Some things never change. Physicists call them the constants of nature. Such quantities as the velocity of light, c, Newton's constant of gravitation, G, and the mass of the electron, me, are assumed to be the same at all places and times in the universe. They form the scaffolding around which the theories of physics are erected, and they define the fabric of our universe. Physics has progressed by making ever more accurate measurements of their values.I like the happenstance theory. Suppose a fledgling baseball fan knows only one fact about major league baseball, namely, the lifetime batting average of Ty Cobb, which is .367. That average is not a "law of nature" but, rather, the byproduct of Cobb's 11,429 official at-bats in regular-season play (which excludes the times he was walked or hit by a pitch). Cobb happened to collect 4,191 base hits in those 11,429 official at-bats; thus his lifetime average of .367. If Cobb had retired a few years earlier, his lifetime batting average would have been higher; a few years later, it would have been lower. Then there are the thousands of other "unobserved" persons who played major league baseball and compiled batting averages lower than Ty Cobb's.
And yet, remarkably, no one has ever successfully predicted or explained any of the constants. Physicists have no idea why they take the special numerical values that they do. In SI units, c is 299,792,458; G is 6.673 X 10-11; and me is 9.10938188 X 10-31--numbers that follow no discernible pattern. The only thread running through the values is that if many of them were even slightly different, complex atomic structures such as living beings would not be possible. The desire to explain the constants has been one of the driving forces behind efforts to develop a complete unified description of nature, or "theory of everything." Physicists have hoped that such a theory would show that each of the constants of nature could have only one logically possible value. It would reveal an underlying order to the seeming arbitrariness of nature.In recent years, however, the status of the constants has grown more muddled, not less. Researchers have found that the best candidate for a theory of everything, the variant of string theory called M-theory, is self-consistent only if the universe has more than four dimensions of space and time--as many as seven more. One implication is that the constants we observe may not, in fact, be the truly fundamental ones. Those live in the full higher-dimensional space, and we see only their three-dimensional "shadows."
Meanwhile physicists have also come to appreciate that the values of many of the constants may be the result of mere happenstance, acquired during random events and elementary particle processes early in the history of the universe.
Scientific knowledge, in some respects, is as superficial as the knowledge of the fledgling baseball fan. The "constants" of nature have been found to take certain values. But until scientists understand "why" the constants take the values that they do -- just as we know "why" Ty Cobb batted .367 over his career -- scientists will have only superficial and partial knowledge of our universe.
Isaac Newton (1642-1727) said near the end of his life,
I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, while the great ocean of truth lay all un-discovered before me.Almost 300 hundred years have passed since Newton wrote those words. Yet, any living scientist who is worthy of being called a scientist would take them for his own.