# Thread: Can anyone explain to me Einstein's theory

1. E=mc2 , this is the theory of einstein but the problem is i have searched about it in wikipedia but the explanation was complex so can anyone explain it to me in a simple way ?

2.

3. To clarify, are you asking about the derivation of E=mc^2, or about special and general relativity?

4. Originally Posted by Dou7a
E=mc2 , this is the theory of einstein but the problem is i have searched about it in wikipedia but the explanation was complex so can anyone explain it to me in a simple way ?
This is not a theory but the result of a mathematical equation. Please specify more precisely.

5. I'm pretty sure the "Theory of Einstien encompasses more than "E=mc^2"

6. My interpretation of E= mc(squared)

is that energy = mass x speed of light squared

if you put an atom on a weighing scales, suppose it has 'x' mass

that would be a measure of the weight of the electrons in orbit and the nucleus holding them so.

the centripital force of the electrons, and the gravity-like force of the nucleus is the the total energy.

if it the electrons were isolated from the nucleus they would move like light, accellerating away, thus squared.

and the nucleus would fall into itself, accellerating into the infinitismal, accellerating thus squared.

Yeah, clearly i have no education on these matters, but that's my take on it anyway, and it's kept me out of trouble to date..

7. Originally Posted by pedronaut
My interpretation of E= mc(squared)

is that energy = mass x speed of light squared
If you'd stopped right there, you would have been okay, after that it became hopelessly confused.

The actual meaning is that there is an equivalence between energy and mass. Or that a piece of matter of mass M could be converted into an amount of energy equal to the value of that mass times the speed of light. For instance, 1 kg of matter could be converted to 9 x 10^16 joules of energy.

if you put an atom on a weighing scales, suppose it has 'x' mass

that would be a measure of the weight of the electrons in orbit and the nucleus holding them so.

the centripital force of the electrons, and the gravity-like force of the nucleus is the the total energy.

if it the electrons were isolated from the nucleus they would move like light, accellerating away, thus squared.

and the nucleus would fall into itself, accellerating into the infinitismal, accellerating thus squared.

Yeah, clearly i have no education on these matters, but that's my take on it anyway, and it's kept me out of trouble to date..

8. "equal to the value of that mass times the speed of light."

don't you mean, the speed of light squared.

9. Yeah, Janus made a mistake in typing but his logic was accurate. You are mistaken on all the basics and logicallly inconsistant.

Yet instead of learning, you nit-pick and castigate him ???????????

Anyhow, is anybody going to offer a simple explanation as to how the equation is arrived at...

11. Originally Posted by pedronaut

Anyhow, is anybody going to offer a simple explanation as to how the equation is arrived at...
Here is a section off the mass-energy equivalence page on Wiki partially explaining that:

In developing special relativity, Einstein found that the kinetic energy of a moving body is

with v the velocity, m0 the rest mass, and γ the Lorentz factor.

He included the second term on the right to make sure that for small velocities, the energy would be the same as in classical mechanics:

Without this second term, there would be an additional contribution in the energy when the particle is not moving.

Einstein found that the total momentum of a moving particle is:

and it is this quantity which is conserved in collisions. The ratio of the momentum to the velocity is the relativistic mass, m.

And the relativistic mass and the relativistic kinetic energy are related by the formula:

Einstein wanted to omit the unnatural second term on the right-hand side, whose only purpose is to make the energy at rest zero, and to declare that the particle has a total energy which obeys:

which is a sum of the rest energy m0c2 and the kinetic energy. This total energy is mathematically more elegant, and fits better with the momentum in relativity.

12. Well, if that is what Wikipedia says, it is not historically correct. In fact is not central to the Special Theory - it is a derived result. Neither do I believe that Einstein ever derived this identity in the way that Wikipedia claims, at least not in his originak works (though he may have done so in one of his many pop-sci writings.

Here's the original Einstein (hugely paraphrased):

Consider a material body with energy content . Let emit a "plane wave of light" for some fixed period of time . One easily sees that the radiation energy content of is reduced by

Let i.e.the light energy "withdrawn" from which obviously only depends on .

Now, says Einstein, consider the situation from the perspective some body moving uniformly at velocity with respect to . Then, evidently, by Lorentz time dilation, , by the Special Theory, depends only on , which is .

