THE ETHER AND ITS FUNCTIONS.
By Professor GEORGE FRAZER FITZGERALD, 1890?
"All are but parts of one stupendous whole
Whose body nature is, and God the soul."
When we more carefully consider matters, however, we must concede
that this way of speaking does not accurately represent even the
popular view of nature. Still less does it represent the view that must
be taken by every diligent observer and accurate thinker. In the case
of an empty room, everybody acknowledges that it is really full of air,
and that to speak of it as empty is not absolutely accurate, though
sufficiently so for ordinary purposes. It does not deceive those whom
we are speaking to. Quakers even have not objected to use the term. It
is defensible on the same plea as stating that one is "Not at home."
Neither statement is verbally accurate, but neither statement deceives,
and each is, in consequence, quite legitimate. It does not appear at
first sight, however, that there is any obvious way in which it is
inaccurate to speak of interstellar space as empty. There are, no
doubt, stars and comets and nebulae and meteors, but between them
surely space is empty. And yet even popularly a place is spoken of as
"full of light." Surely the space all round the sun is "full of light."
Can we, with perfect accuracy, speak of a space as empty which is full
of light?
There have been several theories as to the nature of this light
that fills space. At one time it was supposed to be some sort of
process or feeler that was projected out of peoples eyes by which they
felt objects. What the cause of day and night can be, seems a serious
difficulty to this hypothesis. It would, anyway, justify the suggestion
as to the uselessness of the sun which came, out by day, though it
would hardly explain the usefulness of the moon. This view is not even
held by "cranks" nowadays. Light is attributed to the sun, to lamps, to
candles, and not to the eyes of the observer. Metaphysicians may ask
for the sense in which one can speak of light being present without an
observer, but even in this age of skepticism, these very important
metaphysical questions have not yet attracted popular attention. We are
content to assert that in some sense or another we are justified in
speaking of light being due to the sun, or a lamp.
A more recent view was that light was due to small particles
emitted by bright bodies. This was a hypothesis with many things to
recommend it. In this case it was certainly inaccurate to speak of
interstellar space as empty. It must be choked full of these minute
particles, hurrying about in all directions at the almost inconceivable
rate of one hundred and ninety-two thousand miles a second. Can a space
thus actively occupied be accurately described as empty? Even in the
shadow of the earth there must be innumerable such particles. The stars
are shining there. The earth itself must be emitting immense numbers of
them, for we know that it is cooling all night, and the phenomenon of
giving out heat by radiation is essentially the same as that of giving
out light by radiation. There are, however, several very serious
difficulties in the way of believing this hypothesis. One of the most
serious is that one must suppose, upon this hypothesis, that the light
travels more quickly in water than in air, while it has been proved by
a direct experiment that light travels more slowly in water than in
air. There are, in addition, several other difficulties in this
hypothesis. Very curious and rather inexplicable fits of easy
reflection and easy transmission have to be attributed to these light
particles. In order to explain them, Sir Isaac Newton suggested that
all space was full of a fluid which in some way caused these
inexplicable fits. Such a suggestion almost surrendered all ground for
the hypothesis that there were any light particles at all. Once it is
conceded that there is a medium filling space, why not attribute light
to the vibrations of this medium in the same sort of way as we
attribute sound to the vibrations of the air? This is, in fact, the
hypothesis now held, and while it explains almost every fact connected
with light, there are no known facts necessarily inconsistent with it.
Still, there are people who do not believe in this medium. They
seem to think that the sun may act upon us here without any intervening
medium. Such people do not appreciate the difficulty in thus explaining
what becomes of the action during the eight minutes it takes to reach
the earth after it has left the sun. The light takes eight minutes to
pass over the intervening space. What is it during, these eight
minutes? One view was that it existed as small particles traveling with
an enormous velocity. This hypothesis is untenable because it does not
explain a number of other light effects. The other view is that it
exists as some sort of periodic change in structure of an intervening
medium which is called a wave of light in the ether. This is consistent
with all known phenomena, and no other hypothesis has as yet been
published which has been shown to explain in an intelligible way the
phenomena of light.
