Expert: Daniel Mazur - 1/28/2008

Question
Dear Mr. Mazur,
    I am very interested in theoretical physics- especially the science and study behind wormholes, zero-point energy, and most of the more exotic pieces of the universe. What kind of careers could I find in this field of study? My other question is why do people say that a purely magnetic motor is not possible? In theory, it is very possible to convert the linear attraction/repulsion of magnets into rotary movement. The motor is not perpetual motion, because there is force being added into the equation(the magnets). If at all possible, answer the last question in layman's terms, or at least something a Freshman could understand.
    Thank you
    Kristofer Schumacher

Answer
Hello Kristofer,

the career that seems to fit your inclinations is Theoretical Astrophysics. As my field is experimental Physics of Surfaces and Interfaces of Solids, I may be wrong, but I have the impression that there are (worldwide) many students of theoretical astrophysics and only a small number of positions. For some reason, Astrophysics and Theoretical Physics are extremely popular fields of study, but at the same time this branch of physics gives little or no results that can be applied in people's lives. The lack of commercializing opportunity means that no industrial entities would employ us to do theoretical astrophysics, all funding must come from governmental agencies and even for them it is a "luxury" to fund this type of research. So, you must be really, really good from the start (doctorate years) to show people that you're worth it.

I am not sure I understand your second question (i.e. what you mean by "purely magnetic motor") correctly, I would very much like a follow-up, should my understanding be faulty. My understanding of a "purely magnetic motor" would be something like an electromotor, where coils are replaced with solid state magnets... in other words eliminating the need for electrical power supply.

The explanation, why such thing cannot work can be made in more than one way, depending where you want to start. The simplest way is through energy transformation and conservation. Let us first check, why the operation cannot be perpetual without a continuous supply of "input energy". Motor would be defined as an engine that transforms energy of type "X" into rotary motion. Just like every other engine, the efficiency will always be less than 100%, some of the energy input will be lost in dissipation (friction and subsequent heat). This is the 2nd law of thermodynamics and is entirely independent of what type of energy is our "X".

Now, the function of electromotor completely depends on that the coils are NOT SWITCHED ON all at the same time. It is the switching on and off that allows the rotor to move on and on, otherwise it would jerk just once and stand still for the rest of eternity. We cannot turn solid magnets on and off simply and in a repeatable cycle (see more below). Perhaps we could move them in and out repeatedly and that WOULD work, but at that point I would not call the motor "magnetic" anymore. Here the magnets are only mediators in transforming the input mechanical (!) energy into the output mechanical-rotational energy.

The idea of using magnetic (!) energy to do work is an old one and I myself answered a question about it here at AllExperts.com. One first needs to understand, what solid magnets are, what makes them ferro-/para-/dia-magnetic, and that is not a high-school topic. Firstly, all atoms have a quantity "magnetic moments" defined. Some atoms have it zero, some non-zero. Materials (ensembles of many atoms) can have the atoms arranged so that the "total magnetic moment" (or "magnetization") is either zero or non-zero. It is this arrangement and the ease or difficulty, with which we can change the state that decides, whether a material is ferromagnet or anything else. We cannot harvest the magnetism of atoms themselves, we can only get the energy difference between different orientations of the atomic magnetic moments in a material. It is impossible for us to attach cogwheels to individual atoms, or even large- (fraction of a millimeter)-size grains to change the moments' orientation. There are a few ways, to influence magnetism as a whole, but none of them is practical enough to make an engine. For example, sufficiently strong external magnetic field can change materials magnetic state. Heating makes it easier. Many technical materials become magnetic (gain permanent magnetization) during machining, drilling etc. High pressure works for some materials... But to truly use magnetic energy in a motor you'd need a supply of ferromagnets on the input and a mechanism for demagnetizing that would not loose the energy, but transfer it to the rotor. The waste then would be a demagnetized material... The amount of energy thus available is so tiny that its out of consideration - compared to other motor mechanisms we have available.

I hope this helps, let me know, if I did not quite answer you.
Cheers,
Daniel