Few ideas in modern science have reshaped our understanding of reality more profoundly than space-time—the interwoven fabric of space and time at the heart of Albert Einstein's theory of relativity.

For a century, quantum theory has passed every experimental test, but physicists can’t agree on how to use it to paint a picture of our reality – or even whether that is possible ...

This persnickety number determines the strength of magnetic fields. It figures in everything from motors and generators to ...