But there are other phenomena due to the air, for instance, in
addition to sound. It has chemical actions, it can blow things about by
winds, it can burst strong vessels by its pressure. Are there no
phenomena due to the ether except light? Surely a medium whose
vibrations are so important can hardly fail to possess other
properties. Lord Salisbury, no doubt, said in his inaugural address
last year, as President of the British Association at Oxford, that the
only function of the ether was to undulate. This was a most
extraordinary mistake for even a politico-scientist to make. It is one
of the glories of British science that by Faraday and Clerk Maxwell a
sure foundation has been laid for the theory that electric and magnetic
forces are due to the ether. Its only function is to undulate! One
might as well say the same of the atmosphere or of the waters of the
sea. No doubt the undulatory, electric and magnetic properties of the
ether require us to suppose a very much simpler nature for the ether
than for any known form of ordinary matter. Ordinary matter, with which
we are so familiar that we treat its wonders with contempt, is
fearfully and wonderfully complex. We cannot hope to explain the
innumerable properties of air, for instance, which is quite a simple
form of matter compared with most other commonly occurring forms,
without attributing to it some very complicated structure. The
properties of the ether are so simple that there is every hope that we
may be able to explain its properties by attributing to it a simple
structure. So far as is known we need only attribute to it the ability
to produce electric force and magnetic force in order to explain all
the phenomena which can be repeated in any properly equipped
laboratory. It is as if we had an invisible bar by means of which we
could either push or pull or twist objects at a distance. These are
very simple operations, and if they were the only ones that the
invisible bar could perform we might very fairly describe it as
possessed of very simple properties. No real ordinary matter is so
extraordinarily simple as that.
A solid glass bar, for instance, would prevent our pushing our
fingers across it; it would bend light that passed through it; it would
reflect light from its surface; it would absorb heat; it could be
melted if raised sufficiently in temperature; it could be acted upon
chemically by hydrofluoric acid; and it would possess innumerable other
important properties, so that we could hardly fairly describe it as
possessed of very simple properties. Of course no one can prophesy that
there may not be found many other important properties of the ether
which may show it to be very complicated. The very fact that matter is
so complicated, and that ether is so intimately connected with matter,
shows that the ether may be very complicated too. At present, however,
it seems as if these complications were due to the complex nature of
matter, while a comparatively simple ether would suffice to explain all
we know.
In the beginning of science it was difficult for people to believe
that we were living at the bottom of an ocean of air. Winds were looked
upon as subtle entities rather than as movements of the air. The rising
of water in pumps was ascribed to an unexplained natural principle of
abhorrence of a vacuum. In a similar way we have, until within the last
few decades, been content to explain electric and magnetic forces by a
natural principle of attraction of electricity and magnetism. As soon,
however, as the existence of winds and the rising of water in pumps,
the height of the barometer, and the flight of balloons were all
explained by the varying pressures in an ocean of gas, people gave up
their former obviously unsatisfactory and provisional explanations, and
nobody now doubts the theory that these phenomena are all due to a
medium whose vibrations constitute sound. All these properties have
been shown to be consistent properties of a single medium, and
consequently nobody doubts of the existence of this medium. We now are
persuaded that we feel this medium when the wind blows us; we see its
action when balloons rise; we hear its vibrations in sound. In a
similar way electric, magnetic and light phenomena are all consistent
properties of a single medium, and consequently no one should doubt of
the existence of this medium. We should feel this medium when a magnet
pulls at a piece of iron we hold; we should see its action in a flash
of lightning; we should see its vibrations in light.
But, it may be said, nobody has been able to explain these
properties? Well, neither has anybody been able to explain the
properties of the air. Some of the simpler properties of the air can,
no doubt, be explained by supposing it to consist of countless small
elastic particles of different sizes and weights jostling one another
about. The elasticity of these particles is, however, unexplained, and
a great many of their properties, notably the whole series of these
chemical properties, are still in that obviously provisional condition
of being described as simply properties of doing this, that and the
other. The electric, magnetic and luminous properties of the ether are
very much simpler than the innumerable properties of air, and it is
consequently not unreasonable to expect that they will be explained,
and it is consequently unreasonable to doubt of the existence of the
ether because of its possessing unexplained properties, while we have
no doubt of the existence of air though it possesses very many more
unexplained properties.
Several directions have been suggested in which we may look for
explanations of the simple properties of the ether. It has been
suggested that it may consist of particles somewhat like those of a
gas, only very much smaller and moving, about with very much greater
rapidity. It has not, however, been fully shown how this hypothesis can
explain the electric and magnetic properties of the ether. Others have
gone to the opposite extreme, and supposed that the ether may consist
of smooth hard particles almost completely filling space, instead of
being very small compared with their distances apart. These particles
are supposed to slide or roll over one another so freely that they
practically offer no resistance to matter moving among them. This seems
in many ways a rather hopeful direction in which to look for an
explanation of the properties of the ether. It has not, however, been
fully worked out, though Prof. Hertz has shown, in his posthumous work,
that such a supposition is not inconsistent with what we know of
electric and magnetic actions, for he attributes all dynamical actions
in nature to actions of this kind. It was the direction in which Clerk
Maxwell sought for a dynamical, material system that would possess the
same sort of properties as he showed that the ether must possess.
