Dense regions generated gravity, attracted more matter and became denser. So it wasn't long (a few million years) before huge seething hot spheres of hydrogen were speeding through our baby universe.
But it didn't stop there. Just like the hydrogen atoms, stars create gravity. Soon the stars themselves would clump together into huge groups, millions of light years across. These we would call galaxies, our most familiar one being the Milky Way.
Dust, rocks, and planets
A star contains massive amounts of super heated hydrogen at its core, which will keep it burning for many millions of years. But eventually the first wave of stars in our universe would run out of fuel, and with no more fusion to resist their own gravity they would collapse.
 |
Temporary expansion as a dying
star explodes
(image from nasa) |
Now the collapse of a star compresses huge amounts of energy into a tiny space in one final destructive death cry of super fusion. But from this destruction comes creation. At the incredible temperatures within the dying star, larger atoms can collide, combining to create still larger ones.
Our biggest elements (such as gold) are formed when the largest stars collapse, creating incredible detonations called super novas that outshine every star in the galaxy for a short period of time, often shrinking to tiny points of matter called black holes, heavy enough to suck in light itself.
 |
Artists impression of an early
solar system, with a star surrounded by dust
(image from berkley lab) |
As the first stars died they would spit out huge amounts of these heavier elements creating vast clouds of dust. As more stars formed the dust gathered and once again gravity came into play. The dust formed clumps to create rocks. Rocks become asteroids, and asteroids become planets.
This process would repeat many times, and eventually, 4.6 billion years ago our very own solar system was born. Orbiting a star called Sol it originally contained only huge gas giants - planets formed not of dust but of gases such as hydrogen, surrounded by mini planets called moons. However, after another few million years enough dust would gather to form rocky planets, and around 4.54 billion BC, earth was created from the stellar remains surrounding Sol.
Baby Earth
Back in its day, the earth was a very different place. Its surface consisted largely of molten rock, and at these extreme temperatures, the heaviest of the common elements, iron, sunk to the center, giving our planet a spinning core of liquid metal.
 |
Artists rendition of early earth
with a liquid surface
(image from ulsfmovie.org) |
As the crust cooled and hardened, huge super volcanoes would erupt, spewing more molten rock and gasses such as carbon dioxide and methane. The gas built up, clinging to the earth under gravity, and a magnetic field created by the spinning iron core prevented solar winds from ripping it away.
The next few million years on early earth are uncertain times, it being such a volatile and ancient place. One of the greater mysteries of these early years is why it has so much more water than other planets. There are many theories, but the most widely regarded is that the asteroids and comets of the primeval solar system, constantly colliding with the earth, delivered vast quantities of water in the form of ice.
Whether we'll ever know the exact details of earth's very early history is debatable, but what we do know (by finding biological residue in ancient graphite!) is that somewhere between 4.1 and 3.9 billion years ago, with an atmosphere, heat, assorted chemicals and oceans, the stage was set for the next chapter in this amazing story - life!
Some primeval chemistry
By now the earth is a planet in a stable orbit around the sun, with a solid crust, an atmosphere (albeit mostly poisonous gases!), oceans, an assortment of chemicals, weather, and even a moon it picked up along the way from some planetary sized collision.
 |
The basic structure of an amino acid
(Image from wikipedia) |
Floating in the huge oceans of primeval earth are small molecules, undergoing constant reactions as they come into contact with each other. In the intense atmosphere some of these small molecules would combine to form amino acids, complex chains of carbon, nitrogen, oxygen and hydrogen, with side chains made up of other elements.
Certain types of amino acids, such as glutamine have a very special part to play in early life. These molecules are the precursors to more complex molecules called nucleotides, which can join together to form huge chains that we now call DNA and RNA - the building blocks of life.
Now this may all sound rather unlikely. Somehow a set of tiny molecules joined, and joined again, and combined and connected to form DNA - and all by chance! But the truth is billions upon billions of chemical reactions happen every day, and back in primeval earth they had billions of days in which to occur. When you look at it like that, if the ingredients were there, how could it
not eventually happen?
