The measurment problem

[weaksauce]

This is ridiculous, the cat is alive and dead at the same time? Now the theory might say whatever it wants to say, but we know from a fact that in this time and space the cat is either dead or alive. Just because a conscious mind doesn't know doesn't make it both.

Unless, of course, if you go by the multi verse.

In one universe it is alive, in the other it is dead.

Secondly, how do you know that the one you are experiencing, is the "right" one? How is this You the "right" You?

Why would there even be a difference between this and the other?

Is there even one this and one the other?

You may see it, as there is one, with everything. The cat is both dead and alive in the one parallel universe. You are parallel.

That is seriously fucked up.




On a side note, how should science be seen?

Should you see it as models, and are the models then real? Are there actually real things we call quarks or strings that have properties like being a blue ball and build up the universe like lego bits? Although it's interesting that there are lego bits that can be built with.

Or is it a phenomenon that is only understood by the effects of it? That there is no actual "thing", but an occurrence of happenings which behavior we can observe and explain in math?
That there is no actual "thing" in the middle of, just the properties and effects, that is the phenomena?

I am more in favor of the latter. I don't believe you can go around legobitizing everything. That seems to give more problems than solutions.

It's ridiculous to say that an photon can be both particle and waves. There is no photon! It's a phenomenon observed in and described in some cases with the model of a particle and in others with the model of a wave, but the models are fake! There are no models in reality. Really this should just be calculated on and observed by on the effects, ie magnetic fields induce a force in a wire or light bends after gravity.
You might use the model to make the calculations, but the model and the math itself isn't the actual phenomena. The phenomena is, and you may calculate it with models.

If you try to visualize it, it just gets weird. First you have this blue ball and then you have this transparent, graph-like 2d wave in 3d space and then you try to link them together. Neither are real and it just gets very strange trying to make them "more real" by linking them.

 

[Bouncing Zabaglione Bros.]

You shouldn't quote Schrodinger's Cat unless you understand that it's a thought experiment, and was meant to disprove/poke holes in early quantum theory. It's not as simplistic as "it's dead and alive at the same time".

Schrödinger's cat is a seemingly paradoxical thought experiment devised by Erwin Schrödinger that attempts to illustrate the incompleteness of the Copenhagen interpretation when going from subatomic to macroscopic systems.

Remember, everything we experience is "modelled" in our brains. It's no surprise we invent thought models for things we are trying to understand that we don't directly perceive with our senses.

Modelling the world is how our brains interface/understand/react to the universe around us.

 

[KimB]

This is ridiculous, the cat is alive and dead at the same time? Now the theory might say whatever it wants to say, but we know from a fact that in this time and space the cat is either dead or alive. Just because a conscious mind doesn't know doesn't make it both.

How do we know? Granted, we never experience any such thing in the real world, but then we don't expect to given the properties of quantum mechanics, as whenever you have an interaction, the wave function collapses. And since you can't observe something without an interaction, you can never observe anything in a superposition of states.

Is it strange? Yes. Is it contrary to our naive expectations? Definitely. Does that make it wrong? Not in the least.

On a side note, how should science be seen?

It should be seen as the best method for finding an accurate description of reality that humanity has yet come across. As such, when the scientific community reaches consensus, you can be highly certain that they are correct.

Should you see it as models, and are the models then real? Are there actually real things we call quarks or strings that have properties like being a blue ball and build up the universe like lego bits? Although it's interesting that there are lego bits that can be built with.

Quarks we can be highly confident of. Strings we just don't know today, as there is as yet not even any potential experiment that has been devised that could determine whether or not they exist.

I think the proper response here is that you should listen to what the scientists say about a particular theory or model, being careful to avoid the crackpots, but always remain skeptical that you have understood correctly. It is, after all, often quite difficult to properly explain theories on a popular level so that they can actually be understood.

It's ridiculous to say that an photon can be both particle and waves.

No. All particles act as waves as well as particles. Just because something is outside of our normal experience doesn't mean it's wrong. We should not expect the world of the very small to behave the same as the medium-sized world which we can observe. Photons are real particles. We know they are real because of their effects.

 

[weaksauce]

You shouldn't quote Schrodinger's Cat unless you understand that it's a thought experiment, and was meant to disprove/poke holes in early quantum theory. It's not as simplistic as "it's dead and alive at the same time".

The whole the thought experiment is based on wether or not a certain radio active material radiates or not. According to it, it is both.

Remember, everything we experience is "modelled" in our brains. It's no surprise we invent thought models for things we are trying to understand that we don't directly perceive with our senses.

No, it is not all modelled unless you go and think about it. This table wasn't first of all a table before we made the sound "taaableee" and linked it to this shape and it wasn't any model before one started to legobitze it. I don't see any atoms. I can visualize a planetary system of balls, and some would argue that this visualization is correct.

Modelling the world is how our brains interface/understand/react to the universe around us.

Well the other approach is without the model and just the comprehension of effects and calculus. You don't need to think about balls.

It's still ridiculous how it is in popular science enforced on actually being balls.

 

[weaksauce]

How do we know? Granted, we never experience any such thing in the real world, but then we don't expect to given the properties of quantum mechanics, as whenever you have an interaction, the wave function collapses. And since you can't observe something without an interaction, you can never observe anything in a superposition of states.

Is it strange? Yes. Is it contrary to our naive expectations? Definitely. Does that make it wrong? Not in the least.

