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Theories of the origin of the solar system 1956-1985
Abstract
Attempts to find a plausible naturalistic explanation of the origin of the solar system began about 350 years ago but have not yet been quantitatively successful. The period 1956--1985 includes the first phase of intensive space research; new results from lunar and planetary exploration might be expected to have played a major role in the development of ideas about lunar and planetary formation. While this is indeed the case for theories of the origin of the moon (selenogony), it was not true for the solar system in general, where ground-based observations (including meteorite studies) were frequently more decisive. During this period most theorists accepted a monistic scenario: the collapse of a gas-dust cloud to form the sun with surrounding disk, and condensation of that disk to form planets, were seen as part of a single process. Theorists differed on how to explain the distribution of angular momentum between sun and planets, on whether planets formed directly by condensation of gaseous protoplanets or by accretion of solid planetesimals, on whether the solar nebula'' was ever hot and turbulent enough to vaporize and completely mix its components, and on whether an external cause such as a supernova explosion triggered'' the initial collapse of the cloud. Only in selenogony was a tentative consensus reached on a single working hypothesis with quantitative results.
... Desde el punto de vista astronómico, se sabe que algunas estrellas con masa similar a la del Sol pasan por una etapa T-Tauri la cual se caracteriza por la generación de viento solar intenso y pérdida de masa. Uno de los estados de la etapa T-Tauri es llamado contracción Hayashi, el cual es un estado convectivo de colapso por el que atraviesa una estrella en el cual se vuelve altamente luminosa antes de pasar a la Secuencia Principal (Brush, 1990). Es probable que durante la fase post-Hayashi ocurra la pérdida de masa T-Tauri, lo cual se traduce en la generación de vientos solares intensos (Herbert y Sonett, 1978). ...
... Dans ce chapitre, nous ne développerons donc que la théorie de formation des planètes par assemblage d'un coeur puis capture d'une enveloppe de gaz. En ce qui concerne l'historique des théories de formation planétaire, de plus amples détails sont donnés dans la revue exhaustive de Brush (1990). ...
We review theories of terrestrial and giant planet formation. The following stages are described: sedimentation of micron sized dust grains in the protoplanetary disk, growth through collisions and accumulation and capture of a gaseous envelope by a planetary core.
... Theories for the formation and evolution of planets depended primarily on geophysical data from the Solar System (see Brush 1990, and references therein). Starting in the 1940's, astrophysical data began to provide new insights. ...
This pedagogical chapter covers the theory of planet formation, with an
emphasis on the physical processes relevant to current research. After
summarizing empirical constraints from astronomical and geophysical data, we
describe the structure and evolution of protoplanetary disks. We consider the
growth of planetesimals and of larger solid protoplanets, followed by the
accretion of planetary atmospheres, including the core accretion instability.
We also examine the possibility that gas disks fragment directly into giant
planets and/or brown dwarfs. We defer a detailed description of planet
migration and dynamical evolution to other work, such as the complementary
chapter in this series by Morbidelli (available at arXiv:1106.4114).
... Vertical phase transitions are well known in such cases and play an important part in, for instance, explaining the structure of gas giants such as Jupiter and Saturn. 71 Of course, since the spring constant in the tethered chain model is proportional to temperature, and since the force of gravity varies with z in a non-Hookean manner in planetary models, the analogy is not complete. ...
Phase transitions in polymeric surface films are studied with a simple model based on the van der Waals equation of state. Each chain is modeled by a single bead attached to the surface by an entropic-Hooke's law spring. The surface coverage is controlled by adjusting the chemical potential, and the equilibrium density profile is calculated with density functional theory. The interesting feature of this model is the multivalued nature of the density profile seen at low temperature. This van der Waals loop behavior is resolved with a Maxwell construction between a high-density phase near the wall and a low-density phase in a "vertical" phase transition. Signatures of the phase transition in experimentally measurable quantities are then found. Numerical calculations are presented for isotherms of surface pressure, for the Poisson ratio, and for the swelling ratio.
... The purpose of this paper is to review what we think we know about the pulsar planet origins and to place this in the broader context of this meeting, 1 For a proper history of theories of solar system formation, see Brush (1990). 2 I've been unable to verify this particular reference. ...
I describe models for the formation of planetary systems surrounding the remnants of stellar mergers and collisions. I focus primarily on models for the viscous evolution of disks suitable for the formation of the planets surrounding the pulsar B1257+12. I show that the adaptation of models for traditional protoplanetary disks which invoke quiescent or `dead' zones are quite successful in producing disks appropriate for the formation of the pulsar planets. I also briefly describe some even more exotic possibilities that may arise from compact object mergers.
