Our leisure time is important to us. Many leisure activities – watching television, marvelling at a firework display or having a round of golf – would not be possible without the help of some amazing science and technology.

Golf balls
Golf is one of the most popular sports in the world and key to the game is the golf ball. Modern balls consist of two parts: the core and the cover. The core is made of rubber or a similar compound. Sometimes the core is wound with rubber thread, and sometimes it is solid.

The cover is made from either an ‘elastomer’ or a ‘thermoplastic’ material. Each has its own special properties. The covers can be directly moulded onto the cores, or else formed as two half-shells that are then fused together around the core. The covers are dimpled. This improves the aerodynamic properties of the ball – reducing drag and increasing lift so that it flies further and higher.

Plasma TVs
Unlike a conventional TV, a plasma screen TV does not rely on a bulky cathode ray tube, which fires streams of electrons from the back of the TV on to the screen at the front. Instead it consists of a flat panel containing tens of thousands of tiny chambers or cells, each holding a gas.

When the gas is excited by an electric current, it causes the cell to glow a particular colour. The cells are sandwiched by a grid of tiny wires, or electrodes. There is a cell at each point that the electrodes intersect. A computer switches on and off electric currents at each of these points thousands of times in a second. With tens of thousands of cells flashing on and off at different colours and intensities, moving images can be created.

Fireworks
Fireworks that shoot into the air usually consist of a shell of stiffened paper containing an explosive powder. Within this can be smaller shells, which will themselves explode in the air. There are also usually ‘stars’ – pellets of a mixture similar to that which makes up a sparkler. These ignite in the air and fizz and crackle.

The shell can be launched from a tube of card or metal containing a small amount of ‘lifting charge’. When the fuse is lit, the lifting charge takes the shell into the air and also ignites the shell’s fuse. This is timed to burn until the shell reaches a good height, when it will explode, releasing smaller shells, with their own fuses, and the burning stars.