# Planet rotation

#### serhiy1635

While I was chatting on some space forum, I`ve bumped into one interesting question. And I decided to post it here.
Why do different planets orbit the Sun faster? Not distance but speed. If you have some ideas, please share your information with me

• rod

#### rod

The *ideas* as to *why do different planets orbit the Sun faster?* goes back to the geocentric solar system of Claudius Ptolemy (motion around the Earth in circles, including the Sun moving around the Earth in a circle), later Copernicus (heliocentric solar system still used circles but around the Sun). The observations of Tycho Brahe using Mars (Tycho geocentric-heliocentric model), Galileo telescope observations, Kepler formulating the laws of planetary motion (elliptical motion, not circles) based upon Tycho Brahe study of Mars, and Isaac Newton.

"In the 1660s, Isaac Newton (1642-1727), armed with calculus, of which he was a co-inventor, developed laws of motion and gravitation, which encompassed the entire universe, more or less subsuming Kepler and Galileo. Kepler's laws retained a flavor of mutual independence, but with the new mathematics, Newton was able to derive enhanced versions of and unite the three. In his 1687 book, Principia Mathematica, he verified, as Kepler had strongly suspected, that they apply to all the solar system planets and by implication to everything everywhere. Newton modestly told the world that he stood on the shoulders of giants, and Johannes Kepler was certainly one of the giants.", ref - Governing the Planets, Sky & Telescope 138(2):58-62, 2019

My note - Newton's law of gravity and motion allowed mathematical modeling of the planets, elliptical orbits around the Sun and accurate position change predictions that Kepler developed from Tycho observations of the motion of Mars.

MS WWT has videos to watch, one is on Galileo. One of the arguments used against Copernicus to claim the Earth did not move, if the Earth moved around the Sun, the Moon would be left behind and not keep up. Galileo telescope observations of the small lights moving around Jupiter showed Jupiter could move as it did yet the tiny lights always kept up with Jupiter. Isaac Newton neatly explained all of this with the universal law of gravity. Thus the Earth could move around the Sun and the Moon be kept in place moving around the Earth, just like the moons of Jupiter do.

Last edited:
• IG2007, Catastrophe, serhiy1635 and 1 other person

#### Helio

The closer a body gets to a massive object (Sun) the faster it travels. It's similar to how a magnet works, the closer iron is to a magnet the harder it's pulled toward it.

We call this action of attraction for planets and such "gravity" but we don't fully understand just what it is. But we do know to an exact degree how it behaves.

Since objects in freefall will travel much faster near the Sun then they would only avoid crashing if they orbit much faster than those objects far from the Sun.

• Catastrophe and serhiy1635

#### serhiy1635

The closer a body gets to a massive object (Sun) the faster it travels. It's similar to how a magnet works, the closer iron is to a magnet the harder it's pulled toward it.

We call this action of attraction for planets and such "gravity" but we don't fully understand just what it is. But we do know to an exact degree how it behaves.

Since objects in freefall will travel much faster near the Sun then they would only avoid crashing if they orbit much faster than those objects far from the Sun.
Thank you so much for your answer)

• Catastrophe

#### Stellarwest

While I was chatting on some space forum, I`ve bumped into one interesting question. And I decided to post it here.
Why do different planets orbit the Sun faster? Not distance but speed. If you have some ideas, please share your information with me
Here below is a python program which calculates weights of two different objects at different distances. It could answer this question here.

Python:
``````# Python Program to Calculate Gravitational Force

# setting value of Gravitational Constant

# Reading weight and distance
while True:
G = (.00000000006674)
m1 = int(input('Enter weight of first body (Kg): '))
m2 = int(input('Enter weight of second body (Kg): '))
r = int(input('Enter distance (m): '))

# Calculating Gravitational Force
F = (((G * m1) * m2) / r**2)

# Displaying result
print(m1,'Weight of First Body Kg')
print(m2,'Weight of Second Body Kg')
print('{0:.100f}'.format(F),'Gravitational Force')
print('{0:.14f}'.format(G),'Gravitational Constant')``````
You can do an experiment with the code of 10Kg vs 100Kg at two different distances (from 1 meters to 10 meters) and when the two are closer the gravitational force goes up. I assume this would accelerate a body when closer to its heavier counter part than further out.

Output for 1 meter vs 10 at weights of 10Kg vs. 100Kg:

Enter weight of first body (Kg): 10
Enter weight of second body (Kg): 100
Enter distance (m): 1
10 Weight of First Body Kg
100 Weight of Second Body Kg
0.0000000667400000000000007280097748599279050552013359265401959419250488281250000000000000000000000000 Gravitational Force
0.00000000006674 Gravitational Constant

Enter weight of first body (Kg): 10
Enter weight of second body (Kg): 100
Enter distance (m): 10
10 Weight of First Body Kg
100 Weight of Second Body Kg
0.0000000006673999999999999907364854975387255531238395178661448881030082702636718750000000000000000000 Gravitational Force
0.00000000006674 Gravitational Constant

Last edited: