Is the moon there when you dont look at it?

Justin1982

I'm looking for the technical answer to "Is the moon there when you dont look at it?" which should be based on the literal interpretation of the Copenhagen Interpretation of Quantum Mechanics firstly.
I'm also looking for the real answer which takes into account humans on the Earth, Copenhagen Interpretation and things like the Sun shining on the Moon.

Please before you reply be sure that you know the answer to at least one of these questions. I'm not really looking for peoples personal opinions or other interpretations of Quantum Mechanics. Also keep your answer short, sweat, dont use terms like "Bells Inequality says this or that" and keep the terminology easy to understand and self explanatory. At least in the first couple of replies. After that people can go into mental meltdown with their opinions.

With my education in QM I think the answer to the question is the following (Mathematically. And presuming that all the particles of the Moon disappear all together or dont. Probably unrealistic but just to save a lot of hassle)

|State of the Moon> = A x |Moon is not there> + B x |Moon is there>

Where
A = The probability that the Moon spontaneously disappears (presumably tiny)
and
B = The probability that the Moon doesnt disappear (presumably massive)

For the real answer I'm somewhat under the impression that the Sun shining on Moon keeps the Moon in the following state below even when we humans dont look at it. I'm thinking about the quantum watched pot here. As in repeated observations of an unstable quantum state — such as a radioactive atom — can make it live forever, or at least much longer than its natural lifetime.

|State of the Moon> = |Moon is there>

Skyfall

The answer is cheese

Justin1982

Skyfall wrote: »

The answer is cheese

Thats a slightly less cynical answer than the one my girlfriend gives me when I tell her I'm thinking about such questions You'll have to try harder!

When the moon disappears all of a sudden and the Earth's axis of spin starts going mental the smirk will be on the other side of your face! Wont it! :P

krd

Justin1982 wrote: »

For the real answer I'm somewhat under the impression that the Sun shining on Moon keeps the Moon in the following state below even when we humans dont look at it.

I'm not going to offer up my own theory, only to say I don't like this one. It's too much of a 'Monty Hall problem' interpretation of reality.

I don't know how to do those calculations, but I believe if you do them for the moon, your probability A is so tiny, it would take longer than the age of the universe for the moon to vanish.

M.T. Cranium

Surely the tidal effects of the Moon would be very chaotic if they depended on observers seeing it, to be there.

That would imply a probabilistic pattern of its "existence" based on human population modified by weather factors allowing for viewing opportunities.

But any two persons acting together could disprove the theory, by alternating attempts to view the Moon. Each would obviously see it, from the same location (virtually) and thus the theory is disproved by that circumstance.

Also, it is damned silly.

NIMAN

What colour is the sky in your world?

krd

M.T. Cranium wrote: »

Surely the tidal effects of the Moon would be very chaotic if they depended on observers seeing it, to be there.

The idea that there needs to be a human observer for the moon to exist is frankly stupid.

If astronomical bodies were really vanishing and reappearing, all the time, wouldn't we see astronomical effects all the time. We'd see gravity waves everywhere. Space would literally shimmer like the air on a hot day.

The idea that the rate of decay of an atom is spontaneous, and observation effects its' decay, sounds unprovable. It's more plausible, that a nucleus has a range of stability, and there is a range of specific external events (that may be rare events) that can destabilise the nucleus, causing a decay. And this would seem to be the case as in nuclear fission. The neutrons have a probability of colliding with a nucleus and causing its' decay. Increase the density of fissile atoms, and the probability increases - slow the neutrons down using water and the probability increases again by I think a factor of five. And this has been observed.

Randomness may see spontaneous, but if there are enough degrees of freedom in a system, the randomness will evolve, and spontaneity may be an explanation - but it's just as good a tautological explanation; "It's happens because it happens. It's there because it's there" - which means it's not a very good explanation.

Justin1982

M.T. Cranium wrote: »

But any two persons acting together could disprove the theory, by alternating attempts to view the Moon. Each would obviously see it, from the same location (virtually) and thus the theory is disproved by that circumstance.

Also, it is damned silly.

The question is a silly one to some extent. I ask it because I come across the question in a lot of popular science books recently. They generally put the question out there but never give an answer (presumably because its very controversial and one is obviously liable to look like an idiot if they give an answer that doesnt take into account all the variables around the moon)

The question as far as I know was popularized by Einstein because he didnt accept the Copenhagen interpretation of QM and it has also been popularized by David Mermin of late.

Silly and philosphical as the question is, I still think that physicists should be able to give an answer which is consistent with QM, rather than just assuming that the classical answer "Yes the moon is always there" is correct.

As far as I know, the classical answer is not correct exactly and if you want to answer the question while being consistent with the known, experimentally proven laws of physics then the answer is more complicated. Obviously the correct answer should approximate to the classical answer which is why we consider the classical answer to be obvious.

krd

Justin1982 wrote: »

Silly and philosphical as the question is, I still think that physicists should be able to give an answer which is consistent with QM, rather than just assuming that the classical answer "Yes the moon is always there" is correct.

It sounds like the thing celebrity professor Brian Cox, did on the television show 'A night with the stars'. Where he used the Dirac equation to calculate how long it would take for a diamond, he had in a box, to be outside the box. I think the figure was several times the age of the universe.

As far as I know, the classical answer is not correct exactly and if you want to answer the question while being consistent with the known, experimentally proven laws of physics then the answer is more complicated. Obviously the correct answer should approximate to the classical answer which is why we consider the classical answer to be obvious.

Classical theory always sounds more plausible, but there are so many instances where it breaks down, it's obviously incomplete.

As for philosophical questions. It's a little more complicated. Theories, equations, experimental results, and even what your own eyes are telling you. These are maps. And the map is not the territory. ........But we cannot discard the maps, as we would have nothing else - and that is absolutely nothing. So we have to accept them as reality. In fact you take it further and there is no territory, and no possibility of territory, and there are only maps. Science is all about finding maps - it hits a problem when there's features on one map that are not on another.

http://en.wikipedia.org/wiki/The_map_is_not_the_territory