Philosophy Discussion Forums

...Everett's interpretation of QM, which posits innumerable branching universes to rationalise the situation, is a popular alternative to the Copenhagen 'consciousness causes collapse' theory.

Just a correction: The "consciousness causes collapse" interpretation is not the Copenhagen Interpretation. The former is mostly associated with John von Neumann and to some extent John Wheeler. Copenhagenists generally believe collapse is an artifact of the quantum scale and macroscopic scale universes being distinct, and besides the wave function is only a mathematical description of quantum behavior, not a symbolic representation of physical reality. (I have a slightly different take but I don't wish to muddy the ongoing exchange of ideas with distracting details).

So if there is 'no mystery', why this vast body of theorization? What problem was Everett trying to solve? Why did Neils Bohr say 'if you have not been shocked by quantum theory, you haven't understood it yet?' I think this is where your instrumentalist view is challenged, actually.

I know this was addressed to Steve3007 but since I'm guilty of idolizing Bohr in my more sentimental moments, I'll just point out that rather than an instrumentalist view being challenged by the mystery of quantum mechanics, an instrumentalist view is possibly the only rational response to the mystery. It was Bohr's very wonder and appreciation of the mystery that led him to the conservative stance of the Copenhagen view, to preserve the integrity of scientific methodology in the face of phenomena outside (at the time) its epistemological purview.

Xris wrote: Brownian motion indicates particles but not electrons nor photons. As I have said, at some point energy does become mass. I am not saying the point of mass requires an observable image.

Can you give me the precise description of an electron or a photon that indicates it has the necessary requirements to be called a particle. How do you explain quantum entanglement other than instantaneous ?

When dealing with fundamental particles like the photon or electron, it is an experimental and theoretical fact that you never encounter a partial effect associated with them. You only ever measure whole electrons or photons, and never a part of them. Take light for example. If you lower the power of a light source (e.g. a laser) eventually the beam stops getting gradually weaker, and starts to blink on and off as you detect the individual photons.

There are two ways of explaining entanglement, neither suffers from real instantaneous effects, otherwise they would be wrong.

Interestingly the Wikipedia entry on Copenhagen says it

holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta, entities which fit neither the classical idea of particles nor the classical idea of waves. According to the interpretation, the act of measurement causes the set of probabilities to immediately and randomly assume only one of the possible values. This feature of the mathematics is known as wavefunction collapse.

I do note that there is a separate article on the Van Neumann interpretation. (We're not allowed to link to Wikipedia, apparently it's terrible.)

Note: I've added a small reply to Quotidian to my previous post.

Logicus:

As I understand the experimental setup when this experiment was originally carried out, the component used to "observe" the electron passing through one of the slits was not optical in nature.

Well, the experiment as specifically described here, and by Feynman in the Feynman Lectures on Physics, is a thought experiment - an amalgam of various different actual real-life experiments. We know from a combination of all kinds of similar experimental results, including ones that do use EM radiation, that this is the result we get.

I can understand the argument about clumsy scientists and crude measuring tools but even when the tools seem more appropriate to the task, it still seems to maintain its enigmatic results.

The thing is, he's using expressions like "clumsy scientists" to make a point: it's not just about making experimental blunders. The uncertainty is irreducible. It is a principle. But all principles are established from individual instances.

Quotidian wrote:Interestingly the Wikipedia entry on Copenhagen says it ...

I do note that there is a separate article on the Van Neumann interpretation. (We're not allowed to link to Wikipedia, apparently it's terrible.)

As I have repeatedly pointed out, the Copenhagen interpretation (from the 1920's) and its descendants, (consistent histories, decoherent histories) are local non-realist theories. This is just as well as realism has been experimentally refuted.

Steve3007 wrote:

(Nested quote removed.)


Picture yourself in a boat on a river.

There is another boat right next to you. Give it a kick. What happens? Both boats, yours and the other one, move away from each other. Now picture the other boat a little bit bigger. And bigger. And bigger. It will move less and less. But there is no point where it will suddenly go from moving a little bit to being completely unmoved.

The Earth is a huge boat.

Every beat of your heart makes the Earth move a little bit.

This was actually an awesome explanation.

I'm familiar with small boats and large ships so this image is helpful. Although, and I'd hate to disappoint you, but there is still something about this my mind just can't make sense out of. Especially if there are billions of feet all across the the world - that is not flat but more or less round - walking and running on it. I just can't imagine the huge earth moving the slightest from my heart beats.

I'm not trying be strong headed... this is just one of those sticking points for me. Maybe one day it'll make sense to me. Or maybe it never will.

Some belated comments (I can't keep up):

Logicus (Post #116):

To make it more confusing: The wave in "wave function" is a probability wave, not a physical wave. It is an indeterminate location of the particle until something external to it "collapses" the wave by, in some way, determining where the particle has to be.

Remember to ask yourself: what exactly is a "physical wave". The wave equation that describes the time dependent configuration of water-surface molecules is just as much a mathematical construct as the wave equation that describes the time-dependent probability of making a particle-like observation at a particular point in space.

The time-dependent probability wave can be thought of as passing through a gap in the same mathematical way as the time-dependent wave equation representing the position of water on the surface of the ocean.

