Physics was the discipline that studied the most general laws governing the motion of matter and the fundamental structure of matter.
As an admittedly imprecise but vivid analogy, the universe was like an infinite sequence such as [1, 2, 3, 5, 7, 11, 13...], while Physics was the discipline that studied the patterns within that sequence.
In the era when the spark of science had only just begun to kindle, while people were still arguing over 1 and 2, a physicist sitting beneath an apple tree was fortunate enough to count to 3. He thus concluded, "This sequence consists of all natural numbers such as 1, 2, 3..."
However, as technology advanced, so did methods of observation.
By Einstein's time, this physicist of the new age quickly discovered that the fourth term was not 4, but 5. The laws Newton had summarized applied only to the first three terms—in other words, under so-called macroscopic conditions.
To make his theory seem more convincing, he continued observing until the seventh term, the number 13. Then, based on what he had observed, he arrived at the following conclusion:
[In this sequence describing the universe, apart from the first term, the unique number "1," the numbers that follow should consist of prime numbers such as "2, 3, 5, 7, 11, 13, 17, 19..."]
Smart children had probably already noticed that the Theory of Relativity, the Standard Model, Quantum Mechanics, and all sorts of other unfathomably profound theories were, in fact, this sort of thing.
They described the world beyond the fourth term, a world ordinary people could not see and could observe only with specialized equipment—
namely, what people usually called the "microscopic world."
Far luckier than that scholar beneath the apple tree, Einstein had been limited by his era and had seen only