62 results found.
... Science Frontiers ONLINE No. 85: Jan-Feb 1993 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Why Intelligent Life Needs Giant Planets The two giant planets, Jupiter and Saturn, are 318 and 95 times more massive than the earth, respectively. Being so weighty they strongly perturb the orbits of comets, deflecting many away from the inner solar system, where we reside. Calculations by G. Wetherill, at the Carnegie Institution, reveal that if Jupiter and Saturn were only 15 times the mass of the earth, the earth would have been devastated every 100,000 years by giant comets, instead of about every 100,000,000 years, as indicated by the geological record. Under such intense bombardment, it would probably have been difficult for advanced life forms to develop. (Croswell, Ken; "Why Intelligent Life Needs Giant Planets," New Scientist, p. 18, October 24, 1992.) Comment. Reasonable as the foregoing assertion sounds, we do not really know what stimulates the development of new life forms. Actually, the fossil record reveals that some biological "radiations" occurred soon after great geological upheavals. That the Jupiter-Saturn "shield" was and is not completely effective is indicated by the heavy debris traffic mentioned above. From Science Frontiers #85, JAN-FEB 1993 . 1993-2000 William R. Corliss ...
Terms matched: 1 - Score: 42 - 15 May 2017 - URL: /sf085/sf085a04.htm
... Science Frontiers ONLINE No. 87: May-Jun 1993 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects The earth: a doubly charmed planet In SF#85, we learned that the evolution of advanced life forms on earth may have depended upon the protective influences of Jupiter and Saturn. These two giant planets can gravitationally deflect potentially devastating asteroids and comets away from the earth. It seems now that we are doubly lucky! Computer runs demonstrate that the presence of our large moon has stabilized the earth's spin axis down the eons. Presently, the earth's spin axis makes an angle of 23.5 with the plane of the earth's orbit (its "obliquity"). The well-known result is our yearly procession of seasons. Without the steadying effect of the moon, however, the earth's obliquity would probably have swung chaotically over much larger values. Such extreme changes would have been inimical to the development of life, particularly advanced life. As a case in point, the polar axis of Mars, with only two tiny moons to dampen its spin excursions, seems to have gone through many wild swings, as indicated in the figure. What deadly climatic changes must have wracked our sister planet! (Touma, Jihad, and Wisdom, Jack; "The Chaotic Obliquity of Mars," Science, 259: 1294, 1993. Also: Laskar, J., and Robutel, P.; "The Chaotic Obliquity of the Planets," Nature, 361:608, ...
Terms matched: 1 - Score: 24 - 15 May 2017 - URL: /sf087/sf087a04.htm
... Science Frontiers ONLINE No. 105: May-Jun 1996 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Eight Little Craters All In A Row The recent impact upon Jupiter of a procession of chunks from Comet Shoemaker-Levy 9 has encouraged geologists to look for crater chains here on earth. Such have been spotted on the moon, and it is unlikely the earth escaped such bar rages. Of course, older terrestrial craters are harder to identify due to the ceaseless geological activity here on earth. In the first 1996 number of Geophysical Research Letters, M.R . Rampino and T. Volk describe a possible swath of meteoric devastation across the North American Midwest. "Eight circular geologic structures ranging from about 3 to 17 km in diameter, showing evidence of outwarddirected deformation and intensive brecciation, lie within a linear swath stretching about 700 km across the United States from southern Illinois through Missouri to eastern Kansas. Based on their similar geological characteristics and the presence of diagnostic and/or probable evidence of shock, these structures, once classified as 'crypto volcanic' or 'cryptoexplosion' structures, are more confidently ascribed to hypervelocity impact. No other similar occurrence of aligned features is known, and we calculate the probability of a chance alignment to be less than 10- 9 ." The craters are all roughly the same age: 310-330 million years. Rampino and Volk suspect they were formed all at once by a string of asteroids or comets. (Rampino, Michael R., and Volk, Tyler; "Multiple Impact ...
