WHITHER IS OUR EARTH TRAVELLING?

Oamaru Mail, Volume XLIV, Issue 14704, 3 June 1920, Page 8

WHITHER IS OUR EARTH TRAVELLING?

(Bv Charles Nevers Holmes.) 1

Our little planet home—this world of ours-r—possesses several motions, all of whieli are in progress at" the same time. Of these motions the swiftest and- the most important are three, two of which are very well known. • ■ We aiiknow .of our earth's diurnal or daily ; motion—its ; rotation upon itsaxis from west to east, whereiiy the sun rises in the east and sets in the west. We all know of its annual or yearly motion—its revolution - around the sun from west to whereby we behold the apparent revolution of suns and constellations - around the • polestar from east to west, as well as the seeming movement of our sun, eastward, along the zodiacal constellations. As we ..well know, our earth's daily motion upon.-its axis causes the alternation of light'and darkness, of day and nighty while its yearly motion around the sun causes .the seasonal, cycle of spring, summer, autumn, and | winter. But, in addition to these I diurnal and annual motions, it possesses a third . swift and remarkable motion-—its movement out into the illimitable abyss of the universe. . . Its diurnal and annual motions are, of course, wholly peculiar to'our world, whereas in its. movement out into space it is associated' with the sun and all the other members of the solar system. That is, the entire solar system —the sun, the earth, the . moon,. Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and so on —is travel-* ling speedily through space, somewhat like a firmamental fleet under sealed orders. ' ' All the units of this firmamental fleet are bound together, as if by invisible chains, the sun being their pivotal point and a sort of flag-ship. Every member of the system is moving out into the vast abyss of the cosmos at exactly the same speed otherwise . some of our planets and their satellites; would soon be left behind. The changing- domain in space occupied by our swiftly travelling solar system approximates . six billions ot miles' in width, since Neptune, at present our outermost known planet, revolves around tile sun at a- mean dis"tance of about 2,792,000,000 miles. This third motion possessed by our little planet'; 1 home, which may lie termed our solar, system motion, is much swifter than the earth's diurnal rotation and considerably slower than its annual: revolution. " Its--daily-rotatiori. at the surface, .of the globe, lias speed of about 1000 miles an hour, or 500 yards per second—which is equivalent to about nine million miles in a year. Its vearly revolution has a speed of 18 miles per second —which amounts, to almost 584,000,000 miles each year. In other words, .our world revolves/round the sun approximately 65 times' as fast as it rotates around its axis. Its forward motion into space has been calculated at about 11 miles per second. That is to say, our planet home is speeding through its region of the universe at a rate of approximately 950,000 miles each day. or 347,000.000 miles each year. It is evident, therefore, that this third motion of our earth is about 38 times as fast as its progress from day to night, but not much more than half as fast as its progress..from season to season. : The earth is like an old-fash-ioned spherical cannon-ball shooting through the illimitable ether, hnd, although this terrestrial projectile is, comparatively speaking, a small body, its "solar system velocity" approximates IS times that of a shell®from a modern naval gun; Indeed, such a pace would carry our world across the United States, from the Atlantic to the Pacific, in a little more, than four minutes, .or completely round its own surface in about 38 minutes, it would travel as far as the moon within six hours, as far as the sun within 98 days, and entirely across the changing domain occupied by the solar | system in something less than 18 years. ' Yet, despite the fact that our sun and its system are travelling about 11 miles each second, their motion in space seems very slow compared with that of. some other solar svstems. It has been I calculated that one of - the swiftest of J these. "Groombridge 1830," moves more than 18 times as rapidly, so that j it- would speed from earth to moon within 20 minutes, and across our solar system in a little less than a year

Respecting the "sealed orders" under which our planet ship is sailing so swiftly amid the vest ether ocean surrounding her, we aboard her are in utter ignorance. Wo believe that our comparatively tiny craft was launched upon her mysterious voyage according to the laws and processes of the universe, but we do not know how long that voyage mav be or what outside conditions may be governing it. We do not know whether our course will be straight ahead—for a. short time or for eternities —or whether our course is on an orbit, possibly around some other sun. visible or invisible. . It may be that our solar system is travelling upon an immense orbit .around some other solar system, very much as our earth is revolving around the sun on a comparatively small orbit. Man's astronomical science-is not yet old enough to have detected such

vast orbital revolution; but it seems more probable to suppose that oursystem is free from any outside condition or control, and that our little planet ship is sailing swiftly straight ahead —to ultimate disaster or to safety—amid the illimitable abyss of the universe.

Nevertheless, although he has been studying astronomy for only a few centuries, man does know in what general direction amid firmament his little earth is travelling. Yeirs ago Sir Wm. Herschel announced that our sun and its planets were speeding toward the star Lambda in the constellation of Hercules. To-day, after a score or so of calculations respecting this "apex of the sun's ; way," it is agreed-that outsolar system motion is toward a, point on the borders of that dim and distant group of stars. Toward -this firmamental point, then, our planet home is travelling with a velocity - approximating 347,000.000 miles each year, or thirty-five billion miles each century; Now, between our earth and Alpha Centauri, the nearest known sun of night, there, is a stupendous gap of space about twentyfive trillion miles in extent. It is: easy to calculate that our world can-, not traverse this vast stretch in less time than seven hundred and twenty centuries.But some of the stars in the constellation of Hercules.. are believed to be twinkling at a distance from five to seven times as far as it is to the sun Alpha Centauri, so that it would take our earth approximately 4300 cen-" turies, or 430,000 years, to reach the constellation toward which it is speeding. Our planet ship would reach Hercules in that time, provided no terrestrial disaster occurs and. that. Hercules remains motionless. However, all the Willis and satellites in Hercules are in motion, just as- the sun and its satellites of our solar system are in motion, and it is probable that within future centuries astronomers 7 will discover that we are moving toward some other constellation. Since the beginning of the Christiain era; we must have travelled at least 665 billion miles through space, or mere than 3500 itmes as far as "it is to the sun and back to earth. In the " future, .provided nothing interferes ■! with its progress, our planet ship will sail swiftly on and on- through innumerable ages, far, far beyond the domain in space now occupied by the. constellation Hercules. In time it may react tlie iMilky Way and even still more remote regions, but it is probable that long before that era our world will "eoi&e to an end." Before' the end of our . world, most, if not all, of-the mysteries ofastronomy may be revealed, and it is possible that- even in our own generation we' shall- be able to answer more fully this interesting- astronomical . question, "Whither is our plahet-Jiome travelling? . "