Michael Faraday’sElectrogravityBy Andrew N. Adler[*]

Copyright © 1986 by Andrew N. Adler. All rights reserved.

1

The search for a relation between electricity and gravity comprised one of Michael

Faraday’s last research undertakings.[1] During his first period of experimentation, Faraday

himself deemed his chances of success very slim.[2] His colleagues almost unanimously

ignored or criticized his theoretical ruminations on the subject, and Faraday openly courted

hostility by espousing them. When his results of 1849 yielded nothing useful, Faraday

published them anyway, writing that, “[The negative results] do not shake my strong feeling of

the existence of a relation between gravity and electricity, though they give no proof that such a

relation exists.”[3]

In 1855, Faraday lamented, “I suppose that nobody will accept the idea [of gravity inter-

conversion with electricity] as possible.”[4] Yet, four years later, he executed another round of

electrogravity investigations. These also failed. Faraday again sought publication, but this time,

he was prevailed upon to withdraw his paper.

Faraday searched so diligently for such an elusive goal because he wanted to verify a

cherished theory ― the conservation and convertibility of all forces ― that he thought followed

inexorably from his religious beliefs. In short, he did not separate religion from science.[5]

Faraday, though, often cautioned others against dogmatism. He decreed, for example,

that, “The scientist should have no favourite hypothesis; be of no school; and in doctrine have

no master.”[6] Although Faraday did not always follow these guidelines, he sincerely adopted

them. Again for religious reasons, he believed that human beings are inherently fallible, and

that experimental and theoretical errors remain inevitable. In one respect, then, Faraday took an

inductivist attitude towards his work. On the other hand, Faraday perceived the paramount

importance of imaginative thought, and he could not resist the temptation to fabricate new

hypotheses.[7] Thus, Faraday “both delighted in and feared speculation.”[8]

2

Regarding his gravity researches, Faraday declared, “Let the imagination go, guiding it

by judgment and principles, but holding it in and directing it by experiment.”[9] Yet as noted

above, for this scientist some “principles” rest upon absolute truth.[10] Neither negative

experiments nor conflicting theories can disprove such “principles.” A tension thus resides in

Faraday’s method, although neither he nor scholars of his work necessarily have admitted as

much.

Of course, Faraday was motivated, too, by the prospect that a successful unification

would revolutionize science. As he confessed one day in 1849:

It was almost with a feeling of awe that I went to work, for if the hope should prove well

founded, how great and mighty and sublime in its hitherto unchangeable character is the force I am

trying to deal with, and how large may be the new domain of knowledge that may be opened up to the

mind of man.[11]

Other scientists seeking some grand synthesis must have shared this “feeling of awe.” Thus,

even Einstein was driven to spend years in an endeavor similar to Faraday’s; yet electrogravity

eluded him as well.

Faraday’s electrogravity efforts reveal the preconceptions and predispositions he

developed over a lifetime devoted to religion and science. This essay treats in depth the

theoretical and sometimes minute technical ideas crucial to Faraday’s electrogravity

experiments. True, these are not Faraday’s best ideas: his cognitive abilities were in decline,

and he did not even devise the best experiments to explore his conjectures.[12] Still, it profits

the historian of science to highlight the important tensions in Faraday’s changing conceptions,

to trace how he modified some beliefs yet felt unable to abandon others. For, Faraday

committed himself, to various degrees, not just to the unification of all forces, but also to the

primacy of electricity as the most important manifestation of the unified force, and to the

3

notions of polarization, action at a distance, and field symmetry. Intriguingly, he struggled with

complicated (and sometimes deceptively mundane) consequences of revising these scientific

themes while maintaining, although often trying to compartmentalize, a fixed theology.

The Conservation & Conversion of Force

Faraday based his conceptions of “force” on his religious convictions. Sometimes he

uses “force” to mean “power,” with its wide and complex connotations, while at other times he

means something more specific (and nearer to our notion of the term). He was aware of the

semantic difficulty, penning this remark to Maxwell in 1857:

I dare say I have myself greatly to blame for the vague use of the expressive words… What I

mean by the word [“force”] is the source or sources of all possible actions of the particles or materials

of the universe: these being often called the powers of nature when spoken of in respect of the different

manners in which their effects are shewn.[13]

That Faraday could never specify this vague concept proved an embarrassment to his

theories.[14] Nevertheless, he gave this term’s wider implications a priori status. For Faraday,

the indestructibility of force derives immediately from the fact that God created everything, and

thus only God can annihilate.[15] Furthermore, forces could not vanish or dissipate:

Just as non-conservation of force would have been a slight on God’s omnipotence, so

“wastage” by an unnatural motion (violating least force) would have implied a lack of design,

contradicting the more fundamental fact of Providence: that in making the universe God created a

natural economy specifically for the benefit of mankind. It followed that every expenditure of force

must have a use.[16]

Faraday was a member of the rigid Sandemanian Church, which, according to Levere,

“held that Christianity was of an intellectual character, having its origins in understanding. In

the natural world, therefore, there must be an intellectually comprehensible unity and logical

4

coherence.”[17] This “unity” of God’s plan, thought Faraday, would manifest itself in a unified

force theory.[18] While Faraday’s teleological beliefs would seem to align him with the

Naturphilosophen, Levere points out that Faraday appealed to strict evangelism and divine

revelation, not to metaphysical arguments, and that for him, a dissociation between religion and

science would be incomprehensible.[19]

In some of his writings, Faraday breaks out of his inductivist mode and demonstrates his

confidence in religious presuppositions. In his seminal essay, “On the Conservation of Force”

(1857), he states that, “The case of a force simply removed or suspended, without a transferred

exertion in some other direction, appears to me to be absolutely impossible.”[20] Later in the

same essay, he explicitly invokes God, declaring, “We have a right to ask these questions, but

not to ignore or deny the conservation of force.”[21] While Faraday resorts to such dogmatism

very infrequently, his religious biases of necessity infiltrate his science, in a manner not always

recognized by commentators.

