So WHY are the orbits elliptical?? Is there a short understandable answer?

Question

There was a similar question and here is a part of one answer..but it doesn't make any sense to me...

"..external force which existed during the formation of earth. This force on earth imparted earth a velocity that was greater then critical velocity to revolve in a circular path around sun but less than the escape velocity. Any body imparted with such velocity will rotate in an elliptical orbit.."

I can't make sense out of this explanation, but is it similar to the following statement....This is what I have read from other sources..: If the balance between large body's gravitational pull and centrifugal force is not perfect, the orbit will be elliptical, but to me it would mean that either the Moon will fall into the Earth or it will leave Earth's orbit, depending which force will be stronger...I really don't understand!!! Is there a purely logical explanation without complicated mathematical formulas???

Answer 1

In simple English...It means that the pull of gravilty is less at 2 points so the orbit expands at those points before being pulled back in by gravity, and so the eliptical shape occurs.

Answer 2

Think about what choices there are - a square? a triangle? Those don't make sense because the orbits should be somewhat smooth - there are no discontinuities in the physics of the problem. So you basically can choose from circles or ellipses. If an ellipse happens to have both radii the same, then you have a circle, so a circle is really just a special case of an ellipse. Sometimes you do get a circular orbit by "getting lucky" as someone else here put it.

If the satellite is crashing in towards the center, then it is just pulled in by gravity and it crashes, and we don't have to worry about its orbit. Likewise if it is zinging away too fast for gravity to hold it in orbit, then it just goes off into outer space, and we don't have an orbit to bother us. It's only in those special cases where there is balance between moving fast enough that gravity won't suck it in, but slow enough that it doesn't zing off into outer space, that we have an orbit. The ellipse shape (sort of a squashed circle) allows for some trade off between velocity and gravity. The satellite actually moves faster when it is in that part of its orbit closer to object it is orbiting. It moves slower when it is farther away. If you get lucky and things are perfectly balanced, it moves at the same speed all the way around the orbit, and keeps the same distance from the center - i.e. a circular orbit.

Answer 3

Keep in mind that objects in orbit are just continually "falling," they only have a fast enough "lateral" velocity that they don't hit the object that they are orbiting.

There is a famous illustration (I think it was DaVinci) that shows someone firing a projectile off a mountain at different velocities and a round earth. If you could shoot it fast enough it would "fall" at the same rate that the earth's curvature changes. Too bad I can't show a picture.

Anyhow, projectiles generally follow a parabolic path assuming a small range of distance where the earth is essentially flat. They move laterally at a constant velocity (l/t) (neglecting losses) and fall at a rate determined by acceleration of gravity, g, but a l/t^2 term nonetheless. This function over time assuming x is the lateral velocity and y the vertical, is a parabola.

Now expand that to the case where "lateral" and "vertical" don't really mean anything because you're out in space, with no "level" ground to remind you what is lateral. Now both terms are l/t^2 and the general solution is an ellipse. Ax^2 + By^2= constant. Only in perfect conditions does A=B, and then you have a circle.

I know that wasn't a very short answer, but hey, in Einsteinian curved space all orbits are circles.

Answer 4

The Sun is a gaseous (fluid) body, not solid; its mass shifts around. Similarly, the Earth has the Moon in orbit around it, so that the center of gravity of the Earth-Moon pair is constantly shifting. If you have two bodies, far removed from the gravitational influence of everything else, it is easy to show that their orbit is circular. But when you begin introducing multiple other bodies, close enough to affect one another, they all influence each other, and the orbit is no longer perfectly circular. It becomes elliptical.

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Answer 5

A circle is defined to be an ellipse with zero eccentricity - how "elliptical" it looks. Since this is only one of an infinite number of possible shapes for an ellipse, it would be very surprising to find a perfectly circular orbit anywhere. Even if there was one, the slightest gravitational influence from a passing asteroid or comet would stretch it out of shape.

Not to worry, though, we know elliptical orbits are stable or we wouldn't be here to talk about them.

Answer 6

Circular orbits can be created by very accurately accelerating an object to an exact velocity at the exact time and place. There is a very remote chance that this could happen by accident, but elliptical orbits happen more by chance. It's really just a probability thing.

Answer 7

In metaphysics, we learn astrology is based on the fact
there are different strains within the magnetic field of the Solar System. It is not constant. This is most likely the reason
orbits are eliptical, rather than perfectly round.

Answer 8

with the aid of fact circles are suitable, and not something interior the Universe is acceptable. although, we are particularly close. we've the backside eccentricity ("out of around") orbit of the different merchandise interior the photograph voltaic gadget. The eccentricity of the Earth's orbit is at present approximately 0.0167, purely indicating that our orbit is nearly around, the semiminor axis is ninety 8.6% of the semimajor axis. Over hundreds of years, the eccentricity of Earth's orbit varies from purely 0.0034 as much as 0.058 as for this reason of gravitational attractions between the planets. there is not any reason that our orbit *could no longer* be completely around, it particularly is purely that with the aid of character of planetary and different-stellar formation, it particularly is *no longer likely.* yet with the aid of fact of our very nearly-around orbit, it makes existence lots greater conceivable. you are able to think of approximately it in this way... with the aid of fact of geometry and Newton's regulation of primary gravitation, there are purely 4 diverse paths that an merchandise passing on the element of the sunlight can take. the 1st is a hyperbolic orbit -- the object is available in from area in direction of the sunlight with lots capability that it swings around the sunlight, yet nevertheless with adequate capability to flow returned out into area on a diverse direction... a trajectory direction that ought to look style of like a stretched out letter "U" (hyperbolic). 2nd, the object ought to are available from area with out adequate capability to flee from the sunlight's gravity properly and could then be captured in an elliptical orbit with the eccentricity of the orbit based upon the object's preliminary capability. Thirdly, the object ought to have *precisely* the impressive volume of capability had to be captured in a splendidly around orbit. finally, the object ought to no longer have adequate capability to be certain any style of orbit and it may spiral into the exterior of the sunlight and dissipate, which we are able to all agree could suck. considering Earth (and each thing else interior the photograph voltaic gadget) congealed out of a dense planetary disc, we natives of the gadget have been all imparted with frequently elliptical orbits, no longer with the aid of fact we could no longer have completely around orbits, purely with the aid of fact we did no longer type alongside our paths with completely even accretions, boost, completely uninterrupted as we shaped. purely... oh properly, rather no longer likely.

Answer 9

In fact, the moon IS crashing into the earth

Answer 10

http://en.wikipedia.org/wiki/Two-body_problem

This is about as simple as it can get I'm afraid.