The movement of the Earth affects what you see in the night sky. The time of night, the time of year and your latitude affect what constellations and planets you see.

https://vimeo.com/24253126

Man on beach under milky way

Finding Jupiter or the Southern Cross is easy if you know where to look — and that's easy too once you know how the movement of the Earth affects our view of the sky.

If you live in a city you might struggle to identify anything in the night sky besides the Moon — all those stars can look pretty random.

So how do you make sense of what's going on up there? It helps to know how living on a big spinning planet affects what part of the sky we see at any one time.

Once you know what the Earth is up to, the movement of the stars and planets over one night or an entire year starts to make sense.

You'll know where to look for planets and constellations, when to look for your star sign, and why cities on the same latitude see the same stars at night.

Circular lights in the sky

You can gaze at the night sky for five or 10 minutes and nothing much will happen. But if you could speed the whole night up and watch the sky in fast motion, you'd see the stars moving across the sky as one.

Stars rise in the east and set in the west, just like the Sun and Moon do. It's because the Earth spins from west to east, so everything in the sky comes into view as we spin towards it and leaves our view as we spin away from it.

But depending on where you are, not all stars rise and set. If you're in the southern half of Australia, looking south at the sky in fast motion, the stars there (including the Southern Cross) go around the sky in a circle.

For example in April, the Southern Cross is on its side in the early evening, but it becomes more upright towards midnight, like in the animation below.

The stars aren't really circling a point in the sky — we are. The point is the South Celestial Pole, the spot in the sky that lies directly above the South Pole.

The Earth spins on an axis that runs from the North Pole to the South Pole — it's like we're turning on a giant imaginary skewer.

If you look up at the sky from the North or South Pole, you'll always see the stars going in circles overhead, never rising or setting at the horizon. At the North Pole the stars circle the North Star, which lies exactly where the "skewer" is pointing.

If you went to the equator you'd see something quite different. The equator lies at a right angle to the Earth's axis of spin (the "skewer"), so every star rises in the east, goes straight across the sky and sets in the west with mathematical precision.

The downside is you can't see the celestial poles or the stars circling around them because the rest of the planet blocks your view.

In between the poles and the equator — at latitudes like southern Australia — you get a bit of both. You're far enough south to see the stars circling the South Celestial Pole, but because you're not at a right angle to the axis of spin, the stars don't go straight overhead as they travel from east to west.

Instead they move further north as they rise in the east, and further south as they set in the west. In the Northern Hemisphere, the stars curve towards south as they rise.

https://zippy.gfycat.com/FrighteningVerifiableAfricanhornbill.mp4