Question about Quantum Mechanics
 

I love this stuff, but I'm still trying to make sense of it all.

If everything is so random and chaotic at the Quantum level and we are introduced to such ideas like there are infinite simultaneous instances of our life at any given time... like right now, the world could be ending, a tree could be floating through my office, or a carrot wearing a cowboy hat could be riding a bike up my wall, etc..

If everything is so random and chaotic at that level, then why is it our reality and perception appear to only pick out those things that appear to be "in order"? I guess I should rephrase it... why am I only experiencing THIS layer of reality as opposed to the other wacky/crazy ones? In order for Quantum Mechanics to be correct in stating that there are infinite instances/dimensions of our life, wouldn't our consciousness knowingly have to have some part in them?

Ask yourself this.

Who is to say there is not someone in another dimension, who thinks someone pushing buttons with fingers in order to communicate is the most rediculous thing he has ever heard of....it all comes down to perception.

Stompy, the reason you and I see things "normally" is because all of the abnormal things cancel each other out.

For instance one of the first things a high school phsics student learns about optics is that when a light beam hits a mirror, it is reflected off in such a way that the angle of incidence is equal to the angle of reflection.

[IMG]http://groups.msn.com/_Secure/0RgDyAi0VnerMKybe98n0lP9dSynV71Qvj9meDax4TAPHTKDvhXHlBNka8vleyKyAX2kbxhj6L8jNhziszbZjycaE!EZNcX8XzM*hkOSYfHs/qm10.gif?dc=4675467795118108168[/IMG]

What QM tells us is that the photon takes every path at once.


http://groups.msn.com/_Secure/0RQDdA...67795193715499

In the second part of this image, we can see the time taken for each of the routes A - M. Each "sub-route" has an "arrow" associated with it. To find work out the "arrow" for the route as a whole we simply add up the arrows of the "sub-routes" like you would vectors. (by lining them all up head-to-tail). You can see the result in the third part of the image. The long black line is the "arrow" for the route as a whole. If you look closely you will realise that A, B, C and D effectively cancel each other out, as fo J, K, L and M. The bulk of the arrow is made up from the contributions of F, G, H and I. As you can see from the first part of the image, this represents the "sub-route" of refelecting in the manner as predicted by classical physics.

So all of the "crazy" sub-routes cancel each other out, but the "normal" win out, and so we get the observations as made in classical physics.


All of these diagrams have been taken from Quantum-Electrodynamics by Richard Feynman. This is a very accesible account of quantum mechanics, and I highly reccomend it. It will explain what all these "arrows" mean!!

If the lottery really is random and any combination of numbers can come up, why do we never see 1, 2, 3, 4, 5, 6?

The answer is that for every combination that can come up and make us go 'hmm, that's wierd' there are a million more that won't make us bat an eyelid. So the overwhelming probability is that any given observer will exist in one of the far more infinite number of mundane universes, rather than one of the bizzare ones.

The more bizzare you get, the fewer universes there are like that. After all things only get to be bizzare by not happening very often.

There may be n universes where a carrot in a cowboy hat rides its bike up a wall somewhwere at some point in that universe's lifetime, but the chances of any given person even existing at the time it happens, let alone being anywhere near it are insignificant.

If you want to find a universe where there are loads of crazy things happen (so you can improve your chances of seeing something crazy), your chance of being in one are even more remote, because there are only n/loads of those (or perhaps n/(e^loads) I can't say exactly.

The other thing is that wierd stuff does happen. Take the big bang, or a big rock being thrown out from a boiling mass of gas, then cooling in such a way that parts of its surface begin to form into shapes that can reproduce themselves, respond to stimuli and eventually start making observations, or water falling out of the sky, or big rivers of boiling granite emerging from the Earth. It's just that once something wierd has happened, it becomes normal.

stompy, i don't think you quite understand quantum mechanics...?

not even sure where to start. quantum physics is based on a single wave equation that just happens to predict the behavior of small particles and small amounts of energy. based on that equation, there are two basic conclusions that can be 'easily' grasped:

uncertainty principle: there is a limit to the precision with which both the position and the velocity of an object can be measured simultaneously. the limit is pretty insignificant when you're talking about large objects, and becomes more and more significant the smaller you get.

wave/particle duality: a 'particle' is something that goes from point a to point b when you push it in that direction. a 'wave' is a pulse of energy that travels through a medium, spreading out as it travels and amplifying/nullifying at certain points when other waves are interfering. it turns out that all objects, including photons of light, behave as particles in certain situations and as waves in others. there's no really good intuitive explanation for this--it's just the way things are. related to this is the fact that you can't build a 100% solid wall to capture something. The particle can 'distribute' itself partly through the wall, even tunneling out past the wall is some circumstances. the effect, again, is much greater for small objects.

stompy, i'm not sure how you're getting this stuff about multiple dimensions and trees floating through your office from this. but maybe you know something i don't--it's been a few years since i took quantum physics...

csfilm: thanks for the diagram--didn't quite follow the logic of the 'subroutes', but it makes me want to check out the feynman book.

