February 2, 1955
Dear Prof. Einstein:
All I wanted in my last letter to you was to gain the concession that a comet, going through the corona of the sun or through an outburst of ionized gases, sustains an electromagnetic effect. The consequences of opening the gate to such an effect into the heavenly mechanics force the astronomer to disregard physical experiences, in order not to violate in the least the system of 1666. But in fact the comets do not follow precisely Keplers third law: those that pass near the sun (like Enckes comet) show acceleration unexplained by gravitational mechanics.
My knowledge is not great, yet gravitation with static electricity I do not identify, as you understood me and then refuted me with the fall of a body which must discharge itself upon touching the ground. In the following I present my thoughts about the nature of gravitation and discuss also in shortmore in the form of questionsthe four systems of the world, of which the first is the Newtonian, and the second actually does not violate the Newtonian.
Do you remember how I asked you: If the good Lord would give you the task to conceive a plan for a new universe, where gravitation of the inverse-square variety takes no part, would you be able to comply? To Newton He could not have made such a proposition, since Newton had only a very vague idea of electricity. However, the sentence with which he concludes the Principia is very interesting. I let this sentence follow as a supplement.
The end paragraph of the PRINCIPIA by Newton
But hitherto I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses . . .
And now we might add something concerning a certain subtle spirit which pervades and lies hid in all gross bodies; by the force and action of which spirit the particles of bodies attract one another at near distances, and cohere, if contiguous; and electric bodies operate to greater distances, as well repelling as attracting the neighboring corpuscles; and light is emitted, reflected, refracted, inflected, and heats bodies; and all sensation is excited, and the members of animal bodies move at the command of the will, namely, by the vibrations of this spirit, mutually propagated along the solid filaments of the nerves, from the outward organs of sense to the brain, and from the brain into the muscles. But these are things that cannot be explained in few words, nor are we furnished with that sufficiency of experiments which is required to an accurate determination and demonstration of the laws by which this electric and elastic spirit operates.
[end of the Mathematical Priciples; transl. by F. Cajori]
Newtons plan in which the heavenly bodies in their movements are influenced only by gravitation (and in a very small measure by light pressure). For this plan speak:
a) The simplicity of the law of gravitation. (The simplicity would be more complete if the same system would also be in action as the dominating force in the atom, and if gravitation, like all other energies in nature, were given to transformations).
b) The exactness with which the positions of the planets are predicted. (The exactness of Ptolemaic astronomy in predicting eclipses and conjunctions was superior to that of Copernicus; and still the geocentric system is false).
c) The discovery of Neptune and Pluto (Neptunes position, but not its distance from the Sun was calculated in advance; Plutos mass is by far not sufficient to explain the disturbances it causes).
Some of the circumstances which cannot be explained, or only with great effort, are:
1. The Sun, Jupiter and Saturn rotate quicker on their equators; the rings of Saturn rotate quicker than the planet. The inner satellite of Mars revolves quicker than Mars rotates; the sun possesses only 2% of the angular momentum of the solar system.
2. The Suns protuberances gain in speed with the distance from the Sun. They fall back as if attracted to the place from which they erupted, falling back (as if on a rubber band) to the sun without acceleration.
3. The Suns equatorial diameter is equal to, and in the consensus of other observers is 0.038 seconds of the arc smaller than the polar diameter (and to this says Menzel: We are loathe . . . ).
4. The tides caused by the Sun in the Earths atmosphere are 16 to 20 times greater than those caused by the Moon.
5. The Moon and [some] other satellites always show their planets the same face.
6. The comets tails are turned away from the sun and move in perihelion with a speed approaching the speed of light; no attempt at quantitative calculation has been made in this direction.
The heavenly bodies are held in their orbits mainly by gravitation; however they are not neutral.
Since static electricity also acts according to the inverse square law, its presence is masked by gravitation. From this follows: The masses of the heavenly bodies are not exactly calculated.
This plan can explain satisfactorily most of the difficulties of Plan 1. For this Plan 2 speak also, among others, the following facts:
1. The Sun too has a general magnetic field the strength of which is estimated very differentlythe difficulty lies in the angle of observation. The corona has a form which resembles the lines of force of a magnetic field and extends far out.
2. In several stars a strong magnetic field (7000 gauss) has been detected. These stars must also be electrically charged because electrical currents would hardly occur on hot stars. The movement of two members of a double star system which rotate around each other in a few hours must probably be affected by more than just gravitation alone.
3. The earth is a magnet. The earth is enveloped in electrical layers of the ionosphere. Chapman postulates a strong electrical layer high (12,000 to 16,000 miles) over and around the earth.
4. The planets Mercury, Venus, Mars, Jupiter, Saturn, clearly influence our ionosphere and radio-reception; Jupiter and Saturn also have a connection to the origin of the sunspots.
