Question

At noon, the sun and the earth pull the objects on the earth’s surface in the opposite direction. At midnight, the gm and the earth pull these objects in the same direction. Is the weight of an object, as measured by a string balance on the earth’s surface, more at night as compared to its weight at noon?

Answer 1

Hint This is a critical question, it requires some good knowledge on astrophysics to answer this question. We should know about the tidal force and the gravitational pull of sun on earth to understand this question.

Complete step by step answer
If you ask will there be a change in the weight of an object in noon as compared to night the answer is yes. If we consider only the sun and the moon to be the determining factors that cause difference in weight of the object, the answer is no. Even though there is a change in weight it would be a negligible amount.
There are a lot of determining factors other than the Sun, and we know that there is no gravitational neutral point in the universe, as the distance would have to be infinite, for in inverse square law to produce zero gravity. The gravity of the sun is about $0.00589{\text{ m/}}{{\text{s}}^2}$at the radius of the earth's orbit, or about $0.0006$of the earth's gravity, $g = 9.81{\text{ m/}}{{\text{s}}^2}$
It is true that the tidal force of the sun affects earth but its effect is the same on day time and night time.
A tidal force is referred to a situation where a body is under the gravitational influence of another body. In case of sun and earth, the earth is under the influence of the sun. Since the sun is very far away from the earth the tidal effect of sun on earth is small. But it does not differ in daytime and night time. It has the same effect all the time. The moon also has a tidal effect on earth since the moon is way closer to earth than the sun; it has a major part of the tidal effect on earth.
The earth is in orbit around the sun, which is to say it's effectively always falling towards the sun but missing. Because the sun is attracting the earth and its mass equally (in terms of acceleration) and when the spring balance measures the difference, it only sees the earth's gravity not the sun's gravity.

Note Most of the students don’t understand this question. To get a better understanding about this question students should get to know about the tidal force, gravitational pull of the sun and moon on earth.