The laws of physics are constant and unchanging . . . or are they? Researchers are beginning to find tantalising evidence that the physical constants of science might not be as absolute as we thought.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Robyn Williams: The point about constants in science is that they're supposed to stay, well, constant.

A variable's name is known as an identifier. The identifier given to a variable usually follows certain rules: It can contain letters and numbers but must start with a letter. It must contain at least ...