The difference between and is simply . By expanding as a Taylor series, and dropping terms of order higher than 2 in , he finds that (and you can too, with a little simple algebra!)

.

Mathematically this all makes sense. What is not obvious is that the identity makes any sense, that is to say, it is not immediately obvious that the total energy withdrawn from a body varies with its state of motion relative to some alternative reference point

But, Einstein now says something like this: is an equation for the differential energy of bodies in relative motion; but so is , the equation for kinetic energy - these can only differ by an irrelevant additive constant, so from the above set

and so .

But, says he, is simply a "quantity" of energy, radiation in this case, that now depends only on and so......

.

Which is merely to say that, since is a universal constant, that mass and energy are conserved under any arbitrary coordinate transformation that is either globally or locally consistent with the the Special Theory

13. forgive me for being presumptuous,
But OP here requests simplicity not neccessarily Math jargon.

Is the total energy in a piece of matter the sum of the 4 known forces,
strong and weak nuclear forces and the electromagnetic force and the gravitational force.

Did Einstein arrive at this via mathematics
or did he visualise the breakdown of an atom into nuclear, electrical and gravitational energy

14. Yes, that is being presumptuous. People constantly want these things explained in a simple way, but these theories are not simply or intuitive, and such a simple explanation would inevitably be incorrect. Einstein, probably, used a combination of visualization and mathematics to get the general idea, but the end result of that is solidly mathematical.

15. Originally Posted by Guitarist
Well, if that is what Wikipedia says, it is not historically correct. In fact is not central to the Special Theory - it is a derived result. Neither do I believe that Einstein ever derived this identity in the way that Wikipedia claims, at least not in his originak works (though he may have done so in one of his many pop-sci writings.

Here's the original Einstein (hugely paraphrased):

Consider a material body with energy content . Let emit a "plane wave of light" for some fixed period of time . One easily sees that the radiation energy content of is reduced by

Let i.e.the light energy "withdrawn" from which obviously only depends on .

Now, says Einstein, consider the situation from the perspective some body moving uniformly at velocity with respect to . Then, evidently, by Lorentz time dilation, , by the Special Theory, depends only on , which is .

The difference between and is simply . By expanding as a Taylor series, and dropping terms of order higher than 2 in , he finds that (and you can too, with a little simple algebra!)

.

Mathematically this all makes sense. What is not obvious is that the identity makes any sense, that is to say, it is not immediately obvious that the total energy withdrawn from a body varies with its state of motion relative to some alternative reference point

But, Einstein now says something like this: is an equation for the differential energy of bodies in relative motion; but so is , the equation for kinetic energy - these can only differ by an irrelevant additive constant, so from the above set

and so .

But, says he, is simply a "quantity" of energy, radiation in this case, that now depends only on and so......

.

Which is merely to say that, since is a universal constant, that mass and energy are conserved under any arbitrary coordinate transformation that is either globally or locally consistent with the the Special Theory
This is one of the most helpful and well-explained derivations I have seen on this forum, thank you!

16. Originally Posted by MagiMaster
Yes, that is being presumptuous. People constantly want these things explained in a simple way, but these theories are not simply or intuitive, and such a simple explanation would inevitably be incorrect. Einstein, probably, used a combination of visualization and mathematics to get the general idea, but the end result of that is solidly mathematical.
Yes - I'd like to validate your comment - people constantly want these things explained in a simple way...... My genius geek rockstar can see the elegance in physics/math formulas..As Dirac says - look for the beauty in the math (something like that)... he can see it. I can't. Oh well. And with that, I need to stay off this board.

17. Epidemos, your commernt makes about as much sense as do my theories of space and time, maybe stick to math and forget about english.

Permit me to go off topic.
I don't think it's much to ask to have 'these things' explained in a simple way. Is that not the point of the natural sciences.

I accept that university level math is required to master the higher level physics concepts, but surely the lay man can generally be afforded a rough explanation.

"Complexity is simply an excess of simplicity"

18. The problem is people want these things oversimplified. They want it simplified to the point of uselessness.

The math is important. Getting some help understanding the math is valid. Trying to get rid of the math isn't.

19. Originally Posted by Dou7a
E=mc2 , this is the theory of einstein but the problem is i have searched about it in wikipedia but the explanation was complex so can anyone explain it to me in a simple way ?
1) I think that if one wants to help a student, should try not to show off his own culture, be hair-splitting and pedantic, criticize eventual imprecisions,
but try, with empathy, to understand his problem from his point of view.