We turn now to two additional thematic concepts — the primacy of electricity and of

polarization. These concepts are fundamental to understanding Faraday’s work on

electrogravity and his ambivalence about the nature of gravity.

The Primacy of Electricity

Faraday insisted that electricity constitutes the fundamental force, although nothing in

his theology seems to necessitate this assumption. While he would certainly prefer to discover a

fundamental force, “convertible in its manifestations,”[22] it would appear natural that

electricity should be relegated to one of these manifestations. Yet as early as 1815, Faraday

averred that electricity is “the most extraordinary and universal power in Nature.”[23] This

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power would even explain life itself.[24] Moreover, Faraday suggested that all substances

harbor electrical properties.[25]

Perhaps Faraday’s fascination resulted from the fact that his early experiments almost

exclusively involved electrical phenomena. In any case, he convinced himself that gravitation

would most likely represent a “subordinate” manifestation of the electric force. He found great

encouragement in the theories of O.F. Mossotti, writing to Whewell in 1836 that:

I have been exceeding struck with it [Mossotti’s memoir] & hope it is correct in its mathematical

part of which I am no judge… [H]is view jumps in with my notion which I think I mentioned to you that

Universal Gravitation is a mere residual phænomenon of Electrical attraction & repulsion.[26]

The particulars of Mossotti’s theory were probably flawed. (Faraday asked Whewell to

check Mossotti’s mathematics, but no reply has been published in Faraday’s correspondence.)

In 1838, however, Faraday again declared his presupposition, and in 1857 remarks that,

“Gravity may be only the residual part of the other forces of nature, as Mossotti has tried to

show….”[28] Maxwell also concluded that Faraday espoused this viewpoint:

You [i.e., Faraday] have also seen that the great mystery is not how like bodies repel and unlike

attract but how like bodies attract (by gravitation). But if you can get over that difficulty, either by

making gravity the residual of the two electricities or by simply admitting them, then your lines of force

can ‘weave a web across the sky’…[29]

Polarity & Force

By August 1836, Faraday had come to believe that “polarization” was the “essential

principle”[31] of his new science of electricity. Faraday’s biographers describe his theory and

experiments in great detail.[32] In summary, electricity is a transmission of strain or tension

between contiguous particles. Induction occurs when particles are fixed in space and cannot

6

easily transmit this force. The relief of this stress occurs through discharge. Thus, electrostatic

inductive capacitance consists of successive polarizations and depolarizations.

The idea of polarity arose from considerations of symmetry. Faraday convinced himself

that no isolated, discrete charge exists, and that one cannot separate positive from negative

aspects of the force. Further, for him, curved lines of force yielded experimental proof that

electricity does not travel from positive to negative poles directly, but rather by transmitting

“strain” along an “axis of induction,” through repeating molecular polarizations.

Each particle induces an opposite charge in its nearest neighbor. Faraday achieved great

success with this theory, using it to integrate electrical action (e.g., static and dynamic,

chemical, animal, etc.). Polarizability became his guiding theme, allowing him to carry out his

favorite task, unification.

Polarizable forces represented those that acted inductively at all orders of magnitude.

Faraday liked this operational definition because he could always resort to empirical decisions

based on it. Still, this definition became problematic, as discussed below, when Faraday tried to

unify other forces with electricity.

Polarizable forces, he supposed, must act via contiguous particles. Lines of tension

curve, since force must proceed in the direction of the nearest existing particle. A polar force

acting at a distance would violate the conservation of force. Gooding explains that, “Faraday

believed that the tension between two particles represents a fixed, definite quantity of

action…To allow that some part of the force can act beyond the nearest existing particle would

be to deny conservation of force over the interval between the two contiguous particles.”[33]

At this stage, Faraday thought that non-polarizable forces do exist. And, crucially, non-

polarizable forces need not behave locally: Polarizability implies action via neighboring

7

particles, which in turn forbids action at a distance for such forces. (Curved lines were taken as

proof of action via neighboring particles.) Yet “action at a distance,” defined appropriately[34],

occurs for non-polarizable forces. In this case, the force skips over an adjacent particle or

particles without imparting tension to them. Conservation of force is thus still satisfied.

Almost all commentators have supposed that Faraday disliked action at a distance, and

that he based this hostility upon a philosophical denial of instantaneous propagation.

Presumably, he was influenced by Berkeley’s conception of time[35] and various anti-

Newtonian theories of point atoms. (Point atoms fill all space.)

This present essay contends that Faraday was ambivalent about gravitational action at a

distance because he was ambivalent about gravity’s polarity or non-polarity. Moreover, Faraday

did not deny gravitational action at a distance solely on the basis of matter theories, dynamical

atomism, æther theories, or the like, but rather because of the presupposition of polarity for all

forces which he developed in the 1840’s.

