Energy

[Hakomar]

Greetings dwellers of the Athenaeum,
Currently I am doing Physics for one of my GCSEs, and the class has progressed so far to energy. I still don't understand - I understand what the exam board needs me to know, but I can't get my head around the idea of energy. Is it a tangible, physical substance? Can it be observed, or only its effects? What actually is energy?
Being a very lazy person, I have had a few brief glances at Wikipedia, but for someone so scientifically illiterate as myself, it is far too esoteric. I was wondering if anyone could put it in layman terms for me?

[Jack04]

Energy can be a difficult one. Think of it as a quantifier of how much of something a system is doing (or, in the case of potential energy, can do). It is a property of an object, not something in and of itself. However, it must also be conserved when objects interact. It can be "observed" in a fashion, in that we can see how much of it is transferred to detectors when an object is stopped to judge how much of it an object had before interacting.

It is also equivalent (and transferable) to mass.

[Elfdude]

Energy for lack of a better way to describe it is simply the term given to the disassociation of negative and positive particles. Presumably at the formation of the universe negative energy and positive energy were distributed unevenly leading to a long term reordering of the universe to a stable state. Energy has the property of being able to form a variety of particles when observed in our universe. Everything and anything is energy. The small disassociation of negative and positive particles can create new particles, these particles can in turn have various effects and can continue to combine. The Higgs boson is for example one form of energy which gives mass to a particle (all particles are massless without it) etc.

Energy which is stabilized (a drastic oversimplification) is matter. Matter is formed of smaller and smaller particles which arise from energy. Energy is always net 0 in the universe however within a local environment it may be positive or negative. This is why we exist and why everything exists.

But basically you just need to understand that E=MC^2 which means that energy and matter can be converted back and forth between each other. They are two sides of the same coin, or if you prefer matter is a higher order of organization than energy.

Energy is conserved because it's best to think of it as particles or waves (or wave packets) that pass from one thing to another. When I punch the wall it absorbs the energy not by destroying the energy but by directing that energy through the wall into the environment around it until the energy produces negligble effects. Some of the energy might go into deforming the matter, some might go into heating it, some might go into friction, but the vast majority (unless you destroy the wall) is directed through the wall.

To put it another way Energy is movement. The more movement something (anything) has the more energy it has. Particles which are warmer are moving faster than particles which are colder. There's friction because the movement of your particles interacts with the movement of other particles passing off energy from yours to theirs or vice versa there's kinetic energy because on top of the natural energy of the particles themselves they are also moving relative in space which gives the energy direction.

Energy is the basis of everything. Without it nothing is just nothing and we never existed.

[Dolgorukiy]

Energy for lack of a better way to describe it is simply the term given to the disassociation of negative and positive particles. Presumably at the formation of the universe negative energy and positive energy were distributed unevenly leading to a long term reordering of the universe to a stable state. Energy has the property of being able to form a variety of particles when observed in our universe. Everything and anything is energy. The small disassociation of negative and positive particles can create new particles, these particles can in turn have various effects and can continue to combine. The Higgs boson is for example one form of energy which gives mass to a particle (all particles are massless without it) etc.

Energy which is stabilized (a drastic oversimplification) is matter. Matter is formed of smaller and smaller particles which arise from energy. Energy is always net 0 in the universe however within a local environment it may be positive or negative. This is why we exist and why everything exists.

But basically you just need to understand that E=MC^2 which means that energy and matter can be converted back and forth between each other. They are two sides of the same coin, or if you prefer matter is a higher order of organization than energy.

Energy is conserved because it's best to think of it as particles or waves (or wave packets) that pass from one thing to another. When I punch the wall it absorbs the energy not by destroying the energy but by directing that energy through the wall into the environment around it until the energy produces negligble effects. Some of the energy might go into deforming the matter, some might go into heating it, some might go into friction, but the vast majority (unless you destroy the wall) is directed through the wall.

