# What is energy?



## Unicorntopia (Jun 18, 2010)

Ok, I know it is heat and anything with a temperature above absolute zero has it, but it just really bothers me that it is invisible. I am comfortable with matter because I can picture it and you can pick it up and do stuff with it, but energy just seems wierd to me. 

On top of all that, supposedly matter is not even "solid," as in, if you were small enough you could fit yourself bewteen the different particles of what make up these things. They keep finding that if you look even closer than that, you can see that there are even smaller things that make up those things that you were just between, and you could shrink to fit inbetween those as well. So far, this just keeps going and going. 

So, basically this tells me we have yet to find anything "solid" at all. Its like all we have are borders within borders within borders to infinity. And, then they say that there is dark matter that lies in all the between spaces but we can't see that supposedly. 

So, we have two invisible things, one is dark matter and one is energy. We also have light matter that we can supposedly see but to me it seems just as invisible as the other two since there is infinite "space," which we now call dark matter in between all the little "separations," inside of it, and all of these move around in relation to one another. All of this, when there is supposedly no space to move through, only more and more matter that is packed with more and more matter, going light then dark then light then dark, to infinity outwards and inwards. 

So, I guess my real question is, is there any such thing as matter or energy, or is it just infinity immaginary separations gliding around one another or something alone those lines? 

Can anyone say anything to make me feel a little more secure that any of this actually exist anywhere close to how we think we understand it today?

Am I missing something? I must be missing something. None of this makes any sense to me. I appologize if I have just overlooked something simple this entire time I have been alive. Pretty, pretty, please tell me it if you know it. 

Thanks.


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## Psychosmurf (Aug 22, 2010)

Unicorntopia said:


> Ok, I know it is heat and anything with a temperature above absolute zero has it, but it just really bothers me that it is invisible. I am comfortable with matter because I can picture it and you can pick it up and do stuff with it, but energy just seems wierd to me.


I just picture energy as a sort of "fluid" which can pass from one object to another. Maybe that helps.



> On top of all that, supposedly matter is not even "solid," as in, if you were small enough you could fit yourself bewteen the different particles of what make up these things. They keep finding that if you look even closer than that, you can see that there are even smaller things that make up those things that you were just between, and you could shrink to fit inbetween those as well. So far, this just keeps going and going.


Although it is true that most of what we think of as solid matter is simply empty space, the composition of matter is not infinitely complex. Eventually, you get to a set of particles so small, that they don't have a measurable size. Therefore, there can be no smaller particles. These particles are called _elementary particles_ and they include leptons (i.e. electrons, muons, tauons, and neutrinos), quarks, and intermediate bosons (i.e. photons, W-bosons, Z-bosons, and gluons).



> So, I guess my real question is, is there any such thing as matter or energy, or is it just infinity immaginary separations gliding around one another or something alone those lines?


There are such things as matter and energy. But the distinction between them starts to break down at planck scales.



> Can anyone say anything to make me feel a little more secure that any of this actually exist anywhere close to how we think we understand it today?


The reason we think that all of these strange things exist the way they do is because these are concepts that are used in modern physical theories. From these concepts we can form mathematical models of the world to make predictions. These predictions are then tested to see if they match reality.

So far, the theories have worked extraordinarily well. In fact, General Relativity and Quantum Mechanics are the most well-supported theories in scientific history.



> Thanks.


You're welcome! roud:


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## Unicorntopia (Jun 18, 2010)

Psychosmurf said:


> I just picture energy as a sort of "fluid" which can pass from one object to another. Maybe that helps.


Yeah, yeah ,yeah that is the only way I can even remotely try to accept it. Even though... that is your immagination!!! :tongue:



Psychosmurf said:


> Although it is true that most of what we think of as solid matter is simply empty space, the composition of matter is not infinitely complex. *Eventually, you get to a set of particles so small, that they don't have a measurable size.* Therefore, there can be no smaller particles. These particles are called _elementary particles_ and they include leptons (i.e. electrons, muons, tauons, and neutrinos), quarks, and intermediate bosons (i.e. photons, W-bosons, Z-bosons, and gluons).