Remarking that einstein has a lower-case e is as mean as pointing out that it is not a theory.
Moreover, I think that if one is not able to give an intelligent answer to a silly question, he should just abstain and refrain from giving a silly answer. I joined some time ago but abstained from starting threads or sending posts, because I do not wish being abused in a forum. Now,
I do hope that the new Admin will prevent that and wish him well and,
I wish thescienceforum be the place where even if you ask a stupid question you get an intelligent and corteous answer.

So, if anyone does not agree with anything I say, let him state his different opinion, or correct eventual mistakes, in an impersonal way, as I am doing now.

2) many people, and most if-not-all scientists, tend to think that maths is something completely different from everyday language, or even that is not language at all.
This is a false belief. Maths is just shorthand language, a subset of any language that is useful just because it is (the same in every language) universal.
there is no difference whatsoever between " two and two makes four" and " 2+2=4".
TWO and 2 are both signs, signifiers of a linguistic sign (words) which happen to have the same signified (meaning).

1) the idea (theory) that light and matter might be inter-convertible goes back to 1717 (Newton), then it was developped in 1900 by Wien and others (who gave different values to the equivalence)
Einstein produced the current formulation for this concept E = m * C^2
that means only that (the mass of)

ONE electron can be trasformed into (energy, light,)
ONE photon whose energy is (0.511 MeV, which is equivalent to) 1.24 x 10^20 Hz which is
roughly equivalent to C^2 (speed of light -squared divided by 8)

TO OVERSIMPLIFY IT:2) It is roughly like when you burn wood to warm yourself, the difference is only that the electron completely disappears,
leaving no ashes !

if you burn one electron you just get 250,000 rays of yellow light

20. Originally Posted by formal

1) I think that if one wants to help a student, should try not to show off his own culture
Forgiving your poor grammar, NO I was not trying to "show off mine own culture", I was genuinely trying to help the OPer, Believe me or not, your choice. Alternatively read Einstein's 1905 paper and see if you or the OPer understands it better that my explanation.

Moreover, I think that if one is not able to give an intelligent answer to a silly question, he should just abstain and refrain from giving a silly answer.
So the question was "silly" and my answer was not "intelligent"? Why do you think the question was silly? Why was my answer silly? Please elaborate, or get lost

{JabaJabaJaba, all nonsense}

if you burn one electron you just get 250,000 rays of yellow light
I hope all here realize this is complete gibberish?

Plucking at random, how do I burn an electron?

21. Einstien's theory was based on spherical electromagnetic radiation. However, electromagnetic radiation is not truly spherical, which casts doubt on his theory.

Einstein's energy equation E=mc^2 is easily derived from the electromagnetic model of the atom.

Electromagnetic radiation theory is the key to understanding the universe.

22. Originally Posted by MagiMaster
The problem is people want these things oversimplified. They want it simplified to the point of uselessness.
The math is important. Getting some help understanding the math is valid. Trying to get rid of the math isn't.
I would suggest that people want things sufficiently simplified, which is not necessarily the same thing. My son, for example, wouldn't know or understand a derivation, if it hit him in the face. And at this stage, maths would be too much for him. In this respect, everyone is different.

23. Originally Posted by Dou7a
E=mc2 , this is the theory of einstein but the problem is i have searched about it in wikipedia but the explanation was complex so can anyone explain it to me in a simple way ?

The equation is read from left to right, and says that Energy (E) is equivalent to (=) the mass (m) of some stuff, multiplied by the value of the speed of light (c), squared (2).

It is not a theory, but a famous mathematical equation which explains how Energy (represented by the letter E) and the mass (m) of stuff, are related. It is sometimes called the Mass-Energy Equivalence equation.

What the equation means is that energy is a different form of mass. All objects have mass (which is a measure of how much stuff we have, similar to weight). Energy is like heat and light. You are probably most familiar with converting a mass of uranium into heat energy in either (a) an atom bomb, (b) in a nuclear power station.

So the equation tells us that if we had one kilogram of uranium, and if we could convert it entirely into energy, then the amount of energy, E, produced would be:

Joules

As a comparison, this is about the same energy released by 21,000 tons of TNT, or half a million US gallons of gasoline.

