Re: Being careful with directions

[Leigh Palmer <palmer@SFU.CA>]

> Now hang on a minute! Just WHERE might you be (and WHEN) to see these
> due south or north sunrise/sunset/
>
> The arctic circle perhaps? Are you SURE????
>
>
> Seems to me that sunrise/sunset directions have got to stay away from
> due north/south by ~23.5 degrees?

Above the arctic circle (from the hemispheric chauvinist's
point of view) there must be two days each year when the Sun
sets and then very soon rises*, very nearly in the north.
Below the antarctic circle there are two days when it rises
in the north and then almost immediately sets. It should be
no surprise that these are nearly the same days for places
the same number of degrees from the equator north and south.

I highly recommend that anyone who undertakes the teaching
of astronomy obtain a copy of "Starry Night Pro" and play
with it a lot before undertaking the task. As a solid state
physicist I tried this (teaching astronomy) for the first
time two decades ago. I'm now aghast at the thought of some
of the misconceptions I must have had then which I passed on
to my students. I could have used "Starry Night Pro" then!

This is an appropriate topic today, since today marks the
end of the Sun's residence in positive declinations, our
spring and summer. We can be quite smug in realizing that
our autumn and winter will be shorter than spring and summer
by a significant amount.

Anyone want to guess by how much? Has this fact ever been
pointed out to you before?

Leigh

*Both sunrise and sunset have definitions which must be
taken into account. Prediction of sunrise and sunset times
can only be approximate because atmospheric conditions
affect them, and the effect on time is greatest for just
the cases we are discussing here.