> Physics is about measurements.
> Explain how the distance between the particles is measured, WITHOUT
> introducing any more particles (or objects, such as fields) into the
> universe. No photons; those are particles, too! No clocks; those
> contain _lots_ of particles! No meter-sticks; those contain lots of
> particles, too!
Perhaps I should not claim the particle to be an observer.
It is an experiencer. It experiences this angle by definition.
It is a suppositional argument and is not critical to the problem.
That is the open part of the problem.
The thing I'm trying to focus on is whether or not it is valid that two
particles have a 1D solution.
> This is not a trivial, irrelevant question. Go back and look at the
> beginning of Einstein's 1905 Electrodynamics paper. What's he talk
> about first? He talks about _HOW_ you make measurements, _HOW_
> velocity, time, and distance can be measured, because without
> specifying such things you don't have anything "physical" to talk
> about.
I hope not any more. But if you think it is ill defined still perhaps
we could work on some more of the basics. For example the proposition
holds that spacetime exists. This implies a 3D space. From one
particles position we simply choose a unit vector in a random direction
and call that the "Ray" Now there is also a vector connecting the two
particles, for particle A we could call this X. Define unit vectors
r(Ray) and x(X). The angle is just arccos( r dot x ), where dot is the
vector dot product.
> > may be interpreted as relative to a ray. This ray may be
> > generalized to a polarized axis.
[quoted text clipped - 15 lines]
> Sure, but you can't do much with it. It's too small to be
> interesting.
>> > By evacuating all of space and granting just two particles the
>> > context of dimensionality takes on a striking choice.
>> If you do that, you obtain something useless. Read on.
>> > If we allow for just one distance between these two particles
>
[quoted text clipped - 8 lines]
> This is a theoretical two body problem. It is the only one that we
> know how to solve.
This isn't quite correct. The 2-body problem is the only one with an
analytic (closed-form) solution.
Problems with larger numbers of objects can be solved to any precision
you like, and future behavior predicted to any precision you like.
Their behavior can be modeled to any precision you like. That's
generally taken to mean we can "solve" such problems, in a very real
sense.
> Can we simply accept that there is a distance x
> between these two particles measured in meters and that the distance
> will vary? I have never seen anyone actually use a measuring rod on
> particles before.
OK, I grant that you can do that. It's cheating a little, because it
apparently doesn't have any physical consequences in the universe
you've described, but it's at least well-defined.
We can also observe that, should a radar gun suddenly materialize in
the otherwise empty universe, one particle could use it to determine
the distance to the other.
You still have a big problem with _time_, though. How do you define
it in a universe with just two particles? A radar gun measures speed,
too, but it couldn't do that if it didn't come equipped with an
internal clock, and once you add a clock to the universe you've added
a whole pile of particles interacting in complex ways.
> The only reference points in the system are the
> two particles so there is one distance x, which varies based only on
> these two particle's interaction and some initial conditions. If you
> don't want to use fields I think for this context it is OK to just
> use a 1/(r*r) type of force
So we have two particles and a mutual field of some sort?
> but as you will see that is what I am
> troubled by:
[quoted text clipped - 3 lines]
> So let's assume that we have two particles containing only the
> property of mass.
Ah ... So, your mass tensor is nonzero and now, if you want to figure
out the interaction, you need to solve the field equations to
determine the curvature...
Or you can use the Newtonian approximation.
One way or another you have some sort of attraction operating between
them.
> We don't give them any angle characteristic. They are directionally
> symmetric.
In that case you appear to have made your universe explicitly
1-dimensional.
> We plop these two particles into spacetime. The only observable in
> the system is the distance and therefore the only data that these
> particles will ever obtain is one dimensional. To the particles they
> do not exist in spacetime. Instead they exist in a one dimensional
> space. So where is the spacetime?
Well, since you don't have any clocks in the universe, the "time"
dimension seems to be a little lacking. But aside from that, what's
wrong with spacetime with just 1 spatial dimension? It's used all the
time in SR problems.
> The original argument suggests that the system constructed here is
> invalid.
No argument I made. I just said it's too simple to be interesting.
> There is an informational mismatch that is incongruent with the
> notion of spacetime.
[quoted text clipped - 7 lines]
> relativity. Informational conservation might be a useful
> principle. The prediction it makes is already satisfied.
What prediction?
> I think the strongest argument against the mass construction above
> is that should the two particles fall into an orbit, perhaps
> elliptical, that they will form at least a two dimensional
> system. They will experience oscillating distance.