24. Originally Posted by sharpsword
Einstein's energy equation E=mc^2 is easily derived from the electromagnetic model of the atom.
Then "easily derive" it for us, as it is beyond my powers. In fact my first instinct is that this is wrong, but I am quite willing to be shown otherwise.

Electromagnetic radiation theory is the key to understanding the universe.
I am sure it is, maybe you would care to elaborate. Wait, on second thoughts, don't bother, as I am pretty sure this is a claim without content.

Prove me wrong (you can use mathematics if you like, I am cool with that, and so are many others here).

25. Originally Posted by Guitarist
Originally Posted by sharpsword
Einstein's energy equation E=mc^2 is easily derived from the electromagnetic model of the atom.
Then "easily derive" it for us, as it is beyond my powers. In fact my first instinct is that this is wrong, but I am quite willing to be shown otherwise.

Electromagnetic radiation theory is the key to understanding the universe.
I am sure it is, maybe you would care to elaborate. Wait, on second thoughts, don't bother, as I am pretty sure this is a claim without content.

Prove me wrong (you can use mathematics if you like, I am cool with that, and so are many others here).
It is not just a claim, as you claim. It has been published. The forces acting on the electron in an atom are electromagnetic in this derivation. The Coulomb force attracts the electron to the proton, which is the electrostatice force. The electromagnetic force is in the opposite direction and it is equal to the Coulomb force in a stable atom. The derivation of the electromagnetic force was the primary obstacle. It begins with the Lorentz force which includes the above forces. The laws of electromagnetics were applied, and the "cross vector" equation was derived.

The Lorentz force is a vector equation: Fbar = q(Ebar + vbar cross Bbar). Sorry, but I don't know how you print these variables properly, Can I cut and paste them somehow? The bar means that the variable is a vector. Applying the laws of electromagnetics, the magnetic force is determined, which turns out to be

Fm = Ke x (v^2/r^2c^2). This opposes the Coulomb force Ke/r^2, and the two are equal in a stable atom. Einstein's energy equation can be derived by equating the magnetic force to the "particle force" of mechanics!

The derivation of the magnetic force is a bit complex, but it has been documented. Would you like a reference? If I could cut and paste it here, then that could also be done.

BTW, we have Latex support for equations. Have a look HERE.

27. Originally Posted by KALSTER

BTW, we have Latex support for equations. Have a look HERE.
It would probably be best to go through the equations one by one so that you can critique each one. I normally use Mathtype and Mathcad for my equations. With Mathcad, the answers can be checked for accuracy. I have used Latex before but it seems slow to me. Perhaps that is just me, though. Let me bone up on it, and I will get back to you on this. It will be helpful to me to have someone critique these equations. If you are not familiar with the basics of electromagnetics, then let me give you my reference for this subject: Sir Charles Oatley, "Electric and Magnetic Fields", Cambridge University Press, 1976. Chapter four of this book provides much of the basic materials and the excellent methods employed by this expert. I have also used Planck's Columbia Lectures, Lecture Seven, "The Principle of Least Action", fpr the actions of moving electrons in cyclical coordinates without losses.

28. Here's a try at an answer invoking as little math as possible. Einstein's theories unified space and time into a single 4-dimensional space-time. Note that in doing so we should use the same units for both distances and durations. The conversion constant is based on the speed of light in a vacuum 1 second = 299,792,458m. So in common units if you're moving at the speed of light your speed is 1 = 1 lightsecond/second. Massive objects necessarily move at a speed less than 1.

Similarly the three dimensional spatial velocity gets unified into a 4 dimensional space-time velocity (how fast an object's space and time coordinates are changing w.r.t. a clock moving along with that object i.e. w.r.t. proper time.) This 4-velocity has a magnitude which is the same no matter how observer's are moving relative to the object (i.e. no matter how the object is moving relative to the observer). What's odd about special relativity and its generalization is how the magnitude of a 4-vector is calculated. Instead of taking the square root of the sums of squares one takes the square root of the difference in the squares of the time-like and space-like components.

Now the invariance of the magnitude of a 4-velocity means especially that if I'm moving along with the object (i.e. it is stationary w.r.t. me) then the magnitude of its 4-velocity is easy to calculate. It isn't changing spatially at all and it is moving through time at 1 second per second. 4 velocities for massive objects always have magnitude 1. When seen from a moving frame the bigger the spatial velocity then the bigger the speed through time so that the difference in the squares stays just 1. (That's why you get time dilation.)

