Perigee full moon

The reasonably common phenomenon of full Moon coinciding perigee was completely ignored until the media discovered the term 'supermoon' a few years ago, Perigee (minimum distance from Earth) varies between 356400 and 370400 km (average 362600 km) and apogee (maximum distance from Earth) varies between 404000 and 406700 km(average 405400 km), so on average a perigee full Moon will appear 12 percent larger and 25 percent brighter than one occurring at apogee.

However, perigee on 14 November will be the closest one since 1948, and the Moon will appear 14 percent bigger and 30 percent brighter compared with the smallest apogee full Moon. This still isn't an enormous difference, and prior to the current frenzy over 'supermoons' was only of interest to astronomers. Here in Britain, of course, we are in any case set to see absolutely nothing.

Full Moon

Taken on 22:00 on 19 July 2016 with Canon Power Shot SX530HS - 1/160 sec at f/8 ISO 100.

Waxing gibbous Moon

19 April 2016 at 19:16 shot with Canon Power Shot SX530 HS 1/800 sec at f/8 ISO 200.

Half Moon

Taken on 15 Feb 2016 at 17:26 with Canon Power Shot SX530HS 1/320th sec at f/6.5 ISO 500.

One giant leap for mankind: now for Mars

Forty years ago today, on 20 July 1969, Neil Armstrong and Buzz Aldrin became the first men to land on the Moon.

In Houston, the time was 15:17:40 CDT; in the UK 21:17:40 BST. Even aged 14, watching with my family, I was aware of how historic the moment was. I was an avid space enthusiast, my interest (like I suspect many boys of my age) having been sparked by Gerry Anderson’s TV shows such as Fireball XL5 and Thunderbirds. With us that evening was my grandfather, Robert “Pop” Mitchell, who was born in October 1892. He had just turned 11 when the Wright Brothers first flew at Kitty Hawk in 1903, a few years younger than I was in 1969. He was 19 when the Titanic sank and in his early 20s when he fought in the trenches of World War I, where he was seriously wounded in action.

As we now know, the mission came close to failure as the Eagle’s primitive computer, already overloaded, began to take the LM down towards an area strewn with boulders. Neil Armstrong was forced to take control and brought the spacecraft down safely with just 25 seconds of fuel remaining. But to those watching on TV and listening to the dialogue between Armstrong, Aldrin and CAPCOM Charlie Duke (who later went to the Moon himself), there was little hint of trouble:

Mission
Elapsed
Time
102:44:24 Aldrin: 200 feet, 4 1/2 down.

102:44:26 Aldrin: 5 1/2 down.

102:44:31 Aldrin: 160 feet, 6 1/2 down.

102:44:33 Aldrin: 5 1/2 down, 9 forward. You're looking good.

102:44:40 Aldrin: 120 feet.

102:44:45 Aldrin: 100 feet, 3 1/2 down, 9 forward. Five percent. Quantity light.

102:44:54 Aldrin: Okay. 75 feet. And it's looking good. Down a half, 6 forward.

102:45:02 Duke: 60 seconds [at this point Eagle is down to her last 60 seconds of fuel].

102:45:04 Aldrin: Light's on.

102:45:08 Aldrin: 60 feet, down 2 1/2. 2 forward. 2 forward.

102:45:17 Aldrin: 40 feet, down 2 1/2. Picking up some dust.

102:45:21 Aldrin: 30 feet, 2 1/2 down.

102:45:25 Aldrin: 4 forward. 4 forward. Drifting to the right a little. 20 feet, down a half.

102:45:31 Duke: 30 seconds [of fuel remaining].

102:45:32 Aldrin: Drifting forward just a little bit; that's good.

102:45:40 Aldrin: Contact Light [these were actually the first words spoken from the Moon, not as is commonly thought, Armstrong’s famous change of call sign to “Tranquillity Base”].

102:45:43 Armstrong: Shutdown.

102:45:44 Aldrin: Okay. Engine Stop.

102:45:45 Aldrin: ACA out of Detent.

102:45:46 Armstrong: Out of Detent. Auto.

102:45:47 Aldrin: Mode Control, both Auto. Descent engine command override, off. Engine arm, off. 413 is in.

102:45:57 Duke: We copy you down, Eagle.

102:45:58 Armstrong: Houston, Tranquillity Base here. The Eagle has landed.

102:46:06 Duke: Roger, Tranquillity. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot.

102:46:16 Aldrin: Thank you.

The Moon walk wasn’t actually scheduled until around 07:00 BST next day, with NASA having scheduled a sleep period first, but Armstrong and Aldrin were understandably anxious to get on with the job and having just landed on the Moon I’d imagine sleep was the last thing on their minds. So shortly before four o’clock I dragged my brother (a few days short of his ninth birthday) out of bed and together we watched as Neil Armstrong became the first man to walk on the surface of the Moon and fluff his lines at the same time:

109:23:38 Armstrong: I'm at the foot of the ladder. The LM footpads are only depressed in the surface about 1 or 2 inches, although the surface appears to be very, very fine grained, as you get close to it. It's almost like a powder. Ground mass is very fine.

109:24:13 Armstrong: I'm going to step off the LM now.

109:24:48 Armstrong: That's one small step for [a] man; one giant leap for mankind.

About 20 minutes later, Aldrin joined Armstrong on the lunar surface:
109:43:08 Aldrin: That's a good step.
109:43:10 Armstrong: Yeah. About a 3-footer.
109:43:16 Aldrin: Beautiful view!
109:43:18 Armstrong: Isn't that something! Magnificent sight out here.
109:43:24 Aldrin: Magnificent desolation.

That first lunar EVA lasted just over 2½ hours. In addition to collecting contingency, bulk and documented lunar samples, Armstrong and Aldrin deployed a seismometer to detect moon quakes and a retro-reflector array to reflect laser beams back to Earth and so determine the Earth-Moon distance very accurately. Also left behind was a US flag; an Apollo 1 mission patch commemorating Ed White, Gus Grissom and Roger Chaffee; Soviet medals commemorating Yuri Gagarin and Soyuz 1 cosmonaut Vladimir Komarov; a gold olive branch; and a plaque mounted on the LM Descent Stage ladder bearing drawings of Earth’s Western and Eastern Hemispheres with an inscription reading “Here Men From The Planet Earth First Set Foot Upon the Moon, July 1969 A.D. We Came in Peace For All Mankind” together with signatures of the Apollo XI crew and President Nixon.