Deffinately do! It's very short (just over 150 pages) and very accesible (get this; not a single equation is sight!).
Also Feynman doesn't go and waffle on about the "wackiness" of it all. He doesn't go in for any cheap philosophical drivel, just the facts!

Stompy: Sounds like everyone has pretty much answered your question. In summary, while everything is possible with quantum dynamics, it (it being a cowboy-carrot riding up your wall or whatever) is very very very (x10^very large number) improbable (as John Henry illustrated). And as CSflim demonstrated, most of quantum mechanics' weirdness and wakiness is elliminated on the every-day observable level by cancelation and other quantum mechanical effects.

The only thing I really have to add is there are indeed theories involving infinite universes with every possible universe (i.e. carrot cowboys) represented. However, it is only a theory and isn't one that could be readily tested. And as John Henry pointed out the odds of exisiting in one of these universes would be very tiny. So, I wouldn't worry about those cowboy carrots too much.

CSflim: What is wrong with waffling about the "wackiness" of it all? Quantum Mechanics is very weird and its equations allow for some odd-ball effects to happen.

For anyone interested in learning of the wackiness of all the modern-physics theories, I would recommend reading either book by Brian Greene. He just recengly released one, "The Fabric of the Cosmos" and I am knee-deep in it. It has been a few years since I read his "the Elegant Universe", and I don't really remember what is the difference between them. Anybody read these two books and can help me remember why anyone should read "the elegant Universe" as opposed to just getting a more or less updated version of the same thing called "The Fabric of the Cosmos"?

Yes, I agree. But there is a time and a place. Also many authors of popularisations fall into the trap of getting all mystical, and then leave the actual explaining far far behind.
If you want to get an actual understanding of what quantum mechanics is about I recomend Feynman. If you want to wax philosophical on the possible existence of parallel univeres where anything and everything can happen, then look elsewhere. That is all that I meant.

I haven't read either of them (but I certainly plan to), but as far as I know the Elegant Universe is a much harder book to read, and goes into much more depth, where as Fabric of the Cosmos is much more accessible.

Thanks for the replies.

Still kinda hard to grasp, but I think I understand it a bit better :)

I have the Elegant Universe and Universe in a Nutshell that I'm currently going through. Very interesting reads.

Mystic QM:

You can predict the position of a particle by pretending it takes every route, and adding up the probabilities.

This, together with Infinite Dimensional Hilbert Space operators being interpritated "literally", leads to people believing stuff like The Many Worlds Interpritation of Quantum Mechanics.

i know this was braught up earlyer but what is the true meaning of wackyness or bazaar its just perception so this universe demnision could be the most bazaar of them all its just were here and that were used to it but the other ones could be normal but bazaar to us?

i'm with cs about waffly physics books--people often read these non-technical physics books (which have a great gee-whiz factor) and then come up with all sorts of ideas of how that affects or supports their philosophy of life, understanding only the gee-whiz example, and not the general principle behind it. for example, there are plenty of people who read somewhere that 'entropy always increases' and are now convinced that something as orderly as a human being could not possibly have been created without interference from God. but the actual 2nd law of thermodynamics is much more mundane than you'd understand from the three words 'entropy always increases'--it refers to a very specific set of conditions that have to apply. i think that's the danger of some of those non-technical physics books--it makes people feel like they understand something that they don't.

I'll admit, some of the bizarre in-depth aspects of QM is definitely way over my head.

Some things I won't grasp at first, but I have some friends who are deep into this stuff, and they'll explain it differently and it'll "click".

The rest of the more 'basic' stuff I can grasp and it certainly helps give me a different view on things.

Stompy, know alot about any really complex things? Programming, a Religion, anything?

The things you learn from just skimming the surface of a complex subject are quite often nearly completely unrelated to the subject. They are just illusions, reflections of the soul of the seeker.

Be careful about basing any beliefs off something you don't understand.

Totally.

Proof of Creationism #2,347:
1. If you place a hot thing beside a cold thing, the heat will flow from the hot one into the cold one and not vice-versa.
2. Therefore evolution is false.

:lol:

Very practical viewpoint. Though, don't let it prevent you from wanting to learn more. The effect these kinds of books have sometimes is that it can get someone interested enough to dig deeper.

I'm a software developer and I have found that what separates a good developer from a bad developer is that a good developer never believes he's a good developer. He KNOWS there is always something else to learn, some better way to do what he wants to do, and there is always someone else who understands or knows more than he does. Not to mention that the whole foundation for your understanding of how to do what you do and how you think is likely to change in within the timeline of when you actually are a developer.

