Does E really = MC^2?

Question

Is there any physical proof? How can the speed of light have anything to do with the amount of energy in an object.
The amount of energy in a given amount of mass may be very, very large, but is it really M X C X C?

Answer 1

well we can bomb hiroshima again if you think the first time was a fluke...

Answer 2

When an atom undergoes fission, or splitting, something interesting happens. When you split the nucleus of an atom which has [for sake or simplicity] a mass of 1, the resulting particles' [after the split] total mass does not total 1. Where did the mass go? Did it just disappear? No, it was converted into energy. At what rate did it get converted? c^2. Energy and mass are covariant. The first time this was observed in the lab and measured was shortly after Fermi conducted the first sustained fission chain reaction experiment underneath the racquetball court. It was an experiment conducted by [mother and son team] the Joliet-Curies. When they measured the result of their fission, they found less mass than expected but an energy yield of approx 200 million eV. This is the amount predicted by Einstein's equation. This is also much more energetic than burning like in a fireplace. The burning [or oxidation] of a carbon atom yields about 4 eV.
This was all possible by Chadwick discovering the neutron. One must use neutron to split the nucleus since they are neutrally charged and can get by the atom's electromagnetic force barrier. If one tried to use electrons without enough kinetic energy, they would be repelled by electron cloud in the target atom. Same for protons which would be repelled by the protons in the target nucleus.

Oh yeah, and light is part of the electromagnetic spectrum. So are all forms of radiation. Radiation is energy. All forms of electromagnetic radiation propigate at c [in a vacuum]. Form some radiation it takes more to be stopped since the transmission particles are so much more energetic than light photons--which can be refracted, reflected or stopped by things like water or even the human body. It's kind of a good thing that the body doesn't stop all radiaiton like X-rays. It's a bad thing when considering things like gamma rays. But, again they are all part of the spectrum and all travel at c.

Answer 3

Here's another imponderable: how can the speed of light have anything to do with the propagation of gravity? Yet the current understanding of gravity is that its field travels through space at the speed of light.

If you run the numbers, one gram of material, if converted completely to energy in the form of electricity, would supply enough juice to run the City of Los Angeles for about 6-1/2 hours.

I agree with other answerers who noted that only a small percentage of this energy is tapped by either nuclear power or nuclear bombs. However, when, for example, uranium is used in a nuclear power plant to generate heat, the "spent" fuel ends up weighing less than the original uranium. How much energy was produced? EXACTLY mc^2, where m is the difference in mass between the starting and ending fuel loads. (A large amount of this energy is lost inside the power plant, much of it out of the cooling towers.)

Added note: I forgot to mention this wonderful book, available as hardcover, paperback, eBook, or Books on Tape or CD:

E=MC^2: A Biography of the World's Most Famous Equation, by David Bodanis.

It will get you comfortable with the concepts involved even though it's essentially math-free. It contains exciting stories about the heroes of 19th- and 20th-century physics and patiently explains the derivation of the equation.

I've learned that the PBS program on Einstein and E=mc^2 is based on Bodanis' book. Regarding the squaring of c in the equation, the book, and program, details the contribution of Emilie du Chatelet, who back in the 1740's debunked Isaac Newton's notion that kinetic energy is proportional to the speed of an object, but showed instead that it was proportional to the square of the speed. The squaring of velocities in calculations of energy has been with us pretty much since then.

Answer 4

Yes, there is physical proof. In fact, in 2005, the centennial of Einstein’s great year, a team made the most accurate test yet of his equation. They measured the tiny change in mass of radioactive atoms before and after the atoms emitted gamma-rays. And they measured the energy of the rays. The missing mass times c² equalled the energy of the rays to within 4 hundred-thousandths of one percent.)

I agree with you; I think it's pretty incredible that mass and energy are related to each other by a third factor that really doesn't seem to have much to do with either. That's one of the reasons I really like physics - sometimes it seems pretty close to magic - time dilation, matter-energy equivalence, strange action at a distance. But all proven true in the lab.

Answer 5

That's Einstein's famous formula for the amount of energy in matter. I call it the atomic energy formula. Most people look at the atomic energy formula, and say, "Wow, that must be a lot of energy!" But do they understand the formula? Do you? Do you know that "c" represents the speed of light? If you're like most people, you have never truly understood the meaning of this formula. You'll be happy to know the formula is easier to understand than you might have thought.
Kinetic Energy of a Car Going 60 MPH
Let's use the kinetic energy formula to see how much energy it takes to get a 1500-pound car moving at 60 mph.

1/2 * 1500 * 60 * 60 = 2,700,000.

So the kinetic energy of the car is about two and a half million. Two and a half million what? Why, two and a half million square mile pounds-of-mass per hour per hour. energy can be measured in "square mile pounds-of-mass per hour per hour". Sometimes it's easier to just accept some things.

Answer 6

This is the value of rest mass energy. For everyday use this means little. The most meaningful way to understand it is to think about the change in mass when nuclear reactions take place. The mass change is very little (mass defect)... it is that mass, the mass defect, that is the M in Einstein's equation. It is correct.

Answer 7

No, it doesn't.


E=mc^2/(1-v^2/c^2)

That's the whole equation. E=mc^2 does not take into consideration an increase in energy based upon field intensity. ^^

Answer 8

It used to but then some 11 year old Japanese kid messed it all up!

Relativistic mass theory is refuted with E=Mq2T-1second.

The point is that as we grow and learn more about our galaxy, our theorys and even our laws change to fit the new knowledge. Eventually we may come up with irrefutable laws but I am sure that will be a very long time in the future.

The best we can hope for now is to study enough to give the right answer on a test and after that study enough to keep up with current changes and trends.

Answer 9

Hi. Yes, every test and experiment (and bomb) confirmed this value. The Hiroshima bomb converted 3 grams of matter to energy.

Answer 10

Nope, The Einman came up with that theory. If alive today he probably would have taken into account other variables to arrive at a more accurate answer. His formula is to simple.

Answer 11

Einstein was just pulling your leg; E actually equals watermelons.