An explorer in the Amazon came across a waterlily that doubled in size every 24 hours. If one day its leaves stretched two metres across, the next day they stretched four metres across.
He took it home and kept it in a pond. In exactly 30 days the waterlily had covered the entire surface of the pond. Pictures of the waterlily were printed in all the major newspapers.
Another man, a bitter rival of the explorer, called the newspapers to tell them that they were being fooled. He said he had seen the waterlily on the 27th day after it had been planted in the pond and it had not covered even half the pond.
He was later proved right, but the explorer continued to be honoured for his discovery. Why?