December 11, 1970
from NobelPrize Website
1. Science and
Every new discovery displaces the interest and the emphasis. Equally important is that new technological developments open new fields for scientific investigation.
To a considerable extent the way science takes depends on the construction of new instruments as is evident from the history of science.
For example after the development of classical mechanics and electromagnetism during the 19th century, a new era was started by the construction of highly developed spectrographs in the beginning of this century. For its time those were very complicated and expensive instruments. They made possible the exploration of the outer regions of the atom.
Similarly, in the thirties the cyclotron - for its time a very complicated and expensive instrument - was of major importance in the exploration of the nucleus. Finally, the last decade has witnessed the construction of still more complicated and expensive instruments, the space vehicles, which are launched by a highly developed rocket technology and instrumented with the most sophisticated electronic devices.
We may then ask the question:
These regions earlier were supposed to be void and structureless but we now know that they are filled with plasmas, intersected by sheath-like discontinuities, and permeated by a complicated pattern of electric currents and electric and magnetic fields. The knowledge gained in this way is fundamental to our general understanding of plasmas, especially cosmic plasmas.
Indirectly it will hence be important to thermonuclear research, to the study of the structure of the galaxy and the metagalaxy, and to cosmological problems.
Our advancing knowledge in cosmical
electrodynamics will make it possible to approach these fields in a
less speculative way than hitherto. The knowledge of plasmas is also
fundamental to our understanding of the origin and evolution of the
Solar System, because there are good reasons to believe that the
matter which now forms the celestial bodies once was dispersed in a
As several of the basic problems of the
magnetosphere and interplanetary space are still unsolved, one can
be sure that these regions will still command much interest.
However, the lunar landings and also the
deep-space probes to Venus
and Mars have supplied us with so many new scientific facts that the
emphasis in space research is moving towards the exploration of the
Moon, the planets, and other celestial bodies in the Solar System.
However, when applying this research pattern to the Moon and the planets one is confronted with another problem, viz. how these bodies were originally formed.
In fact many of the recent space research reports end with speculations about the formation and evolution of the solar system. It seems that this will necessarily be one of the main problems - perhaps the main problem - on which space research will center in the near future.
Already at an early data NASA stated that the main scientific goal of space research should be to clarify how the solar system was formed. This is indeed one of the fundamental problems of science. We are trying to write the scientific version of how our Earth and its neighbors once were created.
From a - shall we say - philosophical
point of view, this is just as important as the structure of matter,
which has absorbed most of the interest during the first two thirds
of this century.
3. Plasma physics and
As you know, plasma physics has started along two parallel lines. The first one was the hundred years old investigations in what was called electrical discharges in gases. This approach was to a high degree experimental and phenomenological, and only very slowly reached some degree of theoretical sophistication. Most theoretical physicists locked down on this field, which was complicated and awkward.
The plasma exhibited striations and
double-layers, the electron distribution was non-Maxwellian, there
were all sorts of oscillations and instabilities. In short, it was a
field which was not at all suited for mathematically elegant
This was the starting point of
The cosmical plasma physics of today is far less advanced than the thermonuclear research physics.
It is to some extent the playground of
theoreticians who have never seen a plasma in a laboratory. Many of
them still believe in formulae which we know from laboratory
experiments to be wrong. The astrophysical correspondence to the
thermonuclear crisis has not yet come.
It is now obvious that we have to start
a second approach from widely different starting points.
This means that in every region where it is possible to explore the state of the plasma by magnetometers, electric field probes and particle analyzers, we find that in spite of all their elegance, the first approach theories have very little to do with reality.
It seems that the change from the first approach to the second approach is the astrophysical correspondence to the thermonuclear crisis.
Indeed it is essential to stress that astrophysics is essentially an application to cosmic phenomena of the laws of nature found in the laboratory. From this follows that a particular field of astrophysics is not ripe for a scientific approach before experimental physics has reached a certain state of development.
As a well-known historic example, before
the advance of nuclear physics the attempts to understand how the
stars generated their energy could not possibly be more than
speculations without very much permanent value.
This is a very shaky basis because the formation of the sun (and other stars) is a highly controversial subject.
Recognizing that the satellite systems
of Jupiter, Saturn, and Uranus are very similar to the planetary
system, and at least as regular as this system, it seems now more
appropriate to aim at a general theory of the formation of secondary
bodies around a central body, regarding the formation of the
planetary system as only one of the applications of such a general
As the origin of the solar system
is essentially a question of the repeated formation of secondary
bodies around a primary body, the term hetegony (from Greek
hetairos or hetes = companion) has been suggested.