As discussed above, Faraday’s notions derive principally from his theology, not from

Kantian metaphysics. It is not surprising, then, that Heimann[36] and Gooding[37] contest his

alleged overriding concern with matter theory.[38]

Faraday’s own words demonstrate that he had no misgivings in 1836 about gravitational

action at a distance. He contrasts electrostatic induction, which acts on contiguous particles,

with gravity, which acts distantly:

This inductive influence seems like an action of particles, different in its nature & kind from that

of gravity; for it is a power acting in curved lines, i.e., by intermediate particles.[39]

As explained, Faraday assumed that curved force-lines imply local (i.e., non-distant)

action. Guided by this assumption, Faraday “proved empirically” that electrostatic action is

local. But, he has made no such determination for gravity or magnetism:

8

That [electrostatic] induction through Air, etc. does not act in right lines but in lines variously

and much curved or bent to circumstances, is a strong proof that it is an action of contiguous particles

affecting each other in turn, and not action at a distance. Contrast with direct attraction, as Gravitation

or Magnetism through matters indifferent to it…[40]

So far, Faraday has noticed that the lines of gravitational action were straight. (He also

erroneously believed the same for lines of magnetic action in empty space.) Therefore, he

deemed both forces non-polar. Yet Faraday must have disliked establishing the dichotomy

between polar and non-polar forces: He wanted to place all forces under the rubric of

“electrical,” and electricity itself was polar. It probably seemed unlikely to Faraday that he

could associate electricity with, say, force Φ, unless the mode of transmission of force Φ

approximately matched that of electricity. If force Φ were non-polar, however, a fundamental

dissimilarity stood in the way of unification, and this is likely why Faraday eventually began to

demolish the very idea of non-polarity.

The Continuing Search for Polarity: 1837-1850

Faraday became increasingly absorbed in trying to discern new polar effects and in

unifying new forces with electricity. Faraday convinced himself that magnetism was a polar

force, and he attempted for eight years to show that magnetism polarizes matter placed in its

course, analogously to inductive capacitance of the electrostatic force (his 1836 discovery). He

looked for a state of progressive tension as he had before. His repeated failures did not deter

him. Finally, in 1845, he discovered the “magneto-optic effect” and “diamagnetism.” These

discoveries exhibited a relationship among electricity, magnetism, light, and matter.

Furthermore, they showed that a steady magnetic force affects non-magnetic matter in a polar

manner. Here, magnetism acted locally and inductively, in curved force-lines. The effect

confirmed his views of the convertibility and polar nature of force.

9

Faraday also searched for a link between electricity and light in 1822, then in 1833 and

again in 1845, and failed each time.[41] Faraday also repeatedly tried to demonstrate that light

has poles but failed and never published.[42] What emerges is that at least one phenomenon —

light — did not seem polar in the precise sense that electricity was, nor did it appear to

interconvert directly with electricity. One could already question the grand unification of forces

subordinate to electricity.

Faraday does not dwell on this problem, because recent triumphs encouraged him to

experiment further. Since “crystalline” (cohesive) forces were capable of acting upon polarized

light, he thought that they might be related to the diamagnetic force, which displayed similar

properties. He tested this theory and dubbed the newly-found relationship the “magnecrystallic

force.” By September 1848, it was evident that the magnecrystallic force had unusual

properties. Williams explains:

In the Twenty-second Series Faraday reported that, “the line or axis of MAGNECRYSTALLIC

force…tends to place itself parallel, or at a tangent, to the magnetic curve or line of magnetic force,

passing through the place where the crystal is situated” (2479).

This law was simple enough, but it involved a somewhat odd mode of behaviour. The fact that

a crystal would align itself along the magnetic lines of force (like iron) implied a polarity in the

crystalline particles themselves and in the crystal as a whole. Yet, if a crystal in a magnetic field were

turned 180˚, it would remain along the magnetic lines of force. The conclusion to be drawn was in-

escapable:

“The directing force, therefore, and the set of the crystal are in the axial direction. This force is,

doubtless, resident in the particles of the crystal.… Either end of the mass or of its molecules, is, to all

intents and purposes, both in these phænomena, and in the ordinary results of crystallization, like the

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other end; and in many cases, therefore, the words axial and axiality would seem more expressive than

the words polar and polarity (2472).”

It would be a strange sort of polarity, indeed, in which the poles were the same, but this was

what Faraday’s experiments indicated. His inability to accept this strange conclusion is shown by his

substitution of the term axial for polar… Faraday had been accustomed to think of molecular action in

terms of the polarization of particles… He was not prepared to abandon his concept simply because a

rather strange kind of polarity had become manifest.[43]

Hence, Faraday’s previous use of the term “polarity” did not well accommodate

crystallic forces. Moreover, the researcher became increasingly aware that magnetic lines of

force may not have “ends” either.

As a further setback, Faraday observed that crystallic forces do not involve contiguous

particles, his previous hallmark of polarity. Therefore, they act at a distance. Faraday explicitly

states this several times in his report.[44]

The scientist searched fruitlessly for years to locate polarity in these forces. The

chronology of his thoughts, according to L.P. Williams, was as follows: In 1848, Faraday

believed that crystallic forces were polar; by 1850, he was convinced they were not.

