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Einstein, quantum theory and the battle for reality

"I think I can surely say no one understands quantum mechanics." So the late, great physicist Richard Feynman quipped in the 1960s – and his words feel just as fresh today. The quantum mechanical explanation of how the universe works at atomic level interferes with intuition. Schrodinger's cat, the unfortunate moggie caught in a box with a radioactive atom whose unpredictable decay will release poisonous gas, is both dead and alive until we open the box to see. A particle has no definite position until we measure it, its exact location neither here nor there without a magic sensation of probabilities.

Hang on. Do you see, measure ̵

1; do our actions really make the difference? Isn't the poor cat either dead or alive before we open the box? Sure, the world behaves regardless of our perception of it? Albert Einstein believed so: he proclaimed realism, where the universe can be understood and described without regard to our interactions with it. His nemesis was the Danish physicist and glowing anti-realist Niels Bohr, who claimed that no such objective image is possible, just an overlying canvas that shows what we can observe and measure.

Anti-realism won the day. Quantum mechanics, promoted by Bohr, which transforms reality into an irrelevant, is the prevailing image of nature on the atomic and subatomic scale.

It should be overthrown, according to Lee Smolin, along with the "magic" thinking that accompanies it. Smolin, a leading player in the struggle to restore realism as the foundation of science, insists that it is now the right time to take up arms. "Science is under attack," he writes in Einstein's unfinished revolution "and thus the belief in a real world where facts are either true or false … when fundamental physics itself is cut off by an anti-realistic philosophy, we are in danger. "The danger he warns is the abandonment of the century-old realism project", which is nothing less than the continuous adjustment, bit by bit, as knowledge progresses, by the boundary between our knowledge of reality and the realm of fantasy. "

Smolin offers a masterful exhibition on the state of quantum physics, which smoothly mixes a history of the field with clear explanations, philosophical contexts and an accessible introduction to new ideas. His story of how two competing perspectives on quantum behavior were hardened in Bohr's counterintuitive orthodoxy, spelling binding.

Einstein fired the starting gun by embracing the idea that the light could show the properties of a particle occupying a particular location, and a wave that is more diffuse. In 1905, when he was only 26 years old and worked as a patent manager, he showed that the brilliant light on metal could release electrons. He had discovered what became known as the photoelectric effect, proving that the light came in small packages or "quanta" (now called photons). It would serve him a Nobel Prize in 1921.

Niels Bohr (left) and Albert Einstein © Science Photo Library

Niels Bohr discovered that Einstein's light theory can be used with advantage for atoms. A young Parisian aristocrat named Louis de Broglie then gave a critical insight: if light could be both a wave and a particle, the same bizarre duality could be true for electrons and other issues?

1920, Erwin Schrodinger, a matrimonial professor at the University of Zurich, heard of the Broglies thesis and took it, plus girlfriend, for a vacation in the mountains. Within a few days he had invented the relevant equations (when he traveled to Stockholm to accept his Nobel, rascal took both wife and girlfriend).

Bohr grasped that all these breakthroughs were gathered in a theory filled with puzzling probabilities and uncertainty, a shocking departure from the well-known, deterministic results of classical physics. But the new theory of quantum mechanics seemed to work, if not intuitively then mathematically. Bohr grabbed his moment, writes Smolin, "not only does the birth announce a new physique but a new philosophy. The moment for radical anti-realism had come and Bohr was ready for it."

Since Bohr's institute in Denmark was a hotbed for these ideas, became the philosophy known as Copenhagen's interpretation. When German theorist Werner Heisenberg arrived at the same formulation of quantum mechanics via another path, Bohr was further tested.

Although Einstein fell before Danish domination, realism never died. De Broglie later pioneered a unifying idea called pilot wave theory, where the particle is controlled by a "pilot" wave. It was rediscovered in the 1950s and still has its followers.

The last half century has given rise to other new ideas such as loop quantum gravity, where Smolin is a leading researcher. But he and his colleagues are not illusory about the monumental challenge ahead: the need to invent new physics, as Einstein and others did.

"So maybe it's all up to a brilliant student somewhere, impossible arrogant, as the young Einstein was, but dazzling enough to absorb the essentials of everything we've done before we set them aside and gently begin."

] If Einstein feels like the man of the moment, it is because 2019 marks the centenary of the most spectacular test of his forces: the British effort to confirm the theory of relativity by the total solar eclipse in 1919. This experiment and its heritage are subject to No Shadow of a Doubt by Daniel Kennefick of the University of Arkansas.

Einstein had calculated that starlight would bend as it passes a massive object – the sun says – because the object's gravity makes the space-time fabrics difficult. Eclipse on May 29, 1919 promised a rare chance to test their second worldly prediction. British scientists seized the opportunity and planned expeditions to two sites, Principe Island in the Gulf of Guinea and Sobral in Brazil.