So we think! What?! You have not seen the trend? Give it some time Psychosmurf, and you will see there is a like 99% probability that we just keep going and going finding smaller things!



Psychosmurf said:


> There are such things as matter and energy. But the distinction between them starts to break down at planck scales.


Ahh, my suspicions mildy supported...





Psychosmurf said:


> The reason we think that all of these strange things exist the way they do is because these are concepts that are used in modern physical theories. From these concepts we can form mathematical models of the world to make predictions. These predictions are then tested to see if they match reality.
> 
> So far, the theories have worked extraordinarily well. In fact, General Relativity and Quantum Mechanics are the most well-supported theories in scientific history.


We need to find something better. I will expect you to have figured it out in twenty years. :bored: The clock is officially ticking as of now. :tongue:





Psychosmurf said:


> You're welcome! roud:


*bows and tips hat*


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## Psychosmurf (Aug 22, 2010)

Unicorntopia said:


> Yeah, yeah ,yeah that is the only way I can even remotely try to accept it. Even though... that is your immagination!!! :tongue:


Hmmm.... I think I've just thought of a better way to think about it. Think of energy as the amount of change in a system per unit time. So, for example, an explosion is a _very_ large amount of change in a very short amount of time, so the energy in that system is very high. A rusting nail is a small amount of change over a very long time, so the energy in that system is very low.




> So we think! What?! You have not seen the trend? Give it some time Psychosmurf, and you will see there is a like 99% probability that we just keep going and going finding smaller things!


I think I should make the idea of elementary particles clearer. 

There are two kinds of quantum particles, composite and elementary. To each particle is associated a compton wavelength and the wavelength that the particle currently has. If a particle has a wavelength larger than its own compton wavelength, then it is said to be composite. If a particle has a wavelength that is smaller than its own compton wavelength, then it is said to be elementary. Now, the sizes of the composite particles can be easily measured by comparing them to the sizes of other composite particles. But elementary particles don't have _any_ measurable size. They're not small, and they're not large. 

Now, the tools that we have used in the past to measure sizes had designs that were informed by the physical theories of the time. Those theories did not have particles that do not have a measurable size, so they always said that we can make size measurements ever more precise. And that trend continued, until today. Now, the best theories we have say that elementary particles are the end of the line. These theories will be used to inform the designs of modern measuring devices. And if the best theories say that measurements smaller than some amount are impossible, it therefore follows that we cannot make measuring devices that can measure anything smaller than said amount.



> We need to find something better. I will expect you to have figured it out in twenty years. :bored: The clock is officially ticking as of now. :tongue:


This is true. The theories we currently have break down in certain situations.


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## Bote (Jun 16, 2010)

@Unicorntopia 

Yeah all that we can observe and measure in the Universe is 99.999% empty space. And that 'empty space' is made of probabilistic fluctuation where quantums of energy pop in and out of existence. Totally confusing I agree.


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## Unicorntopia (Jun 18, 2010)

Psychosmurf said:


> Hmmm.... I think I've just thought of a better way to think about it. Think of energy as the amount of change in a system per unit time. So, for example, an explosion is a _very_ large amount of change in a very short amount of time, so the energy in that system is very high. A rusting nail is a small amount of change over a very long time, so the energy in that system is very low.


Interesting, so now you are saying that energy is movement/change, which you could aslo say is creation or destruction. This is very helpfull because it takes away the thought that it is "something" like matter is something. I was trying to make it be something in my mind that I could pin point, visualize and carry from one thing to another. It still bothers me that still things can have potential energy if the definition is change over time. Things like fat in the body have stored energy, but are not changing or moving while having energy. Is potential energy nothing more than us predicting how much energy it will have in the future based on what we have seen things situated just so in the universe do in the past? This would make me think that said thing with potential energy would not have "energy" (other than what it needs to exist in its relatively still state) until the point in time that it makes that big move. Then my question is where was the energy hiding while the energy of said thing is potential? 