A Redefinition of Polarity: From Polarization of Particles to Polarization of Force Lines

Until about 1850, Faraday conceived of polarity as a molecular phenomenon, related

critically to contiguity of particles in the affected matter. (Each particle induces an opposing

state in its nearest neighbor.) But Faraday refused to part with the idea of polarity entirely, even

for magnecrystallic forces. Instead, he detached the term from the idea of contiguity. Gooding

elucidates:

[Faraday’s] inability to develop a molecular theory of the magnetic properties of crystals lead

him to abandon the notion of contiguity but not the idea that polarity is a definitive and essential

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property of force. In fact his abandonment of atomistic conceptions is made possible only when

Faraday distinguished the concept of polarity from the (less fundamental) notion of contiguity, making

polarity a property of the lines of force.[45]

Heimann further explains:

In replacing the tension and polarization of the particles of matter by the primacy of the lines of

force, Faraday was arguing that polarity did not exist as a state of matter. However, he continued to

use the term “polarity,” speaking of “the polarity of each line of force” [ERE III, § 3361], but now he

used the term to represent the direction of the lines of force, not the polarization of particles. As he

said, “My view of polarity is founded upon the character in direction of the force itself” [§ 3307].[46]

This redefinition has important consequences: First, the line or lines of force between

two bodies now have been detached from materiality of the particles themselves or of any

intervening particles. (Still, the lines of force terminate on masses of “ponderable matter.”)

Thus far, one can consider magnecrystallic action as polar under the new definition. Another

essential condition of polarity is now directionality. In contradistinction to the former

definition, though, the force need not have distinguishable ends (poles).

Here, magnetism and light definitely assumed the stature of polar forces, as Faraday

spells out in 1854.[47] But what about magnecrystallic action? The answer did not matter,

because Faraday discovered that this force was simply a special case of magnetic induction.

How the Redefinition Affects Faraday’s Conception of Force: Field Theory

Faraday had to exclude the inessential. Thus, in his previous electric-force theory, he

dismissed questions involving point atoms and concentrated on induction. Now, his updated

theory does not depend much on the nature of surrounding space. While Faraday did question

current æther theories, he did so in a speculative manner,[48] remaining ambiguous about the

12

difference between æther, attenuated matter, and lines of force.[49] He thought the actual

distinctions in question were probably “beyond the reach of experimental science.”[50]

Yet Faraday’s overwhelming urge towards unification of forces remained a crucial

impetus. The scientist’s field theory remained deficient in its treatment of mass, inertia, motion,

and in a host of other details,[51] but it achieved the aim of saving polarization, and hence

unification, as fundamental entities. While several of Faraday’s contemporaries were solving

problems using conservation of energy and of mechanical force,[52] Faraday’s world-view

would not accommodate these useful notions.[53]

Before discussing how Faraday fit gravity into his theory, it is necessary to trace some

of his conclusions about the transmission of electricity. For electricity and magnetism, the force

in question transmits in a particular direction as a wave of strain in space. The strain consists of

vibrations or undulations in a “to and fro” motion.[54] Static states correspond to a freezing or

deceleration of the vibrations. As before, inductive capacitance manifests when lines of force

are prevented from vibrating.[55] Additionally, we can make the following two conjectures

about Faraday’s theory:

First, curved lines of force are physically real entities. Previously, curved lines were

taken as proof of action via neighboring particles. Now, however, Faraday dismisses material

contiguity. In 1852, he points out the new significance of curvature: “I think the existence of

curved lines of magnetic force must be conceded; and if that be granted, then I think that the

physical nature of the lines must be granted also.” He repeats this sentiment several times.[56]

Second, since electricity (or magnetism) is a physical wave of strain in space, the

vibrations inherent in its motion must take time. That is, if the force represents actual waves, it

must propagate in actual time. Faraday may have perceived a more sophisticated argument for

13

these actions taking finite time when he described the “sluggishness” of lines of force. Berkson

has suggested that Faraday may have had in mind that, since one must attribute mass in some

sense to force, one could set mass equal to the rate of response of forces at the given point in

space. (Faraday’s vague definition of “force” need not strictly obey F = ma, but analogous

reasoning applies.) Then, “since the force point acted upon will act in turn upon its neighbours,

all changes in the field must take place at finite velocity; any disturbance in the field will take

finite time to move to a distant place.”[57]

Properties of the Unified Field

In summary, all of the forces that Faraday had successfully united by the 1850’s share

certain properties:

(1.) These forces act in curved lines. Consequently,

(2.) they are physical in character; they are not just gradients to equipotential surfaces or some

other mathematical devices. Therefore,

(3.) they travel in finite time.

Since these integrated forces are “polar,” two additional, crucial ramifications follow:

(4.) The lines of force propagate in definite direction, and consequently, the forces exist as

unidirectional strains in space. Finally,

(5.) these strains display sinusoidal properties.

One can deduce Properties 2 and 3 from Property 1. Property 4 is Faraday’s new way of

preserving the symmetrical aspect of opposing (say, +/- or N/S) poles while invoking his more

recent conception of polarity.

One can also deduce a more subtle relationship. Recall our conclusion derived from

Faraday’s first definition of polar, that “polarizability implies action via neighboring particles,

14

which in turn forbids action at a distance for such forces. (Curved lines were taken as proof of

action via neighboring particles.) Yet ‘action at a distance,’ defined appropriately, occurs for

non-polarizable forces.” Here, action at a distance is the crowning consequence of Faraday’s

“essential principle,” polarization.

