Here's why:

* Constellations are illusions: Stars in a constellation are incredibly far apart from each other. They just *appear* close together because we view them from Earth.

* Gravity's role: The stars in a constellation are bound to each other by gravity, but not in a way that creates a fixed shape. Gravity is the force that holds galaxies together, but individual stars within a constellation don't orbit each other.

* Perspective and movement: Over time, constellations slowly change because stars are constantly moving within the Milky Way. Our perspective from Earth also changes due to the Earth's rotation and orbit.

Think of it like this: if you were to look out a window at night and see streetlights lined up in a row, you might think they were connected. But in reality, they're just far apart and happen to be aligned from your vantage point.