In this work, we consider a statistical theory for a cosmogonical body formation (so-called spheroidal body) to develop the analytical models of protoplanetary formation in extrasolar systems. Within the framework of this theory, the models and evolution equations of the statistical mechanics have been proposed, while the well-known problem of gravitational condensation of infinite distributed cosmic substances has been solved. This paper derives the general equation of distribution of the specific angular momentum of forming protoplanets since the specific angular momentums (for particles or planetesimals) are averaged during a conglomeration process (under a planetary embryo formation). As a result, a new law for planetary distances (which generalizes Schmidt’s law) is derived theoretically. This paper develops also an alternative thermal emission of particles model of the formation of protoplanets in extrasolar systems. Within the framework of this model, the equation for the thermal distribution function of the specific angular momentums of particles moving in elliptical orbits in the gravitational field is derived. According to this thermal escape model, only 0.8% of the total number of particles in the solar system composing the protoplanetary cloud has angular momentum 15.6 times higher than the angular momentum of the remaining 99% of particles. This conclusion agrees completely with the known fact of a nonuniform distribution of the angular momentums in our solar system noted by ter Haar. As pointed out here, the exponential laws of planetary distances occur in some extrasolar systems.
The SETI endeavor represents a test for a fundamental shift in cosmological worldview, from the physical world to the biological universe. I define the “biological universe” as the scientific worldview that holds that life is widespread throughout the universe. This chapter is meant to be a contribution to the ongoing endeavor to understand where the extraterrestrial life debate fits in the history of science.
This review addresses the state of research that employs astronomical (remote
sensing) observations of solids ("dust") in young circumstellar disks to learn
about planet formation. The intention is for it to serve as an accessible,
introductory, pedagogical resource for junior scientists interested in the
subject. After some historical background and a basic observational primer, the
focus is shifted to the three fundamental topics that broadly define the field:
(1) demographics -- the relationships between disk properties and the
characteristics of their environments and hosts; (2) structure -- the spatial
distribution of disk material and its associated physical conditions and
composition; and (3) evolution -- the signposts of key changes in disk
properties, including the growth and migration of solids and the impact of
dynamical interactions with young planetary systems. Based on the state of the
art results in these areas, suggestions are made for potentially fruitful lines
of work in the near future.
At the end of the nineteenth century, Lord Kelvin's upper limit of only 20 or 30 million years for the age of the Earth was challenged by the American geologist T. C. Chamberlin, who showed that Kelvin's model of an Earth gradually cooling from an initial molten state was not the only possible one. Kelvin's limit was soon afterwards repealed by the new science of radioactivity, which yielded ages of a few billion years. While some geologists resisted this expanded time-scale, Chamberlin was the only one who could provide a comprehensive cosmogonical theory that did not submit to the epistemological superiority of physics and astronomy. In the 1940s, as radiometric age determinations improved in accuracy, they came into conflict with the expanding-universe cosmology — a conflict which the cosmologists eventually avoided by expanding their distance and time scales. In 1953, Patterson announced the result 4.5 billion years, which is still accepted as the best estimate for the age of the Earth. But geologists, liberated from Kelvin's limit, define the epoch of the Earth's formation as being outside the scope of their science, and their textbooks rarely give credit to the person who established the number that once seemed so important to accounts of the Earth's history.
The science of nucleosynthesis was substantially inspired by chemical analyses of meteorites. As if in repayment, that theory now imbues meteoritics with enlarged meaning. I recount the emergence of four great issues for nucleosynthesis—issues that received decades of my own attention; and I describe unexpected abundance patterns within meteorites that were suggested by the resolution of those issues. The latter have altered the information content of meteoritic science. The issues are:
1. a quantitative s ‐process theory
2. cosmoradiogenic chronology
3. explosive nucleosynthesis and gamma‐ray astronomy
4. cosmic chemical memory
Starting from historical origins for each issue, I comment upon both the broad cultural canvas in which they lie and my own work in their establishment. Examples of predicted (or rationalized) meteoritic measurements illustrate our surprised delight at the expansion of the range and power of meteoritic science.
Catastrophes in our solar system have played a big role especially during its early evolution, e.g., the formation of the Earth’s moon or the slow retrograde rotation of our sister planet Venus can be explained by catastrophic collisions of the early planets with other planet-sized objects. Catastrophes may have happened also on later stages during the Earth’s evolution. We give a review about the possible catastrophe scenarios and address to the question whether they caused the known mass extinctions during the last 500 million years on Earth. Could cosmic catastrophes be a thread to the existence of life in the solar system. With the discovery of many extrasolar planetary systems, the study can be extended to these systems.
The aim of this paper is to show that the global structure of our planetary system could be the result of diffusive ring-shaped acoustic waves, excited at the inner boundary layer of the slowly rotating protosun and propagating to the outer parts of the protoplanetary accretion disk. We show that for low-mass disks with a relatively high Toomre's stability number Q secular instability effects are very slow and can be neglected in a first approximation. Therefore a gravitational collapse, or, for time scales considered here, a global gravo-viscous instability can be excluded. In the framework of a WKB-analysis one can derive for the spacing ratio Λ = rn+1rn of two consecutive acoustic wave crests at the moment of maximum compression the formula Λ ≈ exp[4π(csvK)], where cs is the sound speed in the disk and vK is the local orbital speed of the disk material. We believe that the orbital spacings of the planets today reflects a definite frozen-in stage of the propagation process of these primordial acoustic waves in the protoplanetary disk. It is very likely, that in the non-linear regime the waves become shock waves and could serve as a trigger mechanism for transient high-energy processes in the dust-gas disk as well as for the very complex building processes of the planets. The theory could be relevant for the formation of the terrestrial rocky planets as well as for the cores of the giant gaseous ones.
