The Moon revered by humans for millennia is undoubtedly one of the most useful tools (for want of a better word) man-kind has been able to bring to bear on his daily life.
The following is a brief outline on my impressions of the Moon. Here’s how I see it.
The Moon revered by humans for millennia is undoubtedly one of the most useful tools (for want of a better word) man-kind has been able to bring to bear on his daily life. He has used it as a reference to regulate most everything he has done from bodily functions in ancient times (or at least keep track of them) to crop rotation etc., in more modern times.
Our group of Amateur Astronomers for instance make sure it’s not ‘up’ on viewing nights, where possible!
Days, weeks, months and therefore years are slotted in by the Moon’s 27.32 day Sidereal Period
or Sidereal Month and 29.53 Lunar or Synodic Month with some help from other factors of course. (I feel it was Julius Caesar who developed the current popular calendar). It gives us our ocean movement in two (2) High Tides every day, with the gravitational pull of the Moon on one side of the earth and the Sun to a lesser extent on the other side, causing either a ‘Pile-up’ or Pull Away’ effect on the water every 12.25hrs.
Now, I’m no scientist so I’ll leave that technical stuff to them. But, Astronomers believe (for want of a better idea) that the Moon may have been caused by a very large object (maybe, even Mar’s size) around 4 Billion years ago impacted the Earth (maybe a glancing blow) and throwing up into space huge amounts of molten material, some of which returned to Earth eventually but the remainder became the “Blanc’ for the Moon we see today. The late ‘Bombardment Period’ responsible for most of the craters and fissures in the Moon’s crust, in the first 500 million years of it’s life that filled the largest craters with lava to give that nice smooth look of the ‘Maria’ and a new place for smaller future craters in latter times the huge smooth area’s we once believed to be ‘Sea’s’ are in fact not water (there is no water on the Moon) but large lava filled plains, named in Latin as ‘Mare’ for sea, the plural being ‘Maria’. They are still very impressive when seen from earth.
Galileo Galilei changed the way we view the Moon and indeed many other things 400 years ago when he looked to the heavens in his small hand-made Telescope.
Now, I would hazard to say that the most famous of the ‘Sea’s’ is ‘Mare Tranquillitas’ or more commonly know as the ‘Sea of Tranquillity’ while the honour of the largest goes to ‘Oceanus Procellarum’ or the Ocean of storms. The size of these being respectively 870km and 2600km, whilst the other ‘Maria’ range in size from ‘Mare Spumans’ at 104km to ‘Mare Frigoris’ at 1600km and we’ll cover these in future instalments.
Our busy little ocean ‘Regulator’ has however, got itself a dark side (as viewed from Earth, anyway) one only seen by camera’s on Space Craft and a very few outrageously lucky humans (astronauts).
The Moon is tidally locked to the earth by the earth’s gravitational force. It rotates once on its axis (angle of 6.7o from vertical) in the same time as it takes to revolve around earth travelling at around 1.3km per second, hence we on earth only ever see one side of our lunar companion. Librations of the Moon give us small peeks at the edges of ‘the other side’ such as the very edge of ‘Mare Orientale’.
The Moon’s phases as seen from earth are from New Moon to Waxing Crescent – 1st Quarter to Waxing Gibbous to Full Moon then Waning Gibbous to last Quarter to Waning Crescent and once again to New Moon. One full Lunar rotation is called a ‘Lunation’ and lasts for 29.53 days. So when we look to the phases of the Moon (one at a time, of course) the round or normal side of the Moon is called the ‘Limb’ and the side being revealed by the sun’s shadow is called the ‘Terminator’. Using a good set of Moon Maps, such as those obtained from www.Astrovisuals.com.au or a book written by Steve Massey ‘Exploring The Moon’ available at www.myastroshop.com.au one can, on a nightly basis feast one’s eyes on a line-up of the Moon’s craters, crater chains, Riles, Wrinkle Ridges, Faults, Domes etc.
If at this stage you don’t own a Telescope and the outlay of thousands is not possible, then I find the Newtonian Telescope on a Dobsonian Mount around the 200mm (8”) aperture to be ideal for both adults and children to both enjoy and grow into. I’m especially fond of the Sky Watcher brand sold by Tasco Australia – the SW680 would be my choice for a beginner. The ‘eye pieces’ sold with this type of scope would be around the 25mm and 10mm strength and a Moon Filter would be very handy (the Moon can be very bright), good makes of these are ‘Meade’ or ‘Lumicon’ and are inexpensive. A light cloud layer also helps on Moon viewing nights, to cut out the ‘Glare’ somewhat. With this brand of scope (Newtonian) some adjustment (collimation) is necessary from time to time. This is easily done with minor tuition!
For now and in summary of our small companion in our lonely isolation, some figures, sizes, distances etc.
- Revolves around Earth at approx. 1.3km per second.
- Visible magnitude – approx. -12.50 to -13.00
- Average distance from sun – 93 million miles or 149 million km’s
- Diameter – 2160 miles or 3476 km’s
- Distance from the Earth – 239,000 miles or 384,000 km’s
- Sidereal revolution period – 27.32 days
- Lunar or Synodic month – 29.53 days
- Angle of Axial Tilt is – 6.7o from vertical.
So, having written the above, I will admit that I’m getting on a bit and busily searching for some of my faculties. So if you are younger and more able to pursue our Lunar Soul Mate, please step up! If not, I’ll be back next month with more on our little friend.
Thanks must go to my information sources, which are, in my humble opinion, among the best available.
Moon Phase Maps: www.astrovisuals.com.au
Exploring the Moon: Steve Massey – www.myastroshop.com.au
Atlas of the Southern Night Sky: Steve Massey & Steve Quirk – also available at www.myastroshop.com.au
The Astronomy Hand Book: Clare Gibson – available at Dimmicks Book Shops.