"Not defining evolution and then saying "it" is based on facts and physical evidence without stating such doesn't sound very scientific to me."
I am glad anonymous asked, because there seems to be a lot of confusion in the popular mind about what a biologist means when referrring to biological evolution.
Evolution as a word has a number of meanings, some more general than others. The most general meaning of the word is change through time. But when referring to biological evolution perhaps the most common today is that biological evolution(the type creating all the fuss) can be defined simply as a change in the genetic makeup of a population over time.
The National Academy of Science(1998) defines evolution as:
"..change in the hereditary characteristics of groups of organisms over the course of generations. (Darwin referred to this process as "descent with modification.")"
Note the reference to Darwin's geneological definition as descent with modification.
So biological evolution is not really about species but how about the genetic make up of populations and how this changes over time. This definition can be used to model and empircally test hypotheses about HOW evolution operates. It is after a conceptually trivial problem to demonstrate that biological evolution happens, I suggest a trip to the Science library on this point. So the issue for the scientist is explaining how evolution operates in different situations. Again a trip to your friendly neighborhood science library might be useful.
Incidentally this definition does not refer to the origin of life problem or the "big bang" or any of the other obfuscations creationists try to use when dealing with evolution.
I wonder what the definition of intelligent design is. Can IT be specifies in a way that allows empirical tests as to HOW intelligent design operates? How about creationism: can IT be defined in a way that allows empirical testing of the mechanisms of creationism? We can do that with evolution. Come on...after all what is good for the goose is good for the platypus.