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What really is the difference between matter and energy?





ocalhoun
What is the real difference between matter and energy?
Why is a photon always moving, while neutrons stay relatively still? (for example)
Why don't particles of energy (I guess you would call them that) want to stay put as well?
Just curious...
newolder
I can't do much better than this :: http://www.physlink.com/Education/AskExperts/ae98.cfm

except to stress that photons (or other zero mass entities) have zero Ricci and non-zero Weyl curvature in their action on space-time whilst matter is the opposite.
DjinniFire
From my knowledge and I guess it's similar to what newolder said.

Energy and Matter are in essence opposite. Matter as defined in Newtonian Physics is defined with the property of wanting to stay at rest. So if you think of them as opposites Matter stays at rest and Energy doesn't stay at rest :]

And I think energy if it didn't move, would cease to exist. The fact that it's moving gives it the energy and thus replaces the mass that it should have. Idk this is really confusing since I'm not really a physics buff.
Gagnar The Unruly
Energy is the essence of matter, so you can't really consider them opposites.
ocalhoun
I've been thinking, perhaps there are photons and such just sitting around all over the place...

This could be without our knowing it, because if they weren't moving, we couldn't detect them. In order to be detected, they need to move, and hit our eyes or our detectors...
newolder
That hypothesis is tested (and falsified) since every photon detected to date has a unique and traceable history across its space (time has no meaning for photon energy travelling at c).

There is no reservoir or "word-bag"-equivalent (Feynman) of photons. Smile
Bondings
Matter is a form of energy. Another form of energy is movement, so if it's not moving, there is no energy. A simplification, but it's a short explanation.
Bikerman
Bondings wrote:
Matter is a form of energy. Another form of energy is movement, so if it's not moving, there is no energy. A simplification, but it's a short explanation.

It raises additional issues, however, chief amongst them being 'movement with regard to what?'. What do we mean by movement and what do we measure it against?
KronikSindrome
Quote:
In the mass–energy equivalence formula E=mc2, mass and energy are more than equivalent, they are different forms of the same thing.


http://en.wikipedia.org/wiki/Mass-energy
Bikerman
KronikSindrome wrote:
Quote:
In the mass–energy equivalence formula E=mc2, mass and energy are more than equivalent, they are different forms of the same thing.


http://en.wikipedia.org/wiki/Mass-energy

Yes and no. The word equivalence is, I think, the best to use. It is also worth remembering what the m in the equation stands for. There are two measures of mass (although intertial mass is now much the favoured measure and relativistic mass is being killed off slowly). The two measures are intertial (invariant) mass and relativistic mass. Invariant mass is what you have now and does not change as you move faster. Inertial mass is, I think, a nicer term..but both terms describe it fairly well. This is the measure everyone knows.

Relativistic mass, however, DOES change as you go faster, and tends towards infinity as the speed of light is approached. This is often quoted as one reason nothing with mass (rest mass, or invariant mass) can travel at c. Relativistic mass, however, changes with speed according to the normal Lorentz factor.
The m in Einstein's equation relates to relativistic mass, not intertial mass. Many people do not realise this. Accordingly, we can re-write Einstein's equation to give us intertial mass as follows:
(BCC code is playing silly-buggers with me for some reason...why will it not take this image link I wonder...?
OK - in longhand it is ugly but :
e=mr*c^2 (mr - relativistic mass)
e=mr*c^2=m0/sqrt(1-v^2/c^2) (m0 is intertial mass)
sqrt(1-v^2/c^2) is called the Lorentz factor and is also applicable to length and time as a mass approaches the speed of light.

(This is an easy way to win a pint - bet someone they don't know what e=mc^2 means, or bet them it is wrong. Then all you have to do is move slightly and your rest mass is then different from your relativistic mass (only by the tiniest amount of course). Obviously when you are at rest (and all these conversations are actually meaningless unless we talk in terms, or better yet frames of reference [FOR] - that was the point I was trying to make earlier) so if I am at rest with regard to an observer, my rest mass is the same, for that observer, as my relativistic mass, since v=0 and therefore the Lorentz factor is 1-0/c^2 = 1. Multiplying by 1, of course, leaves the term as it was so now we can truly say that e=mc^2 and it doesn't matter that we are using the wrong measure of mass.
If I move, however, then v is non-zero and the Lorentz factor is therefore slightly less than 1, therefore e<>mc^2.

(This is the reason I am more comfortable with the word 'equivalence' than with the term 'is the same as'.)
dwinton
ocalhoun wrote:
What is the real difference between matter and energy?
Why is a photon always moving, while neutrons stay relatively still? (for example)
Why don't particles of energy (I guess you would call them that) want to stay put as well?
Just curious...