5. The polar lights consist of electrical charges which come from the sun and which, after eruptions on the sun, or after the passage of a big sunspot, influence radio transmission and ground currents, and cause magnetic storms.
6. Meteorites are magnetized without exception. Also, upon entering the atmosphere they are regularly diverted toward the east and sometimes even seem to be hurled out after they have already penetrated into the atmosphere.
7. The fact that comets glow in cold space (lines of emission), and also the contraction of their heads when closer to the sun, speaks for an electrical effect.
8. A rise and fall in the strength of mutual disturbances between Jupiter and Saturn in the years 1898-99 as opposed to that of the years 1916-17 (18 % difference: J. Zenneck, Gravitation in Encycl. der Math. Wiss., vol. V, first part, p. 44), speaks also for this and the following plans.
As to the argument that the photoelectric effect of the sun would neutralize the charges on the planets, I would like to ask: Would not the photoelectric effect cause charges on neutral planets? And why is not our ionosphere neutralized by the photoelectric effect?
The other argument against this plan is in the assumption that the sun cannot be charged because it would repel the surplus ions. I would answer: According to spectral analysis, the atoms on the sun have been left without many, often without any orbiting electrons. Could not the electrons which have left the protons in their closest proximity where the attraction is tremendous, also have left the sun entirely? Actually the sun hurls out charged particles (polar lights, also cosmic rays) as if it were charged and would like to reach a neutral state. (However the sun, charged as it is, changes its charge imperceptibly: were it not so, then the system would constantly change its paths.)
Another reply: In the atom the same problem exists: how can charges of the same sign hold together in the nucleus?
Now a third reply: The stars, which are strong magnets, must also be electrically charged, because no electrical currents can exist at such temperatures. Why do the surplus protons or electrons stay there? And if there, then probably also on the sun.
And finally: Should we not, instead of considering the sun as neutral, rather consider the whole solar system neutral, with a surplus of charge of one sign on the sun and of another sign on the planets?
Gravitation would be a force which quickly diminishes with distance. Static electricity would be the dominating force between the heavenly bodies.
This would mean that the force which we know from our experience on earth as gravitation does not effectively reach the moon.
Against such an explanation speaks the fact that the Cavendish experiment under different conditions and distances between mutually attracting masses always showed the same results. However, as far as I can judge, this experiment was not performed in a Faraday cage; at the same time we know that the atmosphere has an electric potential and that the potential difference strongly increases with distance from the ground, but probably could be almost identical in different laboratories.
This plan of static electricity as the dominating force between the heavenly bodies would explain most of the phenomena which are unexplainable in plans 1 and2, but against it speak the following facts:
1. In the case the planets are all of the same charge (positive or negative), they would repel each other. But would they not behave like two parallel conductors which attract each other when their currents flow in the same direction?
2. If, for instance, the sun is positive and the earth negative, then the moon would again be positive, and the sun would repel the moon.
In this plan, too, gravitation would be a force which diminishes rapidly with distance. Planets, satellites, and comets are charged bodies which move in the magnetic field of the sun, and which themselves create magnetic fields.
This plan would explain:
a. The retrograde movement of various satellites and comets;
b. the distribution of angular momentum;
c. the behavior of cometary tails; also the fact that comets are attracted to the sun from great distances, but were never seen falling into the sun, even though they are unstable in their orbits;
d. the position of the moon and other satellites which continuously turn the same face to their planets;
e. the energy of cosmic rays;
also the fact that the sun is hotter in the corona than in the photosphere; and several other facts.
Since magnetic force decreases quickly with distance, the heavenly bodies must be differently charged in order to obey Keplers laws. The planets which are further away from the sun must have a correspondingly stronger charge. This would be analogous to the arrangement of electrons in the atom. It would also explain the disturbances caused by Pluto, the mass of which is by far not sufficient to explain such perturbations.
Against this (4) plan speak the enormity of electric and magnetic forces necessary to make this plan effective.
The sun moves in relation to the stars; it rotates; the charged planets revolve around the sun, and create a Rowland magnetic field. How does the magnetic field between the sun and the planets behave, and how quickly does it decrease? (The calculations which I received from several young physicists differ greatly and go all the way from 1/r to 1/r4).
But above all, are the physical experiences of laboratories always applicable to the sky? There, a very great and hot mass of gases moves in the coldness of space; how would the magnetic field behave under such conditions?
It is apparent that plans 2 and 4 sin less against facts and observations than do plans 1 and 3. In order to decide between plan 2 and 4 the Cavendish measurements between impeccably neutral bodies must be repeated. But how impeccably? The electrical repulsion between two protons is 1040 times stronger than their gravitational attraction.
With cordial greetings,