TL;DR I want to warn readers (non-physicists) of my blog that it is wrong to claim that erasing or not detecting "which-path" information in DS and DCQE experiments is the same as turning off your recording device or deleting a data file on your PC, and it is wrong to assume that the particle creates diffraction pattern just because the Universe "knows" that you don't have "which-path" information recorded anywhere (although detector might have detected it earlier). But to get this to my readers I need a simple, dumbed down analogy. Long story: I know that there have been many discussions about DS and DCQE experiments. But I would like to have some simplified, dumbed down explanation which would prove why exactly the people who claim that DCQE changes the past or that it proves that observing the results affects the experiment are wrong. I am working together with a friend on an article in our native language (Latvian) where we'll try to explain the basics to an average technically thinking reader who might have no quantum physics knowledge at all. I myself am not physicist nor mathematician. I have a degree in programming, but I selected Beginner level for this thread because I feel like a beginner in quantum physics. That's why I hope on your help to explain it all in as simple words and analogies as possible. This all started with a "crack-pottery" case discussed in this thread: https://www.physicsforums.com/threads/double-slit-experiment-with-detectors-not-recording.414617/ I saw the video mentioned there, so I did a web search for keywords "double slit tape recording", and that thread was the best one but too technical and full of physics details. Essentially, this guy, Thomas Campbell in that video (and also in some later videos in Calgary) claims that in double slit experiments it is possible to observe particles without any interaction with particles, and thus it is wrong to say that particles are collapsed to wave functions just because detectors have somehow "damaged" the particles. And he says that not detecting or erasing "which-path" information is the same as turning off the recording device or deleting recorded data files while the experiment is being run as usual, with detectors being on, but no-one consciously observing the experiment real-time. But when reading about these experiments, I've got impression that detecting a particle implies some interaction with it because it is not possible to "observe" a particle in the same sense as we observe macroscopic objects. We can look at a ball and the ball won't be affected by our vision at all. But we cannot look at a photon or electron in the same way, we have to interact with it to detect its position. Am I right this far? And in that case in DCQE experiments they are not just merely erasing "which-path" information. They are first "damaging" the particle to obtain that information, but at that point the information is not stored anywhere. We could say, that at the moment of detection, the "which-path" information is not real information, it is potential information and we simply cannot record it on some media (tape or computer RAM) before the measured particle hits the screen because then our recording system must be capable of recording bits of information faster than the time required for a particle to travel from slits to the screen. The following sentence from Wikipedia seems to prove my point: "Experiments observe nothing whatsoever between the time of emission of the particle and its arrival at the detection screen." And then later in DCQE experiments when they are "erasing" the information, they are "undoing" the damage done by the detector to a particle, at the same time losing the "which-path" information because it was not stored anywhere, anyway. This means that you cannot make an analogy of erasing a recording on a tape (or a file on computer's disk or in RAM) or running detectors without recording the data. Or maybe I'm wrong and it is actually possible to record "which-path" information on a computer before a particle reaches the erasing stage of DCQE and keep the "which-path" information recorded on a computer even after it has been erased in DCQE itself? I highly doubt that, but I'm not sure. In case if I'm right and erasing information in DCQE is not the same thing as erasing data already recorded, the claim "Scientists show future events decide what happens in the past" http://www.digitaljournal.com/scien...pens-in-the-past/article/434829#ixzz3hepfJZ52 also seems somewhat exaggerated crack-pottery with wrong conclusions. Still I'm curious, has there been any experiments done which would prove those "crack-pot" guys to be wrong? It would be actually easy to implement. Just take a classical DS experiment and make it fully automated black box, so no conscious being can observe the results real-time. Record the detector data and screen data as two separate sets of information (e.g. data files). Repeat the experiment twice. Now you have two sets of pairs detection+screen. But do not look at contents of the data files yet. Erase the "which-path" file from your second data set. And only then take a look at all the data you have. If "crack-pots" are right, then you'll find diffraction pattern in the set where you have deleted the "which-path" data, and no diffraction pattern in the set where both files are present. But if you won't get such results, then it will prove "crack-pots" wrong once and for all. I guess, such experiments haven't been done because they sound too crazy and do not make much sense for physicists. But still, it would be great to be able to prove that it does not work that way. And there is one technical thing which confuses me. Wikipedia claims that such experiments have been done also with molecules. But is it possible to do DCQE with molecules? That would negate quantum weirdness to some extent because it should be easier to detect a molecule and then delete that "which-path" information, and it would be closer to our macroscopic world. I'm hoping for you, physicists, to confirm my conclusions or explain where I'm wrong, so I can then pass that to readers of my blog. Thank you for your time reading this.