large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb_36
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb
English
12904
Working backward, however, it seemed that 25 million years ago, the sun must have been so large as to fill the earth's orbit. Clearly the earth could not then have existed. In that case, the maximum age of the earth was only 25 million years. WORKING BACKWARD HOWEVER IT SEEMED THAT TWENTY FIVE MILLION YEARS AGO THE SUN MUST HAVE BEEN SO LARGE AS TO FILL THE EARTH'S ORBIT CLEARLY THE EARTH COULD NOT THEN HAVE EXISTED IN THAT CASE THE MAXIMUM AGE OF THE EARTH WAS ONLY TWENTY FIVE MILLION YEARS
of meteors held out—even millions of years. This, however, would mean that the sun’s mass would be increasing steadily, and so would the force of its gravitational pull. With the sun’s gravitational field increasing steadily, the length of earth’s year would be decreasing at a measurable rate—but it wasn’t. In 1854 Helmholtz came up with something better. He suggested that the sun was contracting. Its outermost layers were falling inward, and the energy of this fall was converted into heat and light. What’s more, this energy would be obtained without any change in the mass of the sun whatever. Helmholtz calculated that the sun’s contraction over the 6000 years of recorded history would have reduced its diameter only 560 miles—a change that would not have been noticeable to the unaided eye. Since the development of the telescope, two and a half centuries earlier, the decrease in diameter would have been only 23 miles and that was not measurable by the best techniques of Helmholtz’s day.  OF YEARS THIS HOWEVER WOULD MEAN THAT THE SUN'S MASS WOULD BE INCREASING STEADILY AND SO WOULD THE FORCE OF ITS GRAVITATIONAL PULL WITH THE SUN'S GRAVITATIONAL FIELD INCREASING STEADILY THE LENGTH OF EARTH'S YEAR WOULD BE DECREASING AT A MEASURABLE RATE BUT IT WASN'T IN EIGHTEEN FIFTY FOUR HELMHOLTZ CAME UP WITH SOMETHING BETTER HE SUGGESTED THAT THE SUN WAS CONTRACTING ITS OUTERMOST LAYERS WERE FALLING INWARD AND THE ENERGY OF THIS FALL WAS CONVERTED INTO HEAT AND LIGHT WHAT'S MORE THIS ENERGY WOULD BE OBTAINED WITHOUT ANY CHANGE IN THE MASS OF THE SUN WHATSOEVER HELMHOLTZ CALCULATED THAT THE SUN'S CONTRACTION OVER THE SIX THOUSAND YEARS OF RECORDED HISTORY WOULD HAVE REDUCED ITS DIAMETER ONLY FIVE HUNDRED SIXTY MILES A CHANGE THAT WOULD NOT HAVE BEEN NOTICEABLE TO THE UNAIDED EYE SINCE THE DEVELOPMENT OF THE TELESCOPE TWO AND A HALF CENTURIES EARLIER THE DECREASE IN DIAMETER WOULD HAVE ONLY BEEN TWENTY THREE MILES AND THAT WAS NOT MEASURABLE BY THE BEST TECHNIQUES OF HELMHOLTZ'S DAY
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb
file
download/librilight/large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb.flac