The Titius-Bode law, which describes the average distances r between the Sun and various planets, may be represented by a new formula, rn = an2. Here a is a constant and n is an integer. If we let a 1 = 0.042, the values n = 3, 4, 5, 6 will refer to the terrestrial planets and n = 7, 8 to asteroids. For a2 = 1.2 and n = 2, 3, 4, 5, 6 this formula describes the Jovian planets. In this case Neptune, Pluto, and many satellites also agree with this formula. From this can be developed a similar theory to the Bohr atom model, and we obtain the quantum constant H = (aGM⊙)1/2 of the solar system. As such many quantities of the solar system can be quantized. Then the astronomical Schrödinger equation is derived, and the distance rule is a statistical result of planet evolution. Further, an extensive quantum theory should exist that has different quantum constants but similar formulations.
Um das Jahr 1856 war James Clerk Maxwell (1831–1879) damit beschäftigt, Faradays Konzept der elektrischen und magnetischen Felder in eine befriedigende mathematische Theorie zu übersetzen. Daneben hatte er schon Arbeiten zur Farbentheorie und Elastizitätstheorie veröffentlicht. Doch eine Arbeit hebt sich von diesen mehr physikalischen gänzlich ab: eine umfangreiche theoretische Untersuchung zur Stabilität der Saturnringe auf der Grundlage verschiedener Hypothesen bezüglich der inneren Konstitution dieser Ringe. Im folgenden Aufsatz soll einerseits gezeigt werden, wie weit Maxwell mit dieser rein astrophysikalischen Arbeit seiner Zeit voraus war; andererseits aber auch angedeutet werden, wo aus heutiger Sicht die Grenzen und notwendigen Erweiterungen seiner Modelle liegen — insbesondere im Hinblick auf strukturbildende Prozesse in der protoplanetaren Akkretionsscheibe des frühen Sonnensystems.
According to some scientists and philosophers of science, a theory is or should be judged by its ability to make successful predictions. This paper examines a case from the history of recent science---the research of Hannes Alfvén and his colleagues on space plasma phenomena---in order to see whether scientists actually follow this policy. Tests of five predictions are considered: magnetohydrodynamic waves, field-aligned (``Birkeland'') currents, critical ionization velocity and the existence of planetary rings, electrostatic double layers, and partial corotation. It is found that the success or failure of these predictions had essentially no effect on the acceptance of Alfvén's theories, even though concepts such as ``Alfvén waves'' have become firmly entrenched in space physics. Perhaps the importance of predictions in science has been exaggerated; if a theory is not acceptable to the scientific community, it may not gain any credit from successful predictions.
Earth's atmosphere is a disequilibrium mixture of oxidizable materials in the presence of large amounts of oxygen. The entropy reduction is brought about by living organisms using photochemical energy from the Sun. Almost all the oxygen in the atmosphere is derived from photosynthesis; inorganic photochemistry can produce only 10−9 of the present atmospheric level at most. Oxygen is a critical component of our atmosphere, not so much because some living organisms employ respiration, but because O2 is a precursor of atmospheric O3. Between them, O2 and O3 filter out short-wavelength UV radiation from the Sun, and so permit the existence of life on dry land.
Origin of the Earth and Moon. R. M. Canup and K. Righter, Eds. University of Arizona Press, Tucson, in collaboration with Lunar and Planetary Institute,
Houston, 2000. 571 pp. $50. ISBN 0-8165-2073-9.
The contributors to this volume, which grew out of a December 1998 conference, discuss experimental results, theoretical analyses,
and computational modeling related to the early history of the Earth-Moon system.
1992 was an astrophysically exciting year for most of us. E-mail lines buzzed with news of the COBE anisotropy, the Gallex solar-neutrino flux, a pulsar with two planets, and the remarkable isotropy of the gamma-ray burst sources seen by CGRO. Meanwhile, more routine work continued on problems like star formation that have been around for decades and seem unlikely to be fully resolved in this millenium. The overview of the year presented here attempts to strike some balance between the new discoveries and the less spectacular, but equally important, progress that comes from many people tackling a subject in different ways. Seven self-contained sections discuss the Sun, extra-solar-system planets, the search for brown dwarfs, triggered star formation, gamma-ray sources, the unified model of active galaxies, and large-scale lumpiness in the universe. Five sections of shorter items concern ( 1) the solar system and Milky Way, (2) discoveries of things long sought, (3) the converse, and (4) and (5) various kinds of corrections and updates.
