Physicists use mathematical entities called wave functions to represent quantum states. A wave function can be thought of as a list of all the possible configurations of a superposed quantum system, along with numbers that give the probability of each configuration’s being the one, seemingly selected at random, that we will detect if we measure the system. The wave function treats each element of the superposition as equally real, if not necessarily equally probable from our point of view.
The Schrödinger equation delineates how a quantum system’s wave function will change through time, an evolution that it predicts will be smooth and deterministic (that is, with no randomness). But that elegant mathematics seems to contradict what happens when humans observe a quantum system, such as an electron, with a scientific instrument (which itself may be regarded as a quantum-mechanical system). For at the moment of measurement, the wave function describing the superposition of alternatives appears to collapse into one member of the superposition, thereby interrupting the smooth evolution of the wave function and introducing discontinuity. A single measurement outcome emerges, banishing all the other possibilities from classically described reality. Which alternative is produced at the moment of measurement appears to be arbitrary; its selection does not evolve logically from the information- packed wave function of the electron before measurement. Nor does the mathematics of collapse emerge from the seamless flow of the Schrödinger equation. In fact, collapse has to be added as a postulate, as an additional process that seems to violate the equation.
Many of the founders of quantum mechanics, notably Bohr, Werner Heisenberg and John von Neumann, agreed on an interpretation of quantum mechanics—known as the Copenhagen interpretation— to deal with the measurement problem. This model of reality postulates that the mechanics of the quantum world reduce to, and only find meaning in terms of, classically observable phenomena—not the reverse.
This approach privileges the external observer, placing that observer in a classical realm that is distinct from the quantum realm of the object observed. Though unable to explain the nature of the boundary between the quantum and classical realms, the Copenhagenists nonetheless used quantum mechanics with great technical success. Entire generations of physicists were taught that the equations of quantum mechanics work only in one part of reality, the microscopic, while ceasing to be relevant in another, the macroscopic. It is all that most physicists ever need.
Universal Wave Function
In stark contrast, Everett addressed the measurement problem by merging the microscopic and macroscopic worlds. He made the observer an integral part of the system observed, introducing a universal wave function that links observers and objects as parts of a single quantum system. He described the macroscopic world quantum mechanically and thought of large objects as existing in quantum superpositions as well. Breaking with Bohr and Heisenberg, he dispensed with the need for the discontinuity of a wave-function collapse.
Everett’s radical new idea was to ask, What if the continuous evolution of a wave function is not interrupted by acts of measurement? What if the Schrödinger equation always applies and applies to everything—objects and observers alike? What if no elements of superpositions are ever banished from reality? What would such a world appear like to us?
Everett saw that under those assumptions, the wave function of an observer would, in effect, bifurcate at each interaction of the observer with a superposed object. The universal wave function would contain branches for every alternative making up the object’s superposition. Each branch has its own copy of the observer, a copy that perceived one of those alternatives as the outcome. According to a fundamental mathematical property of the Schrödinger equation, once formed, the branches do not influence one another. Thus, each branch embarks on a different future, independently of the others.
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14 Comments
Add Commentimaginative scientists- using imaginary numbers- creating imaginary universes-which cannot be fully imagined.
Reply | Report Abuse | Link to thisIMAGINE THAT ! ! TAHT ENIGMA!
If time were thought to actually oscillate, like a point on the rim of a rolling wheel that appears to go retrograde as it moves forward, much of the paradox of quantum multi-states would disappear.
Reply | Report Abuse | Link to thisFurthermore, the retrograde overlap would create the appearance that time had quantum properties (both partical and wave, simultaneously) as it marches forward to eternity.
photons traveling to a target could react in similarities as a basball being thrown (curved) when isosolation occures. Thus acting as a wave.
Reply | Report Abuse | Link to thiswow. i'm a huge Eels fan... that was a big suprise at the end of the article. Souljacker is a great album, i highly recommend it.
Reply | Report Abuse | Link to thisDifferent worlds seem far fetched. but when we dial in a radio station in amongst static (I think of atoms as static) we are opened up to different worlds, so to speak. We electronically tap into a energy source from which we know how is produced. But perhaps we can tap (physiologically) into an energy source from another plain from which Everret theorizes.
Reply | Report Abuse | Link to thisWow. I just finished reading the article. It's mind blowing. I've been a science fiction fan for over 40 years. Robert Heinlein's premise in "The Number of the Beast" that number of the beast is not 666, but 6 to th 6 th power raised to the sixth power is the possible number of universes, and that every time an author creates a new "universe" it becomes reality somewhere fits right in with Everett's theory.