Indeed! Conservation of angular momentum comes into the picture.
Yes, come to think of it, they will behave that way. On the other
hand, if you put a massless and intangible observer in this sparsely
populated universe, he/she would be hard pressed to say whether these
two particles are orbiting in 2 space dimensions under the influence
of a central 1/r^2 force, or are oscillating in 1 space dimension
under the influence of a force that looks something like k(r-r0).
On the _other_ other hand, AFAIK there's no way you can get any
interaction going which will reveal the third space dimension, even
indirectly, in this limited situation.
> The hypothetical angle is an internal property that each particle
> has which allows it to measure the direction of the other
> particle.
But suppose the poor thing is rotating -- how would it know? A
rotating particle would "see" the other particle as revolving around
it, instead, unless it could figure out, somehow, that it's not,
itself, stationary.
If you make each "particle" complex enough so that it carries an
inertial reference frame within itself -- and can determine (a)
whether it's, itself, rotating and (b) identify an (arbitrary) set of
up, down, right, left, front and back directions then you've got
enough information to start talking about angles and a full set of
three dimensional information, but you've also got a universe that's
an awful lot more complex than just two elementary particles.
> Because we accept one distance between the particles
> angular information is really all that we have left to work with
> geometrically.
>
> In the minimal construction each particle now has a two dimensional
> context,
Huh? What's this mean?
Again, if you give each "particle" enough structure to have an
internal "orientation" and to determine whether it is itself rotating,
then each defines, in effect, a 3-dimensional inertial frame.
You still have, of course, got a bit of an issue with regard to
clocks.
> but the two together form a three dimensional system. The
> really hard part is to define the interaction as a function of both
> distance and these angles.
Can't you can set up the equations of motion in ordinary 4-space and
then just project the results down into whatever space you like?
The only problem with your 2-particle space is that there's very
little you can actually, physically, measure in that space.
> I'm not able to do it yet so I am sorry
> that I cannot specify this part of the problem. We could make
[quoted text clipped - 11 lines]
> features rather than predicting the exact interaction of those two
> particles.
Not at all. The only such "prediction" is that featureless particles
have no measurable features, not that particles _must_ have
features.
>> > then we might claim a one-dimensional system as in classical
>> > physics where we just work in one Cartesian dimension x for a
[quoted text clipped - 38 lines]
>>
> That's true, but he was also playing with varying the properties of
"he"?
> distance and time based on the properties of the system so it was
> crucial to address these concerns.
[quoted text clipped - 17 lines]
>
> I hope not any more.
Do you mean you defined it by the assertion that each particle has (in
effect) an internal gyroscope of some sort?
> But if you think it is ill defined still perhaps we could work on
> some more of the basics. For example the proposition holds that
[quoted text clipped - 4 lines]
> r(Ray) and x(X). The angle is just arccos( r dot x ), where dot is
> the vector dot product.
You've picked a random number and called it "angle". Now we can
say that the two particles are at "angle" relative to some vector.
"angle" may or may not vary with time, depending on whether a randomly
chosen direction varies randomly or not.
This doesn't seem terribly helpful. It provides no actual reference
point for measuring anything. It provides no way to determine, for
instance, angular velocity of the position vector of one particle
relative to the other in any meaningful way.
>> > may be interpreted as relative to a ray. This ray may be
>> > generalized to a polarized axis.
[quoted text clipped - 18 lines]
> Higher systems are based on the superposition of these two body
> systems.
Actually the 2-body systems generally used involve numerous other
bodies used for reference.
Such things as fixing the difference between a 1-dimensional central
force going as something like k*(r-r0) or a 2-dimensional central
force going as something like k/r^2 just don't come up when one uses a
universe with many complex objects in it, even when we ignore all but
two of them for the purposes of understanding basic electromagnetic
interactions.
> I really appreciate your discussion and challenge to these
> ideas. I've inspected your website briefly and will try to learn
[quoted text clipped - 3 lines]
>
> http://www.BandTechnology.com

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Tim - 21 Mar 2006 14:00 GMT
> >> > By evacuating all of space and granting just two particles the
> >> > context of dimensionality takes on a striking choice.
[quoted text clipped - 72 lines]
> In that case you appear to have made your universe explicitly
> 1-dimensional.
This is the conclusion that is troubling about the most simplistic
solution.
I did not explicitly make a 1-dimensional spacetime. I explicitly
stated real spacetime but out comes this 1D system.
