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Quantum Experiment Confirms Causality Is Fuzzy (physicsworld.com)
"An experiment has confirmed that quantum mechanics allows events to occur with no definite causal order," reports an article shared by long-time Slashdot readers UpnAtom and jd. Researchers at the University of Queensland in Australia believe this could link Einstein's general theory of relativity to quantum mechanics, according to Physics World:
In classical physics -- and everyday life -- there is a strict causal relationship between consecutive events. If a second event (B) happens after a first event (A), for example, then B cannot affect the outcome of A. This relationship, however, breaks down in quantum mechanics because the temporal spread of a particles's wave function can be greater than the separation in time between A and B. This means that the causal order of A and B cannot be always be distinguished by a quantum particle such as a photon.
In their experiment, Romero, Costa and colleagues created a "quantum switch", in which photons can take two paths. One path involves being subjected to operation A before operation B, while in the other path B occurs before A. The order in which the operations are performed is determined by the initial polarization of the photon as it enters the switch.... The team did the experiment using several different types of operation for A and B and in all cases they found that the measured polarization of the output photons was consistent with their being no definite causal order between when A and B was applied. Indeed, the measurements backed indefinite causal order to a whopping statistical significance of 18 -- well beyond the 5 threshold that is considered a discovery in physics.
Science Magazine applauds the experiments for "obliterating our common sense notion of before and after and, potentially, muddying the concept of causality.
In their experiment, Romero, Costa and colleagues created a "quantum switch", in which photons can take two paths. One path involves being subjected to operation A before operation B, while in the other path B occurs before A. The order in which the operations are performed is determined by the initial polarization of the photon as it enters the switch.... The team did the experiment using several different types of operation for A and B and in all cases they found that the measured polarization of the output photons was consistent with their being no definite causal order between when A and B was applied. Indeed, the measurements backed indefinite causal order to a whopping statistical significance of 18 -- well beyond the 5 threshold that is considered a discovery in physics.
Science Magazine applauds the experiments for "obliterating our common sense notion of before and after and, potentially, muddying the concept of causality.
You got drunk because you were going to break the table.
Science Magazine applauds the experiments for "obliterating our common sense notion of before and after and, potentially, muddying the concept of causality.
If anything I'd say a big "Duck you" was in order for guaranteeing that no non-physicist will ever understand quantum physics ever again. ... But on the other hand, it might get me out of the dog house for getting drunk and breaking the living room table...
Non-physicists may not understand quantum mechanics, but they're in good company.
I think I can safely say that nobody understands quantum mechanics. -- Richard Feynman
If it weren't for deadlines, nothing would be late.
https://arxiv.org/abs/1803.043...
I've been thinking about time lately. Why do we assume we only move forward in time? We move forward and backward in all the other dimensions, why assume we aren't oscillating back and forth in time? What difference would that make if we were? How would we know?
Consider the double slit experiment. Everyone reading this by now knows that if you send a single photon through a double slit it refracts as a wave until it hits the screen, then the "waveform" collapses and becomes a single point of light. Now imagine that quantum particle moving forward a ways, then moving backward a ways, vibrating back-and-forth in time. Each time it vibrates backward it interacts with itself as it's waveform briefly overlap it past self at the edges. This would cause it to refract against itself through the double slit. Then, once it's finally made it to the screen it appears to the observer as a single photon.
Quantum mechanics
The order does not matter
until classical
Some drink at the fountain of knowledge. Others just gargle.
Look up time reversibility and you'll see that it's not that this hasn't been considered (because math would tend to presume you can negative change in time). It notes that at the quantum level "the weak nuclear force is not invariant under T-symmetry alone; if weak interactions are present reversible dynamics are still possible, but only if the operator also reverses the signs of all the charges and the parity of the spatial co-ordinates (C-symmetry and P-symmetry)."
It's one reason some physicists have argued that perhaps anti-particles are merely their like particles going backwards through time and hence exhibiting reverse charge/spacial parity. Waves though are inherently time reversible. But particle-wave duality has everything as a wave, so that's something of an incongruence. There's also the small wiggle that a photon is its own anti-particle, so it if were to simple reverse in time randomly it'd self-annihilate.
My limited understanding of physics is that things like photons don't do that because anything travelling at the speed of light doesn't experience time/change, so the only way it could change directions is if the path it traveled on changed. Everything else that has mass is constantly changing and its those changes that derive its mass (warpage of space) and whatever charge it has. If it were to repeatedly move back/forward through time, then it would repeatedly engage in this conversions and we'd see gravity/charge ripples a lot more frequently than we do or there'd be more to it--the force of each ripple would be smaller (so the total observed would add up to the same) and movement speed would have an inverse effect on the charge (presuming that faster particles don't move more back/forward in time their charge smaller charge would be spread out over a wider area). That's not what observation/math currently shows.
Basically, any idea you come up with has to line up with the math/observations we already have while you introduce new math and/or observations with either the former leading to the latter or the latter requiring the former because the current math doesn't work. As much as we don't comprehend quantum mechanics, we do have math and observation that match and we're not seeing observations that inherently fail the math. This experiment, AFAIK, is really separate because causality is much more a presumption based on the math we have (ie, it's a convenient axiom to describe things). Now, if you could use this experiment to disprove the current math, that'd be interesting/useful (show that if you throw away the axiom and use some new axioms that match this experiment, the math fails).