It will be seen that the sequence of figures shown in the first four examples is precisely that shown in the theoretical figs. 4 to 6. The series could easily be extended to include observed nebulae of the shapes shown in the theoretical diagrams i and 2, but such nebulae are not interesting objects photographically. Statistical researches by Hubble make it highly probable that there is a continuous sequence of nebulae having the shapes shown in the theoretical diagrams r to 6, only the last half of this series being exemplified by the photographs shown in Plate I. The last photo graph of all on this plate shows a nebula of the same general type viewed from another angle; there is little room for doubt that this nebula is physically very similar to that shown in fig. 5, the difference in appearance arising solely from the different angle of view.
The amount of rotation of some of the nebulae is so great that, at some stage of their shrinkage, matter was spilled out into their equatorial plane and has remained in this plane ever since; see Plate II. for a number of instances of this formation. The matter left behind in this way would at first form a continuous nebular medium, a sort of counterpart of the parent medium out of which all the nebulae were formed, except that its density must have been some I o,000 million times as great, being of the order of io 21 instead of io 31 grammes per cubic centimetre. The process of gravitational instability must operate in this medium also, but as a consequence of the far greater density, the masses of the resulting condensations must be far less. Calculation indicates that the amount of matter in each condensation must be about equal to that in a newly-born star.
For a long time this hypothesis appeared to give the most likely ex-planation of the origin of the solar system, but to-day the available evidence both of observational astronomy and of mathe matical theory is unfavourable to the explanation. The sky pro vides a great number of examples of the fate awaiting stars which rotate too fast for safety; it is not to found a family but to break in two. And when the mathematician follows out the details of the process. imagined by Laplace with reference to the special case of the solar system, he finds that there is nothing wrong with the general mathematical theory, but that its application to the solar system leads to numerical values which cannot possibly be reconciled with those observed. Thus there is a consensus of opinion that Laplace's hypothesis must be abandoned as an explanation of the origin of the solar system, not because it is wrong in theory, but because it fails in practice.
This is the basis of the Solar Nebula Hypothesis – that from a cloud of dust and gas, our Solar System formed to what we see today: a Sun, four rocky terrestrial planets, an asteroid belt, four “gas-giant” planets, Pluto and the other Kuiper Belt Objects, and the Oort cloud (and the variety of debris within).
The efficient market hypothesis suggests that there is no trading system based on currently available information that could be expected to generate excess risk-adjusted returns consistently as this information is already reflected in current prices.
The Uncertainty Hypothesis from Herzog’s article holds that the author indulges himself in such gamesmanship to convey the message that closure is non existent, and that there is only uncertainty which constantly defers the ending of everything.
The gas set free from a nozzle in the laboratory does not form condensations under its own gravitation, the reason being that the mass of matter involved is so small that the gravitational attraction of the matter on itself is inappreciable ; it is only when matter is set free on a colossal scale that gravitational instability can come into operation. The scale of the galactic nebulae is amply big enough, but that of jets of gas in the laboratory is too small. Calculation shows that any ejection of gas from the equator of a rotating star is also on too small a scale for gravi tational instability to get any grip, so that the ejected gas must just scatter into space like gas out of a tap.
The first products of gravitational instability, the extra-galactic nebulae, proved to be incomparably greater in size than Laplace's imaginary rotating nebula, but each of the smaller masses of gas formed by condensation out of the outlying parts of these nebulae is in effect a gaseous nebula of just about the size and mass imagined by Laplace. If, then, the younger generation of nebulae, as they rotate and shrink, meet with the same sequence of expe riences as their parents before them, we have the course of events postulated by Laplace taking place on the scale imagined by Laplace, and we need not look farther for the mode of birth of the solar system. But mathematical theory prohibits such a simple solution to the problem.
The binary systems which can be said with fair certainty to have been formed by fission due to rapid rotation are mainly of the class known as spectroscopic binaries. The telescope generally shows these as a single point of light, but the evidence of the spectroscope reveals the fact that the apparent point of light really represents two stars describing orbits about one another. Another class of binary systems; which outnumbers these by perhaps 20 to one, consists of pairs of stars which describe orbits about each other and show visually as two distinct points of light. These are known as visual binaries. The dimensions of the orbits of many of these are so great that they can hardly have been formed by the fission of a single star and it is more likely that they are the remains of independent but adjacent condensations in the nebula from which they were born. These visual binaries provide evidence as to their ages which is in general agreement with the story told by the spectroscopic binaries.
This suggests very forcibly that the outer regions of the nebulae are the birth-places of the stars. Condensations in process of forming may be seen in the outer regions of the nebulae shown in Plate I., and at various times actual unmistakable stars have been photographed in the outer regions of the nearer of the extra galactic nebulae, although it is significant that all efforts to find them in the inner regions of the same nebulae have failed.
The two-Gospel hypothesis provides an effective response regarding these literary and historical similarities with the Gospels of Matthew, Mark, and Luke through a balanced approach utilizing both internal and external resources to address the long standing debate regarding the synoptic problem....
The astrono mer is familiar with bodies of the required size; they are the spiral and other extra-galactic nebulae. The sun and all the stars we can see with the naked eye belong to a single colony of stars, the "galactic system," which is bounded by the milky way alto gether. Outside this system lie the bodies known as "extra galactic nebulae," at distances so great that light from even the nearest of them, although covering i 86,000m. every second of its journey, takes something like I,000,000 years to reach us. The masses of these nebulae are of the order of ion or I,000 million times the mass of the sun, and so are of precisely the magnitude required by the hypothesis that they have been formed by gravi tational instability out of a continuous primaeval gaseous medium. Their dimensions are comparable with the dimensions of the whole galactic system, and are so enormous that, in spite of their immense distance, the astronomer can study their shapes and photograph their general appearance with comparative ease. A selection of photographs is shown in Plate II.