Gravity & Energy: Questions on Object Acceleration & Hydrogen Cloud Collapse

In summary, the question asks about the source of extra energy when objects are affected by gravity. In the case of an object moving towards Earth, its potential energy converts to kinetic energy. Similarly, the potential energy of a hydrogen cloud in space converts to kinetic energy when it collapses into a star. This is explained by Newtonian gravity, although General Relativity may not have a definitive answer.
  • #1
BobiG
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I have a quick question, if an object is moving straight towards say Earth, isn't the gravitational field of Earth going to accelerate that object giving it extra energy? Where does that energy come from? Similar question, you have a hydrogen cloud in space, isn't the mass(energy) of that cloud less than the mass(energy) of that same cloud when it collapses into a star due to gravity? Again where does the extra energy come from? It may be a stupid question but I have to ask!
 
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  • #3
BobiG said:
I have a quick question, if an object is moving straight towards say Earth, isn't the gravitational field of Earth going to accelerate that object giving it extra energy? Where does that energy come from?
If an object "is moving straight towards say Earth", it must have been above the Earth and so has potential energy. That potential energy converts to kinetic energy.
There is no net change in energy.

Similar question, you have a hydrogen cloud in space, isn't the mass(energy) of that cloud less than the mass(energy) of that same cloud when it collapses into a star due to gravity? Again where does the extra energy come from? It may be a stupid question but I have to ask!
Similar answer- the hydrogen cloud has potential energy due to the fact the hydrogen atoms are separate. There is no net change in "mass-energy".
 
  • #4
Not a stupid question at all. I suppose everyone just goes back to Newtonian gravity to answer that one, since I don't think General Relativity has an answer to it. GR says that the object isn't gaining energy when viewed from the appropriate free-falling frame. I think that's a cop-out, because in that frame, the ground is accelerating toward you. Where does *that* energy come from?
 
  • #5


Your questions are not stupid at all! In fact, they touch upon some fundamental principles of physics that have been studied and debated for centuries.

To answer your first question, yes, the Earth's gravitational field does accelerate objects towards it. This acceleration is due to the force of gravity, which is a fundamental force of nature that exists between all objects with mass. When an object is in the Earth's gravitational field, it experiences a force towards the Earth's center, causing it to accelerate. This acceleration does give the object extra energy, which is known as gravitational potential energy. This energy comes from the work done by the gravitational force as the object moves towards the Earth.

Now, for your second question, the answer is a bit more complex. When a hydrogen cloud collapses into a star due to gravity, the mass of the cloud does not change. However, the energy of the cloud does change. This is because as the cloud collapses, its particles get closer together, which increases the cloud's density. This increase in density also increases the gravitational force between the particles, causing them to accelerate towards each other. This acceleration converts the potential energy of the cloud into kinetic energy, causing the cloud to heat up and eventually collapse into a star. So, in this case, the extra energy comes from the conversion of potential energy into kinetic energy.

It's important to note that the total energy of a system, such as a hydrogen cloud collapsing into a star, remains constant. This is known as the law of conservation of energy. So, while the energy of the cloud may change, the total energy of the system remains the same.

I hope this helps answer your questions. Keep asking questions and seeking answers – that's what science is all about!
 

1. What is gravity?

Gravity is a fundamental force that attracts objects with mass towards each other. It is responsible for the acceleration of objects towards the surface of the Earth and the motion of planets around the Sun.

2. How does gravity affect object acceleration?

Gravity is directly proportional to the mass of an object. The greater the mass, the greater the force of gravity, which results in a greater acceleration towards the source of gravity. However, gravity also decreases with distance, so the closer an object is to the source of gravity, the greater its acceleration will be.

3. What is the relationship between gravity and energy?

Gravity and energy are closely related as they both play a role in the motion of objects. Gravity is a force that can do work, which is a form of energy. As objects move in a gravitational field, they can gain or lose energy depending on their position and velocity.

4. What is the significance of hydrogen cloud collapse?

Hydrogen cloud collapse is a process in which a large cloud of hydrogen gas collapses under its own gravity, eventually forming a star. This process is significant because it is the first step in the formation of stars and galaxies, which are essential for the formation of planets and the development of life.

5. How does gravity impact the evolution of the universe?

Gravity is responsible for the formation of structures in the universe, such as galaxies, clusters of galaxies, and superclusters. These structures continue to evolve and interact due to the gravitational force between them. Without gravity, the universe would not have formed into the complex and diverse system that we see today.

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