Psychosmurf said:


> I think I should make the idea of elementary particles clearer.
> 
> There are two kinds of quantum particles, composite and elementary. To each particle is associated a compton wavelength and the wavelength that the particle currently has. If a particle has a wavelength larger than its own compton wavelength, then it is said to be composite. If a particle has a wavelength that is smaller than its own compton wavelength, then it is said to be elementary. Now, the sizes of the composite particles can be easily measured by comparing them to the sizes of other composite particles. But elementary particles don't have _any_ measurable size. They're not small, and they're not large.


Are you saying that we can see things moving but cannot see the boundaries of these things? How can we see something moving if we cannot see it? Ex. If you see a black wall that goes in all directions but is moving, you cannot see it move because you cannot see the edges of it move closer or further from another thing that may or may not be beside it. 





Psychosmurf said:


> Now, the tools that we have used in the past to measure sizes had designs that were informed by the physical theories of the time. Those theories did not have particles that do not have a measurable size, so they always said that we can make size measurements ever more precise. And that trend continued, until today. Now, the best theories we have say that elementary particles are the end of the line. These theories will be used to inform the designs of modern measuring devices. And if the best theories say that measurements smaller than some amount are impossible, it therefore follows that we cannot make measuring devices that can measure anything smaller than said amount.
> 
> 
> 
> This is true. The theories we currently have break down in certain situations.





Bote said:


> @Unicorntopia
> 
> Yeah all that we can observe and measure in the Universe is 99.999% empty space. And that 'empty space' is made of probabilistic fluctuation where quantums of energy pop in and out of existence. Totally confusing I agree.


So, is space dark matter? And, if it does not have measurable size and pops in and out of existance, could that mean that "it" is what is "moving" or should I say "pushing" measurable matter around? 

Maybe there is no energy at all. Maybe the poping in and out of existant stuff scooting us closer and further apart as it pops in and out of between us? If we do indeed have the power to create and it is not just fate, maybe that means we have at least some control over these poping in and out of existant things.


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## Psychosmurf (Aug 22, 2010)

> Interesting, so now you are saying that energy is movement/change, which you could aslo say is creation or destruction. This is very helpfull because it takes away the thought that it is "something" like matter is something. I was trying to make it be something in my mind that I could pin point, visualize and carry from one thing to another. It still bothers me that still things can have potential energy if the definition is change over time. Things like fat in the body have stored energy, but are not changing or moving while having energy. Is potential energy nothing more than us predicting how much energy it will have in the future based on what we have seen things situated just so in the universe do in the past? This would make me think that said thing with potential energy would not have "energy" (other than what it needs to exist in its relatively still state) until the point in time that it makes that big move. Then my question is where was the energy hiding while the energy of said thing is potential?


Energy actually is "something" just like mass. The idea I came up with (I should be more clear with these things) was for _visualizing_ changes in energy. The fat stored in the body has almost no change in its energy over a wide range of durations, so therefore the physical action (i.e. amount of change in the system) is very small.

The potential energy is just as real as kinetic energy. The potential energy that an object has is really due to the potential field around it. A field is a potential only if it depends on the position variable. 

Let's look at an example of a system with lots of potential energy. Imagine a ball gets shot out of a cannon high into the atmosphere. Initially, it has lots of kinetic energy, but then it reaches a peak. At this point it has zero kinetic energy and lots of potential energy. The potential energy comes from a nearby potential field. In this case, it is the Earth's gravitational field. It exerts a downward force on the ball at all times and only really changes with distance from the earth's surface. The potential energy was never actually "in" the ball.

