Does Gravity Between Two Equal Mass Objects Cancel Out?

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The discussion revolves around the concept of gravity between two equal mass objects, specifically in a hypothetical scenario where two identical apples fall simultaneously from antipodal altitudes toward a homogeneous Earth. It emphasizes that while both the Earth and the apples exert gravitational forces on each other, the effect of the Earth's movement is negligible compared to that of the apples due to their relative masses. The participants clarify that Galileo's principle demonstrates that all objects fall at the same rate in a vacuum, but this does not imply that the Earth and an apple fall toward each other equally. The conversation also touches on the idea of whether the gravitational forces of two equal masses would cancel each other out, concluding that they still exert a significant force on one another despite the net acceleration being zero. Overall, the thread explores the nuances of gravitational interaction and the implications of mass and acceleration in such scenarios.
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Galileo was first to demonstrate that all objects fall at the same rate in the absence of an atmosphere. As it is said that the Earth and the Apple fall toward each other but apple looks a lot to falls to the Earth as compared to the falling of Earth toward the Apple which is so tiny to be detected.

Let's imagine Earth is a homogeneous sphere and two identical apples start falling simultaneously from same ANTIPODEAN altitude in the absence of all other gravitational attraction including atmosphere.

So what would be the direction of accelaration of earth?

If net accelaration of Earth is zero in aforementioned scenario then would gravity "g" of two equal spherical spheres/ planets cancel each other if placed on each other?
 
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zarmewa said:
Galileo was first to demonstrate that all objects fall at the same rate in the absence of an atmosphere. As it is said that the Earth and the Apple fall toward each other but apple looks a lot to falls to the Earth as compared to the falling of Earth toward the Apple which is so tiny to be detected.

Let's imagine Earth is a homogeneous sphere and two identical apples start falling simultaneously from same ANTIPODEAN altitude in the absence of all other gravitational attraction including atmosphere.

So what would be the direction of accelaration of earth?

If net accelaration of Earth is zero in aforementioned scenario then would gravity "g" of two equal spherical spheres/ planets cancel each other if placed on each other?

Two points that are antipodal to one another are connected by a straight line running through the centre of the Earth. China and Argentina are one example of antipodal points. So, if you would please explain what "ANTIPODIAN altitude" means it would help me understand what you are asking. Thank you. By the way, it is spelled "acceleration"
 
:frown:Let A and B are anitipodal points.

Assume

An apple is dropped from a height of h = 100 feet above ground level [point A]

An apple is dropped from a height of h = 100 feet above ground level [point B]
 
zarmewa said:
Galileo was first to demonstrate that all objects fall at the same rate in the absence of an atmosphere. As it is said that the Earth and the Apple fall toward each other but apple looks a lot to falls to the Earth as compared to the falling of Earth toward the Apple which is so tiny to be detected.

Galileo was not demonstrating that an apple falls toward the Earth at the same rate that the Earth falls toward an apple.

Galileo was demonstrating that two objects (both of insignificant mass compared to Earth), both falling toward Earth, fall at the same rate.

zarmewa said:
Let's imagine Earth is a homogeneous sphere and two identical apples start falling simultaneously from same ANTIPODEAN altitude in the absence of all other gravitational attraction including atmosphere.So what would be the direction of accelaration of earth?
Zero. What does this have to do with the first part of your post?

You are conflating two separate scenarios.

zarmewa said:
If net accelaration of Earth is zero in aforementioned scenario then would gravity "g" of two equal spherical spheres/ planets cancel each other if placed on each other?
What do you mean by "cancel each other out"? They are still pulled toward each other with a significant force.

Regardless of the mass of the two (or even three) objects, the centre of mass of the two (or three) body system will have an acceleration of zero (i.e. the CoM will not move). What does this have to do with Galileo's discovery?
 
Last edited:
I do not have a good working knowledge of physics yet. I tried to piece this together but after researching this, I couldn’t figure out the correct laws of physics to combine to develop a formula to answer this question. Ex. 1 - A moving object impacts a static object at a constant velocity. Ex. 2 - A moving object impacts a static object at the same velocity but is accelerating at the moment of impact. Assuming the mass of the objects is the same and the velocity at the moment of impact...

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