Molecule machines!
So after a few millions of years basic DNA was finally floating in earth's oceans, and it had a some very special properties.
 |
Dna splitting and forming 2 new
identical copies of itself
(image from biotechnology) |
Firstly, being formed of a double helix (2 intertwined spiral strands), it has the ability to split into 2 separate single strands. These single strands can then attract the necessary simple elements to reform new double helixes. Put simply, DNA can self replicate. On top of the ability to replicate, the reforming process isn't perfect - sometimes errors can occur, causing it to mutate.
Of course, a molecule that can self replicate is pretty amazing, but in itself not that much use. However, by interacting with other simpler chemicals, DNA can form a class of molecules called proteins. The exact structure of the DNA and the chemical environment it is in control what will be produced, allowing it to create a vast array of proteins.
After millions of years the earth had built a self replicating, molecule building machine! Its exact makeup was like a computer program controlling what proteins should be created and when. With its double helix structure this complex molecule could create copies of itself, with a small chance of mutations, causing new versions of the code. These mind blowing properties encoded with nothing more than a complex chain of atoms produced a machine that could sit at the heart of a cell, read the chemical environment, generate new molecules in response and reproduce to build new cells. This amazing feat, around 4 billion years ago was nothing less than the chance development of life on earth.
Basic Life
The oceans of earth now contain the building blocks of life - microscopic machines capable of reproducing and building proteins according to a code. However, this in itself was not enough. Initially the codes were random collections of instructions with no useful purpose. Fortunately, with the ability to reproduce and mutate, these tiny machines were ready for the next great stage in the development of life - evolution by natural selection.
 |
A modern bacterial form of prokaryote
(image from wikipedia) |
To replicate and produce proteins, DNA needs resources in the form of energy and other molecules, which were initially in abundance in the great oceans of earth. However, for the first time there was competition. Some codes produced proteins that attracted further molecules. Others developed membranes by creating proteins that formed a protective bubble around the DNA itself. By being very slightly more effective than other codes, certain DNA was able to last longer, and thus reproduce more often. This process of gradual improvement is called evolution, and the driving force - survival of the fittest - is called natural selection.
By 3.6 billion years ago certain codes had begun to dominate, mutate, and occasionally improve. The codes were naturally refined to the extent that the first life forms emerged. Known as prokaryotes, these simple structures consist of a strand of DNA surrounded by a liquid (cytoplasm), an inner membrane, a cell wall, an outer membrane and finally a 'shell'. The membranes allowed useful molecules in, but blocked others.
Team Work
Over the next few 2.6 billion years life would slowly but surely be refined. Not through targeted improvement, but by the simple preservation of superior mutations. Prokaryotes became cyanobacteria, the first lifeforms to perform photosynthesis and convert the toxic atmosphere into an oxygenated one. Next up were the complex cells - eukaryotes, with a well enclosed nucleus to contain the DNA, and additional structures to allow for more complex means of survival. During this process, some cells were able to mutate (and thus evolve) more efficiently by merging DNA with other similar cells, and sexual reproduction was born.
 |
A simple multicellular lifeform
(image from news soft) |
Many of these early life forms still exist in one form or another. Being a single cell is still a perfectly good way of surviving, as bacteria is well aware! However, in the competition for resources some bacteria began to benefit from safety in numbers by growing in clumps.
Around 1 billion years ago this social bacteria became what we now call multicellular life. Single life forms made up of multiple cells with identical DNA. With this new ability, life was able to adapt further, and earth's oceans finally contained complex organisms.
Plants, creatures and fungi
In those early years life branched out and flourished in many different forms. Some took advantage of the techniques of cyanobacteria, converting carbon dioxide to oxygen through photosynthesis. These would become the early plants and fungi that grew comfortably in the sea without a need for structural support.
