Is the Moon There When Nobody Looks?

[Cosmo16]

I remeber that Einstein and is supportors asked if no one in the world was looking at the moon, then was it not there based on quantum. The proponents of quantum at the time answered with a resounding "Exactly".

But, is that correct? Since the gravitational influence would still be felt then wouldn't the moon still be have an affect and thereore still be there?

p.s. I don't remeber what principle of quantum they were debating.

 

[lawtonfogle]

This is like the tree in the forest. If it falls, does it make a sound. The answer is no, it does not. What it does make is a vibration in the air. Why this is not considered a sound is that it take an ear and a brain to make it a sound. Sound exist only in our minds.

Even if you look at the moon, you do not see it. What you see is the light bouncing off of the moon. As far as human have interacted with the moon, the moon must exist in some ways.

It must exist in a way we can touch it, because we have walked on it (we as in mankind). It must exist in a way that light comes off of it, no matter where the light comes from. It must also exist in a way that it has gravity, And it must exist in a way it can move.

Can we see the wind?

 

[Cosmo16]

that makes sense

 

[Quantum_Prodegy]

This is like the tree in the forest. If it falls, does it make a sound. The answer is no, it does not. What it does make is a vibration in the air. Why this is not considered a sound is that it take an ear and a brain to make it a sound. Sound exist only in our minds.

Wow, I've never thought of it that way, very interesting and it makes complete sense.

 

[mtong]

Also, although we are not visually observing the moon in this situation we are still observing the gravitational effects of it. So in your scenario we really never stop observing the moon, so it does not apply to the 'Schrödinger's Cat' type situation (Duality).

If however we were able to remove all forms of observations of the moon then it could be said that the moons exists in two states, both there and not there.

Correct me if i am wrong :D

 

[lawtonfogle]

If we remove all ways to observe the moon, then how could we say it is there? The information one can use is that the moon was there a while ago, but who says it is there now, and even if it is observed afterwar, that stills does not mean it was there at the time in question.

 

[ben_jamin]

are you talk about the physics? I feel it is a kind of philosophy, so measure theory will be a part of philosophy?

 

[Problem+Solve=Reason]

idk... If no one is around, prove the tree made a vibration...

And to answer Cosmos's question. Those light rays we see are evidence enough to say that it is there. If you want to get scientifical about it, we have enough info to prove that as well.

----- Life is a Problem... SOLVE IT!

 

[caribou]

I remeber that Einstein and is supportors asked if no one in the world was looking at the moon, then was it not there based on quantum. The proponents of quantum at the time answered with a resounding "Exactly".

But, is that correct? Since the gravitational influence would still be felt then wouldn't the moon still be have an affect and thereore still be there?

p.s. I don't remeber what principle of quantum they were debating.

Like Schrodinger's Cat, it's a question about macroscopic quantum superposition states.

The modern answer to the question is that particles from the sun, other stars, the Big Bang, etc. interact with the moon and cause it to go from a superposition of possible positions to a very definite actual position by a process called "decoherence".

Simply put, these particles "observe" the particles in the moon.

The famous example of decoherence is that the superposition of two positions 1 mm apart for a 1mm dust grain far out in deep space will decohere in a billionth of a second just from interactions with the photons remaining from the Big Bang.

Something like the moon will decohere even faster and remain in a very good approximation of a good old-fashioned textbook classical orbit whether or not anyone is looking at it because the particle interactions are "observing" the moon.

 

[Problem+Solve=Reason]

I'm currently reading about Decoherence, but I thought i would ask you: If we have never seen the moon, could we prove that it does exist through Dechoherence?

---- Life is a Problem... SOLVE IT!

 

[caribou]

I'm no expert but I think we can prove the moon would exist in the usual sense by the constant particle interactions causing continuous decoherence.

 

[QMistic]

I am rather new and not a physicist. So those who are, I hope you will be patient with my limited understanding. So take this as a challenge if you wish, but I am going to make a few comments regarding my understanding of QM.

Cosmo

But, is that correct? Since the gravitational influence would still be felt then wouldn't the moon still be have an affect and thereore still be there?

It is not that the moon and it's gravitational affects are not there, but it is OUR perception of matter that does not take place until we 'look at it'. Only then the ever present state of and interaction of waves "collapse" into particles that we perceive. The processes we observe as matter and gravity's affect on them take place whether or not we are watching.

Caribou

Something like the moon will decohere even faster and remain in a very good approximation of a good old-fashioned textbook classical orbit whether or not anyone is looking at it because the particle interactions are "observing" the moon.

This is all new to me. Are you saying that QM theory now allows for "particles" to be the 'observer' so that they cause their own collapse? I guess I'm from the old QM school so maybe this is new stuff I don't understand.

Sim

 

[caribou]

This is all new to me. Are you saying that QM theory now allows for "particles" to be the 'observer' so that they cause their own collapse? I guess I'm from the old QM school so maybe this is new stuff I don't understand.

This work I'm referring to is quite recent so the old QM school isn't that long ago. Decoherence was theoretically suggested in the 1970s and only clearly experimentally confirmed in 1996. It's an extremely important effect, though.

I'm still learning the details but the basic idea is that particles interacting with each other act as the "observers". There is no collapse of the wavefunction anymore in the modern interpretations I'm referring to. A particle loses its strange quantum effects to a greater and greater extent as it interacts with more and more other particles.

The famous two slit experiment is an example of that. If a single particle is sent towards the slits and detected on the other side then there are interference effects and the particle acts like it went through both slits at the same time and interacted with itself on the way.

However, if the particle interacts with a lot of other particles on its journey then the interference effects disappear and the particle acts like it went through just one slit or the other. Interactions make the particle go from quantum weirdness to classical behaviour.

An isolated particle or isolated system of particles will start weird and stay weird, though. It takes an "environment" to break down the weirdness.

Also, some things like electrons interact easily and some things like photons don't. This is the reason we tend to think of photons in light as waves and electrons as particles. The photons don't decohere so easily and keep their interference effects better.

 

[QMistic]

Thankyou Carabou for that summary.

This is new to me, and interesting

An isolated particle or isolated system of particles will start weird and stay weird, though. It takes an "environment" to break down the weirdness.

Also, some things like electrons interact easily and some things like photons don't. This is the reason we tend to think of photons in light as waves and electrons as particles. The photons don't decohere so easily and keep their interference effects better.

Can you direct me to anything published of this sort that an amature physicist can get into?

Sim

 

[Problem+Solve=Reason]

I've been reading about Decoherence off this article. And yes, it is very interesting... Try out this link QM: http://plato.stanford.edu/entries/qm-decoherence/

 

[caribou]

Depends what you are interested in, I guess.

I don't really know of any non-technical explanations in books that are much better than the pages a Google search on "decoherence" will find, with pages like the one Problem+Solve=Reason gives or this one:

http://www.decoherence.de/

People like Zurek, Paz, Joos, Zeh, Gell-Mann, Omnes and Hartle are some of the names of experts in the field.