Although Faraday no longer admits the contiguous-particle theory of polar force, he

nevertheless continues to associate curved (physical, temporally-propagated) lines of force with

non-distant action. Here, Faraday probably conceived of “contiguous force points.”[57a]

Space, then, would contain force points that spread force by physically disturbing

adjacent force points. Curiously, this schema reintroduces a vaguer form of contiguity. Still,

Faraday never suggested that curved lines implied local action, without at least some reference

to such contiguity. His definition of local action always included interaction between two points

separated by finite distance, as long as no other point occupied this path. This definition extends

to the new mode as well.

But does this “force point” analysis mean that polarity still causes local action? It would

seem so. After 1850, Faraday no longer conceived of a polar force as mediated by opposing

poles. Instead, the force acts along an axis that itself actually causes the dual nature of the

force.[58] Therefore, the wave of induced opposing states occurring along this axis constitutes

the sole means by which an antithetical force appears to have “poles.” Any given force point

along the axis therefore plays an integral role in transferring the very essence of the force — by

inducing its opposite state in the next point. But neighboring opposing force points necessarily

are strained, in the sense that a definite quantity of “something directional” must pass between

them. There can be no action at a distance.

15

Contrast the above with the mode of transmission of a non-polar force: There, no

successive states need be induced, and no poles need be constructed. A force point in the

vicinity of the first affected test particle will always remain in a “positive” state, just as a point

near the other affected particle will. No systematic transfer of tension occurs; hence, the

interaction between force points remains unspecified. As we have seen, Faraday did not rule out

unmediated, instantaneous propagation for such (non-polar) forces.

Berkson, however, did not consider this kind of analysis when he concluded that, for

Faraday, “all changes in the field must take place at a finite velocity; any disturbance in the

field will take finite time to move….” He assumed that all of Faraday’s force-lines were local,

non-instantaneous, and real. But, as this essay posits, only polar forces necessarily possess

these properties.

Gravitation

To his dismay, Faraday perceived two differences between gravitation and the unified

field. First, gravitational lines of action are always straight (pre-relativistically, of course).

Second, gravitation is a purely attractive force and thus does not produce opposed states. A

systematic study of Faraday’s theoretical writings from 1846 to 1859 illustrate how he made

novel assumptions about gravity in order to facilitate its incorporation into the unified field.

Williams writes that in the research reports of 1846, Faraday already thought that

gravity took time and acted locally.[59] But, in reality, Faraday’s stance was equivocal:

I am not aware whether there are any data by which it has been, or could be ascertained,

whether such a power as gravitation acts without occupying time, or whether lines of force being al-

ready in existence, such a lateral disturbance of them at one end as I have suggested above, would

require time, or must of necessity be felt instantly at the other end.[60]

16

In June 1852, Faraday retracted further, giving a view of gravity that harkened back to

the 1830’s version. Ostensibly, he remained unsure about the temporality aspect:

There is one question in relation to gravity, which, if we could ascertain or touch it, would

greatly enlighten us. It is, whether gravitation requires time…It seems equally impossible to prove or

disprove this point; since there is no capability of suspending, changing, or annihilating the power

(gravity), or annihilating the matter in which the power resides.[61]

Nevertheless, in his next paragraph he contrasts “radiation phænomena” to gravitation:

“The lines [of radiation force] require time for their propagation…in marked contrast with the

lines of gravitating force.”

Also, Faraday now declares definitively that gravity is a “pure case” of action at a

distance.[62] And, in another paper, he decides that the straight lines of gravitation are mere

abstract entities: “As far as we know at present, the line of gravitation is merely an ideal

line.”[63] Finally, Faraday endorses evidence that gravity comprises a “simple” force, as

opposed to the “dual or antithetical” force of electricity.[64]

While his June 1852 publications evinced no doubt that gravity substantially differed

from the electromagnetism/radiation group, Faraday privately expressed hope that gravity had

important similarities to that group. In a letter dated 29 January 1853, Faraday delights in his

discovery of a passage by Newton on the physicality of gravitational lines of force:

Newton’s testimony in favour of physical lines of force as regards Gravity: If that idea is

necessary to gravitation, how much more so it must be in relation to the dual powers, Magnetism and

Electricity, which act in curved lines…[65]

Thus, Faraday continued to agree that gravity-lines are straight and simple (non-polar).

Now, however, he has contradicted earlier statements, and attributed properties to gravity that

previously were associated only with polar forces. Polar forces necessarily travel via real lines

17

and act via contiguous “force points.”[66] Now, Faraday asserted, gravity also acts in real lines.

Still, he balks at giving gravity-lines as definite a quality of reality as electricity-lines (“how

much more [necessary the concept of physical lines] must be in relation to the dual powers…”).

Certainly, however, the scientist wanted to believe in the reality of gravity-lines. For all

intents and purposes, he converted by 1854. While (even in 1857) he did not directly affirm that

gravity acts in finite non-zero time, he no longer considered the question “impossible to prove

or disprove,”[67] and he implied finiteness: By 1854, Faraday has completely endorsed local

action for gravity, and he does so for the rest of his life.[68]

So, Faraday reversed his position dramatically. By the late 1850’s, he imparted the

properties of the unified force to gravity, impelled, it seems, by a far-fetched desire for

complete unification. Faraday later ignored that fact that gravity acts in straight lines. But, he

cannot ignore the absence of a fundamental unidirectionality.[69]

Nevertheless, Faraday’s comments during his failed attempt at discovering

electrogravity confirm that he had profound thoughts on a solution to this problem as well.

