by **Good Elf** » Sun Oct 31, 2010 3:51 am

Hi Vern and Farsight,

[quote="Farsight"]Are the forces mediated by exchange of particles? No.

Is the idea of superposition valid? Yes.

I think it depends what you call "particles". The idea of particles "suggests strongly" the existence of tiny little "billiard ball"

objects that interact like "billiard balls" and bounce off each other and appear to have strongly defined boundaries and hard surfaces. In that sense if you consider sub-atomic particles to be like that then "yes" there are some ways to understand the interaction as "particles". Feynman Diagrams exemplify this notion as "interactions" operating over time at particular points in space. As an example the higher the interaction energy the more "particles" behave like that.... that is as point particles. The "problem comes" at really really low energy where the particle interact as waves and as they are fundamentally waves they are very "non-local"... this means that they exist in a diffuse distributed sense and their position depends on where the measuring instrument is located. When we measure a quantum object we do not measure part of it we measure the whole of it or not alt all. It happens that the exchange of energy is "packetized". You can only exchange energy as a whole "packet" not say for instance as half a "packet". Once you have that packet you can open it and redistribute the energy and so on. When we measure something that is usually where we believe it to be. For instance the position of a balloon is not a single point in space but I can use a pin to "detect" the balloon and ***** it anywhere on its extended surface. An instrument that uses this method to measure where the balloon is has some unique properties...

1. The balloon's position is where you ***** it and any number of "non-local" places would have "detected" the balloon at this same time

2. The balloons energy is released as a single event and is quantized

3. The balloon cannot usually be restored to the before the "***** condition"

4. The measuring instrument measures the position and energy of the balloon with some indeterminacy which is more or less irreducible because you can only ***** this balloon thing once.

In some ways quantum events and uncertainty at low energy reflect these general ideas we see with the analogy of a balloon. One other concept is an actual measurement disturbs what is being measured because the transfer of energy or momentum reacts on the instrument that is used to measure this event. To be able to measure tiny events the instrument must be responsive to accept the transfer of energy and momentum so it "kicks back" on the measurement system scattering the phenomenon. This results in a position and momentum (or energy) uncertainty.

The more accurately we want to measure one attribute the less accurately the other attribute is measured. This is called "orthogonality". We can know the position of an event with high precision but this affects the energy of the interaction.... In high energy physics they are only interested in the position of events not their exact energy or momentum as quanta. That is why they are called "atom smashers". In quantum physics we want to try and know both their position and momentum and the properties become fuzzy when we try to disturb the state as minimally as possible since a quantum state can only be measured once. Actually there are some recently discovered subtle exceptions... but do not worry about that for now.

"Superposition" is a valid concept since the fundamental "particles" we are speaking about are "fundamentally" waves. Any number of frequencies are required to "localize" a particle. If you think of a sine wave as the basic idea of a wave then it has an infinite extent because the mathematical function "extends" from +∞ to -∞. To reduce the "size or extent" of this infinitely long wave. We need to add in a number of truncation functions on of them. An example is the boxcar function and it is this...

The left hand function is the boxcar which is in the time (or spatial) domain and is like a hammer blow striking a nail (an impulse or spatial particle) but the right hand function is the transform of this function in the frequency domain (or spatial frequency domain... like matter waves) and you can see it has a lot of internal frequencies to make the "clean" impulse on the right. Please note this is not symmetrical above and below the horizontal axis. Alternatively the right hand function can be considered as an "origin" as the time domain function (the inverse) this is often called a "packet"... a damped oscillation and the left hand diagram describes the frequency distribution of this function as the sum of a narrow band of frequencies around the origin. I may add or subtract frequencies to change the shape of the wavelet but what it is saying is that any shaped function is internally composed of a sum of internal frequencies which sum th the final figure. The boxcar function is one dimensional function a three dimensional function that has the same response in three dimensions as a solid sphere... the ideal particle. This theory is called

Fourier Theory and applies everywhere even in quantum physics. Particle physics makes the global assumption that "particles" have wavelet compilations that make all particles behave like the

boxcar function while wave theory at low energy makes all particle behave like waves and look like wave packets composed of a

sinc function like on the right. In actual fact everything ultimately is composed of waves and "hardness" of a particle depends on the high frequency content of the wavelet... the higher the internal frequency the harder the particle. At low energy particles are 'softer"... if this word can be used and they interact like "wiggledly wobbley things". They then interfere with each other and with things ... like for instance "Young's double slit".... the distributed waves can pass through both slits at once whereas a "particle" is forced to pass through one slit at a time... the idea of particles is incompatible with waves in the low energy region. But still remember that the quantum is the minimum "packet" of energy that is able to be interchanged... while passing through a number of slits it either gives up all of it's energy or none at all.

If you consider everything as waves then particles are one extreme of high energy interactions of wave packets. People like the idea of particles as little balls ... that is the real problem... this preference for regarding "matter" as being composed of stuff with ponderable and visible "mass"... actually that aspect of "reality" is more to do about electromagnetism than it is about mass.

Remember this is kept "really simple" so the idea is understood. Naturally there is a lot of added complexity and this theory is called "non-classical" by convention... being that quanta do not behave like "billiard balls".

Cheers