Other life forms evolved from the eukaryotes, taking advantage of more complex cells that took on different tasks to create life forms that were far greater than the sum of their parts. Today we call these animals, and they began with very simple creatures such as sea slugs and jelly fish.
Gradually segmented life forms would develop, made up of multiple almost modular segments with an array of different purposes, such as senses, propellance and tactile interaction with their environment. By the time we reach 500 million years ago life has evolved into many different distinct species. Bacteria, amoeba, slugs, sea-insects, fish and plants are all floating or even swimming in the sea. A food chain has developed, with life forms consuming other life forms rather than collecting nutrients directly from the sea.
Being well suited to growth on land, plants and insects eventually exploited this huge and as yet unused resource. The simple structures and strong walls of plants required nothing more than reinforcement and some refining of reproduction to thrive on land. Similarly, sea insects with their hard supporting shells didn't struggle too much with crawling onto the early beaches to lay eggs and find food.
 |
The gas filled swim bladder of a bony fish
(image from fresh aquarium) |
The last to make the transition to the now green shores were the fish. Some took advantage of the lack of predators on land and so laid eggs on the beaches of earth. Gradually they developed features that allowed temporary survival outside of the water, the greatest of which was the ability to absorb the oxygen stored in their swim bladders (a small internal pouch to help them float) directly to the blood stream. Soon muscles would develop to refill the bladder with air whilst out of water, and the first lung was formed. Thus, 350 million years ago, the amphibians crawled out of the waters. Some would later choose never to return, becoming land dwelling animals.
Early Life On Land
Over the next few million years life would flourish into a bewildering variety of species. The early amphibians with their scaly fish like skin transformed into the lizards. Cold blooded creatures that slept during the night, then used the heat of the day sun to warm their blood and survive far away from the seas from which they came. In the then temperate earth, with it's highly oxygenated atmosphere these lizards would grow huge.
 |
An early dinosaur - the plateosaurus
(from wikipedia) |
The first recorded dinosaurs, prosauropods, with their distintive skeletons, would appear around 225 million years ago and over the next 150 million years these giant lizards would dominate the earth. However, the planet was cooling and the level of oxygen in the atmosphere gradually stabilizing at a lower level than that in which the giant creatures had evolved.
68 million years ago a vast extinction event occurred, most likely a huge meteor. While the detonation itself would not have eliminated life on earth, its effect on the planet's environment would have been epic, long term and disastrous for the giant lizards that depended so greatly on warm sun and a rich atmosphere.
Evolution is not one to be stopped by a simple extinction event however! Towards the end of the reign of the giant lizards, a tiny new branch of creatures was beginning to evolve. Probably starting out as miniature lizards, these creatures had evolved their own internal chemical heating system, fur to keep that heat in, and improved night vision. These warm blooded creatures that we now call mammals could forage, and eventually hunt, at night, when the major predators were dormant.
As the effects of the meteor were felt, the giant lizards and sea creatures would die out in an environment that was simply no longer rich enough to support them. In their place the early mammals, smaller lizards and the few surviving dinosaur descendants, the birds, would take over. This would be the dawn of life's next great age, and the beginning of an earth that would be much more familiar to modern man.
The dawn of man
We've now moved on from the big bang at the beginning of the universe to an earth rich in life a mere 65 million years ago. The giant lizards have been all but wiped out, along with thousands of other species through a mass extinction event, but life is already filling in the gap. In the place of the giants come smaller lizards, birds, and crucially for us, mammals.
A new race of flying animals (a close ancestor of the flying lizards) would soon become hugely successful, branching into both scavengers and birds of prey. Owls, wood peckers, parrots, song birds and ancestors of flightless birds such as the ostrich would come to be, and soon the sky would be as full of life as the land itself.
Throughout the same period, the mammals would begin to take hold. Rhinoceroses, camels and even the earliest primates were evolving, but the great push towards modern mammals was yet to come.
