E=MC2 Why the speed of light ?, relativity question

This is for those that really understand relativity.

I can accept very easily that mass can become energy and vice versa, but why should it have anything to do with the speed of light ?

And why should 1g of Lead produce the same amount of energy as 1g of say, Hydrogen ? the ratios of the various subatomic particles are different, so the energy they produce should be different, no? (This of course assumes that it is possible to turn both types of mass into pure energy)

Any thoughts ?

All the best

Dom

On the contrary, the speed of light is just a ad-hoc postulate (i.e. the conjecture, that is accepted without proof) in relativity theory, which can be derived from anything else. The Aether Wave theory explains the speed of light invariance by the Rayleigh wave character of Aether. The mass = energy equivalence can be derived using Lorentz transform, after than.

Just because the mass / energy equivalence .... The mass concept has nothing to do with the energy density concept, because the higher is energy density, the higher is the space convolution/compactification too and both these effects are mutually compensating itself.

Hi domdom,

Look at 2/ E = mc2 .. this might or might not help


http://forum.physorg.com/index.php?showtop...indpost&p=60398

Best wishes, C2 .

Just see them both as 1g of assorted Protons and Neutrons. And the small counting difference is the difference in Binding energy etc.


Another fun part, in a non-vacuum, transparent medium, the Speed of traveling light is slower then that of light in a vacuum. Is the E=mc2 equation than also different with reference to c? As if E = a differential Energy. But then again, Cerenkov radiation would not exist, but it does.

c is often misunderstood
light isn't the limiting factor
when you slow light everything doesn't slow.
light just so happens to travel at c in a vacuum as well the rest of the EM spectrum.
c is just the speed limit of the universe and is not medium specific. I wish they would quit calling i the speed of light o avoid the confusions... like if i slow light does E go down.. answer is NO as c isn't the speed of light it just happens to be the speed light goes in a vacuum.

Fun part..

It would be nice to say there is only one velocity of light and any of the 'slowing down' effects are due to reflections or 'something else'.

Edit.. I think Joules_Beef is saying the same thing .. only one velocity of light ..


Clearly immersing a mass of lead in water (slower light speed than vacuum) does not cause a huge release of energy so it looks like the e= m c^2 bit always works with the vacuum velocity of light (The velocity of light).

http://en.wikipedia.org/wiki/Cherenkov_effect

Cherenkov radiation involves charged particles and the way electromagnetic radiation propagates (not always at the The velocity of light) - not quite related to turning the mass into energy as such.

-C2 .

The speed of light is always the same, even when traveling through a medium. Here's something I heard in 9th grade.

Think of light traveling in a medium as a person walking through a crowded room, the person will always walk at the same speed (Ignore the small moments of acceleration[hmm... how does light accelerate? that's one I haven't heard]) And think of the people as the atoms of the medium (Let's assume the medium is made of atoms...) So the person walking through the room will stop and talk to people as he walks by them, sometimes being reflected or refracted by them.... Okay I made that part up. Basically the light traveling from particle to particle goes at 300,000 km/s but it for some reason stops at them, don't ask me why, maybe it's tired.

all electromagnetic radiation travels at c in a vacuum
true their speeds can vary in mediums
Cerenkov radiation is emitted when breaking the em barrier in a medium.


an interesting property of Lorentz and kinda shows the consistence of light..
A space ship traveling at 99%c relative to the earth.. launches another spaceship that goes 99%c relative to the first ship.. to the guy on earth, the second ship isn't going at 198%c but is instead going at 99.94%c..Lorentz always keeps the speed below c from all perspectives... nice thing about this.. is if your twin brother takes off on a ship going 99%c.. you can quickly catch him by going just slightly faster.

No, electromagnetic radiation always travels at the same speed, c. It is rather stupid if you think about it to accept the idea that electromagnetic waves travel slower in mediums.

not it isn't. That why they specify c is light(or EM) in a vacuum.. or they wouldn't specify vacuum.
speed of light in water is about 3/4 the speed of light through air.
or about 225,000km/s where c is closer to 300,000
speed of light through the air on the earth is only .03% less than c
you also work out the refraction of water based on the speed of light(vacuum) divided by the speed of light (water)
even electricity is slowed in great conductors like copper...thats why we want super conductors.
electrons can travel faster than light in water..because they have inertial mass.
EM varies through materials..
they have even slowed light to a stop..
they even think they made light go faster than the speed of light and hense the rising edge of the wave left the material before it entered.. key this is through a material with a high refractive index.

I've heard that new solution to Einstein theory has recently been found in five dimensions. Did anyone heard that too? (If this person can "present" those solutions it ll be perfect )

thanks

not it isn't. That why they specify c is light(or EM) in a vacuum.. or they wouldn't specify vacuum.
speed of light in water is about 3/4 the speed of light through air.
or about 225,000km/s where c is closer to 300,000
speed of light through the air on the earth is only .03% less than c
you also work out the refraction of water based on the speed of light(vacuum) divided by the speed of light (water)
even electricity is slowed in great conductors like copper...thats why we want super conductors.
electrons can travel faster than light in water..because they have inertial mass.
EM varies through materials..
they have even slowed light to a stop..
they even think they made light go faster than the speed of light and hense the rising edge of the wave left the material before it entered.. key this is through a material with a high refractive index.

Okay, lets say you have light traveling from 1 particle to another in space, it travels at c right? So whats the difference if the particles are only nanometers apart? All that is in between particles of atoms is space, just like the space in between the electron of a hydrogen atom in a sun in Andromeda and that of one in the oceans of Earth.

Hi domdom,

I know this is going to seem silly at first but there is nothing in the Universe other than light in the end. It is all pure geometry and energy and nothing else... This is why you can produce matter from just energy (admittedly matter and equal quantities of antimatter).

So if that is all there is... then the speed of light must be at the bottom of "everything".

Also which is heavier a pound of feathers or a pound of gold? I know... a dumb question.

Cheers

No, electromagnetic radiation always travels at the same speed, c. It is rather stupid if you think about it to accept the idea that electromagnetic waves travel slower in mediums.

The EM radiation travels at c/n, where n is the index of refraction. The photons, however, travel at c. Classically the wave slows down. Quantum-mechanically, the photons are absorbed and re-emitted.

mass is structured energy
in the universe there is only ONE energy.
The basic grains of the energy are quanta of space QS that build up cosmic space.
All subatomic particles that build up matter all and electromagnetic waves are different structures of QS.

Formula E = m x cc

shows relation between "free energy" E and "structured energy" m