OK, Now comes the mass times velocity or momentum. The usual momentum gets unified with energy to yield the momentum-energy 4-vector. You again have to throw some C's in there to get the units the same but again you get an invariant magnitude. The magnitude for the energy-momentum vector of an object is the magnitude when it is at rest which is just the energy, but given momentum is mass times velocity the magnitude of the energy-momentum has to also be mass time the magnitude of the 4-velocity, That's mass * 1. So mass = rest energy. That's the equation and the c^2 business is just the necessary unit conversion factor. Like with velocity when the object is moving the momentum increases and so the energy must increase too (kinetic energy) so that the square energy - square momentum stays constant.

The full equation is not that's just a special case when the spatial momentum is zero, i.e. for an object at rest.
Rather the general relation is: , the mass is the square magnitude of the energy-momentum 4-vector, (with some c's in the equation to convert to energy units.)

The "Eee equals em cee squared" is a popularized expression of the big idea: unification of space-time and of momentum-energy. With this where we have momentum = mass times velocity, we get energy is mass times speed through time which is just mass when an object is at rest. E=m. (plus unit conversion).

29. Originally Posted by jambaugh
The full equation is not that's just a special case when the spatial momentum is zero, i.e. for an object at rest.
Rather the general relation is: , the mass is the square magnitude of the energy-momentum 4-vector, (with some c's in the equation to convert to energy units.)
I don't think the distinction between rest mass and inertial mass was clearly made, the total energy of a body being the product of the inertial mass and a term or being a slight rearrangement of the norm of the momentum 4-vector. If the mass in equation 1 of the quote is the inertial mass then it is as good an expression for the total energy as equation 2.

Edit: altered to make more sense.

30. Originally Posted by pedronaut
Epidemos, your commernt makes about as much sense as do my theories of space and time, maybe stick to math and forget about english.

Permit me to go off topic.
I don't think it's much to ask to have 'these things' explained in a simple way. Is that not the point of the natural sciences.

I accept that university level math is required to master the higher level physics concepts, but surely the lay man can generally be afforded a rough explanation.

"Complexity is simply an excess of simplicity"

some of you physics people are no better than CBS soap queens, there, I said it.

31. Originally Posted by wallaby
Originally Posted by jambaugh
The full equation is not that's just a special case when the spatial momentum is zero, i.e. for an object at rest.
Rather the general relation is: , the mass is the square magnitude of the energy-momentum 4-vector, (with some c's in the equation to convert to energy units.)
I don't think the distinction between rest mass and inertial mass was clearly made, the total energy of a body being the product of the inertial mass and a term or being a slight rearrangement of the norm of the momentum 4-vector. If the mass in equation 1 of the quote is the inertial mass then it is as good an expression for the total energy as equation 2.
Good point and I should have been more explicit. But I think the better trend is to avoid the concept of "inertial mass" and stick to "mass = rest mass" and let the variable component of momentum-energy be called "energy".

Note that "inertial mass" is (m=rest mass), we define it because we are translating this relativistic component back to the pre-relativistic form of Newton's equation F = ma (F = 3-force, a=3-acceleration, m = inertial mass). I find far less confusion and semantic ambiguity occurs if one sticks to the relativistic format when working with relativistic theory, namely sticking to 4-vectors. One still has Newton's law F=ma but now with F a 4-force, m the invariant (rest) mass and a the 4-acceleration.

32. This is true, having just had 6 weeks of lectures on special relativity i wish the lecturer had gone with using 4-vectors. Might have made collision problems that little bit easier.

33. [QUOTE=Dou7a;277724]E=mc2 , this is the theory of einstein but the problem is i have searched about it in wikipedia but the explanation was complex so can anyone explain it to me in a simple way ?[/QUOTE

OK Dou7a, in simplistic terms Albert was demonstrating that mass and energy can be one and the same.
in a given set of circumstances.
nokton.

34. No other name evokes the emotions that Einstein does! Thats how powerful those two theories are! His greatest work was done on our understanding of light and gravity. The photo electric effect, and the understanding that gravity was a curvature of space-time rather than an etheral force, sprung man-kind forward in to a new Universe of space-time connectivity, and black holes!

35. Well, if it is General Relativity you want to understand, it can be spoken of in Layman's terms, but I doubt the math will be grasped.

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