One Hundred Years of E=MC2 408
Eric Ward writes "To mark the one hundredth anniversary of Einstein's
famous equation, E=mc2, NOVA has gone live this month with a Web site that features exclusive content and podcasts from ten of the worlds top physicists. This once-in-a-lifetime gathering of top scientists such as S. James Gates, Jr., Brian Greene, Neil deGrasse Tyson and Nobel Laureate Sheldon Glashow simplify what the equation means to our world today and the effect it has had on their careers. NOVA online also details how Einstein grappled with the implications of his revolutionary theory of relativity and came to a startling conclusion: that mass and energy are one,
related by the formula E=mc2.
Viewers will also find lesson plans through the
award-winning NOVA Teacher's Guide and a special
library resource kit."
Re:Its not E=MC^2 (Score:2, Informative)
Re:What if E = mc^2.0000000001? (Score:2, Informative)
Perhaps we will discover that the E deviates from mc^2 when temperatures are very high or very low or m is very large or magnetic fields are especially strong
Interestingly, these conditions provide a good verification of the relationship between energy and mass. High energy photons (no mass) in extremely strong magnetic fields (e.g. near massive stars or in particle accelerators) lead to the creation of electron/positron pairs (with mass).
Re:One Hundred Years of E=MC2 (Score:1, Informative)
½mv^2
Re:What did E=MC2 give us the past 100 years? (Score:5, Informative)
All this business of E = mc^2 "giving us the nuclear bomb" is another example of newspaper pap-science. There's far more to a nuke than computing the mass defect.
The whole idea is a staple of Relativistic kinematics which has been verified in collider experiments, etc., etc.
You can define relativistic stuff in less than four dimensions (e.g., one of space and one of time). Take an electron-positron annihilation into two photons. A proper treatment requires quantum field theory, where mass can be understood (in one way) as a parameter constraining the dynamically allowed momentum-energy configurations of the physical ("on-shell") fields. It's [probably] not right to think of electrons as little dots of mass.
Again, you need to consider quantum field theory to [begin to] answer these questions.
Re:Plagiarist? (Score:2, Informative)
years ago they were pushing naltrexone for blocking the effects of drugs like opioids and many stories talked of its completely safe use and ability to fix drug users in just days or weeks and prevent any relapses, and was an immune system miracle drug that beat HIV and AIDS.
then after naltrexone was approved nexus printed many articles afterwards talking about the mind control use of naltrexone which was being sneaked in the back door by making drug users use it first because that wouldn't be rejected by society even though there is claimed all evidence to it being unsafe.. claims now are the whole population will be on naltrexone and under mind control within decades.
the position switch might sound like nexus is dual personality but really it just cmoes about because they feel the same information wants to be free as many other people but will work towards that by publishing information nobody else will publish.
whether that information is bollocks matters not it will be published anyway.
E = mc^2 is Not Einstein's Discovery (Score:3, Informative)
Robert A. Herrmann
1. Introduction
It appears that some scientists have not received the proper credit for significant discoveries for which they have priority. However, without specific and irrefutable information, it is not possible to give convincing reasons why these individuals have been denied recognition and why others have been given credit for their scientific discoveries. In 1996, I was asked whether certain aspects of General Relativity were originally formulated by Einstein or Hilbert. (Hilbert presented the gravitational equation(s) prior to Einstein.) The questioner said that he knew very little about Einstein's achievements except for such things as "E= mc^2." I answered his question relative to the Hilbert verses Einstein controversy but I neglected to discuss the more easily explained E = mc^2. What follows in this short article shows exactly who developed the idea that "radiation" can be characterized as having an apparent mass and that it was not Einstein in his 1905 paper. Except for the last remarks on Olinto De Pretto, this article is concerned mostly with "radiation" and its relation to E = mc^2.
read more... [serve.com]
Michael. [michael-forman.com]
2 years too late (Score:2, Informative)
Rory Carroll in Rome
Thursday November 11, 1999
Guardian
The mathematical equation that ushered in the atomic age was discovered by an unknown Italian dilettante two years before Albert Einstein used it in developing the theory of relativity, it was claimed yesterday.Olinto De Pretto, an industrialist from Vicenza, published the equation E=mc2 in a scientific magazine, Atte, in 1903, said Umberto Bartocci, a mathematical historian.
