What are the effects of the earth's revolution around the sun?

Answer 1

Depends on what you mean by "effects"!

By itself, Earth's revolution around the Sun doesn't do much. By comparison, think of the Moon: it revolves around the earth without rotating on its axis, and its relation to the Earth is pretty static. The Earth doesn't rise or set on the Moon, it just hangs there motionless in the sky (more or less, I'm leaving out some minor motions). Such would be the view from earth if all the Earth did was revolve around the sun! The same side would always be in daylight, making it incredibly hot. Consequently, the opposite hemisphere would be incredibly cold, getting no sunlight at all.

However, the earth doesn't just revolve around the sun; it rotates on its axis, and its axis is tilted compared to "the plane of the ecliptic", or the imaginary disk that the Sun, Earth, and all other "real" planets revolve in. So, because the earth's axis is tilted and that tilt always points in the same direction as the Earth goes around the Sun, the hemisphere getting the more direct light at one point in the Earth's orbit will get less direct light 180 degrees away in the orbit. In short, the revolution of the Earth around the Sun with the tilt in the earth's axis causes the seasons. Of course, we wouldn't notice those seasons if the Earth didn't also rotate on its axis, giving us day and night. In fact, if it didn't rotate, we couldn't even define its axis!

Another effect of the revolution of the Earth is the difference in length between the solar and sidereal day, or the day as measured from noon to noon and the day as measured from when a fixed star rotates back to the same position respectively. Naively, you'd think that these would be the same, but the sidereal day is slightly shorter! I'll let you puzzle this one out for yourself. Imagine the earth going around the sun and at the same time rotating on its axis: what would have to happen to make the sidereal day shorter than the solar day? Longer?

Another interesting effect is the fact that the Earth doesn't exactly revolve around the sun but rather a mutual center of gravity that is a weighted average dependent on the relative masses of the two bodies. This center of gravity is off-set from the center of the sun and both the sun and the earth revolve about this. For this reason the sun does a little circle orbit of the same period as the earthly year.