Terms matched: 1 - Score: 17 - 15 May 2017 - URL: /sf105/sf105p09.htm
... Science Frontiers ONLINE No. 90: Nov-Dec 1993 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Alien Meteors Meteors or shooting stars are usually considered to be small fragments that have been broken off the asteroids plying orbits between Mars and Jupiter. If this belief is correct, meteors darting into the earth's upper atmosphere would have speeds less than 260,000 kilometers per hour. Any objects with significantly higher velocities must come outside the solar system. It has, therefore, been unsettling to find that quite a few meteors hit our atmosphere at speeds much higher than 260,000 km/hr. Radar measurements of 160,000 meteors by A. Taylor and colleagues, at a New Zealand site, found that about 1% (1500 meteors) struck the atmosphere with velocities greater than 350,000 km/hr. These speedsters must come from beyond the solar system. The question arising is: Whence all this interstellar debris? One hint comes from the fact that the aliens appear to come from the direction in which the sun and its family of planets are traveling through interstellar space. Evidently, this interstellar medium is far from a vacuum; it is strewn with flotsam and jetsam -- but from what smashed planets, moons, and asteroids? (Samson, Alan; "Radar Traps Visitors from Outer Space," Dominion Sun Times (Wellington), April 25, 1993. (Cr. P. Hassall) From Science Frontiers #90, NOV-DEC 1993 . 1993-2000 William R. ...
Terms matched: 1 - Score: 15 - 15 May 2017 - URL: /sf090/sf090a99.htm
... Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects In The Dark About Dark Matter During our last two-month collecting cycle, four "dark matter" items worth mentioning turned up. A wider search undoubtedly would have netted many more, because dark matter is worrying a lot of astronomers. Observations of visible matter, the only kind we can see directly, suggest that most of the universe is, in fact, composed of dark matter. This conclusion comes mainly from the belief that something unseen (dark matter) is tugging on visible matter, making it do things the laws of motion say it should not do. All visible bodies, therefore, seem to be careening about in a dense cloud of unseen, unknown masses. These might be dark, Jupiter-sized objects, black holes, and/or some exotic forms of matter. We must choose between the reality of dark matter or admit that something is awry with our laws of gravitation and motion when they are applied on a cosmological scale Now, let us examine those four darkmatter items from the recent literature: D. Lin, a University of California astronomer, has shown that the Large Magellanic Cloud that orbits around our own galaxy (the Milky Way) is being torn apart (" cannibalized") by the powerful gravitational pull of a dense cloud of dark matter surrounding the Milky Way. This dismemberment of the Large Magellanic Cloud cannot be explained by the gravitational forces exerted by the stars in our galaxy that we can see. Lin calculates that our halo of dark matter is ...
Terms matched: 1 - Score: 15 - 15 May 2017 - URL: /sf089/sf089a04.htm
... The earth's retinue of mini-asteroids. "Asteroids as big as houses pass near the Earth 100 times more often than anyone suspected. On an average day, about 50 asteroids measuring at least 10 metres across come closer to the Earth than the Moon, and each year about five such objects may hit the planet." (Second reference below.) These startling data come from D. Rabinowitz and coworkers at the University of Arizona, who have been scanning nearby space with a telescope fitted with supersensitive charge-coupled devices (CCDs). They have picked up astronomical objects that have escaped conventional instruments. Several sources have been suggested for this unexpected, threateningly large population of small asteroids: (1 ) debris hurled earthward from collisions within the asteroid belt located between Mars and Jupiter; (2 ) the breakup of a large object formerly in orbit about the earth; and (3 ) fragments blasted off the moon by impacts of large asteroids there. (Kerr, Richard A.; "Earth Gains a Retinue of Mini-Asteroids," Science, 258: 403, 1992. Also: Mitton, Simon; "HouseSized Asteroids Home In on the Earth," New Scientist, p. 16, October 31, 1992.) Comet Smith-Tuttle. At a conference in Sydney last October, astronomer D. Steele announced that comet SmithTuttle is heading towards a possible impact with earth on August 14, 2116. This 3.1 -mile-diameter chunk of ice would have the destructive power of 20 million megatons (1 .6 million Hiroshima ...
