Einstein's Lost Key

Einstein's Lost Key

Author	Alexander Unzicker
Published	2015
Publisher	CreateSpace Independent Publishing Platform
Pages	236
ISBN	978-1519473431

Einstein's Lost Key: How We Overlooked the Best Idea of the 20th Century is a 2015 popular-science book by the German physicist and science writer Alexander Unzicker. Published on 28 November 2015 by CreateSpace Independent Publishing Platform in a 236-page paperback edition (ISBN 978-1519473431; ISBN-10 1519473435), it argues that Albert Einstein's early, and later abandoned, treatment of gravitation as a spatially variable speed of light was the more physical of the two routes Einstein took toward a theory of gravity, and that its premature abandonment cost twentieth-century physics its best idea. An updated and revised edition appeared in 2022, and the book is also available as a Kindle e-book and as an Audible audiobook.

The book appeared in the centenary year of the completion of the general theory of relativity and is the popular counterpart to Unzicker's own technical work on Mach's principle and variable-speed-of-light gravitation. It followed his two earlier critiques of contemporary theoretical physics, Bankrupting Physics (with Sheilla Jones) and The Higgs Fake, both of which drew sharp reactions from the physics community.

Synopsis

One hundred years after the completion of the general theory of relativity, conferences, meetings and celebrations took place all around the world — yet, Unzicker argues, a decisive consideration on the subject by Einstein himself had completely fallen into oblivion. Already in 1911, Unzicker writes, Einstein held the key to an even greater discovery in his hands: a theory concerning the variable speed of light that would have explained the origin of gravity by referring it to the distant masses in the universe.

Einstein's 1911 idea

In his 1911 work on the influence of gravitation on the propagation of light, Einstein treated gravity not as a curvature of spacetime but as a position-dependence of the speed of light c: light slows in a gravitational potential, and rays are consequently bent, exactly as a medium of varying refractive index would bend them. Within a few years Einstein had replaced this picture with the metric, geometrical formalism of general relativity, and the earlier line of thought was set aside. Unzicker's contention is that the two descriptions are far closer than the textbook history suggests — that spacetime curvature can be mimicked by a speed of light c(r) that depends on the distribution of masses — and that the variable-c version retains a physical transparency the geometrical version loses.

The Machian consequence

The heart of the book is what Unzicker takes to be the idea's Machian payoff. If the local speed of light is fixed by the surrounding matter, then gravitation is not a local, intrinsic property of space but an effect of all the masses in the universe, in the spirit of Ernst Mach's principle. On this reading the gravitational constant would not be a fundamental constant of nature at all but a derived, cosmologically determined quantity. Unzicker argues that Einstein's 1911 formula for the variable speed of light would have been confirmed once the true size of the universe became known — but that the necessary astronomical scale was only established in the 1930s, by which time the idea had been abandoned. Einstein's insight, in his phrase, came about twenty years too early.

Unzicker develops this argument technically in A Machian Version of Einstein's Variable Speed of Light Theory (arXiv:1503.06763, with Jan Preuss), which uses Green's functions to cast Einstein's 1911 idea in closed analytic form and derives a relation between curvature and the local speed of light, and earlier in Mach's Principle and a Variable Speed of Light (arXiv:gr-qc/0511038). He places his own work in a lineage running from Mach through Dennis Sciama's 1953 inertial-induction hypothesis and Robert Dicke's 1957 flat-space, variable-refractive-index representation of gravitation.

Consequences for cosmology

Unzicker maintains that the consequences of taking the 1911 idea seriously would be revolutionary for modern cosmology: if the speed of light is not a universal constant but varies with the mass distribution, then the interpretation of redshift, and with it the picture of an expanding universe and the Big Bang, would need to be revised. This is the point at which the book departs most sharply from the standard cosmological model, and Unzicker presents it as an open research question rather than a settled result.

Schrödinger, Dirac and the lost thread

A recurring theme is that Einstein was not alone. Unzicker notes that the Nobel laureates Erwin Schrödinger and Paul Dirac had both worked on closely related ideas — Dirac's large-number hypothesis, in particular, raising the possibility that the "constants" of nature evolve with the age of the universe — and that this whole line of enquiry was dropped less because it was refuted than through a series of historical accidents and shifting fashions. He treats the same abandoned programme historically in A Look at the Abandoned Contributions to Cosmology of Dirac, Sciama and Dicke (arXiv:0708.3518).

The book is at once a description of relativity written to be comprehensible to lay readers, a vividly told piece of history of science, and, in Unzicker's own framing, a serious though controversial contribution to current research. Alongside the physics runs the polemical thread familiar from his earlier books: a criticism of the modern preference for elaborate mathematical modelling over intuitive, visualisable physics, and a call for physicists to return to the primary literature and to the unanswered questions of the early twentieth century.

Reception

The book was reviewed by Kirkus Reviews on 7 February 2016. The reviewer summarised Unzicker's thesis as the examination of "a concept that Einstein originally incorporated into his work on relativity, but later abandoned: a variable speed of light," and granted that "the author's ideas are engaging and he presents them well," while judging that he "doesn't make a compelling argument for the correctness of a variable light-speed." The review objected chiefly to the book's tone, holding that Unzicker's "insistence on attacking the 'groupthink' of the scientific community" and his criticism of mathematical models over more intuitive practices "becomes overly insistent and detracts from the inherent appeal of the underlying concepts," so that the book "turns into a screed against the scientific establishment." Its verdict called the work "a passionate but disconnected treatise whose adversarial tone makes for an ultimately unpleasant reading experience."

The original page on this wiki carried the Kirkus quotation in the abbreviated form:

KIRKUS REVIEWS: ...the author's ideas are engaging and he presents them well. [...] turns into a screed against the scientific establishment.

As with Bankrupting Physics and The Higgs Fake, the reception of Einstein's Lost Key has divided along familiar lines: reviewers sympathetic to Unzicker's project value the recovery of a genuinely Einsteinian idea that the textbooks pass over, while critics within the mainstream community treat the argument as a polemic against institutional physics rather than a technical case. Unzicker has continued to argue the book's thesis publicly, notably through his YouTube channel "Unzicker's Real Physics."

Links to Purchase Book

• Einstein's Lost Key

External links

• Kirkus Reviews review of Einstein's Lost Key (7 February 2016)
• Alexander Unzicker and Jan Preuss, "A Machian Version of Einstein's Variable Speed of Light Theory" (arXiv:1503.06763)
• Alexander Unzicker, "Mach's Principle and a Variable Speed of Light" (arXiv:gr-qc/0511038)