In what is called the double-slit experiment, “you have a light source, along with a photographic plate that records the light that’s emitted. Between them, you place a screen that blocks the light. If you cut a slit in the screen for the light to pass through, then a fuzzy image is created on the photographic plate that corresponds to the location of the slit.
“What happens if you cut a second slit in the screen? You might think you would get two fuzzy images, matching the two slits, but you don’t. Instead, the light appears to pass through the slits as waves, producing an interference pattern on the photographic plate, of alternating light and dark bands. Light sometimes acts as if it’s made up of particles, and other times it acts like waves. But here’s the thing about the double-slit experiment: when you turn down the light source so low that the light goes through the screen one photon at a time, guess what happens? Somehow, you still get the interference pattern. As theoretical physicist Paul Dirac said, ‘Each photon then interferes only with itself.’ It’s as if each photon hasn’t made up its mind about which slit to choose and goes through both of them simultaneously.
“In case you think these results are simply due to the strangeness of light, its particle-wave duality, you should know that the double-slit experiment has now been done with electrons as well. In fact, similar experiments have been done with neutrons, atoms, and even larger molecules. Not just light but actual matter also acts like waves, seeming to go in two places at once and interfering with itself. The famed physicist Richard Feynman said the double-slit experiment was ‘impossible, absolutely impossible, to explain in any classical way’ and it ‘has in it the heart of quantum mechanics.’
“Most of us learned in science class that atoms, the building blocks of the universe, consist of electrons circling a nucleus like small billiard balls. Quantum physicists tell us instead that electrons are better seen as smears of probability, with their locations being potentials rather than definite places. As strange as it may seem, it is only when an electron is measured that its location goes from a smear to a specific spot.
“In the double-slit experiment, there is one thing that can force the photons to make up their minds and go through one slit or the other. If you set up sensors to observe them as they travel, each photon is seen going through just one of the slits. The interference pattern on the photographic plate disappears, and you get two fuzzy images corresponding to the two slits instead. The observation leads to one path, one definite outcome, rather than the two potential outcomes that existed before.
“Similarly, take a small particle that can travel down one of the two paths, with a fifty-fifty chance of going down each one. According to quantum theory, until someone looks to see which path it goes down, with a measuring device for instance, all that can be said about the particle is that it has the two probabilities. Common sense says it goes down a path but we just don’t know which one until someone checks. Common sense, however, can be misleading at the quantum level. Until the particle is observed, it does not actually go down either path. It simply exists as a fifty-fifty probability wave for going down each path.
“To say that light and matter only exist as probability waves until they are observed raises the question of what their existence in such a state would mean. As Werner Heisenberg, one of the founders of quantum physics, noted: ‘The atoms or the elementary particles themselves are not as real [as any phenomena in daily life]; they form a world of potentialities or possibilities rather than one of things or facts.’ With a measurement, one outcome snaps into place. ‘The transition from the possible to the actual takes place during the act of observation,’ to quote Heisenberg again. The measurement somehow causes one of the two possibilities—or in other situations one of many possibilities—to become the reality that is seen. Measuring something thus creates a reality that did not exist before.
“Imagine that you do an experiment in which a photon can take one of two paths, and a measuring device can be set up on one of the paths to determine if the photon goes down it. The device failing to detect it on that path would mean that the photon must have taken the other one.” Quantum physicists examining this situation “found that observing the absence of a photon on the first path collapses the wave function just as much as observing the presence of it would. Since nothing is actually measured and only an absence is observed, this indicates that the observation—not the measurement itself—is the critical process in wave function collapse.’”
Moreover, Tucker writes: “it’s not the observing per se that produces a result, it is the knowing produced by the observing that does. By seeing that a particle doesn’t go down one path, an observer can deduce that it must have gone down the other one. Since no other result is possible, the observer ‘knows’ which path the particle took, thereby collapsing the wave function and producing the result.” As John Hopkins physicist Richard Conn Henry wrote in the journal Nature, ‘The wave function is collapsed simply by your human mind seeing nothing.’ This led him to conclude, ‘The Universe is entirely mental.’
Another physicist, Helmut Schmidt, conducted experiments “to see if conscious effort could produce nonrandom results even if the effort occurred after the events had already been recorded. He got positive results in the five studies he did, with odds against chance of 8,000 to 1. He recorded random events such as red and green light flashes, and the series of flashes was then stored on a floppy disk. Days or months later, the sequence was shown on a computer while a test subject tried to mentally cause one of the colors to flash more. As long as no one inspected the recordings beforehand, the mental efforts of the test subjects could cause the results to be nonrandom, with more of one color appearing that would be expected by chance. The test subjects’ success means that the collapse of the wave function did not occur when the recording device initially measured the flashes of light; the collapse only happened when the recordings were later observed.
Jim B. Tucker, Return to Life: Extraordinary Cases of Children Who Remember Past Lives (St. Martin’s Press, 2013).
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