Certain constellations are associated with certain times of year. For example, we see the zodiacal constellation Gemini in the Northern Hemisphere's winter (Southern Hemisphere's summer) and the zodiacal constellation Sagittarius in the Northern Hemisphere's summer. Why do we not see Sagittarius in the Northern Hemisphere's winter or Gemini in the Northern Hemisphere's summer?

The Earth's orbit around the Sun plays a crucial role in how we perceive constellations from Earth. Our planet follows an elliptical path, taking approximately one year to complete a full revolution. This journey changes our viewpoint of the stars, making different constellations visible at different times of the year.

Imagine standing on Earth, looking at the night sky. Because of the orbit, our perspective shifts daily. As the Earth moves to different positions in its orbit, the stars and constellations that were visible in one season might not be seen in another.

This orbital movement means certain constellations are aligned with the backdrop of the Sun during the day, making them invisible due to the Sun's brightness. Thus, the seasonal change in our night sky is a direct effect of Earth's continuous orbit around the Sun.

In the Northern Hemisphere, constellations like Gemini are visible in winter. This is because the Earth's night side is facing away from the Sun towards Gemini.

In summer, we see different constellations, such as Sagittarius. The night sky now faces the opposite direction, making Sagittarius prominent.

The Northern Hemisphere experiences different constellations due to the tilt of the Earth's axis. This tilt affects which part of the sky is visible at night throughout the year. Seasons also play a big role. The same tilt that causes summer and winter also determines the constellations we see. For example:

• Winter: Gemini
• Summer: Sagittarius

This cycle repeats annually as the Earth continues its orbit.

In the Southern Hemisphere, the visibility of constellations is the opposite of that in the Northern Hemisphere. For example, when Gemini is visible in the Northern Hemisphere's winter, it is summer in the Southern Hemisphere. However, the apparent constellations are still determined by which part of the sky faces away from the Sun.

Thus, during the Southern Hemisphere's winter, constellations like Sagittarius become visible. Similarly, in summer, Gemini appears in the night sky.

The tilt of the Earth’s axis and its orbit around the Sun affect the Southern Hemisphere similarly but in reverse order concerning the Northern Hemisphere. It means that as one hemisphere enjoys summer and sees certain constellations, the other hemisphere experiences winter and sees entirely different constellations.