We all know we live in three-dimensional space. But what does it mean when people talk about four dimensions? Is it just a bigger kind of space? Is it “space-time”, the popular idea which emerged from ...

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.

When you drill down into the very fabric of reality—where elementary particles make up the matter that is you and me and everything around us in three-dimensional space—things get divided nicely into ...