Q1.
After two hours, observe the Big Dipper again. Has it moved? Again, draw its orientation and note down the time.
Answer
Yes, it has clearly moved — and it has also turned, so the whole seven-star pattern is tilted differently against the same trees or buildings on the ground.
Do the sketching honestly: draw the ground line and a fixed tree or building first, then the seven stars above it, and write the time beside the sketch. Fig. 12.7 is the record made by a student in Pune on the night of 1–2 April:
| Time | Where the Big Dipper is seen |
|---|---|
| 7 pm | Low in the Northeast |
| 9 pm | Higher, still towards the Northeast |
| 11 pm | Highest, nearly due North |
| 1 am | Beginning to come down, past North |
| 3 am | Lower, towards the Northwest |
| 5 am | Low in the Northwest |
Why it happens: the Earth turns through 15° every hour (360° ÷ 24 h). In two hours it turns 30°, so the whole sky appears to slide back by 30°. That is a big, easily visible shift — about the width of three fists held at arm's length.
Tip: do all the observations from the same spot on the same night, and always draw the same tree or building. If you change your standing place, the comparison is spoilt.