• Thu. Sep 21st, 2023

Chang’e 4 probe reaches the dark side of the moon

BySam Haynes

Feb 1, 2019

China successfully completed the world’s first landing on the far side of the Moon with Chang’e4, an unmanned space probe. It is undoubtedly a jubilant time for China’s space program but are there greater ramifications?

Unfortunately for any fanciful Pink Floyd groupie or misguided Transformers fan, the sunny landing of China’s Chang’e 4 space probe on 3 January has confirmed at least one thing already. There is no dark side of the Moon. There is, however, a side that Earth never sees. This is due to a fascinating phenomenon known as ‘tidal lock’.

Billions of years ago the Moon rotated at a faster rate, which would have allowed for observations of its surface in its entirety from Earth. Since then the Earth’s massive gravitational field has continually warped the shape of the Moon. This has caused the Moon’s rotation to reduce to its current rate, now taking about 28 days to complete a full rotation. This is the same amount of time it takes to orbit once around the Earth and the reason we see only one side.

As an aside, the Moon’s gravitational field is equally trying to deform the shape of the Earth, which is the origins of the sea’s tides and, indirectly, the temporary phenomenon we call a total solar eclipse. There are a fair few other examples of ‘tidal lock’ in the Solar System. Mercury is tidal locked to the Sun, meaning it actually does have a side in perpetual darkness. The dark side of Mercury just isn’t quite as catchy.

It is precisely because of tidal locking that Chang’e 4, the first spacecraft ever to land on the far side of the Moon, is a significant feat of engineering. Never being able to face the Earth means direct communication is impossible. Only though a stable relay system with an orbiting satellite can a landing ever hope to be successful or useful.

Marking China’s continued interest in our relatively neglected celestial partner, Chang’e is a series of planned spacecraft named after the Moon Goddess in several chinese mythologies. Its overall aim is to test technologies for an eventual manned flight and even pave the way for the creation of a lunar base. This time round, with Chang’e 4, a symphony of onboard instruments plan to conduct far-reaching experiments to excite any science buff, all with an admirable open data policy. Radio antennae to conduct novel astronomy without the overwhelming terrestrial cacophony, a self sustaining biome to explore the possibility of growing life and geological probes to uncover the history and structure of the Moon.

So, why is China interested? Geopolitically, space looks great on any superpower’s résumé. National egos tend to be terrific for propelling progress, which is fortunate for space science but historically less so for humanity. Alarmism aside, China’sBelt and Roads Initiative, South ChinaSea dispute and American trade war are indications of Xi Jinping’s shedding the China’s historically insular foreign policy. The West’s space programs are gradually submitting to private ventures selling grandiose Martian dreams. Are we seeing the celestial projection of the Chinese Government capitalising on regions overlooked by the West? Conceivably, China has decided to concede colonising Mars as the impractical farce it is in order to follow through on a significantly easier and likely more fruitful command of the future of the Moon.


Image credit: Sergio Calleja (Life is a trip) via Flickr

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