According to Einstein, matter is just a very efficient form of energy. One of Einstein's postulates is that all light goes at the same speed and that nothing can go faster than it. It is on these postulates that relativity (which has been demonstrated experimentally) is based. The thing about light is it has momentum. The momentum of light is h/lambda (planck's constant divided by the light's wavelength). that equals h*nu/c (planck's * the frequency of the light/ speed of light) which is the energy of the light over the speed of light. Because energy cannot be created or destroyed and momentum is preserved in a system with no external forces, when the light slows down, it's mass must increase to preserve momentum (which also equals m* velocity).

Neutrons do not stay still. The atoms in which they are located move around a lot (at normal temperatures) and so the neutrons also move. Neutrons also have a ton of mass so moving a neutron requires a ton of energy whereas light is massless.

Energy is usually described in quanta (basically what you would call a particle of energy, but a quantum is the smallest amount of energy that you can have wheras particles can be divided). Energy can stay put if it is in the form of mass; however, in other forms (such as light and thermal energy) it cannot. Light cannot stay still for if it does it becomes a particle with mass and thermal heat moves spontaneously from a greater temperature to a less great one.

Quote:
Another form of energy is movement, so if it's not moving, there is no energy. A simplification, but it's a short explanation.

Movement isn't a form of energy. A mass moving has kinetic energy though. And there is still potential energy and thermal energy created by moving objects.
Bikerman
dwinton wrote:
ocalhoun wrote:
What is the real difference between matter and energy?
Why is a photon always moving, while neutrons stay relatively still? (for example)
Why don't particles of energy (I guess you would call them that) want to stay put as well?
Just curious...


According to Einstein, matter is just a very efficient form of energy. One of Einstein's postulates is that all light goes at the same speed and that nothing can go faster than it.
Errr,,,no, that is incorrect (neither of the two posits/postulates is correct).
SR postulates that a particular photon(s) move at the same speed for all observers, but the speed of light itself varies depending on the medium through which it is moving. Relativity has nothing specific to say about c being a limit - there is no statement in relativity that forbids speeds above c.
Quote:
It is on these postulates that relativity (which has been demonstrated experimentally) is based.
Not really, but let's progress
Quote:
The thing about light is it has momentum. The momentum of light is h/lambda (planck's constant divided by the light's wavelength). that equals h*nu/c (planck's * the frequency of the light/ speed of light) which is the energy of the light over the speed of light. Because energy cannot be created or destroyed and momentum is preserved in a system with no external forces, when the light slows down, it's mass must increase to preserve momentum (which also equals m* velocity).
Not really. You need to distinguish between inertial mass (normal) and relativistic mass (what light has). If light grew more massive as it slowed down then we would expect it to have a rest mass (an inertial mass) but it doesn't.
Relativistic Mass is explained HERE
Quote:
Neutrons do not stay still. The atoms in which they are located move around a lot (at normal temperatures) and so the neutrons also move. Neutrons also have a ton of mass so moving a neutron requires a ton of energy whereas light is massless.
We can do better than 'tons'...
Mass of proton : 1,6726 x 10^(-27) kg
Mass of neutron: 1,6749 x 10^(-27) kg
Mass of electron: 0.00091x10^(-27) kg
Quote:
Energy is usually described in quanta (basically what you would call a particle of energy, but a quantum is the smallest amount of energy that you can have whereas particles can be divided). Energy can stay put if it is in the form of mass; however, in other forms (such as light and thermal energy) it cannot. Light cannot stay still for if it does it becomes a particle with mass and thermal heat moves spontaneously from a greater temperature to a less great one.
Fundamental particles cannot, we think, be divided - electrons, photons etc.. Light cannot stay still because it has no rest mass and does not exist, or thought of another way - light travels as a wave-waves move.
dwinton
Did you mean AE when you wrote SR?

[quote]In particular, special relativity states that it is impossible for any material object to accelerate to light speed.[quote]
Wikipedia says nothing can go faster than light according to special relativity.

I read that they think the electron can be split in two. [url = http://www.meta-religion.com/Physics/Particle_physics/electron_may_be.htm] I found something like what I read here [/url]. I know for a fact neutrons can be split into a proton and an electron. And wikipedia says protons are made of three quarks. I would imagine the proton can be divided that these three quarks can be separated somehow.
Bikerman
dwinton wrote:
Did you mean AE when you wrote SR?

No - I meant SR - Special Relativity....
Quote:
Wikipedia says nothing can go faster than light according to special relativity.

Well, itt shows that wikki is not perfect then Smile
Quote:
I read that they think the electron can be split in two.
No, I don't think you did - you may have thought you did....
Quote:


http://www.meta-religion.com/Physics/Particle_physics/electron_may_be.htm] I found something like what I read here [/url]. I know for a fact neutrons can be split into a proton and an electron. And wikipedia says protons are made of three quarks. I would imagine the proton can be divided that these three quarks can be separated somehow.

