THE HIGHEST AIM OF THE PHYSICIST[1]




PROFESSOR HENRY A. ROWLAND




SCIENCE


EDITORIAL COMMITTEE: S. NEWCOMB, Mathematics; R. S. WOODWARD, Mechanics;
E. C. PICKERING, Astronomy; T. C. MENDENHALL, Physics; R. H. THURSTON,
Engineering; IRA REMSEN, Chemistry; J. LE CONTE, Geology; W. M. DAVIS,
Physiography; HENRY F. OSBORN, Paleontology; W. K. BROOKS, C. HART MERRIAM,
Zoology; S. H. SCUDDER, Entomology; C. E. BESSEY, N. L. BRITTON, Botany;
C. S. MINOT, Embryology, Histology; H. P. BOWDITCH, Physiology; J. S.
BILLINGS, Hygiene; J. MCKEEN CATTELL, Psychology; J. W. POWELL,
Anthropology.


AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE

FRIDAY, DECEMBER 8, 1899





GENTLEMEN AND FELLOW PHYSICISTS OF AMERICA: We meet to day on an
occasion which marks an epoch in the history of physics in America; may
the future show that it also marks an epoch in the history of the
science which this Society is organized to cultivate! For we meet here
in the interest of a science which above all sciences deals with the
foundation of the Universe, with the constitution of matter from which
everything in the Universe is made and with the ether of space by which
alone the various portions of matter forming the Universe affect each
other even at such distances as we may never expect to traverse,
whatever the progress of our science in the future.

We, who have devoted our lives to the solution of problems connected
with physics, now meet together to help each other and to forward the
interests of the subject which we love. A subject which appeals most
strongly to the better instincts of our nature and the problems of which
tax our minds to the limit of their capacity and suggest the grandest
and noblest ideas of which they are capable.

In a country where the doctrine of the equal rights of man has been
distorted to mean the equality of man in other respects, we form a small
and unique body of men, a new variety of the human race as one of our
greatest scientists calls it, whose views of what constitutes the
greatest achievement in life are very different from those around us. In
this respect we form an aristocracy, not of wealth, not of pedigree, but
of intellect and of ideals, holding him in the highest respect who adds
the most to our knowledge or who strives after it as the highest good.

Thus we meet together for mutual sympathy and the interchange of
knowledge, and may we do so ever with appreciation of the benefits to
ourselves and possibly to our science. Above all, let us cultivate the
idea of the dignity of our pursuit so that this feeling may sustain us
in the midst of a world which gives its highest praise, not to the
investigation in the pure etherial physics which our Society is formed
to cultivate, but to one who uses it for satisfying the physical rather
than the intellectual needs of mankind. He who makes two blades of grass
grow where one grew before is the benefactor of mankind; but he who
obscurely worked to find the laws of such growth is the intellectual
superior as well as the greater benefactor of the two.

How stands our country, then, in this respect? My answer must still be,
now, as it was fifteen years ago, that much of the intellect of the
country is still wasted in the pursuit of so-called practical science
which ministers to our physical needs and but little thought and money
is given to the grander portion of the subject which appeals to our
intellect alone. But your presence here gives evidence that such a
condition is not to last forever.

Even in the past we have a few names whom scientists throughout the
world delight to honor. Franklin, who almost revolutionized the science
of electricity by a few simple but profound experiments. Count Rumford,
whose experiments almost demonstrated the nature of heat. Henry, who
might have done much for the progress of physics had he published more
fully the results of his investigations. Mayer, whose simple and
ingenious experiments have been a source of pleasure and profit to many.
This is the meager list of those whom death allows me to speak of and
who have earned mention here by doing something for the progress of our
science. And yet the record has been searched for more than a hundred
years. How different had I started to record those who have made useful
and beneficial inventions!

