Advent calendar door #18: Who's looking at you?
"Observers, of course, are important in all of physics," says Jim Hartle, Professor of Physics at the University of California, Santa Barbara. This is because predicting, making and comparing observations is fundamentally how physics is done. We (or rather, our fellow human physicists) use theories to predict what our observations will be and we test these theories by checking if the observations that are predicted match what we actually observe.An observer doesn't necessarily have to be a human being, says Hartle, they just need to be what he calls a information gathering and utilising system (IGUS for short). "It could be a computer; it could be a collection of human beings pursuing science; it could be beings on other planets."
So the idea of an observer is a very general one in science. "We have theories to explain experience and we test them by how well they explain that experience." An observer is always central to that idea, but the question is: is what we see dependent on what kind of observer we are? Or are we somehow on the outside looking in?
Find out more about the wonders of observation, and the link to quantum mechanics, in this article.