Q. Consider the following scientific observations over geological times:
Moon is moving away from Earth
Earth is moving closer to Sun
Mean solar day is getting longer
Earth’s rotation speed is getting down
Which among the above observations are correct:
Answer: 1, 3 & 4
Notes:
- Moon is moving away from Earth: This is a fact that has been verified by scientific observations and measurements. Over time, the gravitational interaction between the Earth and the Moon causes the Moon to slowly drift away from the Earth. The rate of this process is estimated to be about 1.5 inches (3.8 cm) per year. This gradual increase in the Moon's distance from the Earth has a number of consequences, including changes in ocean tides, the length of a day, and the shape of the Earth's orbit.
- Earth is moving closer to Sun: This statement is not accurate. The Earth's distance from the Sun varies over time as it moves in its elliptical orbit. However, over long time periods, the Earth's average distance from the Sun remains constant.
- Mean solar day is getting longer: This is a fact that has been verified by scientific measurements. A mean solar day is defined as the time it takes for the Earth to complete one rotation on its axis with respect to the Sun. Over time, the gravitational influence of the Moon and other celestial bodies causes the Earth's rotation to slow down, resulting in a gradual increase in the length of a day. Currently, the length of a day is estimated to be increasing by about 1.7 milliseconds per century.
- Earth's rotation speed is getting down: This is a fact that has been verified by scientific measurements. The Earth's rotation speed refers to how quickly the Earth is spinning on its axis. Over time, the gravitational influence of the Moon and other celestial bodies causes the Earth's rotation to slow down, which results in a decrease in the Earth's rotation speed. This gradual slowing of the Earth's rotation has a number of consequences, including changes in ocean tides, the length of a day, and the shape of the Earth's orbit.
Above question is part of 10000+ MCQs for UPSC (Prelims) Paper-1 course in GKToday Android app.
