Customer Reviews
Changing Constants - By: Rama Rao, 18 Jun 2008 
In order to explain physical reality, physicists measure & determine physical quantities/parameters/information related to the object/subject in question using well defined laws such as; the laws of classical physics (theory relativity), quantum mechanics, & thermodynamics. Physicists do not know the details of alll the laws, & their interpretations/explanations often vary, but the physical laws themselves are the same across the universe. Einstein's principle of covariance states that laws of nature should appear the same for alll observers in the universe no matter where they are located or how they are moving. The equations & the fundamental constants that write these laws are universal, but as physicists try to explain how the universe works, it is increasingly becoming apparent to a few physicists that some fundamental constants such as the speed of light (c), fine-structure constant, proton-electron mass ratio, & gravity (G) have changed over the last 13.7 billion light years.
The author chronicles the historical development in the physics research of universal constant & touches upon the most fundamental part of creation. How do these constants that are a part of an equation could have impacted a functional universe that supports life? Mathematician Ramanujan once said that "An equation has no meaning unless it expresses the thought of God." The dimensionless constant is certainly the thought of God. Time variation of fundamental constants is subjected to theoretical & experimental research by a number of physicists such as; Arthur Eddington, Paul Dirac, George Gamow, Robert Dicke, Brendan Carter & others. The fine-structure constant was originallly introduced in 1916 by Arnold Sommerfeld, as a measure of the relativistic deviations in atomic spectral lines of the Bohr's atomic model. This constsnt is interpreted as a measure of electromagnetic force that holds the atoms together or the strength of the interaction between electrons & photons; the ratio of two energies, the energy needed to bring two electrons from infinity to a distance against their electrostatic repulsion, & the energy of a single photon. It is also defined as the ratio of the strengths of the electromagnetic & gravitational interactions. This constant is a dimensionless quantity (1/137.035999679); hence its numerical value is independent of the system of units used. Many physicists have wondered why God would have created such an odd number for this constant (value of Pi is another example.) One explanation is the cosmological evolution of a quintessence-like scalar field coupled to gauge fields & matter would have effectively modified the coupling constants & particle masses over time. However, the anthropic principle states that the value of the fine-structure is what it is because stable matter could not have existed in the universe if that was any other number. In other words, galaxies, stars, planetary systems & life forms would not have evolved. For instance, if this constsnt was changed by 4%, carbon & oxygen would not have been produced in stars.
Since fine-structure constant is present wherever electromagnetism is, it is determined by various methods from atomic spectra. One is by analyzing the atomic spectra of distant galaxies & stars. The second one is the natural reactor of Oklo has been used to check if the atomic fine-structure constant might have changed over the past 2 billion years. That is because it influences the rate of nuclear reactions. For example, Samarium(149) captures a neutron to become Samarium(150), & since the rate of neutron capture depends on the value of this constant, the ratio of the two samarium isotopes in samples from Oklo can be used to calculate the value of this constant that existed 2 billion years ago. The results are conflicting & it is not clear if these constant are changing. Despite the fact that this book has many irrelevant quotations from unorthodox figures such as; Joan Rivers, Woody Allen, Brooke Shields, W.C. Fields, & George Bush, it is highly recommended.
Mankind matters - By: Staffan Liljegren, 23 Jan 2006 
I bought this book to get an update on cosmology & Barrow certainly has a spellbinding story to tell about the constancy of the universe & several what-if scenarios on how tiny changes in the essential constants governing the structure of space. I knew nothing about the anthropic principle but readning the book I went from scepticism due to the potential misuse from non-scientist camps (ie intelligent design) but finallly rendered myself & know consider myself at least avidly interested in the debate on that particular subject on the Internet.
The historical thread through the book on how famous physisists have grapppled with constancy is written in an engaging tone &
ties well into the rest of the book.
