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#### Probability and Quantum Theory

May 16, 2013 at 8:01 pm

So I just read a really neat article in Scientific American (an amazing magazine everyone should get) about a reformulation of what the wave function means in quantum mechanics. Its interesting both from a physics standpoint and from a philosophical standpoint, as in many ways its is simply a philosophical shift. Its a little complicated so I'll try to break it down, starting with a brief quantum theory overview for those who don't know about it.

Quantum theory is a wildly successful theory regarding the behavior of matter, in particular on the smallest scales. Together with relativity it is one of the most successful theories ever, accounting flawlessly for all sorts of physical results. Its also very, very weird with a lot of paradoxes. These pardadoxes are built around the wave function - a function that describes the state and behavior of a given particle. The result of the evaluation of a particle's wave function gives you the probability that the particle will have a particular characteristic (nothing in quantum mechanics is 100% accurate). In other words, it gives you a probability distribution.

According to the standard interpretation of quantum mechanics the wave function is real. Before a particle is observed it exists in a superposition of multiple states. Upon being observed the wave function "collapses" into one state (this is called the Copenhagen interpretation). To explain I'll give the common example, Schroedinger's cat. Keep in mind that quantum mechanics doesn't predict this sort of stuff really happening to large objects like cats - it only happens on a small scale.

Anyway, the basic idea is you have a cat sealed in a box with a vial of poison that will break within an hour with a 50/50 chance based on a quantum event. Before you look in the box after an hour has passed the quantum trigger, the vial, and the cat are all in a superposition of two states. In particular, the cat is both alive and dead at the same time until you open the box, at which case the wave function collapses and you are left with either a dead or alive cat.

That's the typical interpretation, but I just read about a new one, where the wave function doesn't really exist - rather it is only a personal mental probability calculation. This is based off of a different, subjective kind of probability, called Bayesian probability, where quantitative statistical data is combined with subjectve intuition to determine the probability of an occurance.

This type of probability is often shunned by scientists, who disregard subjectivity. However, unlike purely statistical probability, this personal value judgment of sorts can resolve the strangeness of quantum mechanics.

As an example of the difference, say that you know that one person has one the lottery every week for 10 years. Based on statistical probability you would still enter, as previous statistical events should have know bearing on future independent ones. However, this seems wrong, something a Bayesian probability would take into account.

This applies to quantum mechanics in that the wave function is now interpreted as just a measurement of the observer's mental state rather than physical reality. The cat is alive either alive or dead, but you don't know until you make the observation. The probabilities are all in your head.

This isn't just subjective mumbo-jumbo though. Using Bayesian statistics one can derive a precise quantum mechanical equation that tells an observer how to calculate their beliefs about a quantum system.

An interesting thing about this method of thought is that until an experiment is performed its outcome does not exist. For example an electron does not have a speed or position until it is measured.

I know that was long winded, but does anyone have any comments on that view of reality? Or on statistical vs. Bayesian probability? Or any questions about quantum physics?

half.note replied...
May 16, 2013 at 8:09 pm

I wondered when this day would come. XD

Anyways, don't really have time to read through everything.

I just wanna ask, have you ever read any Miles Mathis? His theories aren't widely accepted, but my dad thinks he's brilliant and that his stuff will eventually catch on. I've been meaning to read some of his articles myself, but haven't had the time. Maybe you should check him out.

God bless. ♥

Quantum1.0 replied...
May 16, 2013 at 8:21 pm

Half.note: Well I just looked him up and I admit I'm very skeptical - he's claiming a bunch of algebraic errors in relativity which considering relativity has been taught, been learned, and been tested for a century and has met all experimental data I am extremely doubtful that these errors exist as relativity has been examined by literally thousands of physicists since Einstein.

That said I'll read some more and see what he has to say...maybe I'll make a thread on it.

Quantum1.0 replied...
May 16, 2013 at 8:31 pm

Yeah...he seems like a bit of an egotistical guy who just wants to get attention...see this:

ht tp:/ /milesmathis.c om/david.h tml

On the other hand I will try to keep an open mind and actually read through his reasoning. I'll keep you posted.

Quantum1.0 replied...
May 16, 2013 at 8:33 pm

As an example he wrote this in reply to someone criticizing his work:

Glad to know those at UCDavis are reading my papers. You might want to read a little closer though, since you don't seem to be getting it. Thanks for writing and let me know when you start to understand physics. If you took your eyes off your diploma every once in a while, it might help. By the way, the proper English is "lack of a response." "None response" just proves to me I am dealing with a failed product of our educational system, which obviously reaches all the way up to the university level. Good luck with your continued coursework. PS Keep writing if you want to keep losing this exchange. It is up to you. I am always amazed when people like you are deluded enough to email me with your little slurs. You don't seem to realize when you're in over your head. You were in over your head the moment you clicked on my website.

First of all - don't complain about slurs when that is all you're doing. And second this guy understands physics - he is a physicist!

Quantum1.0 replied...
May 16, 2013 at 8:35 pm

It should be an interesting read though if just for understanding some oppposing views. Thanks, Half.note!

Quantum1.0 replied...
May 16, 2013 at 8:45 pm

All right. I've decided I don't believe anything this guy says. He says he's better at algebra than Einstein, but he proposes this equation for a particle being accelerated at high velocity in a gravitational field:
vf = v0 + 2v02t.
To understand why this is wrong you don't need to know any physics at all - just units. In particular velocity is in the units of m/s and time is in the units of s.