But I know, when I look in the faces of those before me, where the eager
intellect and high purpose sit enthroned on bodies possessing the vigor
and strength of youth, that the writer of a hundred years hence can no
longer throw such a reproach upon our country. Nor can we blame those
who have gone before us. The progress of every science shows us the
condition of its growth. Very few persons, if isolated in a
semi-civilized land, have either the desire or the opportunity of
pursuing the higher branches of science. Even if they should be able to
do so, their influence on their science depends upon what they publish
and make known to the world. A hermit philosopher we can imagine might
make many useful discoveries. Yet, if he keeps them to himself, he can
never claim to have benefited the world in any degree. His unpublished
results are his private gain, but the world is no better off until he
has made them known in language strong enough to call attention to them
and to convince the world of their truth. Thus, to encourage the growth
of any science, the best thing we can do is to meet together in its
interest, to discuss its problems, to criticize each other's work and,
best of all, to provide means by which the better portion of it may be
made known to the world. Furthermore, let us encourage discrimination in
our thoughts and work. Let us recognize the eras when great thoughts
have been introduced into our subject and let us honor the great men who
introduced and proved them correct. Let us forever reject such foolish
ideas as the equality of mankind and carefully give the greater credit
to the greater man. So, in choosing the subjects for our investigation,
let us, if possible, work upon those subjects which will finally give us
an advanced knowledge of some great subject. I am aware that we cannot
always do this; our ideas will often flow in side channels; but, with
the great problems of the Universe before us, we may sometime be able to
do our share toward the greater end.

What is matter; what is gravitation; what is ether and the radiation
through it; what is electricity and magnetism; how are these connected
together and what is their relation to heat? These are the greater
problems of the universe. But many infinitely smaller problems we must
attack and solve before we can even guess at the solution of the greater
ones.

In our attitude toward these greater problems how do we stand and what
is the foundation of our knowledge?

Newton and the great array of astronomers who have succeeded him have
proved that, within planetary distances, matter attracts all others with
a force varying inversely as the square of the distance. But what sort
of proof have we of this law? It is derived from astronomical
observations on the planetary orbits. It agrees very well within these
immense spaces; but where is the evidence that the law holds for smaller
distances? We measure the lunar distance and the size of the earth and
compare the force at that distance with the force of gravitation on the
earth's surface. But to do this we must compare the matter in the earth
with that in the sun. This we can only do by _assuming_ the law to be
proved. Again, in descending from the earth's gravitation to that of two
small bodies, as in the Cavendish experiment, we _assume_ the law to
hold and deduce the mass of the earth in terms of our unit of mass.
Hence, when we say that the mass of the earth is 5½ times that of an
equal volume of water we _assume_ the law of gravitation to be that of
Newton. Thus a proof of the law from planetary down to terrestrial
distances is physically impossible.

Again, that portion of the law which says that gravitational attraction
is proportional to the quantity of matter, which is the same as saying
that the attraction of one body by another is not affected by the
presence of a third, the feeble proof that we give by weighing bodies in
a balance in different positions with respect to each other cannot be
accepted on a larger scale. When we can tear the sun into two portions
and prove that either of the two halves attracts half as much as the
whole, then we shall have a proof worth mentioning.

Then as to the relation of gravitation and time what can we say? Can we
for a moment suppose that two bodies moving through space with great
velocities have their gravitation unaltered? I think not. Neither can we
accept Laplace's proof that the force of gravitation acts
instantaneously through space, for we can readily imagine some
compensating features unthought of by Laplace.

How little we know then of this law which has been under observation for
two hundred years!

Then as to matter itself how have our views changed and how are they
constantly changing. The round hard atom of Newton which God alone could
break into pieces has become a molecule composed of many atoms, and each
of these smaller atoms has become so elastic that after vibrating
100,000 times its amplitude of vibration is scarcely diminished. It has
become so complicated that it can vibrate with as many thousand notes.
We cover the atom with patches of electricity here and there and make of
it a system compared with which the planetary system, nay the universe
itself, is simplicity. Nay more: some of us even claim the power, which
Newton attributed to God alone, of breaking the atom into smaller pieces
whose size is left to the imagination. Where, then, is that person who
ignorantly sneers at the study of matter as a material and gross study?
Where, again, is that man with gifts so God-like and mind so elevated
that he can attack and solve its problem?

