when sun has equal gravitational pull in all directions,why are the orbits of planets elliptical ???

Answer 1

The basic idea is that the pull of the sun's gravity on a planet accelerates the planet, and that acceleration can manifest itself in several ways: speeding up, slowing down, changing direction, or a combination of direction change and speed change.

When the planet is farthest from the sun it goes slowest and the acceleration is purely direction change as it arcs along the orbit at aphelion. As it continues along its path it starts speeding up as it 'falls' toward the sun. When it gets to the point of closet approach (perihelion) it is going fastest and again its acceleration is again seen to be pure direction change. After passing perihelion it starts to slow down as the sun's gravity puts on the brakes, in a sense. The planet coasts out toward aphelion and the process repeats.

If you do the mathematics using Newton's law of universal gravitation and his 2nd law of motion you can produce a description of exactly where the planet will be at any time.

To tell the truth, I think it's rather interesting that the planets' orbits are as close to circular as they are!

Answer 2

If the Sun's gravitational pull was NOT equal in all directions, then the orbits of the planets COULD NOT be elliptical.

An elliptical orbit around the Sun is the ONE AND ONLY mathematically possible orbit during which the planet will exchange its extra potential energy, when it is farthest from the Sun and moving slowest, for precisely the same amount of extra kinetic energy half an orbit later, when it is closest to the Sun and moving fastest. It was Isaac Newton who first understood that his proposed inverse square law of gravitation, supposing it to be equal in all directions, would give precisely this elliptical result.

Mathematics is stranger than you think!

Answer 3

To really understand how this works requires some mathematics, which I won't go into here; any textbook on the subject (e.g., the Feynman lectures) will have it. Suffice it to note that the gravitational attraction goes as 1/r^2, so that an elliptical orbit will have a higher velocity and kinetic energy when close to the sun, and smaller values at larger distances. As the planet moves in its orbit, the energy is exchanged between potential and kinetic; the potential energy is larger at larger distances. The orbits of the moon and artificial satellites around the earth are also examples of this, some satellites have circular orbits, and some don't, depending on how they were placed into orbit.

Answer 4

The sunlight has 324,000 cases extra mass than the Earth, and a million,000 cases extra mass that Jupiter, and subsequently that fairly extra gravitational charm from a distance than the two planet. The Earth and Jupiter additionally exert a gravitational charm on the sunlight, yet as a results of fact the sunlight is that fairly extra enormous their result upon it extremely is inconsequential. The sunlight and the planets orbit one yet another however the middle of gravity between them is on the middle of the sunlight. that's the reason the planets seem to circulate around the sunlight like the outer rim of a wheel with the sunlight being the hub. although, the two planets are in orbit around the sunlight, and for each foot they fall in direction of it, the sunlight strikes to the realm by using an equivalent quantity. In different words, the two planets are in a state of perpetual loose fall around the sunlight and firmly held in it incredibly is gravity field.

Answer 5

If you drop a rock without throwing it, it falls straight down, gaining speed as it falls. Similarly if Earth were held motionless in space and then let go, it would fall straight "down" into the Sun, gaining speed all the way as it went. If instead you throw the rock sideways, it curves to the ground, keeping the same sideways speed but gaining downward speed all the time. Similarly, if you held the Earth still and then threw it sideways, it would curve "down" to the Sun, keeping the same sideways speed and gaining speed down toward the Sun all the way. Now the Earth is WAY up above the Sun, so it has a long way to fall. Gravity of the Sun is weak way out here but gets stronger as you get closer, so the fall would gain speed faster at closer distances. This changing strength of gravity with distance is the key to understanding how an orbit can work. Now, it would take 3 months to fall the 93,000,000 miles to the Sun. All that time it is still moving sideways, and Earth even a pretty slow sideways speed would be enough to miss the Sun to one side when it got there. In that case Earth would zoom past the Sun at really high speed, but the gravity of the Sun at such a close distance is pulling really hard on Earth and it makes the path curve very sharply, trying to pull the Earth in. But Earth would be going SO fast that it's speed would win out and Earth would fly back up from the Sun after making a full 180 degree turn around the back side. But it would slow down as it went as the Sun's gravity tried to pull it back, and eventually, when it got back to 93,000,000 miles away it would stop moving away, just like a rock you throw up goes so high and stops. Then the rock falls again, and so would Earth. But it would still have its sideways speed so when it fell again it would miss the Sun again. What you have in that case is a very long, skinny elliptical orbit. If at the start you threw Earth sideways faster, it would miss the Sun by a wider margin, and the elliptical orbit would be fatter. If you threw Earth at just the right speed it would fall toward the Sun at just the right rate to stay at the same distance, and it would orbit in a circle. If you threw it a little faster then Earth would start fly off sideways faster than the weak gravity of the Sun at that distance could pull it back. But eventually the Sun's gravity would curve it back and the result would be an elliptical orbit with the LOW point at 93,000,000 miles. If you threw it fast enough, the Sun could never pull it back. The minimum speed needed to do that is called the escape velocity.

Answer 6

The Sun's orbital vector?

Just a S.W.A.G., but since these planets are orbitting a sun that is, itself, in motion, their distance is compressed when the planet passes in front of a forward moving sun. When the planet passes to the rear of this movement, the distance would lengthen. An orbit so compressed & stretched would be elliptical. Just a pet theory...

Answer 7

Here is another way to look at it. Imagine a up-side down cone (like an ice-cream cone, with a pointed tip). This cone represents the gravity from the sun, with the sun at the tip.

The orbits of the planets are drawn around the cone. The orbits are in a straight plane -- like cutting the cone with a long sharp knife. If the plane is level, then the orbit is a circle. But if the plane is tilted, then the orbit is elliptical.

Answer 8

Isn't it just that the Sun is slowly pulling the whole system into shape? In the beginning these rocks had individual velocities (i.e. speed and direction) and gradually came under the force of the suns superior gravity. Some shot off into outer space, some were 'just and so' captured (comets) and have highly elongated orbits, some settled into nice orbits - which will gradually become almost perfect circles.

Answer 9

its due to the variance of gravitational pull by the sun due to all factors like sunspots, the solar flares taking place and the amt of helium:hydrogen ratio which is ever increasing

Answer 10

Wrong question ;;; the real question is why is no planets in a circular orbit.