How does a moving body stay in a circular orbit?

Answer 1

It is the so-called swept area per unit time that remains constant in an eliptical orbit. Picture a planet in an eliptical orbit around the sun. Draw a line from the sun to the location of the planet at any given instant of time. Draw another line from the sun to the location of the planet at, say, one week later. The two segments drawn and the path of the orbit make a geometric figure. It's like a "slice" of the elipse of the planet's orbit, and it has a given area. Got it? Pick another spot in the orbit of the planet and draw a line to it. Then draw another line to where it is one week later. Again, the two segments and the curve of the planet's orbit form a geometric "slice" of the elipse. Any "slices" (and there are an infinite number of geometric possibilities) of the elipse created by the week of elapsed time will have an equal swept area as described by the line segments drawn from the sun to the location of the planet at the beginning and end of that week. The last bit of information needed to tie this together is that the planet is moving more slowly when it is farther from the sun than it is when it's closer. The segments drawn to create the "one-week slice" when the planet is farther out will be longer, but the slower movement of the planet will make the "slice" a bit "narrower" than the one-week slice of the planet when it's closer in. Pick any starting point in an orbit and draw a segment. Pick any length of time, be it an hour, day, week, month, or whatever, and draw another segment. Using that same length of time, draw more segments and create more "slices" of the elipitical pie. They'll all have the same swept area.

Answer 2

If an objects gravitational force is exerting itself on another celestial body the body will also be attracted to the other body creating the ecliptic path. For the planets to revolve in circular paths around the sun they must not exert a force back upon the sun. The sun must also remain in a single place. We are creating the ball attached to a pole by a string where when the ball is hit it creates nearly a perfect circle. This is due to centripetal force.

Reference(s): My Brain

-Brian

Answer 3

I am not sure about the second factor, but the first is gravity. Classically we would think of the planets taking a curved path through space, due to the force of gravity between them and the sun. In the relativistic view, the planets actually travel in a straight line, but through a space-time which is curved by the masses therein. Either way, the planets' elliptical orbits are due to gravity.

The other factor could be inertia? As long as nothing gets in their way, there is nothing to stop them from going forward in their orbits.

Answer 4

The normal tendency for a body is to move in a straight line, at constant speed. The only way for a body to move in a circle is if there is a force pulling it towards the center of the circle. In astronomy, when planets move around the Sun (or other stars), moons move around planets, etc., this force is gravitation.

Answer 5

A moving body may stay in its circular orbit through the gravity and balance present around it.

e.g

How the planets rotate without falling out of their orbits.

Answer 6

The elliptical object is the result of the interaction of the laws of movement (inertia), and the gravity of the central object.