Finally there was a silicon disk containing goodwill statements by US Presidents Eisenhower, Kennedy, Johnson and Nixon and 73 other world leaders and heads of state. The latter detail makes interesting reading. The signatories include such notorious dictators as Nicolae Ceausescu, Ferdinand Marcos, the Shah of Iran, Chiang Kai-Shek, Park Chung-hee and Anastasio Somoza. Others perhaps more positively remembered include Queen Juliana, Archbishop Makarios, Indira Gandhi and Eamon de Valera. The only signatory still remaining in office is HM Queen Elizabeth II. France is conspicuous by its absence; so is the USSR and indeed all but a handful of communist countries; China was represented by the Republic of China in Taiwan.

For months afterwards the story was doing the rounds that the Chinese people had still not been told about the landing and in those pre-internet times it might have been true. By contrast, Soviet television gave extensive coverage to the event.

Before beginning preparations for blasting off from the Moon, Armstrong and Aldrin took their sleep period and, following their example, my brother and I went back to bed. By the time I woke my father was waking my grandfather and telling him about the moonwalk. Six months after the landing, my grandfather passed away, aged 77. His life thus spanned the entire history of human powered flight, from Kitty Hawk to the Sea of Tranquillity.

On 24 July 1969, Apollo XI returned to Earth safely and, after three weeks in quarantine, its crew emerged to a heroes’ reception. But astonishingly, the public almost immediately lost interest. Six more manned missions were sent to the Moon, but only the incredible drama of Apollo XIII made the headlines (and, a quarter of a century later, an excellent if not entirely accurate Hollywood movie). Since December 1972, not a single manned spacecraft has left Earth’s orbit.

In 2002, a moon landing hoax conspiracy theorist confronted Buzz Aldrin outside a Beverly Hills hotel and called him "a coward, a liar, and a thief." Aldrin – then aged 72 - punched him in the face. Beverly Hills police and the city's prosecutor refused to file charges.

It is a fact that thanks to unmanned space probes, we now have better maps of the surface of Mars than we do of the Moon; though NASA’s Lunar Reconnaissance Orbiter will redress the balance. Already it has returned images of abandoned Apollo hardware, unseen through all these years. The photographs from the Apollo XIV site are particularly good and show footprints left by Alan Shepard and Edgar Mitchell on the Moon’s surface; finally burying for good the ridiculous conspiracy theory that the Moon landings were faked.

As a boy, my grandfather could hardly have expected to see men land on the Moon in his lifetime, but I never doubted I’d live to see a Mars landing, assuming then that it would happen in the 1980s. If the will had been there, it would have done, but NASA was sidetracked by the space shuttle for decades before returning to the original Apollo concept in an updated form, Project Orion. Very tentatively NASA is now talking about an expedition to Mars in 2037. I’ll be 82 that year – I might just make it.

© Christopher Seddon 2009

Moonwatch

In 1965, as the space race between the United States and the Soviet Union was hotting up, officials at NASA realised that they did not have “space rated” wristwatch that could be used for the upcoming Project Gemini. Given that the program was slated to include an EVA or space walk, there was an obvious need for a watch that could withstand exposure to vacuum and other rigours of spaceflight. In addition to being able to keep good time under such conditions, the watch would have to incorporate a chronograph or stop-watch function, so astronauts could see at a glance how long they had spent outside their spacecraft and to help carry out other tasks that required accurate timing.

Rather than go through the time consuming procedure of inviting bids for a “space watch”, NASA decided to send a couple of engineers to out to downtown Houston with instructions to procure a variety of off-the-shelf chronographs for testing. The tests included exposure to extreme temperatures, vacuum, intense humidity, shock, acceleration, pressure and vibration. At the end of the tests, NASA had a clear winner as the watch most suitable for spaceflight: the Omega Speedmaster.

The Speedmaster was first introduced by in 1957 and utilised the Lemania 2310 (AKA Omega 321) manual-wind movement. It is often stated that NASA specified a manual-wind movement because they thought automatic (“self-winding”) movements would not function in zero-gravity conditions, but this is incorrect on two counts. Firstly an automatic works by inertia and is not dependent on gravity; secondly the simple reason NASA selected a manual-wind chronograph is that at the time that was the only type available. The first automatic chronograph movement – the Zenith el Primero – did not come into use until near the end of the decade. However it is likely that in the cramped conditions of a Gemini or Apollo spacecraft, there would be insufficient activity to keep an automatic fully wound and a manual-wind would be more suitable.

On 3 June 1965, Gemini 4 pilot Edward White became the first US astronaut to make a spacewalk. He was wearing an Omega Speedmaster, strapped to the outside of his spacesuit with a Velcro strap. Curiously it was not until almost a year later that Omega finally learned the use to which NASA had been putting their watches. As might be expected, they wasted little time in cashing in and photographs of White’s spacewalk were soon featuring in their advertising literature. The watch itself was renamed the Speedmaster Professional, but its finest hour was yet to come.

Early on the morning of 21 July 1969, Buzz Aldrin stepped out onto the surface of the Moon wearing a Speedmaster Professional, which thus became the first watch to be worn on the Moon. Earlier, Neil Armstrong had had to leave his own watch in the Eagle lunar module after the lander’s onboard chronometer developed a malfunction. Sadly this historic watch was later stolen while on loan to the Smithsonian and has never been recovered.

In April the following year a Speedmaster Professional was used to time a crucial engine burn aboard the crippled Apollo XIII during the desperate and ultimately successful endeavour to return the spacecraft safely to Earth.

Meanwhile feeling was growing that an American watch should be used on NASA moon missions and the US-owned Bulova company lobbied the White House for their watches to be used instead of the “Speedy Pro”. Eventually NASA was persuaded to test a fresh batch of watches, including a specially-manufactured Bulova chronograph, but the Omega again came out on top with the Bulova stopping several times during testing.

