THE SUN

Otago Daily Times, Issue 25456, 10 February 1944, Page 6

THE SUN

DISTANCE FROM THE EARTH By Douglas C. Berry, F.R.A.S. Perhaps the most accurate of all astronomical calculations was recorded last week in a single small column. Even then it was two years overdue as it was announced in 1942 that the Astronomer Royal, Sir Harold Spencer Jones, had found a mean parallax for the sun of 8.79, which puts the sun at a mean distance of 93,005,000 miles from the earth. In these new calculations the Astronomer Royal tells us that the margin of error is 9000 miles corresponding to the apparent breadth of a human hair at 10 miles or a half-penny at 3250 miles. “This is by far the most accurate measure of the sun’s distance ever made,” announced the Astronomer Royal. “The final word has been said on this historic problem for many years to come.” Enormous though these 93,005,000 miles between the sun and the earth may seem, astronomically speaking it is just a “stone’s throw away.” The nearest star outside the solar system, Proxima Centauri, is 4.3 light years away, or roughly two hundred and fifty million million miles away. This is, light takes 8 minutes 20 seconds to come from the sun and 4 years 108 days from Proxima. Some conception of the immensity of time, and space may be gathered from Hendrik Van Loon’s famous definition of eternity. “Imagine,” he says, “an island as large as Britain in the middle of an ocean. Suppose that every million years a little sparrow came and sharpened its beak on the rock. When the rock was eventually worn away a second of eternity had passed away." The sun is 864,000 miles in diameter, and its mass is 332,000 times that of the earth. It rotates on its axis every 24.7 days at the equator. When we consider the ruddy coloured stars, Antares, Betelgeuse, and. Aldebaran, which have diameters above 250 million miles, we are inclined to think that the sun is comparatively small; but the sun was not always “ small.” Actually it is becoming smaller by four million tons every second. Even so, the sun and its system of planets, asteroids, and comets, have an expectation of life of millions of years to come. The heat at the centre of the sun is said to be about 60,000,000 degrees. This means that if a piece of the sun’s centre the size of a sixpenny piece was placed on top of the Post Office everything would shrivel up in white hot heat over the whole of Otago and Southland.