Does gravity slap us into reality?

[seer]

Observation of the quantum reduces its set of possible positions to a single position. It is no longer possible for it to be in position B if we have observed it to be in position A. When a quantum occupies a wide superposition, it behaves similarly to a wave. When its superposition is narrowed, approaching a single position, it behaves like a particle.

Yes but how does simple observation do this? Where is the physical connection?

[Boxing Pythagoras]

Yes but how does simple observation do this? Where is the physical connection?

I really don't understand the disconnect, here. It's fairly direct. If a thing is observed to be at position A, it cannot be at position B. That much makes sense, right?

[Sparko]

I really don't understand the disconnect, here. It's fairly direct. If a thing is observed to be at position A, it cannot be at position B. That much makes sense, right?

I think he is asking why is it observed at A? If you first looked at B, would it be there instead? Does it exist at all probable points until you look for it at a specific location and then "poof" there it is and nowhere else?

[Boxing Pythagoras]

I think he is asking why is it observed at A? If you first looked at B, would it be there instead? Does it exist at all probable points until you look for it at a specific location and then "poof" there it is and nowhere else?

That's the real odd part. Since it is probabilistic, it exists at all possible points simultaneously-- that is its superposition. Once observed, it still exists at all possible points, but now it is no longer possible that it exists in any position but the one at which it was observed.

Here's an analogy: let's say we have a pair of regular, six-sided dice and an opaque cup. We toss the dice into the cup, shake them up, and flip it mouth-down onto the table. The dice settle into a position, and are showing some value. However, until we lift the cup and observe the dice, we cannot know for certain what value they have. We can know only that their value corresponds to the following probabilities:

1-in-36 chance of a 2
1-in-18 chance of a 3
1-in-12 chance of a 4
1-in-9 chance of a 5
5-in-36 chance of a 6
1-in-6 chance of a 7
5-in-36 chance of an 8
1-in-9 chance of a 9
1-in-12 chance of a 10
1-in-18 chance of an 11
1-in-36 chance of a 12

Now, let's remove the cup. Let's say that our dice turned up a value of 8. Now, our odds are different. The odds that the dice show a value of 8 are 1-in-1, and the odds of any other value are zero. The simple act of observing completely altered the probability of the value of the dice. It is no longer possible for them to be currently showing any value but 8.

The same thing is true for quanta. Prior to observation, a quantum exists in a superposition. After observation, the odds remove all but one possible position.

Now, if you were to observe that a particular quantum is not in a particular position, without observing which position the quantum actually occupies, you would be narrowing its superposition, but not reducing it to a single position, and it would therefore still behave in a wavelike manner.

[seer]

I really don't understand the disconnect, here. It's fairly direct. If a thing is observed to be at position A, it cannot be at position B. That much makes sense, right?

OK, we have our photons shooting through the double slit - forming an interference or wave pattern on the screen. I walk in and look at it, or you turn the detector on. At that point "poof" (thanks Sparko) - the wave collapses and we get a common particle pattern. How does my presence cause the change? How does the detector cause the change?

[Truthseeker]

A probability wave packet can have an effect on others. Sure, if you observe the wave patterns on the surface of a swimming pool, they seem to not interfere with one another. But that is only a superficial observation. Say a water particle is up because a wave is passing through. A moment later, another wave hits the water particle. Now it goes even further up; maybe even pop off the surface entirely.

The particle detector at the double-slit board can be seen as a mess of probability wave packets. Now you see how it is possible for the particle detector to affect the experiment. Each packet is actually spread out all over spacetime.

[firstfloor]

I know it changes the results. But how does my looking at it effect it - physically touch it? Is there something shooting out of my eyes that is interacting with the particles?

The touching is done with photons which are carriers of the electromagnetic force and have momentum. You could think of it, very crudely, as a game of billiards. The illuminated object absorbs/emits photons and your eyeball converts their energy into electrical signals. Your eye does not emit a beam.

[shunyadragon]

We all know that the theory of relativity describes weirdo happenings in our world of space, time and mass.

We all know that quantum mechanics describes weirdo things in the world of the utterly tiny - the atom, the electron, the neutrino, the photon.

And we all know just how well tested both theories are, that they describe aspects of reality very, very well, but that they are also hopelessly at odds with each other.

Personally I do not consider these as weirdo nor is anything is hopelessly at odds here. This sort hype of science layman yellow journalism.

In the macro-world of the Newtonian mass and energy Physics the weak force of gravity of course dominates, but in the smallest scale of the Quantum world, gravity is not meaningful.