By now, not only NASA was equipping its astronauts with the Speedmaster Professional. In 1975, when an Apollo spacecraft rendezvoused with a Soviet Soyuz in Earth orbit, both crews were wearing what had by now become known as the Moonwatch.

In 1978 NASA held a fresh series of tests ahead of the Space Shuttle program. Once again the Speedmaster Professional triumphed. The watch had by now received an updated movement, the Lemania 1873 (AKA Omega 861), which featured a shuttle/cam system rather than a column-wheel. The former design is simpler and thus is cheaper to both manufacture and service, but it yields nothing in terms of performance and reliability. The 1873 is again a manual-wind movement.

Externally however the Speedmaster Professional has changed very little in over half a century, even retaining its old-fashioned Hessalite (plexiglass) crystal in preference to a modern scratch-resistant sapphire crystal. This has been at the request of NASA. Plexiglass scratches quite easily, but it is virtually indestructible. By contrast, a sharp blow can shatter a sapphire crystal. Having sapphire fragments floating about inside the zero-g environment of a spacecraft is obviously not a good idea! A sapphire version, also featuring a sapphire display back, is available at extra cost but many enthusiasts prefer the Hessalite model, which is the only flight-qualified version.

The Speedy Pro is certainly not the only watch to go into space (and was probably not even the only watch worn on the Moon – contra Omega’s website), but even now it is the only watch permitted to be used for EVAs from the International Space Station or from the Space Shuttle. The Casio G-Shock – a watch almost as iconic as the Speedy – is routinely worn aboard the ISS, but because their batteries may explode in a vacuum, they cannot be used for spacewalking.

Who knows, the Omega Speedmaster Professional may even eventually become known as the Marswatch.

© Christopher Seddon 2009

The End is Nigh!

The Day the Earth Caught Fire (1961) & Crack in the World (1965)

During the 1960s, the Bomb, as it was simply known, held very much the same place in public consciousness as global warming does today. The fear of nuclear war was very real and even though the Cuban Missile Crisis had shown that the US and USSR could pull back from the brink, there remained the possibility that a nuclear war could be started by accident. Hollywood’s output reflected this fear with Stanley Kubrick’s black comedy Dr. Strangelove and the documentary-styled Failsafe, both released in 1964.

The possibility that mankind might be placed in peril simply by the testing of nuclear weapons or indeed by an attempt to make benign use of them was less prominent in the public imagination; nevertheless this sub-genre gave rise to two excellent “doomsday” movies: the British-made The Day the Earth Caught Fire (1961) and the US-made Crack in the World (1965).

The Day the Earth Caught Fire is an offbeat but smart piece of movie-making. It was directed and produced by the late Val Guest, who also directed the first two screen-adaptations of the Quatermass series. Screenplay was also by Guest, in conjunction with Wolf Mankowitz. The film starred Janet Monroe, Leo McKern and Edward Judd, and featured former Daily Express editor Arthur Christansen playing himself. It was filmed in black and white, with some orange-tinted sequences.

The tinted opening of the movie shows journalist and reformed alcoholic Peter Stenning (Judd) making his way down a deserted, heat-baked Fleet Street to the Daily Express building, to cover what may well be the last news story ever. Four nuclear devices, the most powerful yet devised, have just been detonated in an attempt to push the Earth back into its proper orbit. It is too early yet to tell if the attempt has been successful.

Reverting to conventional b/w, the main section of the movie then tells the story of the events of the previous 90 days, beginning with near-simultaneous bomb tests by the United States and the Soviet Union. In the days that follow, earthquakes and freak weather conditions occur in many parts of the world, and a total eclipse of the sun is seen in London ten days before it was due. Soon after, the whole world begins to experience heat-wave conditions. London experiences thick fog, followed by violent storms.

These events are seen through the eyes of Stenning and fellow journalist Bill Maguire (McKern). Stenning’s relationships with his ex-wife (who left him for another man), his son and new love Jeannie Craig (Monroe) are skilfully worked into the story, forming an integral part of the narrative drive. Encouraged by Editor Arthur Christiansen (himself), Stenning and Maguire, with assistance from Craig, eventually expose a government cover-up. The bombs have caused an eleven-degree shift in the tilt of the Earth’s axis. The Prime Minister goes on the air to reassure the public that the Earth’s axial tilt has altered in the past without catastrophic effects, and that things will eventually settle down.

But temperatures continue to rise inexorably. Water rationing is brought in and the Thames dries up. Eventually Christiansen learns from a Russian correspondent that that the bomb tests have also affected the Earth’s orbit, and it is moving towards the Sun. With doomsday just four months away, the Prime Minister goes on the air again to inform the public that the heads of governments world-wide have decided that the only hope for mankind is to detonate four very large nuclear bombs, in order to reverse the motion towards the Sun. Meanwhile, law and order is breaking down. People are coming down with typhoid from contaminated bootleg water and bottles of Coca Cola are fetching four pounds (about £80 at today’s prices). A street party held the night before the corrective bombs are detonated gets out of hand and rioting breaks out.

The countdown is broadcast to an anxiously-waiting world by radio, by loudspeakers set up in the streets of cities around the world, and by producer-gas fuelled police cars on the streets of London. Stenning, Maguire and Craig follow events from the Old Bell, Fleet Street [a pub in which I have spent many hours!] and the bombs are detonated, through the only immediate effect is a that cloud of dust is shaken up. Stenning begs Maguire to let him cover the story.

The story returns to the tinted “frame” that began the film. Stenning dictates his copy, his typewriter having seized up. A camera pans between two versions of tomorrow’s front page, ready to go to press. One reads “World Saved”, the other “World Doomed”. Several shots show clocks, both inside and outside the building, each showing a later time than the last, suggesting the passage of time. Church bells ring out across the City of London, implying that the Earth was saved.

It has been suggested that the church bells were added at the insistence of the distributer, and Guest intended a completely open ending. In a director’s commentary to the DVD edition, he does not mention the ending. Val Guest died in 2006, aged 94.

The Day the Earth Caught Fire is the definitive “cult movie”, a term that should be reserved for movies that punch above their weight, while delivering what they set out to deliver. This film does just that: in addition to the intelligent screenplay, the special effects belie the small budget, especially the scenes where Thames dries up. Londoners will particularly appreciate the location filming around the capital.

