[Nibile]

i know there are quite e few very competent people here, and not only climbing wise, so:
yesterday while driving back from a soaked magic wood, the moon came out of the clouds, and g/f asked me if, when its a full moon, its seen as a full moon all over the globe, i.e. south of the equator.
i obviously said yes, and kept driving nonchalantly.
was i right?
why?
what is that create the shade on the moon?

ps its not about ben moon.

[Rice Boy]

was i right?

No.

However I am not at liberty to explain why as THEY are always listening.

[SA Chris]

 Well Yes and No.

My understanding is that is seen as more or less the same phase by everyone in the world who can see it, but it can't always be seen by everyone, ALL OVER the globe, as in some places it isn't night (if that makes sense).

In fact this may be horsecrap now i think about it.

[Rice Boy]

Sorry, just read that back not as helpful as it played out in my head??

I've studied the phases of the moon many times over my academic life but I still haven't a clue, facinated but haven't a clue.

Girlfriends ask the simplest but hardest questions at times, recent ones include:

Why is the sky blue?
Why does the moon wax/wane?
Have you booked the holiday?

etc. . .

It seems a higher education in this country does not prepare you (me) for the world (women) at large. Ask me about surface complexation in clays and I'll show you the world . . .

[Jaspersharpe]

I nominate this thread for the "Least Helpful Replies 2007" award. My own included.

[dave]

you'd think the moon would be far enough away (i.e. 30 times the diameter of the earth) to look more or less the same to all obsevers on the correct side of the earth. techincally there aught to be a difference particularly at the extremes of the phase but its probably not noticable, but probably is detectable.

the sky looks blue cos the atmophere scatters shit loads more blue light than any other wavelength.

[andy_e]

wikipedia is your friend

[Johnny Brown]

Jeez. Its pretty simple...

The moon phase is always the same, doesn't matter where on earth you are.

Its caused by the sun shining on the moon, just as night and day are caused by the sun shining on earth.
Half of either planet is always lit, half is dark.

The only way you could change is if you were in a spacecraft and went sideways away from the moon-earth alignment.

As the moon orbits the earth, we see a half-moon when its lit from the side (ie when the moon is at 90 degrees to the sun), a full moon when it is behind us relative to the sun - which can occasionally be eclipsed by the shadow of the earth, and a new (invisble) moon when it is between us and the sun (which it can occasionally block out causing a solar eclipse)

So you see the same phase from anywhere on the earth, though not at the same time - you have to wait for the earth to spin so you can see it.

It does look a bit different though as the angle of the half-moon changes depending on latitude - ie at the equator its horizontal like a saucer or dome, at the poles its vertical more as we in the uk see it.

I could go on...

[rc]

In reverse order:-
The sky is blue due to Rayleigh scattering. The sun beams out white light, the molecules in the atmosphere scatter short wavelength light, so the blues (and violets) get scattered and this is what you see when you look at a 'bit of sky' (rather than at the sun). In space there is no atmosphere so when you look away from the sun (or any other star) it is all black - no atmosphere means nothing is scattered so you only get light hitting your eye directly from the source (ignoring bendy light things for now).

The moon thing.
Get a large orange, a table tennis ball, turn the light off and tell your girlfriend to shine a torch at you. You'll work something out.

For the less experimental:
Imagine looking at the system from somewhere out in space. The half of the moon facing the sun is lit, the other half is not. Wherever the earth is out in space, everyone on earth pretty much sees the moon exactly the same. So whatever phase the moon is in, those that can see it will see the same phase.
Caveat 1: some people are on the side of earth facing away from the moon - they see nothing
Caveat 2: some people are on a bit of the earth where it is daytime so maybe they dont see much
Caveat 3: moon phase may look very slightly different due to the diameter of the earth - not everyone is seeing the moon from _exactly_ the same point in space. Look up the distance between the moon and earth vs the diameter of the earth to get an idea of how big this effect might be.

[rc]

Looks like I was the slowest kid in class today.

So how about why is the sea/ocean blue. Is it innately blue or is is a reflection of the sky?
And why is the sun yellow...specifically is the sun yellow when viewed from space?

[Rice Boy]

the sky looks blue cos the atmophere scatters shit loads more blue light than any other wavelength.

I'd gone with Genesis 1:2 or there abouts; 'and when God doth chose his pallete, he doth selected turquoise for the sky (with a little spilt grey over Manchester) to marry with the heavens'.

[dave]

the sea just reflects the sky. at sunset the sea looks red, on a cloudy day it looks grey. think of it as a big wavy mirror.

does the sun look yellow? perhaps in cartoons. if you want to see what the sun looks like from in space go out on a clear night and you'll be looking at any number of other suns.

[rc]

But often the sea looks other colours too - very green say or whatever. So the main component is reflection but with some perturbations if it's chock full of algae/seaweed? Is that the accepted situation?

