Einstein's theory of special relativity states that mass and energy are interconvertible . we know of mass being converted with energy as in the case of nuclear bombs , but what we may not be to familiar with is that the reverse is also possible .


Pair production


Pair production is the conversion of photons to an elementary particle and its anti particle .

For example , photon to electron and positron.

Photons are chargeless , hence , they produce both a positive and a negative particle .

0 = + 1 - 1

The photons must be close to an atomic nucleus for this process to occur

The reason is that pair production can t happen in a vacuum is that the law of conservation of energy and the law of conservation of momentum can not be conserved silmutaneously .


Law of conservation of energy.


Energy of photon=energy of positeron + energy of electron + kinetic energy of electron + kinetic energy of positeron



Law of conservation of momentum.


Momentum of photon = momentum of electron + momentum of positeron


Hf / c = mv1 + mv2

Where v1 = velocity of elecyron

Where v2 = velocity of positeron

Hf = mc ( v1 + v2 )


But we know hf = 2mc^2 from the first equation

E = hf E = mc ^ 2

But v1 is not equal to c .

And v2 can never be equal to c.

Remember that elementary particles only move at a velocity which is never equal to speed of light.

Therefore an obstacle would have to absorb a large part of the momentum so that the laws of conservation of energy and momentum can be satisfied simultaneously.



Such an obstacle is the atomic nucleus.


But anyway the energy of the photons has to exceed the total resting mass energies of both electrons and positrons

Isn't matter a form of energy with less entropy?

If this is so, won't converting energy into matter violate the laws of thermodynamics? notably reducing the entropy of the universe?

I have to confess, I've never actually considered the possibility of converting energy to matter, never could find a use for it.

Teempakguy:
Isn't matter a form of energy with less entropy?

If this is so, won't converting energy into matter violate the laws of thermodynamics? notably reducing the entropy of the universe?

I have to confess, I've never actually considered the possibility of converting energy to matter, never could find a use for it.

Energy cant be said to have entropy because entropy itself is a mathematical function of the energy of a system.