**Science
in Christian Perspective**

*Physics inthe Future
*
Where Do We Go From Here?*

ARTHUR E. RUARK

7952 Orchid St. N. W. Washington, 13. C. 20012

From: *JASA* **22** (March 1970): 4-7.

**B**ecause all science feeds on unsolved problems, it is our privilege, from time
to time, to make some forecast of the future. Naturally, the forecaster can do
nothing about some great surprise that may come, with sudden force, to change
the course of a whole science. Nevertheless, in a well developed science such
as physics, one can see some invariant driving forces. There are tides in the
affairs of physics that drive us onward without cease. The greatest tide of all
appears to be explicit faith in the unity and consistency of natural behavior.
This faith implies that parts of our subject that develop in relative isolation
will come together to form a broader, more perfect structure.

A very striking feature of our times has been the extension of
physical and chemical
and biological studies to very small sixes and time intervals. I am
talking about
our ability to deal with atoms, nuclei and elementary particles. Again, there
has been extension of our ability to learn about the large-scale
features of this
universe-this "bourne of space and time," as Tennyson said. These are
intellectual and moral endeavors, in the sense that we have to deal with great
uniformities in nature; with creation, evolution and final fate.

Here, my unifying thread of thought will be the increasing interaction between
subatomic physics and the physics of the heavens. I shall consider some
solved problems in these fields. The list is highly selective. I have excluded
nearly all the things in the mainstream of current effort, in order to include
others that now receive little attention but may be in the mainstream in years
to come. Let us proceed, beginning with a few topics in fundamental
physics.

**
THE VERY, VERY SMALL
**
We all know of the close relation between the relativity theory and the quantum
theory. However, there are curiosities connected with this matter. Partly they
arise because the field on which the game of quantum theory is played
is a classical
manifold, the field of space and time, or better spoken,
"space-time."
Let me indicate how these two theories are connected at their very roots.

"After taking bachelor's, master's and doctor's degrees at Johns Hopkins University, Arthur E. bark taught at Yale, Pittsburgh, North Carolina and Alabama universities. tIc joined the Atomic Energy Commission in 1956 as chief of the controlled thermonuclear program and recently retired as senior associate director of the division of research as the AbC.

Quantum theory is a relativistic theory. The basic papers of Louis de Brogue and of Erwin Schrodinger already showed that the waves belonging to a particle of speed v have a phase speed c2/e, where c is the speed of light. This formula arises from special relativity; if one uses Newtonian mechanics, a wrong result is obtained.

Special relativity deals with space and time enördinatesx and t, so that it is usually considered to he a classical theory; that is to say, a nonquantum theory. This seems to be correct when one considers it as a mathematical scheme; for there is no mention of Planck's constant is in the axioms set up by Albert Einstein. On the other hand, I do not think it is generally understood that this point of view has to be modified a hit when we take a hard look at the interpretation of the theory.

**
There are tides in the affairs of physics that drive us onward without cease.
The greatest tide of all appears to be explicit faith in the unity
and consistency
of natural behavior.**

In order to use the theory in physics, we have to say what the quantities x and
f stand for, and Einstein made the choice that is really useful. When lie said
x, he meant a length measured with a real meter stick. He did not
mean a hypothetical
nonexistent "rigid ruler," the kind talked about in geometry classes.
When he said t, he meant a time measured with a laboratory clock. Now, this has
consequences. The object to he measured is a dynamic thing, and so is
the standard.
The meter stick is a group of crystals, a vibrating body held
together by quantum
forces, and so is the clock. It looks as though we are caught in a
vicious circle;
we want to study the intenors of atoms with the aid of laboratory
standards, and
Lo! The standards are made out of the very things we want to study.

True enough, we do not actually thrust a meter stick down into the
atom. We have
none with divisions fine enough, and we know that such a disturbance
of the atom
would not he pertinent if we could do so. Actually, we have to study
the wavelengths
of light emitted (and other useful quantities), recording them always with the aid of gross apparatus-a favorite topic of Niels Bohr.

Always there are experimental troubles. Always, we are making use of a chain of
experimental results and interpretation, concerned with the whole
coupled apparatus
and based on special relativity and quanturn theory together. A
central question
is whether we wish to use our ordinary ideas about lengths and distances when
we get into the domain of the very, very small; is this practice
really bad? Not
at all. The physicist is always trying to extend the scope of his
laws or to find
their limitations. He is a great fellow for cutting Gordian knots; so
he says:

"I shall continue to use special relativity and quanturn theory
as a strange
pair of partners, to interpret results of my experiments on collisions between
elementary particles; and I shall find out whether I run into
discrepancies."