We examine the gravitational capture of supersonic gas and dust as it impacts and triggers the collapse of a molecular cloud core. We use two techniques to track the triggering material in two dimensions, a set of tracer particles and a color field, much like a dye, computed in the same manner as the hydrodynamic density variable. The two tracking techniques produce very similar results. We find that about 10% to 20% of the supersonic material with an initial impact parameter less than the molecular cloud core's initial radius is captured by the collapsing cloud. This fraction is less than the 100% capture estimate often used to constrain the distance to possible stellar sources of radioactive isotopes, and hence may require these stars to be closer than would otherwise be the case. Rayleigh-Taylor instabilities occur and aid in the mixing of the shock material with the target cloud. The impacting material is injected into the outer layers of the collapsing protostar roughly one free-fall time (2 × 105 yr) after the first contact of the triggering material with the cloud, and injection continues for approximately two more free-fall times. These time intervals are substantially less than the mean life of one of the radioactive nuclides of interest, 1.1 × 106 yr for 26Al, and are comparable to the mean life (1.5 × 105 yr) of another short-lived nuclide,41Ca. Evidence for live 26Al and 41Ca in the early solar system is thus consistent with a scenario involving supersonic triggering and injection of freshly synthesized radioactive nuclides into the presolar cloud. Because injection proceeds at a steady pace, it does not appear to be a significant source of temporal heterogeneity in the distribution of 26Al, though the outer layers of the presolar cloud are preferentially enriched in the injected material.
IntroductionHistorical Background of the Development of the Core Accretion ModelObservational ConstraintsGeneral Description of the Core-accretion ModelThe Model and the Computer CodeResultsDiscussionReferencesFurther Reading
This article illustrates the possible application of homeokinetics to the constructive process of the origin of life. The homeokinetic strategy is to seek out cycles at all time scales in a system where they can be discovered (spectroscopy) and to show how inter-acting cyclic processes can account for historical emergence of new entities, many of which also are cyclic processes. The full story of emergence necessarily begins with cosmology, which eventually results in an earth that can support geological processes, which form the matrix for life. Biology and chemistry might be viewed as dominating the discussion about the ori-gin of life. However, physics also has very useful insights to share. The intent of this article is—given the evolution and development of "purpose" in life systems wherein they can persist for a great number of generations—to determine the physi-cal processes that can account for how the origin and evolution of many disparate species emerge as a regular procession of processes and events that began with the physics of the Big Bang. Actually, four topics—physics, chemistry, geology, and biology—are part of a continuum that flows from physical processes and from the way humans process in-formation. Physical science was born in the Enlightenment of the 17th century, and leads from Copernicus (ca 1500) to Newton (ca 1700; Randall, 1940; Wills, 1975). This new age of science led to the development of chemistry, geology, and biology. Chemical science began in the 18th century with Lavoisier. The coupling of ideas from these disparate fields led to an age of mechanism and machinery, and to an industrial revolution for engineering processes—civil (physical), mechanical, ECOLOGICAL PSYCHOLOGY, 13(4), 315–327 Copyright © 2001, Lawrence Erlbaum Associates, Inc.
The modern era in the extraterrestrial life debate is normally dated from Cocconi and Morrison's paper in 1959, and though one can always find precursors, this in my view is a valid perception. Cocconi and Morrison gave definite form to SETI, Frank Drake independently first carried out the experiment, a network of interested scientists began to form and met in Green Bank in November 1961, and the most distinctive part of the modern era of the extraterrestrial life debate - the Search for Extraterrestrial Intelligence by means of radio telescopes — was off and running. In this paper, after briefly reviewing some of the long-term steps toward the biological universe, I would like to examine the immediate precursors to this modern era in the 1940s and 1950s.
Making use of the fact that, in the solar system, the angular momentum is carried predominantly by the planets while the mass
is beared almost entirely by the Sun, an iterative scheme is devised to solve approximately the n-body contributions of the lunar orbit problem. The scheme envisages the Moon-Earth-Sun three-body subsystem as being nested
in the grand Earth-Jupiter-Sun system. In the planetocentric representation, the orbital motion of the Sun about the solar
system center of mass is transmitted to the third body via the second primary body in both the grand and nested three-body
systems.
Inverse and forward helioseismic approaches are reviewed. Chemical abundance profiles from a solar model generated by Takata
and Shibahashi (1998) by inverse helioseismology are used in a forward approach. This forward model is referred to as the
author’s ‘seismic’ solar model. This model is compared to a similarly calculated standard evolution solar model (ssm) and
the author’s reference high-Z core (hzc) solar model. The degree l = 1 nonradial oscillation frequencies of the three models are compared, for orders n = 7 to 33. Relative to current observations, there is good agreement between the seismic model predictions and the five-minute-band
frequency observations. In addition, there is good agreement between the hzc model frequencies and the seismic model frequencies.