To all matter we attribute two properties, gravitation and inertia.
Without these two matter cannot exist. The greatest of the natural laws
states that the power of gravitational attraction is proportional to the
mass of the body. This law of Newton, almost neglected in the thoughts
of physicists, undoubtedly has vast import of the very deepest meaning.
Shall it mean that all matter is finally constructed of uniform and
similar primordial atoms or can we find some other explanation?

That the molecules of matter are not round, we know from the facts of
crystallography and the action of matter in rotating the plane of
polarization of light.

That portions of the molecules and even of the atoms are electrically
charged, we know from electrolysis, the action of gases in a vacuum tube
and from the Zeeman effect.

That some of them act like little magnets, we know from the magnetic
action of iron, nickel and cobalt.

That they are elastic, the spectrum shows, and that the vibrating
portion carries the electrified charge with it is shown by the Zeeman
effect.

Here, then, we have made quite a start in our problem: but how far are
we from the complete solution? How can we imagine the material of which
ordinary or primordial atoms are made, dealing as we do only with
aggregation of atoms alone? Forever beyond our sight, vibrating an
almost infinite number of times in a second, moving hither and yon with
restless energy at all temperatures beyond the absolute zero of
temperature, it is certainly a wonderful feat of human reason and
imagination that we know as much as we do at present. Encouraged by
these results, let us not linger too long in their contemplation but
press forward to the new discoveries which await us in the future.

Then as to electricity, the subtile spirit of the amber, the demon who
reached out his gluttonous arms to draw in the light bodies within his
reach, the fluid which could run through metals with the greatest ease
but could be stopped by a frail piece of glass! Where is it now?
Vanished, thrown on the waste heap of our discarded theories to be
replaced by a far nobler and exalted one of action in the ether of
space.

And so we are brought to consider that other great entity--the ether:
filling all space without limit, we imagine the ether to be the only
means by which two portions of matter distant from each other can have
any mutual action. By its means we imagine every atom in the universe to
be bound to every other atom by the force of gravitation and often by
the force of magnetic and electric action, and we conceive that it alone
conveys the vibratory motion of each atom or molecule out into space to
be ever lost in endless radiation, passing out into infinite space or
absorbed by some other atoms which happen to be in its path. By it all
electromagnetic energy is conveyed from the feeble attraction of the
rubbed amber through the many thousand horse-power conveyed by the
electric wires from Niagara to the mighty rush of energy always flowing
from the Sun in a flood of radiation. Actions feeble and actions mighty
from intermolecular distances through interplanetary and interstellar
distances until we reach the mighty distances which bound the
Universe--all have their being in this wondrous ether.

And yet, however wonderful it may be, its laws are far more simple than
those of matter. Every wave in it, whatever its length or intensity,
proceeds onwards in it according to well known laws, all with the same
speed, unaltered in direction from its source in electrified matter, to
the confines of the Universe unimpaired in energy unless it is disturbed
by the presence of matter. However the waves may cross each other, each
proceeds by itself without interference with the others.

So with regard to gravitation, we have no evidence that the presence of
a third body affects the mutual attraction of two other bodies, or that
the presence of a third quantity of electricity affects the mutual
attraction of two other quantities. The same for magnetism.

For this reason the laws of gravitation and of electric and magnetic
action including radiation are the simplest of all laws when we confine
them to a so-called vacuum, but become more and more complicated when we
treat of them in space containing matter.

Subject the ether to immense electrostatic, magnetic or gravitational
forces and we find absolutely no signs of its breaking down or even of
change of properties. Set it into vibration by means of an intensely hot
body like the sun and it conveys many thousand horse-power for each
square foot of surface as quietly and with apparently unchanged laws as
if it were conveying the energy of a tallow dip.