All these theories depending on the existence of hard bodies in
space, whether like gaseous atoms they have large distances between
them, or like the second hypothesis they have small distances between
them, labor under the disadvantage of postulating the existence of
these hard bodies without offering any explanation of the cause of
their hardness, etc. A hypothesis like Lord Kelvins, that material
atoms are vortex rings in a continuous incompressible medium, only
postulates the existence of this continuous incompressible medium. From
this one postulate, and the hypothesis that its various parts are
moving in a variety of ways consistent with the postulate, it can be
shown that indestructible atoms could exist. It does not seem
impossible that all the complexities of nature may be explicable by
this hypothesis. A being living in the midst of an infinite ocean of
liquid, which was perfectly transparent and at rest, might never
discover its existence, just as mankind lived for generations inside an
ocean of air without fully realizing its existence, even though they
had plenty of motion in the winds to help them. Such a being might be
supposed some day to meet a great whirlpool and thus become suddenly
alive to the existence of the medium around him. He would probably, at
first, think of the whirlpool as an independent entity. He would,
however, ultimately find that its effects extended to all places he
could reach. No doubt, at a distance from the whirlpool, its effects
would be very small, while near to it its actions would be so
tremendous that maybe he could never get quite close to its central
core. With this evidence before him, would not such a being be
justified in supposing that this active thing was a kind of movement in
a medium extending throughout all the space he could reach? We find a
very similar state of affairs near atoms of matter. They have a central
region where their action is so intense that we have no evidence that
we can penetrate it. Around this and extending throughout space,
diminishing in intensity the further we go from this central core, are
actions accompanying this atom. Close in there are chemical actions. It
may have electrical and magnetic actions. It always has gravitational
action at all places, at least as far as the solar system extends. Is
it then irrational to suppose that these atoms are themselves really
only a particular kind of motion in a medium that fills all space? In
order that an incompressible liquid should be able to transmit actions
such as gravity, electric and magnetic force, light, etc., it must
itself be full of motion. Lord Kelvin has shown that certain kinds of
disturbances might be propagated in a manner somewhat similar to light
vibrations, by a liquid whose parts were in intense motion. In order
that the action may be propagated rapidly, the motion of the liquid
must be very intense. The average speed of the motion of its parts must
be comparable with that of the propagation of the disturbance. In the
case of light propagation this is very great. Light goes one hundred
and ninety-two thousand miles in a second. The parts of the medium must
consequently be moving on the average with a velocity comparable with
this. Some years ago, Prof. DeVolson Wood proposed to calculate the
average velocity of the parts of the ether in a somewhat similar way.
There was, at that time, a very serious objection to this. Prof. Wood
was applying the theory of gases to this case. Now, though there its
some similarity between the cases, there is an essential difference.
Disturbances, such as sound waves, are propagated by the compression
and rarefaction of a gas. Light is known to be propagated by some other
kind of action, we dont know exactly what, but it certainly is not by
compressions and rarefactions in the ether. It was, consequently, quite
illegitimate to apply a calculation which was only known to be true of
this kind of motion to quite a different kind of action. Before such a
proceeding would become in any way justifiable, it was necessary to
prove that this quite different kind of action could be propagated at
all by a medium whose parts were in intense movement, and Prof. Wood
had not at that time shown reason for believing this.
