[Tfug] Wallpaper criteria

[Bexley Hall]

On 1/9/2013 12:49 PM, Bexley Hall wrote:

[attributions elided]

>>>> The brightness on the left is the Sun just about
>>>> to appear and it will take just over an hour and a half to move across
>>>> the screen entirely.
>>>
>>> ?? Why? Doesn't it show the current terminator?
>>
>> Just a matter of timing. If you can see the Sun pass directly behind
>> the Earth then the terminator is necessarily perpendicular to the
>> observer. If I were looking at my desktop at, say, 2PM, then I would
>> definitely see the terminator slowly moving from East to West, And,
>> of course, my view settings are on a fixed point on Earth. If I
>> alternatively chose to view from a fixed point like the Sun, then I
>> would see the rotation of the Earth and little, if any, movement of
>> the terminator.
>
> Understood. My comment is why "an hour and a half"? This suggests
> your earth is rotating faster than normal? (??) Maybe I don't
> understand what you're saying...
>
> E.g., in my setup, it takes 24 hours for Tucson to reappear in the
> center of the display -- "high noon".

Ah, I think I've sussed this out!  Because your vantage point is
10 earth diameters (?) above beantown, the Sun only occupies the
chord represented by the display's width for a small portion
of it's (apparent) rotation around *you*.  I.e., the other
22.5 hours it is off to the side of the display and, at times,
even "behind your head"!

[Typical "hub" thinking:  the universe revolves around beantown!  :> ]

OTOH, if your vantage point had been at 10AU, you would likely see
the sun coming *around* the Earth -- at times behind it, on either
side and even in *front* of it!

--don