Free Who Built the Moon? by Christopher Knight, Alan Butler Page A

person standing at sea level at the equator is a little further away from Earth’s dense core than someone closer to one of the poles. Using a pendulum on the Moon would not produce any meaningful result because of what are known as ‘mascons’.
    The term mascon is an abbreviation for ‘mass concentration’ – regions of the Moon that have hugely dense material below the surface, rather than in the core as everyone would naturally expect. These mascons made it very difficult for spacecraft to orbit close to the Moon without continual adjustments to compensate for the variations in gravity. Some observers believe that it was this gravitational minefield that caused all of the problems for the early probes that were directed on the basis of a homogeneous gravity.
    The existence of mascons was discovered after Lunar Orbiter 1 went into orbit around the Moon on August 14 th 1966 and sent back high-quality images of over two million square miles of lunar surface, including the first detailed images of potential landing sites for the planned Apollo missions.
    This new discovery of gravitational ‘hotspots’ on the Moon had an impact on a man who is arguably the greatest science fiction writer of all time and an acknowledged inspiration to NASA. Arthur C Clarke combined forces with film director Stanley Kubrick to write and shoot the most realistic space adventure ever. When their film
2001: A Space Odyssey
premiered in April 1968, it stunned audiences across the world with its beautifully produced vision of the future.
    The plot of the film starts millions of years ago when our ancestors were still apelike creatures without speech or tools. There is a visitation from some undisclosed power in the form of a jet-black and perfectly finished rectangular monolith that stands upright. When touched by the probing fingers of the gang of primates at dawn the monolith somehow remaps their brains to begin a process that will take these proto-humans on the evolutionary road to intellectual development. As the camera pans up the length of the monolith the Sun and the Moon appear directly overhead as though an eclipse is about to occur. The scene then leaps forward to the beginning of the twenty-first century when a powerful magnetic anomaly is discovered just below the surface of the Moon in the Tycho crater and excavations are carried out to discover what is causing the effect. A black monolith, some four metres tall is uncovered and a team of experts sets out from Earth to investigate the clearly artificial phenomenon.
    The team travel to the Tycho crater as the Sun rises and wearing spacesuits they walk down a ramp into the pit where the monolith stands just a few metres below the surface. Like the man-apes millions of years earlier the team leader, Dr Floyd, is mesmerized by this alien structure and he touches it with his gloved hand. A moment later a ray of sunlight comes over the edge of the pit and strikes the monolith, signalling the end of the dark lunar night that lasts for two Earth weeks. This time, as we look up the monolith we see the Sun and Earth hovering directly above and almost touching. Then suddenly, the object transmits a signal in the direction of one of the moons of Jupiter (in Clarke’s novel version this was changed to Iapetus, one of Saturn’s moons).
    The ingenious idea that Clarke put forward here was astonishingly close to the real-world discovery of the lunar mascons that had been made around the time he was writing. The similarity between Clarke’s magnetic anomaly and the gravitational anomalies are obvious. We wonder whether Clarke was aware of the newly discovered mascons and whether that gave him the idea of a kind of trip switch placed on the Moon in the extreme past by some alien intelligence to trigger a signal that told them that creatures from the Earth had become smart enough to reach the Moon and spot a serious abnormality.
    What a brilliant concept!
    If an alien intelligence had indeed been