Obviously this is very different from what the man on the street means by truth. For the rest of us `truth' is a statement about reality, as things actually are rather than as they appear to be or we surmise them to be. But science deals only with what is measurable and what we can infer from that in the simplest possible way.
Science might be best compared to a court of law where one has to make a ruling from what little evidence is available. The court infers what happened and declares that to be the case, but we all know that courts are sometimes wrong. This is similar to science in that it reaches for truth as common man knows it but has only limited evidence, so it sometimes makes mistakes. For example, science once declared that man must have descended from a group of ancestors numbering in the millions spread all over the world, but now, in the light of new genetic evidence, scientists have declared that we may have had far fewer ancestors, perhaps just a single female ancestor in southern Africa. Or the leading theory of how the dinosaurs came to be extinct changes constantly from being outdone by mammals to ice ages to meteor collisions to major volcanic upheavals to whatever will be popular tomorrow.
Scientists in general overestimate the significance of what they do with respect to the truth and tend to ridicule anyone who disagrees with them. One form of dismissal comes from the skeptical creed that if science can't verify something then it is a meaningless statement. Such statements are used to attack religious beliefs, but of course skepticism holds as its basis a rejection of other ways to reach the truth such as revelation. That is, the skeptic assumes that only science is valid and then goes on to `prove' that other ways to know are invalid. Of course, any idiot can prove what he has already assumed to be true.
The reason skeptics so vehemently reject all revelation as a form of knowledge is because if they were to accept it they would have to accept that science does not always reach towards truth but in fact sometimes reaches towards fallacy.
To understand why this can happen we first have to understand the way in which scientists reason. The classic example of scientific reasoning starts with the simple fact that the sun has always risen in the past and so therefore we can infer that, almost certainly, the sun will continue to rise in the future. This is just simple inductive reasoning, but a scientist will go one step further and also conclude that it is therefore in the nature of the sun to rise in the morning. Now of course the sun only appears to rise, actually the earth is rotating. But the scientist claims that it is in the nature of something that is rotating to continue rotating. A child's top only slows down and stops because of friction. If we could eliminate all friction then the top could continue to spin forever because it is in the nature of something that is spinning to continue spinning.
Now we apply this to a little assumption underlying all scientific reasoning and see that it is sometimes impossible for science to reach the truth. The argument starts with the simple fact that since the universe exists at all we can conclude that it has never ceased to exist in the past (Since time is a part of the universe). This then allows us to infer that, almost certainly, the universe will continue to exist into the future. Now this is perfect inductive reasoning, but the scientist takes it further. The scientist also claims that it is in the nature of the universe to continue existing. The problem here being that the Church teaches that God is existence, and is the source of all existence. He created the universe out of nothing and it continues to exist only by force of His will. If God turned His will from the universe then it would cease to exist. In short, he universe continues to exist from moment to moment only by the will of God.
So we have here a case where not only is the scientist wrong, but it is actually impossible for the scientist to reach the truth through science alone. Conclusions such as the one about the will of God holding the universe in existence can only be reached through revelation. That is why skeptics hate revelation, to accept revelation one must first accept that science can lead us away from the truth.