The moon in Kenya

[Simpo Two]

I know there some fairly well-informed astronomers on this forum hence the post here.

A friend has just come back from Kenya, and tells me that the face of the moon appears rotated almost 90 degrees compared to how it looks in the UK. I can understand his other observation that the crescent of the crescent moon is underneath instead of to the side as there's quite a distance between here and Kenya - but I can't explain the apparent rotation. Any ideas folks?

[Nick M]

Bored, so I'm going to take a bit of a guess here, but...

- the same face of the moon is presented to the earth all the time isn't it ?

- so, if you're stood on the outside of a sphere in relatively high northern latitudes, you'll see the face of the moon at a certain angle to your 'horizon'. At the north pole you'd be 'vertical' if you drew a line up from the centre of the sphere.

- Move south and you're angle relative the centre of the sphere changes - at the equator you'd be at 90 degrees, the south pole 180, etc.

- so, if you move from relatively high northern latitude to a similar latitude in the southern hemisphere, you would have moved through an angle of, say, 90 degrees relative to the centre of the sphere.

- hence your 'attitude' compared the face of the moon would change.



.*sits back and waits to be flamed to hell and back *

[Simpo Two]

You're right, but two things.

First, the triangle made by UK - Kenya - Moon is very acute - hence the moon's face would appear to rotate but almost imperceptibly.

Second, he reports the moon's face as rotating left-right not up-down.



Of course he may have been suffering from too much jungle juice, but he's quite sensible with scientific stuff.

[Nick M]

Not sure the angle between the moon, UK and Kenya is relevant here.

For example - imagine a vertical disc which is 10m in diameter and you're stood at the top looking directly forwards at a circular object with a defined pattern on it about 100m away.

I now rotate the disc 90 degrees to the left (as if you were moving south on the same line of longitude), and two things happen:

1. you fall off;

2. your view of the object will have changed such that the pattern will have rotated from left to right.

Does that make any more sense ?

[Simpo Two]

I see - yes, that could work if the moon was low in the sky, but not high.



That Newton was a clever geezer.

[Nick M]

Indeed !

And don't even ask me how the earth's rotation features in the equation

[beano500]

Imagine the face of an apple in your outstretched hand.

Imagine turning your whole body around and keeping the apple at arms length with the same face towards you. Like your on a kids roundabout, looking out as the world goes past.

Where's the stalk of the apple?

Now imagine - without moving your apple - that you could take your face off and put it back upside down.

Now rotate yourself, like on that roundabout.

Imagine again the same face of the apple is facing you in your outstretched arm.

Where's the stalk of the apple?

[Hugo a Gogo]

Simpo Two said:

I know there some fairly well-informed astronomers on this forum hence the post here.

A friend has just come back from Kenya, and tells me that the face of the moon appears rotated almost 90 degrees compared to how it looks in the UK. I can understand his other observation that the crescent of the crescent moon is underneath instead of to the side as there's quite a distance between here and Kenya - but I can't explain the apparent rotation. Any ideas folks?

is this not just very simple? travelling from here to there, WE rotate through nearly 90°

the moon is the same way up, we are standing on the 'side' of the earth instead of near the top

[Nick M]

beano500 said:

Imagine the face of an apple in your outstretched hand.

Imagine turning your whole body around and keeping the apple at arms length with the same face towards you. Like your on a kids roundabout, looking out as the world goes past.

Where's the stalk of the apple?

Now imagine - without moving your apple - that you could take your face off and put it back upside down.

Now rotate yourself, like on that roundabout.

Imagine again the same face of the apple is facing you in your outstretched arm.

Where's the stalk of the apple?

I have no idea, because I got all dizzy and threw up !!

[Yellabelly]

beano500 said:

Imagine the face of an apple in your outstretched hand.

Imagine turning your whole body around and keeping the apple at arms length with the same face towards you. Like your on a kids roundabout, looking out as the world goes past.

Where's the stalk of the apple?

Now imagine - without moving your apple - that you could take your face off and put it back upside down.

Now rotate yourself, like on that roundabout.

Imagine again the same face of the apple is facing you in your outstretched arm.

Where's the stalk of the apple?

beano, have you been on the wacky baccy! " take-your-face-off and put it back...... upside..... down" !!!

That's some serious sh-t your puffing on!

[james_tigerwoods]

beano500 said:

Imagine the face of an apple in your outstretched hand.

Imagine turning your whole body around and keeping the apple at arms length with the same face towards you. Like your on a kids roundabout, looking out as the world goes past.

Where's the stalk of the apple?

