Could someone please explain my question regarding the Moon's behaviour? Thanks.

reply to post by Ozscot


Ok, here's the thing:
The world is round.
Let's imagine that the Moon is right over the equator, and that it's current phase is waxing crescent.
A man stands on the equator and watches it set.
Since he is on the equator, "vertical" to him is perpendicular to the Earth's axis.
Thus south is to the left, and north is to the right.
The Earth rotates west-to-east, so the setting Moon appears to be descending straight down to the horizon.
The Moon's axis is roughly parallel to the Earth's (it's actually a couple-dozen degrees off, but go with me).
That means the man on the equator will see the setting moon's axis oriented south-left/north-right.
The tips of the crescent are near the Moon's poles.
Thus the crescent will appear on its side, like a "U"

At the same time, a man near the South Pole looks at the Moon.
"Vertical", to him, is parallel to the Earth and [approximately] Moon's axis.
Thus south is up, and north is down.
That means the man near the South Pole will see the moon's axis oriented south-up/north-down.
The tips of the crescent are near the Moon's poles.
Thus the crescent will appear straight up-and-down, like a "C".
Also, since east-west is horizontal, the Moon won't actually be setting - it will seem to be skimming along the horizon.
A man near the North Pole would, for the same reason, see the crescent as straight up-and-down, but with the directions reversed.

The point of all this is as follows:

The further you are from the equator (i.e. the higher your latitude, either north or south), the more up-and-down the crescent will appear. Conversely, the lower your latitude, the more sideways it will appear.

Do you see where I'm going with this?

Scotland is ~55 - 60 degrees latitude north of the equator.
Australia is ~15 -40 degrees latitude south of the equator.
You spent most of your life living at a high latitude where the phases of the Moon mostly looked up-and-down, even when it was setting. Now you've moved to a lower latitude, where the moon often looks like it's laying on its side. It's no wonder that, once you noticed it (and subconciously realized you'd never seen it like that before) it didn't seem right to you.

So, for starters, you can quit kicking yourself. As a bonus, if some wise-arse ever asks you, "How do you know the Earth is round?" You can smile and say you've seen the proof for yourself (then you can punch 'im in the snot-locker, for me - please).

*****************

Addendum:

The Moon's orbit is actually inclined to the Earth's equator. This inclination varies between 18 & 28 degrees, and at the moment it's inclined at ~23 degrees. That means that, month-to-month, the Moon's orientation will change, so that next month's crescent will not be at exactly the same angle as this month's. Over a six-month period, it will rock ~46 degrees, then come-back in the six months to follow.

Hope this helps (it would have been better with pictures, but the good software is on another computer).

reply to post by Ozscot


Here's an illustration of how the moon would have looked from Sydney at 6:30pm on April 12th:



It was about 35 degrees above the horizon, in a NNE direction.

At 8:30, it would look like this:



It was about 38 degrees above the horizon, almost due north.

As you can see the apparent angle of illumination on the moon has changed. This is because we tend to judge that angle relative to the closest point of the horizon. Because the moon is fixed in orientation, as it moves through the sky, from east to west, the angle relative to the horizon changes.

Here's an animation that covers from 6:00pm to 12:00pm, showing how the moon moved through the sky, and how this affects the apparent angle of illumination on the moon: Animation

Originally posted by ArMaP
I have photographed the Moon almost every day since last Friday (I think I missed a day) and I haven't seen anything like that.

Pics, or it didn't happen

Due to the fact that as the round Earth rotates (as the day/night goes on), our perspective of the Moon changes.

To illustrate, I created this for another (similar) thread, but it fits this thread also (the arrow signifies the "top " of the Moon at moonrise -- which was meaningful to that other thread):
[atsimg]http://files.abovetopsecret.com/images/member/e600c974ad2c.jpg[/atsimg](please note that this is for the Northern Hemisphere, but a similar thing would happen in much of the Southern Hemisphere. In most of the Southern Hemisphere, you would be seeing the Moon move from the NNE to NNW sky rather than the SSE to SSW sky)

Ha ha, great explanations from some of you, and makes a lot of sense. However we are forgetting one thing. In the past If there was a say, half moon rising above the horizon with a perfectly vertical line of shadow. The moon would travel across the sky until it drops below the opposite horizon and the vertical line of shadow would not change its orientation at all. This is how it always was, and there are plenty of time lapse videos to prove it. So what has changed. That is how it was, and this is how it is. Why...

Originally posted by Dinoman
In the past If there was a say, half moon rising above the horizon with a perfectly vertical line of shadow. The moon would travel across the sky until it drops below the opposite horizon and the vertical line of shadow would not change its orientation at all. This is how it always was, and there are plenty of time lapse videos to prove it.

No, it's never been like that. It can't be like that due to the very nature of the motions involved.