Electrogravity

From the first diary entry on his investigation of electogravity, in March 1849, Faraday

pondered the symmetry problem. He began:

Surely this force [gravity] must be capable of an experimental relation to Electricity, Magnetism

and the other forces, so as to bind it up with them in reciprocal action and equivalent effect…

What in Gravity answers to the dual or antithetical nature of the forms of force in Electricity and

Magnetism? Perhaps the to and fro, that is, the ceding to the force or approach of Gravitating bodies,

and the effectual reversion of the force or separation of the bodies, quiescence being the neutral

condition. Try the question experimentally on these grounds.[70]

18

Thus, he initially surmised that, in order to restore symmetry, currents may occur in two

bodies approaching from opposite directions. Yet some more generalized law is necessary, as

Faraday surely realized.

Next, Faraday speculated that gravity might gain a special symmetry at the instant when

bodies stop falling.[71] This idea presupposed that gravity would interconvert with electricity

sinusoidally. Electricity has a static state when the wave of force is frozen. If gravity also has a

frozen or neutral state, it might interconvert with a frozen electricity wave at that moment. This

theory, however, is not fully articulated.

In 1859, Faraday framed the fundamental problem in a diary entry. In it, he suggests

that either electricity must collapse into a single state or else gravity must have two opposing

states. The former possibility chafes against Faraday’s entire scheme of electricity and

polarization. He is reluctant to embrace it, but he seems open-minded about changing his whole

theory if convertibility of forces results:

The evolution of one electricity would be a new and very remarkable thing. The idea throws

doubt on the whole, but still try, for who knows what is possible in dealing with gravity?[72]

In the next paragraph, he reflects on the latter option:

The first thought would give a new relation, a relation of a dual power to a single power, which

would probably give a modification to the character of singleness supposed to belong to gravity – for it

would then be as dual as electricity.

Faraday seriously entertained the formulation of a negative or repulsive gravity. In

addition to above diary entry, he mentions the idea twice in 1857 and again in 1858. The first

reference arrives in a letter addressed to Maxwell:

All I wanted to do was move men… from the unreserved acceptance of a principle of physical

action which might be opposed to natural truth. The idea that we may possibly have to connect

19

repulsion with lines of gravitation-force (which is going far beyond anything my mind would venture on

at present, except in private cogitation), shows how far we may have to depart from the view I

oppose.[73]

In “Conservation of Forces,” Faraday is much less confident but manages to mention

the possibility.[74] Finally, C.F. Winslow, in response to correspondence from Faraday,

enthusiastically receives negative gravity. Winslow’s own theory holds that all forces represent

“secondary powers arising from two primal forces” — attraction and repulsion.[75] (Faraday

believes in but one primal force.)

Some of Faraday’s experiments even assumed that gravity has polar qualities. When he

looked for electrical currents in insulated elevating bodies, he hoped to find either positive or

negative charge induced by the loss of gravitating force,[76] presumably depending on some

potentiality in the gravity itself. He also refers to gravity as conceivably capable of inducing

change in the magnetic polarity of the earth or in other gravitating bodies.[77] Again, gravity

itself must have some non-cancelling direction in order to induce such transformations.

Finally, Faraday sees gravity as a tension in the space between gravitating particles.[78]

It has been argued that non-polar forces need not induce such tension. Once again, Faraday

attributes properties of a polar force to gravity.

On 11 April 1859, Faraday deserted his electrogravity research and turned instead to a

relationship between gravity and heat. His reasoning is intriguing:

The following point is against electricity. There is no reason why, when two bodies recede or

approach, that they should not change (if they change at all) in the same direction. But this would be

against the idea of a dual power — though not against that of a single power (so to speak), as heat.

It would be strange if a body should heat as gravitation increases by nearness of distance. We conceive

of heat as a positive force and of gravitation as a positive force…Or else heat must be negative to

20

gravity or the converse of gravity and gravity must be in the same negative or converse relation to heat.

This is against the expectation of anything from the heat experiment. Nevertheless make it, for who

knows.[79]

Clearly, Faraday knew of the critical symmetry questions plaguing electrogravity theory

and “thermogravity” theory. Yet he nonetheless persevered. He lost his direction, but his

imagination continued to provoke him. In a famous diary entry, Faraday rhapsodizes:

ALL THIS IS A DREAM. Still, examine it by a few experiments. Nothing is too wonderful to be true, if

it be consistent with the laws of nature, and in such things as these, experiment is the best test of such

consistency.[80]

Whatever the theological status of “the laws of nature,” Faraday by and large maintains

his inductivist position. According to Agassi,

Faraday says we all have methods, and this leads us to dogmatism. This is inevitable but can be

minimized — by a method. What is evil is not method but the abuse of method…. If you must

generalize… then generalize as widely or as broadly as possible because only very broad agreements

with facts give any degree of probability. This is a most unusual view in that in the name of inductive

caution it recommends boldness.[81]

“Bold” is a just epithet for Faraday’s failed synthesis of forces.

