Why does the celestial sphere rotate once everyday?

Answer 1

EVERYTHING rotates. The Sun, the planets, all the asteroids, they are all spinning around the galaxy and spinning around themselves.

The most likely reason WHY everything spins is that the original planetary nebula was itself spinning, and conserved angular momentum as it contracted. When the matter fell into the gravitational well of the mass that would eventually become the Sun, each atom had its own original velocity, and as the atoms collided on the way in, it all averaged out to be a rotation. Everything in our solar system spins counter-clockwise when viewed from a point high above the "north" pole; all the planets orbit that way, and most of the objects SPIN that way.

Answer 2

No, The earth and moon revolve around their common center of gravity, called the barycenter. The earth is so much more massive than the moon that the barycenter is within the body of the earth. It is constantly moving of course, because of the combined effects of earth's spin and the moon's orbit.

Answer 3

Not quite. Actually, the earth and moon both orbit the same point once every 27.32 days.

The point is their common center of mass ... the point between the earth and moon

where the pivot would have to be in order for them to balance if they were on a see-saw.

Since the earth has about 80 times more mass than the moon has, the pivot has to be

80 times farther from the moon than it is from the earth. It just so happens that the

point winds up inside the earth, but that's not a problem. It just looks like the moon

is orbiting the earth, but actually they both orbit that point.

Answer 4

It doesn't. From the point of view of the Earth or someone on it, the moon orbits

in an elliptical path. The reason is: Because that's the way gravity works.

Take Newton's simple equation for the gravitational force and direction, and if you

have enough algebra, geometry, and calculus to be able to massage the equation

for a while, you can show that every closed gravitational orbit is an ellipse. In fact,

you can derive all three of Kepler's 'laws' mathematically ... the first of which is that

the orbits of the planets are ellipses with the sun at one focus.

Answer 5

There are many questions in physics and astronomy in which the question "Why?" does not make much sense. We observe facts; we hypothesize about patterns. We don't always know "why" things are the way they are.

This is one of them. The Moon does orbit the Earth 12 and a fraction times per year. That's a fact. We have no idea if there is some sort of reason why this is true; but it IS true.

Answer 6

Because the earth spins all the way around, once a day.

Answer 7

Because there are only 2_ something days in February and then February has 1 but March has 2.

Answer 8

It is being pulled by another objects gravitational pull.

Answer 9

It takes the Earth 24 hours to make one complete rotation on it's axis, so a day lasts 24 hours.

Answer 10

The center-directed force of Earth's gravity pulls the moon into a nearly circular orbit around Earth. :)