The theory is not about that the measurement disturbes the condition of the particle, the particle is created in the measurement. There's this whole segment of virtual particles etc... (which I don't think I've fully grasped but good luck on visualizing that one)

No. All particles act as waves as well as particles. Just because something is outside of our normal experience doesn't mean it's wrong. We should not expect the world of the very small to behave the same as the medium-sized world which we can observe. Photons are real particles. We know they are real because of their effects.

That's the thing, we only know the effects. We then make a model to describe the effects, ie the particle or the wave. But the model is not real and imo it shouldn't be dealt with at all, as it occludes the real thing.

 

[pocketmoon66]

I recommend the Atom mini-series recently shown here in the UK on BBC4, presented by Jim Al-Khalili.

http://www.al-khalili.co.uk/

 

[weaksauce]

Yeah, thats exactly what I watched before making this thread.

 

[KimB]

The theory is not about that the measurement disturbes the condition of the particle, the particle is created in the measurement. There's this whole segment of virtual particles etc... (which I don't think I've fully grasped but good luck on visualizing that one)

There is nothing here that makes this any different from the table in front of you. A photon can be said to be real in the exact same way that a table can be said to be real. The whole real vs. virtual thing is irrelevant here.

That's the thing, we only know the effects. We then make a model to describe the effects, ie the particle or the wave. But the model is not real and imo it shouldn't be dealt with at all, as it occludes the real thing.

The model should be considered to be a possibly inaccurate description of reality. Something that behaves like a photon really exists, though our theoretical concept of what a photon is is likely to be incomplete. The model doesn't exist, it is merely our description of something that does.

 

[Bigus Dickus]

A moving table has wave properties. Move it fast enough, and you might observe some of them.


As for the more probing questions, I still find David Deutsche's "Fabric of Reality" to have probably the most compelling "putting it all together" viewpoint of physics, cosmology, biology, and computational theory. I think some details of his thoughts may need to be tweaked a bit to reconcile better with the most recent research and understanding, but on the whole it gives as good an answer to some of these unanswerable questions as I've found.

 

[Fred]

Shrodingers* cat is already sort of a problem at the classical level (as far as intuition goes). Forget everything you know about quantum mechanics and Heisenbergs uncertainty principle, and just consider the following:

*Actually it was Einstein who first came up with the thought experiment, but whatever.

Imagine all particles in nature actually were perfect classical waves, not quantum mechanical waves, but pure classical waves (like pressure waves or ocean waves).

When the 'trigger' goes off, it unleashes a bullet that has some waveform. This waveform will interact with the cats waveform. Now freeze time, close to the point of impact (as yet to be determined what that means), and open the box. I ask you, at what point and with what criteria can you make a measurement that says the cat is 'alive' or 'dead'?

You could say, opt to bounce a light wave off the cat + bullet system and measure it. Light is also a wave here, and clearly it will also interact with the system (changing the nature of whats really there in some small but subtle way).

Worse, you will have a measurement uncertainty (experimentally), with the incident light wave that you measure. I claim (and can prove), that no matter what subjective criteria (something about the initial waveform) you state is aliveness or deadness, you can always shrink this criteria into the experimental uncertainty of what you eventually measure.

 

[Fred]

Now, what happens with quantum mechanics?

QM adds an extra layer to the problem in the following sense.

Imagine if I was god, and could measure the state of the cat + bullet system without altering it (by bouncing a photon off and measuring it in the previous example), or could measure the waveform of the photon perfectly. I could of course in that case, say something concrete about aliveness or deadness. Either the bullet went off, or it didn't.

QM makes this perfect measurement, fundamentally impossible -even in principle-

This is Heisenbergs uncertainty principle in its full glory, it is not something merely about *experimental* uncertainty, but rather something deep and profound about the actual state of matter and possible information about a system.

 

[Davros]

If your interested in string theory ect you should watch this
http://www.pbs.org/wgbh/nova/elegant/program.html

Quantum mechanics
Richard Feyman - The Douglas Robb Memorial Lectures
http://www.vega.org.uk/video/subseries/8

 

[Davros]

Ps: why is no one discussing Davros's Cat

Why did the cat cross the road ?

Now untill i deliver the punchline the joke is in a super critical state of being funny + not funny at exactly the same time + only when the punchline is delivered does it become one or the other

Quantum theory explained
And to think there are some b3d readers who doubt my genius

 

[RussSchultz]

That would assume that any subset of the 'why does the 'x' cross the road' jokes are funny.

Just with that lead in, I can unequivocably say "unfunny"


Though, to be honest, I laughed out loud when reading your comment.

 

[Davros]

So its unfunny yet you laughed out loud

see B3d readers a demonstration of Heisenbergs uncertainty principle before your very eyes

I should start a physics lecture tour or something....

 

[dizietsma]

.

If you try to visualize it....

No, you see that's the problem, trying to visualise it. Thinking in terms of everyday objects like small hard sphers or waves in a string, pond etc will not lead you to how it works, it will just confuse you.

I think you mentioned visulise about 3 times in your posts so I can tell why you are uncertain. Really the best way to approach it would be to just learn the mathematics and try and junk the "mindseye" approach.

 

[weaksauce]

No, you see that's the problem, trying to visualise it. Thinking in terms of everyday objects like small hard sphers or waves in a string, pond etc will not lead you to how it works, it will just confuse you.

I think you mentioned visulise about 3 times in your posts so I can tell why you are uncertain. Really the best way to approach it would be to just learn the mathematics and try and junk the "mindseye" approach.

That is what I have been saying the whole time.

 

[Fred]

Interesting new experiment + commentaries that shows the weirdness of it all:

http://scienceblogs.com/principles/2007/09/watching_wavefunctions_collaps.php