Write a paragraph about "Why the constellations appear to move across the sky". (Thanks if you help!! Means a lot! :D)

The constellations appear to move across the sky because of Earth's rotation. Earth moves from west to east, so the stars look like they appear from the east. Stars move across the sky during the day, but because of the Sun, we can't see them.  

Explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.