Einstein allegedly used De Pretto's insight in a major paper published in 1905, but De Pretto was never acclaimed, said Professor Bartocci of the University of Perugia.
De Pretto had stumbled on the equation, but not the theory of relativity, while speculating about ether in the life of the universe, said Prof Bartocci. It was republished in 1904 by Veneto's Royal Science Institute, but the equation's significance was not understood.
A Swiss Italian named Michele Besso alerted Einstein to the research and in 1905 Einstein published his own work, said Prof Bartocci. It took years for his breakthrough to be grasped. When the penny finally dropped, De Pretto's contribution was overlooked while Einstein went on to become the century's most famous scientist. De Pretto died in 1921.
"De Pretto did not discover relativity but there is no doubt that he was the first to use the equation. That is hugely significant. I also believe, though it's impossible to prove, that Einstein used De Pretto's research," said Prof Bartocci, who has written a book on the subject....
Re:Ok guys... educumacate me (Score:2, Informative)
Relativity : The Special and the General Theory
By Albert Einstein
This is written for the technically inclined layman. I read it and since then I've been life of the party. It really did make things much more clear - like what does flexible of spacetime have to do with the speed of light? It's all in there!
Did it in 1932 (Score:3, Informative)
Here's the link you need to CD Anderson's 1932 experiment [physlink.com] using gamma rays
Re:serious question (Score:1, Informative)
Lets go with a fairly common unit system for relativitic physics.
Let c = 1
so our units of length are a light second and out unit of time is a second, you could also pick light-years and year, light-milenia and miliseconds dosen't matter...
Try this: let's try doing the unit conversions before and after. I'm going to use CGS (centimeters, grams, seconds) and MKS (meters, kilograms, seconds) If you want to change time units you can repeat this, you are also welcome to use parsecs, months (30, 31 or 29 day), and slugs if you wish.
Let m = 23 kg or 23000g
Let c = 3x10^8 m/s or c = 3x10^10 cm/s
Lets calculate E
E = 23kg * (3x10^8 m/s)^2
E = 23*3*3*10^16 * kg*m^2/s^2
E = 207x10^16 * kg*m^2/s^2
Now for CGS
E = 23000g * (3x10^10 cm/s)^2
E = 23000*3*3*10^20 * g*cm^2/s^2
E = 207x10^23 * g*cm^2/s^2
Now lets see what 207x10^20 * g*cm^2/s^2 is in MKS:
207x10^20 / (100^2 * 1000)
207x10^20 * 10^-4 * 10^-3
=> 207x10^16
Low and behold! They are the same. Repeat with any set of units you wish (even make up one, like a pi-meter or a pi-year or a e-second)
Re:Plagiarist? (Score:3, Informative)
I guess its just
Re:Plagiarist? (Score:5, Informative)
Ummm, no. Einstein's NP was for his paper on the photoelectric effect. Read your source again.
Re:serious question (Score:3, Informative)
it is in m^2kgs^-2
Speed is also a derived unit.
it is in ms^-1
So when you pick a definition for time and distance, everything matches up.
Re:serious question (Score:5, Informative)
I think you are making the mistake that, for example, a 4-slice pizza is smaller than an 8-slice pizza, because, as everyone knows, 4 is less than 8. However, the pizzas are exactly the same size, it is just that the slices are larger in a 4-slice pizza.
