Exploring the Physics of Energy: Can it Displace Bodies?

In summary, the conversation discusses the concept of energy and its relation to motion. The participants mention that energy is often considered abstract, but it can be quantified in terms of an object's ability to displace other objects. However, there is no clear consensus on what causes motion, with some suggesting energy and others suggesting momentum or force. The conversation suggests that further clarification and understanding of these concepts is needed for the paper.
  • #1
susskind99
24
0
If you see any mistakes in the following please let me know. This is for a paper.

We often say that energy is abstract but it is certainly less abstract than say velocity or pressure by virtue of the fact that it seems to cause particles or bodies to displace other bodies. Undoubtedly particles move and they also have an ability to displace other particles or bodies. This ability to displace bodies can be quantified in terms of energy. Whatever it is that causes bodies to move, then energy is the best candidate. We certainly wouldn't say that velocity causes bodies to move or pressure but ultimately we have to give a name to that cause that causes bodies to move and energy it seems is the best name for that cause.
 
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  • #2
Welcome to PF;
susskind99 said:
If you see any mistakes in the following please let me know. This is for a paper.
... that you are writing on some unspecified topic, for some unsecified course or other at some unspecified level?
It is difficult to see how to read this without that information.

"We [who?] often say that energy is abstract but it is certainly less abstract than say velocity or pressure by virtue of the fact that it seems to cause particles or bodies to displace other bodies.

Undoubtedly particles move and they also have an ability to displace other particles or bodies. This ability to displace bodies can be quantified in terms of energy.

Whatever it is that causes bodies to move, then energy is the best[?] candidate. We certainly wouldn't say that velocity causes bodies to move or pressure but ultimately we have to give a name to that cause that causes bodies to move and energy it seems is the best name for that cause."

What about "momentum"?
What about "force"?
 
  • #3
Simon Bridge said:
What about "momentum"?
Not sure about momentum. Feel free to provide any thoughts.

What about "force"?

I was listening to a lecture from the teaching company about physics and the prof said: a lot of people think force causes things to move. no, no, no, a 1000 times no, force causes bodies to change direction.
 
  • #4
In Newtonian mechanics - a force causes an acceleration - which may be a change in speed and/or direction.
There is no absolute for velocity - you can only have a constant velocity in relation to something else.
The cause of relative motion is acceleration - what caused the acceleration.

motion has a directional quality that is absent from energy but is present in momentum ... so I think you have more work to do there in terms of what counts as "best".

However - you have not supplied the missing information.
 
  • #5
I was listening to a lecture from the teaching company about physics and the prof said: a lot of people think force causes things to move. no, no, no, a 1000 times no, force causes bodies to change direction.

Are you sure the last word wasn't velocity rather than direction?
 
  • #6
How about we try to figure out what is the best name for that thing that causes motion.
 
  • #7
CWatters said:
Are you sure the last word wasn't velocity rather than direction?

Pretty sure.
 
  • #8
I'm not sure why someone would call that which moves objects energy rather than momentum.
 
  • #9
susskind99 said:
How about we try to figure out what is the best name for that thing that causes motion.
First tell me how you would recognize the cause of motion and then we can figure out what best to call it.

susskind99 said:
CWatters said:
Are you sure the last word wasn't velocity rather than direction?
Pretty sure.
Check. Force changes velocity - which does not have to involve a change in direction.

susskind99 said:
I'm not sure why someone would call that which moves objects energy rather than momentum.
You appear to be supporting that idea in post #1.

Anyway - if I push a wagon, then am I not the cause of the motion?
Am I not "that which moves" the wagon? Am I energy? Am I momentum?

Anyway - I believe your questions have been answered.

I suspect the paper will be marked on how you understand the words you are using.
You can improve your paper by addressing the 4 areas raised in post #2 ... and cleaning up your terminology.
 
