In Richard Dawkins' book A Devil's Chaplain there is a wonderful essay, Good and Bad Reasons for Believing that addresses the question: "How do we know?". His answer is, in short: Evidence.
At this point in human history we have built a huge web of supporting evidence for our models of the natural world. These models allow us to make reliable predictions, not only about the outcome of experiments, but also events in everyday life. Each of these successful predictions then becomes another bit of supporting evidence. This evidence, and the theories it supports, form the basis of much of human knowledge, technology, and our entire civilization.
From my point of view, as a physicist, it is remarkable that such a small number of rules allows us to understand so much of the complexity and wonder of the universe. In his introductory astronomy textbook, Michael Seeds puts it this way:
"By the end of my course, I want my students to know a few basic things: that they live in a very big universe that is described by a small set of rules; that those rules are knowable; that the human race has found a way to figure out the rules."
That way is science. Systematically following the evidence has allowed us to find some of the rules.
The purpose of this web site is to present the evidence for some of the things we all take for granted. I find this topic to be beautiful. Many people have trouble associating beauty with science but, like math, I find that science has a very powerful esthetic.
The layout and design of this site is very much uncertain. If you have any criticisms or suggestions, or if you stumbled just onto this site, please drop me a note to say 'hi' and let me know what you'd like to see!