If the parts of the medium are really moving at these tremendous
speeds, every cubic foot of the medium must have some energy in it. If
the medium be at all dense, the energy of its motion will be very
large. Each cubic foot might, for instance, be looked upon as a cubical
box containing whirling wheels. If the wheels are massive, and whirling
with tremendous rapidity, there will be a great deal of energy in the
box. If the wheels are very light, there will not be very much energy,
even though they are whirling very rapidly. Can we make any estimate as
to whether the medium is rare or dense? Most of the estimates that have
been made lead to the conclusion that it is very rare. They each depend
upon some unproved assumption. We have no conclusive proof as to the
density of the medium. It is generally thought that, because we do not
directly perceive the medium, it must be very rare. This is by no means
the case. To return to the being immersed in the ocean of liquid, be
was unable to perceive. Whether it were a dense liquid or no, would not
make any difference to him. If it were dense, he would, no doubt, in
moving his limbs, feel that he had to exert himself a good deal in
order to start them moving on account of all the surrounding liquid be
would have to set moving. If he was suddenly transferred to a very rare
medium, he would perceive the difference. Like the ancient mariner, he
"felt so light, almost," "he thought that he had died in sleep," "and
was a blessed ghost." But then this was supposed not to be one of the
experiences of this being. He was always accustomed to have to move all
this dense medium whenever he moved his limbs. In fact, he had never
attributed this inertia to the medium at all. He had always attributed
it to his limbs. In a similar way we, when we move a stone or a bit of
lead or platinum, attribute its inertia to the body moved, while really
the inertia may be due to the medium we move along with the body. This
must actually be the case if the hypothesis already mentioned, as to
the nature of matter, be true. If matter be itself only a part of the
medium, which is possessed of some peculiarity of motion, then the
inertia of matter is merely the inertia of the medium itself. If this
be so, it would appear as if the medium must be at least as dense as
platinum. When we move a piece of platinum, we may not move all the
medium inside it, and in that case the density of the medium may be
much greater than that of platinum. There is nothing certainly known to
disprove such a hypothesis. If, for instance, the medium be five times
as dense as platinum, i.e., about one hundred times as dense as water,
all that it would require would be that when we move water about we are
only moving the one-hundredth part of the medium that occupies the
space of the water, and this does not seem at all an impossible
hypothesis. If this be so, how much energy may there be in one cubic
foot of ether? There will be about one hundred million of million of
million foot pounds of energy. This would supply a million horse-power
for five thousand years. Such a calculation as this does not pretend to
prove that there is this energy in each cubic foot of the ether. All it
pretends to is to show that in our present desperate condition of
ignorance, we know nothing with absolute certainty that disproves the
possibility of this energy being there.
Is this energy available? Well, it is not safe to prophesy what is
and what is not possible. Most prophesies as to what is and what is not
possible have proved untrue. Until, however, we have discovered how to
utilize the immense known stores of energy in each cubic foot of gross
matter, in the earth, in the water of the sea, and in the air about us,
energy whose nature is pretty well known and whose amount we can
approximately estimate, until we have found out some way of doing this,
it seems very unlikely that we shall be able to utilize the energy of
the ether, even if we are right in our hypothesis that it exists.
Each cubic yard of air possesses more than four foot tons of
energy, owing to the motion of its molecules, and yet we have not found
out any way of using this. If we could only catch hold of whichever of
the molecules we wished and harness them to a car, and let these go
when we had got all the energy out of them we required and harness up
fresh molecules, it would enable us to use this energy. The discovery
of how to use the chemical energy of coal would be absolutely nothing
compared with this. It has been suggested that some of the minuter
bacteria are able to do this. Is it impossible that larger organisms
may be able to do it? Is it impossible that they may develop the
ability thus to sort out the molecule they require in their own
superficial cells? If bacteria have developed this ability in their
cells, may not mankind by judicious selection or by other means attain
a similar ability? We could easily fly then; we could do many other
wonderful things. We may fly before that. A surface set suddenly in
motion with a velocity greater than that of sound in air would, at
least temporarily, have a pressure of nearly fifteen pounds per square
inch on its surface, and an area of twelve square inches would then
support a heavy man. This is, however, quite beside the matter in hand.
And what is all this fierce motion in space which we desire to
direct in accordance with our wishes? How do we now direct motion in
accordance with our wishes? Is there any motion directed in accordance
with our wishes? Certainly there is, if "in accordance with our wishes"
has any real meaning. We can often direct the motions of our limbs in
accordance with our wishes. By experience gained in childhood, by
carefully conducted education, by following the experience of others,
we direct many, very many, motions outside our bodies in accordance
with our wishes. We do this by learning what we call the law of nature,
or the rules of that great organism with which we have to work, and
accommodating ourselves to them. But what is the "we" and what are "our
wishes?" What is the "I" of another person? In old times people used to
attribute feelings and sensations and thoughts to the heart, liver,
spleen, etc. Nowadays we locate all these in the brain. Why? Because we
find that an animal can get along very comfortably without a liver or
spleen for a short time, so long as its nervous system, of which the
brain is such an important center, is kept in working order. So long as
the brain is in working order a person can feel and think. If it is out
of order or improperly supplied with blood the feeling and thinking are
disordered. There is every reason to suppose that our feeling of light
is concerned with one series of brain cells, our feeling of sound with
another; that so long as we feel light there are certain changes, i.
e., movements going on in one set of brain cells; while we are
conscious of beauty some kind of change is going on, maybe not only in
our brain cells but a concomitant change affecting our whole system.
