[Joe L. Ogan (OP)]

What is the difference between Mass and Matter?  It appears to me that there is a lot of similarity between the two but they are not just the same thing.  Do they both have gravity?  Does either have have an electrical charge?  Does either repell?  Do both attract?  Is the earth composed of Mass or Matter or both?  Thanks for comments.  Joe L. Ogan

[Farsight]

Mass is a measure, matter is "stuff". Mass causes gravity, and matter has mass, so that causes gravity too. Strictly speaking it's energy that causes gravity, and mass is a measure of energy, but we can come back to that. 

You can't say mass has charge, but you can say matter has charge. It's usually a combination of positive and negative charge, so there's no net charge. For example a hydrogen atom consists of a proton with positive charge, and an electron with negative charge. Alternatively, a neutron has no net charge, and so it doesn't attract or repel via electromagnetism, but it has a magnetic moment indicating that charge is present, see http://en.wikipedia.org/wiki/Neutron_magnetic_moment. Also check out Beta decay where a neutron turns into a proton, an electron, and an antineutrino. There are other neutral particles that have mass but no charge, such as the neutral pion, but it decays after a nanosecond. The neutrino is something of a special case, and is thought to have a slight mass and a "charge radius", but nobody knows for sure. 

The earth is composed of matter, and has mass.

[Joe L. Ogan (OP)]

How does Mass measure Energy?

[lightarrow]

How does Mass measure Energy?

A system's mass is nothing else that the energy contained inside that system (divided by the constant c²).

[Joe L. Ogan (OP)]

Am I then right to think that Mass is an inherent part of Matter?  And in the equation:   E=MC2, does the M= Mass or Matter?  Thanks for comments.  Joe L. Ogan

[LeeE]

I think you're better off thinking of Mass, or at least Rest Mass, as both a property and a measure of the quantity of matter, rather than being a 'part' of matter.  Temperature is another property of matter, and also a measure of the quantity of kinetic energy of the molecules that comprise the matter.

You can't have (Rest) Mass without matter, just as you can't have a temperature without matter.

Inertia is also a property of matter, but not exclusively so, otherwise things like light-sails wouldn't work.

It is incorrect to say that:

A system's mass is nothing else that the energy contained inside that system (divided by the constant c2)

for they are clearly different; if they were not, we would all be living in radiation and not matter.  However, matter and energy may be inter-converted and so may be considered equivalent in the same sense that a tank full of heating oil is equivalent to a warm home in winter.  You only need to try living in a tank full of heating oil to spot the difference between them though.

[Joe L. Ogan (OP)]

There is something that continues to bother me about this discussion.  If Mass is a measure of energy, then it can not be energy itself.  In the equation E=mc2, there is nothing to work out the equation without first getting a value for mass.  Since matter is the only thing that has energy, we must first get a value for it and convert that value into mass.  Now, I can see easily how that can be done, but it must be derived outside of the equation E=mc2.  So correct me if I am wrong but, the equation is not workable without first getting a value for mass.  Thanks for comments.  Joe L. Ogan 

[Farsight]

Joe/Dave, check out http://en.wikipedia.org/wiki/Mass_in_special_relativity where it says this:

..The invariant mass is another name for the rest mass of single particles. The more general invariant mass (calculated with a more complicated formula) loosely corresponds to the "rest mass" of a "system." Thus, invariant mass is a natural unit of mass used for systems which are being viewed from their center of momentum frame, as when any closed system (for example a bottle of hot gas) is weighed, which requires that the measurement be taken in the center of momentum frame where the system has no net momentum. Under such circumstances the invariant mass is equal to the relativistic mass (discussed below), which is the total energy of the system divided by c (the speed of light) squared.

Also see Einstein's 1905 paper Does the Inertia of a Body Depend Upon its Energy Content? at http://www.fourmilab.ch/etexts/einstein/E_mc2/www/. Einstein used L instead of E, and said:

If a body gives off the energy L in the form of radiation, its mass diminishes by L/c². The fact that the energy withdrawn from the body becomes energy of radiation evidently makes no difference, so that we are led to the more general conclusion that the mass of a body is a measure of its energy-content; if the energy changes by L, the mass changes in the same sense by L/9 × 10²⁰, the energy being measured in ergs, and the mass in grammes. 

If you heat a body such as a container of gas, the kinetic energy of the particles increases. The rest mass of the individual particles doesn't increase because they aren't at rest. However the container of gas is at rest. Its rest mass increases. If it's hot, it weighs more. That's what E=mc² is all about. Back in 1905, Einstein told us that a hot body weighs more than it does when it's cold. The underlying reason is down to a symmetry between momentum and inertia, but you never see it in magazines or articles. Relativity never seems to be explained properly.

[Joe L. Ogan (OP)]

Do you or does anyone else have a formula for Mass?  Thanks for comments.  Joe L. Ogan

[Farsight]

It is incorrect to say that:

A system's mass is nothing else that the energy contained inside that system (divided by the constant c2)

for they are clearly different; if they were not, we would all be living in radiation and not matter.