21

NOTES

[*] I composed this essay for Prof. Gerald Holton’s course in the history of science taught atHarvard University. I would like to thank Prof. Holton for his support and mentoring. For thekey concept of “themata” in science, see Gerald Holton, Thematic Origins of Scientific Thought:Kepler to Einstein (Cambridge: Harvard Univ. Press, 1973).[1] Faraday was born in 1791 and died in 1867. His made the first series of electrogravityexperiments in 1849 (published on 28 Nov. 1850) and the second series in 1859 (paper refused& withdrawn on 16 Apr. 1860).[2] Martin, Thomas, ed. Faraday’s Diary. 7 vols. London: Bell & Sons, 1932-36, (hereafterreferred to as Diary), Vol. V, § 10032. Cf. Diary VII, § 15786.[3] Faraday, Michael. Experimental Researches in Electricity. 3 vols. New York: Dover, 1965(hereafter referred to as ERE), Vol. 3, § 2717.[4] ERE, p. 573 (“Points of Magnetic Philosophy,” Jan. 1855). Faraday actually referred to thehypothetical gravity-electricity relation as “gravelectricity.” Diary V, § 10132. I use the moremodern and mellifluous term, “electrogravity.”[5] Levere, T.H. “Faraday, Matter and Natural Theology: Reflections on an UnpublishedManuscript.” Brit. J. Hist. Sci. 4 (1968-69), pp. 102-3; Williams, p. 103.[6] Agassi, Joseph. Faraday as a Natural Philosopher. Chicago: Univ. of Chicago Press, 1971,p. 27. See also Agassi, p. 32; and Williams, L.P. Michael Faraday. New York: Basic Books,1965, p. 84.[7] Agassi, p. 135.[8] Berkson, William. Fields of Force: Development of a World View from Faraday to Einstein.New York: Halsted, 1974, p. 57.[9] Diary VII, § 15809.[10] Agassi, p. 160.For more discussion of Faraday’s methodology, see, for example, Agassi, pp. 30-32, 127-140,157-163; Williams, pp. 334-337, 460; and Segrè, Emilio. From Falling Bodies to Radio Waves:Classical Physicists and Their Discoveries. New York: Freeman, 1984, pp. 132-155.[11] Diary V, § 10061 (25 Aug. 1849).[12] For a discussion of Faraday’s experimental designs, see Williams, pp. 465-71.[13] Faraday to Maxwell, 13 Nov. 1857, in Williams, L.P. Selected Correspondence ofFaraday. 2 vols. Cambridge: Cambridge Univ. Press, 1971, (hereafter referred to asCorrespondence), Vol. II, p. 884.[14] Berkson, p. 123.[15] Gooding, David. "Empiricism in Practice: Teleology, Economy, and Observation inFaraday's Physics." Isis 73 (1982), pp. 46-67.[16] Id.[17] Levere, p. 103.[18] Gooding, David. “Metaphysics Versus Measurement: The Conversion and Conservation ofForce in Faraday’s Physics.” Ann. Sci. 37 (1980). One force may seem to be destroyed: Forexample, when two bodies are moved apart, the gravitational attraction between them lessens.This decrease must be accompanied by an increase in a corresponding force, e.g., in electricalaction. Thus, gravity and electricity must interconvert, and together, as manifestations of asingle unified force, remain conserved. For Faraday’s ignorance of potential energy, see note 51below.

22

[19] Levere, pp. 100, 103.[20] Faraday, Michael. “On the Conservation of Force.” Phil. Mag. 13 (1857), p. 227. Myemphasis.[21] “On the Conservation of Force,” 1857, pp. 229, 234.[22] Faraday, Michael. "On the Conservation of Force." Phil. Mag. 17 (1859), pp. 166-169.[23] ERE, Series 11, introduction. See also ERE I, § 1161; Diary II, §§ 1780-1788.[24] ERE I, § 1162.[25] Berkson, p. 33.[26] Faraday to Whewell, 13 Dec. 1836, in Correspondence I, p. 306.[27] ERE, Series 15.[28] p. 237.[29] Letter to Faraday, 9 Nov. 1857, quoted in Williams, p. 512. A complete text with diagramcan be found in Correspondence II, pp. 881-883.[30] For example, Agassi, p. 312; Williams, p. 506.[31] Diary II, § 3425, quoted in Williams, p. 291.[32] See, for example, Williams, Ch. 7.[33] Gooding, David. “Conceptual and Experimental Bases of Faraday’s Denial of ElectrostaticAction at a Distance.” Studies Hist. Philos. Sci. 9 (1978), p. 124, n. 37.[34] “Faraday regards neither the direct action (through the vacuum) nor the indirect action(through the insulator) as actions at a distance because both are contiguous actions… Hishypothesis of contiguity does not preclude interactions between any two particles (call themx,y) separated by a finite or ‘sensible’ interval (xy) provided that there is no other point (z)occupying this interval.” [Gooding, 1978, p. 124.][35] Williams, p. 81.[36] Heimann, P.M. “Faraday’s Theories of Matter and Electricity.” Brit. J. Hist. Sci. 5 (1971),pp. 235-257.[37] Gooding, 1978.[38] But see Agassi, esp. pp. 79-80, 209, 312; Berkson, e.g., p. 114.[39] Diary III, § 4029.[40] Diary III, § 3512. Emphasis in original.[41] Spencer, J. Brookes. “On the Varieties of Nineteenth-Century Magneto-OpticalDiscovery.” Isis 61 (1970), pp. 34-51.[42] Williams, p. 460, n. 10. Light is “polarizable” in the modern sense, but its lines of force donot have “poles,” or ends, such as + and – for electricity. According to Segrè [p. 151], Faradayhad “deep insight in the electromagnetic nature of light.” This insight comes during and afterFaraday’s redefinition of polarity to incorporate light and magnetism. See his discussions ofradiation, 1854–.[43] Williams, pp. 417-418. Emphasis in original; my ellipses.[44] ERE III, §§ 2564, 2568, 2578.[45] Gooding, 1978, p. 130.[46] Heimann, 1971, p. 256. Emphasis in original.[47] ERE III, §3324 etc. (Dec. 1854.)[48] Agassi, p. 311; Williams, p. 454.[49] Agassi, p. 225 ff.; Berkson, p. 99; Gooding, “Final Steps to the Field Theory: Faraday’sStudy of Magnetic Phenomena, 1845-1850.” Hist. Studs. Phys. Sci. 11 (1981), pp. 253, 267,esp. n. 91-92; Williams, pp. 380, 454-466; ERE III, pp. 447-452 (“Thoughts on Ray-