The film is not without some “bad science”, however. Nuclear bombs could not possibly affect the Earth’s orbit. A major meteorite impact, such as the one that wiped out the dinosaurs, would be many times more powerful than the world’s combined nuclear arsenals, but it would have a negligible effect on the orbit. Indeed, anything powerful enough to affect the Earth’s orbit to the extent implied by the film would almost certainly destroy the planet at the outset.

A solar eclipse can only take place at New Moon and one occurring ten days early would not happen without warning, as it would be apparent for days in advance that something was seriously wrong with the Moon’s phases. Four days before the eclipse, the Moon would have been seen as a waning crescent when it should still have been full. This would be noticed by astronomers and indeed any casual observer in possession of a diary or calendar. The anomaly would certainly have been picked up at a newspaper, where the current phase of the Moon is often published with sunrise and sunset times.

A eleven degree alteration of the Earth's axial tilt would significantly alter sunrise and sunset times around the world, and postions of constellations in the night sky. Again, this would be widely noticed almost immediately.

Made four years later, Crack in the World is a more orthodox SF/disaster movie. It starred Dana Andrews, Janette Scott, Keiron Moore and Alexander Knox. The screenplay was by John Manchip White and Julian Zimet. The film was shot on location in Spain and its memorable score was composed by Johnny Douglas.

Project Inner Space is an international effort to tap geothermal energy by drilling down to the Earth’s mantle, but attempts are being frustrated by a layer of dense material lying at the boundary between it and the crust above. The project’s director, cancer sufferer Dr. Stephen Sorenson (Andrews) wants to use an atomic bomb to blast through the obstruction, and a government team headed by Sir Charles Eggerston (Knox) travels to the Project’s site, a massive complex two miles underground, to consider Sorenson’s plan. This is supported by nearly all the Project’s scientists, including Sorenson’s wife Dr. Maggie Sorenson (Scott). The one dissenter is Maggie’s former lover Dr. Ted Rampion (Moore), who has developed a “Rampion Theory” that the Earth’s crust has already been seriously weakened by underground nuclear testing, and that Sorenson’s plan would trigger a global catastrophe.

Despite Rampion’s objections, the attempt goes ahead but shortly before it does Sorenson learns that his illness is terminal. However he bravely keeps this knowledge to himself. The bomb does blast through the obstruction, and magma bubbles to the surface. All appears to be well, and Rampion happily concedes that he was wrong.

However a series of earthquakes begin to occur along a (fictitious) geological flaw in the Earth’s crust known as the Macedo Fault. Many of the places affected have no history of seismic disturbance. Rampion and his assistant Steele take a DSV to investigate an underwater portion of the fault and determines that a spreading crack has opened up in the Earth’s crust. If a way of stopping the rupture isn’t found, the Earth will be torn apart.

Sorenson and Rampion put aside their differences and try to come up with a solution. They decide the best hope of averting disaster is to explode a hydrogen bomb in the shaft of an active volcano that lies in the path of the spreading crack. Rampion and Steele volunteer for the difficult assignment of lowering the bomb into the volcanic shaft.

The bomb is successfully placed, though Steele falls to his death in the volcano’s magma chamber, and Rampion is almost barbecued alive. Believing him to be dead, Maggie Sorenson is distraught. Still unaware how seriously ill her husband is, her affections are drifting back to Rampion. However, the latter is only unconscious and rapidly recovers. The bomb goes off and the earthquakes appear to cease.

Relief is short-lived. Soon reports come in that suggest that the crack has simply switched direction, and appears to be doubling back on itself. To make matters worse, it is now moving twice as fast. As Rampion speaks to Sorenson by R/T, the latter collapses - it is finally apparent that he seriously ill. The group returns to the Project, where Maggie learns her husband has just days to live. Despite her renewed feelings for Rampion, she is grief-stricken. However she accompanies Rampion in a jeep on a trip to investigate a second crack that has appeared near the Project complex [where exactly this is located is never revealed]. Meanwhile, Sorenson determines that the two cracks will meet at the original borehole, and that a portion of the Earth will be blasted away into space to form a new moon.

On the surface, Rampion and Maggie Sorenson desperately try to stop a train that is heading straight towards the crack, but the jeep goes into a ditch. The train fails to stop and a bridge it is travelling over collapses. There are no survivors.

After freeing the jeep, the pair return to the Project, which is being evacuated. There is a dramatic shot of two converging cracks. Nobody has seen Sorenson, so Rampion and Maggie take the elevator down into the by-now quake-torn complex to look for him. They find him preparing to record the birth of Earth’s new moon. He points out that the Project is located outside the area that will be blasted into space, locks himself in and refuses to leave. Rampion and Maggie Sorenson head back to the surface, but the elevator becomes jammed by a quake. They manage to climb to the surface and reach safety just as the two cracks meet. A colossal explosion blasts the new moon into space, at the same time acting as a safety valve to prevent any further earthquakes. Calm returns and the old Moon and its new sibling are seen in the sky together for the first time.

The science in Crack in the World is well thought out, but became dated soon after the film’s release as the theory of plate tectonics became widely accepted. There are in fact many “cracks in the world”, corresponding to the tectonic plates that slide over each other to cause continental drift.

The theory that the Moon was spun off from the Earth was first put forward by Sir George Darwin (son of Charles) in the 19th Century and was strongly supported by the American astronomer William Pickering, who suggested that the Atlantic basin had been formed as a result. However the angular momentum of a system so formed would not correspond to that of the actual Earth-Moon system, so the theory had to be abandoned.

Dated though the science is, it is certainly on another level to the ludicrous Core (2003).

For some reason, Crack in the World has never been released on DVD. It is strongly to be hoped that this omission will be rectified in the near future.

In recent years, there has been a trend for remaking classic movies of the 1950s and 1960s, such as the 2005 version of The War of the Worlds. The Day the Earth Caught Fire and Crack in the World would both be excellent candidates for a remake. Although both films are rooted in ‘Sixties fears about the Bomb, they additionally tap into two highly-topical themes – climate change and emission-free energy.