Oh and one more thing. Peoples explanation of the moon shadow rotation would mean that if the moons shadow rotating through the night is normal behaviour. That would mean that seeing crescent moons would also be normal, and at least once a month. It was not normal in the past. Even people I meet that have no interest in the astronomy are always commenting or talking about the moon being different, and I have many people comment on how they can still see the dark part of the moon illuminated against its background, which I have also noticed many times myself. This too is not how I remember normal.

reply to post by nataylor


Are you saying we have always seen crescent moons in the sky. Like every time we have a waxing or waning moon, due to the moons shadow rotation. I dont think so. New to this but ill try to post some video I have so you can explain them to me.

Originally posted by Dinoman
Ha ha, great explanations from some of you, and makes a lot of sense. However we are forgetting one thing. In the past If there was a say, half moon rising above the horizon with a perfectly vertical line of shadow. The moon would travel across the sky until it drops below the opposite horizon and the vertical line of shadow would not change its orientation at all. This is how it always was, and there are plenty of time lapse videos to prove it. So what has changed. That is how it was, and this is how it is. Why...

Ok -- I'll start. Here is a video of the Moon in which our perspective of the "tilt" of the Moon changes as the night goes on:



I say this is completely normal for reasons I mentioned above. Also, the thousands of amateur astronomers out there who have watched the Moon for years agree this is normal.

Now that I posted a video example of the Moon's apparent tilt changing (which I say is normal), why don't you post your example (of which you say there are plenty) of the Moon's apparent tilt NOT changing as it moves across the sky for several hours.

reply to post by Soylent Green Is People


Lovely, video from the 15th Nov 2010. Exactly the same day the world and his friend started posting videos on youtube about something strange going on with the moon. Exacly the same date I stated earlier in this thread that I noticed the moon behaving like this. Got any earlier timelapse video my friend. I got many that shows different. Just trying to work out how to put youtube video up, cant find where to find the youtube numbers.

Originally posted by Dinoman
reply to post by nataylor

 

Are you saying we have always seen crescent moons in the sky. Like every time we have a waxing or waning moon, due to the moons shadow rotation. I dont think so. New to this but ill try to post some video I have so you can explain them to me.

Not sure what you mean by "always seen crescent moons." The moon has always gone through it's phases.

What I am saying about the orientation is this: Say, when the moon first rises, generally to the east, you paint a clock face on it, with 12 o'clock being straight up, relative to the horizon. As the moon goes across the sky, and sets generally in the west, the twelve o'clock position will now be pointing down.

Here's an animation I made in response to the OP's situation. As you can see, the relative angle of the face of the moon to the horizon changes as it moves through the sky: Animation

It's always been like this.

Originally posted by Dinoman
...That would mean that seeing crescent moons would also be normal, and at least once a month. It was not normal in the past...

Are you saying that seeing a crescent Moon at least once a month is not normal?

By the way, we actually go through two crescent phases every month -- one waxing and waning, and everything in between. Here is a chart showing the normal Moon phases throughout the lunar cycle (roughly 1 month):



and here is a calendar showing all of the phases for this year (2011):

Originally posted by Dinoman
reply to post by Soylent Green Is People

 

Lovely, video from the 15th Nov 2010. Exactly the same day the world and his friend started posting videos on youtube about something strange going on with the moon. Exacly the same date I stated earlier in this thread that I noticed the moon behaving like this. Got any earlier timelapse video my friend. I got many that shows different. Just trying to work out how to put youtube video up, cant find where to find the youtube numbers.

I was thinking you would have an earlier one showing that the "apparent orientation" of the moon does NOT change over the course of a day/night. You said there are plenty.

[yvid]

reply to post by Soylent Green Is People


sorry what I meant was crescent moon in the upside down smiley face position.

reply to post by Dinoman


You can embed a video like so:
You click on the "VID:YouTube" button on the "post a reply" page, then you put the part of the YouTube address after the "v=" in the blank provided.

I can help you out here. This is what you are trying to post:


I'd say that is only less than 1 hour of movement through the sky -- not an entire night (or day/night). It would be hard to notice the apparent change in orientation after such a short period.

I'd like to thank everyone for their replies - it seems I've touched upon something that many well educated people were unaware of - that the light on the moon changes as the evening progresses. Some of the diagrams and pictures above explain to me clearly what is happening.

I got terribly confused because In the pursuit of understanding things fully I checked out some time lapse video of the moon and saw this one - where the light doesn't change and obviously it leaves me somewhat confused. But I can see what you all mean with your diagrams and pics and it makes perfect sense! Thank you!

This was one of those videos I was referring to (from Chicago) where it doesn't appear to change...


Oz


.

reply to post by Dinoman


Here you go:



That video appears to cover only a few minutes, not long enough to notice any significant change in apparent angle.

We all know the stars do THIS during the night:



So if we imagine one of those stars being crescent-shaped and fixed on one of these arced paths, we can easily imagine how the orientation of that fixed crescent will change (as we see it) as it moves along that arc-shaped path during the night....

...i.e., it could rise looking more like a smiley face, and set looking more like a frown.

[yvid]