After Albert Einstein published his special theory of relativity in 1905, he spent the next decade trying to come up with a theory of gravity. But for years, he kept running up against a problem. He ...

PARTICULARLY since the introduction of the theory of relativity, the problem of the ether has been a bone of contention among physicists. They have been divided into two camps; one unwilling to let go ...

Surprising as it may sound, 107 years after the introduction of general relativity, the meanings of basic concepts are still being worked out. More than a century after Albert Einstein unveiled ...