What is energy?

[AndresKiani]

Do we know what energy is in Physics? I've thought about this for a long time, but it seems as though energy some what synonymous with motion and potential for motion. This my interpretation from my readings.

 

Potential to do work. Though what causes an object to do work? What is it within the fabrics of that object that allows it do such a thing?

 

Does this relate back to entropy and perhaps the big bang? It seems to me that energy comes from the instability of something to a more stable existence. Thus does this relate somehow to the big bang perhaps, how the general directionality of the universe is from unstable to more stable?

[swansont]

Energy is a property, and since the laws of physics don't change with time, it's a conserved quantity. That makes it useful in figuring out how things behave.

[ajb]

Do we know what energy is in Physics?

This depends on what you mean.

 

Potential to do work.

So this is the thermodynamic definition of energy; you think of energy as the property of a configuration that allows it to, or gives it the potential to 'do something'.

 

We also can understand energy as the 'conserved charge' related to time translation invariance of a system. Basically as the physics is the same at all times we have the notion of energy. This is related to Noether's theorems.

 

At best you should think of energy as a number that we can calculate given a physical configuration, this number happens to be useful, but physics does not really deal with the question of 'what is'. We just know how to use it.

[Nicholas Kang]

Though what causes an object to do work?

 

Force. Recall the formula for work done. W=Fs, whereas W=work done, F=nett force, s=displacement

 

What is it within the fabrics of that object that allows it do such a thing?

 

The fabric? I supposed you are talking about the space-time continuum. First of all, work done can be defined in many context. Work done against gravity is just one manifestation of work done. For instance, say I move a wooden block with a force of 3N across a smooth floor (with negligible friction and air resistance) for 1m, based on the formula W=Fs, my work done is 3N m, or simply 3 Joule. The wooden block and I are all on the Earth, within its gravitational influence. But recall that displacement is distance in a particular direction (of the nett force). So I push the block forward, my direction is to the right (from you view as a spectator standing right beside me) Only the distance I moved to the right will be considered, independent of Earth gravity.

 

For overcoming gravitational force, the direction of nett force is upwards, therefore, only the vertical distance is considered.

 

I would suggest you so as not to use the word fabric anymore. It is quite misleading. In fact, Einstein`s General Relativity say nothing about space-time as a fabric. Mordred, one of the members in scieceforums.net, advised us to not thinking of space-time as a fabric. he emphasizes it many times. Refer:

 

Post 16, "Space is not a fabric" http://www.scienceforums.net/topic/86180-vacuum-energy-universes-within-universes/

This is a better desrciption. Post 9, http://www.scienceforums.net/topic/83690-what-is-space/?hl=fabric

 

Does this relate back to entropy and perhaps the big bang? It seems to me that energy comes from the instability of something to a more stable existence. Thus does this relate somehow to the big bang perhaps, how the general directionality of the universe is from unstable to more stable?

 

Entropy is related to second law of thermodynamics. it is something like a measure of the complexity of the order of the universe and nature. Imagine you have a ball and a transparent empty can. You throw the ball into the can, it settled down after a while, you shake the can, it settled down after a while. Will the ball settled at the same place exactly as the previous one. It is almost impossible, though theoretically possible. Entropy increase along with time. Things become disordered after time. For Big Bang, i don`t really know what you mean. Big Bang is a too general term. You can state the exact epoch for a better explanation, e.g. First 3 Minutes etc. Some scientists proposed that Big Bang start off with a quantum fluctuation. A sudden energy surge resulting in our current universe.

 

I spent some time rereading your question. I roughly know what you are talking. you must be talking about dimesnions. Our "mother" universe is unstable in higher dimensions, so the universe "break down" into a four-dimension universe (our universe) and an unseen 6-dimension universe. The 6-dimesnion universe is too small to be observed.

 

Here is how to relate it with energy. (based on my speculation on what you had typed)

 

Imagine having a pencil positioned straight upright on a table. This is a state of balance, technically know as unstable equilibrium. This is almost impossible in real-life practice. But this is an equilibrium theoretically. The pencil will then fall onto the table to achieve neutral equilibrium. The universe is unstable in higher dimensions so it must go through quantum tunneling to lower energy state, which is 4-dimension.

 

Does the above information help? If you delve further, you may encounter Kaluza-Klein Theory, Superstring Theory etc. They have something to do with higher dimension science.

[studiot]

What is energy?

Beginners all too often get sidetracked by such questions as what is time? what is space? or what is energy?

Any technical discipline follows the pattern of resting on a number of fundamental definitions and a some propositions.
The propositions are called axioms in mathematics and principles in physics.

Whatever the discipline, they are open ended. That is they are accepted without proof and rest upon nothing else.
This does not mean to say that they are not the result of intense thought and practical investigation and also subject to revision in the light of better information.
Further we can provide descriptions to gain an intuition of where, when, why and how these are used.

Not making these basics open ended results in the sort of pointless disputes about circular arguments currently being enacted in the sister thread what is time?

It should be noted that the structure of scientific disciplines is open at both ends. That is not only in its foundations but also to allow for future development. There is always something left to be discovered.

This does not only apply to scientific disciplines.
For instance you have probably changed money to go abroad.
But what is money? What is value? what is price?
They are basic definitions in economics.

Money is not a thing in itself. It is a means to compare. A convenient container or wrapper to hold all the paraphanalia and processes associated with exchange of things.

Energy too is not a thing, it is a wrapper to hold all the paraphanalia and processes associated with certain interactions of real physical things.