"The Comets Chart / Poster is 22.5x29 inches, (56x73cm). The Comets Chart dissects the nature and history of comets. Creaded in conjunction with comet experts the world over, it makes comets easily understandable to anyone. Interesting facts about comets abound. (Did you know that comets have not one, but two tails? Find out why on the chart!) This comet chart examines history of comet theories, from Aristotle's ""exhalations of the Earth"" to Fred Whipple's ""dirty snowballs."" A simply fascinating comet education!"