Each northern autumn, the days shorten and the nights lengthen until they reach a point of balance at the autumnal equinox in late September. The full moon at this time of the year is known as the harvest moon. During these evenly matched days and nights of fall, as the sun sinks beneath the western horizon, the moon rises in the east to take its place and cast strong moonlight most of the night if the weather remains clear.

The time around the autumn equinox was the traditional time for farmers in northern latitudes to be harvesting their crops. The farmers, always mindful of changes in the weather that can ruin a harvest, were ever-ready to take advantage of the cooling nights lit by the autumn moon, and spent those nights gathering in more of the harvest. A month later, as the moon again becomes full, there is almost as much light, but this later, cooler moon of autumn is named for the hunter, not the harvester.

The moon gave significance not merely to the hunter and the harvester. Its cycles were those by which peoples of ancient Egypt and in Africa timed ceremonies relating to planting crops, fertility rites and rites of passage. There are still farmers who feel that certain crops should be planted in relation to the phases of the moon, that root crops should be planted during the dark period without moonlight and that fruit crops should be planted during the moon's light phase.

The moon and its light are mysterious. I saw a ghost once by moonlight. Moonlight and moonbeams are not always so alarming, though, and there is whimsy in the moon too. In certain parts of the world people look at the full moon and see there, in its face, the "Man in the Moon," while in China and Japan folk see a rabbit; interestingly, the Aztecs also worshipped the Volcano Rabbit of the Moon.

The "soft-seeming globe in the night sky" (D. H. Lawrence) is virtually the same age as our Earth, so that all life here has evolved under its heavenly influence either via its gravitational or tidal pull, or under its soft nocturnal light.

Nevertheless, the influence of the moon on life in general and on humans in particular has somehow remained the realm of folksy fantasy rather than hard science. With the notable exception of the lunar influence on the human menstrual cycle, scientists have shied away from any study of moon-related behavior.

There are those that assert that more crimes are committed around the time of the full moon, especially those involving arson, aggression and kleptomania. Psychiatric ward workers readily report that their charges become more unruly when the moon becomes full; one I spoke to said, "We always seemed to have a significant number of people going off at the full moon." Not for nothing were such inmates known a century or so ago as lunatics.

The moon, it seems, does have a powerful influence, even if it is one that people are loathe to admit. Even NASA was moonstruck for many years in the 1960s and 1970s. There are those of us who watched in awe as the first time-lagged pictures were relayed back from space showing a human figure standing on the moon. Here at last was the final, incontrovertible proof that the lunar surface did not consist of cheese (as Wallace and Gromit would still have us believe).

Final proof too that there was no man already there as Europeans believed, nor the giant rabbit of the Aztecs and Asians. There were those of us in awe of the science, of the adventuresome crew of Apollo 11, of the footprints in the lunar dust and of the sentiment of the whole venture.

However, there were those for whom there was no awe, such as Pablo Picasso, who apparently said, "It means nothing to me. I have no opinion about it, and I don't care."

Perhaps for him, it was merely a venture to a dead rock -- the ultimate lunacy, to spend billions of dollars traveling from a rock with life to one without. There are still others who claim the whole voyage was a fantasy, created on a film set somewhere in Hollywood. Perhaps those nay-sayers had also spent a little too much time staring at the moon.

Our Earth's natural satellite, although averaging more than 380,000 km from us, was, until the advent of electric lighting, by far the most powerful light in the night sky. Even today, with light pollution streaming skyward from every major and many a minor urban area, the reflective surface of the moon, when it is full, still provides the most significant source of night light. On full-moon nights, moonlight can be bright enough to read by, and that means it is more than light enough for many other creatures to go about their lives.

Animals and birds normally only active during daytime take advantage, like the harvesting farmers, and go out to feed again at night when the moon is full. I have watched as geese and ducks fly to roost as the sun sets, yet fly out once more to their foraging grounds when the moon rises, not wasting a moment of precious feeding time.

The light that the moon reflects is but one of its ways of affecting life here on earth. Its most significant means of influence is by driving the tides that ebb and flow across the world's oceans, turning mudflats into shallow seas, covering coral reefs, flooding mangroves, forging up rivers in tidal bores, sweeping beaches clean, scouring channels, sucking, pulling, driving, swirling.

Invisible grasping fingers of gravity from the moon and the sun cause whole oceans to bulge, only matched by the bulge resulting from the Earth's own spin. As the world spins round, these bulges raise tides; two highs and two lows, which rise and fall against the shores of the world every 24 hours.

At the full and new moons, the tides are highest, swamping even the highest of salt marshes. These are the spring tides and they are to be feared when backed by storms from offshore, for then they can bring severe flooding, and when the sun and moon are exactly aligned at the vernal and autumnal equinoxes the greatest spring tides of the year occur.

Between the spring tides, when the moon is in the first and third quarters, fall the lowest tides, known as neap tides, an ancient Anglo-Saxon word.

Through the tides, the moon exerts its most powerful influence on the inter-tidal life around the world's coastlines, driving their daily patterns of life and their reproductive cycles.

Perhaps the British playwright Christopher Fry was right when he wrote "The moon is nothing, But a circumambulating aphrodisiac, Divinely subsidised to provoke the world, Into a rising birth-rate."