A letter to Democritus describing the advancements made in atomic theory since his time might restate Democritus’s ideas before moving on to Lucretius, John Dalton, and the discoveries of J. J. Thomson and Ernest Rutherford.
In the fifth century BC, Democritus argued that the material world was made up of an infinite number of atoms. The Latin poet/philosopher Lucretius advanced atomic theory in the first century BC. Lucretius, too, believed the material world was the result of atoms. He also believed that atoms propelled entities such as the soul.
Centuries later, the English chemist Dalton helped people realize the complexity of atoms. Not all atoms are alike; different elements will produce atoms of varying masses and sizes. In 1803, Dalton’s work with atoms lead to his law of multiple proportions, which set a precedent for calculating the ratio of two elements that combine to form more than one compound.
At the end of the century, in 1897, Thomson discovered electrons. In the early part of the twentieth century, Rutherford, one of Thomson’s students, discovered the nucleus.