Our limitations don’t limit God.
I have a physicist friend that tells me that many modern “theories” in physics require such huge energies that they can never be tested. Is an untestable theory science at all? Or is it theology/philosophy/even an internally coherent fairy tale?
Ah, the friend of a cousin who’s aunt... May I suggest a very short and quite readable book, Science and Its Ways of Knowing, edited by J. Hatton and P. Plouffe. It contains a series of essays discussing science as a method and philosophy written by such luminaries as Sagan, Hawking, Popper, Gould, L. Alvarez, et al. It will help you understand the strengths and limitations of (for example) young vs. mature, data-driven vs. theory driven, and experimental vs. observational sciences.
You REALLY don’t understand Science, do you? Your physicist friend is right, and is most likely referring to M-theory (what used to be called String Theory). You’d need a particle accelerator the size of the Solar System in order to prove some of the implications of M-Theory. Perhaps the greatest difference between science and religion (other than science being based on observable, repeatable data, i.e. empirical evidence, and religion being entirely faith-based) is that science makes PROGRESS. Religion already claims to know all the answers, and thus it is static. Furthermore, if religion changes, then doesn’t this render it untrue as it has strayed from the original ONE TRUE WORD of God? How many times have religions been updated or changed during history?
OF COURSE a currently-untestable theory is science! Theories are the building blocks of science! The presently-untestable M-theory is a perfect example of this. Just because we can’t think of a way to test it NOW, science doesn’t just give up, or ascribe it all to a mythical supernatural force. Scientists continue to strive to find new ways to test, they just don’t give up, even if it takes generations to find the answer. A good analogy to the state of incompleteness M-theory now finds itself in would be the theory of electromagnetism. In the 19th century, they had theories for electricity and magnetism, and knew that both were related somehow. In 1864, James Clerk Maxwell published a paper with his now-famous equations that showed the relationship clearly. Unlike static religion, science has excellent prospects for solving problems, and, indeed has done more to alleviate human suffering than any religion is remotely capable of.
Science is a search for the ultimate Truth. Theories and hypotheses are presented, published for peer-review, and all those who read it try every way they can think of to DISPROVE the theory. If they cannot, then that hypotheses or theory becomes a stronger theory. Ultimately, as with thermodynamics, enough proof can be amassed to make it into a scientific Law.