Breakdown?

Nowadays, one kind of search for such discrepancies is called experimentation
on the breakdown of quantum electrodynamics. It is carried on by studying, for
example, collisions between two electrons; one looks at the
distribution of scattered
electrons to see whether it agrees with predictions from electrodynamics. As of
1968, there was no clear evidence of trouble,^{1} down to inferred
distances between
the collision partners as small as about 1.8 x 10^{-14} cm.

The question now arises: Could particle theory continue to make use
of the customary
spacetime concept if a breakdown of electrodynamics were found? Let us see. A
failure of present-day theory would simply lead to construction of
some new formulation,
not to a modification of the space-time picture. People would keep
that picture.
What they want is consistency in theoretical talk over the whole
range of space-time
dimensions, "from zero to infinity." It will be extremely
bard to eject
the space-time picture from any part of physics. Curvature may he introduced;
broader geometries may be invoked, but the continuous manifold will
still be there
because of the flexibility with which new physical fields can be
introduced when
experiments appear to suggest their presence.

**
Weak and Infrequent Things**

The success of Fred Reincs and Clyde Cowan^{2} in starting up the
subject of experimental
neutrino physics showed us that studies involving miniscule cross sections can
he worth a great deal of effort. There is also the search for
gravitational waves,
it is heartening to know that Joseph Weber^{3} has really excellent apparatus to
look for these waves; his laboratory is full of seismographs and the like, for
throwing out spurious effects from tides and earthquakes. It is still
more heartening
to know that he has some events that are difficult to explain by
means of terrestrial
disturbances.

We should not forget that there may he very weak forces in nature,
still undiscovered,
aside from the gravitational ones. I do not know of any current search for such
forces.

The whole trend in physics has been to assume that particles are extremely well
standardized. Nevertheless a few people^{4} have been looking for
anomalous or nonstandard
particles; here I am talking about aberrant electrons, protons, or
what-have-you?
The resources of modem technique (and in particular, the capabilities
of optical
spectrographs) are not now
being fully used to make some progress with this matter. The trouble
is that when
one starts to speculate about such particles, the possibilities are very wide;
so one must look very selectively for good opportunities to do an interesting
experiment.

**
The Search for Underlying Levels
**

In recent years we have seen rather extensive searches for an underlying level of simpler things from which a horde of elementary particles might be made. There was the quark search and the search for Dirac magnetic poles; now there is the interest in so-called "W particles." The quark idea, as a mathematical scheme, is indeed ingenious arid interesting. The quarks are sometimes thought of as the ultimate particles, but there is a trouble with such ideas. If we had quarks, people would just say, "What are they made of?" This is an example of the infinite Regression-a question such that if you answer it you come up against another question of the same kind.

**Astrophysics and Cosmology**

We are all aware of the highly fruitful relations betweets advances in atomic
and nuclear physics and those in astrophysics and nebular physics. Furthermore,
the fruits of cosmic-ray work, radio astronomy and x-ray astronomy show us that
high-energy physics is one essential key to the understanding of very violent
astrophysical events." But there is mounting evidence that, in a broader
sense, particle physics and cosmology are closely related. Let us
turn our attention
to a few aspects of this fascinating realm of ideas.

**
Space-time and Matter
**
It is frequently said that the material content of space and the motion of that
material determine the curvature of the space-time manifold. This is
often called
Mach's principle. Indeed, Einstein's gravitational equations say that a tensor
built from curvature quantities is equal to the matter-energy tensor T

This is a good place to ask, "How is it that space has three dimensions?" This question is at least 70

years old. I have seen nothing on the subject that is more than a plausibility argument, but I have a small suggestion as to a fresh approach. Suppose we use the methods of tensor and spinor calculus to examine physical equations in space-time of several dimensions, from two up to six, for example. Let us cover both classical theory and quantum theory, remembering to look closely at the properties of simple solutions that represent point particles; we search for features that appear particularly desirable or unique (or both), in the case of fourdimensional space-time. If such features emerge, we may understand a little better the preference for three space dimensions in this universe. The results would still be plausibility arguments, but if they looked attractive, we would promote them to the status of assumptions; and that would be that.

