Planets in gravitational well
The explanations here are based on a pushing theory of gravity. For the proof that gravity is a pushing force that can be blocked, read Gravitational forces on objects.
Far in space, gravitational force coming from one direction is almost cancelled by gravitational force coming in opposite direction. An object in that position continues in strait line because the net force on the object is zero.
Because of all its atoms, the sun blocks some of that gravitational force coming from space around itself. If it was possible to see the density of gravitational force coming from space near the sun, the density close to the sun would be less than far away. In this drawing of a frozen picture of gravity, every black pixel would represent gravity. The sun is represented by the red circle.
Gravity from space is blocked partially by the sun; gravity density is lower close to the sun and increases far from the sun according to distance squared.
For example, the above graph shows at a distance of 1E+10 m the intensity measured in special units would be 100 but at a distance of 1E+20 m the intensity would be 400 units.
Gravity coming from all regions of space was first emitted by all the atoms in universe. The sun itself is also an emitter of gravity. That means close to the sun gravitational force from the sun is bigger that in space around. That extends to a certain distance from the sun and density decreases with the square of distance.
For example, at a distance of 1E+5 m the intensity measured in special units would be 450 but at a distance of 1E+10 m the intensity would be only 200 units.
At a certain distance from the sun, the density of gravitational force from one side is almost equal to the density of gravitational force coming from the direction of the sun.
That makes a kind of big sphere; the skin of the sphere is where gravitational force is almost equal on each side of a line pointing toward the sun.
That region is the gravitational well. Planets cannot go in strait line because in doing so, they enter a region where the gravitational force from outside is now bigger and they are pushed back towards the sun. When they approach the sun, the same thing happens in opposite: the gravitational force coming from the sun is now bigger and the planet is pushed away, In that manner, the planet goes around the sun and is a satellite.
Region around the sun emitting in all direction added to what is emitted from space causes a different density region. If we add the gravitational force from the sun and from space, we have something similar to that drawing, showing the low density zone of gravitational force all around the sun.
The blue line is for the gravity from space that was partially blocked by the sun and the red line is the gravity emitted by the sun. It goes to almost zero at far distance.
Depending on its speed, the planet finds the distance away where the force towards the sun equals its centripetal force. The mass and the speed of the planet will permit to find an equilibrium point and it becomes a satellite to the sun. Planets are situated in a zone from 5.80E+07 m to 6.00E+09 m.
Following the equation (F = Gmm/dd) there is a possibility to have planets between the sun and Mercury. There is no such planet there. This is because of the gravity well described here. A planet closer to the sun would be pushed away by sun radiation of gravity unless its speed was very high and its mass was bigger than Saturn or of the sun itself.
This also explains why most comets do not fall into the sun as they should because of the high pressure of the gravity emitted by the sun at close distance. That emitted gravity does push the comet’s tail away from the sun. Only a direct hit toward the sun will allow something to fall on the sun.
If we add all forces going towards a planet as coming from the sun position to forces from space pushing toward the sun, we have this picture.
NEGATIVE VALUES: FORCES PUSHING TOWARD THE SUN
POSITIVE VALUES: FORCES PUSHING AWAY FROM THE SUN
VALUES FOR A STRAIT LINE JOINING THE SUN TO A PLANET.
Blue line = intensity of gravity emitted by the sun
Magenta line = intensity of gravity emitted by the stars blocked partly by the sun
Pale blue line = intensity of gravity coming from all regions of space pushing toward the sun.
Green line = centrifugal forces
Purple line = total forces on a planet: gravity forces plus centrifugal forces
Brown circles = possible position for planets, between 7 and 10.
N.B. The sun is at 0 on vertical axis.
N.B. The units used on vertical y-axis are for comparison of forces toward the sun.
N.B. The distances away from the sun are the exponent value in meters.
Thus 4 on x-axis is 1 x104 meters. 20 is very far, being 1 x1020 meters.
N.B. Note that the planets are situated at a distance between 5.80E10 meters and 6.00 E12 meters, very close to the values of the graph because that is where the centrifugal force is almost equal and opposite to the total forces pushing the planet toward the sun . The planet is forced to go in orbit around the sun.
N.B. This also explains why Pioneer satellite, far away from the sun is slowed down. The force of gravity from space directed toward the sun is becoming much bigger than the gravity emitted by the sun at large distance because the force from the sun is decreasing with the square of the distance. The forces from space do not decrease like that.