free download × PDF, DOC, TXT or eBook ↠ Manjit Kumar

uantum Einstein Bohr and the Great Debate About the Nature of Reality review ✓ 0 Uantum theory is weird As Niels Bohr said if you weren’t shocked by uantum theory you didn’t really understand it For most people uantum theory is synonymous with mysterious impenetrable science And in fact for many years it was euall. Whether the science in this book is light or heavy depends on who you are For me the science was heavy as my fascination with science has always been greater than my knowledge of it I am not a scientist That said I loved this book Did I understand all the theories experiments and discussions No But I understood enough to follow the narrative and get excited or saddened by events and to share the passion of these giants and marvel at their tenacity and their geniusYears ago When I started my studies in chemistry and physics my brother thoughtfully gave me a framed copy of the famous Solvay 1927 Conference group photo the one mentioned in the prologue as inspiration Inspire it did as I gradually learned who these participants were and what they contributed to the understanding of our world Theirs is such a grand story I did not need to get every scientific reference in order to love listening to it I think that is a measure of just how good this book is

uantum Einstein Bohr and the Great Debate About the Nature of Reality review ✓ 0 Y baffling for scientists themselves In this tour de force of science history Manjit Kumar gives a dramatic and superbly written account of this fundamental scientific revolution focusing on the central conflict between Einstein and Bohr. I thoroughly enjoyed Kumar s book He traces the scientific discoveries leading to uantum theory and the relationships of the scientists with a focus on the Einstein Bohr debate over the theory s meaning I found Kumar s explanations of complex theories accessible and helpful I remember in high school and college in the 1960 s always hearing about this strange uantum world that didn t uite exist unless someone looked at it Kumar really helps make sense of it My notes below summarize the science that paved the way for uantum theory the Einstein Bohr rivalry and the various takes on the Copenhagen interpretationKumar s history begins with Max Planck s discovery of the uantum and his eponymous constant Working to derive a formula to predict the spectral distribution of blackbody radiation in 1900 Planck found that only whole increments of energy worked At a time when the atom was not a widely accepted theory this confronted Planck s belief in the continuous nature of energy and matter He dodged the issue by saying that only the exchange of energy was uantized not energy itselfAlong came Einstein who accepted atoms as discrete matter and sources of discrete energy After reading Planck s paper Einstein challenged the prevailing wave theory of light proclaiming light is made up of uanta Einstein employed his uantum theory of electromagnetic radiation to explain the photoelectric effect in which light precipitates the release of electrons from metals This was in 1905 Even in 1922 when Einstein was awarded the Noble Prize for his euation explaining the photoelectric effect the underlying principle of light as uanta was still not widely accepted Newton had held that light was composed of particles but Thomas Young s famous two slit experiment in 1801 showed light to be a wave After overcoming the implied disrespect to Newton scientists finally accepted light as a wave and held onto that view as tenaciously as they had held onto the particle view before Also in Einstein s Annus Mirabilis he explained Brownian motion with atomic theory gaining the atom much wider acceptance And in his spare time that year he formulated the special theory of relativity and the famous EMC2In 1913 Niels Bohr conceptualized the uantum atom Recognizing that J J Thomson s plum pudding model of the atom was inherently unstable Bohr assigned electrons to special orbits in which they could not continuously emit radiation and lose energy Each orbit had a specific energy level When an electron moved from one orbit to another an exact amount of energy uantum was exchanged which resulted in uniue spectral patterns Amazingly there was no in between An electron left one orbit and appeared in another instantaneously The Franck Hertz experiment in 1914 confirmed that the energy released or absorbed was exactly the difference between the energy levels of the orbits In 1922 Bohr refined his atomic model with the concept of electron shells This allowed him to predict the chemical similarities of elements in the periodic tableEinstein was thrilled with Bohr s uantum atom as he felt it proved his theory of light uanta In 1916 finding time after his ground shattering theory of general relativity was announced in 1915 Einstein theorized that spontaneous emission occurred when an electron jumped to a lower energy orbit The rub was that in his theory electrons made these jumps at random His theory employed probabilities to determine the freuency of these jumps Einstein now as later was uncomfortable with chance in physics theories Einstein s light uantum later to be renamed the photon was proven in an 1923 experiment by American Arthur Compton who firing x rays at graphite recorded changed wavelengths in the reflected scattered x rays Only a particle would behave this way Further he found the recoiling electrons that the x rays had bounced off of Then a French prince Louis de Broglie setting the stage for uantum mechanics postulated that if a wave could have the values of a particle why not the reverse Ascribing wave characteristics to electrons explained perfectly the available orbits for electrons in an atom Only those orbits that could accommodate whole or half wave lengths were physically possible Sure enough subseuent experiments showed that electrons diffracted just like light Wave particle duality was now established for energy and matterIn 1925 Wolfgang Pauli building on a paper by Edmund Stoner developed the exclusion principle Stoner determined the number of possible energy states of electrons orbiting an atom But the three uantum numbers denoting angular momentum shape of orbit and orientation of orbit only allowed for half of the possible energy states Pauli developed a fourth uantum number which would later be explained as spin This uantum spin had two states up or down doubling the number of allowable electrons It also explained the heretofore mysterious splitting of spectral lines known as the Zeeman Effect The exclusion principle stated that no two electrons in an atom could have the same set of uantum numbers thus limiting the number of electronsWerner Heisenberg solved a remaining problem of the uantum atom model Even though it now explained the freuency of spectral lines it did not explain the different intensities Heisenberg decided to discard anything not observable even that electrons occupied orbits He needed the help of Max Born who collaborated with one his students an excellent mathematician named Pascual Jordan to get the math to support the physical theory This new uantum mechanics employed a strange form of matrix mathematics in which A times B does not eual B times A but it successfully calculated spectral line