35 million years ago was a little known but absolutely essential event occurred in the evolution of modern life. It was at this time that a new form of plant life evolved, spreading through both root networks and pollen, capable of surviving on relatively small amounts of sunlight, and could prospering in areas that other trees and plants had failed. We know it today as grass, and as it began to spread, so too did the creatures that fed on it. Modern creatures such as deer and zebra sprung up, along with their natural predators. Hawks and eagles evolved to catch the tiny mammals living in the grass, and crucially for us some of those primates would come down from the trees to exploit the new food rich environment of the grass lands.
Throughout the next 33 million years thousands of the species we know today appeared, including most of the apes such as chimpanzees, gorillas and the orangutan. But finally, a mere 2 million years ago, the first species of the genus 'homo' would appear on the plains of Africa.
Modern humans
It's crazy to think that over all these billions of years it wasn't until 2 million years ago that a race appeared which even remotely resembled a human being. If the history of the universe was compressed into a year, this wouldn't have happened until very late on December 31st! But much was to come before these ape like creatures would evolve into the intelligent and social creatures we know as modern humans.
There's great debate over how many species of the genus homo actually existed. We know Homo-Antecessor, a very early ancestor appeared around 1.2 million years ago, and following it, 600 thousand years later was Homo-Heidelbergensis. This would later branch out into 2 separate paths - the neanderthals (who's reputation as stupid and aggressive is likely to be highly inaccurate), and later in 200 thousand BC, homo-sapiens, or 'modern humans', appeared on the plains of Africa.
Around 50 thousand BC, the homo-sapien would expand from Africa, out into Europe and Asia. As we filled other continents and adapted to the changing environments, humans proved to be best suited to survival and gradually replaced the intelligent neanderthals and other hominid species.
Our early human ancestors, while intelligent, were primarily scavengers, and as a result lived in small groups sharing the job of gathering resources. However, over time, probably through a chance realization that seeds could be planted and would grow into new plants, the process of domestication began. Through farming human beings could afford to live in larger groups and build permanent settlements rather than having to follow the food. It was now possible to produce an excess of resources, allowing specialists in other areas to prosper.
 |
Early Egyption domestication
(image from wikipedia) |
Exactly when domestication of animals and farming of crops really took off is not entirely certain, with estimates ranging from as early as 50 thousand BC, all the way down to later than 10 thousand BC. Astonishingly though, by the time we hit 0 AD, huge and technologically advanced civilizations had arisen, with vast cities full of thousands of people. Human beings had taken the step from primitive apes investigating those early grass lands to intelligent, social creatures that were set to expand and eventually dominate planet earth all the way up to the present day.
And the rest, as they say, is history!
The history of the universe and me
As I said at the beginning of my blog, I wrote this to show why I am entirely happy to live with the knowledge that we are simply one of many astonishing outcomes of that single event 13.8 billion years ago. Hopefully it's obvious having read the story. It is absolutely stunning. Mesmerizing, astonishing and truly humbling to think of the series of events that led to the present day.
On the more philosophical front, this story really does, at least for me, go some way to defining an answer to the ultimate question - what is the meaning of it all? Well, we are simply atoms, but we are also from many perspectives the most complex entities in the known universe. Yes, we are simply computers, but we are so advanced that we can reason, predict, make decisions and judge their outcome. As a result we can feel and emote, even perform selfless acts of compassion that go against every rule of evolution that led us to the present day. Sure it's technically just neurons firing, but what does that matter? The result is the same!
And so you can only really come to one conclusion. The meaning of it all, or at least the goal from my point of view is simply to lead a worth while life. I try and use my ability to predict to treat the planet well in the interests of future humans. I try to use my compassion and empathy to treat other people how I would like to be treated. And on top of that, I simply try to progress and improve myself every day, so when it comes to the end I can look back and know that I didn't waste my 100 years that resulted from the 13.8 billion years before them!
The End.
