurate, that our understanding is not flawed. In my opinion, the above definition is the correct one in this case. You do not need "faith" to "believe" they are true, because by definition you believe based on logical proof or observational evidence, thus not by "faith."
Now, there are other definitions of "faith" as well. I think this is the one some of you would rather use in this discussion:
Confident belief in the truth, value, or trustworthiness of a person, idea, or thing.
In that context, then yes, you must have faith that your experiment was accurate, you must have faith that the measurements were not erroneous, you must have faith that your understanding is correct. Indeed, you must have faith that the Earth is round. You must have faith that the sky is blue. You must have faith that the people you speak to every day actually exist.
Do you see where that is going? That definition does nothing to clarify the discussion, and in truth that definition is synomous with "belief" in general. In my opinion, there is a distinct difference between "belief" and "faith" (one is true for anything, the other is true only for things which have no logical proof or evidence). The only reason that definition exists is because of popular usage. If you insist on declaring that I must have "faith" that the experiment was accurate, then I'll reply that you must also have faith that the experiment was carried out... faith that there are actually people to carry out the experiment and things actually exist to measure.
If used in that context, it becomes an absurd regression of dependencies. Everything then must be accepted on faith, and the word itself loses any useful meaning. And that, Gato Solo, is precisely the point I was making earlier. You have two choices: to accept (to believe) that everything you observe is real, or to reject it. There is no absolute proof (and we'll get to that in a moment). If you reject it, then you are the only real thing (or, at least your mind is), and you are a solopsist. I would argue that there has never been a human that truly believed he/she was a solopsist... our minds are not made for such a worldview. Your alternative then is to accept (believe) that the world is real, that other people are real, that there are things to measure, and the experiments actually do happen. This does not require faith in my opinion (since I believe the second definition is useless), only the intelligence to reject the absurdity of the solopsist viewpoint.
So which is it? Is the world real? Are experiments and observations (and the observers) real? If so, then the results of the experiments are real, and you have no more grounds for rejecting their reality than you do for rejecting the reality of the experiment itself. Validity of the results is bordering on the discussion of "proof," which I will get into next.
Relevant definitions of "proof":
The evidence or argument that compels the mind to accept an assertion as true.
The validation of a proposition by application of specified rules, as of induction or deduction, to assumptions, axioms, and sequentially derived conclusions.
A statement or argument used in such a validation.
Convincing or persuasive demonstration: was asked for proof of his identity; an employment history that was proof of her dependability.
Determination of the quality of something by testing; trial: put one's beliefs to the proof.
Law. The result or effect of evidence; the establishment or denial of a fact by evidence.
So, hopefully we have established that it does not require faith to accept that the material world and observations about it are real. What then, about the accuracy or validity or proof of such observations?
We are now firmly in the realm of epistemology. Let's start with a simple example. You might be surprised how blurred the lines between "real" and "true" (or proven) become. I show you a rock on the ground, and ask you if it is real. You respond that it is, and I ask you to prove to me that it is real. You say that you can see it, and I respond that you might be fooled or tricked somehow. You say that you can kick the rock and feel it, and I respond that your brain might again be fooled. In fact, your concious perception of the world is just a rendered representation based on sensory inputs to your brain. There is no guarantee, at all, that the inputs are accurate or that the rendering is accurate.
So where does that leave us? Back at the beginning. You must either accept that the rock is real, based on physical evidence, and declare that that is proof enough, as much as there ever will be, or you accept that nothing but your mind is real. Look at the definitions above. Where, in any of those, does it say that proof is evidence in absolute certainty, beyond any doubt? It doesn't, because such a thing does not exist.
It is a fallacy that some people believe "proof" to be that which is absolute. So, what then have we defined "proof" to mean? Precisely what is stated above. When physical or logical evidence strongly supports an idea, then it has been proven. There is no other definition. There is no absolute thing. The English language does not even contain a word that has the meaning some of you are attempting to use.
RD_151, you especially seem to be hung up on this usage of proof. Has it been proven that the world is round? Of course. Is that proof absolute, beyond any doubt? No. Is the usage of "proven" still correct in that context? Yes, because that is what we have defined the word to mean.. It is not my usage that is incorrect, but yours. Historical evolution is proven. Both the observational evidence and and the logical argument are there. The definition of the word is fulfilled.
It sits uneasily in your mind for me to speak of Evolution being proven, becuase you wish for the proof to be absolutely certain, beyond question. However, you are simply deluding yourself to think that there any such things. You are holding Evolution to a higher standard then you are anything else in the real world. Why?
Now, it is another matter entirely to say that the Evolution of life from non-life is proven. It is not, and science does not declare that it is. There are compelling arguments for it, and indeed one such compelling argument is that there are not alternative explanations currently, but that alone isn't enough to prove the theory, therefore science still regards that aspect of evolution as unproven. If you are going to argue that Evolution is not proven, or that the age of the Earth (within a given certainty band) is not proven, you must separate and specifiy precisely what you are referring to.