Smoking, Drugs, and Alcohol mtroduction Once a hypothesis has been proposed, the question is always asked, "where is the evidence? The British scientist sir Humphry Davy once burned diamonds into graphic, ignoring the expense, to demonstrate that diamonds and graphite are both crystallized carbon, He made his point. Proof or evidence is usually the result of observation or experimentation, combined with reasoning. The theories that are accepted are those with the most supporting evidence, In the second century, Claudius Ptolemy proposed that the planets and the sun revolved around the earth. His theory was accepted because it predicted the position of the planets with some accuracy. But all "proofs" are tentative, to be discarded when another theory emerges that explains morefacts, Thirteen centuries later, the polish scientist Nicolaus Copernicus "proved" that the planets revolve around the sun by demonstrating that his theory explained things that Ptolemy's theory could not, like the seasons of the earth and the retrograde or backward motion of the plangts,then, in 1905 Albert Einstein shook everyone up by saying that motion is relative and that whether the sun is moving or the earth is moving depends on your point of view!And on and on we go, always striving to get closer and closer to the truth.