A pair of silver-studded blue butterflies

© Misja Smits/Minden Picture

The butterfly effect. Silver-studded blue butterflies

The butterfly effect is a scientific concept coined 50 years ago today, now a widely-used term to describe how the smallest change may have worldwide implications. Mathematician and meteorologist Edward Norton Lorenz theorised that the flapping of a butterfly's wings, like those of the silver-studded blue butterflies you see in today's image, could, weeks later, influence the formation of a tornado.