The road to knowledge

On the Isle of Lewis, part of an archipelago off Scotland’s west coast, ancient peoples constructed an arrangement of huge stones which survives to this day near

W. D. Woods, How Apollo Flew to the Moon, Springer Praxis Books,

DOI 10.1007/978-1-4419-7179-1 12. © Springer Science+Business Media. LLC 2011

the village of Calanais (pronounced ‘callan – ish’). This impressive 5,000-year-old monu­ment is believed by some to have been a means of predicting the more subtle motions of the Moon across the sky over an 18-year cycle. If true, then its Neolithic builders seem to have imbued the Moon with a spiritual significance that caused them to devote major resources to its construction.

Down the centuries and all across the planet, peoples have portrayed the Moon as a deity. The Greeks associated its changing appearance with three goddesses; Selene, He­cate and Artemis. The Romans likewise looked to Luna and Diana. Despite this deification of the Moon, one Greek philosopher, Hip­parchus, was able to determine its distance and size by clever interpretation of naked-eye observations. It would be nearly 1,500 years before Europeans learned to stand on the shoulders of Hipparchus by applying scientific principles to the gaining of knowledge.

Four hundred years ago, Galileo Galilei acquired an early version of the telescope and turned it towards the Moon. His written descriptions and drawings reveal that he saw

it not as a perfect celestial body that merely reflected the imperfect landscape of Earth. as some of his contemporaries believed, but as a world in its own right, with plains, highland areas and ranges of mountains. Although he. like others, called the dark areas ‘seas’, his perception was sufficiently developed to suggest that they were just as likely to be dry plains.

As the telescope and its use increased in sophistication, a series of maps were drawn by ever more capable selcnographcrs. notably by Giovanni Riecioli who instituted the scheme of nomenclature that is used today and which has gradually evolved to name most of the large features that can be seen from Earth. The finest maps of the pre-photographic age were drawn by Wilhelm Beer and Johann Madler in Germany using a telescope equipped with a micrometer to measure features using cartographic techniques. After its invention in the mid-1800s, photography became the staple medium of lunar research and good atlases were produced to show the near side with oblique lighting that displayed lunar topography well.

The question that most intrigued lunar scientists concerned the origin of craters – circular landforms that appeared ubiquitous on the Moon and whose sizes ranged from many hundreds of kilometres down to the limits of detection. Craters could be found on Earth, although their size seemed to be limited to a few kilometres at most, and all were associated with volcanoes. Many tried to bend the volcano hypothesis to explain the origin of lunar craters but it was a geologist. Grove Karl Gilbert, who postulated accurately that the major process responsible for the lunar landscape was impact, sometimes on an utterly cataclysmic scale. Volcanism did occur and was responsible for laying down the vast mare plains, but there are no volcanic edifices on the Moon that would rival a Mount Fuji, Mount Kilimanjaro. Mount Vesuvius or Mount Etna. Instead lunar volcanism produced low mounds with small vents at their summits.

Gilbert’s work was not fully acknowledged by the lunar science community for decades, but this difficulty in accepting the new occurs in science far more often than many people realise. Too many scientists were wedded to their grand imaginings of massive volcanic events to grasp how time and a rocky rain from space could form such consistent structures. They reasoned that if craters came from falling rocks, they should arrive from many angles and produce elongated craters. Lunar craters were notable by their circularity.

Generally, astronomers don’t like the Moon. Its shine swamps the feeble light they are trying to capture from immensely distant objects. However, they often use the Moon as a handy target when new telescopes are being tested. Thus, in the second decade of the twentieth century, an exquisite photograph of the impressive crater Copernicus was taken during tests of the 2.54-metre Hooker Telescope at Mount Wilson. At the turn of the 1960s. Eugene Shoemaker used this photograph to carry out an elegant study of crater morphology. His investigation finally drove home the importance of impact as the prime sculptor of the Moon’s face. The study was coupled with findings from ballistic trials that demonstrated how the extremely violent explosions that resulted from cosmic impacts would produce circular craters for all but the most oblique impacts. Related studies of the manner in which rock becomes shocked by impact enabled sites of terrestrial impacts to be identified. One

significant product of this knowledge was the dawning realisation that impact is still reworking not only the surface of the Moon, but also the surface of Earth.

As the space age developed and Cold War politics aimed the United States to the Moon, lunar scientists found themselves with an undreamt-of opportunity to extend their discipline which, up to that point, had accomplished about as much as could be achieved using Earth-bound photographs made blurry by the roiling atmosphere. NASA was aware of the bureaucratic danger of justifying its existence only on Kennedy’s political whim, so it turned to science as a valid, long-term rationale for flying men to the Moon. Although the primary driver for Apollo was international prestige and technical supremacy, science would give the crew of the first mission something useful to do after planting the national flag, and it would then go on to underpin the missions that followed.