what does light have to do with the equation E=mc^2?

Question

I UNDERSTAND EVERYTHING ELSE BUT WHAT DOES LIGHT HAVE TO DO WITH THE EQUATION? AND WHY IS IT SQUARED? Plz help and include sources

Answer 1

I'm really glad you asked this. I'd always wondered myself but didn't take the time to quench my ignorance... sigh.

Did a bit of Googling just now and turned up a whopper:

Einstein multiplied mass times the speed of light, on the premise that if something is turned into energy, it will thenceforth travel at light speed, because that's the speed pure electromagnetic energy travels at.

Now, the energy content of anything that is in motion, I believe, is obtained by squaring its velocity. The author of the below link gives the example that an object moving 4 times faster than another object of the same mass, has 16 times the energy of the slower object.

This is *awesome*. See the genius of it? Einstein is simply saying here, "Mass equals energy."

Don't read the equation like I used to, that "mass equals energy because of..." some mysterious mechanism related to light speed.

I had always been reading it wrong. This reading didn't follow the reasoning implicit in the nature of mass and energy.

By taking into account the nature of pure energy and its motion, the equation further predicts how much energy there is in a unit of mass. But this is almost a secondary statement of E=MC^2.

Just incredible. It's one thing to venerate a man because everyone else does... but to see it for yourself is another level entirely.

Answer 2

The letter c stands for the velocity of light. This equation is a consequence of Einstein's Special Theory of Relativity, which describes the dynamics of objects moving at very high speeds. Einstein showed that as an object is accelerated toward the speed of light, its mass increases so that further acceleration becomes progressively more difficult. The accelerative energy shows up in the object as increased mass rather than increased kinetic energy.
As for why the c is squared, firstly it's a consequence of the rest of the mathematics, and secondly, if it were not squared the units of measurement would not work right.

Answer 3

The standard equation for the conversion of mass to energy is E=mv^2. In metric, applying mass in kilos and velocity in meters per second , it gives the number of joules of kinetic energy within a speeding object (you can calculate the energy of an impacting asteroid as its kinetic energy is converted to blast energy on hitting the Earth).

E=mc^2 is simply a variation on this high school physics energy equation, where nuclear processes convert all the mass of an object to radiation energy, and of course that radiation has the speed of light.

Note that though we call c light speed, in general terms it is the velocity of the whole spectrum of electo-magnetic radiation, of which light is just a small fraction of the spectrum.

Answer 4

Well, the constant "c" is the speed of light (3x10^8 m/s, I think). I don't know why it's squared, but I'll post a link from wikipedia in the sources. You can read more yourself.The article is E=mc^2.

Answer 5

It is used as that is the speed of any radiation, not just light.
All radiation travels at that speed ina vacuum, even gamma rays, the most powerful radiation.
The amazing thing is, that it is squared at a very small measurment level, the cm, Thus 30,000,000,000^2
Off hand I do not know why it is squared, but it appears that the formula has been experimentally verified.
The bombs dropped on Japan, converted about 0.7 grams into energy. That's about 0.025 oz (2.5% or 1/40th of an ounce)

Answer 6

E=mc2 is one of the most famous equations in physics, even to non-physicists. It states a relationship between energy (E), in whatever form, and relativistic mass (m). In this formula, c², the square of the speed of light in a vacuum, is the conversion factor required to formally convert from units of mass to units of energy, i.e. the energy per unit mass. In unit-specific terms, E (joules) = m (kilograms) multiplied by (299792458 m/s)2.

Answer 7

well in this equation, light is very important. c is equal to the speed of light, which is a constant. E is equal to energy, which can often be transferred through light waves or a similar source.

Answer 8

In this formula, c², the square of the speed of light in a vacuum, is the conversion factor required to formally convert from units of mass to units of energy, i.e. the energy per unit mass

Answer 9

The formula, E=mc^2 was derived from other conclusions which Einstein reached while working on Special Theory of Relativity. So i will give u bit of a background, though i cant show u the derivation here ! So please bear with me........

Einstein began his theory of Relativity taking into consideration the the fact that the speed of light is invariant to all observers irrespective of their frame of reference. This was not his conclusion, but had already been experimentally demonstrated by Michelson and Morley. At the beginning of Special Relativity Einstein was working on Transformation Equations, that is how measurement made in one frame of reference can be transformed into measurement made with respect to another. In relativity its called Lorentz Transformation equations, in honour of Lorentz who first worked in this direction. It is while working on these equations that Einstein had to introduce a constant k = 1/square root of (1-V^2/c^2). The reasons for introducing this constant cant be discussed here except to say he had to generalise certain equations.
Now, after building these transformation equations, he realised that Length (space), Time, Mass, vary from one frame of reference to another. And he worked out the transformation equations for each of t. And in each of these transformation equations, the constant mentioned above was used.
Now the formula for the variation of mass turns out to be
m = m1 . k , where is he constant mentioned above. Or alternately, m = m1 / square root of (1-V^2/ c^2) ,
where, m1 is the rest mass as measured in the frame which is at rest with respect to observer and 'm' is the variation in this mass as measured in a frame moving with a velocity 'v'. Notice that 'm' is always greater than 'm1' the rest mass. Now notice that this formula has C^2 as one of its components.

It is from this formula that Einstein derived the formula E=mc^2. First he built the equation for the work done in moving a certain mass m through a small distance say..dx. Now, workdone W= Force x Distance. And Force = Mass x Acceration. But unlike in classical physics, here mass is not invariant. So while differentiating this equation both acceleration and mass is to be considered as variables. Thus he had to use the formula for the variation of mass which he had constructed. Workdone is closely related to Energy. And they have the same unit of measurement, joule. It is from the formula for workdone over a small distance in moving a mass 'm' that he arrives at E=mc^2. Hence what u see here is a direct consequence of the theories and formulas from which it is built and cant be explained separately. And in constructing this formula he had shown how Energy is related to Mass. And also that they are interconvertable and stem from a single quantity hence forth refered to as Mass-Energy which is conserved. Though mass and energy are not seperately conserved. And this was ofcourse a revolutionary idea.
I hope this explanation satisfies u.

Answer 10

Energy required to travel at c (186282 mps) equals the mass of the object times 186282 mps (lightspeed) squared.
This sets lightspeed as the universal speed limit. work out the equation for yourself and you will see that in order to travel faster than c , the fuel required to produce the energy needed for propulsion would turn your ship into an infinitly hot, dense mass.
At one point, that hot, dense mass would collapse in on itself forming a black hole.
Hope this helps ;D