Question about Gravity?

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In summary, Galileo's discovery that all objects fall at the same rate in the absence of an atmosphere applies to two objects of insignificant mass compared to Earth, regardless of their size or distance from each other. The direction of acceleration of Earth in this scenario would be zero. However, the gravity between two equal spherical objects would still exist and not cancel out completely. This is separate from Galileo's discovery and relates to the centre of mass of a system.
  • #1
zarmewa
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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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  • #2
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"
 
  • #3
: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]
 
  • #4
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?
 
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  • #5


I would like to clarify that gravity is a force that exists between any two objects with mass. The magnitude of this force depends on the masses of the objects and the distance between them. In the scenario described, the Earth and the apples have different masses, so the force of gravity between them will also be different. This is why the apple appears to fall faster towards the Earth, as it has a smaller mass and is therefore more affected by the Earth's gravitational force.

In terms of the direction of acceleration, both the Earth and the apple would be accelerating towards each other, but the Earth's larger mass means that its acceleration will be much smaller compared to the apple's.

In regards to the hypothetical scenario of two identical spheres or planets placed on top of each other, the force of gravity between them would not cancel out. In fact, the two objects would attract each other and potentially merge into one larger object. This is because the force of gravity is always present between any two objects with mass, regardless of their size or placement. I hope this clarifies any misunderstandings about the concept of gravity.
 

1. What is gravity?

Gravity is a fundamental force of nature that causes objects with mass to attract each other. It is responsible for keeping planets in orbit around the sun and objects on the Earth's surface. It is described by Sir Isaac Newton's law of universal gravitation and Albert Einstein's theory of general relativity.

2. How does gravity work?

Gravity works by the curvature of space-time caused by objects with mass. The more massive an object is, the stronger its gravitational pull. This pull is what keeps objects in orbit around each other and gives weight to objects on Earth's surface.

3. Why do objects fall towards the ground?

Objects fall towards the ground because of the Earth's gravitational pull. The Earth's mass creates a large enough curvature in space-time to attract objects towards its center. This pull is what causes objects to have weight and fall towards the ground when dropped.

4. Can gravity be manipulated?

So far, there is no known way to manipulate gravity. However, scientists are constantly researching and experimenting with the possibilities of manipulating gravity, especially in space exploration and propulsion systems.

5. How does gravity affect the universe?

Gravity plays a crucial role in the formation and evolution of the universe. It is responsible for the formation of galaxies, stars, and planets. It also affects the movement and interactions of celestial bodies, such as the orbit of planets around stars and the rotation of galaxies. Without gravity, the universe would be a much different and chaotic place.

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