Further comparisons are made in terms of fractional differences and/or of ratios of seismic/ssm, hzc/ssm and seismic/hzc quantities
such as (1) speed of sound, (2) density and (3) gamma functions, Γ1. From prior studies, the effective gamma, γe, defined by the relation, (γe − 1) = P/E, with P, the total pressure and E, the total energy, respectively, is used in the oscillation equations instead of the complete
analytic form of the Γ1 function. It is shown that between the radius fractions x (= r/R) = 0.05 to 0.95, the fractional differences and ratios seismic/hzc yield good agreements for the speed of sound, density and gammal
function. Since the hzc model is also consistent with two of the three operating solar neutrino experiments and has the bottom
of the convection region at x = 0.6926 with a temperature over 2.4 × 106 K (hence consistent with the lithium problem without invoking ‘overshoot’), it is concluded that the current hzc model is closest
to the structure of the real sun. Consequently, an astrophysical solution to the solar neutrino problem is possible as part
of an answer to the question of how the real sun formed and evolved to its present state.
The aim of the present paper is to show that an accretion disk, the material of which satisfies the Navier-Stokes equations of a compressible fluid, is secularly unstable to axisymmetric density disturbances even if Toomre's parameter Q is greater than one. This instability process, which can also be interpreted as negative diffusion, leads immediately to the formation of rings in the accretion disk as an intermediate step in the formation of planets, at least for the outer gaseous ones. We believe that the same process is also responsible for the ringlet-structure of planetary rings. Only a dynamical instability of axisymmetric density wave perturbations, represented by Toomre's condition Q , does not exist in a viscous self-gravitating disk. On the base of a local theory we calculate the characteristic wave number and the corresponding time scale of the mode of maximum secular instability. In the global theory, we formulatea complex linear integral equation describing the diffusion instability in the accretion disk. The radial distances of the rings to the protosun obey in the outer range of the disk an exponential law provided that the quantity v (the vertically integrated viscosity) is nearly constant throughout the disk. Our treatment gives arguments in favour for the result, that the spacing ratio q = r
n+1
/r
n
between two consecutive protoplanetary orbits is approximately given by the formula q exp(21/3), where is close to the ratio of the accreted ring-masses in the disk and the mass of the central body. We believe that the formation process is shorter for the outer gaseous than for the inner rocky planets, because the global secular ring instability is evanescent in the inner regions of the disk.
The modern era of the Search for Extraterrestrial Intelligence (SETI), which began with the paper of Cocconi and Morrison in 1959, reached a landmark with the inauguration of NASA''s High Resolution Microwave Survey (HRMS) in 1992. SETI programs stand in the tradition of humanity''s quest for its place in the Universe, and seek to test whether cosmic evolution results in widespread intelligence in our Galaxy. This paper reviews the history of the modern SETI era, with emphasis on the development of the NASA SETI program.
Problem of the existence of the most significant jet-stream Flora A is analysed. On the basis of the data analysis it is shown that Flora A consists mostly of very faint asteroids with (1) oppositions of perihelia during autumn months, (2) very low inclinations.
Due to the favourable observing conditions just during September, the concentration of proper longitudes of perihelia is then explained as a consequence of the observational selection effects. The low inclinations explain the concentration in proper longitudes of nodes just in the area corresponding to that to the jet-stream Flora A.
Thus, the most important asteroidal jet-stream Flora A is fully explained as a consequence of observational selection effects.
The dynamics of the satellite–planet system under the influence of the Sun is analyzed in the rotating frame of the planet. This system is described by the well-established, restricted three-body potential. In order to break the capture/escape scenario in temporary satellites, a scattering mechanism by an existing planetary satellite is suggested to account for permanent capture of guest bodies.
A review of new issues that have emerged in the study of nucleosynthesis is presented. The issues explored in detail are: (1) a quantitative s-process theory, (2) cosmoradiogenic chronology, (3) explosive nucleosynthesis and gamma-ray astronomy, and (4) cosmic chemical memory. The unexpected abundance patterns within meteorites that were suggested by the resolution of these issues are described.
The one-dimensional (1D) large bipolaron is investigated in the limit of strong electron-phonon coupling. The nonlinear integro-differential equation for the bipolaron wave function is solved numerically, from which we obtained estimates for the main characteristics. An enlargement of the stability region for the bipolaron ground state is found in 1D as compared to the stability regions in 2D and 3D. The energy of the first relaxed excited state (RES) equals the energy of two single polarons and the ground state in the potential generated by the first RES has a slightly lower energy than this RES and is therefore stable. The nonlinearity causes the feature that the combination of the ground state and an excited state of one-particle wave functions could lead to a higher bipolaron energy than the combination of two excited states.
We considered the coupled motion of an electron described by a one-dimensional (1D) tight-binding Hamiltonian, whose diagonal matrix elements have a spatial variation incommensurate with the lattice, and a harmonic 1D lattice. The coupling was taken to be of the deformation-potential type. We studied numerically the time evolution of the coupled system starting with the lattice in its classical ground state and the electron in various initial states. Depending on the initial energy of the electron, on how close to the mobility edge it is and the strength of electron-lattice coupling, we found different types of localized and apparently extended (large) polarons. Near the mobility edge even a very weak coupling suffices to create a localized polaron even for high initial electronic energies. In many instances and even for very long times the electron does not seem to transfer much of its energy to the lattice.
