A giant lightning ball

A few years ago, a reader wrote to the 'Science Times' section of The New York Times about a lightning ball that was seen by her family to 'enter the glass front door, go right past us (or possibly even through us) in the living room and leave by the back window, where it hit a tree, causing some damage'. The Science Times commentator joked, 'Next time, take a picture', because it is one of nature's rarer phenomena and few photographs of it exist. It is also the least understood. Ball lightning...

From antimatter to mirror matter

The idea of a 'mirror world' was first suggested in 1956 by Chinese-American physicists Chen Ning Yang and Tsung Dao Lee. First, a tiny dose of particle physics, before you can enter their 'mirror world'. The universe is held together by four types of fundamental forces - gravity, electromagnetism, the strong force, and the weak force - which are transmitted or 'mediated' by the exchange of elementary particles. The gravitational force, or gravity, is the long-range force responsible for the...