An example of a comparison based on a familiar everyday scale:
"If the sun were a large pumpkin, the Earth would be a pea, the moon a poppy seed, and the Empire State Building in New York about as small as the smallest bacteria we can see through the microscope.
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From the observed parallax, and the known diameter of the Earth's orbit, Bessel calculated that his star was 103 000 000 000 000 km away, that is, 690 000 times farther away than the sun! It is rather hard to grasp the significance of that figure. In our old example, in which the sun was a pumpkin and the Earth a pea rotating around it at a distance of 200 ft [feet, one foot is c. 0.3 m], the distance of that star would correspond to 30 000 miles [a mile is c. 1600 m]!
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In our old simile, in which the Empire State building was symbolised by a bacterium, the Earth by a pea, and the sun by a pumpkin, the galaxies might be represented by giant swarms of many billions of pumpkins distributed roughly within the orbit of Jupiter, separate pumpkin clusters being scattered through a spherical volume with a radius only a little smaller than the distance to the nearest star [other than the Sun]. Yes, it is very difficult to find the proper scale in cosmic distances, so that even when we scale the Earth to a pea, the size of the known universe comes out in astronomical numbers!"
George Gamow (1961) One, Two, Three…Infinity. Facts and speculations of science, Revised Edition, Dover Publications, Inc., New York.
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