MI collisions

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Collisions do take place on every scale. They are simply collisions produced by smaller scale forces, not by contact. I gave two examples.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Real collisions take place at every scale. But there is never any contact, nor is any ever needed.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> Quite frankly Tom - You're not making any sense, along with the two example you gave.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">We never need actual contact collisions because smaller-scale forces can always simulate contact collisions, and every scale has such forces acting. -|Tom|-<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
This is exactly the bone of contention. If the "appearance of contact" is the only "real" form of contact ... then ... you are simply describing, in a different way, standard model "fields" as the only causal connection between two bodies. [The "field" being an abstract, three dimensional layout of numbers which indicates how much a trajectory will change under given conditions]

If you wish to deal with "bullets" as the carriers of force ... you must deal with finite cross-sections for them to hit. And in order to make a cross-section (without fields) you must posit solid, impenetrable balls of some finite sizes such that, even though they are infinite, they sum to that finite cross-section ...

Your tactic is "tail chasing". I disagree with it and view it as a logical canard.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">And having a base particle or scale requires a miracle, whereas infinite divisibility does not. -|Tom|-<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Why is "one" a miracle ... but not "infinity", which, as you posit, sums to "one" ?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Skarp</i>
<br />You're not making any sense, along with the two example you gave.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Let's look at one of those examples: two galaxies colliding. Because galaxies are mostly empty space occupied by the occasional star, colliding galaxies rarely involve any real star collisions or contact. Yet each star of Galaxy A has close encounters with stars in Galaxy B that redirect its motion. In one simple case, each star of Galaxy A whips around a star in Galaxy B and is sent back in the direction it came from. So Galaxy A ends up retreating from Galaxy B following the collision, just as if there had been an elastic rebound.

Moreover, consider an observer on a much larger scale who is unable to see the individual stars but can only observe the bulk motion of galaxies. That observer will "see" an elastic rebound, and will describe the event as a "contact collision", even though nothing from either galaxy ever touched anything in the other galaxy.

If you tear down any mental blocks you may have built, this is a real scenario faced in galaxy dynamics, and is not that difficult to understand or appreciate. And it is a good analog for the kind of thing that can happen in any collision. "Contact" is a description used only by observers whose instruments are not good enough to see the actual details of the collision. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by EBTX</i>
<br />If the "appearance of contact" is the only "real" form of contact ... then ... you are simply describing, in a different way, standard model "fields" as the only causal connection between two bodies.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">To reiterate what I said above, "there is never any contact, nor is any ever needed." All "contacts" are appearances only for observers whose instruments are not good enough to see what is really happening.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">If you wish to deal with "bullets" as the carriers of force ... you must deal with finite cross-sections for them to hit.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Agreed except for the prejudicial choice of words. Replace "hit" with "be influenced by" and "bullets" with "comets" so their speeds are slow enough to be influenced by local forces.

Then every target has a finite cross-section representing the area within which it can influence the paths of comets attempting to pass by. And the influenced comets have their momentum redirected just as if they had contacted something.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">And in order to make a cross-section (without fields) ... [The "field" being an abstract, three dimensional layout of numbers which indicates how much a trajectory will change under given conditions]<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">My definition of a field is a medium influenced by a material body. With my definition, there are no cross-sections without fields. Your definition appears to be a mathematical one, not a physical one.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">[tvf]: And having a base particle or scale requires a miracle, whereas infinite divisibility does not.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Why is "one" a miracle ... but not "infinity", which, as you posit, sums to "one"?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I could not parse your sentence so that your question made sense to me. So I'll just offer a few general remarks.

An uncomposed particle cannot have elastic collisions for many reasons, the simplest of which is that elasticity is a property of bodies composed of constituents, wherein a collision causes those constituents to become compressed. Then forces of repulsion between constituents attempt to restore the original shape, which expels the momentum absorbed in the collision back in the direction it came from.

Just try to describe the physics of a collision between two uncomposed bodies, and you will see a host of unanswerable problems, where the only resort in physics is a miracle. Of course, in math, one never needs to address the details of interactions, and can simply write an equation showing the conservation of momentum.

So the issues here and their resolutions all lie in the physics, and not in the math. Thinking mathematically tends to obscure physical details, and is commonly done where we cannot observe those details. But one must always defer to the physical details to avoid inadvertently introducing miracles into any process -- a common logical error in mainstream physics today. -|Tom|-

Jim,

In another thread some have argued that direct contact never happens. Instead, they argue, every particle has this "field" doohickey associated with it. The field of one particle interacts with the field of the other particle, and the result is what looks like one of several types of contact. But no real contact occurs.

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The problem with this idea is NOT the concept of a field interaction substituting for actual contact.

Rather, the problem is that the fields in these "explanations" are visualized as non-material and monolithic (a single entity, not composed of smaller parts).

The equations that DESCRIBE the effects of these fields are imagined to be some sort of EXPLANATION of these fields, ... and for some reason the proponents of this notion think that no further explanatory effort needs to be expended.

Much like the experts that are always ready to claim "this is the bottom!".

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In MM (as you can plainly see from Dr. Van Flandern's example) -

* fields exist (for at least some particles)
* they interact with each other
* this interaction is responsible for for what appears at some scales to be an actual contact.
* * *
* but no actual contact occurs, nor is it needed.
* the fields of MM are very material, very real
* and not at all monothic - the fields of MM are ALWAYS built from smaller parts.
* and those smaller parts ... well, you know the drill by now.

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The "only" real difference is, the fields of MM have a reasonable explanation. A physical explanation. (I put the word only in quotes because this difference may look small at first glance, but it's not.)

IOW, the difference is MM both describes (math) AND explains (physics) what is going on.

The non-material field idea only describes it. Kind of like opening up a birthday present, and finding that the box is empty.

Regards,
LB

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Replace "hit" with "be influenced by" and "bullets" with "comets" so their speeds are slow enough to be influenced by local forces.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
But what does "influence" mean to you? To me it means affected by "fields". Does it mean to you ... affected by collisions which do not actually occur? Are you proffering a theory of "quasi-collision" ? ;o)

The entire disagreement here is basically the continuous vs the discontinuous. You do not accept the physicality of any type of continuous field. You require that it be possible to examine it and discover some sort of discreet constituents in order for it to be "real". To me, the difference between a continuous field and a set of discontinuous particles is the same as the difference between the real numbers and their subset, the integers.

Why is a great, big, continuous block of rubber with logitudinal and transverse waves in it less real than a bunch of floating, colliding bricks? I have no trouble at all accepting both as "real". Both are useful geometric constructs (useful in terms of "explanation").

Neither appears even slightly "miraculous" to me.