speed of light?

Question

Can someone explain E=MCsquared to me I know it is energy =the speed of light x the speed of light but what units are they using, grams, kilograms, pounds or tons, and is the speed of light in miles per second or kilometres and what if we used a different time scale? Perhaps one that had 30 seconds to the minute. I don't think i'm stupid but I cannot get my head around it.

Sorry about the repetition, but my computer would not accept the question, and I kept clicking the "Submit"

Answer 1

forget the units..irrelevant..it is found experimentally that if a body is accelerated, some of the Ek gained goes into increasing its mass instead of its speed.
The equation is given by
M=Mo(1-v^2/c^2)^-1/2.(Lorentz transform)+
simple binomial expansion> M=Mo(1-(v^2?c^2)*-0.5+higher terms in v^2/c^2
> M=Mo+Mo*v^2/2*c^2
>change of mass =M-Mo=Mo*v^2/2c^2
> deltaM= Ek/c^2 (Ek=Mo*v^2/2-non rel exp)
>E=deltaM*c^2.. dropping the kinetic suffix
Basically it is telling you the conversion rate between a change in mass and the energy released..works for nuclear reactions..anti-pair annihilation/creation..and hawking radiation.
+ this equation is the result of the fact that C=constant in any moving ref frame, whereas mass, length and time have to change to follow suit.

Answer 2

I wondered exactly the same think when I was a kid.
The answer is that you can use whatever units you like but the units of M and C determine the units of E ( or vice versa ).
If M is in Kg and C in m/s/s then E is joules. A good way to visualise a joule is the energy required to lift an apple by 1m.
As an example
1g = 9000000000000 J = enough energy to lift the Eiffel tower into space. This is about as much energy as was released by the Hiroshima bomb.

The answer by grolsch is very odd. The speed at which light moves is indeed variable because almost every use of the 'speed of light' should actually read 'speed of light in a vacuum' and that is a fixed value. It is a fundamental constant of the universe and can be measured to incredible precision.

Answer 3

KITCHEN SCIENCE

You can work out the speed of light using your microwave, a 15cm ruler and a bar of chocolate.

1 IMPORTANT. Unwrap the Chocolate.
2 Look at the back of your Microwave, find the label that tells you what frequency it works at.
3 Remove the Turntable
4 Place the chocolate as close to the centre as you can
5 Turn it on for 10 second "blasts", until you see the "hotspots" where the chocolate melts.
6 Measure the distance between them
7 Multiply this distance by 2 and then multiply that figure,(the wavelength) by the frequency and you should come close to 299792458 metres per second , or the speed of light.

Now, E=mcsquared

Where e = energy, usually measured in watts or joules
m = mass measured in grammes per cubic centimetre
c = the speed of light.

Answer 4

No units and all units. E = mc squared is as much philosophical as scientific. Note that since Einstein wrote this, the speed of light (c) has been slowed down in laboratory conditions which seems to imply that it could also be speeded up. Note also that 'c' was chosen because it was a constant, ie unchangeable, yet for the equation to work it has to be multiplied by itself, ie squared. Also, whatever old Albert said, human beings cannot, yet, know the speed of light for what it really is but only as we observe it. In other words, no human timescale can affect the essential speed of light, any more than a thirty second minute would make a sprinter run slower or faster. But have you noticed how subjective time slows down on a motorway?

Answer 5

A better way of think about relativity is to imagine that the whole of spacetime is expanding at the speed of light. Anything that changes its velocity in space relative to the big bang has to undergo a corresponding change in velocity through time to balance the equation and bring the total velocity through soacetime back to c. If you go a step further and imagine that all matter is really just vortices in the fabric of space you can imagine that the spinning vortices would be stable and resist the expansion of spacetime which we then experience as gravity. I`ve got loads of this stuff but I`ve gotta feed the dogs

Answer 6

It's a matter of choosing the unit of measurement. The speed of light as measured in miles is 186, 292 miles a second. For feet per second one must know there are 5280 feet in a mile. To get the speed of light in feet per second multiply 186,292 miles a second by 5280 feet. that will give you the speed of light in feet per second. You can download what they call a conversion table on the internet and it will tell you how to convert the speed of light in kilometers per second and so on. If you used a time scale of thirty seconds to the minute that wouldn't change the speed of light per second but it would change the distance that light travels in your thirty second minute. It would be half as far.

Answer 7

Energy = M (C) squared
where (C) is a constant expressed as 186,282 miles per second or 299,792,458 m / sec so it does not matter how u express it : meters, mile, kilometers, even inchs it is always the same even for time

it does not use units at all only constants and variables

Answer 8

e = mc^2 is Joules, and m is in kg, c is in ms^-1 (meters per second) Which makes joules kg m^2 s^-2

The speed of light is 299,792,458 ms^-1

As for changing the time scale, then there'd probably be some sort of constant in the equation like this:

e = k m c^2

Or we simply wouldn't be using Joules, plain and simple.

Answer 9

Mass can be measured in kilograms (kg).

C can be expressed in meters/second (m/s).

Therefore, Energy, E = kg * m^2 / s^2

A newton is an amount of force:

1 N = 1 kg*m/s^2

Energy is force acting across distance.

E = N * m = kg*m^2/s^2

Which matches E = mc^2

Answer 10

Does this help?

http://en.wikipedia.org/wiki/E%3Dmc2