The earliest speculationsabout contact with otherworldly beings, in fact, hoped for contact withinhabitants of the Moon or of other planets circling our Sun.

After all, in the 1800s manyastronomers thought that -- at least theoretically-- life might well exist throughout the solar system. The trick was togo from theory to a concrete experiment, all in the days before powerfulradio telescopes. And though no large-scale attempts were ever made tocontact extraterrestrials within our own solar system, there was no lackof inventive proposals.

Undaunted by the vast distancesbetween Earth and its sibling planets -- with a journey to our Moon stillfar in the future -- alternative strategies were suggested, making useof the technology of the day.

Crop geometry lessons

One technique, drawing onbasic geometry, was proposed in the 1820s, some say by the brilliant mathematicianCarl Friedrich Gauss.

In this scheme, huge geometricalpatterns would be sketched out on the Siberian forests by plowing downvast stretches of trees and planting fields of wheat in their place. Usingthis approach, the Pythagorean theorem could be etched out, providing avisual example of every geometry students favorite equality: a²+ b² = c².

In this 19th-century precursorof crop circles, any inhabitants of the Moon inclined to look Earthwardwould see that terrestrial engineers were privy to the secrets of Greekmathematics. In turn, we might hope for a response, perhaps a tutorialon the lunar equivalent of Euclids Elements. However, even afterthe advent of bulldozers and John Deere tractors, the experiment was nevercarried out.

The burning desert

All well and good for daytimesignaling, but what about when the dark side of Earth faces the Moon? JohannJoseph von Littrow suggested an alternative: digging a huge, circular canalinto the Sahara Desert, many miles in diameter, and filling it with kerosene.When lit, it would provide evidence of human intelligence.

While there would be no guaranteethat Moon folk would understand the true significance of the circle forEarthlings, von Littrow reasoned that a picture would convey much morethan the arbitrary symbols: r².

Since the Sahara is on thedark side of Earth only half of each day, von Littrows plan still didntexpand signaling to a 24-seven schedule -- even on a theoretical basis.And in practice, his plan was not carried out any further than the earliersuggestion to signal with fields and forests.