intensities In England Cambridge student P A M Dirac also developed a mathematical proof working from a draft of Heisenberg s paperIn 1926 Edwin Schr dinger developed a wave function for de Broglie s electrons which eliminated the incomprehensible electron jumps It also supported calculations that achieved the same predictive results as Heisenberg s matrix mechanics The rub was picturing what the wave represented Schr dinger claimed it was a cloud of charge that could smoothly and continuously move from one orbit to another He denied that electrons were particles at all while Heisenberg committed to particles opposed the wave theory putting the two at oddsHeisenberg trying to settle his dispute with Schr dinger developed the uncertainty principle This stated that uantum mechanics could not determine both the position and momentum of a particle specifically an electron Heisenberg working as Bohr s assistant toyed with the idea that the photon itself that measured the electron interfered with the observation Heisenberg refused to imply any behavior to an electron that could not be measured There was no assuming what happened to an electron between two measurements thus no path at all was held to have been traveled Basically Heisenberg was saying classical concepts of wave particle position momentum and trajectory had no meaning in the uantum world until observed Bohr believed that uncertainty was fundamental to the uantum nature of wave particle duality Bohr felt the electron was both a wave and a particle but that no experiment could measure both at the same time He called his principle complementarity Bohr held that observer and observed could not be separated The way the uantum world was observed determined what was seen Be it wave or particle both observations were true depending on the way it was observed Causality and regular patterns had no meaning The only prediction uantum mechanics could make was one of probability No experiment could ever return the deterministic clockwork cosmos of Newton to the uantum world There was no reality at the uantum level outside of observation This view became known as the Copenhagen interpretation Einstein while accepting that uantum mechanics was a correct and important theory did not accept this interpretation Einstein believed the uantum world was deterministic God doesn t play dice and most importantly real It was there even when nobody was looking The stage was set for a lifelong series of challenges to this interpretation by Einstein directed at Bohr the Copenhagen Interpretation s champion At the conferences in Solvay in 1927 and 1930 Einstein offered thought experiments to show uantum mechanics was an incomplete description of reality Bohr would parry and nothing would be resolvedAfter the Nazi s assumed power in Germany In 1933 Einstein moved to Princeton Bohr would be able to continue in Copenhagen until the Nazi s declared martial law in Denmark in 1943 Many Physicists in Germany were Jewish or had Jewish connections They were leaving and scattering around the world Despite the turmoil of the 1930 s and 40 s Einstein and Bohr carried on their uantum chess match Einstein in 1935 published a paper with help from Princeton assistants known as the EPR paper This thought experiment proposed measuring the momentum and position of one of a pair of entangled particles to determine the momentum and position of the other The point was to prove the existence of the other particle independent of direct observation of it The Copenhagen interpretation denied reality independent of observation Key to Einstein s argument was the concept of locality that nothing faster than the speed of light could affect the other particle Bohr conceded this but claimed the particles were entwined and thus one system that a measurement of one was a measurement of both Einstein reached out to the sympathetic Schr dinger who came up with his famous cat in a box thought experiment A tiny radioactive substance is placed in the box When it decays it will trigger a Geiger counter that will trigger the release of a vial of poison killing the cat Since the event is not observed does it happen In the Copenhagen interpretation of uantum mechanics only a probability wave of the event exists Schr dinger was trying to appeal to common sense in support of Einstein believing in reality that the cat was either actually dead or still alive But Copenhagen purists would still say that the cat was both dead and alive until the wave was collapsed by observation The debate would dominate the minds of Bohr and Einstein over the ensuing years Bohr last visited Einstein in Princeton in 1954 Einstein died the next year at 76 Bohr died in 1962 at 77 The night before his death Bohr had drawn on his blackboard Einstein s light box a thought experiment Einstein proposed at the 1930 Solvay conference in an attempt to prove uantum mechanics an incomplete theory Over 30 years later Bohr was still refining his argumentIn 1964 John Stewart Bell put forth a theorem to test whether any local hidden variables could be used to explain the behavior of the entangled particles in the EPR thought experiment Subseuent tests of the theorem supported non locality between entangled particles and paved the way for today s experiments with uantum level teleportation But even though what Einstein called spooky action at a distance was proven to exist his underlying belief that the uantum world also existed even when not measured was not disproven In 1957 Hugh Everett III found a neat way around the problem with his many worlds interpretation In this theory all uantum states actually exist simultaneously obviating the probability wave This resolved one objection to the Copenhagen Interpretation Who observed the big bang to collapse the probability wave God of course is one answer Another issue for uantum mechanics is determining the dividing line between the uantum world and the classical world where reality is the normDespite the overwhelming acceptance of the Copenhagen interpretation in the mid twentieth century today while uantum mechanics itself is universally accepted many physicists don t believe it is a complete theory The Copenhagen interpretation has lost its luster Nobel laurate Murray Gell Mann said Niels Bohr brain washed a whole generation of physicists into believing that the problem had been solved At a 1999 uantum mechanics conference at Cambridge University of 90 physicists polled only four accepted the Copenhagen interpretation thirty believed the modern version of the many worlds theory and most were undecided Famed British physicist Roger Penrose said I would myself strongly side with Einstein in his belief in a submicroscopic reality and with his conviction that present day uantum mechanics is fundamentally incomplete So maybe somewhere in the great beyond Einstein is finally winning his argument with Bohr

free download × PDF, DOC, TXT or eBook ↠ Manjit Kumar

uantum Einstein Bohr and the Great Debate About the Nature of Reality review ✓ 0 Over the nature of reality and the soul of science This revelatory book takes a close look at the golden age of physics the brilliant young minds at its core and how an idea ignited the greatest intellectual debate of the twentieth centur. It s written about the uantum mechanics history