Thread: m=E/c^2 ?

If one can create energy out of mass, can one create mass out of energy?
how much energy would, theoretically an atom be equvalent to?
If we where to convert energy into mass, what kind of mass would we gain?

I've tried to answer these question based on wikipedia saying a letter weighing 1g is equvalent to 27 megatons of TNT. The answeres where so obsure that either Im claculating wrong or the numbers in wiki are too rounded-off.

Where in Wikipedia did you find that?

Originally Posted by miomaz

If one can create energy out of mass, can one create mass out of energy?
how much energy would, theoretically an atom be equvalent to?
If we where to convert energy into mass, what kind of mass would we gain?

I've tried to answer these question based on wikipedia saying a letter weighing 1g is equvalent to 27 megatons of TNT. The answeres where so obsure that either Im claculating wrong or the numbers in wiki are too rounded-off.

1) Yes, you can theoretically create mass from energy, and that is what is believed to have happened in the Big Bang. Mass can come from a photon-photon collision if there is sufficient energy to create a massive particle. You won't get an atom from such a collision but rather a particle-antiparticle pair.

2) The energy of an atom depends on the atom, and specifically on the mass of the atom

3) You can do the calculation for the energy of 1 g of mass yourself using and the fact that a megaton of TNT is equivalent to Joules.

If you enter "1 gram *c^2 in joules" into Google calculator you get:

1 gram * (c^2) = 8.98755179 × 10^13 joules

And using Doctor Rocket's conversion factor that's

(8.987 * (10^13)) / (4.184 * (10^15)) = 0.0214794455 megatons, or 21.4 kilotons.

Originally Posted by DrRocket

You won't get an atom from such a collision but rather a particle-antiparticle pair.

Sorry, but what that mean?

Originally Posted by AbuYusuf

Originally Posted by DrRocket

You won't get an atom from such a collision but rather a particle-antiparticle pair.

Sorry, but what that mean?

Hmmmmm.......

That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

However, in simple laymans terms, yes it is possible to create mass from energy but you need a lot of it in a small enough space. Luckily the strong nuclear force (which binds quarks together inside protons and neutrons follows an inverse square law - that is the force between the particles gets STRONGER as the particles are moved further apart (unlike other forces such as magnetism and gravity) Eventually if you move quarks far enough from each other then what will happen is that the force will become so strong that the energy will collapse on itself and form another particle (another quark infact) - and thats why you wont find single quarks floating around the universe - they have to exist at least in pairs.

And to the OP; dont take everything you find in wikipaedia as read or wholly correct; remember wikipaedia is an open-source encyclopaedia so anyone can add anything. although yes the general gist of it is correct - from a small amount of mass you get a large amount of energy.

[quote="leohopkins"]

Originally Posted by AbuYusuf

Originally Posted by DrRocket

You won't get an atom from such a collision but rather a particle-antiparticle pair.

Sorry, but what that mean?

Hmmmmm.......

That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

quote]
Well, they move away from each other.

[quote="thyristor"]

Originally Posted by leohopkins

Originally Posted by AbuYusuf

Originally Posted by DrRocket

You won't get an atom from such a collision but rather a particle-antiparticle pair.

Sorry, but what that mean?

Hmmmmm.......

That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

quote]
Well, they move away from each other.

No - they dont move away from each other. They have an opposite charge therefore they attract and the end result is annihalation.

Originally Posted by leohopkins

Originally Posted by AbuYusuf

Originally Posted by DrRocket

You won't get an atom from such a collision but rather a particle-antiparticle pair.

Sorry, but what that mean?

Hmmmmm.......

That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

Gamma rays are photons. And if you have photons with high enough energy colliding to form massive particles those particles occur in particle/anti-particle pairs.

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

[quote="leohopkins"]

Originally Posted by thyristor

Originally Posted by leohopkins

Originally Posted by AbuYusuf

Originally Posted by DrRocket

You won't get an atom from such a collision but rather a particle-antiparticle pair.

Sorry, but what that mean?

Hmmmmm.......

That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

quote]
Well, they move away from each other.

No - they dont move away from each other. They have an opposite charge therefore they attract and the end result is annihalation.

After the pair production, the electron and positron move away from each other in an angle of 180 degrees.

That's because they possess the excess energy of the initial photon that remains as kinetic energy after their formation. If this is too small, they annihilate immediately again.

Originally Posted by Dishmaster

That's because they possess the excess energy of the initial photon that remains as kinetic energy after their formation. If this is too small, they annihilate immediately again.

Thats much better explained.