Terms matched: 1 - Score: 14 - 15 May 2017 - URL: /sf085/sf085a03.htm
... Science Frontiers ONLINE No. 86: Mar-Apr 1993 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Cosmic Snowballs And Magnetic Asteroids The genesis of a cosmic "dust bunny". The nebulous meteor of July 29, 1970, as observed over Dover, England. The great diversity of the debris swirling around the solar system is making life difficult for scientists trying to reconstruct solar-system history. At the high end of the density spectrum, we now have an asteroid that seems to be mostly metal (probably iron). This is the asteroid Gaspra, some 13 kilometers across, that the Galileo spacecraft encountered in August 1992 on its way to Jupiter. Scientists had not expected Galileo's magnetometer to flicker as it passed Gaspra at a distance of 1600 kilometers -- but it did. In fact, considering the inverse square law and Gaspra's small size, it was a magnetic wallop. Thus, Gaspra is the first known magnetic asteroid; and it is probably mostly metal. (Kerr, Richard A.; "Magnetic Ripple Hints Gaspra Is Metallic," Science, 259: 176, 1993.) At the low end of the density spectrum, we now find that Pluto's moon, Charon, and some of Saturn's moons have very low densities (1 .2 -1 .4 ), meaning they are probably mostly water ice. Such density figures come from direct observation of these objects' volumes combined with mass estimates from their orbital dynamics. (Crosswell, Ken; " ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf086/sf086a04.htm
... Science Frontiers ONLINE No. 128: MAR-APR 2000 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects The Ganymede Magnetic Paradox In December 1995, the Galileo space-craft was injected into orbit around Jupiter, thereby becoming the first known artificial satellite of this giant planet. In the five years that have transpired, Galileo has radioed back voluminous data about Jupiter itself and its four large Calilean satellites. These natural satellites have turned out to be a disparate bunch. Three have iron cores, but Callisto breaks the mold with an unusual core of mixed ice and rock. Europa probably possesses an ocean, and Callisto might also. Only one of Jupiter's large satellites, Ganymede, boasts a magnetic field. In fact, Ganymede is apparently the only satellite in the solar system to display an intrinsic, dipole magnetic field like the earth's . Although Ganymere's magnetic field is like that produced by a permanent bar magnet, its core is much too hot for permanent magnetism. Again like the earth, Ganymede's field is theorized to be generated by the convection of electrically conducting liquid in its core -- a dynamo of sorts. All well and good, but Ganymede is so small that it should have cooled off billions of years ago thereby freezing its metallic core. So then, whence its magnetic field? One way out of this box it to suppose that about a billion years ago Ganymede was circling Jupiter in an orbit that took it much closer to this ponderous planet. Then, Jupiter's powerful ...
Terms matched: 1 - Score: 66 - 15 May 2017 - URL: /sf128/sf128p04.htm
... , there seems to be a great dearth of small, cool, solid, water-and-carbon-rich planets circling beneficent suns. Can it be that we are looking for extraterrestrial life in the wrong places? Life may have originated and prospered on the multitude of sun-less aggregations of matter drifting through the void, some doubtless quite close to us. Myriad nomadic planets may be roaming our Galaxy free from the clutches of parent stars. Two teams of astronomers think they have detected 25 of these free-floating planets, and say there could be hundreds of millions of them wandering the Milky Way. These free-floaters or "drifters" were created when small clouds of gas and dust coalesced under gravity's urging. If such collapsing clouds were less than 80 times Jupiter's mass, they would not be able to sustain nuclear reactions and become long-lived stars. Many would be-come "brown dwarfs." Still smaller aggregations -- less than 14 Jupiters -- would never shine at all. These would remain warm for a while as they dissipated the gravitational energy that created them. Such small objects would be temporarily detectable by infrared telescopes. Hundreds of such infrared "point sources" turn up in sky surveys. These are the only "drifters" we can detect. "Drifters" that have already cooled off are certainly out there by the hundreds of millions. (Muir, Hazel; "The Drifters," New Scientist, p. 14, April 1, 2000.) Comments. Science-fiction writers have not ...