So doing dimensional analysis we have:

m/s = m/s + (m/s)^2(s)
m/s = m/s + m^2/s

which is clearly wrong as you cannot add m/s to m^2/s.

(^ denotes a superscript so m^2 means meters squared)

stuntddude replied...
May 16, 2013 at 9:53 pm

I don't claim to be any kind of physicist, so keep in mind I may be full of BS, but there's something you said that I have a bit of beef with.

"The result of the evaluation of a particle's wave function gives you the probability that the particle will have a particular characteristic (nothing in quantum mechanics is 100% accurate). In other words, it gives you a probability distribution."

From my understanding of quantum mechanics, I don't think this is quite how it works. The movement of particles isn't really random in that sense -- Schrodinger's wave function is a purely deterministic equation. The problem isn't with uncertainty in the equation, but with uncertainty in the measurements. Because of the uncertainty principle, the more acurately you measure a particle's position, the less accurately you can measure its velocity, and vice versa. Even if the equation turns out to perfectly describe the underlying law and it is deterministic, we can only ever plug in inaccurate or incomplete data, so for any given particle there's no way to know. Which is very depressing now that I think about it.

One objection to that is that, if the universe really did begin in a uniform state the way it seems like it did, how would a universal, deterministic law produce differences and fluctuations throughout? I don't pretend to know the answer. In fact, I have no clue.

Another thing I'm a lot less sure about is the idea that the wave function doesn't really describe the motion of the particles, but that there really are literal waves (in fields, like how we understand the electromagnetic field), and that particles simply emerge from the globbiness that tends to occur when a system capable of observation interferes.

Or I could be full of BS. I dunno.

P.S. WOW, that guy really is egotistical and melodramatic! I know this is unscientific of me, but I honestly wouldn't trust what he's saying just based on that. I've personally never met anyone with that kind of attitude who had anything very worthwhile to say. Usually that's a sign of insecurity more than anything else.

Quantum1.0 replied...
May 16, 2013 at 10:19 pm

stuntdude: You're 100% correct. That's what I meant but you explained it much more clearly. Thanks!

stuntddude replied...
May 16, 2013 at 10:35 pm

Me explaining something more clearly than someone else? That's a first xD

Imaginedangerous replied...
May 16, 2013 at 11:31 pm

Wow... I just read some of his stuff...
Apparently because you can put draw a point on a graph, and Cartesian graphs are two-dimsenional, all points are two-dimsenional. Also because a mathematical graph is not part of the real world, a mathematical graph cannot be used to model the real world. Thus Calculus as a whole is invalid.

Which means I just wasted an entire year on homework and 89 bucks on an AP test. (runs off to a corner to cry)

(then makes sure that everyone in the proverbial room is aware of the SARCASM)

Quantum1.0 replied...
May 16, 2013 at 11:45 pm

Imaginedangerous: Yeah. Who'd have that all the great minds of history and everyone who has studied them has been wrong up until now - bummer huh? (more sarcasm)

Quantum1.0 replied...
May 16, 2013 at 11:46 pm

So what do y'all think about the philosophy behind Batesian probability?

Quantum1.0 replied...
May 16, 2013 at 11:50 pm

*Bayesian (batesian is a type of mimcry in biology)

May 16, 2013 at 11:58 pm

O.O I read the WHOLE thing. I'm so proud of myself. Now I'm just disappointed I don't know enough (and didn't understand enough) to join the discussion XD I'm only in hon chem 1 ......takin IB chem next yr tho, I like it XD anywho, carry on smart peoplez

Quantum1.0 replied...
May 17, 2013 at 12:00 am

Jade.I.Am: Comgrats on getting through my novel length post. Feel free to ask some clarifying questions. There's nothing I love more than talking about physics, so it won't bother me at all.

half.note replied...
May 17, 2013 at 12:02 am

Woah, was not expecting these responses.

Honestly, I've never read much of Miles Mathis' stuff (except for a couple paragraphs over my dad's shoulder).

I know he's pretty out there, but my dad thinks he's a genius. And considering my dad is a genius, I trusted his opinion...

I don't know, I'll definitely have to read some of his articles when I have the time.

As for Miles Mathis being egotistical, perhaps he is. :P

I mean, you don't have to be perfect to be right. His personal flaws should not affect the validity of his science (which I'm not suggesting you guys are doing, I'm just giving this as a general rule of thumb).

As well, maybe his "egotistical" remarks just came off that way because he was tired of the same arguments over and over.

I mean, my dad has emailed and talked with Miles Mathis before, and he never thought he was egotistical.

Anyways, I'm not trying to defend him... I honestly just don't know enough about the guy.

Anyways, I'm no scientist, so I think I'll back myself out of this one.

God bless. ♥

Quantum1.0 replied...
May 17, 2013 at 12:10 am

Hald.note:  Well I won't say that his tone (or his science) appealed to me, but I didn't mean to offend you in any way. I may not agree with him on most things, but he is right that physics doesn't have much room for dissenters right now (for example everyone is involved in string theory, which is an awesome, but probably dead end of a scientific theory). In that sense, its good that he's trying to bring some new ideas.

I'm sure your Dad knows what he's talking about as well. Perhaps Mathis is one of those people who is better one on one in terms of communicating nicely (the internet is a breeding ground for poor/rude communication).

Anyway, you should give his stuff a read too. Hope I didn't offend you - I admit I got a little rude their myself - it was just really irritating me for some reason. (I'll blame it on the fact I'm a redhead with a fiery temper :) )