We have studied through real-time numerical simulations the question of polaron formation by a single electron injected in a band consisting of fluctuating amplitude or mobility edge eigenstates. We found that polaron formation depends strongly on how close to a mobility edge the initial state is, on its average energy, and, to a much lesser degree, on its shape. In some instances novel highly excited long-lived localized polarons appear. In general, the time evolution exhibits an unexpected behavior; even for very long times, the electron does not seem to transfer much of its energy to the lattice.
Is a theory that makes successful predictions of new facts better than one that does not? Does a fact provide better evidence
for a theory if it was not known before being deduced from the theory? These questions can be answered by analyzing historical
cases. Einstein's successful prediction of gravitational light bending from his general theory of relativity has been presented
as an important example of how "real" science works (in contrast to alleged pseudosciences like psychoanalysis). But, while
this success gained favorable publicity for the theory, most scientists did not give it any more weight than the deduction
of the advance of Mercury's perihelion (a phenomenon known for several decades). The fact that scientists often use the word
"prediction" to describe the deduction of such previously known facts suggests that novelty may be of little importance in
evaluating theories. It may even detract from the evidential value of a fact, until it is clear that competing theories cannot
account for the new fact.
Es werden die hydrodynamischen Gleichungen mit turbulenter Reibung für eine um einen Zentralkörper rotierende Gasmasse gelöst unter der Voraussetzung, daß die radiale Geschwindigkeit klein gegenüber dem Absolutbetrag der Geschwindigkeit und daß das Gravitationspotential allein durch den Zentralkörper bestimmt ist. Für den Mischungsweg wird ein Potenzansatz zugrunde gelegt. Die Rechnungen werden für ein zwei- und ein dreidimensionales Modell durchgeführt. Es ergeben sich zwei verschiedene Lösungen: Entweder der Drehimpuls des Zentralkörpers bleibt erhalten und ein Teil der Gasmasse fällt auf den Zentralkörper, während der Rest ins Unendliche entweicht, oder der Zentralkörper gibt Drehimpuls an die Hülle ab, die dann vollständig ins Unendliche wegströmt. Lösungen für gewisse Exponenten des Mischungswegs und für bestimmte Anfangsverteilungen werden angegeben.
On January 20-21, 1964, the Institute for Space Studies of the Goddard Space Flight Center, National Aeronautics and Space Administration, was host to an international group of astronomers, physicists, and Earth scientists, gathered to discuss the Earth-Moon system. This was the sixth in a continuing series of interdisciplinary meetings on topics in space physics held at the Institute. The conference was organ ized by G.J.F. MacDonald, of the University of California at Los Angeles, and by R.H. Dicke, of Princeton University. The working title of the conference was "The Dynamics of the Earth-Moon System," and indeed much of the contents of this proceedings volume is concerned with dynamical problems, but the conference dealt with many other topics concerning the Earth-Moon system, and hence we have adopted the shorter title for this volume. The conference proceedings have been somewhat rear·· ranged from the order in which the papers were actually presented. In doing this the editors are exercising hindsight to bring together closely related discussions. The first paper, by D. Brouwer, discusses the motions and moments of inertia of the Moon and their relation to the lunar figure and composition. From this discussion it emerges there remain many uncertainties in the motion of the Moon associated with the lunar composition and the distribution of its mass.
The evidence is now overwhelming that the earth is several billion years old; many different determinations by radiometric dating methods give an age close to 4.5 billion years. The criticisms of radiometric dating by creationists have no scientific basis, and can be justified only by arbitrarily rejecting well-established results of modern physical science. Their argument for a young (10 000yr old) earth from decay of the earth's magnetic field is completely refuted by empirical data and is incompatible with all currently-accepted principles of geomagnetism.-Author
Abundances in terrestrial and meteoritic matter indicate that the synthesis of D², Li⁶, Li⁷, Be⁹, B¹⁰ and B¹¹ and possibly C¹³ and N¹⁵ occurred during an intermediate stage in the early history of the solar system. In this intermediate stage, the planetary material had become largely separated, but not completely, from the hydrogen which was the main constituent of primitive solar material. Appropriate physical conditions were satisfied by solid planetesimals of dimensions from I to 50 metres consisting of silicates and oxides of the metals embedded in an icy matrix. The synthesis occurred through spallation and neutron reactions simultaneously induced in the outer layers of the planetesimals by the bombardment of high energy charged particles, mostly protons, accelerated in magnetic flares at the surface of the condensing Sun. The total particle energy was approximately 10⁴⁵ ergs while the average energy was close to 500 MeV per nucleon. Recent studies of the abundance of lithium in young T Tauri stars serve as the primary astronomical evidence for this point of view. The observed abundances of lithium and beryllium in the surface of the Sun are discussed in terms of the astronomical and nuclear considerations brought forward. The isotope ratios D²/H¹= 1.5 × 10‐4, Lie/Li⁷= 0.08, and B¹⁰/B¹¹= 0.23 are the basic data leading to the requirement that 10 per cent of terrestrial‐meteoritic material was irradiated with a thermal neutron flux of 10⁷ n/cm²s for an interval of 10⁷ years. The importance of the (n, α) reactions on Li⁶ and B¹⁰ is indicated by the relatively low abundances of these two nuclei. It is shown that the neutron flux was sufficient to produce the radioactive Pd¹⁰⁷ and I¹²⁹ necessary to account for the radiogenic Ag¹⁰⁷ and Xe¹²⁹ anomalies recently observed in meteorites. The short time interval, ∼ 6 × 10⁷ years, required for the radioactive decays to be effective applies to the interval between the end of nucleosynthesis in the solar system and the termination of fractionation processes in the parent bodies of the meteorites. It is not necessary to postulate a short time interval between the last event of galactic nucleosynthesis and the formation of large, solid bodies in the solar nebula.