A primeval plasma was concentrated in certain regions around a central body, and condensed to small solid grains. (Even the primeval plasma may have contained grains.)
The grains accreted to what have been called embryos and by further accretion larger bodies were formed: planets if the central body was the sun, and satellites if it was a planet. The place of the asteroids in the hetegonic diagram is controversial.
They have formerly been generally considered to be fragments of a broken-up planet, but there are now an increasing number of arguments for the view that they represent - or at least are similar to - an intermediate state in the formation of planets.
A clarification of these two alternatives is important.
However, the situation seems now to be
changing so that there is a good hope to bring the whole field of
research from the state of a discussion of more or less bright
hypotheses to a systematic scientific analysis.
Besides plasma physics, which we have already discussed, there are a number of other fields of research which are basic for the reconstruction of the hetegonic processes.
7. Space observations
relevant to the hetegonic problem
We shall now discuss the question of
what sort of space missions are of special value for the study of
the hetegonic problem.
Further, meteor impacts on spacecraft supply us with information of the very small bodies in our environment, which are probably related to those small bodies out of which our present planets once accreted. Particularly important is the study of meteor impacts on the Moon (and on Mars).
Hence these and other investigations «automatically» contribute to the background knowledge necessary for the solution of the hetegonic problem. But although this is satisfactory there are a number of crucial problems which cannot be solved unless space research is purposely directed towards solving them.
We shall now discuss how this could be
8. Big bodies versus
This is not necessarily true, because
missions to asteroids and comets would be at least as interesting
from a scientific point of view. As some asteroids are the closest
neighbors of the Earth-Moon system, this would also be the easiest
from a technical point of view.
Thus small bodies will be relevant to earlier periods more than large bodies.
This means that it is essentially
through studying the properties of small bodies in space that we can
hope to understand the crucial phase in the formation of the solar
system when most of the matter, which later formed the planets and
satellites, was still dispersed.
The earliest phase of this accretion produced a small body, the matter of which may today be in the core of the planet, which means that it is inaccessible even if a manned spacecraft should land on the surface of the planet.
There is also a possibility that, for example, convection in the interior of the planet has more or less completely obliterated the information once stored there. Concerning the surface layers, geological processes, including atmospheric effects, have mostly wiped out the surface traces of the hetegonic processes in Earth and probably also in Venus.
In other bodies like
the Moon and
and probably also Mercury, there seems to be considerable
information left, but only referring to the very last phase of the hetegonic processes.
Furthermore, a study of them will give us knowledge of the behavior of small bodies in space which will be valuable for the clarification of the hetegonic processes in general. We study in them intermediate products in the manufacturing of planets.
They give us, so-to-say, snapshots
showing the sequence of events when a planet like the Earth once was
The great revolution in physics which took place in the beginning of this century meant that classical mechanics and classical electrodynamics were considered to be more or less obsolete as fields of research. The new fields which attracted the interest were the theory of relativity and quantum mechanics and the experimental work was largely concentrated on the exploration of the electron shells of the atom.
The advance of nuclear physics marked
another step in a similar direction.
Also classical electromagnetism is of decisive importance to the theory of magnetized plasmas, which is basic both for thermonuclear research and for astrophysics in general. This does not mean that we should make the mistake - similar to what was made 50 years ago - of declaring the atomic and nuclear physics to be obsolete. They are not.
They have an enormous inertia which will keep them moving, and they will produce many new and interesting results.
But they have got very serious
competitors, and remarkably enough these are the fields which
earlier were declared dead that are now being resurrected.
I believe that it is easier to explain the 33 instabilities in plasma physics or the resonance structure of the solar system. The increased emphasis on the new fields mean a certain demystification of physics. In the spiral or trochoidal motion which science makes during the centuries, its guiding center has returned to those regions from where it started.
It was the wonders of the night sky, observed by Indians, Sumerians or Egyptians, that started science several thousand years ago. It was the question why the wanderers - the planets - moved as they did that triggered off the scientific avalanche several hundred years ago.
The same objects are now again in the center of science only the questions we ask are different.
We now ask how to go there, and we also ask how these bodies once were formed. And if the night sky on which we observe them is at a high latitude, outside this lecture hall - perhaps over a small island in the archipelago of Stockholm - we may also see in the sky an aurora, which is a cosmic plasma, reminding us of the time when our world was born out of plasma.
Because in the beginning was the