# Gravitational Energy: Infinite Potential & Its Impact on Nature

• pprajwal
In summary, forces in nature have a limited value and their effect is reduced when many objects are influenced by them. This can be seen in the example of magnetic force being greater for a single iron nail compared to two nails in the same field. However, this principle does not apply to gravity, as adding more people to the Earth actually increases the gravitational force. Additionally, the potential energy for both gravitation and electromagnetism is finite for non-point masses, making the concept of infinite potential energy irrelevant. Ultimately, the number of people on Earth does not significantly impact the gravitational force on an individual, as it is a complete non-issue.
pprajwal
In nature, all forces have a limited value, i.e, their effect is reduced if many objects are influenced by that force. Example, the magnetic force experienced by a single iron nail (in a magnetic field) is greater than that of 2 iron nails in the same field.

Consider gravity,
gravity exerts a force that is related to our mass. Now, on Earth, there are millions of people but everyone experiences the same force even if there are billions or trillions. That means, gravity has infinite potential.
How is this possible?

Prajwal

pprajwal said:
In nature, all forces have a limited value, i.e, their effect is reduced if many objects are influenced by that force.
Example, the magnetic force experienced by a single iron nail (in a magnetic field) is greater than that of 2 iron nails in the same field.

I'm not sure this is correct. I can see it if you put the nails end to end so that one is further away from the magnet, but not if they are placed at the same distance.

Consider gravity,
gravity exerts a force that is related to our mass. Now, on Earth, there are millions of people but everyone experiences the same force even if there are billions or trillions. That means, gravity has infinite potential.
How is this possible?

Prajwal

The electromagnetic force is not the same as gravitation. The EM force has two charges which complicates things. For example, you can "screen" a positively charged particle from the electric field of a negatively charged particle by having another positively charged particle between them. That's why you can have objects which are electrically neutral. This is not possible with gravitation.

In gravitation there is only one "charge" and it is only attractive. It cannot be screened like the EM force can. So adding people onto the Earth will actually ADD to the gravitational force, not reduce it.

In addition, the gravitational potential energy for anyone object is never infinite. You can boost an object from the surface of the Earth to infinity by accelerating it to escape velocity. For the Earth, this velocity is equal to about 25,000 mph.

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pprajwal said:
Now, on Earth, there are millions of people but everyone experiences the same force even if there are billions or trillions. That means, gravity has infinite potential.
How is this possible?
The Earth's potential is finite. You only get an infinite potential for a classical point mass, and Earth is not a point mass.

Also, this is the same for electromagnetism. A classical point charge has an infinite potential also, and a non-point charge has a finite potential.

Luckily, classical point sources do not exist.

DaleSpam said:
The Earth's potential is finite. You only get an infinite potential for a classical point mass, and Earth is not a point mass.

Also, this is the same for electromagnetism. A classical point charge has an infinite potential also, and a non-point charge has a finite potential.

Luckily, classical point sources do not exist.

I do not understand the point of Earth not being a point mass. I mean, how does a point mass and Earth differ in action of gravity (wrt the question).

And, by saying that Earth's potential is finite, do you mean that for every baby born, the gravitational force on me decreases by infinitely small amount?

pprajwal said:
do you mean that for every baby born, the gravitational force on me decreases by infinitely small amount?
If the babies immediately crawl away from you.

pprajwal said:
I do not understand the point of Earth not being a point mass. I mean, how does a point mass and Earth differ in action of gravity (wrt the question).
The potential energy density of a gravitational field is given by ##u=-\frac{|\mathbf{g}|}{8\pi G}##. If you evaluate that for a uniform spherical ball then you get
$$U=\int u\;dV = -\frac{3GM^2}{5R}$$

Where G is the universal gravitational constant, M is the mass of the ball, and R is the radius of the ball. This number is finite for R>0, and infinite for R=0 (a point mass). Therefore the Earth's gravitational potential energy is finite but the gravitational potential energy of a point mass is not.

pprajwal said:
And, by saying that Earth's potential is finite, do you mean that for every baby born, the gravitational force on me decreases by infinitely small amount?
Yes. The mass of the Earth goes down and therefore its gravitational potential energy goes down. However, the baby also has a gravitational force and the baby's gravitational potential energy goes up by the same amount that the Earth's potential energy goes down since the baby's mass is the same as the mass removed from the earth. So it really is a complete non-issue.

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1 person
pprajwal said:
In nature, all forces have a limited value, i.e, their effect is reduced if many objects are influenced by that force.

Right there is your mistake. That's just not true.

pprajwal said:
And, by saying that Earth's potential is finite, do you mean that for every baby born, the gravitational force on me decreases by infinitely small amount?
For every baby that is born and then taken away by aliens to the distant mothership, gravity decreases. Otherwise a new born baby is just a rearrangement of existing matter.

AM

dauto said:
Right there is your mistake. That's just not true.
I think the OP has in mind a mechanical force. I apply a force F to a mass m, and get acceleration a but if I apply it to 2m I get a/2 for acceleration.

For gravitational and electromagnetic fields, the force is different because the magnitude of the force is proportional not only to the field but to the magnitude of the mass or charge of the bodies in that field: F = mg or F = qE.

AM

The OP seems to think that more people being born should reduce Earth's effect on me just like more guests coming in means less soup for me. It doesn't work that way.

## 1. What is gravitational energy?

Gravitational energy is a form of potential energy that is associated with the gravitational force between objects. It is the energy that an object possesses due to its position in a gravitational field.

## 2. How does gravitational energy impact nature?

Gravitational energy plays a crucial role in the formation and movement of objects in the universe. It is responsible for the formation of stars, planets, and galaxies. It also determines the orbits of celestial bodies and is a key factor in the laws of motion.

## 3. Is gravitational energy infinite?

According to the theory of general relativity, gravitational energy is infinite. This means that there is no upper limit to the amount of gravitational energy that can be present in a system. However, in practical applications, gravitational energy is limited by the size and mass of the objects involved.

## 4. Can gravitational energy be harnessed as a source of energy?

Currently, there are no known ways to directly harness gravitational energy as a source of energy. However, in the future, it may be possible to use gravitational energy in the form of tidal or orbital energy to generate electricity.

## 5. How is gravitational energy related to other forms of energy?

Gravitational energy can be converted into other forms of energy, such as kinetic energy or thermal energy. For example, when an object falls towards the Earth, its gravitational energy is converted into kinetic energy. Also, the potential energy stored in a hydroelectric dam is converted into electrical energy as the water falls and turns the turbines.

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