Of course not, that would be immoral. They’ll track trollies and baskets, then tag it to the till and your loyalty card. It would be a lot more consistent, and harder to dodge.

I can see multiple uses for the tech. Unfortunately, many are a but dystopian, but some are legitimately useful.

You could detect decoherence in the system, that doesn’t indicate a human observer, however.

That process is, however, used to protect cryptographic keys, transfered between banks. A hostile observer collapses the state early. The observer gets the key instead of the 2nd bank, which is extremely conspicuous to both banks.

We can observe the end result. E.g. observing the screen only, and you get wavelike behaviour. When you also observe the slit, the wavelike behaviour disappears, and it seems particle like.

Both end in an observation, 1 has an extra observation.

Depends on how you are observing it photons impart energy and momentum. The true, detailed explanation is a lot more convoluted, it’s all wave interactions, in the complex plane. However, digesting that into something a layman can follow is difficult.

The main point I was trying to get across is that there is no such thing as an independent, external measurement. Your measurement systems minimum interaction is no longer negligible. How that is done varies, but it always changes the target and becomes part of the equations.

We know how it works, we just don’t yet understand what is going on under the hood.

In short, quantum effects can be very obvious with small systems. The effects generally get averaged out over larger systems. A measurement inherently entangled your small system with a much larger system diluting the effect.

The blind spot is that we don’t know what a quantum state IS. We know the maths behind it, but not the underlying physics model. It’s likely to fall out when we unify quantum mechanics with general relativity, but we’ve been chipping at that for over 70 years now, with limited success.

Observer here doesn’t mean the same as the layman meaning. It’s anything that interacts with the system while it’s developing.

Interestingly, it actually can be used for a presence detector, at least in a sense. You can use it to transfer cryptographic information. If no-one is listening in, about half your sent numbers are wrong, but you can agree on what ones. However, if someone is listening in, all your data gets randomised.

They actually now use this system to transfer information between banks. They send a random stream of 0s and 1s over a fibre optic cable. They then send (semi publicly) which bits made it properly. If someone spliced into the fibre, they would get the encryption data, but the target bank would not! They know instantly that something is wrong.

For those confused, it’s worth noting the difference between observed as a layman concept and as a quantum mechanical one.

In QM, to observed is to couple the observer to the “system” being observed. Think of it like “observing” your neighbour, over a fence using a BB gun. When you hit flesh, you know where your neighbour is. Unfortunately, the system has now been fundamentally changed. In a classical system, you could turn down the power, until your neighbour doesn’t notice the hits. Unfortunately, QM imposes fundamental limits on your measurements (heisenburg and his uncertainty principal). In order to observe your neighbour accurately, you need to hit them hard enough that the will also feel it and react differently.

QM behaves in a similar way. Initially, the system is just a single particle, and is not very restrained. This allows it to behave in a very wave like manner. When you observe it, the system now includes the whole observation system, as this coupling propagates, more and more atoms etc get linked. The various restraints cause an effect called decoherence. The system behaves ever more like a classical physical system.

In short, a quantum mechanical “observer” is less sneaky watching, and more hosing down with a machine gun and watching the ricochets.

Theories can be a stepping stone to other theories. Until we explore those chains, we don’t know if there is anything useful at the end.

E.g. initially, lasers were a solution looking for a problem. An interesting quirk possible due to some interesting bit of physics.

Maths explores idea spaces. Much of that is purely of interest to other mathematicians. However, it sometimes intersects with areas of interest to other scientists, at which point it becomes extremely useful.

There are several major hurdles, and no particularly strong evolutionary drive to overcome them.

The first is breathing. Fish “breath” water. Shifting to air takes a huge reconfiguration. It also compromises their ability to process water.

The second is power. “Flying” fish are actually gliders. They build up momentum in the water before launching themselves into the air. They don’t actually have the ability to flap and maintain their flight. Developing the muscles for this would likely compromise their swi.ing slightly. That would be a far bigger issue, compared to a bit of extra gliding.

A flying fish’s goal is to break contact with an underwater hunter, before reentering the water. A steerable glide is more than enough of this. There is simply no pressure to advance it further.

I don’t know if it’s real or just nostalgia, but reddit is massively worse than I remember. I’ve gone back to nose a few times, and it feels like a ghost town, compared to what it used to be.