> > We plop these two particles into spacetime. The only observable in
> > the system is the distance and therefore the only data that these
[quoted text clipped - 52 lines]
> it, instead, unless it could figure out, somehow, that it's not,
> itself, stationary.
This is the minimal construction. The Ray is the axis of rotation.
The angle and the distance are what the particle experiences.
I would not deny the vector that connects the two particles.
That is a fundamental piece of information.
All of the additional features you list below should not be necessary.
The angle is relative.
> If you make each "particle" complex enough so that it carries an
> inertial reference frame within itself -- and can determine (a)
[quoted text clipped - 12 lines]
>
> Huh? What's this mean?
An angle and a distance makes two dimensions of information.
> Again, if you give each "particle" enough structure to have an
> internal "orientation" and to determine whether it is itself rotating,
[quoted text clipped - 102 lines]
> Do you mean you defined it by the assertion that each particle has (in
> effect) an internal gyroscope of some sort?
yes.
> > But if you think it is ill defined still perhaps we could work on
> > some more of the basics. For example the proposition holds that
[quoted text clipped - 15 lines]
> instance, angular velocity of the position vector of one particle
> relative to the other in any meaningful way.
I didn't mean to introduce a random component into the system.
I just meant to define an angle in the simplest context I could.
As these angles (each particle has one) vary the system has become
three dimensional, satisfying congruence to spacetime informationally.
Again this is merely a minimal construction.
Can time in this system simply be an independent real variable such
that the distance and angles vary as a function of it? Where is the
need for clocks?
So we would have x(t), a(t), and b(t). a for angle alpha of particle A
and b for angle beta of particle B, and x for the distance between A
and B. I don't really like this, but if you insist I will try to go
there. I don't think I can deal with the radar gun you've suggested.
I guess this becomes a Newtonian model.
-Tim
> >> > may be interpreted as relative to a ray. This ray may be
> >> > generalized to a polarized axis.
[quoted text clipped - 40 lines]
> Nospam becomes physicsinsights to fix the email
> I can be also contacted through http://www.physicsinsights.org
sal - 21 Mar 2006 18:59 GMT
Time to do some snipping.
[Tim]
>> > We don't give them any angle characteristic. They are
>> > directionally symmetric.
[SAL]
>> In that case you appear to have made your universe explicitly
>> 1-dimensional.
>>
> This is the conclusion that is troubling about the most simplistic
> solution. I did not explicitly make a 1-dimensional spacetime. I
> explicitly stated real spacetime but out comes this 1D system.
I don't see the problem, really.
A system consisting of 1 mass connected to a solid wall by a spring
is "1 dimensional". Two masses connected by a spring but constrained
to move in a line is "2 dimensional". But that's just the
dimensionality of the configuration space, not the spacetime itself.
You've started with two particles in an otherwise empty universe. We
can ask several things about the system.
1) What parameters can be _measured_ inside this space using tools
available inside the space? Answer: Not enough to be interesting,
so let's drop that question for now.
2) What parameters can be _defined_ inside this system? In other
words, what parameters could an intangible ghost inside the
universe measure? There seem to be just two:
a) Distance between the particles
b) Relative speed between the particles
Anything else requires introducing some additional structure. A
vector which points in a "fixed direction", mentioned (far) below,
seems very artificial to me -- how does our intangible ghost keep
track of what direction was the "fixed direction"?
3) We cheated in (2).
How does our ghost measure distance? This is not a trivial
question. If this is a relativistic universe then "distance" is
only well-defined between points in an inertial frame of
reference. With just two particles, how do you determine an
inertial frame? How do you make measurements within a particular
frame of reference, when all you've got are two particles?
Suddenly we seem to need a whole flock of ghosts, all carrying
synchronized clocks, and the universe doesn't look so empty
anymore. In particular we end up inheriting an orientation from
the flock of ghosts, and the question of how to measure angles
becomes trivial. Perhaps we should make this a Newtonian universe
-- then we can just talk about "distance" and "time" without
specifying who measured them!
4) Can we define "time" inside the universe? Answer: Yes ... sort
of. As you pointed out, we can use the distance between the
particles as a "clock", _assuming_ that distance is changing. But
again, this doesn't work so well if the universe is relativistic,
because it's distributed (it requires both particles to determine
the time) -- it provides no way to define time for a particular
observer at a particular point, and provides no way to determine
the relative timing of spatially separated events.
5) What's the dimensionality of the configuration space of the two
particles? Looks like 1 to me; again, there is no reference point
inside the universe to tell you anything except how far apart they
are.
6) How many space dimensions are needed to describe the motion of the
particles? Answer: 1 or 2, certainly not 3.
