There exist a bunch of fundamental physical constants that define (or at least describe) important characteristics of our universe. Traditionally these are dimensionless numbers, which means they have no units like kph or grams, although they often describe relationships between dimensioned constants.
Alpha (also know as the fine structure constant), for example, describes the strength of the attraction between the electron and proton. It combines the speed of light, the elementary charge, Planck’s constant and something called the ‘permittivity of free space’ to arrive at its value. The value itself is approximately 1/137.
I think these constants are extremely sexy.
If these constants were different, the universe could be a very different place. Your trousers might fall apart or maybe the universe would have blinked out of existence shortly after (or even before) the big bang.
Scientists have often wondered if these constants are, in fact, constant. Maybe they were different in the past. It has however been difficult to measure what these constants were in the distant past.
The article I link to on ArsTechnica describes a new approach to measuring what a couple of these constants were in the past.