Quantum theory

[Pukko 0]

I went to a short orientation course at my local University based on quantum theory but with focus on the limits of knowledge and the uncertainty principle.... I took the course just for fun, and I had hardly heared the word quantum before, and ofcourse even less what it stands for.

Just as for most other people making first countact with quantum physics it turned parts of the world upside down. But there is one thing that plauges my brain and that I have not been able to figure out in various texts, so I thought some of you guys might know better

2 versions of my question:

 1- is there any particles at all, or is everything just waves?

 2- Is there any particles at all (particles with mass that themselves all move in waves), or is everything just probability-waves with a certain energy?

An explanation of the question:

As I have understood it, the scientists think that photons have no mass, and therefore cant be a particle. Now all bigger 'particles', like the proton, are made up of quarks and antiquarks. And its not until quite recently (if I recall right) someone could prove the existance of a quark at all since they always have to be part of a bigger particle.

So as far as I know noone can tell wether there really is any real 'materia' or 'particles', or if everything is just waves.

Do you know if there in quantum theory are any proof of 'real' subatomic particles (with mass "that you can take on"), or is it still open that everything can just be made up of waves, held together and combined by the "4 forces"?

[Ex-RoNiN 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Pukko @ Sep. 08 2002,14:28)</td></tr><tr><td id="QUOTE">2 versions of my question:

 1- is there any particles at all, or is everything just waves?

 2- Is there any particles at all (particles with mass that themselves all move in waves), or is everything just probability-waves with a certain energy?<span id='postcolor'>

This is easy: the particle-wave duality (discovered in the 30's or 60's, not sure which) clearly state that "particles" are both waves and "particles"

This is why Bohr's model of the atom is not considered "wrong", merely incomplete. Likewise, the electron-cloud model is not the whole story either.

The best thing is that Heisenberg's Uncertainty Principle allows you to measure a particle's position OR a particle's vector, but not both, which indicates that things aren't as clear cut as they seem.

One important experiment regarding the particle-wave duality was done when a scientist used an electron gun to fire it at a 2 slit apparatus, with both slits having a very narrow width. In the first minute, he would fire one electron at the left slit, in the next minute 1 electron at the other and he kept on going for quite some time. When he came back he didn't have the two slits as 2 dark spots on his photographic paper, but rather a continous spectrum of dark spots. This is how the theory of particle-wave duality came into being

EDIT: Here is a website to get you started: http://www.qmw.ac.uk/~zgap118/

[Pukko 0]

Yeah I know about that experiment (that there is a interference pattern corresponding to that of waves on the target) and the concept particle-wave duality, even if i might not have understood them correctly...

But this dont answer the question I thought of and probably failed to make clear so here is another one:

If one could freeze a real basic 'particle' (like photon or quark or even the electron (I read somewhere that it has no apparent internal structure) ) so that it has no velocity and is just static/fixed to one position in the universe (which I think is regarded as impossible), would there still be a particle there?

Or even this question:

Does anything really exists in i self, or is everything in the long run nothing but waves (that might appear as particles)?

[DarkLight 0]

Threads like this one make me very unhappy thinking about what i still need to learn in my school career

[Guest]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">If one could freeze a real basic 'particle' (like photon or quark or even the electron (I read somewhere that it has no apparent internal structure) ) so that it has no velocity and is just static/fixed to one position in the universe (which I think is regarded as impossible), would there still be a particle there?

Or even this question:

Does anything really exists in i self, or is everything in the long run nothing but waves (that might appear as particles)? <span id='postcolor'>

Ex-Ronin answered your question correctly. There are two proporties that coexist.

To take your case for example. If you would try to "freeze" a particle so that you got its position in the room zeroed down then you would have no clue of the mass and velocity of the particle (ie momentum).

There are two ways of looking at the wave proporty. One is that it is matter-waves, which means that the particle is "smudged" over the space that the wave occupies. The other view is through probability density waves. There the wave represent the probability density of the apperance of the particle. This two views are actually the same equation-wise. The frist one comes from de Broglie and the second one from Schrödinger.

[Ex-RoNiN 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Pukko @ Sep. 08 2002,14:55)</td></tr><tr><td id="QUOTE">Yeah I know about that experiment (that there is a interference pattern corresponding to that of waves on the target) and the concept particle-wave duality, even if i might not have understood them correctly...

