Spinning tops, gyroscopes, and scientific toys
In the Introduction to his book Spinning Tops, Professor John Perry (1850-1920 mentions the following:
I shall try to show you towards the end of the lecture that the fact of our earth's being a spinning body is one which would make itself known to us even if we lived in subterranean regions like the coming race of an ingenious novelist
The ingenious novelist Prof. Perry is talking about in his Introduction is Edward Bulwer-Lytton, and the novel is: The Coming Race. The story is about a highly developed subterranean race living in a network of caverns that discovered a superior form of energy they called Vril. What John Perry laments is that the author of The Coming Race apparently never realized that by simply closely observing a kid's toy like a spinning top, that superior and telepathic civilized people would have discovered that their caverns were spinning around a single axis.
The fact is that Leon Foucault (1819-1868), in the year 1851 demonstrated to the skeptic public --using a simple but big pendulum he constructed-- that the Earth rotates around its axis.
But Professor Perry, goes beyond the big scientific apparatus: he says that you don't even need a large pendulum to prove that the Earth rotates. A simple and small --but well constructed toy, like a top-- is enough to prove the rotation of the Earth around its axis.
He goes like this:
Obtain a gyrostat like this (Fig.) but much larger, and far more frictionlessly suspended, so that it is free to move vertically or horizontally. For the vertical motion your gymbal pivots ought to be hard steel knife edges. As for the horizontal freedom, Foucault used a fine steel wire. Let there be a fine scale engraved crosswise on the outer gymbal ring, and try to discover if it moves horizontally by means of a microscope with cross wires. When this is carefully done we find that there is a motion, but this is not the motion of the gyrostat, it is the motion of the microscope. In fact, the microscope and all other objects in the room are going round the gyrostat frame.Now let us consider what occurs. The room is rotating about the earth's axis, and we know the rate of rotation; but we only want to know for our present purpose how much of the total rotation is about a vertical line in the room. If the room were at the North Pole, the whole rotation would be about the vertical line. If the room were at the equator, none of its rotation would be about a vertical line. In our latitude now, the horizontal rate of rotation about a vertical axis is about four-fifths of the whole rate of rotation of the earth on its axis, and this is the amount that would be measured by our microscope. This experiment would give no result at a place on the equator, but in our latitude you would have a laboratory proof of the rotation of the earth. Foucault made the measurements with great accuracy
Spinning Tops is a book useful for young scientists and teachers. Fully illustrated with more than 60 pictures. Clean images and neat edition.