With the body fat, the potential energy is stored in the bonds between the Carbon and hydrogen atoms in the carbohydrates that fat cells contain. When the fat is metabolized it breaks these bonds and the potential energy is transformed into kinetic energy that the body can use directly.



> Are you saying that we can see things moving but cannot see the boundaries of these things? How can we see something moving if we cannot see it? Ex. If you see a black wall that goes in all directions but is moving, you cannot see it move because you cannot see the edges of it move closer or further from another thing that may or may not be beside it.


You don't have to be able to see the boundary of something in order to know that it is moving. Clouds illustrate this idea quite well.

An excellent test to check if an example of motion is real or an illusion is that real motion can always be used to put other things into motion. Optical illusions can't. roud:



> So, is space dark matter? And, if it does not have measurable size and pops in and out of existance, could that mean that "it" is what is "moving" or should I say "pushing" measurable matter around?


No one actually knows what dark matter is.


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## Psychosmurf (Aug 22, 2010)

Actually this has gotten me thinking about writing up a precise explanation of what energy actually is. It'll be an excellent excuse to look into Hamiltonian mechanics, since I was too lazy to learn it before. :tongue:


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## bigtex1989 (Feb 7, 2011)

So @Psychosmurf had a pretty interesting idea by saying energy ds/dt (change in states over time), although, maybe we can do a bit better, as this has nothing to do with potential energy or any of those things. *crosses fingers* let's dive in!

So to understand energy, I think it is imperative to understand what work is. Rudimentary definitions are available everywhere, but a nice concise mathematical one exists: 

dW = Fdx

or, the change in work equals the force exerted times the displacement. It seems simple enough, although there are many interesting subtleties that exist that have almost no bearing on our discussion of energy.

There are many types of work however, mechanical work, chemical work, etc. The addition of these types of work don't really effect a nice intuitive understanding of what energy is, although they do change the math and models and stuff.

Considering only mechanical work, dE = W. What does that tell us? That the change in energy is equal to the amount of work! There is a definition right there. Energy of a system is the capacity a system has to perform work on another system. Phew. However, that doesn't really help in knowing what energy is.

For this example, money = energy. Consider a very rich man. He has the ability to buy anything he wants in this example. He is the richest man on the planet. He can pay any fine, any ticket, post any bail. He can buy justice. He can literally do whatever he wants. He has nearly infinite money, so he can do anything, even defy laws. But, as he pays for more things, he loses money until he becomes broke, provided he has no income. On the other end, a person with no money can't do anything, or at least do very limited things. 

It is also theorized with infinite energy, you can do anything XD. With no energy you can do nothing.

Energy is a fundamental quantity, it is dissimilar to mass in this way. Mass is a collection of smaller masses, and all the way down (although there must be a limit, as there is no such thing as an infinite series physically) until you can definite it as physical matter that we can observe, where as energy is, well energy!

Hope this helps!


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## Unicorntopia (Jun 18, 2010)

I thought I had changed the totle of this thread from "Gravity & diffusion" to "What is Energy" but I gues it did not work. I had originally asked a different question but then realized something that made me change my mind. Sorry if anyone was confused by the title.

@Happy Is it possible to have the title of this thread changed to"What is Energy?"


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## Psychosmurf (Aug 22, 2010)

This may not be the place to say this, but is it just me or has the font of the posts changed? Seems a bit bigger than normal... :mellow:

EDIT: Crap never mind. It was just me.


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## Unicorntopia (Jun 18, 2010)

Psychosmurf said:


> This may not be the place to say this, but is it just me or has the font of the posts changed? Seems a bit bigger than normal... :mellow:
> 
> EDIT: Crap never mind. It was just me.


