Why can't anything travel faster than the speed of light? Do black holes really suck? These are just a few of the questions author and astrophysicist Jeffrey Bennett answers in his new book, "What is ...

String theory is perhaps the most high-profile candidate for what physicists call a theory of everything – a single ...

De Sitter space is a solution to Einstein's general relativity equations. It describes a universe with accelerated expansion, similar to what we observe today with dark energy.

However, all attempts to blend general relativity and quantum physics necessarily introduce deviations from Einstein's theory. Therefore, Einstein's gravity cannot be the ultimate theory of gravity.

Einstein’s theory of general relativity suggests that our universe originated in a Big Bang. But black holes, and their gravitational forces, challenge the limits of Einstein’s work.

Albert Einstein's discoveries changed our concept of gravity by adding revolutionary layers to Isaac Newton's theories. Here's what else Einstein did.

Scientists have found evidence that Einstein's general theory of relativity doesn't quite work in the distant universe.