Now imagine - without moving your apple - that you could take your face off and put it back upside down.

Now rotate yourself, like on that roundabout.

Imagine again the same face of the apple is facing you in your outstretched arm.

Where's the stalk of the apple?

How do you hold out the apple, twist your body around, on a roundabout with your face upside-down?

I think I need to eat something as that makes no sense to my food-starved brain.

Sorry!

[beano500]

[Dave^]

Can you prove it is even the same moon?

[Mr Whippy]

Hugo a Gogo said:

Simpo Two said:

I know there some fairly well-informed astronomers on this forum hence the post here.

A friend has just come back from Kenya, and tells me that the face of the moon appears rotated almost 90 degrees compared to how it looks in the UK. I can understand his other observation that the crescent of the crescent moon is underneath instead of to the side as there's quite a distance between here and Kenya - but I can't explain the apparent rotation. Any ideas folks?

is this not just very simple? travelling from here to there, WE rotate through nearly 90°

the moon is the same way up, we are standing on the 'side' of the earth instead of near the top

Hehe, well explained and it makes perfect sense

[Simpo Two]

Hugo a Gogo said:

is this not just very simple? travelling from here to there, WE rotate through nearly 90°

the moon is the same way up, we are standing on the 'side' of the earth instead of near the top

I see, yes, it must be a question of relative longitude as well as latitude. I was simply thinking of it as 'south'.

Ta!

ETA: And presumably from New Zealand, the moon appears upside down? (I went there but forgot to look)

Edited by Simpo Two on Wednesday 4th November 17:53

[havoc]

Simpo Two said:

Hugo a Gogo said:

is this not just very simple? travelling from here to there, WE rotate through nearly 90°

the moon is the same way up, we are standing on the 'side' of the earth instead of near the top

I see, yes, it must be a question of relative longitude as well as latitude. I was simply thinking of it as 'south'.

Ta!

ETA: And presumably from New Zealand, the moon appears upside down? (I went there but forgot to look)

No, because in NZ YOU are upside-down as well! (OK, cheap shot, but in principle it's true - the effect in NZ is that the moon is 'backwards', I think)


Re: Kenya - noticed exactly the same thing in Tanzania last month (photos to follow, I promise!)...so here's the science:-
- The "angle" of the crescent-moon depends NOT on your position relative to the moon (which, correctly stated, will act on a different axis), but your position relative to the SUN - the light source!
- So, someone standing at the equator on one of the Equinoxes (when the equator is level with the Sun) will see a crescent with the centre pointing straight-down, and someone at the Pole on one of the Equinoxes will see a Crescent moon with the centre pointing directly sideways.
- At any other place on the planet, your view of the crescent will be determined by the angle that your latitude makes to the plane of the ecliptic (i.e. the disc containing the centre of both the Earth and the Sun). This of course changes with the time of year, e.g. on Midsummers Day someone standing on the Tropic of Cancer will be OK the p-o-t-e (the effective equator).


Any questions?

[Simpo Two]

havoc said:

Any questions?

Yep. There are two issues here, (1) the crescent (simply a matter of lighting direction) and (2) the rotation of 'The Man in The Moon'. If travelling to the Equator rotates Mr Man 90 degrees, then logically extending one's travels to the Antipodes should rotate him almost upside-down, no?

[Hugo a Gogo]

Simpo Two said:

havoc said:

Any questions?

Yep. There are two issues here, (1) the crescent (simply a matter of lighting direction) and (2) the rotation of 'The Man in The Moon'. If travelling to the Equator rotates Mr Man 90 degrees, then logically extending one's travels to the Antipodes should rotate him almost upside-down, no?

yes

[Hugo a Gogo]

Simpo Two said:

Hugo a Gogo said:

is this not just very simple? travelling from here to there, WE rotate through nearly 90°

the moon is the same way up, we are standing on the 'side' of the earth instead of near the top

I see, yes, it must be a question of relative longitude as well as latitude. I was simply thinking of it as 'south'.

Ta!

no, not longitude, just latitude

[havoc]

Hugo a Gogo said:

Simpo Two said:

havoc said:

Any questions?

Yep. There are two issues here, (1) the crescent (simply a matter of lighting direction) and (2) the rotation of 'The Man in The Moon'. If travelling to the Equator rotates Mr Man 90 degrees, then logically extending one's travels to the Antipodes should rotate him almost upside-down, no?

yes

Correct-ish...as the equator, as we view it, shows the crescent as "points upwards", then either pole will show the crescent with "points sideways" - which was what I said in my first post - "backwards", rather than upside-down.