We all know what we mean when we say that something has happened — well, all except for theoretical physicists. That's because the notion of a "happening" becomes fuzzy when you go down to the foundations of the science. Find out more with these articles and videos.

Mathematicians are working hard to understand an impenetrable proof of the famous ABC conjecture.

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?

The possibility that there might be many parallel worlds has just become a little more likely.

Mathematical models predict how fast a rumour will spread and how many people it's likely to reach.

A model of the interaction between predators and prey explains why sometimes frogs appear to eat snakes.

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