Again, subject a millimeter of ether to the stress of many thousand, nay
even a million, volts and yet we see no signs of breaking down.

Hence the properties of the ether are of ideal simplicity and lead to
the simplest of natural laws. All forces which act at a distance, always
obey the law of the inverse square of the distance, and we have also the
attraction of any number of parts placed near each other equal to the
arithmetical sum of the attractions when those parts are separated. So
also the simpler law of etherial waves which has been mentioned above.

At the present time, through the labors of Maxwell supplemented by those
of Hertz and others, we have arrived at the great generalization that
all wave disturbances in the ether are electromagnetic in their nature.
We know of little or no etherial disturbance which can be set up by the
motion of matter alone: the matter must be electrified in order to have
sufficient hold on the ether to communicate its motion to the ether. The
Zeeman effect even shows this to be the case where molecules are
concerned and when the period of vibration is immensely great. Indeed
the experiment on the magnetic action of electric convection shows the
same thing. By electrifying a disc in motion it appears as if the disc
holds fast to the ether and drags it with it, thus setting up the
peculiar etherial motion known as magnetism.

Have we not another case of a similar nature when a huge gravitational
mass like that of the earth revolves on its axis? Has not matter a
feeble hold on the ether sufficient to produce the earth's magnetism?

But the experiment of Lodge to detect such an action apparently showed
that it must be very feeble. Might not his experiment have succeeded had
he used an electrical revolving disc?

To detect something dependent on the relative motion of the ether and
matter has been and is the great desire of physicists. But we always
find that, with one possible exception, there is always some
compensating feature which renders our efforts useless. This one
experiment is the aberration of light, but even here Stokes has shown
that it may be explained in either of two ways: first, that the earth
moves through the ether of space without disturbing it, and second, if
it carries the ether with it by a kind of motion called irrotational.
Even here, however, the amount of action probably depends upon
_relative_ motion of the luminous source to the recipient telescope.

So the principle of Döppler depends also on this relative motion and is
independent of the ether.

The result of the experiments of Foucault on the passage of light
through moving water can no longer be interpreted as due to the partial
movement of the ether with the moving water, an inference due to
imperfect theory alone. The experiment of Lodge, who attempted to set
the ether in motion by a rapidly rotating disc, showed no such result.

The experiment of Michelson to detect the etherial wind, although
carried to the extreme of accuracy, also failed to detect any relative
motion of the matter and the ether.

But matter with an electrical charge holds fast to the ether and moves
it in the manner required for magnetic action.

When electrified bodies move together through space or with reference to
each other we can only follow their mutual actions through very slow and
uniform velocities. When they move with velocities comparable with that
of light, equal to it or even beyond it, we calculate their mutual
actions or action on the ether only by the light of our imagination
unguided by experiment. The conclusions of J. J. Thomson, Heaviside and
Hertz are all results of the imagination and they all rest upon
assumptions more or less reasonable but always assumptions. A
mathematical investigation always obeys the law of the conservation of
knowledge: we never get out more from it than we put in. The knowledge
may be changed in form, it may be clearer and more exactly stated, but
the total amount of the knowledge of nature given out by the
investigation is the same as we started with. Hence we can never predict
the result in the case of velocities beyond our reach, and such
calculations as the velocity of the cathode rays from their
electromagnetic action has a great element of uncertainty which we
should do well to remember.

Indeed, when it comes to exact knowledge, the limits are far more
circumscribed.

How is it, then, that we hear physicists and others constantly stating
what will happen beyond these limits? Take velocities, for instance,
such as that of a material body moving with the velocity of light. There
is no known process by which such a velocity can be obtained even though
the body fell from an infinite distance upon the largest aggregation of
matter in the Universe. If we electrify it, as in the cathode rays, its
properties are so changed that the matter properties are completely
masked by the electromagnetic.

