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The Moon for Southern Hemisphere Beginners

.....Answering those Tantalising Questions.....

• What are the Moon Phases?
• Why does only one side of the Moon face the Earth?
• How is the Moon lit up at Full Moon?
• What is a Lunar Eclipse?
• What is on the "Dark Side" of the Moon?
• Why is the Moon in the Northern Hemisphere upside down
from how it looks here in the Southern Hemisphere?

• What is Apogee and Perigee?
• Did Humans really land on the Moon?

NB: There is a penumbral eclipse of the moon on February 9th, 2009. The moon will not be totally darkened but will appear as if it's in shadow. The entire eclipse is visible from New Zealand. The Moon enters the Earth's penumbra at 1:38:46am (NZ time) on February 10th. No change will be visible at this time. However, by 3:38:15am (NZ time) the lower parts of the Moon, as seen from New Zealand and Australia, should be distinctly shaded. Over the next 2 hours the shading will disappear with the Moon leaving the penumbra at 5:37:40am.



Moon Map
Here

What are the Moon Phases?:


Viewed from The Southern Hemisphere
(but NOT to scale!)

February 2009
Moon Phases


  New Moon   Feb 25
  First Quarter  Feb 3
  Full Moon   Feb 10
  Third Quarter   Feb 17

You will notice that the phase times vary in the Southern Hemisphere (particularly New Zealand) from the Northern Hemisphere. That's because of our time difference (New Zealand is 12 hours ahead of GMT/UT and in summer during daylight saving, 13 hours ahead). We also see the moon 'upside down' so the side which is shining seems the opposite from the Northern Hemisphere. In fact, anywhere you go in the world, you will see the Moon and Universe in a slightly different way.

The diagram above-left shows the Moon Phases (how the Moon's light appears to us as we view it from Earth). It shows the Sun and how it shines on the Moon and the Earth, as viewed from the Southern Hemisphere. Imagine that the Earth is "tipped on its end" so that you are looking at the South Pole directly in the centre of the Earth. The monthly chart at right shows which side of the Moon is alight at each different quarter, viewed from New Zealand (the dates may be one day out from other places because we are near the dateline). Both the northern and southern hemispheres of the Earth can see the Moon. However, the southern hemisphere sees the Moon "upside down" from how the northern hemisphere sees it. You can see how New Zealand views the moon when you view the movie "Lord of the Rings"!

The Moon's appearance changes from being a "New Moon" to a "First Quarter Moon" then to a "Full Moon" and on to "Third Quarter Moon", as it makes a full circle in its rotation around the Earth. It takes approximately 27.3 days (called a "sidereal month") to orbit the Earth but because the Earth is constantly moving in its own orbit around the Sun, it takes approximately 29.5 days to go through a full set of Moon phases (called a "synodic month"). The light of the Moon is only the reflection of the Sun's light upon it, as it has no light of its own.

The Moon travels eastward around the Earth. However, as it does so, it keeps only one side (and always the same side, of course) facing the Earth. So, although we see the Moon go into increasing shadow as it turns away from the Sun during it's cycle of phases (which takes 29.5 days), we are still seeing the same side of the Moon.

When it is a "New Moon" phase, we on Earth cannot see the Moon because the Sun is shining only on the other side of it (see the diagram above).

Apart from the main Moon phases, the Moon is referred to as in "waxing crescent" which is when it is approaching from New Moon to First Quarter and "waning crescent" which is when it is phasing from Last Quarter to New Moon. It is in "waxing gibbous" between First Quarter and Full Moon and "waxing gibbous" when it is between Full Moon and Third Quarter.

That is The Acorn Tree Oracle's explanation of what causes the "Moon Phases". (Now, isn't that clear as mud?!)

Ask the Acorn Tree Oracle a Question about the Moon!


Why does only one side of the Moon face the Earth?

The best way to understand this is to see what would happen if the Moon did NOT rotate. Here is a diagram to illustrate it:
(don't get it mixed up with the phases diagram above, which is simply showing the Sun shining on the moon)

Both the Moon and the Earth turn anti-clockwise.