It is correct Lee, no kidding. The trick to it is to look at electron-positron annihilation, and to understand that the electron is "a system". Einstein said a body loses mass through radiation. When annihilation occurs, the electron loses mass through radiation. It loses all of its mass. Then the system called the electron, the "matter", no longer exists.

Check out The nature of the electron by Qiu-Hong Hu which appeared in Physics Essays, Vol. 17, No. 4, 2004. You can find it at http://arxiv.org/abs/physics/0512265. Most people haven't heard of this yet, it's a shame Nature turned it down. But it's good peer-reviewed science. Electrons really do have angular momentum and spin, and they really are made out of radiation using pair production. In a nutshell, when you employ pair production to split a photon and make it go round and round instead of moving laterally at c, we don't call it a photon any more. We call it an electron.



(Or a positron, if it's the opposite chirality).

Joe: see http://en.wikipedia.org/wiki/Mass_in_special_relativity#The_mass_of_composite_systems for a formula. If the momentum p is zero because you're talking about a particle rather than a system of moving particles, the expression reduces to m=E/c².

[Joe L. Ogan (OP)]

This is very interesting and much appreciated.  Now, Will you or anyone else work out a formula of E=mc2.  If you can not do that, will you, or anyone else, please give me a formula for Mass?  There are two unknowns in the equation:  E-mc2.  I can see no way to get a number with the two unknowns.  Thanks for comments.  Joe L. Ogan

[Joe L. Ogan (OP)]

Does the speed of light really have any relevance to energy or was it just the largest number that Einstein could imagine when he devised the equation:  E=mc2?  Thanks for comments.  Joe L. Ogan

[litespeed]

Joe

I think there is a confusion between mass and temperature. Mass has potential energy that is fixed at E=MC2. That potential energy was created when matter condensed from energy after the big bang. That mass can also have kinetic energy we call temperature.

However, I have never seen it stated that the big bang, prior to the 'precipitation' of matter did not have temperature. Its just that we are used to measuring temperature using massive devices.  If you stick a massive thermometer in front of an industrial laser which emits pure energy, it will vaporize before it gives a reading.

I suppose we could say that no temperature existed prior to the introduction of a material measuring device. Still, we can extrapolate temperature of pure energy without needing to do that. Perhaps it is explained by 'potential' temperature that a given amount of pure energy could impart to a given amount of mass.


As usual, I am probably wrong about this. But it just makes common sense.

 

[lightarrow]

This is very interesting and much appreciated.  Now, Will you or anyone else work out a formula of E=mc². 

Sorry, what do you mean with "work out"? The meaning of that formula?

If you can not do that, will you, or anyone else, please give me a formula for Mass?  There are two unknowns in the equation:  E-mc².  I can see no way to get a number with the two unknowns.  Thanks for comments.  Joe L. Ogan

It depends. If you know mass from something else, you can compute the energy with that formula (provided that system's momentum is zero); if you know the energy from something else, you can compute the mass.

Examples:
1. You have a block of 1 kg of iron. Then you heat it to 500°C. Will your (very sensitive) scale measure a different weight now? Yes, because you gave energy to the system so its mass has increased. How much? If you heated the block with an electric resistor, ∫R i² dt is the energy ΔE you gave it, so your block's weight has increased of g*ΔE/c². Note that when you measure the block's mass it have to be *still* or you cannot use E = mc²; you have to use E² = (mc²)² + (cp)² instead, if the block moves with momentum p.

2. Will an high energy photon convert itself into other particles? Well, if that photon has an energy less than 1022 keV, it cannot convert in any particle, because if it does, it must generate couples electron/positron and a single couple has a total mass of electron_mass + positron_mass = 9.109558*10^-31kg + 9.109558*10^-31kg = 1022 keV/c²   so this is the minimum energy required to a photon to generate particles.

3. You have 1g of matter and 1g of antimatter. Will the energy get from the annihilation of the two be able to destroy a city as the Hiroshima's atomic bomb?
I leave this as excercize for you.

[lightarrow]

It is incorrect to say that:

A system's mass is nothing else that the energy contained inside that system (divided by the constant c2)

for they are clearly different; if they were not, we would all be living in radiation and not matter.  However, matter and energy may be inter-converted and so may be considered equivalent in the same sense that a tank full of heating oil is equivalent to a warm home in winter.  You only need to try living in a tank full of heating oil to spot the difference between them though.

1. "Matter" is not "mass". The first means "particles with non zero rest mass", the second means E/c².
2. As I explained a lot of times, the system have to be still, or you cannot use E = mc². A photon cannot be still, so you can never use E = mc² so you cannot say that for a photon the mass is E/c². Infact it's massless...
3. Suppose you havea box with two holes and a laser light pulse enter one hole and exit the other. During the little interval of time in which the light pulse can be localized (or part of it) inside the box, the box acquires a mass m = E/c² if E is the light pulse's energy.

[Joe L. Ogan (OP)]

Are you telling me that the equation E=mc2 is not workable?  I have found out that the constant for Mass is the Kilogram.  I assume that matter must be converted to Kilograms in order to work the equation E=mc2.  What would prevent that?  Thanks for comments.  Joe L. Ogan

[lightarrow]

Are you telling me that the equation E = mc² is not workable? 

