What 'Being Relative' Means
From Human Destiny, a work by the French scientist Lecomte du Nouy, published in 1947 by Longmans, Green & Co. (emphasis in original):
"Certain of our mental illusions are due to the fact that we consider a phenomenon, as we observe it, in the frame of our current life. Motion in a straight line, for instance, is real with respect to the earth, and false with respect to the universe. This does not only apply to sensory illusions. It applies to all our human observations which are always relative to the system of reference chosen. By system of reference we simply mean the scale of observation. This demands an explanation.
"Let us suppose that we have at our disposal two powders. One white (flour) and the other black (finely crushed charcoal or soot). If we mix them we will obtain a gray powder which will be lighter in color if it contains more flour and darker if it contains more soot. If the mixture is perfect, on our scale of observation (that is, without the help of a microscope) the phenomenon studied will always be a gray powder. But let us suppose that an insect of the size of the grains of flour or of soot moves around in this powder. For him there will be no gray powder, but only black or white boulders. On his scale of observation the phenomenon, 'gray powder,' does not exist.
"The same is true of any print or engraving. When examined with a magnifying glass, the nose of George Washington will look to us like a succession of black and white points. Under the microscope, we will see nothing but the grain of the paper, gray, black, or white according to whether it has been covered by ink or not. The principal phenomenon, the design, the portrait of Washington, has disappeared. It only existed on our normal scale of observation.
"In other words, one can say that from the standpoint of man it is the scale of observation which creates the phenomenon. Every time we change the scale of observation we encounter new phenomena.
"On our scale of human observation, as pointed out before, the edge of a razor blade is a continuous line. On the microscopic scale, it is a broken but solid line. On the chemical scale we have atoms of iron and carbon. On the sub-atomic scale we have electrons in perpetual motion which travel at the rate of several thousand miles per second. All these phenomena are in reality the manifestations of the same basic phenomenon, the motions of the electrons. The only difference which exists between them is the scale of observation.
"This fundamental fact was first pointed out by a brilliant Swiss physicist who died in 1942, Professor Charles-Eugene Guye. It enables one to understand many things and to avoid grave philosophical errors."