Stupid question perhaps...

I guess I am missing something obvious but I don't know what.

Lets say:

S = Sun
St = star
E = Earth

OK, in winter we have

______________________S______________E_________-
_______________________St

So the earth is on the "left" of the sun (I know there is no left or
right in space but bear with me).

During the night, the star can be seen because the dark side of the
earth is facing that direction.

Six months pass:

_-
__E_______________S_______________________________ ____________________St


This time the dark side of the earth is facing the opposite direction
(I know, no absolutes etc).


So, surely there should be a massive change in the visible stars
between seasons? But is there such a difference? I thought that most
stars are visible all year round. That doesn't see to fit with that I
have above.

Can anyone explain it in simple terms?

On Jul 21, 1:30 am, cqmman wrote:
I guess I am missing something obvious but I don't know what.

Lets say:

S = Sun
St = star
E = Earth

OK, in winter we have

______________________S______________E_________-

_______________________St

So the earth is on the "left" of the sun (I know there is no left or
right in space but bear with me).

During the night, the star can be seen because the dark side of the
earth is facing that direction.

Six months pass:

_-
__E_______________S_______________________________ ____________________St

This time the dark side of the earth is facing the opposite direction
(I know, no absolutes etc).

So, surely there should be a massive change in the visible stars
between seasons? But is there such a difference? I thought that most
stars are visible all year round. That doesn't see to fit with that I
have above.

Can anyone explain it in simple terms?

There is exactly that massive change.

When you look at say Scorpius (to the South) in the summer at
midnight, six months later at midnight you wont see Scorpius at all it
will indeed be opposite the Sun, Instead you will see Orion.

The thing is that during the course of a night you can see much more
than half of the sky (unless you are located at one of the poles ;-)).
Just after sunset looking straight up you are looking more or less at
right angles to the line between the Sun and Earth. A few hours later
at midnight, straight up is now opposite the Sun, a few hours later
again just before dawn, straight up is again at right angles to the
Earth - Sun line but in the opposite direction to what it was just
after sunset. In the winter when the twilight is short you can of
course see more than in the summer. You are also limited by you
latitude. At the poles you can only ever see half the sky, whereas at
the equator you can see nearly all of it in one night except that part
of the sky close to the Sun. If you move south of the equator for
example you can't see Polaris at any time of year or night.

When you are looking at Polaris in the Northern hemisphere and the
stars near it you will notice that during the course of a night these
stars never set, they are said to be circumpolar. They are even always
in the sky during the day.

To explore the sky and what you will see from your location at various
times of year, I recommend you download a planetarium program. You
tell the program where you are located - they usually have lists of
most cities in the world or you can enter your latitude and longitude.
The program will then display the sky based on the clock on your
computer but you can change that to set any time and date you like
usually +/- a few thousand years from the present. Here is a very good
freeware program called Skycharts - probably has a lot more features
than you will ever need. Select the link that says 'Complete
Package' (don't worry about all the optional star catalogues and stuff
listed)

http://www.stargazing.net/astropc/download.html

On 20 Jul, 15:44, wrote:

The thing is that during the course of a night you can see much more
than half of the sky (unless you are located at one of the poles ;-)).
Just after sunset looking straight up you are looking more or less at
right angles to the line between the Sun and Earth. A few hours later
at midnight, straight up is now opposite the Sun, a few hours later
again just before dawn, straight up is again at right angles to the
Earth - Sun line but in the opposite direction to what it was just
after sunset.


Cool. Thanks very much for explaining it all.