general relativity

Everyone knows what time is. We can practically feel it ticking away, marching on in the same direction with horrifying regularity. Time has enslaved the Western world and become our most precious commodity. Turn it over to the physicists however, and it begins to morph, twist and even crumble away. So what is time exactly?

This podcast featuring Paul Davies, a theoretical physicist and cosmologist at Arizona State University and Director of BEYOND: Centre for Fundamental Concepts in Science, explores this difficult question and accompanies our What is time article.

Time and space form the stage on which events unfold. But what if the stage itself becomes part of the action? We take a brief tour through the history of space and time and see how ideas have changed since the time of Isaac Newton.

Has the future already already been written? Is time just an illusion? Take a step outside of spacetime with cosmologist Marina Cortês to discover the block universe.

Fundamental physics says time is symmetric - so why does time move forwards for us in a block universe?

Is time real? Are we just puppets living out a future already written? Marina Cortês explains why she thinks time is fundamental and that we don't live in a block universe.

Marina Cortês is one of a growing number of physicists who believe time is fundamental. We ask her about the alternatives theories to the block universe, where time comes first.

Physics tells us that we live in a block universe, containing all of the past and all of the future. What does this perspective mean for our understanding of time, events, and free will?

What would happen if the Sun suddenly exploded? Einstein wondered the same thing, and completely changed our understanding of the Universe.

Astronomers have explained a strange effect observed in the vicinity of black holes.