Is there some science behind the selection of the units involved that allows this equation to be so simple, or are we to believe that some serendipitous magic just allows this to be an exact equation and the units somehow just happen to match up?Yes, there is a very challenging derivation of this simple relationship. It is just math, and it is not magic. I won't do the derivation, but I will show that the units do, indeed, make sense:
Energy is a force acting through a distance: F x d
Force is a mass undergoing an acceleration: F = m x a
Acceleration is a change in velocity over a change in time: A = deltaV/deltaT, whose units are length/time x 1/time. Let's use metric. That would be m/s x 1/s.
Substituting the units back into the general energy equation, we get:
E = F x d = m x A x d = kg x (m/s x 1/s) x m. If we pair the 1/s with the meter from "Force acting over a distance" The units are:
E = kg x (m/s) x (m/s), which are the same units as Einstein's famous relation. So, yes, the units do make sense, it is not serendipitous that this works out, and the reason it is so famous is because it is so simple.
Re:serious question (Score:5, Informative)
E = mc^2 holds true no matter what units c is expressed in - as long as the units for energy, mass, and c are consistent.
If you say c is expressed in meters/second, and m in kilograms, then energy must have the units of [kg*m^2/s^2] which we also call Newton-meters or Joules.
Just to confuse you further: sometimes we choose our units such that c=1! In this case, E = mc^2 becomes just E = m. Energy is mass.
Numbers in physics are just convenient ways to express a measurement; they are not of numerological significance (well, maybe the fine structure constant...).
Check out http://en.wikipedia.org/wiki/Physical_unit [wikipedia.org] if you have more questions on the units.
Plagiarism is at least better than bullshit (Score:4, Informative)
To begin: Wolfgang Pauli postulated the neutrino, not Einstein.
Next: Whatever one concludes about the validity of Eddington's solar eclipse experiment, the predictions of General Relativity have been tested and proved out in hundreds, if not thousands, of repeatable and rigorous experiments since then.
And Next:
This quote falls somewhere between the irrelevant and a non-sequitur. Thanks for sharing man--but what does it mean? No physicist takes cold fusion seriously, and autodynamics is a competing theory to General Relativity, for which Richard Moody, Jr. is clearly a shill.
At the end of the day, it doesn't matter whom it was that provided the first, or the first accurate, derivation of e=mc^2. It could have been Einstein, Poincare', or William goddamn Shakespeare, for all I care. What matters is that both Special and General Relativity have withstood an awful lot of testing over the last century, and stood up well under that onslaught.
The autodynamics camp also seems to believe that Special Relativity is used in radioactive decay calculations, and I could have sworn that Quantum/Statistical Mechanics holds sway there....
Re:Plagiarist? (Score:5, Informative)
Not really. Poincare did do a lot of the interesting math, following on from Lotentz, that provides a lot of the mathematical foundations for relativity, but what he didn't do was redefine time. Poincare still viewed the different time in the calculations as a sort of "local time" which was in a sense merely a mathematical fiction required to make the calculation go through. Poincare still believed in the ether, and thus an absolute referene frame and an absolute time. It was Einstein who, with his observations about the very nature of time being relative, did away with a ficntional "local time" and an absolute reference frame. In Einstein's view there was no true reference frame and all time was "local time" - local to the observer. The effects on time were thus not a mathematical fiction, but a physical reality. It was this observation and new conception of time that Einstein is highly regarded.
That does not, of course, in any way diminish Poincare's work - and he did a great deal of work besides just that relating to relativity (he is the father of algebraic topology for instance). Certainly Poincare deserves a little more recognition for his great achievments than he gets outside of the mathematics community. Misrepresenting Einstein's achievements is not the way to give Poincare his due credit however.
(As a side note, more recognition should probably also be given to David Hilbert, who did a lot of the pure maths required to lay the foundations of General Relativity).
Jedidiah.
Re:What if E = mc^2.0000000001? (Score:4, Informative)
Bzzrt. Wrong answer. Motion is relative, acceleration is not. Rocket Twin accelerates and decellerates to leave and come back. He will always be younger at the end.