It is a common error which young physicists are apt to fall into to
obtain a law, a curve or a mathematical expression for given
experimental limits and then to apply it to points outside those limits.
This is sometimes called extrapolation. Such a process, unless carefully
guarded, ceases to be a reasoning process and becomes one of pure
imagination specially liable to error when the distance is too great.

But it is not my purpose to enter into detail. What I have given
suffices to show how little we know of the profounder questions involved
in our subject.

It is a curious fact that, having minds tending to the infinite, with
imaginations unlimited by time and space, the limits of our exact
knowledge are very small indeed. In time we are limited by a few hundred
or possibly thousand years: indeed the limit in our science is far less
than the smaller of these periods. In space we have exact knowledge
limited to portions of our earth's surface and a mile or so below the
surface, together with what little we can learn from looking through
powerful telescopes into the space beyond. In temperature our knowledge
extends from near the absolute zero to that of the sun but exact
knowledge is far more limited. In pressures we go from the Crookes
vacuum still containing myriads of flying atoms to pressures limited by
the strength of steel but still very minute compared with the pressures
at the center of the earth and sun, where the hardest steel would flow
like the most limpid water. In velocities we are limited to a few miles
per second. In forces to possibly 100 tons to the square inch. In
mechanical rotations to a few hundred times per second.

All the facts which we have considered, the liability to error in
whatever direction we go, the infirmity of our minds in their reasoning
power, the fallibility of witnesses and experimenters, lead the
scientist to be specially sceptical with reference to any statement made
to him or any so-called knowledge which may be brought to his attention.
The facts and theories of our science are so much more certain than
those of history, of the testimony of ordinary people on which the facts
of ordinary history or of legal evidence rest, or of the value of
medicines to which we trust when we are ill, indeed to the whole fabric
of supposed truth by which an ordinary person guides his belief and the
actions of his life, that it may seem ominous and strange if what I have
said of the imperfections of the knowledge of physics is correct. How
shall we regulate our minds with respect to it: there is only one way
that I know of and that is to avoid the discontinuity of the ordinary,
indeed the so-called cultivated legal mind. There is no such thing as
absolute truth and absolute falsehood. The scientific mind should never
recognize the perfect truth or the perfect falsehood of any supposed
theory or observation. It should carefully weigh the chances of truth
and error and grade each in its proper position along the line joining
absolute truth and absolute error.

The ordinary crude mind has only two compartments, one for truth and one
for error; indeed the contents of the two compartments are sadly mixed
in most cases: the ideal scientific mind, however, has an infinite
number. Each theory or law is in its proper compartment indicating the
probability of its truth. As a new fact arrives the scientist changes it
from one compartment to another so as, if possible, to always keep it in
its proper relation to truth and error. Thus the fluid nature of
electricity was once in a compartment near the truth. Faraday's and
Maxwell's researches have now caused us to move it to a compartment
nearly up to that of absolute error.

So the law of gravitation within planetary distances is far toward
absolute truth, but may still need amending before it is advanced
farther in that direction.

The ideal scientific mind, therefore, must always be held in a state of
balance which the slightest new evidence may change in one direction or
another. It is in a constant state of skepticism, knowing full well that
nothing is certain. It is above all an agnostic with respect to all
facts and theories of science as well as to all other so-called beliefs
and theories.

