SICNALS TO MARS.

Taranaki Herald, Volume LV, Issue 14013, 18 September 1909, Page 6

SICNALS TO MARS.

The planet Mars, such .a conspicuous object in the sky at night during thr present month, is making one of its close approaches to the earth, and of course thr "popular" scientists are discussing the possibility of signalling to its inhabitant*. The Klea of a light signal, so often suggested, ignores tho conditions under, which Mara and tVu« earth are' visible to one another. Just now, whew we see the red planet in its full glory, the earth is virtually invisible -to the Martians, who see it, if at all, only as a tiny black -spot on the sun's disc. If every square yard of the dark hemisphere of the earth could be lit by blazing arc lamps, the illumination would be lost to the Martians in the fierc« light of the sun. Mr. Edgar Larkin, of Mount Lowe Observatory, California, tells ns in tho Scientific American that during this opposition the Martians might pop tho earth for a few* minutes before and after sunset and sunrise. In order to signal from the earth to Mars ju-.t now, a mirror fifty-two miles wid^ would be necessary, and the Martians would have to possess telescopes capable of showing an object a tenth of a second in diameter at a distance of 100,000,000 milr*. At present an astronomical mirror 100 inches in diameter is- being manufactured laboriously, and for a fifty-two-mile mirror the mere, manufacture of the glass, according to Mr. Larkin, would occupy two centuries. The cost would be anything from a million sterling upwards. Another million would have to be spent on a clock to keep the mirror turning always to .the same point in the heavens, or rather towards Mars, and then the whole arrangement would be at the mercy of cloud and fog. The other suggestion — an electrical signal — is also beyond our capacity. Tho professor who proposes to send a balloon ton miles into the air in order to catch Hertzian waves from Mars might indeed pick up vibrations from outside the earth, but he would be more likely to gather signals from some of the 2()00 wireless stations on the earth.