Page 76 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

INTRODUCING

THE MOON

THE MOON WAS MADE WAY BACK WHEN A LARGE CHUNK
OF CHEDDAR THE SIZE OF MARS HIT EARTH. TRUE? NO!
HOLD ON TO YOUR DOUBLE GLOUCESTER AS THIS MYTH,
AND OTHERS, ARE ABOUT TO BE DISPROVED

To state a fact: the Moon is uncomfortable with the truth. is brighter during the day than Moon is low that it’s possible to
always around somewhere in I’d suggest that maybe the at night, so the Moon is not as notice this movement the most
the sky at some time or other. wrong teacher is in charge prominent. There are lots of and, if you have time, it’s worth
It sounds obvious, but this of science. other reasons why, such as the noting where it is an hour later
concept is wrapped up in urban fact that evenings are the part – you may be surprised how far
myth and provoked a great MYTH-BUSTING of the day when we generally it has moved.
discussion among planetarium Understanding the Moon’s have more time to gaze at the A couple of other things
presenters recently. The myth orbit around Earth and the sky, whereas we’re all busy that are deserving of special
in question has two parts, both corresponding way it is lit by rushing around during the day. attention are the Moon’s colour
of which are entirely wrong: the Sun, which leads to its So, yesterday, after one such and its movement across the
fi rstly, the Moon comes out phases (see box, lower right), busy day at work I took the sky as it orbits Earth.
at night; and secondly, it’s is not easy. However, with a time as night approached to do The Moon moves at a
invisible during the day. No bit of patience it is possible to some stargazing and watched blistering Mach 3, which is
names will be mentioned here appreciate why the Moon can the full Moon rise over the three times the speed of sound
to protect the guilty, but I was be visible during the day and trees in the fi eld in front of at sea level. The stronger
told by a science teacher just does not only ‘come out’ when our house. To the naked eye, goldish-to-reddish colour of
the other day (which makes it’s dark at night. this is when the Moon is most the rising Moon, as opposed
the following even worse to The question really should magnifi cent: a low, golden- to the grey-white view when
absorb), that the myth is taught be: why don’t we notice the tinged globe slowly being it’s higher, is explained by the
in a particular primary school Moon during the day? The carried into the sky by the fact that when it’s low to the
because the pupils would be simple answer is that the sky rotating Earth. It’s when the horizon, light from the Moon

SEAS AND HIGHLANDS PHASES
An unaided, naked-eye view of the The word Moon is responsible
ALAMY X 2, STEVE MARSH, LARRY LANDOLFI/SCIENCE PHOTO LIBRARY thought these dark areas were time it took for the Moon to
full Moon reveals dark patches,
some roundish in appearance,
for our word ‘month’: one
that sit within a much brighter
mooneth (or thereabouts)
landscape. Early astronomers
was the measurement of the
great volumes of water. Even
complete one orbit of the Earth
though we know that water doesn’t
in relation to the Sun. Although
exist on the Moon, their old watery
it’s given in schools as 28
names have remained in use to
days, the Moon’s changing
this day. So, on 20 July 1969
appearance (it’s cycle of
man fi rst landed on the Moon
phases) takes just over 29.5
in Mare Tranquilitatis – the Sea
days. This is known as the
of Tranquility. My favourite wet
Synodic Month. It represents
feature name on the Moon is Palus
Putredinis – the Marsh of Decay;
to the next (or any other
features like seas and marshes by early astronomers
a splendid name!
76 skyatnightmagazine.com 2012 The dark patches on the lunar surface were thought to be watery the period from one full Moon