On this, the third day of advent, we explore some strange consequences of general relativity on our concept of time.

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?