Well in the Jan 3 issue of New Scientist is an article titled “The Secret Life of Reality”. It seems that some researchers suspect that gravity may be the thing that stops us, in our daily lives, from acting in a quantum manner. In discussing the classical light interference pattern made when single atoms are fired at the two slit interferometer, the article states:-

“The only explanation for such a pattern is that each atom splits in two, with one part going through each slit, then interfering before it reaches the detector.”

Looking for frog hairs in quantum physics.


“... decoherence and destroys the interference pattern. It seems that the atom only behaves oddly when no one - or nothing - is looking.”

The refrigerator light is only on when we are looking.

The article discusses various ideas as to why this kind of thing might happen. It then deals with what happens with collections of atoms shot at interferometers. This is where gravity begins to come it. The bolding and coloring is mine:-



“No one really knows what to make of this [the kind of observations mentioned just before]. It is made even worse by the discovery that large collections of atoms seem to be unable to exist in superposition. We have made interference patterns with molecules composed of 800 atoms, but the more massive they get, the shorter-lived the superposition. This has led some to suspect that gravity might be the real reason why massive collections of atoms - including us - are not quantum.”



What makes this so interesting is that the technology nearly exists and physicists are beginning to think of testing this. For example, they are thinking of testing how:-



“... an atom in a supposition [quantum effect] experiences time [relativistic effect] as it flies through different paths in an interferometer and them recombines to produce an interference pattern”.

Too much time on their hands when there is little or no real sensational news coming out of physics and cosmology. Once you get past the news from the new accelerator, there is vary little that is news.



Keep your ears to the ground. This is amazing stuff.

Yawn! Don't do this around highways and airport runways, where mass and gravity rule on impact.

[seer]

The touching is done with photons which are carriers of the electromagnetic force and have momentum. You could think of it, very crudely, as a game of billiards. The illuminated object absorbs/emits photons and your eyeball converts their energy into electrical signals. Your eye does not emit a beam.

OK so the photons from my eyes or the detector are pulsing out and hitting or physically interacting with the photons in the experiment?

[Boxing Pythagoras]

OK so the photons from my eyes or the detector are pulsing out and hitting or physically interacting with the photons in the experiment?

No. Also, I think Firstfloor misunderstood what you were asking.

As I'm still unclear on what you aren't understanding from my explanation, let me pose this question again: do you agree that is a quantum is observed to be in position A, then it is necessarily impossible for that quantum to be in position B?

[klaus54]

OK so the photons from my eyes or the detector are pulsing out and hitting or physically interacting with the photons in the experiment?

I have no idea how you managed to get this from Firstfloor's post.

Yikes!

K54

[seer]

No. Also, I think Firstfloor misunderstood what you were asking.

As I'm still unclear on what you aren't understanding from my explanation, let me pose this question again: do you agree that is a quantum is observed to be in position A, then it is necessarily impossible for that quantum to be in position B?

I have no idea what that means or what is impossible or possible in the quantum world. But for the sake of argument I will answer yes. So how does that deal with my point?

[Boxing Pythagoras]

I have no idea what that means or what is impossible or possible in the quantum world. But for the sake of argument I will answer yes. So how does that deal with my point?

Alright. Now we have a basis with which to work.

Now, I'll move on to a stripped down analogy similar to the one I made with dice, a few posts back. Let's suppose that I have a coin. I flip the coin, and cover it before anyone can see how it turned up. The coin is showing either heads or tales beneath the covering. The probability that it is showing heads is 50%, and the probability that it is showing tails is 50%.

Now, I remove the covering. We see that the coin is showing heads. Now, the probability that it is showing heads is 100%, and the probability that it is showing tails is 0%.

Do you agree that the simple act of observing the coin changed its probability distribution?

[Sparko]

Alright. Now we have a basis with which to work.

Now, I'll move on to a stripped down analogy similar to the one I made with dice, a few posts back. Let's suppose that I have a coin. I flip the coin, and cover it before anyone can see how it turned up. The coin is showing either heads or tales beneath the covering. The probability that it is showing heads is 50%, and the probability that it is showing tails is 50%.

Now, I remove the covering. We see that the coin is showing heads. Now, the probability that it is showing heads is 100%, and the probability that it is showing tails is 0%.

Do you agree that the simple act of observing the coin changed its probability distribution?

The coin was always showing the same side, even when covered up. You just didn't know what it was. But in quantum physics the coin would be showing both sides up until you removed the cover. Schroedinger's cat.

[Boxing Pythagoras]

The coin was always showing the same side, even when covered up. You just didn't know what it was. But in quantum physics the coin would be showing both sides up until you removed the cover. Schroedinger's cat.

That would coincide with a Hidden Variables interpretation of QM. Regardless, it's not important to the analogy. I'm not asking whether the coin, itself, was affected. I'm asking whether the probability distribution which describes the state of the coin was affected.