23

Vibrations,” May 1846).[50] Gooding, 1981, p. 267, n. 140. In “Thoughts on Ray Vibrations,” Faraday speculated aboutthe need for æther, in an effort to join electromagnetism with light and heat.[51] Faraday’s field theories were marred by lack of clarity. He does not show how forcesdistribute themselves around a center of force, or how mass relates to force. Berkson [p. 54]asks, “How do material bodies, the places where lines of force converge, keep their identity astime passes?” Faraday remained vague about the answer. Further, he understood inertia as aseparate force, and hence could not deduce the nature of matter or momentum [Berkson, p. 116ff.; Agassi, p. 232.] He made no distinction between potential and actual cause, thusmisunderstood kinetics, nor did he clarify the difference between “quantity” and “intensity” offorce [Gooding, 1980, p. 11-24]. In other words, and as hinted above, Faraday did notunderstand or adopt the “very new” idea [as of 1849] of potential and kinetic energy [Williams,p. 466]. Finally, he never put his work into the mathematical notation necessary for discoursewith other theorists [e.g., Agassi, p. 306].[52] Heimann, P.M. “Conversion of Forces and the Conservation of Energy.” Centaurus 18(1974), pp. 147-161.[53] Faraday refused to distinguish between energy and force conservation. For a discussion,see Berkson, pp. 119-123. Crosbie W. Smith suggests that Faraday rejected Joule’s idea of theequivalence of heat with mechanical force because Faraday was “deeply committed to hisprinciple of conservation of force” [Smith, Crosbie W. “Faraday as a Referee of Joule’s RoyalSociety Paper ‘On the Mechanical Equivalent of Heat.’” Isis 67 (1976), pp. 444-449.][54] Diary V, §§ 10624-10625.[55] Cf. Williams, p. 459, and other general sources, for interpretations of this model.[56] ERE III, § 3297. See also §§ 3254, 3258, 3261, 3263-3264.[57] Berkson, p. 52. Emphasis in original.[57a] Cf. id. Yet I criticize Berkson below for his mistaken conclusion that Faraday’s lines offorce were conceived as local, non-instantaneous, and veridical.[58] Cf. Gooding, 1978, p. 140 ff.[59] Williams, pp. 380-381.[60] Faraday’s Experimental Researches in Chemistry and Physics, p. 371; quoted in Williams,p. 381.[61]ERE III, § 3246.[62] ERE III, § 3245.[63] ERE III, p. 439 (“On the Physical Lines of Magnetic Force,” June 1852).[64] ERE III, § 3248.[65] Faraday to Whewell, 29 Jan. 1853, in Correspondence II, p. 683. Faraday refers toNewton’s Third Letter to Bentley. An appropriate section of Newton’s letter is quoted inFaraday, “On the Conservation of Force,” 1857, p. 232, n. 2, and also in ERE III, § 3305 (Dec.1854).[66] While Faraday did not consistently employ this terminology, one may adopt it as anapproximation to what Faraday had in mind.[67] Compare his 1852 statements with “On the Conservation of Force,” 1857, esp. p. 226,where Faraday denies that the question of time is purely metaphysical.[68] See letter to Matteucci, 2 Nov. 1855, quoted in Agassi, p. 330; ERE (Dec. 1854), op. cit.;and “On the Conservation of Force,” 1857, p. 232.[69] Gravity has but one state — attractive — and the lines of gravitation between any two

24

centers point equivalently in both directions.[70] Diary V, §§ 10018-10019 (my emphasis); paraphrased in ERE III, § 2703. Cf. Diary V, §§10934-10935.[71] Diary V, §§ 10038-10039, 10109, 15828.[72] Diary VII, § 15795 [10 Feb. 1859].[73] Faraday to Maxwell, 13 Nov. 1857, in Correspondence II, p. 885. Emphasis in original.[74] “On the Conservation of Force,” 1857, p. 237; p. 238.[75] Winslow to Faraday, 5 Nov. 1858, in Correspondence II, pp. 915-917.[76] ERE III, Series 24; Diary VII, §§ 15786-15790.[77] Diary V, §§ 10085-10090.[78] Williams, pp. 459, 468.[79] Diary VII, §§ 15914-15915. Thermogravity experiments: §§ 15916-15985.[80] Diary V, § 10040.[81] Agassi, p. 31.

25

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