  • #10
Simon Bridge said:
First tell me how you would recognize the cause of motion and then we can figure out what best to call it.
I would call motion when an atom is found between points A and B at time T1 and is then found between points C and D at time T2. I still don't know what name to give to that thing which causes this motion.
 
  • #11
susskind99 said:
I would call motion when an atom is found between points A and B at time T1 and is then found between points C and D at time T2. I still don't know what name to give to that thing which causes this motion.
That is because, although you have said how you would identify motion, you have not said how you would identify the cause if that motion.

If an object is in different positions at different times we would usually say that motion has occurred. We can use the statistical uncertainty on the measurements of position and statistical hypothesis testing to determine when the positions are different. Something like that ... the exact definition will depend n the model we are using.

But I want you to concentrate on the difference between the motion itself and the cause of the motion.

Using what you wrote: what causes an atom found between points A and B at time T1 to be found between points C and D at time T2?

What is it about a "cause of motion" that allows you to identify it as such?
 
  • #12
Simon Bridge said:
Using what you wrote: what causes an atom found between points A and B at time T1 to be found between points C and D at time T2? What is it about a "cause of motion" that allows you to identify it as such?

It is for this exact reason that I'm here. If I knew the answer to that I would not have posted the question. To my mind, atoms are in perpetual motion. Now what name do we give to that cause? Energy? Momentum? I don't know.
 
  • #13
susskind99 said:
It is for this exact reason that I'm here. If I knew the answer to that I would not have posted the question. To my mind, atoms are in perpetual motion. Now what name do we give to that cause? Energy? Momentum? I don't know.

Your question in post #1 was:
If you see any mistakes in the following please let me know.
... now it seems your question was "what is the cause of motion?"

In order to answer that question, I need you to define your terms: what do you mean by "cause"?
If you don't know how you would tell what a cause of something is, then the question has no meaning and cannot be answered.

But since you are asking me then: if I push a cart, then I am the cause of the motion.
There's your definition ... momentum, energy, etc are more ways to describe the motion or how motion can change.

You may also want to look at:
http://en.wikipedia.org/wiki/Causality
 
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  • #14
Simon Bridge said:
Your question in post #1 was: ... now it seems your question was "what is the cause of motion?"

In order to answer that question, I need you to define your terms: what do you mean by "cause"?
If you don't know how you would tell what a cause of something is, then the question has no meaning and cannot be answered.

But since you are asking me then: if I push a cart, then I am the cause of the motion.
There's your definition ... momentum, energy, etc are more ways to describe the motion or how motion can change.

I agree that you are the cause of the motion of the cart, but I still would like to know what is the cause of atoms moving? What name do we give that cause? Do physicists not have a name for this?
 
  • #15
susskind99 said:
I agree that you are the cause of the motion of the cart, but I still would like to know what is the cause of atoms moving? What name do we give that cause? Do physicists not have a name for this?
If I push on an atom, then I am the cause of the atom's motion.
The general name for the cause of something is "the cause". There are many possible causes depending on the situation. Did you have a specific situation in mind?
 
  • #16
Simon Bridge said:
If I push on an atom, then I am the cause of the atom's motion.
The general name for the cause of something is "the cause". There are many possible causes depending on the situation. Did you have a specific situation in mind?

Let's get down to the quark level. Would you say that the cause of the motion of a quark during the first few thousand years after the BB was the BB itself?
 
  • #17
It seems that you want a one word answer to the question "what is the cause of motion", when there is no such thing in most cases. Let me give you an example of what I mean. Suppose you have a particle on a hill and you give it a push with instantaneous force F. Well the particle will roll down the hill. What is the cause of the particles motion? Was it the initial force F? Was it the potential energy of the particle that had completely transformed into kinetic energy by the bottom of the hill? You cannot simply identify a single cause for the motion, that's why we have classical mechanics to help us describe motion in many different situations.
 
