Most astronomical hypotheses on the causes of ice ages are dynamically untenable. Alterations in the amount of solar radiation, however, have long been recognized as a possible cause, but only with recent progress in the theory of stellar evolution has it become clear that such changes must occur. At irregular intervals the sun will pass, and will have passed, with low relative speeds through interstellar hydrogen clouds, and the gravitational action of the sun leads to an increase in the quantity of material falling to the surface with high velocity. The conversion of the kinetic energy of fall of this material results in an increase of emission at the solar surface. Increases of order up to about 10 per cent of the present total radiation could occur, and the process is such that the extra energy would be located mainly in the shorter wavelengths.

The standard big bang cosmology has the universe created out of a primeval explosion that not only created matter and radiation but also spacetime itself. The big bang event itself cannot be discussed within the framework of a physical theory but the events following it are in principle considered within the scope of science. The recent developments on the frontier between particle physics and cosmology highlight the attempts to chart the history of the very early universe.

At IAU Symposium No. 168 the presentation was divided into two parts:

1. I.Theoretical Foundations and
2. II.Observational Facts and Consequences

Properties of cometary dust with regard to bulk density, optical characteristics and sizes, derived from recent observations, are used to model scattering properties of cometary and interstellar grains. A wide range of astronomical observations are shown to be explained if cometary objects are hypothesised as a major source of dust grains in the galaxy.

Prof. Fred L. Whipple kindly agreed to be the chairman for all three panels, and introduced the next speaker, Prof. F. Hoyle, who spoke on ‘The Solar Nebula’. Hoyle: I would like to begin this contribution by considering the deductions we can make by comparing the gross chemical compositions of the planets with the composition of the Sun. For this purpose I have divided the planets into the three groups shown in

The second line gives the mass fractions in the Sun of the major constituents of the planetary groups, while the fourth line gives the factors by which the present masses must be multiplied to give the amounts of solar material needed to yield the appropriate amounts of main planetary constituents. The interesting points emerge that Jupiter and Saturn require the least amount of solar material, and that Uranus and Neptune on the one hand and the terrestrial planets on the other require approximately equal amounts. The total requirement is for ≈10-2 M ʘ This is less by a factor ≈10 than the amount postulated in many theories of the origin of the planetary system. However the amount we have now calculated can readily be seen to be consistent with angular momentum requirements.

This communication is concerned with recent computations made with the aid of the IBM 704. The problem was set up in collaboration with C. B. Haselgrove, using a method already described in detail. Facilities for making the computations were generously provided by the IBM Corporation.

Quantum effects in the early stages of some cosmological models are considered. Interactions between particles can be expressed in terms of the Dirac delta function, and the implications of the existence of both positive and negative frequencies in the Fourier expansion of this function are discussed.

Attempts to explain both the expansion of the universe and the condensation of galaxies must be very largely contradictory so long as gravitation is the only force field under consideration. For if the expansive kinetic energy of matter is adequate to give universal expansion against the gravitational field it is adequate to prevent local condensation under gravity, and vice versa. This is why, essentially, the formation of galaxies is passed over with little comment in most systems of cosmology. Yet the galaxies, and the clusters in which they are often found, are such an important characteristic property of the universe that it is unsatisfactory to dismiss their origin in the vague term “fluctuation phenomenon.”

The advent of radio astronomy provides a new observational tool for arriving at tests of the different theoretical cosmologies. The tests may be either wholly new, or revivals in a more cogent form of earlier work in visual astronomy.

Undoubtedly the outstanding advance of the last few years in theoretical radio astronomy has been the widespread recognition of the importance of synchrotron radiation by relativistic electrons. The possibility that high-speed electrons might be of importance in the solar problem was mentioned by Giovanelli [1] and by me [2] in 1948. But real quantitative development in this direction dated from the well-known paper of Schwinger [3] published in 1949. Schwinger's results were put into a form suited to the problems of radio astronomy by Alfvén and Herlofson in 1950, still from the point of view of emission from stellar surfaces, however. In 1953, Ginzburg [5] and Shklovskiì [6] took the additional step of suggesting that relativistic electrons exist in space and that they give rise to the emission from nonthermal sources.

This paper describes the system architecture of a newly constructed radio telescope – the Boolardy engineering test array, which is a prototype of the Australian square kilometre array pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a six-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least nine dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.