When the moon passes in front of the sun during such eclipse, it blocks the sunlight from the sun disk and becomes day to night. The temporary blackout makes it possible to see stars around the sun's rails (as well as Sun's halo-like corona). By comparing the stars true places to their obvious places during the blackout, scientists were able to take advantage of whether the sun really deflected the starlight.

Kennefick for an exciting mix of ingredients together in a dense but rewarding reading: Einstein's chutzpah; Joy, happiness and sense of adventure of eclipse-hunting; whether one is planning such a demanding experiment during the First World War and performing it in its chaotic aftermath. An earlier attempt to confirm relativity ended badly: German scientists looking at the 1914 eclipse in Crimea were arrested as Russian spies.

The war inevitably also cast a shadow over the 1919 eclipse. The planning fell to two brilliant astronomers, both pacifist "oddballs": Sir Arthur Eddington, head of the Cambridge Observatory, and Sir Frank Dyson, then Astronomer Royal and based at Greenwich. Eddington, a Quaker refusenik, was in prison until his university made a considerable appeal to the commission card and claimed that after the death of the observer, first and second assistants, no one in Cambridge killed how to get an eclipse.

A shortage of civil vessels also causes difficulties in sending the necessary equipment. But the expeditions were somehow sailing, the sun shone the most and the necessary observations were secured.

And what observations they were! In November 1919, six months after the eclipse, Eddington and Dyson revealed that they had confirmed Einstein's prediction. It was a global feeling. "Lights All Askew in the Heavens" ran the headline of the New York Times.

The affirmation also influences the culture of science: Einstein's readiness to submit his ideas to experimental investigation persuaded philosopher Karl Popper to develop "forgery" as the litmus test of scientific truth.

Kennefick dissects the skepticism that has then accommodated this historical experiment. After the war, he notes, most German scientists exposed ostracism. Eddington and Dyson plotted to prove relativity in a post-war bid to reunite scientists and the wider world? Did they show bias by rejecting certain data? The fact that both Eddington and Dyson were adept at publicity also seems to have sullied their reputation – unauthorized, in Kennefick's view. "It is wrong to believe that the truth needs no advocate," he writes. The 1919 experiment, he believes, achieved his only goal: to prove Einstein either right or wrong.

Not that the great man needed such confirmation. When asked what he would have done, the result had been less obligatory, Einstein explained: "Then I have to forgive my dear God. The theory is correct."

Now, reserve our compassion for Mileva Maric, or Einstein's wife as a new biography selectively describes her (he was married twice). The cerebral Serbian, among the earliest female science students in Europe, met Albert 1896 at Zurich Polytechnic, where both studied mathematics and physics.

A fellow student described Mileva as "a very good girl, smart and serious, she is small, fragile, dark, ugly … limps a bit, but has very nice manners". Albert, several years younger, was enchanted; He called her Dollie and she called him Johnnie. Their families did not approve. Mileva became pregnant. A daughter, Lieserl, was born out of wedlock, but surprisingly her fate is still unknown. Survivor letters hint at Lieserl either to die from scarce fever or give up for adoption.

However, this is not the question that this book, by retired physics teacher Allen Esterson and science historian David C Cassidy, answers. Instead, Mileva, as former cinemas speculated, was an unredited contributor to Einstein's research?

School and university reports suggest that she was bright but not natural. When the couple responded during periods from each other (including the pregnancy), he happily wrote his ideas but her answers did not work on them. A careful analysis of letters, interviews, gossip, used reports, translations and renegotiations leaves the authors convinced of the Mileva myth.

What appears instead is a portrait of a skilled but frustrated young woman who tragically does not achieve her full potential as a scientist, "nor did she realize her hopes and dreams in marriage and in life". By 1919, this year's eclipse, Einstein had depicted Mileva to marry her first cousin Elsa, herself a divorce with children. Letters arose recently because Einstein had design at one of Elsa's daughters.

This biography of Einstein's forgotten first wife instead gives a haunting accusation of Albert as a distant and ultimately disloyal companion: a quantum man who was neither here nor there; a visionary who saw the star beam in the universe but not the darkness closer to home.

Einstein's unfinished revolution: The search for what is beyond the quantity by Lee Smolin, Allen Lane, RRP £ 25, 322 pages

No shadow of doubt: 1919 Eclipse Confirming Einstein's Theory of Relativity by Daniel Kennefick, Princeton, RRP $ 29.95 / £ 24, 416 Pages

Einstein's Wife: The Real Story of Mileva Einstein-Marić by Allen Esterson and David C Cassidy, MIT, RRP $ 29.95 / £ 24,336 pages

] Anjana Ahuja is a science commentator

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