Somebody has recently shown reason to suppose that angry passions
produce a poison which disorders the digestive system. It is quite
likely, after all, that the spleen may be concerned in these things,
and the liver too. Anyway, what is of importance at present is that the
only way in which another persons angry passions exist as a reality for
me are as very complicated movements in their organism. We do not know
what movements in the brain cells correspond to the sensation of red
light, nor what to a shrill sound. Neither movement is probably one bit
like the vibrations of the eye molecules, nor of the ear molecules,
that excite the cell motions. A waving flag may signal to a general
information as to an enemys manoeuvers which leads him to rearrange his
infantry, cavalry, and artillery. But these movements of his army are
not a bit like the waving flag which started them. We can, however,
trace a connection between them. They are things of the same kind. They
are both movements of matter. Similarly, the movements of the ear-drum
and those of the brain molecules are things of the same kind. Every
action I can perceive in another person is of this same kind. But the
shrill sound I perceive is not of this same kind. Ugliness and
guiltiness are not movements of matter. But then I can not perceive the
shrill sound that another person feels. We may both, no doubt, in a
colloquial sense, hear the same sound, but I am not conscious of the
other persons feeling. The same source causes two feelings, one in me,
the other in the other person. I feel my own feeling, I cannot feel the
other persons feeling. The only way in which the other persons feeling
exists for me is as a movement in his brain, the only way in which my
feeling exists for him is as a movement in my brain. We know as yet no
way of getting behind this. There seems every reason to think that what
is behind this movement may be as complicated as the army manoeuvers
compared with the waving of a flag. It is hard to see how otherwise to
explain the fact that brain movements can correspond to such a variety
of feelings as light and sound, beauty and ugliness, goodness and
guilt. It is well to call all these "feelings," notwithstanding the boy
who defined an abstract term to be a thing like conscience that one
cannot feel. It is always necessary to recollect that to me these
feelings are the only reality; other peoples feelings are to me an
elaborate and frequently erroneous inference.
One of the most interesting investigations of the present day is as
to the positions of atoms in molecules. The whole system is too small
to see. We can form some rough conception of their arrangement from
their behavior, just as we can form an estimate as to the orbit of a
double star from the changes, in its spectrum, even though the
components are far too close to be separately visible. We are gradually
learning how to read, in the spectrum, the story of what is taking
place in molecules, too. There is some prospect that we may some time
even be able to tell what movements in the brain cells correspond to a
sensation of red light, and, if the world lasts long enough, and
mankind is good enough, we may be able to discover what movements in
his system corresponded to Wilberforces determination to put down
slavery.
But if the spleen is involved in angry passions, it is evident that
motions outside our brain and even our nervous system are involved in
feelings and thoughts. Where does our brain end? Where does movement
cease to have a corresponding thought? Surely all movement must have a
corresponding thought. And perchance when we know the movements
corresponding to a determination to abolish slavery we may be able to
form some dim conception of the thoughts that correspond to the
movements of the earth, of the solar system, to the development of
species of animals and plants. These thoughts will not be our thoughts,
nor our ways their ways. That they are not does not necessarily place
them beyond investigation. We already know much about four dimensional
space, and can state things true of multi-dimensional space, though
even of four dimensional space we can form no concrete conception. In
the same way we may hope some time to make scientific statements about
the thoughts of the universe, though we may be quite unable to
reproduce them as our thoughts. Even now we deal with the universe as
with a person. How do we get others to do what we wish? By making them
feel our wishes directly? No. By paying attention to the laws of their
nature and by so acting ourselves as to cause them to act as we wish.
Is not that also a description of how we act on nature? How do others
act on us? By speaking to us with signs. Does not nature speak to us in
the same way? We interpret other peoples signs and judge that they have
corresponding thoughts. Are we then wrong in considering the signs of
nature as the language in which the thoughts of nature are expressed?
All the greatest, wisest, best have implored and exhorted mankind
to believe this. Prophets and seers, philosophers and poets, have
taught mankind this faith. We have faith in the existence of the
thoughts corresponding to other peoples brain-movements. Without this
faith life would be a mockery. Is it not almost a mockery without the
greater faith? The greatest, wisest, best have said so. It is the
almost necessary conclusion of science. Science has by itself no proof
of the existence of other peoples thoughts. Science then cannot be
expected to prove the existence of these thoughts more complex, indeed,
than other peoples thoughts, but which can, for all that, be safely
called thoughts. Do we not show our wisdom by holding fast by the
teaching of the greatest, the wisest and the best? Is it not the most
glorious prospect for science that it may one day give a definite form
to the greatest thoughts of mankinds greatest sons ?