Sorry but I'm not native english speaking, so I don't understand what exact meaning to associate to "workable" in this context, so I'll try to explain better what I've already written.

The equation, as any other equation, is valid only in specific cases. This one is valid *only if the system is stationary, that is it doesn't move*. In physics, even the phrase *it doesn't move* have to be precisely specified: if you have a system consisting of two equal iron balls moving fast in opposite directions, then the system is stationary, because its centre of mass has velocity = zero.

You can define the concept of "stationary" even if you have a system made up of massless objects, like photons. Instead of talking about centre of mass, you talk about *total momentum*: if two equal energy photons are flying in opposite directions, then the system of the two photons is stationary because its total momentum is zero. Then you can apply E = mc² even to such a kind of system and you discover that this system *has mass*. I mean, not *relativistic* mass, but real, invariant mass. A single photon is massless, but two photons travelling in opposite directions has mass! (and even if they are not travelling in opposite directions but simply in different directions, because it turns out that in this case you can always find an inertial frame of reference where they travel in opposite directions).

In conclusion, you can apply E = mc²   but only if the system is stationary.

I have found out that the constant for Mass is the Kilogram.  I assume that matter must be converted to Kilograms in order to work the equation E = mc².  What would prevent that?  Thanks for comments.  Joe L. Ogan

Can you explain better what you mean?

[LeeE]

It is incorrect to say that:

A system's mass is nothing else that the energy contained inside that system (divided by the constant c2)

for they are clearly different; if they were not, we would all be living in radiation and not matter.

It is correct Lee, no kidding. The trick to it is to look at electron-positron annihilation, and to understand that the electron is "a system". Einstein said a body loses mass through radiation. When annihilation occurs, the electron loses mass through radiation. It loses all of its mass. Then the system called the electron, the "matter", no longer exists.

Check out The nature of the electron by Qiu-Hong Hu which appeared in Physics Essays, Vol. 17, No. 4, 2004. You can find it at http://arxiv.org/abs/physics/0512265. Most people haven't heard of this yet, it's a shame Nature turned it down. But it's good peer-reviewed science. Electrons really do have angular momentum and spin, and they really are made out of radiation using pair production. In a nutshell, when you employ pair production to split a photon and make it go round and round instead of moving laterally at c, we don't call it a photon any more. We call it an electron.



(Or a positron, if it's the opposite chirality).

Joe: see http://en.wikipedia.org/wiki/Mass_in_special_relativity#The_mass_of_composite_systems for a formula. If the momentum p is zero because you're talking about a particle rather than a system of moving particles, the expression reduces to m=E/c².

Good grief - talk about trying to teach your grandmother to suck eggs.

Oh, and you're still wrong; mass is not energy and visa-versa but there seems little point in repeating the differences between them.

Do you honestly really think that an electron is just a photon that's orbiting an atomic nucleus?

Electrons are not only made as a consequence of combining two photons but also as a result of free neutron decay.  Also, you can't employ pair production to 'split' a photon; that's rather like putting the cart before the horse.  What happens is that a high-energy photon interacts with other matter (usually an atomic nucleus) and the electron-positron pair are produced as a result.  The electron in the pair is very unlikely to end up being 'adopted' by the atom that produced it, and end up going round and round instead of laterally.  Incidentally, what do you think happens to the positron that's also produced?  You fail to mention its fate.

[Joe L. Ogan (OP)]

Here is what I mean.  There are about 15 lbs of U258 in an atomic bomb. There are about 7 kilograms of Mass in 15 lbs of U258.  To work the equation E=mc2, substitute 7 kilograms for mass and then one can get a value for Energy by multiplying the speed of light squared by 7.  The answer will be expressed in Joules.  And that is the amount of energy in 15 lbs of U 258.  Thanks for comments.  Joe L. Ogan

[LeeE]

It is incorrect to say that:

A system's mass is nothing else that the energy contained inside that system (divided by the constant c2)

for they are clearly different; if they were not, we would all be living in radiation and not matter.  However, matter and energy may be inter-converted and so may be considered equivalent in the same sense that a tank full of heating oil is equivalent to a warm home in winter.  You only need to try living in a tank full of heating oil to spot the difference between them though.

1. "Matter" is not "mass". The first means "particles with non zero rest mass", the second means E/c².
2. As I explained a lot of times, the system have to be still, or you cannot use E = mc². A photon cannot be still, so you can never use E = mc² so you cannot say that for a photon the mass is E/c². Infact it's massless...
3. Suppose you havea box with two holes and a laser light pulse enter one hole and exit the other. During the little interval of time in which the light pulse can be localized (or part of it) inside the box, the box acquires a mass m = E/c² if E is the light pulse's energy.

Sigh...  more nonsense.

The reason that E=mc² cannot be applied to photons is because [the photon], as you eventually point out...

Infact it's massless...

...so of course if you tried to apply E=mc² to a photon you'd end up with a big fat 0.  It's got nothing to do with whether the photon is 'still' or not.

I'll also just remind you that there is no absolute frame of reference, so the notion that anything is 'still' is purely relative.