7) Can we tell how the particles interact by watching them?
Answer: No!
Suppose the distance between them is fixed. Does this mean they're
non-interacting, or does it mean they're in a circular orbit around
a common center? Without some other point of reference the two
seem indistinguishable. What's worse, if the distance between them
is fixed we have no "clock" at all in the universe -- it's totally
static.
8) If we already _know_ how they interact, does that help?
Yes, it helps ... some. Suppose we _know_ they don't interact at
all. Then, if we see them grow closer together and then move
apart, and then just keep moving apart, we can say they are in
constant linear motion with respect to each other.
But if we have no clock in the universe except their relative
motion, we can't say anything more than that, as far as I can see.
With a separate clock, we can talk about how fast they're going,
and we can determine, up to a reflection, what plane they're moving
in.
9) What would _really_ help?
Three non-interacting stationary particles arranged
non-colinearly. That would provide an unambiguous inertial frame.
Then, add a fourth non-interacting particle which is painted red on
one side and blue on the other side. Set it spinning. Now there's
a clock.
But the simplicity of the 2-particle space is really lost at that
point...
[ snip ]
>> > The hypothetical angle is an internal property that each particle
>> > has which allows it to measure the direction of the other
[quoted text clipped - 11 lines]
> additional features you list below should not be necessary. The
> angle is relative.
Relative to _what_?
What parameter would a ghost in the universe measure in order to
obtain this angle?
The ghost would need to stick a thumbtack into the fabric of space in
order to provide a fixed point with which to obtain the angle, and at
that point there's a third particle in the universe (the thumbtack).
>> If you make each "particle" complex enough so that it carries an
>> inertial reference frame within itself -- and can determine (a)
[quoted text clipped - 13 lines]
>>
>> Huh? What's this mean?
> An angle and a distance makes two dimensions of information.
OK, you're talking about degrees of freedom here, or the
dimensionality of the configuration space, rather than the
dimensionality of the universe itself.
[ snip ]
>> > But if you think it is ill defined still perhaps we could work on
>> > some more of the basics. For example the proposition holds that
[quoted text clipped - 18 lines]
> I didn't mean to introduce a random component into the system. I
> just meant to define an angle in the simplest context I could.
But an angle needs to be between two vectors.
In simple terms, you need three fixed points to determine an angle.
You've got two. What's the location of the third point determined by?
You've postulated another vector, but provided no way to identify this
vector, and what's more, there seems to be no way to determine if it's
stationary or rotating.
> As these angles (each particle has one) vary the system has become
> three dimensional, satisfying congruence to spacetime
[quoted text clipped - 3 lines]
> that the distance and angles vary as a function of it? Where is the
> need for clocks?
As I said, if you just _assume_ time, then you've also just _assumed_
a Newtonian universe.
> So we would have x(t), a(t), and b(t). a for angle alpha of particle
> A and b for angle beta of particle B, and x for the distance between
> A and B. I don't really like this, but if you insist I will try to
> go there. I don't think I can deal with the radar gun you've
> suggested. I guess this becomes a Newtonian model.
Yes, so it appears.
[snip ]
>> > -Tim
>> >
>> > http://www.BandTechnology.com

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Tim - 21 Mar 2006 23:05 GMT
> Time to do some snipping.
>
[quoted text clipped - 220 lines]
> Nospam becomes physicsinsights to fix the email
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I think you have made a strong case for your position. Mine is merely a
position of information conservation. The spring analogy is coherent
though it would require constraining the spring in two dimensions. In
that regard the particles here are different. They are free in space.
That they only use one dimension of it may be possible.
If information is conserved then the relative dimensionality paradigm
states that we will never observe the simplistic particle in spacetime.
I don't know exactly what a spin-2 graviton means, but I suppose the
fact that it has a spin does not put it in the simplistic category.
The position of the second particle relative to the first particle is
partially defined by the angle measured by the first particle to the
second particle via its internal reference.
Since superposition is the way that we get to higher systems the naked
two body system is relevant to those systems.
A big problem with the angle hyposthesis initially made is that if each
particle determines its interaction by information unknown to the other
particle then the possibility of destroying conservation laws arises.
If each particle has its own angle that the other knows nothing about
then a degree of independence arises. One would have to arrive at a
consistent conclusion there. Maybe the other angle is available via a
virtual photon type of construction as Ken has suggested.
I appreciate your detailed explanations here. I think I'm OK putting
this away for a while.
Thanks for all of the advice.
-Tim