What does energy=mass times the speed of light times the speed of light itself mean?

Question

e=mc2

Answer 1

As Ina C said.  It is the energy required to accelerate a mass ( m ) from 0 to the speed of light ( c ), in a vacuum.

It is also why people say it is impossible for man to achieve the speed of light.  It would take more energy than we know how to make, and squish the man.

m = 90 kg (200 lb) man

c = 3.00E+08 m/s , the speed of light in a vacuum

c² = 9.00E+16

E = m * c² = 90 * 9.00E+16 = 8.10E+18 joules

to accelerate a 90 kg man to the speed of light (in a vacuum)

I was a little sleepy and previously had newtons instead of joules for the units of E.

I hope José Frink, feels better soon.

Answer 2

E=mc^2 as the equation reveals relates energy with mass

This is an equation to calculate the energy of particles at relativistic speeds. At v << c, i.e., for particles moving less than the speed of light, this reduces to the common equation for kinetic energy E = 1/2 mv ^2

Answer 3

if you destroy completely a mass m in kilograms you obtain an energy in joules = equal to the mass *9*10^16 in joules

Answer 4

Ina is incorrect. If this equation had anything to do with the kinetic energy of a Relativistic body, then it would involve the speed of that body, which it does not.

This is an equation that describes a particle at rest. It means that at rest, there is an amount of energy E = mc^2 that can be liberated by destroying the mass. This is what happens in a nuclear bomb, for instance. A small amount of mass is destroyed and converted into a large amount of energy.

For a body in motion, the correct equation would be E=γmc^2, where γ is the Lorentz Factor, γ=1/√(1-v^2/c^2). It is this equation which Taylor expands to E = mc^2 + 1/2 mv^2 + ... for slowly moving (v << c) bodies.

EDIT: Mr. B is totally, completely, inexcusably wrong. The number he gets is the amount of energy (in JOULES, not in Newtons, as he claims) that would be liberated if the 90 kg man were completely annihilated and converted into energy. It is NOT the amount of energy (and certainly not force!!) that would be required to accelerate him to c. It would, in fact, accelerate him only to 0.866c as given by the correct kinetic equation, E=γmc^2. In fact, NO amount of energy can accelerate a body to c, ever. We routinely give particles kinetic energies far in excess of mc^2 in particle accelerators, and none of them ever reach a speed of c, ever.

And Mr. B. claims to be a physics teacher. It is inexcusable, because he is muddying the waters and this is not a controversial topic. Anyone versed in physics should know the answer to this question. It is "teachers" like him that require physics professors like me to tell students that everything they learned in high school is wrong.