To put it another way Energy is movement. The more movement something (anything) has the more energy it has. Particles which are warmer are moving faster than particles which are colder. There's friction because the movement of your particles interacts with the movement of other particles passing off energy from yours to theirs or vice versa there's kinetic energy because on top of the natural energy of the particles themselves they are also moving relative in space which gives the energy direction.

Energy is the basis of everything. Without it nothing is just nothing and we never existed.

There is so much wrong in here, I don't even know where to begin...

Energy, in its simplest definition is a physical property, which indicates a system's ability to perform work. Work, in its, turn is the integral of a force applied to an object over its path. For instance, If I drop a 5kg bowling ball ball from a height of 10m to the ground, the work that the force of gravity performs on it equals m*g*dh: 5*10*10 which would be about 500 joules, as the force is constant and it's applied right along the path of the ball's movement.
Roughly speaking, Energy can be categorised in two ways: Potential and Kinetic: the first refers to the system's potential to perform work, the other refers to its movement, and is closely related to momentum. In the former example, the system's potential energy at the beginning was 500 joules and the kinetic was zero. It became the opposite right before the ball hit the ground - the potential energy was zero and the kinetic 500 joules. In fact, the sum of the potential and kinetic energies at every moment of the ball's fall would be 500 joules! (Check it, the formula for the kinetic energy of an object is given by 0.5*m*v^2) This is because the force of Gravity conserves energy (i.e the work it performs on a closed loop trajectory equals zero), the energy is conserved until the ball hits the ground at which point it's met with the ground's resistance, which is not conserving, and loses all its energy, which transfers to heat and vibrations (of the ground or air).

Hope that cleared some things up for you.

[Dolgorukiy]

Energy, in its simplest definition is a physical property, which indicates a system's ability to perform work.

As for your "answer"; taking random factoids and mixing them all up in a bowl of complete BS, doesn't define Energy either. Just to point out a few glaring errors:

1. The net energy of the Universe isn't zero, otherwise there would be no Universe.
2. Concepts of Positive and Negative energies only make sense when there is a point of reference, and it can be placed arbitrarily.
3. Energy is not movement, there is that other kind too y'know.

Also this:

The small disassociation of negative and positive particles can create new particles, these particles can in turn have various effects and can continue to combine.

What the hell? Some sort of a really weird and factually wrong explanation of the zero point energy of the vacuum or something?

[Elfdude]

As for your "answer"; taking random factoids and mixing them all up in a bowl of complete BS, doesn't define Energy either. Just to point out a few glaring errors

I'm just going to assume you don't know who I am. I wouldn't engage me in debate without at least searching what I say in google because you're so far off base now your posts are ignorant.

1. The net energy of the Universe isn't zero, otherwise there would be no Universe.

Please review Einstein's theories. Stephen hawking also does an excellent lecture on exactly this topic. Unfortunately you seem to have a baser understanding of physics. Time to brush up.

http://www.astrosociety.org/pubs/mer...2/nothing.html

http://en.wikipedia.org/wiki/Vacuum_energy

Let's do the math here since you've so baselessly attacked my credibility.

(a) E (positive) = mc 2

and

(b) E (negative) = - m M u G / R u

If we were doing a high school physics problem, where we toss a ball of mass M straight up into the air with initial velocity V and we are asked to solve for the height H the ball will reach before it turns around and falls back to the ground, using energy equations rather than force equations, one typically writes the equation:

½ MV2 = MgH

However math is neat and lets us predict all sorts of neat things about the universe.

The above is equivalent to the equation:

½MV2 – MgH = 0

Interesting. It seems the net energy of throwing the ball is zero. I think part of the issue here is not understanding what net means. This is where we get the law of the conversation of energy. The equation is really a statement of Conservation of Energy and any system that starts with net energy ZERO must maintain that value, so if some energy goes positive then some other energy (gravitational) must go negative.

Now we can stop there and in highschool we do but we can continue to ask further questions such as how can we have negative gravity?

We can eliminate m from both terms (since it is a hypothetical particle anyway) and compare:

(a) the value of c 2

with

(b) the value of - M u G / R u

The first expression is the easiest. The velocity of light in this system of measure is c = 3 x 10 8 meters/sec.

