This article extends an earlier, more general discussion of metrics that considered a particle’s shape as described by its radius vector . Initially, the radius was established from a particle’s quark content, and a vector space was defined from sets of particles and their radii. was characterised using statistical averages , standard deviations and correlation coefficients noted by . These quantities have already been assessed for generic compound quarks.

Now let us consider that might be filled with a more restricted set of particles that have special attributes. Specifically we examine collections of atoms so that radius vectors may be expressed in Cartesian coordinates. Atomic aggregates are characterized using their orbital radius , a wavelength and their phase angle . We say that has a **Euclidean metric** if every particle satisfies the following conditions.

- Atoms and molecules must be fully three dimensional like cylinders or rods so that and . Wavelengths and radii are all presumably positive, not nil.
- Particles must exhibit some variation in their shape so that . The standard deviation for any component of the radius is presumably positive.
- The space must be well-stirred. We require spatial homogeneity at an atomic level so that .
- The particles in cannot all have an extremely low temperature, or all be resonating like the atoms in a laser. We assume that so that there is some variation among atomic phase angles.
- Finally, atoms must interact incoherently so that the variation among phase angles is random. Then we can presume that large sums over odd powers of circular functions of add-up to zero.

For a specific example of a Euclidean space consider a big collection of atoms, and larger particles that are composite atoms, noted by . Let these particles be described using the rotini model where atomic shapes are like a corkscrew spiral. They approximate a geometric curve called a helicoid so that atomic radii can be mathematically written as

and

The radius vector is expressed in Cartesian coordinates as so a space like can be generically represented as

The average radii of the particles in are given by

As noted above, we presume that the atoms in have phase angles that are completely incoherent so that sums over the circular functions add-up to zero. Then

and so the variations in particle radii are

We presume that all the particles in are three-dimensional so that and . And as noted above, we also assume that phase angles vary. So and the standard deviations in particle radii must be positive

We also presume that has spatial homogeneity at the atomic-level. Then any variations cannot depend on direction, . But by their definition, correlation coefficients and standard deviations are related as so that

The other correlation coefficients are given by

These coefficients must all be nil because, as noted above, we presume that large sums over odd powers of circular functions of add-up to zero. Then recall that the metric of is given by the ratios

The Euclidean Metric | |
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where and . So overall

and

Then we say that the metric of is Euclidean.