why constellations are different and rotates differently in the southern hemisphere?

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why constellations are different and rotates differently in the southern hemisphere?

In: Earth Science

Any stars that are above the North Pole, like Polaris, can’t be seen from the Southern Hemisphere because you can’t see them through the earth.

Any stars or constellations that are above the South Pole, like the southern cross, can’t be seen from the northern hemisphere because you can’t see through the earth.

Imagine you’re in your front yard, and look at the neighbors across your street,

Then walk to the backyard, and look at your neighbors back there.

Now imagine instead of your house, it’s the earth.

If you’re standing at the North Pole, and look up, you see all the stars “above” the earth.

If you’re standing at the South Pole, and look up, you see all the stars “below” the earth.

You can’t see the North Star (and all the northern constellations) from the Southern Hemisphere because the earth is in the way.

So there are some constellations that you can only see from one hemisphere because the earth gets in the way, and there are some you can see from either hemisphere because they’re “up” from the equator.

The reason some constellations come and go with the seasons is because of the sun, if the stars for the constellation are on one side of the sun, and earth is on the other side of the sun, then the sun gets in the way.

The southern constellations don’t “rotate differently,” they still move from east to west over the course of a night as the earth spins on its axis.

We can chart stars’ positions on a globe by indicating which part of the Earth each star is directly above at a given time.

As the Earth rotates, each star effectively traces out a latitude line on the globe.

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**Why stars rotate differently in different places:**

They don’t. All of the stars are rotating exactly the same way as all of the other stars.

They’re not rotating around the north pole or the south pole (although it might look that way if you try to squish the globe into a flat sky map), they’re just rotating around the Earth’s axis.

(In reality, of course, they’re standing still while *we* rotate around the Earth’s axis.)

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**Why different stars are visible from different places:**

How high a star is above the horizon depends on how its current position on the globe compares to your own. If it’s at your position, it’ll be directly overhead. If it’s 90° from your position, it’ll be on the horizon. If it’s more than 90° from your position, it’ll be below the horizon and you won’t be able to see it unless you climb a sufficiently-tall ladder.

So what stars you can see (assuming you remain at ground level) will depend on what latitude you’re at:

* If you’re at 52°N latitude (e.g. London or Berlin), then stars below 38°S will never rise and stars above 38°N will never set.
* If you’re at 40°N latitude (e.g. New York or Beijing), then stars below 50°S will never rise and stars above 50°N will never set.
* If you’re at 34°S latitude (e.g. Buenos Aires or Sydney), then stars below 56°N will never rise and stars above 56°S will never set.