Lifetimes of research have been dedicated to discovering how the universe was formed, and what it looked like and how it behaved during its stages of development. The topic is a little lengthy, so it will be divided into several independent posts. But first (as usual) we need to address a critical concept: time.
Astronomers estimate that the age of the universe is something like 14 billion years. Imagine what it will look like in twice that time, another 14 billion years from today. Do you expect it to look the same? Clearly not. Most of the stars currently in the universe will have extinguished and exploded and new ones (made up of the less pure remnants of the recently departed stars) will have taken their place. With these new stars (known as population III stars), it is entirely possible that everything we currently know about the behavior and interactions between stars will have changed. Their compositions, lifetimes, and nuclear reactions will be different. With that established, it doesn't seem like a stretch to say that doubling the age of the universe changes it significantly.
Keep that in mind as we explore the first few epochs of the existence of the universe. They take place fractions of seconds after each other in what would today be termed rapid succession. Remember, however, that when the universe was 10-30 seconds old (a trillionth of a trillionth of a millionth of a second or so), it was millions of times older than it was when it was 10-40 seconds old. Back then, time wasn't very old. The age of the universe doubled in units of time too small to think about. So, at that time, fractions of a second were as significant as billions and billions of years would be today. Let's take a look at the earliest stages of the life of our home.
The universe started as an immensely massive, yet infinitely tiny point. At some point in time, something caused it to expand at an astounding rate.
The Planck Epoch
0 to 10-43 seconds
Light and heat are the only two things able to exist. Due to an extremely high temperature (~1032 °C), nothing solid can form and remain formed. Much in the same way that ice can't remain ice at high temperatures, any energy trying to form itself into matter disassociated (broke apart) immediately due to high energy light and became energy again. During this time, it seems that all of the forces that we are familiar with (gravitational, electromagnetic, and nuclear forces) were combined into one unified force that governed all things.
The Grand Unification Epoch
10-43 to 10-36 seconds
As the universe expands, it cools (the same amount of energy is distributed over a larger space), causing gravity to establish itself as a unique, fundamental force. The smallest and most fundamental particles (Higgs Bosons) also form.
The Electroweak Epoch
10-36 to 10-12 seconds
At a whopping 1028 °C, the universe separates the nuclear strong force into a unique and fundamental force (the word fundamental here is not a contradiction even though the force came from something else. I only mean that in these conditions, the force becomes fundamental). During this epoch, we suspect that a rapid expansion period took place known as the cosmic inflationary period. The volume of the universe expanded enormously for several thousand trillionths of trillionths of seconds (during which the total age of the universe doubled about 5000 times). The temperature dropped significantly and quarks (the building blocks of protons and neutrons) formed out of the now cooler energy.
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We're still a trillionth of a second away from the first whole second of the universe's life, but we have already traversed three major epochs in the formation of the universe in which we live. Stay tuned for the next major age of synthesis.
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