© Christopher Seddon 2008

The Moon in Daytime

Although the Moon is generally associated with night time, it actually spends as much time above the horizon in day time. These shots show the Moon in various phases in late afternoon or early evening, at various times of the year.























© Christopher Seddon 2008

Everything you wanted to know about the Moon

Most people will think nothing of the Moon should they happen to see it in the sky. This is hardly surprising, the Moon is after all one of only two distinct, instantly recognisable objects (the other being the Sun) that we are guaranteed to see (even here in Britain!) during our lifetime; there can be nobody alive who has not known of it from their earliest childhood. The Moon is a ubiquitous part of our culture and almost certainly has been since earliest times. Its beauty in the night skies has inspired writers, poets and artists for centuries. Reaching for the Moon was once synonymous with desiring the impossible - until man reached it. Even now, almost four decades on from Armstrong's momentous giant leap for mankind, the Moon remains the only astronomical body other than Earth to be visited by humans.

What’s in a name?

Many people think the “official” name of the moon is the Latin form Luna, but in common with Terra (Earth) and Sol (the Sun) the term Luna has no official standing and is rarely encountered outside of science-fiction novels, though the adjectival forms “lunar”, “terrestrial” and “solar” are in common usage. The “official” name for the Moon is – the Moon (capitalised)! The uncapitalised form – “moon” – is a generic term for any natural satellite of any planet, including our own. Some prefer this term over “satellite” thinking the latter implies something manmade. Strictly speaking a manmade satellite should be referred to as an “artificial satellite” but this usage is now very rare.

The phases of the Moon

The most obvious thing about the Moon is that its appearance changes from night to night. The Moon is not the only body visible from Earth to exhibit phases – Venus and Mercury do also – but without a telescope those of Venus are very difficult to see and those of Mercury are way beyond human perception. The explanation for the phase is straightforward; only one hemisphere of the Moon is illuminated by the Sun at any one time (in common with all other non-luminous solar system objects) and the portion of the illuminated hemisphere visible from Earth changes as the Moon travels round the Earth on its orbit. When the Moon and Sun are on opposite sides of the Earth a full moon is seen; when they are on the same side the Moon disappears altogether. When they are 90 degrees apart a half moon is seen.

The time taken for the Moon to cycle through its phases (the synodic month, defined as the time taken for the Moon to return to the same position relative to both Earth and Sun) is actually longer than the time taken for it to complete a single orbit (the sidereal month) – 29.53 days on average, as opposed to 27.32 days. The reason for this is while the Moon is completing an orbit of the Earth, the latter is moving on its own orbit around the Sun, and the Moon has to move slightly further before it can return to the same position relative to both Earth and Sun.

The wrong time of the month

In 1972 the American researcher Alexander Marshack claimed that people were making records of the phases of the Moon 30,000 years ago. After extensive research that entailed examining just about every prehistoric artefact he could lay his hands on for calendrical notches, he published his findings in a book entitled The Roots of Civilization. Marshack claimed that the tallies corresponded to lunar months. On the face of it, this seems highly plausible. It is now generally accepted that the people of that era were every bit as mentally capable as we are today, and there is little doubt that they would have been aware that the phase of the Moon changes from night to night in a predictable manner. But there are two problems – firstly, it seems unnecessary to record, say, the days since the last full moon when one can simply look at the Moon, note the current phase, and work forward to when the next full moon will occur. The second problem is the tallies vary in numbers of days by more than can be explained by the small seasonal variations in the length of the lunar cycle, or by observational error. However there is another cycle with an average length almost identical to the lunar cycle that does show a certain amount of variation – the human menstrual cycle. It is my guess that this is what was being recorded, since the advantages of knowing when that time of the month is approaching are fairly obvious, and this was probably also the case 30,000 years ago!

That the menstrual cycle is almost exactly one lunar month in duration is now thought to be pure co-incidence, but it is one that was noticed many thousand years ago. The words “moon”, “month”, “menstruate” and “measure” (time) all have the same Proto-Indo-European root. The proto-Indo-European language is the hypothetical common ancestor of the Indo-European languages, which include Latin, Greek, Sanskrit and the modern languages derived from them. According to one popular theory, the Proto-Indo-Europeans were warlike nomads who originally expanded from the Eurasian steppes at around 4000 BC, taking their language with them. A rival theory, proposed in the mid-1980s, claims that Proto-Indo-European origins go even further back, and that they were originally farmers living in Asia Minor, shortly after the end of the last Ice Age. Regardless of which theory is correct (I personally favour the farming theory), the origin of the word “moon” is very ancient indeed.

The Moon from an astronomical viewpoint

The Moon is ranked as a satellite of the Earth. Most of us will be aware that the Earth is in astronomical terms quite undistinguished, and that the same goes for the Sun. Even though the Milky Way, of which the Sun is a part, is classed as a large galaxy one doesn’t have to look far (in fact a mere two million light years) to find a larger galaxy (the Andromeda Galaxy). In a way this is exactly what we should expect from the Copernican Principle or Principle of Mediocrity, an important principle in the philosophy of science which states that Earth holds no special place in the universe and that humans are not privileged observers. Right, so this presumably means that the Moon is equally average? Well, actually, no.

The Moon is a remarkable object and as far as the Solar System is concerned, it is unique. The Moon is a fully paid-up member of the Solar System's "Big Seven" group of satellites, all of which are larger than Pluto and Eris (the two smallest planets(or largest “dwarf planets” if you insist)). The Moon is by no means the largest member of this group, but all the other six are satellites of giant planets: the Earth is at best only medium-sized. Indeed many astronomers take the view that the Moon is too large in relation to the Earth to be considered a mere satellite and elevate it to the rank of a sister world, classifying the Earth-Moon system as a binary planet. However this view is not really valid. Large though the Moon is, it is still only 1/81 the mass of the Earth; the centre of mass for the Earth/Moon system lies below the surface of the Earth and the Moon cannot be classed as anything other than a satellite of Earth.

