The cat that wouldn't die | Hacker News Reader

The cat that wouldn't die

aeon.co

26 pointsHooke18 comments

Shcrödinger’s Cat is intuitive if the universe is lazily evaluated - everything is probabilities (or probability amplitudes, if we’re being technical) until an outcome is needed.

The box and cat and radioactive particle are in their own isolated system, cut off from the universe, so the universe can keep going without information from inside the box. From outside, the outcome in the box can remain probabilistic - it does not need to “be resolved”.

But inside the box (the isolated system) the cat knows very well if it’s alive or dead and the radioactive particle knows if it has decayed. The interior of the system must have resolved (an outcome was chosen) with respect to itself.

To match the first intuition, the universe must then be not merely lazily evaluated from your perspective, but actually lazily evaluated from every perspective.

Because everything is lazily evaluated with respect to everything else, this “inside the box or outside the box” lazy evaluation is happening all the time, everywhere. There’s no universal truth or sequence of events and there never was. There are only truths and sequences of events close enough not to matter at the levels of zoom humans operate at.

Whoa.

Which is why the unobserved portions of the universe do not exist.

How can you travel faster than light, if you haven't observed where you'll be? And if there are no particles before you arrive, what are you going to even observe?

No wonder the universe's expansion is a accelerating, we keep looking at it!

For what it's worth, it doesn't work this way at all with an actual cat in an actual metal box. You get a superposition if there's no possible way to tell what has happened. You don't get a superposition just because you sort of haven't chosen to shake a box yet.

Well, yeah, it's a thought experiment. But if we had some sort of ideal box then yes, the cat would actually in a superposition

It has to be a completely ideal box. That's a very extreme condition, so it messes very badly with people's intuition. It can not be a metal box with a cat in it, for example.

"It's a thought experiment" means "we can specify a totally ideal box." It doesn't mean "a finite metal box on a table will actually behave this way."

Schrödinger's Cat was intended to be easily imagined, but also obviously ridiculous.

I think that ends up confusing people a lot of people who can relate to the scenario, but don't understand that Schrödinger was accentuating the absurdity of the concept of superposition.

I really think that if the Cat was not a Cat, and if the binary was something other than the accessible-but-complicated concept of alive/dead, the thought experiment would be more useful to those of us who were not in the original messageboard threads between Schrödinger and Einstein.

This. Schrödinger's opinion was that the superposition collapses at the very beginning when the geiger counter goes 'click', after which everything behaves normally.

It's a thought experiment that proves the impossibility of an ideal box.

Has schrodingers cat been tested without hurting animals.

Yes, on graduate students at places like CERN, whose careers live or die based on the probabilistic detection of a single particle during their time "in the box".

Yes. If you do a diffraction experiment where a particle scatters off a lattice of atoms, but leaves no trace of which atom it interacted with, then you see a diffraction pattern that corresponds to the superposition of all the possibilities. If you do a modified experiment where the particle leaves one atom in a different state, then you see a different result, which corresponds to scattering off of just one atom, not the whole lattice.

It doesn't matter whether you actually go and check on the atom, though. What matters is whether there's something you could check on.

There's nothing to test.

The elements of the experiment are each well understood and defined, but adding them together you link two incompatible ways of looking at the world. The thought experiment puts it on you to reconcile that.

That would be pretty interesting. I dunno, maybe put an egg in there instead of the poison vial, creating a superposed system of intact egg/cracked egg instead?

But the whole point is that such a superposition is never observable. Any way of detecting it would cause it to collapse into one specified state. The only way to distinguish it from a non-quantum system is that it can be linked statistically to another quantum system. And even then, you're still only going to observe the same set of outcomes you'd see otherwise. The quantum part affects only the distribution of those outcomes.

> But the whole point is that such a superposition is never observable.

This makes it the perfect series of academic papers. "Practical Schrodinger's Cat, volume XIV: Still refrained from collapsing the waveform."

Sean Carroll's cat is awake or asleep.

> Nowhere in the mathematical formulation of quantum mechanics will you find an equation describing this collapse. We are left to assume it happens.

Nada. We are not left having to assume anything but the very clear laws we already have, and continually confirm.

The field equations clearly explain why a collapse “appears” to happen. There is no need to invent an actual literal collapse to explain something already explained.

Let’s keep going with cats.

We know from the laws of momentum and of light-matter interactions that if you throw a cat behind a couch it will “disappear” from existence.

Now imagine people proposing new “disappearing” laws beyond the laws we know. Or saying we are just supposed to assume there is one.

The problem with both responses is (1) the cat didn’t really disappear from the universe, we just perceive it that way, and (2) the reasons for that perception are already explained.

Likewise, quantum collapse doesn’t really happen, it is perceived, and we know why:

The field equations don’t just apply to cats inside boxes, but also cats outside boxes!

When an outside cat opens a box to determine the state of the inside cat, both cats are part of a single field equation. The total field equation covers all potential points of contact between the contributing fields of each cat. These points of contact are called “events” but not classical events. These events all happen. This is why we could have a dead/alive cat in a box in the first place.

(The field equations predict all the events, with different relative distributions, in superposition. Numerous elaborate experiments, and practical systems like quantum computers, both confirm these equations, including their distributions of superpositions.)

Now if you are an outside cat, which one are you? Pick any version based on which “event” you want, and that cat will see that event, see an inside cat alive or dead, and conclude the cat is alive. Or the cat is dead. But the cat never collapsed into one or the other. Another version of outside cat is seeing the other type of event in the total field equation.

So: each outside cat perceives a “collapse” of a dead/alive inside cat into either an alive cat, or a dead cat, but (1) there wasn’t a collapse, just two ways to half the field, and (2) the perception of a “collapse” is exactly what the field equations predict. There isn’t anything unexplained.

Apparently when we are very young and learning about the world, “disappearing” cats behind couches seems strange, and either inexplicable, or “needing” a special “disappearing” law, due to our lack of experience with occlusion.

Today, many people find “collapsing” cats (or atom states) strange and either inexplicable, or “needing” a special “collapse” law, due to a lack of experience with field equations of superpositions, that include themselves.

Contrary to politicians and newborns who may assume perception as reality. It is only a starting point for actually understanding reality. Which seldom actually conforms to our perceptions.

its so funny when you try to create an analogy to prove how something is absurd and the common understanding is that your analogy is how the world works

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