Take a person who was born in 1960 and became a software developer out of college. Say that person never evolved past what they learned in their first few years of employment. These people still exist today (not many of them still have jobs doing programming though) and I've worked with them. They can write some mean assembly language or mainframe code. However, 5 minutes into a discussion on object modeling, data normalization, web services, multi-threading, encapsulation, etc.. etc.. etc.. they are so glazed over you might as well be talking to the floor.

Of course, I can remember a time not so long ago (10 years) where I didn't know how to "copy" and "paste" or create a folder in a computer. I also remember my uncle describing Email to me and I actually remember thinking "how could he send paper through the phone line".

My point : intrigue leads to research which leads to knowledge.

All great replies, but for me they all appear to "miss the forest for the trees". A couple of replies related to our 'perception' of reality - I'd like to offer a slightly more specific version: Our ability to "measure" reality. The perception of chaos at the quantum level arises from the peculiarity that we can seem to CHANGE quantum reality simply by measuring something. Therefore, we can nearly prove or disprove ANYTHING simply by devising a means to measure a particular state of a particle. Because we're not accustomed to this it seems quite chaotic.

In order to perceive the tree floating though your office, you need to devise a way to measure it. Its very tempting to rely on your five human senses to discount this as absuridity, isn't it? I can't SEE the tree floating through my office, so its not there...I can't TOUCH the tree, so obviously it isn't there...etc. Yet you've never seen a muon, a quark, or any other quantum particle...

This is where it gets even more obscure for me...we perceive quantum particles based on the effect they have on other particles or thier surroundings...so a tree floating though your office SHOULD knock the pictures off of your desk and break your lamp - or maybe it shouldn't...maybe its a small tree, maybe its trajectory didn't pass through any other objects, maybe its existence wasn't long enough to touch any other object.

My point is - Anything your mind can conceive IS reality. You doubt that because you cannot PROVE that by measurement. In the "elementary realm" this ability becomes much more pronounced, that's all.

Sorry if there are no *real* scientific answers here; this is just my perception of the way things are...

Cute, but not true. Just becuase measuring changes something doesn't mean we can change something in an arbitrary way by measuring it. Your postulates do not provide sufficient evidence for your conclusion.

Because we evolved at a scale large enough that Quantum 'wierdness' is mostly non-apparent. The 'normal' wierd stuff (like gravity, electricity, light, etc) we are used to, and don't consider wierd. The 'wierd' stuff we consider wierd is the wierd stuff that doesn't often show up at the scale we live at.

No, many interpritations of QM say that our 'consciousness' doesn't know and can't directly know anything about the 'realities' that aren't 'close' to 'our universe'. (sigh, too many ''s)

The multi-universe interpritation of QM seems to imply that most of those universes are orthogonal to ours. That's a technical mathematical term. In the QM interpritation, it basically corresponds to 'out of reach, can no longer affect us or be affected by us'.

That is consistent with QM, but it isn't nessicary to explain QM.

Then again, the 'fact' we are brains sitting in a jar in some alien kid's bedroom is consistent with QM. Consistency is not all it is cracked up to be, when you don't use something like Occam's Razor to shave off the junk.

that's a great point. i was thinking about it and realized that it can be something very simple...

example: to me, the numbers 3 21 81 are my birthday... to anyone else, it would be completely random and meaningless.

very cool thread.

From what I've heard, the sub-atomic particles only appear to be
random, which is why many phycists love the string theorems, it
would put the so called randomness into place.

Besides, I believe that the sub-atomic world and the larger
universe in general are kept by two different sets of rules, as
neither work on the other outside certain parameters (at least
as far as I remember). The "randomness" of the particles really
works to keep what we're doing in certain set boundaries, but
to also give each thing the particles make up a bit of randomness
that's so small it's barely measureable (such as the dripping of
a faucet, or "precise" machine movements).

And on a side-note, just from glancing around, I think the
multi-verse is a load of BS by guys who really can't figure out
any other way why the stuff works. Alot of points may be
valid, but not sound. Or, in terms of lack of knowledge, a point
can be very sound, but because of interpretations, wrongly
held concepts, etc could throw off the theory. I believe that
if there were, we probably would have stumbled onto it by
now. (See Asimov's, "The Gods Themselves")

Perhaps you'd like to elaborate on the third law of QP then...?

I like to interpret it as Stompy did in another post: "The intent of the observer affects the object observed".

The problem was with the use of the term "anything".

This means he was saying something more along the lines of ""The intent of the observer affects in an arbitrary and unbounded way the object observed".

Well put.

If you look at things in terms of numbers depending on how concrete the laws of physics are and to what extent every possible outcome can be possible by simply applying different numbers to different properties on the micro scale. Considering the amount of different mathematical combinations is infinite so are the possibilities of such a hypothetical existance. Ofcourse this is assuming that the laws that govern our world don't neccasarily apply to any other "universe". If other universes exist. Problem is we don't have enough concrete proof to hypothesize on so interpratation of quantum theory/quantum mechanics varies widely.