Lunar geography – or Selenography

Though most will know what it means, terms like “lunar geography” , “lunar geology”, etc, are oxymorons as the prefix “geo-“ means pertaining to the Earth. The correct terms are “selenography”, “selenology”, etc; the prefix “seleno-“comes from Selene, the Greek goddess of the Moon.

It is not true, as is often believed, that Galileo was the first to map the Moon using a telescope. That distinction must go to Thomas Harriot in 1609, a year before Galileo. However, both men clearly observed mountains, valleys, craters and comparatively smooth areas known as maria or seas. It was at one time believed that these latter features actually were seas, or at least dried-up sea beds, but we now know from samples brought back from the Moon that they have never contained any water.

However, in 1998, it was widely reported that NASA's Lunar Prospector probe had found water on the Moon, allegedly from comets that had landed in polar regions permanently hidden from the Sun and thus remained frozen. In fact, the probe had only detected evidence of hydrogen on the Moon's surface. While this could be due to water, I have to say I am highly dubious. Any comet impacting the Moon would almost certainly do so at a relative velocity high enough to vaporise it instantly as its kinetic energy is transformed into heat.

Another theory, popular before the Space Age, was that the maria were great dust-bowls, and any spacecraft landing there would be swallowed up. The idea was featured in two vintage novels by Sir Arthur C. Clarke, Earthlight and A Fall of Moondust, the latter telling the story of a "dust cruiser" designed to "sail" the lunar "seas".

Today we know that the maria are large dark plains of basalt, formed by volcanic activity billions of years ago.

The origin of the lunar craters has been the subject of considerable controversy over the years. It was once believed that they were volcanic in origin, similar to calderas, but it is now generally accepted that they are the result of meteoric impacts. It was however quite a long time before the volcanic theory was abandoned and a number of astronomers, including Sir Patrick Moore, continued to argue for it until as late as the 1990s.

A Canterbury Tale

Assuming that the impact theory is correct could any new craters have appeared in historic times? In theory, there is no reason why not, though in practice it seems unlikely with impacts forming craters visible from Earth being fairly rare events. However in the 1970s an American astronomer named Jack Hartung claimed that a report made on 18 June 1178 by a Canterbury monk named Gervase could be interpreted as an eye-witness account of the formation of the crater Giordano Bruno.

... after sunset when the moon had first become visible a marvellous phenomenon was witnessed by some five or more men who were sitting there facing the moon. Now there was a bright new moon, and as usual in that phase its horns were tilted toward the east; and suddenly the upper horn split in two. From the midpoint of this division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals, and sparks. Meanwhile the body of the moon which was below writhed, as it were, in anxiety, and, to put it in the words of those who reported it to me and saw it with their own eyes, the moon throbbed like a wounded snake. Afterwards, it returned to its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal. Then after these transformations the moon from horn to horn, that is along its whole length, took on a blackish appearance.

It has been suggested that Gervaise saw a meteorite impact, and that the crater Giordano Bruno (named for the Italian philosopher who was burned at the stake for heresy in 1600) was formed as a result. Proponents of this idea point out that the time of the year is consistent with an impact from the so-called Taurid Complex, associated with Enke's Comet, but the whole thing really has to be taken with a king-sized pinch of salt. Surely a small group of men in Canterbury would not have been the only people in the whole world to see and note such a major disturbance in the natural order of things? A more recent mathematical treatment of the theory showed that Earth would have been bombarded with ejecta from the impact. This would have resulted in spectacular meteor showers of roughly 50,000 meteors an hour being visible all over the world for a week – yet there is absolutely no record of anything of the sort being seen.

Crucially, the Moon was close to the horizon at the time and what Gervaise reported was almost certainly an unusual cloud phenomenon or atmospheric disturbance.

The Moon in fiction

What is arguably the world’s first ever work of science-fiction, entitled A True Story, was written by the Greek satirist Lucian of Samosata in the 2nd Century A.D. and dealt with imaginary voyages to the Moon, but the topic did not become popular until the invention of the telescope in the 17th Century. Authors who wrote about journeys to the Moon included Johannes Kepler, Francis Godwin and Cyrano de Bergerac though the heroes tended to travel by unlikely means such as harnessing a flock of geese.

About a hundred years before Project Apollo, Jules Verne described an American moon program in which a projectile is launched from a space gun in Florida and splashes down in the Pacific, just as Apollo would later do. Some 35 years later, H.G. Wells sent his characters to the Moon in a vehicle utilising anti-gravity – much to the disgust of the by then elderly Verne. This criticism evidently affected Wells, who much later used a space gun himself in the moon shot sequence at the end of the movie Things to Come.

The Moon featured in innumerable works by the 20th Century’s “Holy Trinity” of Sir Arthur C. Clarke, Isaac Asimov and Robert Heinlein.

Inevitably the Moon has featured in many science fiction movies and television series, with manned moonbases being a popular theme for the latter. Gerry Anderson, best known for his classic puppet shows such as Thunderbirds, made two live-action series featuring moonbases. In the first, UFO, interceptors were launched from a moonbase to destroy hostile alien spacecraft. The second, Space 1999, was an altogether more ambitious affair. It was billed as a British answer to Star Trek but despite a huge budget, excellent special effects and a star cast that included Martin Landau, Barbara Baines, Barry Morse, Catherine Schell, Joan Collins, Brian Blessed and Judy Geeson, the series was not a success and was cancelled mid-way through its second run. The main problem was an utterly implausible plot device in which a nuclear explosion sent the Moon careering off into outer space at what one must presume was many times the speed of light (a physical impossibility in itself), given that most weeks would find it hurtling towards a new planetary system. Hopes would rise among those marooned on Moonbase Alpha that the new system would contain an inhabitable world on which they could settle, but on the occasions that it did something would always prevent colonisation, be it paranoid aliens fearing cultural contamination by “primitive” humans (this one cropped up on several occasions); an interplanetary battle of the sexes (a group of rather butch-looking women hijacked Alpha and used it as a platform to lob nuclear missiles at the men, who had already been banished to another planet for being “unreasonable”); a time-warp that reverted the crew to cavemen (this provided an excuse to put the lovely Zienia Merton in a leopard-skin), or the putative new home turning out to be rather inconveniently composed of antimatter. Even when the Moon was in interstellar space things were rarely quiet: black holes and time warps were as frequent as tailbacks on the M25; other menaces included a space brain, a monster dwelling in a Sargasso Sea of abandoned spaceships and miscellaneous aliens in suspended animation, who invariably turned out to be bad guys sent into exile by their peace-loving compatriots.