Attempts of applying stellar polarization spectra to evaluation of magnetic fields of some types of stars are described.
There is an ancient Irish folk-tale, rewritten by Padraic Colum in a book called The King of Ireland’s Son, about a prince who goes out into the world to find the secret of his own childhood—the beginning and the end of the Unique Tale. His companion on the quest is Gilly of the Goatskin; and in the end, it appears that the boyhood of neither can be understood without the other.
La naissance de la Lune lors de l'impact d'un objet unique massif, de la taille de Mars, avec la Terre peut expliquer le moment angulaire specifique et les caracteristiques orbitales du systeme Terre-Lune. Les differences chimiques et de densite de la Terre et de son Satellite sont alors liees a la composition du manteau de l'impacteur. On discute de la validite de cette hypothese en montrant qu'il est possible de former un tel impacteur dans la nebuleuse proto-solaire interne
In the 1950's and 60's there arose a plethora of claims that the structure of evolutionary theory was intrinsically different from the structures of the theories of physics—and thus from the structure that philosophers of science claimed to be the structure of scientific theories. There were claims:
1) that evolutionary theory had no laws (Smart 1963);
2) that evolutionary concepts were so peculiar that their definitions violated the ordinary standards for definitions (Beckner 1959);
3) that evolutionary theory was not axiomatizable (Beckner 1959);
4) that evolutionary theory made no falsifiable predictions (Scriven 1959, Manser 1965, Smart 1963);
5) that evolutionary biology relied on teleological explanations which violated the deductive-nomological explanation form (Hempel 1965); and
6) that evolutionary biology made significant use of narrative explanations which also violated the deductive-nomological explanation form (Goudge 1961)
Science is accorded high value in our culture because, unlike many other intellectual endeavors, it appears capable of producing increasingly reliable knowledge. During the last quarter century a group of historians and philosophers of science (known variously as ‘theorists of scientific change’, the ‘post-positivist school’ or the ‘historical school’) has proposed theories to explain progressive change in science. Their concepts and models have received such keen attention that terms like ‘paradigm’ have passed from obscurity to common speech. In this volume, we subject key claims of some of the theorists of scientific change to just that kind of empirical scrutiny that has been so characteristic of science itself. Certain claims emerge unscathed — the existence and importance of large-scale theories (guiding assumptions) in the physical sciences for example. Others, such as the supposed importance of novel predictions or the alleged insignificance of anomalies, seem to be without foundation. We conclude that only by engaging in testing of this sort will the study of science be able to make progress.
We live in a society which sets great store by science. Scientific ‘experts’ play a privileged role in many of our institutions, ranging from the courts of law to the corridors of power. At a more fundamental level, most of us strive to shape our beliefs about the natural world in the ‘scientific’ image. If scientists say that continents move or that the universe is billions of years old, we generally believe them, however counter-intuitive and implausible their claims might appear to be. Equally, we tend to acquiesce in what scientists tell us not to believe. If, for instance, scientists say that Velikovsky was a crank, that the biblical creation story is hokum, that UFOs do not exist, or that acupuncture is ineffective, then we generally make the scientist’s contempt for these things our own, reserving for them those social sanctions and disapprobations which are the just deserts of quacks, charlatans and con-men. In sum, much of our intellectual life, and increasingly large portions of our social and political life, rest on the assumption that we (or, if not we ourselves, then someone whom we trust in these matters) can tell the difference between science and its counterfeit.
The dynamics of two dimensional jetstreams have been studied by following the evolution of simulation particle populations for different collision models. Collisions, independent of details of the collision model, rapidly lead to the establishment of a distribution of perihelion vectors of the form ~exp(-α(P-η)2), the characteristic time for this process being of the order of magnitude equal to the mean free collision time. Under appropriate conditions a radial focusing takes place. In terms of the varians of semi-major axis a focusing exceeding a factor 2 has been achieved. Necessary conditions for the existence of this radial focusing are a sufficient degree of inelasticity and the requirement that the dominant part of the velocity change in a typical collision is along the pre-collisional relative velocity vector. The properties of grazing collisions are especially important in this respect.
