The Allure of the Multiverse by Paul Halpern

Author:Paul Halpern [Halpern, Paul]
Language: eng
Format: epub
Publisher: Basic Books
Published: 2024-01-16T00:00:00+00:00

FLAT-OUT TRUTH

Numerology would seem to have no place in physics. Yet, on occasion, numerical patterns have led to important discoveries. For example, in the early 1960s, physicist Murray Gell-Mann looked at the properties of certain elementary particles, assigned them into arrays on that basis, and deduced the existence of other, hitherto unknown, particles—which were later discovered.

When Nobel laureate Paul Dirac, one of the great theoretical physics geniuses who successfully predicted antimatter (particle counterparts of opposite electric charge, such as positrons being the positively charged versions of electrons), announced the “Large Numbers Hypothesis” (LNH) in 1937, a segment of theorists took him very seriously. Based partly on earlier speculation by Arthur Eddington, Dirac’s proposal offers a way of understanding key features in the universe by connecting certain extremely large ratios—each of the order 1040 (1 followed by 40 zeroes)—of combinations of physical constants. He surmised that what we think of as constants could change over time, as long as those large ratios are preserved. For example, the ratio between the age of the universe and the time it takes for light to cross the classical radius of an electron is comparable to the ratio of the electric and gravitational attractions of an electron to a proton, each in the ballpark of 1040. Square that humongous number, and one obtains 1080, approximately the number of nucleons (protons and neutrons) in the observable universe. Dirac conjectured that to maintain those coincidences, gravitational strength must weaken over time.

By the late 1950s and early 1960s, Dirac’s idea had found an important exponent in Dicke, who was investigating alternatives to general relativity. Dicke’s embrace of the notion that G, the gravitational constant, should be replaced by a varying scalar field—that is, Brans-Dicke theory—was a direct consequence of his interest in Dirac’s LNH. Unlike Dirac, Dicke was an experimentalist, and sought to test his gravitational hypotheses by means of physical and astronomical observations. As Peebles recalled, Dicke once made a friendly bet with Wheeler about gravitational light-bending results, with the former hoping it would reveal cracks in general relativity’s predictions and the latter expecting that general relativity would be vindicated.7 Unfortunately for Dicke, general relativity has triumphed, so far, in every single test. There is no evidence for a changing gravitational constant.

Regardless of the validity of his hypothesis, Dicke contributed valuable insight to cosmology by emphasizing how the mere fact that we are here—and life has flourished on Earth in general—places strict bounds on the ways the universe could have developed. His analysis was an important forerunner of what became known as the Anthropic Principle. Take, for example, the LNH. Dicke believed such enormous figures reflected the stage of the universe we find ourselves in, one involving far-more-complex evolutionary processes than the rudimentary activity of elementary particles on the atomic scale. The many steps required for evolution sets a time scale for the emergence of humanity much greater than that of atomic transitions, leading to a very large number as their ratio. As he noted in a 1957 paper, “Man with all his complexity could not have evolved in a characteristic atomic time.

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