On Tue, 8 Apr 2008 21:41:10 -0700 (PDT), Richard <riplin@[EMAIL PROTECTED]
>
wrote:
>On Apr 9, 3:05 pm, Robert <n...@[EMAIL PROTECTED]
> wrote:
>> On Mon, 7 Apr 2008 22:09:08 -0700 (PDT), Richard <rip...@[EMAIL PROTECTED]
>
wrote:
>> >On Apr 5, 3:19 pm, Robert <n...@[EMAIL PROTECTED]
> wrote:
>> >> As a point of interest, if you are standing within 6 km of either
pole, you
>> >> will actually see the sun rise in the west .. once per year.
>>
>> >You seem to have a strange idea about what one sees when within the
>> >polar areas.
>>
>> Applying an adjective such as strange without elaboration does not
establish the validity
>> of that adjective.
>>
>> The Earth rotates counter-clockwise, viewed from the north. That's why
the sun rises in
>> the east in most places. The Earth orbits the sun clockwise. Close to
the poles,
>> rotational effects become insignificant. The Earth's orbit and 22
degree tilt causes
>> sunrise at the poles. That's why the sun rises in the west there.
>
>That is exactly the sort of 'strange idea' that you seem to have. In
>fact it is completely wrong headed nonsense.
>
>Close to the poles the 'rotational effect' is exactly the same as
>anywhere else: the sun moves at 15 degrees per hour across the sky. It
>happens that at the poles for many months that movement across the sky
>is entirely below the horizon and for many other months it is entirely
>above the horizon.
>
>At some point near the equinox the sun is circling only just below the
>horizon and it completes the circle in 24 hours, at some point it will
>become fractionally visible as a 'sunrise' and this can occur at any
>point on the horizon depending on the relationship between earth's
>orbit and rotation and the height of the observer.
>
>Your claim that it 'rises in the west' may be true for one observer
>one year but false for another some short distance away or standing at
>a different height. It will also vary each year.
>
>If two observers both see the sun's first glimpse at the same time
>they may be on different sides of the pole. One would see it 'in the
>west' and the other 'in the east'. Or possibly 'in the north' and 'in
>the south'.
>
>6 hours later the sun is at a different point of the horizon 90
>degrees away and another observer may see it for the first time.
>
>The sun may also dip back and 24 hours later 'rise' again in a
>somewhat different place and for a slightly longer time while it
>travels along the horizon.
After giving this some thought, I concede you are right. Perhaps these
thoughts will shed
more light on the answer.
The key concept is that the number days in a year is not an integer. There
are ~365.24
days in a year. Suppose on year one the sun rises at the north pole March
21 (vernal
equinox) on a meridian (line of longitude) that goes through Greenwich,
England. On year
two, it will rise six hours later, on a meridian that goes through the US.
On year 3, it
will rise on the international date line. On year 4, it will rise on a
meridian that goes
through Asia. On year 5, it will rise again almost, but not exactly, on
the Greenwich
meridian.
The second concept is the definition of east and west. Conventionally, it
is relative to
the observer. That is meaningless at the north pole, where the only
direction is south. An
alternative definition is the (Anglo-centric) one of relative to
Greenwich, England. If
the sun rises on a US meridian, it can be said to 'rise in the west'; on
an Asian
meridian, it 'rises in the east'. What about the other two? Common sense
says that if
you're facing north, east is on your right. Thus, the international date
line is north and
the Greenwich meridian is south.
I disagree with your assertion that the sun can rise, dip below the
horizon, then rise
again the next day. There are three wobbles in the Earth's orbit, called
Milancovitch
cycles, whose periods range from 20,000 to 100,000 years. The Earth
doesn't wobble and
reverse in one day.
This explanation is from my original thoughts, not gleaned from any
website.
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