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... Science Frontiers ONLINE No. 133: JAN-FEB 2001 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Ribbons In The Sky November 18, 1999. North Atlantic Ocean. Aboard the m.v . Waterford enroute from Pto Bolivar, Columbia, to Ijmuiden. At 1832 UTC an azimuth of Jupiter was taken shortly after sunset. The sky in the vicinity of Jupiter was completely clear, no cloud of any type, with but a few small cumulus dotted around the horizon. About five minutes later, having completed the calculations, the observer again looked out to see a ribbon type cloud, broken in formation, stretching almost from [the] eastern horizon to [the] western horizon. If the estimated height (see below) is reasonably correct, then the bandwidth couldn't have been more than a few hundred feet, apparently more cigar-shaped in cross section than flat, the maximum axis being horizontal, the minimum vertical. The cloud was fairly consistent in density, and at a fairly stable altitude, not undulating or rippled, having the consistency of a small cumulus cloud (white and fleecy), but also translucent. Initially, it was thought to be a condensation trail, but this was shortly dismissed as it was considered too low (estimated to be less than 10,000 ft altitude, probably around 7,0008,000 ft). Both ends of the cloud were checked with binoculars but no aircraft was evident; however, as a yardstick, and by good fortune, one did appear ...
Terms matched: 1 - Score: 25 - 15 May 2017 - URL: /sf133/sf133p13.htm
... Science Frontiers ONLINE No. 131: SEP-OCT 2000 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Planetary Conjunctions that Changed the World On May 17, 2000, five solar-system planets (Mercury, Venus, Mars, Jupiter, Saturn) plus the moon slowly wheeled into a tight 19 arc. It was a notable heavenly conjunction. All manner of natural catastrophes were predicted but failed to materialize. It has been this way down recorded history. Universal deluges were anticipated during similar conjunctions on September 14, 1186, and February 19, 1524, but the weather refused to cooperate with the planets. Humanity survived nicely. This does not mean that historical upheavals are never correlated with planetary conjunctions. If a society believes strongly enough in the power of the stars and planets to shape human destiny, events may be correlated with the heavens. Such was the case in ancient China. In China, the "Mandate of Heaven" concept has been used since ancient times as both a framework for history and a guide to future actions. The basic idea is that Heaven awards ruling power to a sage-king because of his virtue. His descendants remain as Earthly deputies until they become corrupted, whereupon outraged Heaven gives signs in the sky that the Mandate has passed on to a different sage-king to continue the cycle. Three transfers of the Heavenly Man-date marked the beginnings of the Hsu, Shang, and Chou Dynasties. In fact, the tightest grouping of the five visible planets in the period from 3, ...
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... . No longer available. From our own moon's cratered surface to the red, rock-strewn plains of Mars, the Solar System is a fertile field for scientific research. Despite centuries of observation, each new spacecraft and telescope provides us with new crops of anomalies [Picture caption: One drawing of the Venusian radial spoke system] Typical subjects covered: The ashen light of Venus * The Martian 'pyramids' * Kinks in Saturn's rings * Continuing debate about the Voyager life-detection experiments * Neptune's mysterious ring * Evidence of water on Mars * The grooves on Phobos * The two faces of Mars * Lunar clouds, mists, "weather" * Ring of light around the new moon * Dark transits of Jovian satellites * Io's energetic volcanos * Jupiter as a "failed star" * Venus-earth resonance Comments from reviews: "The author is to be commended for his brilliantly conceived and researched volume", Science Books. 383 pages, hardcover, $18.95, 80 illustrations, 4 indexes 1985. 988 references, LC 85-61380, ISBN 915554-19-4 , 7x10 format. The Sun and Solar System Debris: A Catalog of Astronomical Anomalies Sorry: Out of Print. No longer available. Our sun, powerhouse of the Solar System and an enigma itself, is orbited by clouds of asteroids, comets, meteors and space dust These "minor objects" cause "major headaches" to astronomers searching for explanations. Typical subjects covered: Solar svstem resonances * Bode's Law and other regularities * ...
Terms matched: 1 - Score: 5 - 10 Oct 2021 - URL: /sourcebk.htm
