Cassiopeia doesn't actually look different today than it did in the past. It's a constellation, which means it's a pattern of stars that appear to be close to each other in the sky. The stars themselves are incredibly distant and don't change their positions noticeably over human timescales.

Here's why it might seem like Cassiopeia looks different:

* Earth's Rotation: The Earth rotates, causing the stars to appear to move across the sky throughout the night and over the course of the year. Cassiopeia's position in the sky changes depending on the time of night and the time of year.

* Perspective: Our perspective from Earth affects how we see constellations. Depending on where you are on Earth and what time of year it is, Cassiopeia might appear higher or lower in the sky, or even be hidden below the horizon.

* Light Pollution: In areas with a lot of light pollution, it can be harder to see fainter stars, making constellations appear less distinct.

In summary, Cassiopeia's appearance changes due to Earth's motion and our own perspective, not because the stars themselves are changing.