Re:It is E=mc^2 (Score:3, Informative)
People like it because many equations in mechanics are nonrelativistic, such as p=mv, F=ma, and ironically, E=mc2, and the concept of "relativistic mass" makes them work out again if you interpret the "m" as being a function of v: m="m0"/sqrt(1-v2/c2). In fact that is how the concept of "relativistic mass" historically became popular and stayed popular. People wanted to extend the Newtonian laws of mechanics that they were already familiar with, and since we still teach Newtonian mechanics to beginning students in physics before moving on to relativity, we introduce this funny concept of "relativistic mass" as a hack- so that the Newtonian equations are still valid. Unfortunately the Newtonian equations are much less useful when m is no longer a constant but becomes a function of v. If you continue to make a distinction between "rest mass" and "relativistic mass" you will eventually get confused.
Life is much easier when m is a constant. Just switch to the relativistic forms of the equations: p=mv/sqrt(1-v2/c2), F=dp/dt, and E2=m2c4+p2c2. Forget about this "relativistic mass". Rest mass is all the mass you need.
Re:What did E=MC2 give us the past 100 years? (Score:3, Informative)
Re:Happy 100th (Score:2, Informative)
(E^2) = (m^2)*(c^4) + (p^2)*(c^2) (Score:4, Informative)
[PEDANTIC]
For things like photons that have zero rest mass
E = m0*c^2 / sqrt (1-(v/c)^2)
Doesn't work so well... By using the following:
(E^2) = (m0^2)*(c^4) + (p^2)*(c^2)
Now photons (which by definition are moving and have momentum) can have kinetic energy associated with them without having to divide zero by zero (since photons travel the speed of light v/c = 1 and the denominator is zero in your equation).
[/PEDANTIC]
Top scientists? (Score:1, Informative)
Re:What did E=MC2 give us the past 100 years? (Score:5, Informative)
What did E=MC2 give us the past 100 years?
It's a fact (approximately) about the nature of the universe. It doesn't need to give us anything. What did the discovery of the planet Neptune do for us? Nothing practical, but I think knowledge is worth seeking for its own sake.
What I think is more useful from E=MC2 is the idea of relativity. It is true, not just for science, but for almost every field of study.
If by "the idea of relativity" you mean, roughly, "there are no privileged inertial frames of reference", then I have a hard time imagining what bearing that idea has on, say, art history, or comparative religion. If you just mean that "everything is relative", then I'd say that your idea of relativity has very little to do with Einstein, and is probably too vague to be much use in any other field, either.
Re:What did E=MC2 give us the past 100 years? (Score:3, Informative)
In chemical reactions, the amount of mass converted to energy is very small and nearly impossible to measure, but that's not the point.
Example: To heat your house, you use on order of 1000kWh per month, obtained by burning natural gas. 1000 kWh = 3.6 * 10^9 Joules. E=mc^2, solving for m: 3.6 * 10^9 J / (3 * 10^8 m/s)^2 = 4 * 10^-8 kg =
My credentials: I'm a graduate student in physics at the University of Minnesota.
Re:Timing (Score:3, Informative)
I don't personally use the word "accuse", but he bears some responsibility for the events of 60 years ago, and for the nuclear arms race that followed.
Re:Timing (Score:3, Informative)
The fact that the letter itself was essentially a warning that the Germans were probably already pursuing it (which they were)indicates that the events were already in motion. Einstein felt a great deal of guilt over that letter, but frankly it would have happened either way. Szilard, Teller, and Wigner basically goaded Einstein into writing that letter based on a leak by Bohr that fission had been achieved, opening the door to possible fission weapons. At that point, the cat was essentially already out of the bag. Szilard himself actually drafted the letter-- Einstein only signed it. Clearly, had Einstein refused, they'd have found someone else to sign it. They only needed a name on the letter well known enough get the president's attention.
