# PhysicsE = mc², What is E?

#### mathmaniac

##### Well-known member
I checked google and all they have is E means energy.But what energy?Maximum energy?

#### MarkFL

Staff member
Re: E=MC^2,What is E?

Mass

#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

It talks about mass-energy equivalence but not about what the E means...
I think I know well enough about mass-energy equivalance and that mass is actually rest energy.Mass is made of stressed space (or photon) which is the same as energy.I went through the article and found out nothing more than things that I already thought I knew.Could you just quote any line from the article that highlights the answer to my question?I don't see anything other than "E" is energy?Does E mean the degree of compression of space?That is possible because E=mc^2 can be the kinetic energy of any object having mass travelling at c which is like unstressing all the stress...

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#### LLand314

##### Member
Re: E=MC^2,What is E?

I checked google and all they have is E means energy.But what energy?Maximum energy?
The equation to tell us exactly how much energy a given amount of mass represents.
In the world of subatomic processes, the mass of particles can change into energy in the form of light, heat or motion. Likewise, energy can also transform into mass. This is the most important understanding of the equation.

Hope this helps

#### Klaas van Aarsen

##### MHB Seeker
Staff member
Re: E=MC^2,What is E?

Mass is an illusion.
Or more accurately, there is no real distinction between mass and energy.
Given a certain amount of energy, it will attract other masses, just like a regular mass would.

Btw, the proper relation is: $E^2 = p^2c^2 + m_0^2c^4$, which takes kinetic energy properly into account, while the original formula only considers rest mass.

#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

LLand314 said:
The equation to tell us exactly how much energy a given amount of mass represents.
I think Energy is compression or stress.So here energy means the total amount of compression of space inside a mass,which is the same as the amount of energy it contains?Am I right?

#### Klaas van Aarsen

##### MHB Seeker
Staff member
Re: E=MC^2,What is E?

I think Energy is compression or stress.So here energy means the total amount of compression of space inside a mass,which is the same as the amount of energy it contains?Am I right?
The next step is to say that both mass and energy are illusions.
They are mere representations of a hyperdimensional space that is bent in such a way to create the illusion of mass-energy.
I'd like to think of that as stretching instead of compression though.
Near a mass the space continuum stretches into a sort of pit, making other masses fall into it.

#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

The next step is to say that both mass and energy are illusions.
You din't tell if you think I am right.I think you think I am.

What do you mean in the next step?That mass and energy are actual stress in space...?

They are mere representations of a hyperdimensional space that is bent in such a way to create the illusion of mass-energy.
You mean mass is twisted space when photon which is actually a space wave goes in circles in the process of pair production?This is what I think.

I'd like to think of that as stretching instead of compression though.
Streching or expanding is what happens when energy is released,but energy is actually stored as compressions...

Near a mass the space continuum stretches into a sort of pit, making other masses fall into it.
You mean the cannonball on a rubber sheet analogy.But I think thats the wrong analogy because it uses gravity to explain gravity.

Anyway thanks for participating in this discussion.

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#### LLand314

##### Member
Re: E=MC^2,What is E?

I think Energy is compression or stress.So here energy means the total amount of compression of space inside a mass,which is the same as the amount of energy it contains?Am I right?

The equation though is giving the pure energy; pure energy is electromagnetic radiation and electromagnetic radiation always moves at the speed of light which is why c is there.

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#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

The equation though is giving the pure energy; pure energy is electromagnetic radiation and electromagnetic radiation always moves at the speed of light which is why c is there.
Pure energy is space,electromagnetic radiation is space,c is space,everything is space...

This is what I think...

Please tell me if you think this is right or wrong...

"E" means how much the space is compressed in a mass.

Right or Wrong?

#### LLand314

##### Member
Re: E=MC^2,What is E?

Pure energy is space,electromagnetic radiation is space,c is space,everything is space...

This is what I think...

Please tell me if you think this is right or wrong...

"E" means how much the space is compressed in a mass.

Right or Wrong?
How do you yourself exactly define "space"?

#### Bacterius

##### Well-known member
MHB Math Helper
Re: E=MC^2,What is E?

Pure energy is space,electromagnetic radiation is space,c is space,everything is space...

This is what I think...

Please tell me if you think this is right or wrong...

"E" means how much the space is compressed in a mass.

Right or Wrong?
To quote a famous physicist, I think it's neither right nor wrong. It's meaningless since you haven't defined any of the terms you use. How does the speed of light equal space? What does "compressed space" mean? How can you be "in" a "mass", do you mean density?

To be honest I'm not sure this thread contains much information, this kind of physics doesn't really mean anything to the layman until he has some kind of background in relativistic and quantum physics (and I'm not claiming I have said background). It sounds cool to say that "mass is energy" but it doesn't really mean anything without proper definitions and context. It may, however, incite further research and spark an interest in the relevant field, which is a good thing.

