Activity 12.3: Let us explore, Do you observe that the Big Dipper appears to move. Class 7
mediumActivity 12.3: Let us explore, Do you observe that the Big Dipper appears to move. Class 7
Question 1.
Do you observe that the Big Dipper appears to move around the Pole Star (notice just the movement even if you cannot see the Pole Star)?
Answer:
The Earth’s axis of rotation points very close to the Pole Star in the Northern Hemisphere. Therefore, the Pole Star appears nearly stationary in the sky from the Earth. All the stars appear to move around it.
Question 2.
Why do different stars appear in the night sky over the course of a year? Class 7
Answer:
As Earth orbits the Sun, our night time view shifts slightly each day. It is because of the following reasons:
- Earth’s orbit takes a full year, and each night we look out in a slightly different direction.
- Some constellations are seasonal—like Orion, which shines in winter skies. while Scorpius dominates summer nights.
- The Sun blocks certain stars during the day, so the ones opposite the Sun become visible at night.
Question 3.
I have noticed that we go through a cycle of seasons every year. Is it related to the revolution of the Earth around the Sun in some way? Class 7
Answer:
The Earth’s axis of rotation is not upright with respect to the orbit, but is tilted. The Earth maintains this tilt as it orbits around the Sun (Fig.). The tilt of the Earth’s axis and the spherical shape of the Earth gives rise to seasons.
Question 4.
Could the light from the Sun get blocked by the two planets which are revolving between the Earth and the Sun? Class 7
Answer:
No, however the Mercury and Venus also pass between Earth and the Sun, but they are very small to block a significant amount of sunlight.