Nucleosynthesis associated with explosive carbon burning is reexamined, with the aim of providing a realistic prediction of the abundance of /sup 26/Al formed under such conditions. The sensitivities of the /sup 26/Al//sup 27/Al production ratio to variations in the temperature, the initial composition, and the degree of neutron competition from heavy nuclei are explored. Ratios of /sup 26/Al//sup 27/Al in the range 4 x 10/sup -4/ to 2 x 10/sup -3/ are found to result for the range of conditions considered. For a primordial solar-system ratio /sup 26/Al//sup 27/Alapprox. =6 x 10/sup -5/ (Lee, Papanastassiou, and Wasserburg), these production ratios imply that primitive solar matter was influenced by a nucleosynthesis event which could not have occurred more than a few million years prior to condensation.
At the end of the nineteenth century, Lord Kelvin's upper limit of only 20 or 30 million years for the age of the Earth was challenged by the American geologist T. C. Chamberlin, who showed that Kelvin's model of an Earth gradually cooling from an initial molten state was not the only possible one. Kelvin's limit was soon afterwards repealed by the new science of radioactivity, which yielded ages of a few billion years. While some geologists resisted this expanded time-scale, Chamberlin was the only one who could provide a comprehensive cosmogonical theory that did not submit to the epistemological superiority of physics and astronomy. In the 1940s, as radiometric age determinations improved in accuracy, they came into conflict with the expanding-universe cosmology — a conflict which the cosmologists eventually avoided by expanding their distance and time scales. In 1953, Patterson announced the result 4.5 billion years, which is still accepted as the best estimate for the age of the Earth. But geologists, liberated from Kelvin's limit, define the epoch of the Earth's formation as being outside the scope of their science, and their textbooks rarely give credit to the person who established the number that once seemed so important to accounts of the Earth's history.
In mixed leukocyte cultures prepared ’ from pairs of normal unrelated donors, some of the lymphocytes became transformed to large cells capable of mitosis. Subsequent experiments indicated that transformation was stimulated by genetically determined factors in leukocytes. A relationship to transplantation immunity was suggested. [The SCI ® indicates that this paper has been cited over 505 times since 1964.]
Comments are given concerning a paper by Bonsack and Greenstein (1960) on the abundance of lithium in T Tauri stars and on the origin of the solar system. The lithium evidence strongly suggests that planetary materials once were part of the sun as an outer envelope that was later thrown off; and then, perhaps through magnetic interaction, regained almost all the angular momentum initially present in the sun. The inference was drawn that T Tauri stars must be capable of manufacturing lithium, and it was estimated that there was at least ten times more lithium per gram of material on the surfaces of the stars than in the surrounding nebular material. (B.O.G.)
In the Preplanetary dust cloud, particle adhesion and aggregation Would have been most effective for magnetic grains. Enrichment of iron in the region of the inner planets could have occurred by a particle-size fractionation, the outward dispersal of small, metal-poor aggregates leaving behind only the larger aggregates enriched in magnetic particles of iron.
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In considering our space program, it is well to study objects that arrive from extraterrestrial sources quite without any effort or expense on our part. It is my purpose to discuss recent and older observations of meteorites and to draw some tentative conclusions from them. Meteorites are objects of variable structure and chemical composition, and a complete review of their properties is impossible in a brief time; therefore, this discussion will be limited to some specific features from which certain conclusions will be drawn. I believe that these conclusions will not be contrary to evidence that is not reviewed.
A survey of the abundances of elements in the ocean and sedimentary rocks as compared to their abundances in the weathered igneous rocks shows that carbon, nitrogen, oxygen as water, chlorine, bromine and boron are highly concentrated in the surface materials and that thicknesses of from 17 to 89 km of the outer part of the earth would be required to produce these elements if all of them now present in the igneous rocks were removed. A study of the available information indicates that many other elements would be concentrated at the earth's surface if chlorine, bromine and boron were concentrated there by a high-temperature volatilization process either from volcanoes or in an original high-temperature atmosphere of the earth. It is concluded that the removal of these elements from the outer parts of the earth occurred through solution in water at low or moderate temperatures ( 100 degrees C or less), since they are soluble and other elements are not. Iodine should belong to this group, but its position is uncertain because of doubtful analytical data. Sulphur may belong in some degree with the volatiles, i.e. carbon as methane or carbon dioxide, nitrogen as ammonia or molecular nitrogen, and water. It is shown that the low abundances of mercury and arsenic in the sediments are inconsistent with a temperature of formation of the earth's surface regions higher than a few hundred degrees centigrade. The presence of appreciable quantities of nitrogen in the igneous rocks indicates that this element was present in condensed phases during the earth's formation, and a survey of the conditions of stability of such compounds indicates temperatures of about 200 degrees C or less. It has not been possible to decide whether liquid water was present on the primitive earth.
Data on the composition of the satellites of the outer planets and the
composition and structure of planetary atmospheres are briefly reviewed
in light of simple models for the origin of the solar system and the
planets. Some crucial tests of present theories are suggested.