Not sure if this experiment is old news, but has anyone explained it? — TiredThinker
I have found a serious unrelated error in another video of Hossenfelder's, so my trust is broken, and I find myself questioning this dismissal.Surprised so few have approached this experiment like Sabina. So basically the data is interpreted wrong? Sensors 3 and 4 are wrongly not considered together for comparison? — TiredThinker
There is no information that can be sent to the past or FTL in any of these experiments. None of it constitutes time travel in any way. There are plenty of interpretations that explain the quantum eraser and explain entangled behavior in ways that obey the laws of locality and forward causation. It's only the counterfactual interpretations that need FTL explanations for these things, and even those don't propose information transfer to the past.this thread is about physics and implied time travel. — Mr Bee
The paradox is that, if you do that, and are therefore never born, you cannot go back and kill your grandfather before he procreates. So he does procreate, and you are born. So you do go back and kill him. So he doesn't procreate...The Grandfather paradox is the biggy. Here's my take on the subject: You go back in time and kill your grandfather before he procreates. Instantly the world you came from vanishes and is replaced by an alternate reality in which you don't exist. So you disappear and there is no way to tell time travel has occurred. It's a suicide mission. — jgill
I never considered this. It seems to me it depends on how long after your visit you look for alterations. The shorter the time, the less likely you'll see alterations. If the fate of a butterfly that lived today was reversed, that one lost butterfly wouldn't be noticable tomorrow. Even it one animal that survived by eating it ends up dying today instead, that wouldn't be noticed.On the other hand, suppose you go back in time and don't do any real damage. Then the minor alterations you might cause in the time stream are absorbed and normalized. I don't subscribe to a butterfly chaos, rather what Stanislaw Lem saw as a series of effects that peter out and vanish over a time. — jgill
But there will be differences that are noticable to people who know what it should have looked like. — Patterner
Well, yes. It would, off course, depend on people/beings outside of time. Superobservers. — Patterner
I'm certain I switch realities almost daily. I get red lights like you can't imagine. Even as a passenger I can affect the lights to the point that a driver said, "What the heck is going on?!? I can't believe how many red lights in getting!" Of course, I apologized, and explained it was because of me.I wonder, do we shift realities, never realizing? — jgill
Before we rebuild a classical version of the experiment it’s very important to understand a common misconception about the detectors. In most explanations you will see claims that detections at the bottom pre-eraser detector results in a certain pattern on the top detector and detections at the post-eraser detector will result in a different pattern at the top detector. Here’s an example from a PBS video showing a pattern on an interference screen (our top detector):
This is misleading. The top detector ALWAYS shows a smooth smattering of random dots. Always. Yes, I mean always. Nobody ever runs this experiment over and over and sees an interference pattern or banded pattern emerge on the screen. It’s always a smooth, random smattering of hits. People creating these videos aren’t deliberately misleading you; it’s just a shorthand way of talking about the final results that will be produced in later steps. Once all the data has been collected, we can filter the mess of top photons and say “only show me the hits that correspond with the eraser being used” and “only show me the hits that correspond with the eraser not being used” and they will show two different patterns. An interference pattern emerges out of the data if we look at the photons who had a partner detected after going through the eraser. A different pattern emerges for the top photons whose partners were detected before the eraser.
It sort of is. Despite my earlier skepticism, the video is spot on. I did research. One can choose to keep the which-path info and sort the incidences in a way where the wave pattern is absent, or one can choose to discard it and get the pattern. But in no case (at least in this experiment) is there reverse-causality going on. The frequent description of it is that the choice made at a certain time affects the outcome of what goes on at some prior time. Sounds like charlatans to me.Take [Hossenfelder's] word problem example about the age of the captain of the cargo ship. The implication here seems to be that Wheeler and everyone after him that found this experiment interesting is actually a collection of charlatans out to trick you by adding superfluous details. That isn't the case. — Count Timothy von Icarus
Indeed, kind of like not being able to measure both location and momentum of a particle.Neither is it the case that you can observe one outcome, then flip a switch and retroactively see it turn into a second outcome.
