Matter can spontaneously appear in a vacuum by "borrowing" energy from the universe. It comes in the form of a particle and anti-particle. These two
particles are completely opposite to each other in everything but mass. They have opposite charge, baryon/lepton number etc.
Since they are particle and anti-particle, when they collide they annihilate and release energy equivalent to the "borrowed" energy used to create
them. Usually they exist for only fractions of a second before they annihilate, but sometimes they can pull away from each other and exist for longer
For a more complex explanation, see this quote. The source site also has a multitude of other quotes explaining around the subject, which are all
themselves sourced back to a respected physicist's work.
There are something like ten million million million million million million million million million million million million million million (1
with eighty [five] zeroes after it) particles in the region of the universe that we can observe. Where did they all come from? The answer is that, in
quantum theory, particles can be created out of energy in the form of particle/antiparticle pairs. But that just raises the question of where the
energy came from. The answer is that the total energy of the universe is exactly zero. The matter in the universe is made out of positive energy.
However, the matter is all attracting itself by gravity. Two pieces of matter that are close to each other have less energy than the same two pieces a
long way apart, because you have to expend energy to separate them against the gravitational force that is pulling them together. Thus, in a sense,
the gravitational field has negative energy. In the case of a universe that is approximately uniform in space, one can show that this negative
gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero. (Hawking, 1988, 129)
[thanks to Ross King for this quote]
Just so you have a brief understanding of what "the universe = 0" means in context:
One of the most fundamental or basic particle known in the universe is the quark. There are 6 types of quark, up
s and charm
c, each with a different fractional value in certain categories. The most important (and easiest
to understand) categories are electric charge and baryon number. There are many more, but let's just leave it at that for now.
The values are:
Quark Charge Baryon No.
u +2/3 +1/3
d -1/3 +1/3
t +2/3 +1/3
b -1/3 +1/3
c +2/3 +1/3
s -1/3 +1/3
These quarks all have a corresponding anti-quark, signified by the symbol used to represent the quark, but with a bar on top e.g
These anti-quarks also have the same quantity in terms of charge and baryon number, but with the +/- symbol reversed.
Protons and neutrons are made up of quarks, namely the u and d quarks. Protons and neutrons are both made up of 3 quarks, and have a baryon number of
Proton: uud = charge of 2/3 + 2/3 - 1/3 = 1
Neutron: udd = charge of 2/3 - 1/3 - 1/3 = 0
Antiproton: - - - = charge of 1/3 - 2/3 - 2/3 = -1
u u d
When a particle and anti-particle collide they release energy via annihilation. The protons cease to exist and instead form a variety of mesons, which
are made of a quark and anti-quark pair, these mesons then decay further and release gamma radiation (y).
That's why no conservation laws are broken by matter existing - it all eventually becomes energy one way or another. Proton annihilation is actually
a complex process, thinking back I should have used electrons instead, but it illustrates the point well enough I think.
I don't have enough space left to describe the process of pair production where a photon decays in to an electron and positron, but you can look it
up on the internet easily enough.
Anyway, to clarify:
- latent energy in universe becomes matter (pair production)
- sometimes matter exists for very short time
- sometimes matter exists for very long time
- matter that exists for a long time forms material universe we can see and inhabit
- eventually matter becomes energy (annihilation)
- read the quoted website to see some people cleverer than me explain it in a way better than I ever could