Forty Years On The Pacific/Explanation of Difference of Time
By An American Naval Officer
THE sketch below represents the view of the earth that would be obtained by an observer stationed in a balloon above the North Pole. The circle would be the equator. The rotation of the earth and the apparent movement of the sun are shown.
Now, suppose the sun is as shown over the meridian passing through Greenwich, England (0° longitude): it will be noon at that place. At A, the sun is not yet overhead, so it will be some time before noon. At B, the sun has passed and is to the west; therefore, it is afternoon. So it will be seen that west of Greenwich (west longitude) as at A, the time in England is earlier than at 0°, and east of Greenwich, the time is later.
The earth revolves once in twenty-four hours, so at 180° longitude, the difference in time is twelve hours. Let us suppose two points—one 179° 5959" west longitude; the other, 179° 5959" east longitude. At the first point, it will be practically twelve hours earlier than at Greenwich, and at the second, twelve hours later, so the total difference is twenty-four hours. For this reason, when crossing the 180th meridian to the westward, we lose a day, and in the opposite direction, we gain a day.
Since the circumference of the earth may be reckoned as twenty-four hours and is 360°, time changes one hour; for every fifteen degrees of longitude, which is equal to nine hundred nautical miles on the equator.
Longitude west, Greenwich time best, Longitude east, Greenwich time least.
On one trip I made between New Zealand and Australia, in the year of the San Francisco fire (April, 1906), one of the passengers of the Moana was the noted American comedian, Willie Collier. We were traveling west, which means that we had to add about half an hour to every twenty-four hours' run. In other words, passengers traveling west on a fifteen knot an hour steamer, can lie abed half an hour later daily; while, if one is traveling east, he must rise half an hour earlier.
We made up daily a Calcutta sweepstake on the run, and one young actor—I think it was Jack Barrymore—bid in the number of the ticket that won. Collier protested, holding that Barrymore had an advantage, because he was aware of the difference in time, having allowed twenty-five minutes over the twenty-four hours in his calculation when bidding. In fact, Collier wanted the winner to divide the sweepstake. Freddie Shipman settled the dispute, and thus bloodshed was avoided.
During this trip we saw a waterspout, five miles on our starboard, near Lord Howe Island.