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Our earth has orbital motion, revolving once around the sun in about 365 days. Suppose that this orbital motion suddenly stopped completely, but everything else remained the same. How long would it take for the earth to plunge along a straight line into the sun? [...] Kepler's law applies to planetary orbits, whether…
But why should comets become more likely to hit us every million years? Here we launch ourselves into deep speculation. It has been suggested that the sun has a sister star, and the two orbit each other with a periodicity of about 26 million years. This hypothetical binary partner, which has never been seen but which…
As all regions below are replenished with living creatures, (not only the Earth with Beasts, and Sea with Fishes and the air with Fowls and Insects, but also standing waters, vineger, the bodies and blood of Animals and other juices {49} with innumerable living creatures too small to be seen without the help of…
It happened three times in the past that theoretical astronomers invented a new planet on the basis of indirect and circumstantial evidence. The first time was in 1845 when Adams and Leverrier independently deduced the existence of the planet Neptune from the perturbations which it had produced in the motion of…
Piet Hut, another Dutch astronomer fifty years younger than Jan Oort, decided to take seriously the possibility that comet showers are periodic. If they are periodic, the theory that they are caused by the random passing-by of alien stars cannot be right. If showers are periodic, they must be explained by a different…
To understand why comet showers occur, we go back to the Oort Cloud. The theory of comet showers was worked out by Jack Hills, an American physicist now at Los Alamos. He realized that the movements of the comets in the Oort Cloud are not entirely random. Comets in the cloud are generally moving in random directions…
So numerous are the objects which meet our view in the heavens, that we cannot imagine a point of space where some light would not strike the eye;—innumerable stars, thousands of double and multiple systems, clusters in one blaze with their tens of thousands of stars, and the nebulae amazing us by the strangeness of…
Astronomy affords the most extensive example of the connection of physical sciences. In it are combined the sciences of number and quantity, or rest and motion. In it we perceive the operation of a force which is mixed up with everything that exists in the heavens or on earth; which pervades every atom, rules the…
Our Sun is significantly enriched, having formed when the Universe was more than 9 billion years old in the plane of a spiral galaxy, one of the most enriched places in the Universe. Yet, when our Sun formed, it was still made out of — by mass — 71% hydrogen, 27% helium, and about 2% “other” stuff. If we convert that…
The material factors which ultimately limit the expansion of a technically advanced species are the supply of matter and the supply of energy. At present the material resources being exploited by the human species are roughly limited to the biosphere of the earth, a mass of the order of 5 X 10^19 grams. Our present…
In summary, the circumstellar shells of Dyson civilizations-at temperatures ~300 degrees K and radii ~1 a.u.--can be detected with existing telescopes and state-of-the-art infrared detectors in the 8-13-u window out to distances of several hundred parsecs. But discrimination of Dyson civilizations from naturally…
As to your reasoning of the inconvenience that a centre would become further removed from another centre than from the circumference of his own globe, though centres are of the same species while the centre and circumference are of contrary nature and should therefore be furthest removed from one another, I reply as…
Imagine the history of the galaxy with respect to extraterrestrial intelligence. Very early there were only first generation stars, no heavy metals and therefore no possibility of life, much less intelligence. That's Stage One. In Stage Two planets with heavy metals form from the starstuff processed in the previous…
I agree that a dreary comprehensive litany of who made what suggestion and which project official rejected it would be tedious (although me fact that the same idea arose in the minds of many different people - both in the science and the engineering teams - is worth noting), while at least some indication of the…
Mortal as I am, I know that I am born for a day, but when I follow the serried multitude of the stars in their circular course, my feet no longer touch the earth; I ascend to Zeus himself to feast me on ambrosia, the food of the gods.
The making of our week was another forward step in man's mastery of the world, in his reach toward science. The week was man's own cluster, not dictated by the visible forces of nature, for the planetary influences were invisible. By seeking astral regularities, by imagining that regularly recurring forces at a…
By the third century the seven-day week had become common in private life throughout the Roman Empire. Each day was dedicated to one of the seven planets. Those seven, according to the current astronomy, included the sun and the moon, but not the earth. The order in which planets governed the days of the week was…
Rational mechanics soon became a vast and profound science. The true laws of the collision of bodies, respecting which Descartes was deceived, were at length known. Huyghens discovered the laws of circular motions; and at the same time he gives a method of determining the radius of curvature for every point of a given…
We may distinguish the progress of each science as it is in itself, which has no other limit than the number of truths it includes within its sphere, and the progress of a nation in each science, a progress which is regulated first by the number of men who are acquainted with its leading and most important truths, and…
In the course of a redshift survey of galaxies brighter than R approximately equal to 16.3, 133 redshifts were measured in three fields, each separated by roughly 35 deg from the other two. If the galaxies in these fields were distributed uniformly, the combination of a galaxian luminosity function and the magnitude…