Editors note: This is the first requested post made to walled city. This one is by Nick, who wanted insight into the origins of the universe.
In high school, I attended a course called Earth Science. It was, by and large, a 'filler' class - a class meant to be taken when all other options, such as Chemistry, had been either taken or otherwise were unavailable. At one point during this course, the teacher attempted to explain the currently accepted scientific explanation of the origin of the universe (with the caveat that she did not expect everyone to believe it, so as not to offend the young-earth creationists in the class).
She failed miserably.
The Big Bang theory and model of the universe is an extremely misunderstood concept, and is not required teaching in most schools, likely for the same reason that evolution is not required teaching. Therefore, even when a teacher attempts to discuss it with the class, she does not have the required background or knowledge to do so. I lauded the teacher for even trying, condemned her for the subsequent Creationist warning, but mostly, I was disgusted by the way she explained it. She presented it in such a way that it sounded like pure fantasy, and among those students who did not already know the actual theory, there was much disbelief. I cannot say I entirely blame them - had the only information available to me come from this teacher, I myself might be just as incredulous. (Although, I can blame them for not knowing this material already. This is important stuff, people!)
I'd like to present a brief lecture on the origin of the universe. I am not a physicist by any means, and although I will try to offer the most factual information possible, I cannot guarantee that everything is 100% absolutely the most up-to-date accepted model. I can, however, promise that my information will be vastly superior to any you are likely to find in a high school textbook (which is full of "somehow"), or from a high school teacher.
In the beginning, God created the heaven and the earth.
Setting aside for the moment the issue of "where did it come from" (we'll get back to it) let us accept that, roughly 15 to 20 billion years ago, the cosmos were born in a release of energy known as the Big Bang. We will discuss what is known as the "hot big bang model", which assumes that the universe is described by a Friedman model all the way back to the Big Bang. This assumption agrees very well with what is observed.
This release was pure energy; there was no matter involved. As you can expect, as the universe expands, the average temperature of the matter and energy in it decreases. Since temperature is merely a measure of the average energy in a system, this "cooling off" of the universe will have a major effect.
Recall, if you will, Einstein's equation that states E=mc^2. This equation shows that energy and matter are interchangable: Energy equals mass times the speed of light squared. Given enough energy, basic subatomic particles will begin to form - protons and electrons. At very high temperatures, such as we'd find a few seconds after the Big Bang, particles would be moving around so fast that they would resist any attraction to each other caused by the nuclear or electromagnetic forces.
About one second after the Big Bang, the universe would have had a temperature of roughly ten thousand million degrees (Stephen Hawking, Cambridge Lectures on Cosmology, 5 of 8). To give you an idea of the temperature involved here, this is hotter than the surface of the hottest stars, but temperatures on par with this are reached in hydrogen bomb explosions. At this early point in the universe, we mostly find photons, electrons, neutrinos, and all their antiparticles, and a few protons and neutrons.
The universe continues to expand, and the temperature to drop. After the temperature has decreased sufficiently, particles would no longer be able to resist the attraction towards each other, and would start to clump together. Protons attract electrons, and here we have the first hydrogen atoms.
Let there be light.
Over time, as the universe continues to expand, and gravitational irregularities develop, hydrogen atoms start clumping together due to gravity (remember that all matter induces gravity according to its mass). The more of them come together, the more gravitational influence they exert, and attract even more hydrogen atoms, which increases the gravity, which attracts more atoms, and so on. When enough atoms have come together, and the gravitational force within the collective mass is high enough, they begin to fuse together, resulting in a fusion explosion, and the birth of a star.
At the heart of any star is a fusion furnace - hydrogen atoms being compressed together to such a great degree that they fuse together, releasing the nuclear strong force that bound their nuclei together - this results in an immense release of energy. This process also produces helium atoms.
When a star has run out of hydrogen fuel, it continues fusion with the next available element - helium. When helium fuses, it produces a slightly heavier element, and when the star runs out of helium it continues. I believe this process can continue all the way up to the element of lead, but I may be mistaken. Regardless, it is within a star that elements heavier than hydrogen are created, and when at last the available fuel becomes too heavy to continue fusion, the star collapses under it's own gravity (the fusion explosions were what kept it from doing this before). In this collapse, the star goes nova, creating a nebula and spreading these new, heavier elements back out into space. The nebula itself will eventually collapse due to gravity and form another star - and leftover matter from the nebula will have to orbit the star. The orbiting matter will itself begin to clump together due to gravity, and here we have planets.