But this dont answer the question I thought of and probably failed to make clear so here is another one:

If one could freeze a real basic 'particle' (like photon or quark or even the electron (I read somewhere that it has no apparent internal structure) ) so that it has no velocity and is just static/fixed to one position in the universe (which I think is regarded as impossible), would there still be a particle there?

Or even this question:

Does anything really exists in i self, or is everything in the long run nothing but waves (that might appear as particles)?<span id='postcolor'>

Heisenberg's Uncertainty Principle: You either know the position of a particle, but not its momentum, or you know its momentum but not its speed

[Pukko 0]

1:st I'm sorry Ex-ronin if I made it sound as if I dont appreciate your answer which indeed was correct to the my badly formulated question (but its not always easy to ask about these things)

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (denoir @ Sep. 08 2002,15:10)</td></tr><tr><td id="QUOTE">

To take your case for example. If you would try to "freeze" a particle so that you got its position in the room zeroed down then you would have no clue of the mass and velocity of the particle (ie momentum).

There are two ways of looking at the wave proporty. One is that it is matter-waves, which means that the particle is "smudged" over the space that the wave occupies. The other view is through probability density waves. There the wave represent the probability density of the apperance of the particle. This two views are actually the same equation-wise. The frist one comes from de Broglie and the second one from Schrödinger.<span id='postcolor'>

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Heisenberg's Uncertainty Principle: You either know the position of a particle, but not its momentum, or you know its momentum but not its speed <span id='postcolor'>

Yep, I know about that too (I'm sorry for not taking the time to find the correct concepts and 'primciple titles' for where I really stand), but I reserve myself for not understanding it ; the fact that one cannot measure both position and momentum, without 'destroying' the particle.

I have browsed some more on the webb (and at least temporary remembered some concepts again), and I found on the page you linked to Ex-ronin that the electron and even photon is really considered a particle, and the conclusion:

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">"we shall demonstrate that energy in the form of packets gives rise to our interpretation of particles, which cause some very interesting phenomena. Given the right circumstances, usually that they are moving, all particles can be considered to be waves. But, also that certain waves can be considered as particles."<span id='postcolor'>

But this particle-wave duality do not say that there really exists any particles in themselves, do it. Rather the other way; that, like the last part in the citation above, "certain waves can be considered as particles"..... And therefore back to my basic question:

Is there any any evidence of a 'physical', finite, concrete, particle that exists in it self, but that just moves in waves? Or is everything just 'empty' waves (it really is nothing more than just a wave pattern/movement) that gain energy and the appearence of paticles due to very high velocity and various other forces?

Or do this (also taken from Ex-ronins link) really prove that the electron really is a finite, concrete 'physical' particle in it self (even if it could be observed without velocity and wave motion) "that one could 'take on' ":

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">"The electron is clearly a particle as the experiments of J J Thomson show. He calculated that there was a clear e/m ratio and that the charge on any electron is 1.6E-19 Coulombs"<span id='postcolor'>

I'm not sure if I have been able to express myself clearly this time either, but basically: Does anything (subatomic 'particles' decayed to its smallest 'parts' ) really exists in it self according to quatum theory, or is everything just empty waves that might just appear (sometimes very temporary) as concrete finite particles under the right circunstances?

Thanks alot guys for making the effort to even understand what I'm asking, and giving your best answers possible to my badly formulated questions

[Ex-RoNiN 0]

I could be nasty and introduce the concept of Superstrings, which is a theory that states there are no waves or particles, but that what we conceive as waves and particles are just manifestations of multidimensional strings that span several dimensions, they just happen to look like particles and waves in our dimension

<span style='font-family:monotype corsiva'><span style='font-size:7.5pt;line-height:100%'>That is a different way of saying that I am not sure</span></span>

[Mister Frag 0]

Question asked and answered. Closing?

[Pukko 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Ex-RoNiN @ Sep. 08 2002,16:17)</td></tr><tr><td id="QUOTE">I could be nasty and introduce the concept of Superstrings, which is a theory that states there are no waves or particles, but that what we conceive as waves and particles are just manifestations of multidimensional strings that span several dimensions, they just happen to look like particles and waves in our dimension

<span style='font-family:monotype corsiva'><span style='font-size:7.5pt;line-height:100%'>That is a different way of saying that I am not sure</span></span> <span id='postcolor'>

Ok, sounds like I'm in to look at the concept of superstrings then, Thanks

Got any good links?

