Asked by Marie Cannon
Constellations do indeed appear to drift between the two hemispheres. This is caused by the tilt of the Earth’s axis. The Earth is tilted over by 23.5 degrees, as it orbits around the Sun the direction stays pointing roughly the same direction, but there is a slight wobble called precession. As we venture round our orbit it means that our view of the celestial sphere alters as well. This means that we see different constellations at different times. Some of these constellations can appear to move hemisphere for your viewing location. For example, here in the UK we can only see Scorpio during the summer months, for the rest of the year it disappears below the horizon. Technically the constellations are not actually moving, it is simply the movement of the Earth that is adjusting how we are viewing the sky.