Here's why:

* Earth's Tilt: The Earth is tilted on its axis at approximately 23.5 degrees. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year, leading to seasons.

* Earth's Orbit: As the Earth orbits the Sun, the direction of the tilted axis remains constant. This means that different parts of the sky are visible from Earth at different times of the year.

Here's how it works:

1. Summer: During summer in the Northern Hemisphere, the North Pole is tilted towards the Sun. This means that the constellations visible in the Northern Hemisphere during summer are those that are located near the celestial north pole. These constellations are visible for a longer period during the night, as they circle around the North Star.

2. Winter: In the Northern Hemisphere winter, the South Pole is tilted towards the Sun. This means that the constellations visible in the Northern Hemisphere during winter are those located further away from the celestial north pole. These constellations are visible for a shorter period during the night.

Seasonal constellations are essentially a result of our Earth's movement and position in space. It's like looking out a window while on a moving train – the scenery changes as you travel.

Note: The constellations themselves are not actually moving, but our perspective from Earth changes throughout the year.