Yet it would be folly to reason from this that we need not guide our
life according to the approach to knowledge that we possess. Nature is
inexorable; it punishes the child who unknowingly steps off a precipice
quite as severely as the grown scientist who steps over, with full
knowledge of all the laws of falling bodies and the chances of their
being correct. Both fall to the bottom and in their fall obey the
gravitational laws of inorganic matter, slightly modified by the
muscular contortions of the falling object but not in any degree changed
by the previous belief of the person. Natural laws there probably are,
rigid and unchanging ones at that. Understand them and they are
beneficent: we can use them for our purposes and make them the slaves of
our desires. Misunderstand them and they are monsters who may grind us
to powder or crush us in the dust. Nothing is asked of us as to our
belief: they act unswervingly and we must understand them or suffer the
consequences. Our only course, then, is to act according to the chances
of our knowing the right laws. If we act correctly, right; if we act
incorrectly, we suffer. If we are ignorant we die. What greater fool,
then, than he who states that belief is of no consequence provided it is
sincere.

An only child, a beloved wife, lies on a bed of illness. The physician
says that the disease is mortal; a minute plant called a microbe has
obtained entrance into the body and is growing at the expense of its
tissues, forming deadly poisons in the blood or destroying some vital
organ. The physician looks on without being able to do anything. Daily
he comes and notes the failing strength of his patient and daily the
patient goes downward until he rests in his grave. But why has the
physician allowed this? Can we doubt that there is a remedy which shall
kill the microbe or neutralize its poison? Why, then, has he not used
it? He is employed to cure but has failed. His bill we cheerfully pay
because he has done his best and given a chance of cure. The answer is
ignorance. The remedy is yet unknown. The physician is waiting for
others to discover it or perhaps is experimenting in a crude and
unscientific manner to find it. Is not the inference correct, then, that
the world has been paying the wrong class of men? Would not this
ignorance have been dispelled had the proper money been used in the past
to dispel it? Such deaths some people consider an act of God. What
blasphemy to attribute to God that which is due to our own and our
ancestors' selfishness in not founding institutions for medical research
in sufficient number and with sufficient means to discover the truth.
Such deaths are murder. Thus the present generation suffers for the sins
of the past and we die because our ancestors dissipated their wealth in
armies and navies, in the foolish pomp and circumstance of society, and
neglected to provide us with a knowledge of natural laws. In this sense
they were the murderers and robbers of future generations of unborn
millions and have made the world a charnel house and place of mourning
where peace and happiness might have been. Only their ignorance of what
they were doing can be their excuse, but this excuse puts them in the
class of boors and savages who act according to selfish desire and not
to reason and to the calls of duty. Let the present generation take
warning that this reproach be not cast on it, for it cannot plead
ignorance in this respect.

This illustration from the department of medicine I have given because
it appeals to all. But all the sciences are linked together and must
advance in concert. The human body is a chemical and physical problem,
and these sciences must advance before we can conquer disease.

But the true lover of physics needs no such spur to his actions. The
cure of disease is a very important object and nothing can be nobler
than a life devoted to its cure.

The aims of the physicist, however, are in part purely intellectual; he
strives to understand the Universe on account of the intellectual
pleasure derived from the pursuit, but he is upheld in it by the
knowledge that the study of nature's secrets is the ordained method by
which the greatest good and happiness shall finally come to the human
race.

Where, then, are the greatest laboratories of research in this city, in
this country, nay, in the world? We see a few miserable structures here
and there occupied by a few starving professors who are nobly striving
to do the best with the feeble means at their disposal. But where in the
world is the institute of pure research in any department of science
with an income of $100,000,000 par year. Where can the discoverer in
pure science earn more than the wages of a day laborer or cook? But
$100,000,000 per year is but the price of an army or a navy designed to
kill other people. Just think of it, that one per cent, of this sum
seems to most people too great to save our children and descendants from
misery and even death!

But the twentieth century is near--may we not hope for better things
before its end? May we not hope to influence the public in this
direction?

Let us go forward, then, with confidence in the dignity of our pursuit.
Let us hold our heads high with a pure conscience while we seek the
truth, and may the American Physical Society do its share now and in
generations yet to come in trying to unravel the great problem of the
constitution and laws of the Universe.




                             HENRY A. ROWLAND.


[Footnote 1: Address delivered to the Physical Society of America by the
President, at its meeting in New York, October 28, 1899.]