Final answer:
When someone says 'in the east,' it means 'in the eastern sky.' This is because the sky is considered a celestial sphere that turns around us. So, when you see a big rainbow in the east, it means you are seeing it in the eastern sky.
Step-by-step explanation:
When someone says 'in the east,' it means 'in the eastern sky.' This is because when we observe the night sky, stars and other celestial objects rise in the east and set in the west, just like the Sun and Moon.
The idea of the sky being a celestial sphere that turns around us was believed by ancient Greeks.
They thought of the sky as a transparent crystalline material with the stars embedded in it. So, when you see a big rainbow in the east, it means you are seeing it in the eastern sky.