# Help in explaining a question on gravity

• B
• trees and plants
In summary, the conversation discusses how bodies with large mass differences orbit around the common center of mass, known as the barycenter. This is due to the conservation of momentum and is explained mathematically through the two-body problem. The barycenter of the Solar system is not located in the center of the Sun, and this is the latest correct view of the orbits of the solar system. The conversation also mentions the Earth's wobble as it orbits the barycenter and how this does not affect observations of other objects in the Solar system.
trees and plants
Hello. I have this question: do you know why a physical body with bigger mass makes another one orbit around it like the sun does in the solar system and not the opposite of this? Thank you.

The bodies actually orbit around the common center of mass.

You mean the sun also orbits around the center of the solar system which is different than the sun?

How is this explained mathematically? Do you know?

Google "barycenter". A planet orbiting a stationary Sun violates conservation of momentum because the Sun has zero momentum and the planet's momentum is changing. Both need to orbit a common center.

In the case of objects with large mass differences, the barycenter is very close to the center of the larger mass. So "Earth orbits the Sun" is close enough to the truth for most purposes.

davenn
So saying heliocentric system is not correct, center of the solar system is correct which is not the sun. I understand now that they were approximations so far, scientists were trying to describe it and so far this is the latest correct view of the orbits of the solar system?

universe function said:
You mean the sun also orbits around the center of the solar system which is different than the sun?
Yes, the Solar system's barycenter is not located in Sun's center.
https://spaceplace.nasa.gov/barycenter/en/
universe function said:
How is this explained mathematically? Do you know?
I think only two-body problem can be solved analytically. System with multiple bodies need to be solved numerically.
https://en.m.wikipedia.org/wiki/Two-body_problem

The masses of the Earth and Moon are nearer equal to each other and the phenomenon is more appreciable. The Earth has a definite 'wobble' as it 'orbits' the barycentre, once a month and there are no other large bodies in Earth orbit to spoil the effect. The barycentre is about 3/4 of the distance from the centre of the Earth to its surface - pretty significant, eh?
I don't think that amount of wobble is great enough for it to cause enough parallax to affect observations of other objects in the Solar System, though.

## 1. What is gravity?

Gravity is a natural phenomenon by which all objects with mass are brought towards each other. It is the force that keeps planets in orbit around the sun and causes objects to fall towards the ground.

## 2. How does gravity work?

Gravity is caused by the curvature of space and time around objects with mass. The more massive an object is, the more it curves the space around it, and the stronger its gravitational pull. This pull decreases with distance, which is why we feel less gravity on the moon compared to Earth.

## 3. What is the relationship between mass and gravity?

The greater the mass of an object, the stronger its gravitational pull. This is because a larger mass means a greater curvature of space and time around the object, resulting in a stronger gravitational force.

## 4. How does gravity affect the motion of objects?

Gravity affects the motion of objects by pulling them towards the center of the Earth or another massive object. This pull causes objects to accelerate towards each other, which is why objects fall towards the ground when dropped.

## 5. What is the difference between mass and weight in relation to gravity?

Mass is a measure of the amount of matter in an object, while weight is a measure of the force of gravity acting on an object. Mass is constant, but weight can vary depending on the strength of the gravitational pull. For example, an object will weigh less on the moon because of its weaker gravitational pull, but its mass will remain the same.

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