So that's it!! (Score:3, Informative)
A few years ago the National Library in Canberra had an extremely popular exihbition called "National Treasures" or something like that. It was a collection of many historical and influential works like ancient maps, the original lyrics to "Yesterday" by Paul McCartney, and other incredible things I've forgotten about. Included amongst them was Einstein's original paper on relativity open at the famous equation E=mc^2.
A German friend of mine went and saw it, and when he read that page he laughed because Einstein had written (in German) a long explanation concluded by 'this can be aproximated by the equation E=mc^2'.
We both hoped that all the physicists around the world knew that the equation wasn't acurate :)
Re:Timing (Score:3, Informative)
I don't want to get all Voltaire on this, but all things considered it worked out better than it might have. If Heisenberg hadn't botched slow-neutron diffusion path (and hence, critical mass), the Nazis might have had a practical U235 or PU239 warhead before anyone else. As you say, no one was going to un-invent nuclear fission as a weapons explosive; Einstein's own words [aip.org] indicate that the only reasonable way to excuse the US's creation of nuclear weapons was to prevent the Germans from doing so first, creating "...inconceivable destruction, and the enslavement of the rest of the world..."
Re:What if E = mc^2.0000000001? (Score:5, Informative)
Velocity causes the time and distance dilation yes, but the accelleration is what breaks the symmetry between the two.
While twin two is heading away from twin one, you can't say who's older - From Twin One's perspective Twin Two is aging slowly, and From Twin Two's perspective Twin One is aging slowly. It's just as legitimate to say that Twin Two is stationary and everything else is moving around him. It's the fact that he _turns around and comes back_ that breaks the symmetry between the two frames of reference and allows you to say that he is in fact the younger one.
You've covered the part about how the second twin is able to see himself covering the distance in that time, but ignored the fact that while he is not accelerating, the frames of reference are relative and that you can just as easily say the _other_ twin is aging slowly. In short, you ignored the principle of relativity. :)
Just wanted to point out... (Score:2, Informative)
Re:serious question (Score:3, Informative)
If E is in Joules and m is in kg, c would have to be in m/s for the equation to work. Otherwise you'd need a conversion factor. That's all units are, attached labels that assume you're being consistent throughout the equation.
No one has gotten it right yet. (Score:1, Informative)
It is somewhat straightforward to derive E=mc^2 from Maxwell's equations, just as Fitzgerald derived the correct equations for the contraction of a moving object in its direction of motion. But the key, the big thing, that Einstein did was not just derive by rote an equation, but assign consistent physical interpetations to those equations and make some pretty bold predictions. He put the thing together.
For instance, many people keep saying "E=mc^2" means that matter and energy can be "converted" from one to another. THat is actually incorrect - the MEANING of the equation is that the TOTAL ENERGY CONTENT of a system can be derived by noting its resistance to changes in motion as a result of applied force; i.e. its mass. In other words, the MASS of an object, as measured objectively, describes the TOTAL ENERGY CONTENT of that object as per E=mc^2. Or, put more simply, a boiling pot of water has slightly more mass than the exact same pot at room temperature. E=mc^2 can be shown to be a consequence of Maxwell's laws; Einstein's boldness was in asserting that ALL forms of energy, not just electromagnetic, are imbued with mass (a resistance to changes in motion) in proportion to the amount of energy within. His general theory of relativity tied this idea of inertial mass with gravitaional mass, by again boldly asserting that they are the same thing; this is by no means obvious (Eotovs experiments back it up to 10 significant figures, tho). And neither gives a clue about how to extract nuclear energy; all it says is that objects have an internal energy as evidenced by the fact they have mass; accessing that energy is a completely different matter.
Re:Plagiarist? (Score:3, Informative)
Not really. In the Nobel prize for physics is almost always given for something specific that a person did. In Einstein's case [nobelprize.org] it was awarded for "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect".
Most of the other physics prizes are just given "for his discovery/demonstration/development of X"