  • #18
susskind99 said:
Let's get down to the quark level. Would you say that the cause of the motion of a quark during the first few thousand years after the BB was the BB itself?
No - I wouldn't.

In a deterministic and fully causal Grand-Unified Theory of Everything, the Ultimate Cause of everything is the Start of the Universe (or there is no start but that's a different argument).

We don't have one of these ... and it does not look like a GUToE will be deterministic or purely causal.

At the quantum level, where you are asking your question, causality is tricky to pin down - is the decay of an atom caused by something? What? So it may well be that some of the quark/gluon interactions that occurred in such a busy time-frame from the Start of Everything are not well described in terms of being "caused" by anything. Sometimes stuff just happens.

I believe the wikipedia article on causality I linked to covers this adequately enough for your question ... see "causality in physics". Do read the links that appear in answers, we put them there is save typing.

Note: Questions about chains of causality and ultimate cause tend to come from people interested in making a case for the Cosmological Argument.
 
  • #19
So what you seem to be saying is that there is not a general name that physicists give to that thing that causes motion. I thought it was energy. But you seem to be saying that energy is an abstract property particles have that can be used to predict other properties that the particle will have. Energy is not a cause it is a description of how much work a particle can do. The cause of particles moving, such as beta decay, is not known.
 
  • #20
I am trying to tell you that there is no single cause for the various motions we see about us that would warrant giving it a special name. Each of the causes has a name - in my example the cause is me and I have a name, "beta decay" would be the name for the cause of a beta ray, and so on.

[edit - for clarification]
But beta decay itself is a random event caused by instabilities in the nucleus ... but, a decay having happened, there is no reason for that decay to happen at the particular time it did except that there is no reason it shouldn't happen then either. In that sense, the decay time has no cause.

A "cause" a role something plays, not a thing to be named.
 
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  • #21
susskind99 said:
I would call motion when an atom is found between points A and B at time T1 and is then found between points C and D at time T2. I still don't know what name to give to that thing which causes this motion.

If that is the definition of motion then in some situations nothing at all is needed to cause motion.
 

1. What is the physics behind energy displacement?

The concept of energy displacement in physics is based on the principle of conservation of energy. This principle states that energy cannot be created or destroyed, but it can be transferred or converted from one form to another. In the case of energy displacement, the energy of one body is transferred to another body, causing a displacement in its position or movement.

2. Can energy displacement be observed in everyday life?

Yes, energy displacement can be observed in many everyday situations. For example, when a person jumps off a diving board, their potential energy is converted into kinetic energy, causing them to displace the water they land in. Another example is the movement of a car, where the chemical energy in the fuel is converted into mechanical energy, causing the car to displace its position.

3. How does energy displacement relate to Newton's Laws of Motion?

Energy displacement is closely related to Newton's Laws of Motion, specifically the first and second laws. The first law states that an object will remain at rest or in motion unless acted upon by an external force. In the case of energy displacement, the transfer of energy from one body to another acts as the external force, causing a displacement in the object's motion. The second law states that the acceleration of an object is directly proportional to the net force acting on it. In the case of energy displacement, the greater the amount of energy transferred, the greater the displacement of the object.

4. Is energy displacement only possible with mechanical energy?

No, energy displacement can occur with various forms of energy, including thermal, electromagnetic, and nuclear energy. For example, the Sun's energy is converted into electromagnetic radiation, which can displace objects in its path. Nuclear energy, such as in a nuclear explosion, can also cause displacement of objects due to the release of large amounts of energy.

5. How does the concept of energy displacement impact renewable energy sources?

The concept of energy displacement is essential in the development and use of renewable energy sources. Renewable energy sources, such as solar and wind energy, rely on the conversion of one form of energy (i.e., solar radiation or wind) into another form of energy (i.e., electricity). This conversion involves energy displacement, where the energy from the renewable source displaces the need for non-renewable sources, such as fossil fuels. This helps reduce our carbon footprint and promotes a more sustainable energy future.

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