[Ex-RoNiN 0]

http://superstringtheory.com/

http://www.sukidog.com/jpierre/strings/

http://www.theory.caltech.edu/people/jhs/strings/

Should make for a very interesting afternoon read

Why oh why did I quit Physics

[advocatexxx 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Pukko @ Sep. 08 2002,08:28)</td></tr><tr><td id="QUOTE">2- Is there any particles at all (particles with mass that themselves all move in waves), or is everything just probability-waves with a certain energy?<span id='postcolor'>

Even the larger more massive particles protons let's say are somewhat difficult to locate precisely (err, the word I was looking for was "impossible").  In order for you to stabilize a proton (fully) you'd have to hover it in some sort of a magnetic field for once.  Then you'd have to make sure it's in a complete vacuum, one completely empty of electrons, etc. but that one proton.  Then you'd have to make sure no light/heat or any sort of radiation comes in contact with that proton, as that way you could reduce its temperature to absolute zero.  So to answer your question is it possible to actually localize a particle such as proton instead of just imagining it as a wave of probablity, well it is possibly to confine it, but here is what the trick is.  It's one thing confining a proton to be fully disconnected from any external influence and bringing its temperature down to absolute zero, and it's another thing to detect it in that state.  For any means of detection (as far as we know) would involve a direct contact with the proton.  Contact with a photon for example which would cause a slight energy-exchange and thus raise the temperature of the proton to above absolute zero causing it to vibrate.  This of course would prove to be the case as the magnetic field in which the proton is hovering in would definitely cause proton/photon interaction.

If the uncertainty principle has taught us anything it's that nothing can be observed without a direct interaction (thus disturbance).  Reminds me of a poem:

All things by immortal power,

Near or far,

Hiddenly,

To each other linked are.

That thou canst not stir a flower,

Without troubling of a star.

So to fully give you an answer:  Whenever we try to directly detect any of the elementary particles we also directly interact with them causing them to change their velocity/angular momentum.

Just think of them as "there", not "there exactly" : )

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">So as far as I know noone can tell wether there really is any real 'materia' or 'particles', or if everything is just waves.<span id='postcolor'>

Lol, it depends on your definitoin of "real", for if quantum mechanics has taught (me) anything, it's that the term "real" is quite pointless.  If sumpersymmetry does infact complete (or help to complete) the superstring theory (or M-theory), then it will no doubt become clear that whether we think of them as particles or waves really makes no difference.  The Standard Model of particle physics has dead-on proved itself time and time again to be exact to the ziltch (considering you don't take into account relativistic forces and relatioships).  Through the equations of the Standard Model one can conduct any set of calculations and not have to worry whether electron is a particle or a wave.  What matters are its properties (velocity, energy, spin, charge, etc.).

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Do you know if there in quantum theory are any proof of 'real' subatomic particles (with mass "that you can take on"), or is it still open that everything can just be made up of waves, held together and combined by the "4 forces"?<span id='postcolor'>

As I said, if Superstring/M-theory are complete they will most likely reveal that particles are no more than 1-dimensional strings (open, closed, etc.) which vibrate on different frequencies in a 11-dimensional universe (with the most recent theoretical calculations)

I shouldn't have to tell you that apart from experimental calculations and indirect detection methods, one cannot really take a photograph of an electron to prove its "real" existence.  For reasons which I'm sure you're aware of.

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Is there any any evidence of a 'physical', finite, concrete, particle that exists in it self<span id='postcolor'>

Slap yourslef in the face. I call that physical evidence, wouldn't you ?

[bn880 5]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE"> Through the equations of the Standard Model one can conduct any set of calculations and not have to worry whether electron is a particle or a wave. What matters are its properties (velocity, energy, spin, charge, etc.).<span id='postcolor'>

Yes but then basically by not having to worry we can't really progress.

Even if we are convinced of the above theories, they do not actually provide any new tool (usable equation- I know there are equations but...). Although the concepts may leed someone to a new understanding faster, with understanding an equation "reveals" itself.

Superstring theory, ok, but continuasly looking for smaller and smaller particles is very one dimensional thinking... even if you find the smallest, what do you really understand?