But the experiment does exactly that. It throws out half the data by sorting into multiple detectors. That discards which-way information for some events and not others.But her point about the pattern being the same until you pair down the data is, IMO, downright disingenuous. People running the experiment don't "throw out" data randomly, or throw it out in order to get some specific result.
Maybe it didn't, but it is critical to the experiment, to label every dot on the detector with a 1,2,3 or 4. Those numbers are assigned after all detections are done, but the location of each dot is noted before the detection at 1-4 is made. Clinical drug trials that don't track who took what pill are pretty useless.I don't think the video even mentions the term "coincidence counter."
I agree that Hossenfelder didn't convey that as clearly, but the gist of the (uncredited) alternative explanation is in in her video.For a much better explanation of the same thing:
Which interpretation did you feel being pushed in the video? I didn't see it. I didn't see any assertion of 'what there actually is' beyond empirical measurements, but maybe I wasn't looking for them.I'm not super familiar with Sabine Hossenfelder, but from my limited exposure her "science without the gobbledygook," is actually "philosophy of physics with my particular (read: correct) interpretations."
There are paradoxes? I mean, sure if you assume naive Newtonian or absolutist sort of world, relativity might contradict that, but I find relativity reasonably free of paradoxes.There is actually some similarities between this and time "paradoxes" related to relativity.
This is a problem only if you presume non-locality and locality at the same time. There are quantum interpretations that do either, but not both. So no paradoxes.Otherwise, you get into this weird situation where "yeah, cause' as commonly understood can move faster than light in terms of entanglement, quantum tunneling, etc. but it isn't really cause because "information" can't move faster than light,"
Yes, phase velocity of light is faster than c in cesium. So what? It's no more remarkable than the fact that I can make the red dot that my cat chases move faster than c (a lot faster). There's no FTL causality going on in any of those cases, no information getting anywhere faster than c.and you have the same sort of thing with cesium gas moving faster than light (or rather the peak of a pulse gaining on the front FTL), etc.
Do they actually have an experiment that can be interpreted as true reverse causality, that is effect in the past light cone of the cause event? The entangled pair usually space-like separated measurement events, not time-like separation. That's kind of soft retro-causality since the ordering of the events is frame dependent.
Which interpretation did you feel being pushed in the video? I didn't see it. I didn't see any assertion of 'what there actually is' beyond empirical measurements, but maybe I wasn't looking for them.
There are paradoxes? I mean, sure if you assume naive Newtonian or absolutist sort of world, relativity might contradict that, but I find relativity reasonably free of paradoxes.
Yes, phase velocity of light is faster than c in cesium. So what? It's no more remarkable than the fact that I can make the red dot that my cat chases move faster than c (a lot faster). There's no FTL causality going on in any of those cases, no information getting anywhere faster than c.
It is worth pausing at this point to consider the metaphysical motivation for taking a retrocausal approach to quantum theory, especially in light of circumventing these no-go theorems. The orthodox reading of the no-go theorems is that, whatever is said about the ultimate conceptual and ontological framework for understanding quantum theory, it cannot be completely classical: it must be nonlocal and/or contextual and/or ascribe reality to indeterminate states. In short, quantum theory cannot be about local hidden variables. Part of the appeal of hypothesizing retrocausality in the face of these no-go theorems is to regain (either partial or complete) classicality in these senses (albeit, with—perhaps nonclassical—symmetric causal influences). That is, retrocausality holds the potential to allow a metaphysical framework for quantum mechanics that contains causally action-by-contact, noncontextual (or where any contextuality is underpinned by noncontextual epistemic constraints), counterfactually definite, determinate (although possibly indeterministic), spatiotemporally located properties for physical systems—in other words, a classical ontology.
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