Oh no, that was me. My brain just has that grand of an effect on you. :tongue: I will try to tone it down a little bit. :wink:


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## Vtile (Feb 27, 2011)

bigtex1989 said:


> ....
> For this example, money = energy. Consider a very rich man. He has the ability to buy anything he wants in this example. He is the richest man on the planet. He can pay any fine, any ticket, post any bail. He can buy justice. He can literally do whatever he wants. He has nearly infinite money, so he can do anything, even defy laws. But, as he pays for more things, he loses money until he becomes broke, provided he has no income. On the other end, a person with no money can't do anything, or at least do very limited things.
> ...
> Hope this helps!


 Should this continue that in the end those persons with no money got the money of the rich and can do things with it. :mellow: 

- But which currency he/she have and because the time is money isn't this descriping something more like J*s :crazy:


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## bigtex1989 (Feb 7, 2011)

Vtile said:


> Should this continue that in the end those persons with no money got the money of the rich and can do things with it. :mellow:
> 
> - But which currency he/she have and because the time is money isn't this descriping something more like J*s :crazy:


I think you're reading too much into it! It is merely a model after all XD


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## DouglasMl (Nov 3, 2009)

In support of remarks by bigtex1989:

From my university days, I always remembered the equivalence of work, energy, and heat (J. P. Joule's famous experiment with falling weights, an agitator turned by the weights, a supply of water, and a thermometer to measure the heat generated; the metric unit of energy is still called a _Joule _in honour of Joule's work). By _work_, I mean what physicists would mean: force applied over a distance or torque applied through an angle.


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## Just_Some_Guy (Oct 8, 2009)

I think it is first important to make it explicitly clear that common sense and Newtonian thinking will not help understand this problem. 

The best example I can think of is that energy only exists between bits of matter. Perhaps like the old gestalt of the two faces and the vase. If you're looking for "things" you'll see faces and the energy (vase) disappears. I've even gone so far as to postulate that photons are 4d standing waves that instantaneously transmit energy and that space and time are strange results of movement (more energy). I'm pretty sure I'm right, but I have absolutely no way to intelligently postulate the idea or test it. Oh well.


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## Inphamous (May 10, 2011)

EmotionallyTonedGeometry said:


> I think it is first important to make it explicitly clear that common sense and Newtonian thinking will not help understand this problem.
> 
> The best example I can think of is that energy only exists between bits of matter. Perhaps like the old gestalt of the two faces and the vase. If you're looking for "things" you'll see faces and the energy (vase) disappears. I've even gone so far as to postulate that photons are 4d standing waves that instantaneously transmit energy and that space and time are strange results of movement (more energy). I'm pretty sure I'm right, but I have absolutely no way to intelligently postulate the idea or test it. Oh well.



I'm far from a physicist but I seem to remember reading something while I was looking up things reguarding super string theory about matter and / or light being circular standing waves in a higher non-euclidean geometrical dimention.
If anyone can enlighten me farther I and probably many others would be most grateful. Thanks in advance.


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## Aegis (May 3, 2011)

The simplest definition I know is this: _Energy is the potential for a system to cause a change in its environment._

In your body, matter is stored as chemical energy for example in the chemical bonds of ATP molecules. Using a heat engine, you can potentially use internal energy in a heat engine to move other objects (perform work).


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## sprinkles (Feb 7, 2010)

I consider energy to be the potential to do work. I don't mean necessarily "useful" work, just the potential to move something, or heat it, or create light. And specifically how it effects matter.

Example, heat radiation, in itself, is probably not 'hot'. As humans we can feel 'heat' in the air, but this generally is not the heat felt from the energy, it is felt by the heat radiation from the heated air particles as well as direct radiation itself, from the sun for example, contacting your body and increasing your temperature by exciting your molecules. So the radiation is not 'heat' coming through the air, it is radiation that heats up objects it comes in contact with. Kind of like magnets, a magnet by itself doesn't do anything but if you bring it close to metal it will try to 'stick', or try to repel from another magnet. The forces cause work to be done in matter, but if there is no matter in contact, they don't do anything.


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## jameswood037 (Oct 19, 2011)

In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems.Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of a certain length.


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