[ajuc]

But I can record that screen on another camera and look at that recording the next month :)

Are we now also assuming causality can go both ways in time :) ? Or am I changing the recording the moment I look at it :) ?

It's such a stupid theory :)

[reggieband]

Congratulations, you just re-invented Schrödinger's cat thought experiment [1]. One interpretation of this phenomenon is that the universe exists in a superposition of states until an observer causes the collapse through observation. What you dismiss as "such a stupid theory" is an idea/paradox that has confounded quantum physicists for decades.

1. https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat

[ajuc]

I don't think anybody seriously thinks Schredringer's cat is in superposition in real world. It's a living macroscopic thing at room temperature, it interacts with the universe and would collapse immediately. So would the recording.

[reggieband]

Well, you can scroll down to interpretations in the article I linked and choose any of the ones that fit your fancy. Or you can propose a new one. But acting like you are right and all other interpretations is wrong is merely hubris. As far as I am aware, this is an open issue and claiming that "... no on seriously thinks ..." isn't a valid or serious argument.

[stale2002]

No, the camera that you observe 1 month later would be in a quantum state, until you actually observe it.

The "recording" would be in multiple states until you observe the recording.

[ajuc]

Except when we do the experiment in the real world we can't keep the quantum superposition for macroscopic objects from collapsing and now we're claiming it just happens because we don't know the answer.

That's the difference between declaring entangled photons be in superposition and declaring a tossed coin being in superposition because I covered it with my hand without looking.

One is state of the universe, the other is my lack of knowledge.

But sure - we can go on declaring everything entangled all the way up. Then we declare that the whole universe except the conscious observer is in a superposition of states until the observer decides to observe it or not.

The problem with that is that I'm a part of the universe and I have no proof that I have a free will independent of everything else. It just feels like it :)

So assuming everything waits for me to decide seems very self-centered and unjustified by the evidence as opposed to everything happening when it happens and my decision being predetermined like everything else.

[stale2002]

> Except when we do the experiment in the real world we can't keep the quantum superposition for macroscopic objects from collapsing

No. You don't actually know that. Because the act of you "observing" this macroscopic object, could be the cause of this object collapsing.

So the macroscopic object that collapsed could be due the fact that you have observed it.

> One is state of the universe

You have no way of knowing the state of the universe, unless you have observed it. So if you are ever looking at any state of the universe, it is observed and has already collapsed.

> Then we declare that the whole universe except the conscious observer is in a superposition of states until the observer decides to observe it or not.

Yep that's the theory.

> I have no proof that I have a free will independent

Yes, that could be true as well.

> seems very self-centered and unjustified

So, here we get to the Crux of the matter. No matter where we say that the wave "collapses", it is all unfalsifiable.

It could be that the observes collapses it.

It could be that it was collapsed once it had any interactions with a photon or the smallest microscopic particle.

Or, as you pointed out, it could be that the universe has never collapsed, and the whole universe is in a super position right now.

And all of these positions are equally unfalsifiable. There IS no justification that any of these are correct, and there is no way of saying which is more justified.

So, yes, it is unjustified. But it is just as unjustified as any other collapse theory.

It is a fools errand to give arguments as for why one collapse theory is worse or better than any others, and they are all equally unfalsifiable.

[ajuc]

It seems to me that one of these positions makes much more sense because it assumes the least unproven behaviour.

We measure the wave collapsed as if the cat died in minute 3 of being in the box (we can calculate that from the amount of CO2 and other methods). You say "we don't know if it really collapsed in minute 3, or collapsed now and retroactively made every measurable fact look like it happened in minute 3".

To me it sounds like "Earth can be 6000 years old - God simply made it look like it has billions of years". Sure I cannot experimentally distinguish between these options, but one is much simpler.

I guess with QM at least we "caught God doing the retroactive stuff" for small things, but we had no proof it had anything to do with consciousness, and it never seems to happen for macroscopic stuff.

It's like I see street lamp goes black when I'm near it and assume it's because I was close to it. It's easy illusion to get into, because you never see the lamps that go black when you're not around. But there's no justification that you/consciousness is needed.

[stale2002]

You are once against picking a specific time as to when exactly collapse happens.

I would argue the opposite to you, actually, and instead say that the whole world is entangled, and the wave never collapses.

We can't even prove that collapse happens in the first place.

So, assuming that things never collapsed is actually the situation with the least amount of unproven assumptions, and it literally is not assuming that the collapse ever happens.

That's much better than saying that the wave function collapses at exactly the atomic level or something.

All of these points in time are arbitrary.

> retroactive stuff

There is nothing retroactive about any of this. Before collapse, it exists in a state of it not happening and happening at the same time. That's not retroactive.

[ajuc]

> You are once against picking a specific time as to when exactly collapse happens.

Well Many Worlds assumes multiple universes that's kinda big assumption too. But I agree it's the most elegant interpretation.

> All of these points in time are arbitrary.

If we exclude Many Worlds then collapse happens. We have to conclude it can happen for microscopic objects at least.

What I cannot understand is how people then jump to assume it's consciousness that is the important distinction. What's the reasoning here? We can't even define it, we don't know if we have it, we don't know if it's important, why put it it physics?

> There is nothing retroactive about any of this. Before collapse, it exists in a state of it not happening and happening at the same time. That's not retroactive.

Ok, if you don't go back and recreate everything that happened when I observe it then you have to remember all the possible paths and chooses one of them when I look at it.

If I had to code the universe I wouldn't write it in such a way that it needs to remember everything that could happen but was never observed by a player :) Seems like a huge waste of resources if I could just as well cull the statetree early.

We even have an interaction that AFAIK cannot be isolated (gravity) - how's that working with the cat in a box? When it falls dead it curves spacetime outside of the box differently after all.