Do constellations appear the same in northern and southern hemisphere? why or why not?

The visible constellations are definitely different between the Northern and Southern Hemispheres. In general, at any given point on Earth, only around 50% of the sky will be visible. We can understand this by considering the atmosphere as a sphere around the earth. The sky any person can view at one point can be compared to a giant dome equal to half of the sphere. And because the Earth rotates, the dome we can see changes, unless one is sitting directly on the North or South Pole.