[advocatexxx 0]

Superstring theory does not aim to find smaller pieces of energy. It aims to unite what many theories have attempted over the past few decades - Relativity with Quantum Mechanics. One unified theory in which the laws of gravity, strong, weak and electromagnetic forces would finally make sense.

Supersymmetry argues that all of the 4 primary forces infact become one indistinguishable force at Planck-level scale. It's not driven by the constant search of yet smaller building blocks, but rather to gain a complete picture of our Universe.

[Pukko 0]

I've not started to look at the superstring concept yet, but i will at least browse through it tonight..

But I thought, after advocatexxx more philosophical post, that I would make my interests in quantum physics clear.

Apart from general interest in these facshinating concepts, my interest is more on a philosophical level (the course I took last spring was indeed at the Theoretical Philosophy department). I primary study behavioural science, right now with the focus on Social Psycology.

Since these kind of social sciencies always have to deal with what is a real objective 'world', and what is just subjective views/illusions (or the classical realism/idealism ontological questions) Quantum theory comes in here as very valuable contrast to common sence 'reality'. Indeed I have heard of some, probably psycological (since its so close to the individ), perspectives within the social sciencies that study humans from a, or at least with a big portion of, Quantum perspective - anyone heard of it?

So the very reason I started this thread was to come gain insight in this particle question enough to know if it would be a outright lie to say (in the discussion of what is real):

According to quantum theory nothing really exists in it self, everything is rather just waves of probability; that under the right circumstances form what we (humans) can interpret as real things/experiences

It might sound like (and may be) a sick kink to seek to refer to such things in social sciencies, but I think its non the less a vital cotrast to the social reality we see around us. A good example in a ontologigal text and discussion I took part in was about how the eyes via ...... (what ever they are called in english) collect 'light beams' and translate them to pictures. This is indeed on a deeper level (or at least a contrasting reality than the ordinary common sense reality) than the kind of 'he said a bad thing, so he is evil' discussions.

Therefore I think that, even just for myself, being aware of the 'as deep as one can get today' reality that quantum theory can give is really good. Not just to brag and 'eliminate' someone else in a discussion related to reality, but as a sound addition to the everyday, and scientific, conception of reality.

And since quantum physics is all about really abstract concepts, being able to reduce it to a concrete, and preferably containing the extreme basics of 'reality' (as we know it today), scentense is real hard. Such a scentense dont have to make much real sense to the common human being, but its invaluable to provoke humble approach to just 'reality'......

Do any of you care to try one (since I recon mine above is of moderate value at best)?

[bn880 5]

1--></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (advocatexxx @ Sep. 08 2002,131)</td></tr><tr><td id="QUOTE">Superstring theory does not aim to find smaller pieces of energy. It aims to unite what many theories have attempted over the past few decades - Relativity with Quantum Mechanics. One unified theory in which the laws of gravity, strong, weak and electromagnetic forces would finally make sense.

Supersymmetry argues that all of the 4 primary forces infact become one indistinguishable force at Planck-level scale. It's not driven by the constant search of yet smaller building blocks, but rather to gain a complete picture of our Universe.<span id='postcolor'>

Really, the vibrating strings with a definite size, what is that all about? I think that's what you want it to aim for, but maybe it's not really getting there. I really doubt this will explain those forces, we already have means of calculating them pretty well (not at all understanding), and that's where this appears to be building on.

What I'm saying is, if these vibrating strings are the understanding of those forces, then why isn't our understanding of them really any better.

EDIT: Maybe I'm also wondering why we are looking for proof before understanding... also I'm not saying this is not very important research.

[advocatexxx 0]

bn880 I'd love to provide you with a 100 paragraph post going into the details but I'm just so lazy to have to type all that only for 2-3 people on these forums. Maybe you should do more reading on Superstring/M-theory and Supersymmetry before determining their goals.

[bn880 5]

Maybe, and maybe not.

Since you are a hrdcore follower of this research, do you forsee a breakthrough from this, some time in the future?

EDIT: many topics are the concern of only 2-3 people... I have to say, what scientists claim their reserch is looking for is usually not what they actually discover. Just like US soldiers telling Afghans they are there to free them, is not the case.

[Guest]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Pukko @ Sep. 08 2002,16:11)</td></tr><tr><td id="QUOTE">Yep, I know about that too (I'm sorry for not taking the time to find the correct concepts and 'primciple titles' for where I really stand), but I reserve myself for not understanding it ; the fact that one cannot measure both position and momentum, without 'destroying' the particle.<span id='postcolor'>

It is not about destroying the particle. The uncertainty principle itself is very simple itself and you can easily understand it within concepts taken from classical theory.