Flue-cured tobacco is sensitive to foliar and soil residues of off-target synthetic auxin drift. Aminocyclopyrachlor is a newly developed synthetic auxin herbicide that may be used in right-of-way applications for broadleaf weed and brush control. Aminocyclopyrachlor is considered a reduced-risk alternative in rights-of-way compared with similar compounds because of its low application rate and volatility risk. However, no research is available on the response of field-grown, flue-cured tobacco to aminocyclopyrachlor drift exposure. Research was conducted in 2009 and 2010 at the Border Belt Tobacco Research Station in Whiteville, NC, to determine the response of ‘NC 71’ flue-cured tobacco to five simulated drift rates of aminocyclopyrachlor (0.31, 1.6, 3.1, 15.7, and 31.4 g ae ha−1) and one aminopyralid (6.1 g ae ha−1) simulated drift rates applied pretransplant incorporated, pretransplant unincorporated, 3 wk after transplant, and 6 wk after transplant. All herbicide rates and application timings caused significant visual tobacco injury, ranging from slight to severe with increasing herbicide drift rates. Tobacco plant heights and fresh weights were reduced at all application timings receiving ≥ 15.7 g ha−1 aminocyclopyrachlor and the comparative aminopyralid rate.

A simple in-line filter is described which can be fitted into the milk tube of a. milking machine in order to detect clinical mastitis. It consists of a stainless steel mesh, on which the clots are retained, and it is fitted obliquely into a short length of clear plastics tube. The filter has been developed as an alternative to the fore-milk cup. Tests made over 9 months in a 60-cow herd show good agreement between the fore-milk cup and the in-line filter recordings. For general service production the filters are made by moulding.

The development of astronomical knowledge has now reached a stage where a precise description of the details of star formation has become a major issue. The enormous degree of contraction that occurs in stellar condensation, a concentration sufficient to increase the density of material from, say, 10-22gr./cm.3 up to ultimate values of the order of I gm./cm.3, gives a sure indication of the important part played by gravitational forces. Apart from gravitation, gas pressure must be accorded a significant place in the early stages of the process. It has been suggested that radiation pressure should also be included among the forces that determine the onset of condensation.

3. The essential requirement that the nova must satisfy in the above theory is that the total mass in the form of diffuse gaseous material must be of the order of 1/10 the solar mass, which requirement seems to be consistent with the observations of novae. Thus, although the theory applies explicitly to novae that break into two pieces of stellar mass having a gaseous filament drawn out between them (the pieces may have a mass ratio as great as 5/1), it seems clear that the discussion could be adjusted to include the case of novae following other models.

The process described above can be applied to the formation of non-solar planets. The mass of available planetary material depends upon such factors as the mass of the nova and its separation from the companion before outburst. It is to be expected that variations in these factors can lead to planetary masses that vary over a fairly wide range. It follows that since an appreciable fraction of the stars of mass comparable or greater than the solar mass are known to be members of binary systems, the number of planetary systems must be at least of the same order as the number of novae that have occurred in this class of star.

The presence of H2 molecules reduces the temperature of the cosmical cloud to a value that is small compared with the estimate given by Eddington. The necessary conditions for the molecules to persist at the capture radius of hot stars are investigated in the present paper, and it is shown that provided that the density of the cosmical cloud is sufficiently high the molecules will not suffer appreciable dissociation, and that radiation pressure will have only a negligible effect on the hydrogen. The critical density for a typical B star appears to be about 5 × 10−21 g. per c.c.

The rate of accretion of interstellar matter by stars as proposed in a previous paper is further discussed. It is shown that this amount, while sufficient for the evolution of the majority of stars, is insufficient by a factor of the order of 10 or more to give a satisfactory description of the general evolution of massive stars and close binary systems of small mass. Consideration of the possibility of increasing the rate of accretion for such exceptional stars leads to the conclusion that this can be carried out satisfactorily only by a corresponding increase in the density of the cloud. Although we were led to this view by considering all the factors involved in accretion and showing that only a change in the density could possibly produce the required increase, it is at once clear from the accretion formula, without detailed discussion of the other quantities involved, that the density is the only factor through which effects could be introduced that do not apply to all stars quite generally. By investigating the various factors in the galaxy affecting the density, it is shown that within 100 parsecs of the galactic plane, and also in local regions, the density may rise above 10−21 g. per c.c., which gives an increase of order 100 times the normal rate for stars lying in these regions. These suggestions receive independent corroboration from investigations by Jeans relating to extra-galactic nebulae which led to average densities also of order 10−21 g. per c.c., while a further argument from geological evidence shows that the average density of material along the sun's track must be higher than 10−21 g. per c.c. It remains to be seen whether future observations will succeed in confirming these suggestions indicated by the requirements of this theory of stellar evolution.