question 13
13. A reporter records the following observations of an astronaut from his space ship.
(a) The length of the day is same as observed on the earth.
(b) Sky appears black in colour.
(c) The star appears to twinkle while the plants do not do so as they do on the earth. Justify each statement.
Dera students,
(a)Earth spins around its own axis approximately every 24 hours (a sidereal day is 23 hours, 56 minutes, 4 second. On an equinox, day and night are of approximately equal duration all over the Earth. They are not exactly equal, however, due to the angular size of the sun and atmospheric refraction.
(b) Due to absence of atmosphere there is no scattering takes place and the sky appears black.
(c) As the planets are more close to Earth than the stars, they are not appearing as point sources of light. The planet covers a small circular area in space, when viewed from Earth. So, even if light from one point in the circular disc is blocked, light from other points reaches our eyes. Therefore, the light from the planets are not completely blocked from our sight and they do not twinkle.
Regards
Vijaya
(a)Earth spins around its own axis approximately every 24 hours (a sidereal day is 23 hours, 56 minutes, 4 second. On an equinox, day and night are of approximately equal duration all over the Earth. They are not exactly equal, however, due to the angular size of the sun and atmospheric refraction.
(b) Due to absence of atmosphere there is no scattering takes place and the sky appears black.
(c) As the planets are more close to Earth than the stars, they are not appearing as point sources of light. The planet covers a small circular area in space, when viewed from Earth. So, even if light from one point in the circular disc is blocked, light from other points reaches our eyes. Therefore, the light from the planets are not completely blocked from our sight and they do not twinkle.
Regards
Vijaya