So what colour do you reckon the sun is if it is not yellow? White?
I heard that on wavelength terms alone it emits slightly more green than the other colours. Is yellow purely a psychological thing? Is it due to the blue being scattered out of the white leaving yellow? Also seems to be some theory about the nonlinear response of the human eye to light and the perception of yellow is something to do with an afterimage of looking into the sun...

[andy_e]

Yes- sea content does heavily affect colour- think of why the red sea's called the red sea, because it's underlain with desert sands.

[Johnny Brown]

I issue with this thing about not being able to see the moon if its day. Why not? You can see it fine unless its cloudy, of course, but then no one mentioned cloudy nights so I guess thats not what you meant.

Yeah the sun does look yellow. Its a colour temperature thing, like what we're all familiar now we have digi cameras that need white balancing.

Mind you, we should be careful to note that colour is not an innate property of light, just a property of our perception of it.

[andy_e]

Colour, no, but wavelength is, and wavelength determines colours in our eyes...

[Johnny Brown]

wavelength determines colours in our eyes...

To an extent, yes it does. But we don't always perceive the same wavelength as the same colour.
Our eyes automatically 'white balance' by shifting colours across the wavelengths to correct for the varying qualities of the incident light.

[Rice Boy]

Yeah the sun does look yellow. Its a colour temperature thing, like what we're all familiar now we have digi cameras that need white balancing.

Why does our star look yellow/white if it's burning extremely hot whereas a blue heat can be created at lower (?) temperatures within Earths atmosphere? Is this anything to do with the presence of the atmosphere?

On (off) the subject, thought the film Sunshine was a let down, cross between Solaris, Event Horizon and 2001 but never matching their qualities. The special features with commentary from Brian May (possibly his name) of Manchester Uni is facinating, talks about space/quantum theory/star lifecycle very clearly. Science needs people like him to communicate these funky ideas.

[rc]

I issue with this thing about not being able to see the moon if its day.
Yeah the sun does look yellow. Its a colour temperature thing, like what we're all familiar now we have digi cameras that need white balancing.

If that was prompted by my post  - I was only thinking that presumably if the moon is almost in the same position as the sun you wont see it? We've all seen the moon in daytime...

What is the digi-camera 'colour temp' thing? Does this simply refer to a white-ish but non-uniform mix of frequencies? Does the temp thing refer to the equivalent black body radiation?
Ok - I wiki'd it myself http://en.wikipedia.org/wiki/Color_temperature

I'm a skeptical w'pedia user so am not necessarily willing to believe this - depite it bringing back my what colour is the sun question
When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright yellow light (sunlight in the strict sense) and heat. here 

[Jim]

I issue with this thing about not being able to see the moon if its day. Why not? You can see it fine unless its cloudy, of course, but then no one mentioned cloudy nights so I guess thats not what you meant.

Just makes me wish I could get my hands a photo of froggat with the moon above it broad daylight

[Johnny Brown]

I was only thinking that presumably if the moon is almost in the same position as the sun you wont see it?

Well no. You didn't specify it was a new moon though:

So whatever phase the moon is in, those that can see it will see the same phase.
Caveat 1: some people are on the side of earth facing away from the moon - they see nothing
Caveat 2: some people are on a bit of the earth where it is daytime so maybe they dont see much

What is the digi-camera 'colour temp' thing? Does this simply refer to a white-ish but non-uniform mix of frequencies? Does the temp thing refer to the equivalent black body radiation?

Its only when you start photographing stuff that you realise what a remarkable job our eye/brain does in maintaining apparently constant colour in differing lighting.

Yes the temperature thing is related to the black-body. (the sun being yellow is related to this - its temperature is in the midrange for a star hence giving light somewhere between red and blue)

However its complicated by the fact we call reddish (eg sunsets, tungsten lightbulbs, candles) lighting 'warm' when in fact its colour temperature is low (2000-5000K), and bluish lighting (open shade on a blue-sky day, midday tropical sun) cold when in fact its temperature is high (10,000- 50,000K)

Digital cameras can be set to render a scene as we perceive it, rather than with the colour cast caused by the lighting. In the old days you used different film or coloured filters.

[rc]

Just makes me wish I could get my hands a photo of froggat with the moon above it broad daylight

two moons in the peak in broad daylight?

[SA Chris]

Nib already said

ps its not about ben moon.

in his first post.

[Rice Boy]

Wealth of knowledge on this site is an understatement. A team should be sorted out for that 'beat the brainiacs' (load of bollocks) TV show.

Just remembered: The moon smiles when waning in Africa! Again a perspective thing non?

[Johnny Brown]

It would smile when waning (fourth quarter) when rising and when waxing (first quarter) when setting.
Unfortunately it'd frown for the opposite, ie when waning and setting, so your proverb doesn't quite stand up.