Is the Moon Earth’s only natural satellite?

Could the Earth have a second, undetected satellite? On the face of it, there is absolutely no reason why not. Jupiter is now known to have at least 63 satellites; Saturn has about the same number; and even Pluto has three. However if a second Earth satellite were to exist, it would have to be very small indeed to avoid detection. It is not often appreciated that were the Moon only two miles in diameter, it would still be visible to the naked eye.

Nevertheless, the idea that the Moon might not be our planet's sole attendant has intrigued astronomers for the better part of two hundred years. In 1846 Frederic Petit, Director of the Toulouse Observatory, claimed that a second Earth satellite had indeed been discovered. Petit's claim was soon refuted, but he became obsessed with the idea of a second satellite. Fifteen years later, he published an abstract in which he proposed the existence of a second satellite to account for then-unexplained anomalies in the Moon's orbit. The theory attracted little interest among astronomers, and doubtless would have been entirely forgotten by now had a young French writer by the name of Jules Verne not read the abstract and immortalised Petit and his satellite in the novel From the Earth to the Moon, in which the Petit object passes close to the space travellers projectile, pulling it off course and swinging it into an orbit around the Moon.

The idea of a second moon was revived several times during the last century, and shortly after the end of the Second World War, Clyde Tombaugh, discoverer of Pluto, carried out a most comprehensive search. He used equipment so sensitive that it would have shown a lump of coal the size of a football a thousand miles away. He failed to find anything.

It is now believed that the combined gravitational effects of the Earth, Moon and Sun would rapidly eject any small satellite from Earth’s orbit, ruling out the existence of a second moon. Nevertheless in 2002 an object known as J002E3 was discovered in Earth orbit – but it was soon discovered to be almost certainly the discarded third-stage booster from the Apollo XII mission in November 1969. It is believed that the object left orbit in June 2003 and may return around 2032.

It is sometimes claimed that the asteroid 3753 Cruithne ranks as a second Earth satellite. Discovered in 1986, Cruithne has an unusual orbit, known as a “horse-shoe” orbit, due to the influence of Earth. However it is in orbit around the Sun, not the Earth and therefore it is not an Earth satellite.

A Cosmic Coincidence

One of the most singular features of the Moon is the fact that it appears almost exactly the same size as the Sun in the sky. The reason for this is that while the Sun is 400 times the diameter of the moon, it is also 400 times further away, so both objects appear the same size when viewed from Earth. This is a pure co-incidence, but it is responsible for what is surely one of the most spectacular phenomena to be seen anywhere in the Solar System - a total eclipse of the Sun. A solar eclipse is, of course, due to the Moon passing directly between the Sun and the Earth, casting its shadow upon the latter (strictly speaking, the phenomenon is an occultation, not an eclipse). Because the Moon's disc is just sufficient to hide that of the Sun, the latter's atmosphere, the so-called corona can be seen in all its splendour. In fact it is a close call and for a total eclipse to occur, the Moon must be close to perigee (i.e. its minimum distance from Earth). Otherwise, a thin ring of the Sun's disc is left showing, quite enough to drown out the glorious corona, and the eclipse is said to be annular. Because the Moon's orbit is inclined at five degrees, an eclipse does not occur every month, though at least two must occur in a given year. However this figure includes partial eclipses, when the Moon does not pass directly in front of the Sun. Even when a total eclipse does occur, the area experiencing totality is only a small corridor, though it may extend for thousands of miles as the Moon's shadow races across the Earth's surface.

I have only witnessed one total eclipse of the Sun, that being the one in Cornwall in August 1999. Although cloudy skies prevented me from seeing totality, it was still an awesome experience as day became night in a matter of seconds. Sea birds, believing night really had fallen, hooted in great excitement. On the horizon was seen a band of orange light, marking the limits of totality. The scene was one of great beauty and although it was disappointing to have missed something I had been waiting to see since my childhood, it was still a worthwhile experience.

We will not always be able to enjoy the spectacle of a solar eclipse, because tidal effects are causing the Moon to recede from the Earth by 3.8 centimetres per year. That might not seem like a lot, but it adds up. When the first maps of the Moon were being drawn up, three centuries ago, the Moon was 11.4 metres (just under 40 feet) closer to the Earth. When modern humans first reached Australia, 50,000 years ago, the Moon was 1900 metres (rather more than a mile) closer; when the dinosaurs became extinct 65 million years ago, it was 2470 kilometres closer.

Eventually it will be too far away for its disc to fully block out the Sun, even at perigee. These effects are also causing the Earth's spin to slow and the day is gradually lengthening. Again, these effects are small but they add up over time and account for discrepancies amounting to several hours in the timing of eclipses observed in antiquity.

The Dark Side of the Moon

As is correctly pointed out in the eponymous Pink Floyd album, there is no "dark" side of the Moon: each part of the Moon experiences as much daylight as it does night time. So where does the idea that the Moon has a “dark” side come from? In common with almost all bodies circling a larger primary, the Moon exhibits so-called "captured rotation", meaning that it turns on its axis exactly once in each circuit of its primary. In other words, a lunar day is exactly a month long. It is often said that this results in half the Moon's surface being permanently hidden from view on Earth, leading to the misconception that the hidden side is in permanent darkness. If this were true, we’d see a full moon all the month round! The phase is of course due the part of the Earth-facing side being in darkness. In fact it is not strictly true that only half of the Moon’s surface can be seen from Earth. Because the Moon (in common with all other objects in the Solar System) does not move in a perfectly circular orbit, its orbital velocity varies slightly during the course of a month in accordance with Kepler's Laws of Planetary Motion. This means that the orbital motion and axial spin are at times slightly out of step, and in consequence we can see portions of the "hidden" side. Because the Moon's orbit is inclined at five degrees to that of Earth, we can also see alternately beyond the north and south lunar poles. Finally, parallax effects result in observers being presented with slightly different portions of the Moon's surface at different times of the day and in total, about 59 percent of the Moon's surface may be observed from Earth at various times.

