Claudius Ptolemy
The 'great astronomer of antiquity', this second-century Egyptian's theories of the universe held sway for 1,500 years. However, he did most of his 'observing' in the library at Alexandria. Here he calmly lifted the work of an earlier Greek astronomer, Hipparchus of Rhodes. The fraud was not discovered until the nineteenth century when scientists re-examining Ptolemy's original data noticed that the Egyptian astronomer had a blind spot for stars clearly visible from Alexandria - but was remarkably well able to see those visible from Rhodes.

Galileo Galilei
Best known for dropping stones from the leaning tower of Pisa and saying the earth went round the sun, Galileo Galilei was the first to insist on experiment as the only way of discovering truth. But colleagues of the seventeenth-century Italian physicist had considerable difficulty in reproducing some of his results - because this colourful character tended to carry out experiments in his head, rather than in his laboratory. In one instance he graphically described the motion of a ball dropped from the mast of a moving ship. Challenged, Galileo admitted he had not actually carried out the experiment 'I do not need to,' he explained 'I can affirm that it is so because it cannot be otherwise.'

Isaac Newton
Boy genius, founder of physics, author of the theory of gravity. But this exemplar of modern scientific method was not above bolstering his case with false data when the real results fell short of expectations. To make his Principia of 1687 more convincing he 'improved' the accuracy of his measurements in studying the speed of sound and 'adjusted' his calculations in later editions.

Gregor Mendel
The Austrian monk who founded modern genetics was exceedingly precise in his studies of peas. In fact his results - which allowed him to identify dominant and recessive characters and predict the proportions in which these would appear in the offspring - were just too good to be true. Some kind historians suggest the monk was deceived by a well-meaning assistant who knew what was expected. Others say he fiddled the outcome himself.

Paul Kammerer
The sex life of toads was the undoing of this early-twentieth-century Viennese biologist. Kammerer wanted to see whether acquired characteristics could be inherited. His focus of study was the Midwife Toad. Because the species normally breeds on land, the male toad does not have 'nuptial pads' - rough patches on the hands to grasp the slippery back of the female while mating in water. So Kammerer forced midwife toads to mate in water for several generations and, lo and behold, the descendants came to be born with nuptial pads. But when the one remaining male specimen was examined by other scientists they found that the black colouring that marked the pad was nothing but India ink.

Cyril Burt
A pioneer of applied psychology and professor at London University, Burt's claim that intelligence is over 75-per-cent inherited served as a justification for Britain's inequality-ridden education system. But his massive fund of data (including studies of 53 sets of identical twins - the largest collection in the world) was pure fantasy. So were the 'co-workers' whose results he cited to give the impression of on-going research. The scientific and academic world was fooled for 30 years. Only after his death in 1971 was the embarrassing truth discovered.