The Moon revolves around the earth in the same direction and same amount of time, that it also takes for it to rotate (27.3 days). This results in the Moon always keeping the same side turned toward the Earth and the other side turned away from the Earth. It is called "synchronous rotation". The side turned away from the earth is called the moon’s "dark side", even though it is actually lit up for half of the time. It's just that we can't see it from here.

If the Moon did NOT rotate, we would be able to see all its sides, gradually, as we proceeded through the month.


How is the Moon lit up at Full Moon?:

It would be understandable to wonder how the Moon can be lit up by the Sun when the Sun and Moon are on opposite sides of the Earth (the time when Full Moon happens - see Moon Phases diagram above).[note: click your back button on your browser to return to this spot.] This is able to happen because the Moon orbits at a slight angle from the Earth's orbit around the Sun. Consequently, the Sun's rays can zoom past the Earth and shine on the Moon!:) ... except during an eclipse of course!


What is a Lunar Eclipse?:

A Lunar Eclipse is when the Earth comes between the Sun and the Moon, so it casts a shadow over the Moon. It doesn't happen very often (maybe once or twice a year at most) but when it does, it's quite eerie, especially if it is a Total Eclipse.

A Total Lunar Eclipse is when the Moon is completely overshadowed and it becomes very dark or blood-like in colour. Partial eclipses, when the Moon is not so completely in the shadow of the Earth, may not be so obvious. The next Total Lunar Eclipse, visible from New Zealand, is on the 28th August, 2007.

In the Bible, there is reference to when the Moon will become like blood. This could possibly refer to a Total Eclipse of the Moon when the events which are described in this Bible passage, happen.


What's On the Dark Side of the Moon?:

The dark side of the moon is heavily cratered. It seems that it's taken a lot of battering over the years! But the Dark Side is not really always dark. It would be better if we called it the Far Side of the moon, being the side which always faces away from us (apart from a slight nodding movement called "libration"). The Far Side ("Dark Side") of the moon is in total bright sunlight when it is in our "new moon" phase, because that is when that side completely faces the sun.
You want to see a pic? OK, have a look at the NASA photo taken during the Apollo 16 mission, here.


Why is the Moon in the Northern Hemisphere upside down from how it looks here in the Southern Hemisphere?:

The Moon orbits near the equator of the Earth. In the southern hemisphere, we're standing on the opposite side of the globe from the "northerners", so we are "upside down" from each other! So we see the Moon from a completely different vantage point (ie "upside down"!). In fact, we in the southern hemisphere view most of the stars quite differently than from the northern hemisphere.


What is Apogee and Perigee?:

Lunar apogee is when the moon's orbit is at its most distant from the earth and perigee is when it is nearest to the earth. This happens at different times for each month and for each year, and at different distances. For example, this year (2002), the most distant apogee was on March 14 at about 1pm (NZ time of course!) when it was 406,704 km away from earth. The nearest perigee this year occurred on Feb 28 at about 8.30am when it was 356,897 km away. Every month it is different.
Does this mean that the moon looks smaller if it is farther away? Yes, it does. A full moon near perigee looks a lot bigger and brighter than a full moon near apogee. Anything which is closer looks larger and that is how it is with the moon.

Apogee and perigee for the month of July 2002, for example, was as follows:

Perigee: July 15, 0146hrs (1.46am) : 367,851 km away from earth.
Apogee: July 2, 1936hrs (7.36pm): 404,210 km away from earth.

In 2002, the moon was at its closest perigee for the year on February 28th. It was at 356,897 kms.


Did Humans really land on the Moon?

If there had been no Apollo landings on the moon, it would be possible but VERY difficult to keep it a secret. There are some reasons to believe we really did get to the Moon, here, at NASA's Thursday Classroom. Maybe the real test will be when we can get on board a spacecraft which will take many of us there, just like we can go to another country. But of course, that's a little way in the future yet as there are a lot of hurdles to jump first (like the Van Allen radiation belts!).
Mars is likely to be the planet next colonised by our species but the Moon could be a drop-off base also. Science fiction may come to life!



Contact The Oracle
Ask The Oracle about the Moon



Copyright S Alexander 2002
Please Ask The Oracle if you wish to copy graphics etc, OK?!
Goodonyamate!

Except animated moon which is courtesy of Jo's World


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