The thing quantum mechanics basicaly introduces is that energy isn't continuous, but discrete and that there exists a minimal energy quantity (hence the name quantum mechanics).

The very simple explanation of the uncertainty principle is that when you try to measure something on that small scale, you will with your measurment intetrfere with energy of the same order of magnitude as the thing you are trying to measure. So you will disturb it.

Say that you are trying to measure the physical proporties of a roling ball. Your 'instrument' is a stick that you poke the ball with and then try to establish the mass, velocity and position of the ball by measuring the force that you get on the stick from the ball.

The quantum requirement is that you can only push your stick with a force of fixed strength or not to push at all. With normal classical mechanics, you will see that you cannot decide the position and the momentum more exact then the order of magnitude of the force that you applied on the ball with the stick. It is nothing strange here - when you poke the ball you interfere with its velocity and its position.

Ok, a short one on string theory. The problem with QM is that it has problems working with classical electrodynamics. According to Maxwell's equations an electron that travels induces a electromagnetical field (i.e radiates) and by that loses energy. According to Bohr's atomic model the electrons are orbiting around the nucleus in fixed orbitals. That kind of a model does not work with classical electrodynamical theroy, since the electrons are supposed are supposed to lose energy on the way and finally collapse into the nucleus.

The point with string theory is to get around that and also improve the very shady concept of wavepackets. The problems of string theory are however the ususual

1) Does not work with the theory of relativity.

2) Has yet to be confirmed by any empirical measurements.

[Pukko 0]

Now I have filled my brain with stuff from the superstringtheory.com that Ex-Ronin posted to satisfy my urge for anwers, at least temporary..

After traveling through the dimensions of superstring theory (probalby without understanding anything) I went a little further in the spacetime dimensions back to the cosmological concept of the big bang. There it seems like everything is supposed to have been developed from radiation (photons I recon) that later forms quarks and gluons. So therefore I gather (since photons, quarks and gluons probably is massless, or? ) that its likely that all 'particles' is just cooled-down high-energy radiation.

Ah, it doesn't really matters now... But if you would like to comment on my probably pathetic conclusion, I won't take any harm in knowing it...

BTW denoir. My expression " 'destroying' the particle" was just a bad choise of words; I rather meant it was 'destroyed from further measuring', or indeed (if I had found the word) disturbed.. its probably very hard or impossible to miss that part when one hear about it - just felt a little stupid when I read your explanation, but your example with the stick and ball was excellent!

[Ex-RoNiN 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Pukko @ Sep. 09 2002,03:05)</td></tr><tr><td id="QUOTE">. So therefore I gather (since photons, quarks and gluons probably is massless, or? ) that its likely that all 'particles' is just cooled-down high-energy radiation.<span id='postcolor'>

It was Einstein himself that once described matter as "frozen energy"

[Tex -USMC- 0]

I bet they dont have a quantum physics thread on the Americas Army forum

[bn880 5]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Tex [uSMC] @ Sep. 09 2002,08:17)</td></tr><tr><td id="QUOTE">I bet they dont have a quantum physics thread on the Americas Army forum<span id='postcolor'>

I bet they don't. I was just going to say to Pukko, do you think we are a bunch of physicists?

Ex: Frozen Energy, but not strings

As for observing frozen, or small energies, your only option is to see how much energy is emmited, so your apparatus can only absorb. If you send energy of any kind, Denoir already said it.

[Pukko 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (bn880 @ Sep. 09 2002,14:32)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Tex [uSMC] @ Sep. 09 2002,08:17)</td></tr><tr><td id="QUOTE">I bet they dont have a quantum physics thread on the Americas Army forum<span id='postcolor'>

 I bet they don't.  I was just going to say to Pukko, do you think we are a bunch of physicists?  <span id='postcolor'>

But bn, I thought you were that hairy guy on your avatar    

Seriously, I thought that I could get some good answers here - in differance from the AA forum, there are actually some brains around here - and I got them too, didn't I? Thanks guys (now I have to get back to my primary studies though)..

[Postduifje 0]

Whow, this is a tough thread, but I got thrue it. And it somwhat made sense...:)