Perhaps the most significant fact that has emerged from exploration of the distant galaxies is the general consistency of physical law over very large spaces and long time intervals. Apparently we are not dealing with different bodies of law, linked together only by very weak connections. We appear to be living in a Universe-not in some sort of Diverse, or Polyverse. A cardinal piece of support for this welcome notion is the red shift of Vesto Slipher, Edwin Hubble and Milton Ilumason. To an approximation, the light from distant galaxies is shifted toward the red, by amounts that can he explained by assuming that they move outward with speeds c, proportional to their distances R from us; the relation is v = 75R, with c in kilometers per second and R in megaparsecs; one megaparsec is 3.09 X 10

Allowing for this red shift, we see the same spectral series, the same atomic behavior, that is found here on earth. Of course, this probing out to great distances means that one is looking back a long way in time. What is the inner meaning of this consistency? The distant atoms would not show the spectral series properly if they did not obey the Pauli principle. Those atoms are testifying to identity of the electrons and identity of the nuclei in the whole region available for observation. They are revealing a most extraordinary degree of quality control in the creation and maintenance of these particles. Why, not even RollsRoyce...!

Is this uniformity of particle properties due to a uniformity in the properties of space-time itself? Or are these two ideas just the same idea clothed in different words? I leave the answer to you-or your grandchildren.

What shall we say about this result? An orthodox quantum theorist might say, "It is all a matter of chance; this matter was explained in 1927." A thoroughgoing determinist might say, "This astounding accuracy of aim is evidence of extraordinary quality control." A classical relativist might say, "All point events that are connected by light rays are at the same spot in space-time. We are dealing with a sort of contact action. From the standpoint of a being who perceives point events directly and intuitively, there is no problem." We possess considerable flexibility in contemplation of these answers or others like them; for each answer is based on some set of axioms, and axioms are arbitrary indeed. The orthodox quantum theorist will say, "Yes, but look at the fruits of my axioms." And we shall reply "The fruits of your axioms are very great indeed, but a large number of very respectable people are not satisfied with the foundations of your theory."

*
Perhaps the most significant fact that has emerged from exploration
of the distant
galaxies is the general consistency of physical law over very large
spaces and long time intervals... We
appear to be living in a Universe-not in some sort of Diverse, or
Polyverse.*

**
Permanence: A Desirable Feature
**
Let us consider the permanence of gross matter. The customary
estimates of universe
duration lie a little above 10

People are generally impressed with the vast spaces between the stars of our galaxy, and also the spaces between galaxies, which, on the average, are somewhat like tennis balls 8 meters apart. This diluteness is much to be prized, because violent things happen when big pieces of matter get too close together. I invite your attention to the famous case of the galaxy M 82. A photograph of this galaxy can be found in reference

Information From Far Away

How much can we hope in learn about very distant objects? In general, the farther away an object is, the less we can find out about it. Details fuss out; light signals from the object are fainter; spectra move out to the infrared. It is only in recent times that attention has been paid to the quantitative side of this common observation. Kenneth Metxner and Philip Morrison

If and when they reach the limit of their resources, we shall be confronted with an interesting situation. For a long time philosophers have been saying that physicists continually work on the soluble problems, so that metaphysics is necessarily the bin of unsolved ones. Now I shall leave it to the reader to ponder the situation of an experimental science that reaches a limit because the objects under investigation cannot provide sufficient amounts of information to our detectors to give the answers we should like to know.

I have pointed out some lines of endeavor that lie at or beyond the present limits of our capabilities, and I have only two hints for those who may choose to attack these matters. The first is that one should pay close attention to a method used by Rene Descartes. I call it the "Method of Complete Skepticism." He adopted a systematic policy of denying any statement he was considering and of looking at the consequences. The second hint is connected with economy and simplicity of thought. I quote the famous dictum of William of Occam: "

In closing, I mention once more the consistency, the connectivity, revealed by physical studies up to the present. Though each of us usually thinks of himself as a part of the universe, this is a one-sided view, for great portions of our surroundings are always exerting their influence upon us. As an overstatement, one might say that the universe is apart of every man. Sir George Thomson

"The universe that includes our perceptions and our feelings is one, and no single part can be put into a ring-fence completely isolated from all the rest."

Therefore I end this story with the thought: The universe is the proper study
of mankind.

**
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*Reprinted from Physics Today 22, No. 9, 25 (1969).