It is not my intention to go further in the history than I have at the moment. I find it amusing, on some level, that our human ego drives us to change the focus when discussing this sort of thing; we start off with the formation of the universe itself, and gradually narrow it down to Earth, and narrow it down from there to life, and from there, to humanity - and then we stop. The lecture always concludes with, "..and finally, man appeared," as though we were the be-all and end-all; that our arrival was what everything was leading up to and the universe could safely stop everything else it had been doing.
Hubristic though we may be, the fact is that stellar processes did not grind to a halt when we showed up. Stars continue to be born, others continue to die, entropy continues to grind away. Our arrival did not cause any stir among the cosmos.
For that reason, we aren't going to get into evolution today.
In the commissioning of this article, the question of the original "source" was brought up: We have the Big Bang, and everything we observe today leads back to it, but what caused the Big Bang itself? Where did the original energy come from?
Naturally, many religions turn to God at this point, using the First Cause argument or a variation thereof. I hardly need to belabor my view on this - I did so here, specifically sections IV and V. There are multiple problems associated with using any type of god as an explanation for this.
A theist uses God as the metaphysical primary for which all discourse depends. He backtracks far enough into the history of the universe, comes to the inevitable question "So where'd it come from?" and concludes: God. As an atheist, I accept the universe itself as the metaphysical primary; again, for reasons disclosed here.
Stephen Hawking has some fascinating insights into possible origins of the universe, including one theory that universes are spawned from the black holes of other, higher-dimensional universes. In this context, this would mean that our universe was formed as the bottom of a singularity "wrapped" around itself in spacetime in a fourth-dimensional universe, which itself may be spawned from a fifth-dimensional plane, and so on. His explanations can be found in the above book, as well as in this one.
We may also wish to consider the possibility of an eternal cycle of collapse-and-rexpansion. Such a model is known as a "closed universe", in which the total gravity of the system exceeds the force at which the universe is expanding - thus, the universe will eventually stop expanding, recollapse on itself, and start again.
Is it really so curious that our universe should be "just so"? - that everything seems to be exactly what it needs to be? There are only a few dozen fundamental constants that describe the nature of our universe - the mass of the proton, the strength of gravity, the power of the nuclear strong and weak forces, and so forth. A universe that began randomly would have virtually (emphasis on virtual) no chance of being 'viable'. Get the fundamental constants wrong, and you end up with a sea of boring gas, or a hot knot of plasma, or some other equally uninteresting, 'unviable' universe that cannot form basic matter, nevermind stars and planets and life.
In fact, the odds can be calculated. Neal Stephenson, in his excellent The Command Line essay, writes, "If there were some machine, somewhere, that could spit out universes with randomly chosen values for their fundamental constants, then for every universe like ours it would produce 10^229 duds."
It would seem that the odds are insurmountably against us ever having appeared, if the universe were spawned with randomness that way. At least, it seems that way, until we consider the fact that we are here and asking the question. There are, of course, other theories besides the two I mentioned above, but it really isn't worth noticing that our universe happens to be one we can live in. To me, this is like a puddle waking up one day and saying, "This certainly is an interesting hole I live in. Why, I'm a one-gallon puddle, and this is a one-gallon hole! And look - it fits me just perfectly! Why, it's as though this hole was made just to have me in it! How fortunate that the hole was shaped just right for me - perhaps someone planned it that way."
The nature of the universe dictates what will go on within it, not vice versa. Now, it's tempting to bring up certain laws of physics that seem to offer counterpoints to the entire situation. For example, the first law of thermodynamics states that energy and matter must be conserved - they can neither be created nor destroyed. Or the second law, which states that in a closed system, entropy must increase. It would seem, then, that the formation of the universe is a violation of these laws.
However, such laws of physics only apply within the context of the universe itself. "Before" the universe was born, or during the moment of it's birth when it was a mere singularity of zero size, such laws have no meaning. It makes no sense to take laws of our universe, wrench them from their framework, and try to apply them before the universe was even there.
Suppose that universes are being spontaneously generated out of higher-dimensional universes - as we saw before, most of them would be complete duds, but every once in a while, one comes along that allows matter and stars to be formed. Or, consider a cyclic universe that is constantly expanding and collapsing - most of the universes that come out of such a process would be dead and lifeless, but again, given enough cycles and enough chances, eventually one appears that allows interesting things to happen.