So

(a) c^2 = (3 x 10^8 meters/sec) 2 = 9 x 10^16 meters^2 per second^2.

Now this is where it gets interesting. To consider the universe we need to go to the edges of it. Since we don't have the ability to do so seeing as light takes X time to reach us we'll simply speak of the visible universe.

One light year in meters = (velocity of light in meters/sec) times (number of seconds in a year).

Number of seconds in a year = (3600 sec/hour) x (24 hours/day) x (365.25 days/year) = 3.156 x 10^7 seconds/year.

(Yes. There are 365.25 as far as the SI standard is concerned - that's why we have leap years every four years.)

One light year = (3 x 10^8 meters/sec) x (3.156 x 10^7 sec/year) = 9.47 x 10^15 meters.

12 billion years = 12 x 10^9 years so

12 billion light years = (12 x10^9 years) x (9.47 x 10^15 meters per year) = 1.14 x 10^26 meters so

R u = Radius of Visible Universe = 1.14 x 10^26 meters

I won't do the calculations for the amount of mass here because it's ridiculously long, calculations have been made on the number of protons (and hence atoms) that the Universe generated during expansion as 10^80 protons (atoms of H+)

The mass of one proton = 1.67 x 10^-27 kilograms.

So multiplying these two numbers together gives us an estimate of the mass within the Visible Universe as:

M u = (1.67 x 10 -27 kilograms/proton) x (10 80 protons) = 1.67 x 10^53 kilograms.

But wait this is still not nothing? Certainly I must be wrong. That's again only if we stop here. We can go further.

Lets go back to Newton's Gravitational Constant in this system of units is G = 6.67 x 10^-11

So we are now ready to insert values into the more complicated expression:

(b) - M u G / R u = - (1.67 x 10^53) x (6.67 x 10^-11) / (1.14 x 10^26) = - 9.77 x 10^16

This is negative energy.

Now this is a bit of an issue because when we look at it the Net Energy of the Universe is not 0. It's roughly 8% away from being entirely 0 with + slightly greater than -. This would mean all sorts of uncomfortable things. However lets look at the calculations and see where the inaccuracy fails. The most suspect number is the age of the universe. In fact at the age of roughly 13 billion we realize the net energy of the universe is in fact 0.

The problem here is that the universe appears to be expanding, it's not stable. This would mean that both energy and negative energy are increasing. The convential explanation of this is subatomic particles slipping into reality. For this we can think of space as negative energy. The subatomic particles burst into existent and create a postive and negative energy force, the destroy themselves almost instantly. However over long distances this creates a huge repulsive force between objects. Since we know the energy must in fact be balanced (law of conservation of energy), in order for the energy to be balanced we need more mass but that's another whole bunch of physics I'm not going to get into with you.

2. Concepts of Positive and Negative energies only make sense when there is a point of reference, and it can be placed arbitrarily.

You're correct and that's just what I did. Describing what that positive and negative energy is however is another thing all together. We can certainly show what it does but that again isn't answering the question.

3. Energy is not movement, there is that other kind too y'know.

Energy on the simplest scale is movement. Vibrations. Whatever you want to term it. Friction does indeed occur because of the interaction of the atomic particles influencing each other's motion. The more motion on the macroscopic scale the more friction is generated. It's the same concept of kicking off with a skate board. Energy is transferred between particles via motion. A photon accelerates an electron into a higher state. Further energy propagates via distinct packages (we assume) for example electromagnetic energy is a photon. The weak nuclear force is generated by the electron shell. The strong nuclear force is generated by the nucleus shell. Gravity is assumed to be generated by it's own particle/wavepacket because gravity propagates at the speed of light. Electromagnetism should also have a negative component to it, it's opposite, similarly does gravity and the strong and weak nuclear forces. Without this negative component these factors violate the law of conservation of energy.

