this post was submitted on 11 May 2024
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No Stupid Questions

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The Weeping Angels apparently originated with Steven Moffat seeing a statue of a weeping angel in a structure in a cemetery and returning later to find out it was gone. At least according to this RadioTimes article. They first appeared in 2007 in the episode Blink.

I am wondering if this mechanic has been done before though?

It's become quite common in the indie horror scene.

In the 2007 video game Sherlock Holmes: Nemesis Watson would not move if in the player's view but would teleport behind the protagonist when given the opportunity. A video of it can be found here.

Considering this could be an easy place holder for developers or a way to get around programming walking animations all together I'm surprised no one took the idea and ran with it before then.

All that said it could have been used in books or movies. Maybe a twist on some other vision-centric myth like Medusa or Orpheus and Eurydice?

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[–] hperrin 31 points 6 months ago (2 children)

“Observation” in quantum mechanics doesn’t mean a person looking at them, it means taking a measurement, which involves interacting with the particles somehow. It’s that interaction that causes the particles to behave differently. In other words, photons behave as a wave (moving according to a wave function) until another particle interacts with them, at which point they behave as a particle (moving in a straight line). See the various different double slit experiments for evidence of this.

[–] [email protected] 8 points 6 months ago* (last edited 6 months ago) (1 children)

I thought the delayed choice quantum erasure experiment showed it wasn't the act of measurement that collapses the wave, but rather it depends on whether the information regarding its path was retrievable or not.

Scarcelli et al. (2007) reported on a delayed-choice quantum-eraser experiment based on a two-photon imaging scheme. After detecting a photon passed through a double-slit, a random delayed choice was made to erase or not erase the which-path information by the measurement of its distant entangled twin; the particle-like and wave-like behavior of the photon were then recorded simultaneously and respectively by only one set of joint detectors

[–] hperrin 6 points 6 months ago (1 children)

Yeah, I guess in my statement I should have said “unless” instead of “until”, because it’s not time dependent. But it’s still the act of measurement, not the act of a conscious person looking at that measurement, that causes the collapse of the wave function.

[–] [email protected] 1 points 6 months ago* (last edited 6 months ago) (1 children)

it’s still the act of measurement, not the act of a conscious person looking at that measurement, that causes the collapse of the wave function.

That's not the case here; when particles are measured and the which path information is erased/nonrecoverable it remains a wave:

what makes this experiment possibly astonishing is that, unlike in the classic double-slit experiment, the choice of whether to preserve or erase the which-path information of the idler was not made until 8 ns after the position of the signal photon had already been measured by D0.

[–] hperrin 1 points 6 months ago

That may not be the correct way of saying it. You can equally explain the data by phrasing it, “when the photon remains a wave, the which path information is nonrecoverable.”

Moreover, it's observed that the apparent retroactive action vanishes if the effects of observations on the state of the entangledsignal and idler photons are considered in their historic order. Specifically, in the case when detection/deletion of which-way information happens before the detection on D0, the standard simplistic explanation says "The detector Di, at which the idler photon is detected, determines the probability distribution at D0 for the signal photon". Similarly, in the case when Dprecedesdetection of the idler photon, the following description is just as accurate: "The position at D0 of the detected signal photon determines the probabilities for the idler photon to hit either of D1, D2, D3 or D4". These are just equivalent ways of formulating the correlations of entangled photons' observables in an intuitive causal way, so one may choose any of those (in particular, that one where the cause precedes the consequence and no retrograde action appears in the explanation).

The total pattern of signal photons at the primary detector never shows interference (see Fig. 5), so it is not possible to deduce what will happen to the idler photons by observing the signal photons alone. In a paper by Johannes Fankhauser, it is shown that the delayed choice quantum eraser experiment resembles a Bell-type scenario in which the paradox's resolution is rather trivial, and so there really is no mystery. Moreover, it gives a detailed account of the experiment in the de Broglie-Bohm picture with definite trajectories arriving at the conclusion that there is no "backwards in time influence" present.[23] The delayed-choice quantum eraser does not communicate information in a retro-causal manner because it takes another signal, one which must arrive by a process that can go no faster than the speed of light, to sort the superimposed data in the signal photons into four streams that reflect the states of the idler photons at their four distinct detection screens.[note 2][note 3]

But more importantly, you will get the same results regardless of whether a human being is there to observe it. It’s the detection of the photon (by way of interacting with the photon detector) that matters, not whether there is a person there to observe the detection.

[–] MrJameGumb -3 points 6 months ago