You're going to need some physics background to understand this, namely quantum mechanics, particle fields, quantum fluctuation, cosmic microwave background radiation, etc. Allow me to do my best to explain it in layman's terms. Basically, empty space is not empty; it is full of quantum particles that pop in and out of existence, like a boiling brew. Quantum mechanics is built upon the property that when something is not being watched, it can change quantum states ad infinitum. Thus, empty space continues to "move" between all possible states, from nonexistence to hyperactivity. This is called quantum fluctuation. Energy exists everywhere, even in a vacuum. Space is full of energy: inside you, inside me, inside the earth, inside the sun, and inside emptiness. Emptiness IS NOT empty. Weird concept, but very cool. The conservation of energy law states that quantum systems can only fluctuate between states for so long.
For example, consider a charged object, like a balloon after you rub it on your hair. It sticks to the wall, right? It makes your hair stand up. Quantum electromagnetism states that the static field is created by the emission of charged particles that you created when you rubbed it on your hair. These particles have no quantum energy though, so they can propagate without disappearing entirely, thus creating that static force that holds it to the wall.
Now let's apply this to outer space. Think about black holes. There is a radius around the black hole called the event horizon. Inside this event horizon, nothing can escape it in terms of classical physics; not even light. It works both ways: light emitted from INSIDE the radius CANNOT be seen from the outside. It's like a wall of nothing. Once you go past that wall (from either direction), you stop existing.
Now back to my "bubbling brew" statement. Imagine two particles (a particle and its antiparticle) pop into existence in some quantum fluctuation field near the event horizon of a black hole. What if one of those particles gets sucked in? Well, it cannot EVER reunite with the other particle in order to destroy both of them, thus the free particle can fly off. Boom. Something came from nothing, a mere quantum fluctuation.
It's a scientific fact that the universe contains more matter than antimatter. Why? Quantum fluctuations and particles that fail to annihilate each other.
So how was the universe created? Quantum fluctuations. Nothing existed. There was nothing at all before "Time Zero" -- but remember, nothing IS something. So, empty nothingness is a boiling brew of these particles popping in and out of existence. But there's a problem -- if there's nothing to disturb these particles, then they can just go on annihilating each other for all of eternity and nothing will ever happen -- no mass, no stars, no atoms, etc.
Here's the fun part -- these particles are all annihilating each other at extremely fast speeds, and they're all fluctuating between quantum states rapidly since "nothing" exists before "Time Zero". It's basically a free-for-all. Lots of radiation begins to release and accumulate. Particles begin to pop in and out of existence faster and faster. Then, all it takes is ONE pair of particles to establish a small amount of asymmetry, and BOOM. All of that energy: the radiation, the fluctuating quantum states, the rapid expansion of particles' radii, it all comes together and releases an ENORMOUS amount of energy, blasting outwards in all directions with such force that's absolutely beyond mortal comprehension. That single set of particles that established that tiny bit of asymmetry threw off the particle-antiparticle ratio, and thus there is a small amount of particles left over that begin to influence the quantum system, creating more and more and more asymmetry until you have enough particles to create matter, and elements, and atoms, and compounds, and gasses, and stars.
Sounds far-fetched. Well, there's proof: the cosmic microwave background radiation. The CMBR's photons are the remnants of this matter-antimatter annihilation near the beginning of time.
And that's how you create a universe from scratch
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