Nononono....this is all wrong....neutrons split into quarks as do protons and electrons don't split at all.
Quarks come in various types (flavours) but protons and neutrons are made up of up quarks and down quarks. Each up quark has a charge of +2/3 and each down quark has a charge of -1/3

A proton has one up quark and two down quarks. (+2/3 ) plus (+2/3 ) plus (-1/3) = +1 hence they have a electrical charge of +1)

A Neutrons has one up quark and two down quarks. (+2/3) plus (-1/3) plus (-1/3) = 0 (hence they have no charge)
jwellsy
Since a photon has no mass,
it is unaffected by any kind of binding energy,
so it just keeps on traveling till it is attenuated by collisions.
rohan2kool
Bondings wrote:
Matter is a form of energy. Another form of energy is movement, so if it's not moving, there is no energy. A simplification, but it's a short explanation.


movement is relative. considering the energy caused due to temperature of molecules (for instance), temperature is not relative (in the absolute scale). A better statement would be 'movement is the manifestation of energy'...
qsmith
movement itself is not energy, rather energy can be generated by making use of difference in the movement of two masses. Since there is no absolute frame of reference it is easier to consider everything as moving.
Bikerman
jwellsy wrote:
Since a photon has no mass,
it is unaffected by any kind of binding energy,
so it just keeps on traveling till it is attenuated by collisions.


http://www.photonics.com/content/spectra/2007/April/news/87182.aspx
http://newton.ex.ac.uk/aip/physnews.439.html
jwellsy
Those are some cool articles.
Photons in a mirror ball, cool.
They call it a non-demolition method,
yet, that seems to be a bit of a miss.
It is more like a slow destruction.
It only lasts for a tenth of a second before annihilation.
They are actually measuring the effects of the collisions
until total attenuation (demolition) of the photon.

Ionizing radiation particles have mass and a characteristic
called 'slowing down length' which is the distance from birth
till the point that it reaches an energy level equal to it's environment.
Those experiments seem to be measuring the non-mass equivalent
of 'slowing down length'.

The cumulative change in the target electrons energy state = initial photon energy =
average energy transfer per collision x # of collisions

They did not delve into the specific mechanics of the
interaction between the photons and the atoms.

I still believe that an energy transfer occurs
when a photon strikes an electron (electron field),
Increasing the energy state of the electron (target)
and decreasing the energy state of the photon.
If a photon strikes a nucleus it may or may not survive,
depending on the size of the target nucleus and
the angle of the collision trajectory.

The energy transfers in photon-electron collisions
are a much smaller magnitude than what would be required
to be considered a valence change in the target electron field.
yfan624
Matter is a form of energy.
Bikerman
jwellsy wrote:
I still believe that an energy transfer occurs
when a photon strikes an electron (electron field),
Increasing the energy state of the electron (target)
and decreasing the energy state of the photon.
If a photon strikes a nucleus it may or may not survive,
depending on the size of the target nucleus and
the angle of the collision trajectory.

That is correct. Regarding the photon as an em wave rather than a 'particle', we can use the Lorentz force :- F = qE + qvB (where q is charge B is the magnetic field strength, v is velocity and E is electric field strength)
In complete absorbtion the momentum transferred to the electron is obviously W/c (W - work) so that gives a measure of the energy transferred I think....although looking at it I think I need to divide by time t to go from work to energy (where t is the time for the electron to go from initial velocity to velocity after impact)
That would give W/ct.
Bikerman
jwellsy wrote:
I still believe that an energy transfer occurs
when a photon strikes an electron (electron field),
Increasing the energy state of the electron (target)
and decreasing the energy state of the photon.
If a photon strikes a nucleus it may or may not survive,
depending on the size of the target nucleus and
the angle of the collision trajectory.

That is correct. Regarding the photon as an em wave rather than a 'particle', we can use the Lorentz force :- F = qE + qvB (where q is charge B is the magnetic field strength, v is velocity and E is electric field strength)
In complete absorption the momentum transferred to the electron is obviously W/c (W - work) so that gives a measure of the energy transferred I think....although looking at it I think I need to divide by time t to go from work to energy (where t is the time for the electron to go from initial velocity to velocity after impact)
That would give W/ct.
newolder
The Physics News link (Bikerman, above) says::
Quote:
"If a photon is present, the atom acquires a phase shift which can easily be detected."


The total energy in the system made of a photon and a rubidium atom, H (the Hamiltonian) is easy enough to track with QM...

H = EPhoton + Eatom + Eother and Schroedinger relates these to eigenstates (e.g. sine waves with whole-number periods to match the timescales) of the complex wave-function to describe the most probable configuration of the energy that results.

H = E Psi

The phase-shift in France is the result of the action of a stationary (almost) photon packet of energy and rubidium atoms. It's new alright but may lead to further confusion and dead-ends, i fear. Butter is real; money (d'argent) is faith-based. Caveat emptor, as ever. ed. Smile
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