#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

It's meaningless since you haven't defined any of the terms you use. How does the speed of light equal space? What does "compressed space" mean? How can you be "in" a "mass", do you mean density?
Oh sorry,by "c" I meant light not "the speed of light".

"Speed" is just a measure.It is space (distance) by time.

Compression is "Relative" because we don't know what is "perfect space.Where there is more compression (of any medium) it is found that there is more energy.Space is also thought to be a medium and so is thought of space.

To be honest I'm not sure this thread contains much information,
I was asking what Einstein meant by "E"
but never got a satisfactory reply so far.I was to give more clarification and information of my thoughts and thats all I did.

this kind of physics doesn't really mean anything to the layman until he has some kind of background in relativistic and quantum physics (and I'm not claiming I have said background).
The fact that energy is stress is conceivable to any layman and the fact that photon tied in a knot is also evident from "pairproduction".But I as a layman don't know why light is considered as simply a moving stress.If it is conjectured then everything becomes space.

You say the layman cannot understand the universe and I disagree.Because thats what the great physicists are doing nowadays.And thats what Einstein tried to do.It is possible.

But we can percieve the world much better if we know relativistic and quantum mechanics.

It sounds cool to say that "mass is energy" but it doesn't really mean anything without proper definitions and context. It may, however, incite further research and spark an interest in the relevant field, which is a good thing.
All I am sure is that mass is photon.But if I conjecture photon is a travelling stress in space I reach at the conclusion that everything is space.

Ok you want definitions of "mass" and "energy".Here it is from my point of view.

Mass-Mass is photon tied in a knot.And photon is travelling stress.So mass is a three dimensional space knot.

Energy-Energy is simply compressed space.(note the word "compressed" is relative)

I think it's neither right nor wrong.
Now that I have given clarifications of my thoughts tell me what you think the "E" means.Or tell me what Albert Einstein meant by it.

#### HallsofIvy

##### Well-known member
MHB Math Helper
Re: E=MC^2,What is E?

I was asking what Einstein meant by "E"
but never got a satisfactory reply so far.I was to give more clarification and information of my thoughts and thats all I did.o
You have been answered, you just don't like the answers! And from you "thoughts" the reason appears to be that you do not know what energy itself is. You talk about "compression" which is a force, not a type of energy at all.

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#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

Yes!I have been answered that mass and energy are equivalent and "E" is energy.But thats not complete.I mean you say E=1/2 mv^2 . You can say it is the energy transferred to a body of mass moving at constant velocity v, by a force.
But what does the "E" in "E=mc^2" mean?I have been simply answered "E" is energy.That doesn't make sense to me.

And from you "thoughts" the reason appears to be that you do not know what energy itself is.
OK,tell me what you mean by energy and what you mean by "E" in "E=mc^2".

You talk about "compression" which is a force, not a type of energy at all.
I didn't say "compression" is a type of energy,I said "compression" is directly proportional to energy.

Apologies if any of my thoughts seem insane.

#### HallsofIvy

##### Well-known member
MHB Math Helper
Re: E=MC^2,What is E?

"E" in $$E= mc^2$$ is the energy that would be released if you could convert all of the mass into energy. For example, when Uranium 235 fissions, it breaks into two atoms whose wait adds up to slightly less than that of the original U235. The energy produced by the fission is $$E= mc^2$$ where m is that "missing" mass.

#### agentmulder

##### Active member
Re: E=MC^2,What is E?

$$\text{Maybe we should do dimensional analysis in order to figure out what energy is and how} \\ \text{ it relates to other concepts. The quick answer is 'Energy is the capacity to do work and} \\ \\ \text{ is measured in Jouls for the MKS system'.} \\ 1J = 1N \cdot m \\ \\ 1N = \frac{kg \cdot m}{s^2} \\ \\ \text{therefore} \\ \\ 1J = 1kg \frac{m^2}{s^2} \\ \\ \text{and has dimensions} \\ \\ \frac{mass \cdot length \cdot length }{time \cdot time} \\ \\$$

$$\text{This is also true for gravitational potential energy} \\ \\ PE = mgy \\ \\ \text{mass times length squared divided by time squared (work out the dimensional analysis )} \\ \\ \text{And for the famous E = mc^2 all we need to remember is that c has dimensions meters} \\ \text{ per second so} \\ \\ E = \frac{mass \cdot length \cdot length }{time \cdot time}$$

We know what mass is, we know what length is, we have a pretty good idea of what time is... now we just have to figure out how to multiply and divide these dimensions. Hey that's probably much easier than trying to figure out the square root of a kilogram

$$\sqrt{kg} \ = \ ?$$ Last edited:

#### topsquark

##### Well-known member
MHB Math Helper
Re: E=MC^2,What is E?

In Special Relativity we have that the total energy of a particle can be written as
$$E^2 = p^2c^2 + m^2c^4$$

Here E is the total energy (more on this in a moment) of the particle, it has a (relativistic) momentum p, and a rest mass of m. If we approximate this equation we find that
$$E \approx mc^2 + \frac{1}{2}mv^2 + ~...$$
Note: This expression does not take into account any potential energy the particle might have. This is pure "rest energy" plus relativistic kinetic energy.

