Well as for the originally post that why there is the axiom "The more we know, the less we understand." But there are a lot of things we can deduce from what we know. One poster put the temperature of the sun. We can do a spectral analysis of the sun. (Using the EM spectrum) to find the approximate make up of the sun, and we can use what we know about the make to figure out how hot the sun is from that. (Usually in text book they give a range of error next to temperature.)
Also since we are using deduction to figure some of the "facts" out its not out of line for the facts to change especially with a new discovery. When I entered High School in the early 90's the expected age of the universe was a little over 110billion years, by time I graduated that changed to 50-to-60 billion and now consider 13.7billion years.
We still have to discover all the life inhabiting the Earth. We still know very little about the brain, we do have models but there are still a ton of questions with theories attached them.
Though I have to agree there is a lot of theories and models taught as fact, which only end up being tossed out. A good example of this is Clovis First, which after nearly a half century of being the model taught in school as how the North American region what inhabited, has been binned after new dating techniques proved the model is flawed. I remember a science teacher telling me in middle school. "You know all the stuff they taught you in science in grade school forget it because its wrong." The reason why I'm guessing it is taught as fact is: 1) The teacher was taught it as fact, or has a preference. 2) Some fields have so many competing models it is not possible to cover them all so the most popular/teacher preference is taught.
...I have to leave for work and this post is taking a life of its own. So I will end here.