How is kinetic energy passed from one structure to another? What is the potential energy of the universe? How does gravity influence spcae? These are answered by understanding what energy is. Not just what it does. The Higgs boson pulls on space. The Photon transfers electromagnetic energy. There's still a lot of this we don't understand however and unfortunately his question actually crosses into the realm of, that's a great question because we don't really know.

http://www.youtube.com/watch?v=wMFPe-DwULM

What the hell? Some sort of a really weird and factually wrong explanation of the zero point energy of the vacuum or something?

Perhaps you don't understand the meaning of gross oversimplification. I stated at the beginning that was what it was.

[Ludicus]

Energy ...within a local environment it may be positive or negative

.
What do you mean by negative energy? negative mass?
Edit- I just read your last post now.

energy is movement

Well, energy is motion or ability to produce motion. The microscopic forms of energy are those related to the molecular structure of a system and the degree of the molecular activity.

Can it be observed, or only its effects? What actually is energy?

Being the expression of the ability to do work,energy is a scalar quantity that can not be observed directly but can be recorded and evaluated by indirect measurements.
Energy systems and applications

--

I'm just going to assume you don't know who I am

Just out of curiousity, a student of medicine, right?

[Elfdude]

You did not answer the question of what energy was. You answered with what energy does which is fundamentally different. I did note my explanation was a gross oversimplification but yours doesn't come close to answering the question. Classical physics calculations are fun of course but they don't answer the question of what energy actually is.

[Dolgorukiy]

You could have just said that by "Negative energy" you meant gravitational pull. Would have made it so much easier to understand what you meant. However, as you pointed out, Vacuum energy contributes to the expansion of the universe, therefore, on your scale of reference it would be positive, and since the universe is expanding with acceleration, "positive" energy must outweigh the "negative". If they were equal, the Universe would be 'flat'.

[Elfdude]

You could have just said that by "Negative energy" you meant gravitational pull. Would have made it so much easier to understand what you meant. However, as you pointed out, Vacuum energy contributes to the expansion of the universe, therefore, on your scale of reference it would be positive, and since the universe is expanding with acceleration, "positive" energy must outweigh the "negative". If they were equal, the Universe would be 'flat'.

I'm not doing justice to Stephen hawkings explanation it seems. If you want to really understand what I mean I'd recommend reading his lecture on the origins of the universe.

What do you mean by negative energy? negative mass?

That's a very good question and there's a lot of possible answers there. Regardless we know or assume that the universe should be a net of zero.

Well, energy is motion or ability to produce motion. The microscopic forms of energy are those related to the molecular structure of a system and the degree of the molecular activity.

Right, which is an interesting idea if we continue to apply it fractally.

Being the expression of the ability to do work,energy is a scalar quantity that can not be observed directly but can be recorded and evaluated by indirect measurements.

This view breaks down in quantum mechanics where matter and energy become indistinguishable.

Just out of curiousity, a student of medicine, right?

Indeed.

He means that it's below a certain point of reference, in this case particularly, there is a negative sign because of the tendency of objects with mass to attract one the other. In other words, by his definition, 'negative' energy contributes to the collapse of the universe.

He could have made that clearer, really.

That's only if we stop applying this rule, the rule continues to apply ad infinitum. Vacuume energy is one interesting application of this but it applies macroscopically to the shape of the universe it self. I would highly recommend Stephen hawking's lectures on this. Now admittedly he may be wrong but at the very least it comes closer to explaing what the nature of energy really is.

[Dolgorukiy]

He means that it's below a certain point of reference, in this case particularly, there is a negative sign because of the tendency of objects with mass to attract one the other. In other words, by his definition, 'negative' energy contributes to the collapse of the universe.

He could have made that clearer, really.

[Aztech]

I highly recommend reading The Feynman Lectures on Physics Volume 1 chapter 4. In chapter 4 Richard Feynman, one of the greatest scientists of all time, tries to explain what energy is.
Here is a short quotation:
"It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some
numerical quantity, and when we add it all together it gives "28"'—always the same number. It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas." Richard Feynman The Feynman Lectures on Physics Volume 1 chapter 4