Reply | Report Abuse | Link to thisIt also illustrates the importance of being able to think in magnitudes of scale in both size and time. When I took my geography capstone course in 1993 or 1994, the geography chairman said that the last big paradigm shift in the discipline of geography was the realization of the importance of scale. This is true across many different disciplines. I've been obsessed with analyzing the flooding of Greater New Orleans from the Katrina storm surges, and the ACOE STILL doesn't understand that by treating the drainage and flood prevention systems as links in a chain that they are ignoring an awful lot, because they don't seem to have the ability to analyze the system from the microscopic level to the macroscopic level at different scales, from a single floodgate or canal, to the entire drainage system of the east bank, then all of south eastern LA to the entire state to the continent. Then there's the system of faults between the North American plate and Caribbean plate. When it it lets go in the right place, GNO is going to be inundated by a tsunami. Is that real enough possibility for those living in GNO to seriously consider moving their personal property to higher ground permanently? It is for me in this reality.
Not many years ago the world of science refused to believe measurements proving the world was round relying strictly on what felt "right" and what our physical perceptions led us to believe. Everett refused to be deceived by his senses and instead relied on and developed a theory true to mathematics and measurements. In the not so distant future his theory will prove him to be of the magnitude of Galileo. Godspeed Mr. Everett!
Reply | Report Abuse | Link to thisI wonder if Hugh's son has some old science-fiction mags from before his dad started to work on this that had some of the H.Beam Piper ParaTime stories in them. If he does, then Piper may be due a footnote or a byline in the history of this concept. Piper started publishing ParaTime stories in 1947 thru 1964. Check his "Lord Kalvan Of Otherwhen". It has multi divergent world lines based on the transposition of one individual into a world line where the choices he made once he arrived cause the generation of MANY NEW world lines. Here the quanta is choice in/of a human mind and how those humans around him react to bifurcate reality.
Reply | Report Abuse | Link to thisI hope that Hugh's daughter found him. ... "there are more things..."
I was inspired to review this material after reading "A Quantum Threat to Special Relativity" (Scientific American, March 2009). Specifically, I was impressed by the following, a description of Bohr's response to concerns about quantum mechanical entanglement: "Bohr's was a curiously philosophical response to an explicitly scientific concern. More curious still was the enshrinement of Bohr's response as the official gospel of theoretical physics. " I was unaware prior to reading this, and very glad to learn that "From the early 1980's onward, the grip of Bohr's conviction-that there could be no old-fashioned, philosophically realistic account of the subatomic world-was everywhere palpably beginning to weaken." As a former biomedical researcher, I despise bad science and the personality cults which allow it to prosper. Shame on Bohr, who led mainstream physics to turn "away from its old aspirations to uncover what the world is really like..." in favor of " 'a radical revision of our attitude as regards physical reality' " (Bohr's words). The worst thing about bad science is that it has the effect of suppressing the truth. My instincts always told me that collapsing wave functions were a bunch of hooey, and they also tell me that the truth lies in multiple universes. I suspect that Bohr's reputation will suffer, among the knowledgeable, in the same way as Freud's, and Everett's will rise after his death as did Gregor Mendel's.
Reply | Report Abuse | Link to thisLater on this year I will introduce a concept based on the principles of the fractal nature of our universe that will be a possible solution to all the theories that have left so many questions in this field. Even though I am but a retired janitor I have come up with a fractal way that I believe will give some way to answer how our world is constructed.
Reply | Report Abuse | Link to thisAlso supressed and/or ignored were the 'pilot wave' concepts of David Bohm and Cramer's later but related 'Transactional Interpretation' of Quantum Theory...
Reply | Report Abuse | Link to thisCommenters 'westnova' and 'oklatonola' both raise important points on fractals and scale which both bear on the mind-twisting 'decidability' (sic) problem of Q-mechanics.
I think it's important to keep reminding ourselves how very subjective and limited our viewpoints are... in terms of time, scale and bandwidth!
Everett's theory does not seem that much far fetched to me. If time travel is possible, teleportation in being worked on and invisibility is a reality, then why not this?
Reply | Report Abuse | Link to thisHow exciting it must be that everytime a measurement is made, the universe splits into new universes consisting of all possibilities allowed by that measurement. Billions of measurements each day. We must allow for levels of infinity beyond those contemplated by set theorists. I love science fiction too, but unfortunately Everett's mechanism of bifurcation is as unsatisfying as Bohr's collapes of the wavefunction, i.e. there is no mechanism posited (read Everett's original paper), rather it just happens. Bell's Inequality is still violated with no plausible explanation of why. Just that it is.
Reply | Report Abuse | Link to thisMany worlds is a bizarre hypothesis. The idea that a quantum event can spawn countless universes is an exercise in vanity. The truth is that limitations of the human brain create that perception. Having said that, it is likely that there are many universes and the brain switches between them seamlessly.
Reply | Report Abuse | Link to thisD J Wray
http://www.atotalawareness.com