If the momentum of the mass is 0, then we have the "rest energy" $$E_0 = mc^2$$ which is the famous equation.

So what is E_0? If we convert all the rest mass of the particle into energy, we get E_0. Likewise if we use the full equation (line 2 of this post) we get what we call the "total energy" of the particle, which includes the energy due to the momentum as well.

I suspect that some of the problems here are due to language. However two things strike me:
1. You keep referring to a "compression." A compression of what? I don't have any idea what you are talking about here.

2. I believe you mentioned that all energy is made up of photons. This is not true at all. Photons carry energy just like any other particle. They are not made up of energy.

This is my attempt to make things clear. Many of these concepts have already been mentioned by others. Is there any specific question you have about this?
=========================================================

I'd like to take a moment to address another, possibly related, issue. I like Serena made the comment:
The next step is to say that both mass and energy are illusions.
Mass and energy are concrete and distinct concepts that exist in a kind of "duality." When we say that $$E = mc^2$$ we are not saying that mass and energy are the same. By some process we may be able to convert all the mass of a particle into energy but the equation merely says how much, not in what form it will take. (Sorry Mr. Spock. There is no such thing as "pure energy.") For example if we collide an electron with a positron (an anti-matter electron) we get $$2m_ec^2$$ of energy from the collision, plus whatever energy due to the overall momentum of the system contributes. But what form does that energy take? Most commonly as a photon. But it could also be a Z_0 particle, or a graviton, etc. (No single gluons. They have a special property called "color" and we can't directly observe this. You could have a "glue-ball" though which is a combination of more than one gluon in a semi-stable non-color state.)

This pretty much addresses everything I noted in this thread. Please pick my brains as you feel the need. -Dan

#### mathmaniac

##### Well-known member
Re: E=MC^2,What is E?

I suspect that some of the problems here are due to language. However two things strike me:
1. You keep referring to a "compression." A compression of what? I don't have any idea what you are talking about here.
compression of whatever it is in.And atlast maybe compression of aether.

2. I believe you mentioned that all energy is made up of photons.
Doesn't "Pair Production" imply this as it implies that an electron is in a way "a photon stopped"?

This is my attempt to make things clear. Many of these concepts have already been mentioned by others. Is there any specific question you have about this?
So what happens if all the mass is converted?massless photons?

Is there any evidence for it?A special particle for gravity?Seems insane to me..

Thanks everyone for your replies so far.

#### topsquark

##### Well-known member
MHB Math Helper
Re: E=MC^2,What is E?

compression of whatever it is in.And atlast maybe compression of aether.
When Quantum physicists deal with particles we put the interaction in free space. This is a microscopic viewpoint and not shared with Classical, or macroscopic, Physics. I am assuming that the conversation is centering about subatomic particles so there is nothing to compress in this case.

The existence or non-existence of the (luminiferous) aether is a long standing question. Michelson and Morely pretty much debunked the idea of the aether in the late 19th century but I've seen a couple of papers in recent years where it's been toyed with again. But at this time I don't think that any experiment has shown that any kind of aether exists.

Doesn't "Pair Production" imply this as it implies that an electron is in a way "a photon stopped"?
Pair production of electrons and positrons is the interaction: The photon is "destroyed" in the process and all of it's properties (energy, spin, etc) are reflected in the electron and positron so nothing is really stopped or lost, just transformed.

So what happens if all the mass is converted?massless photons?
As I mentioned in my last post when mass is converted to energy it has to be carried off by something, like photons, etc. Energy cannot exist on its own... it has to be carried off by a particle of some sort.

All photons are massless.

Is there any evidence for it?A special particle for gravity?Seems insane to me..
Gravitons (the particle field interpretation of a "gravity wave") are a tricky subject right now. No one has been able to detect one, but the theory of their existence seems sound. You can derive many of the properties of a graviton by looking at General Relativity and they are commonly used in Quantum Mechanics. And besides if you have two objects orbiting each other energy is lost to something as they spiral inward. For the moment we attribute the mechanism of such energy loss as the emission of gravitons. (For the record gravitons, like photons, are massless.)

For a more advanced answer all the forces we know of can be viewed as the interaction of a field with particles. In Quantum Electrodynamics (the quantum version of Electricity and Magnetism) this interaction field winds up being a spin 1 massless scalar particle. Being massless it travels at the speed of light. Experiments have verified that this particle is a photon. In quantum gravity it is a spin 2 massless scalar particle ie. the graviton. Being massless it too travels at the speed of light.

-Dan