Origin of the Moon

As one might expect, the origin of the Moon has been the subject of many theories over the years. The first theory to gain widespread acceptance was put forward by Sir George Darwin (son of Charles). Darwin suggested that the Earth and Moon had originally formed a single rapidly rotating, molten mass. The tidal forces raised by the Sun and the centripetal forces of its own motion caused it to become pear-shaped and eventually split into two objects of unequal size. A strong supporter of the fission theory was the American astronomer W.H. Pickering, who suggested that the scar left by the Moon's breakaway was now the basin of the Pacific Ocean.
Unfortunately the theory was pear-shaped in more ways than one. A mathematical treatment of the dynamics involved showed that it was unsound and it had to be abandoned. This did not prevent it from being used as the basis of an ingenious science fiction movie, Crack in the World, in which an attempt to tap energy from the Earth's molten core goes disastrously awry and triggers a series of earthquakes. A growing rupture in the Earth's crust threatens to tear the planet apart and rival scientists Stephen Sorenson (Dana Andrews) and Ted Rampion (Kieron Moore) are forced to put aside their differences and try to come up with a solution. An attempt to avert disaster by exploding a hydrogen bomb in the shaft of an active volcano is only partially successful, and a whole portion of the Earth is blasted away into space, where it forms a new satellite. The movie's closing reel shows the Moon and its new sibling in the sky together, the whole process having been observed from no more than a few hundred yards by Rampion - accompanied, of course, by the movie's love-interest (Janette Scott).

The next theory to be put forward suggested that the Moon was originally an independent body, but it wandered too close to the Earth and was captured. There is little doubt that this has happened elsewhere in the Solar System, Mars's dwarf attendants and several satellites of the giant outer worlds, including Neptune's major satellite Triton – only slightly smaller than the Moon - were almost certainly captured from independent orbits. The theory was popular for a time and in the middle part of the last century an Austrian researcher named H.S. Bellamy even suggested that it might have happened fairly recently (needless to say, this accounts for the destruction of Atlantis). But captures that are believed to have occurred all involve objects that are very small in relation to their captors, and as we have observed, the Moon is fairly large in relation to the Earth.

Another theory states that the Moon simply formed in Earth’s orbit from the same primordial material, but this model fails to explain why the Moon is less dense and deficient in iron in comparison to Earth.

The currently popular theory, put forward by American scientists W.K. Hartmann and D.R. Davis in 1974, proposes that an object about the size of Mars collided with Earth, and while the bulk of its mass including its iron core merged with the Earth, enough debris was ejected into space from Earth's mantle to form the Moon. The theory explains why the Moon is rather less dense than the Earth, as denser materials were not blasted into space by the impact. The theory is not without its problems, but seems to be the most plausible explanation put forward to date.

From the Earth to the Moon

As we have seen, some 59 percent of the Moon’s surface can be seen under various conditions from Earth. Not until the dawn of the space age was anything definite learned about the remaining 41 percent. In October 1959, the Soviet probe Lunik III made a fly-by of the far side of the Moon. Because the probe was out of radio contact with Earth as it passed behind the Moon's far side, the pictures it took could not be simply beamed back to Earth. Accordingly, film was automatically exposed and developed. As the probe emerged from behind the Moon, the developed film was imaged by a TV camera and the first blurry images of the Moon's hidden side were transmitted back to Earth. It sounds crude, and by today's standards it was, but it was a tremendous technical feat for the time.

As the Cold War ratcheted up tensions between East and West, so the Soviets continued to score an impressive succession of “firsts” in space, but the US was galvanised into a response and on 25 May 1961 President John F. Kennedy threw down his historic challenge:

I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish.

In May 1961, Alan Shepard had only just become the first American to fly in space, yet little over nine years later after the flight of Lunik III, men saw the Moon's hidden side with their own eyes as Apollo VIII made its historic circumnavigation of the Moon at Christmas 1968. Seven months later Armstrong and Aldrin became the first men to actually land there, realising Kennedy’s goal with less than six months to spare. The technological leap that made this possible might sound incredible, but it must be remembered that even the technology of Project Apollo was quite primitive by today's standards. It is a fact that the Eagle's on-board computer was actually far less powerful than that of a modern-day mobile phone! (I refuse to comment on conspiracy theories that the Moon landings were faked because it is patently obvious that the idea is absurd.)

At all events, the US won the race to the Moon. Not until much later did it emerge that early Soviet successes owed more to the genius of Chief Designer Sergei Korolev than to any superiority of communism over capitalism. But Korolev’s health had been ruined by a spell in the gulag during Stalin’s reign of terror and he died in 1966 during a botched operation to remove a tumour. With his death ended any hopes of perfecting the N1 booster with which he had hoped to put a man on the Moon. The race to the Moon lost, the Soviets turned their attention to establishing a near-permanent human presence in Earth orbit – which in the long run was of far more benefit than simply duplicating the efforts of the US.

When will people go back to the Moon? In 1972, when Cernan and Schmitt blasted off from the Moon's surface, it was said that nobody would be going back in the 20th Century. I did not believe this (I assumed that men would be on Mars before the century was out), but the public’s attention-span is short and after the Moon landing had been made, only the astonishing drama of Apollo XIII made the headlines (and, a quarter of a century later, an excellent if not entirely accurate Hollywood movie). NASA turned its attention to the Space Shuttle, setting back the manned exploration of space by decades. As an experimental proof-of-concept spaceship, there is no doubt that the Shuttle was a technological triumph. As a practical manned reusable heavy-lift system however it has been an unmitigated disaster that cost the lives of the crews of Challenger and Columbia. It was the latter tragedy that prompted President George W. Bush, in one of the very few highlights of his presidency, to announce what has since become known as Project Constellation, which will return humans to the Moon, and on to Mars – using designs that draw heavily from Project Apollo, albeit using hardware developed originally for the Shuttle.

A permanently inhabited base on the Moon should be established no later than the middle part of this century. When it is, one of science fiction’s oldest and most central themes will be a reality at last.

© Christopher Seddon 2007