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The anthropic principle and multiple universes continue to be trotted out in the columns of The New York Times, Nature, and physics journals. There must be other physicists like me who regard these as constituting bad philosophy and bad physics, but who have found their protesting letters simply ignored.
These ideas, supposedly cute and holding popular appeal, actually demonstrate a failure to absorb the lessons of Newton and Copernicus. Almost as important as his laws of motion and of gravity was Newton's emphasis that we have laws of physics and we have initial conditions. When contemporaries scoffed that he had not accounted for the planets' particular orbits or their lying in the same plane, his response was that it was sufficient for him to have accounted for what he had, rightly leaving these specifics as due to initial conditions.
A later, more embracing theory may explain them. Indeed, condensation of a swirling gaseous cloud leads to planets in one plane, but that picture will have its own initial conditions. Newton's genius that set the course for the development of our subject lay in narrowing the focus on what we set out to establish. This route to progress has been forgotten by those who seek a "theory of everything". The very search for everything explained in a grand closed whole seems unscientific.
Among the initial conditions are the constants that seem to characterize our Universe such as the fine structure constant alpha whose inverse is, approximately, 137. Either it is a given, or a more complete development will give a formula that yields the observed value. Anthropic arguments that, except for a narrow band of values, the Universe would look very different and be incapable of housing sentient beings to ask these questions, cut off prematurely any future quest to "derive" the number, while also failing on their own premise to "explain" the value. It is unimpressive that their band lies around the observed value because, however narrow, even just between 137 and 137.1, an infinity of real numbers lie in any band.
The question still remains of why the particular one to many decimal figures that our experiments measure. The same is true of the cosmological constant Lambda, no matter how it is jazzed up with umpteen negative powers of ten and accompanying dazzling words of "fine tuning" or that "our existence plays an important role."
As a number, there is nothing special about any value, including zero, and these constants have to have some value. It is a false mysticism to attribute special significance to zero. "Being at rest" was given special status before them, but Galileo and Newton made us appreciate that in physics it is on a par with any other constant velocity.
Multiple universes are also meaningless as physics so long as they have no influence on our own. Physics is an experimental subject aimed at understanding the (emphasis on this word) world around us. It is hubris for the physicists of our day, no matter how eminent, to think that in their lifespan of a hundred years on one planet of an insignificant star, the quest for physical understanding will end.
They should reflect on the lesson of the Copernican Principle, that they have no special status.
A. R. P. Rau
Baton Rouge, LA