“Give me a place to stand and I will move the earth!”
This is a legend ascribed to the famous Archimedes, genius of antiquity who discovered the laws of the lever. “Archimedes,” Plutarch says, “Once wrote to King Hiero of Syracuse, whose kinsman and friend he was, that this force could be used to move any weight. Carried away by the power of argument, he added that, were there another earth, he would go there and lift our own planet from it.”
King Hiero, who was absolutely astonished by the statement, asked him to prove it. In the harbor was a ship that had proved impossible to launch even by the combined efforts of all the men of Syracuse. Archimedes, who had been examining the properties of levers and pulleys, built a machine that allowed him to single-handedly move the ship from a distance away.
Archimedes knew that by applying a lever, one could lift the heaviest of weights by applying even the weakest of forces. One had only to apply this force to the levers longer arm and cause the shorter one to act on the load. He therefore thought that by pressing with his hand on the extremely long arm of a lever he would be able to lift a weight, the mass of which would be equivalent to that of the earth (For the sake of conceptual clarity, we shall take the “moving” or lifting of the earth to mean the lifting on the earth’s surface of a weight whose mass would be equivalent to that of the earth).
But, if this great scholar of antiquity would have known what an enormous mass the earth possesses, he would have most likely “eaten his words”. Let us imagine for a moment that he had at his disposal “another earth” and also the point of support he sought. Further imagine that he was even able to manufacture a lever of the required length. I wonder if you can guess the amount of time he would need to lift a load equivalent in mass to that of the earth, by at least a centimeter? Thirty million million years- and no less!!
Astronomers know the earth’s mass. On earth a body possessing such a mass would weigh in round numbers.
Supposing a man could lift only 60 kg directly, to “lift the earth” he would need a lever with a long arm that would be longer than the shorter arm by
You can easily figure it out that to have the end of the short arm rise by one centimeter; the other end must describe through space the huge arc of 1,000,000,000,000,000,000 km.
That is the colossal distance Archimedes would have had to push the lever to lift the earth by just one centimeter. So how much time would he need? Presuming Archimedes could have lifted 60 Kg one meter in one second- the work of almost one horsepower! – to lift the earth by just one centimeter, even then he would need 1,000,000,000,000,000,000,000 seconds
or 30 million million years. Though he lived to a ripe old age, Archimedes and his lever wouldn’t have lifted the earth by so much as even the thinnest of hair.
No artifices would have helped him to cut the time noticeably – despite all his brilliance. For according to the “golden rule” of mechanics, the mechanical advantage derived will always be accompanied by a loss in displacement, or, in other words, in time. Even if Archimedes had been able to push the lever with a speed of 0.34 km/sec the speed of sound, he would have lifted the earth by one centimeter only after 93,264,094,069,895.84265 years.
If he had pushed the lever with the speed of light, 300,000 km/sec, nature’s fastest possible – he would have lifted the earth by one centimeter only after ten million years of pushing.
– Lewis, Albert C. “Archimedes.” Encyclopedia of World Biography. New York: McGraw- Hill, Inc., 1973. vol. 1, pp.219-223.
– Various history books