"... If you insist on asking "why" then the laws of physics are always
going to lead you around the chicken-and-egg circle. The laws of
physics need to say what happens. They sometimes say how it happens.
The fundamental laws rarely if ever say why it happens. ... The
slightly different question 'how do we know' will get a lot more
traction. ..."
Thank you for another interesting observation, John. But the "why"
questions are often asked by students, and by most people. And
teachers answer them, without difficulties. For example:
*) Why do cars gain speed when moving downhill ? Because of the net
force. And we elaborate.
*) Why do we have day in New York when it is night in Tokio? Because
of the earth rotation. And we elaborate.
*) The shape of the moon changes from day to day; why is it so?...
etc. etc.