Curie Principle, Its Consequences For Technical Systems, and How to Neutralize Them

Y. B. Karasik,
Thoughts Guiding Systems Corp.,
Ottawa, Canada.
Copyright © 1986-2008 by Yevgeny B. Karasik

1. Introduction. The famous French physicist Pierre Curie discovered that when an object is immersed into a medium, this medium destroys those parts of the object’s symmetry, which the medium does not have [1]. Specifically, if object has axes and planes of symmetry {Siobject}i=1N and medium has axes and planes of symmetry {Sjmedium}j=1M , then after some time lapse, the object will only have axes and planes of symmetry

{Siobject}i=1N {Sjmedium}j=1M.

This observation was called Curie Principle.

It is plausible to conjecture that the same holds if not medium but fields act upon an object. The fields destroy all elements of object’s symmetry, which the fields do not have. We can call it generalized Curie Principle.

This principle is behind many unwanted effects in technical systems. For example, when a turbine is stored in the horizontal position for time long enough, its shaft eventually bends. This happens because gravitational field that acts upon the turbine does not have horizontal axis of symmetry (which turbine has). That is why the turbine eventually loses it too.

Engineer has to take into account the generalized Curie Principle and do the following:

  1. Conform symmetry of an object to the symmetry of a medium where it is supposed to work, or to the symmetry of the fields which are supposed to act upon the object;
  2. Find ways to resist the destroying action of the Curie Principle;
  3. Make shape of the object adaptable to the symmetry of the medium/fields.
The purpose of this article is to describe these options in more detail.

2. The minimum information principle. At the first glance, it might appear that advice to adapt the shape of an object to the symmetry of the environment and/or to the symmetry of loads/fields acting upon the object is pretty trivial. One could assume that engineers always do so. More specifically, one could assume that when designing a system, engineers always analyze and take into account the symmetry of loads it is going to be undergoing, or the symmetry of fields, which are expected to act upon it. In fact, engineers often do not bother neither to analyze these symmetries nor take them into consideration (unless it is aviation or construction engineering where negligence of this matter is known to be dangerous).

For example, until recently designers of skates did not take into account the symmetry (or absence thereof) of loads acting upon various parts of skates. They always proposed designs where blades were perpendicular to the soles of boots, as if skaters always stand still and vertically. But when they took into the consideration the real posture of a skater when skating then they had to part with the symmetric design because the fields (loads) do not have such symmetry. It turned out that the most optimal position of blades relative to the soles is not 90° but 93° [2].

Why do people prefer symmetric designs unless something forces them to choose an asymmetric one ? Is it not similar to mechanical bodies always traveling along the path of least action ? May be human thoughts also "travel" along the paths of least "action", which in this case is the path of least information. Symmetric designs carry less information than asymmetric ones. They need less bits to encode. They need less explanation and less questions to answer. Asymmetric design has to be motivated but symmetric has not. That is why in the absence of a motivation people choose a symmetric design. Irrespective to the causes the fact is that engineers involuntarily try to minimize the information embodied in their designs. This could be called the minimum information principle.

3. How to neutralize the destroying action of Curie principle. Suppose that symmetric portions of an object are subject to asymmetric impacts. Then according to Curie principle these asymmetric impacts will eventually destroy the symmetry of the object. If the object cannot be made asymmetrical, then necessity arises to resist the destroying actions of asymmetrical impacts.

One of the possible approaches that may help here is to set object into motion. The purpose of setting it into motion is to alternate symmetrical portions which experience asymmetrical impacts. In particular, if the object has an axis of symmetry and portions symmetrical relative to this axis experience asymmetrical impacts, then the object has to be set into rotation around this axis.

For example, the aforementioned problem of turbine storage can be resolved if turbine is set into a very slow rotation while it is stored.

In case the object does not have an axis of symmetry but experiences impacts of a planar field, then the shape of the object has to be modified and made axially symmetrical. The axis has to be perpendicular to the plane of the field. And the object has to be set into rotation around this axis.

For example, after empty rocket fuel tanks are discarded from a rocket, they usually burn out. Analysis of the thermal loads on the discarded tanks have shown that the front portion of the tank starts burning first because it is heated by the airflow much stronger than the rear portion of the tank. To eliminate such asymmetry, it was proposed to make tanks cylindrical, align them across the airflow and set them into rotation before finally discarding. Then the thermal load would be uniform across the surface of the tank and it might not burn down.

Rotation does not have to be continuous. For example, any ship experiences asymmetrical actions of the surrounding environment: its lower portion is under water and suffers from corrosion, whereas the upper portion is above surface and does not suffer as much. There were proposals to build symmetrical ships that would periodically capsize to equalize the influence of sea. Besides having a longer lifespan, such ships would also have another advantage: they would be unsinkable.

If the field is not planar, then the shape of the object has to be made to coincide with an equipotential surface of the field.

4. How to make the shape of an object adaptable to the symmetry of the environment. Many technical systems alternately work in environments with different symmetries or work in the same environment but its symmetry changes over time. In both cases, the machines will be destroyed unless they have an ability to adapt their symmetry to the changing symmetry of the environment.

Difference in the symmetry of a machine and the symmetry of the environment means that symmetrical portions of the machine are subject to asymmetrical impacts of the environment. To eliminate such asymmetry, the shape of the machine should take a surface of equal action of the environment (or an equipotential surface in the case of external fields). If surfaces of equal action vary over time, the shape of a machine has to follow suit. There are many physical effects that allow one to achieve it.

If impacts of the external medium are mechanical in nature, then in order to allow the shape of a machine to take the shape of a surface of equal load of the mechanical field the machine has to be made of flexible materials. For example, the rotating turbine experiences impacts of both gravitational and centrifugal fields. The equipotential lines of the total field (gravitational + centrifugal) are not straight. That is why the shaft of a turbine should not be straight too. It was proposed to make the shaft of a turbine flexible to allow it to take the shape of one of the lines of equal load of the total field (gravitational + rotational) and thereby prevent it from braking up.

If the external field is thermal, then in order to allow machine parts to take the shape of isotherms of the field, they have to be made of the materials that “remember” certain shapes and take them under specific thermal loads.

R E F E R E N C E S:

  1. Curie, P. (1894), Sur la symetrie dans les phenomenes physiques, symetrie d’un champ electrique et d’un champ magnetique. J. de Phys. (Paris), 3, 393 - 415.
  2. The USSR invention authorship's certificate # 1111677.