This is the explanation for why it changes by observing it: observation collapses the probability wave.

You could say that. Or you could say that the mathematical process of finding the eigenvalues of the equation which we call "collapse" describes the process of observation. Maybe you're putting the cart before the horse. Or maybe the cart and the horse are just correlated.

Make waves, you're sure to be observed.

Steve3007 wrote:
Remember to ask yourself: what exactly is a "physical wave". The wave equation that describes the time dependent configuration of water-surface molecules is just as much a mathematical construct as the wave equation that describes the time-dependent probability of making a particle-like observation at a particular point in space.

The time-dependent probability wave can be thought of as passing through a gap in the same mathematical way as the time-dependent wave equation representing the position of water on the surface of the ocean.

You could say that. Or you could say that the mathematical process of finding the eigenvalues of the equation which we call "collapse" describes the process of observation. Maybe you're putting the cart before the horse. Or maybe the cart and the horse are just correlated.

This is nonsense. A water wave is a physical thing. The equations describing it refer to an element of reality. The wavefunction is not a physical thing (an experimentally verified fact) and it does not refer to an element of reality.

Supine wrote:This was actually an awesome explanation

Not only that, it was also the first line from Lucy in the Sky with Diamonds, which, in the context, I thought was particularly neat.

Steve3007 wrote: I can't keep up

Speed philosophizing, kind of like speed chess.

I'm slowly catching up (or painting the Forth Bridge).

Logicus, post #116 again:

I don't know if you noticed, but the cartoon was also stating that the indvidual particles go through both slits at the same time and interfere with themselves "in some way". That sounds more wave-like. In fact, I would say they are trying to express the behavior of the particles using an analog to the behavior of waves.

Yes, more attempts to hurridly explain an idea that is the culmination of 100s of years of scientific thought with snappy sound-bites. (I mean the cartoon. Not you.) But what can they do? I'm not knocking them. Just sympathising with their plight.

Is this a real problem, or a problem of how we are able to express it with language? The results would seem to indicate it is real. What does it mean? This has been an unresolved problem for decades.

A bit of both, I'd say.

Xris, post #117:

When the best can only give silly cartoons to explain the impossible we are all doomed. Doomed I tell you, doomed.

Thank you Corporal Fraser! I don't think that's all they can do. They can also teach 'O' level, then 'A' level, then degree level physics. Big complicated subjects do not lend themselves to explanation by sound bites, sadly. If they did, they wouldn't be big complicated subjects.

Quotidian, post #131:

Yes, will there ever come a time when everything in life can be explained through the medium of Beatles lyrics? I'm sure it won't be long.

---

Supine:

I just can't imagine the huge earth moving the slightest from my heart beats.

Neither can I. But not being able to directly imagine something doesn't mean it isn't true.

Here's another related thought: Space probes, like the Voyager probes, use a thing called "Gravity Assist" to gain extra energy to propel them to the outer reaches of the solar system. This means wizzing close by the big planets like Jupiter. But where does this extra energy come from? There is a sacred law called "conversation of energy" and if we break it we are severely punished. Answer: it comes from slowing down the planet, in its orbit around the sun, very, very, very, slightly.

This is difficult to imagine too. But in this case, we know it must be true because otherwise we wouldn't have any pictures of Uranus and Neptune.

Steve3007 wrote:The thing is, he's using expressions like "clumsy scientists" to make a point: it's not just about making experimental blunders. The uncertainty is irreducible. It is a principle. But all principles are established from individual instances.

Actually the point, as I see it, is that huge, lumbering primates are not adept, with tools or without, at handling sub-atomic particles. We are on the wrong scale to attempt these experiments without interfering with the results.

Steve3007 wrote:Here's another related thought: Space probes, like the Voyager probes, use a thing called "Gravity Assist" to gain extra energy to propel them to the outer reaches of the solar system. This means wizzing close by the big planets like Jupiter. But where does this extra energy come from?

The energy, meaning the increase in velocity, comes from the orbital speed of the planet. During the period the probe is within the gravitational field of a planet, it picks up some portion of the planet's orbital velocity. The longer it remains and the closer it can get to the planet, the more of the orbital velocity it picks up. It also alters trajectory, so the time is usually limited by that more than anything. When you first think about this, you realize any amount gained during the approach is lost during the following trip outward. The only thing left is the orbital velocity.

The energy, meaning the increase in velocity, comes from the orbital speed of the planet

I did actually say that just after the part that you quoted. My question was rhetorical.

Yes, I see that now. I was in a bit of a hurry in the exchanges and missed it. Your way is a bit more poetic, maybe. If it slows the planet down very slightly there is another effect: the planet moves to a slightly more distant orbit. And it continues to sweep out equal areas in equal times.

Xris wrote: Men once expected the gods to come down to earth and realise all our dreams but we forgot the golden rule. Heaven is for dreamers and gods. Earth is for humans and reality.

Are you talking about the "reality" of this flying, life-coated ball of concentrated "light-like" energy, suspended in an "infinite appearing" spatial dimension, along with zillions of other flying balls?

The recognition of the "strange dreaminess" of that scenario is a crucial first step toward any hope of apprehending its apparently stranger underpinning.

seeds