One of the questions I like to pose in my classes is “how do you know?”  Doing analysis of data and possible decision leads to lots of wild speculation, and this question sometimes brings us back to recognizing that widely held theories are actually quite tenuous.  One observation can bring down a whole theory, a “black swan” event.  I like to use examples from physics, even though I am not a physicist, because I find that students often think that we “know” stuff there.  Science is settled, even if other areas are not.

Here is an interesting (to me) article about measuring light and comparing the measurements to accepted physical theories.  At the end, something to think about:

There’s also a possibility that the explanation could be even more far-reaching, such as that the universe is not expanding and that the big bang theory is wrong.

How certain are you of the things you know?