It is believed (at least I think so) that the first living entity was something extremely simple. Are there any theories about how simple?
- Simpler than short strand of DNA?
- An RNA molecule?
- One very simple group of molecules which evolved into DNA based single celled creatures?
It is my understanding that all known life on Earth is based on DNA molecules using the same genetic code. True? If so:
- Is this due to one single celled creature which is the ancestor of all current life?
- Is it due to several single celled creatures which developed independenlty of each other with the same genetic code? This seems unlikely.
- Is it due to several independent initial single celled life forms, all but one of which (our ancestors) became extinct?
- Might there have been several types of creatures more complex than singled celled creatures with different genetic codes (or not based on DNA), all of which (except our ancesters) became extinct?
This was written a few years back, but reading over it, i can't see any mistakes... for now anyway... lololol.. hope it helps.
''Part One
In the beginning
It is always best to start right at the beginning, and this beginning happened 15 billion years ago when there were no stars or planets in the heavens. No time to measure or any space to move through. There was simply nothing. Then, out of the nothingness appeared a sudden act of violence - a spontaneous expansion of energy and gas. Here, space and time began.
Ancient Roman philosopher Lucretius pointed out over 2000 years ago, that there was a paradox concerning the boundary, or edge of the universe. He states, that for there to be an edge, it would mean that the universe had something beyond it to show it was the edge. However, Albert Einstein, one of the greatest physicists that had ever lived, showed that everything that 'counts' must be contained within the expansion of space and time - thus - the edge of the universe is the boundary between nothing and everything.
This dawning of energy and gas has come to be known as the 'Big Bang.' The Big Bang came out of a 'singularity' which is a point in space and time with infinite qualities - anything that moves into a singularity grows to unimaginable size. A singularity has infinite curvature, and a zero-radius. Here, all laws go bizzerk. The expansion of energy and gas created the first stars - and after billions of years, these stars exploded and sent into the deep regions of space stardust debris that joined and formed the first lot of planets, through a timely process called 'accretion'.\
All matter is made up of tiny little units called 'atoms'. To grasp how small they are, take a Hydrogen atom, the simplest atom in physics. The size of a hydrogen atom is quite small... Describing how small is not an easy task. However, there are even smaller bits of matter that inhabit atoms. Simply, they are called, 'subatomic particles' and are quite small even compared with an atom. We have a wide range of particles in physics labs today, with something like 410 or so known; we will investigate four of those particles in this chapter.
There are 10^80 particles in our universe that accounts for our current observations of the cosmos. That number is vast, compared with the size of planet Earth. Our planet is the third 'rock' from the sun. It is one of ten known (we once thought there was only nine planets in our solar system, but recent data the last year, 2006, showed other planets orbiting our sun - and there is thought to be an eleventh. Here it might be best to note that Pluto is not a planet. It is actually a moon). Our planet contains about 10^24 x 6 kilograms of matter. The sun is gigantic compared to this sum - the sun is a gigantic ball of gas; an E=Mc^2-pumping station (more on E=Mc^2 later). It is something like 6 million times larger than Earth, containing 333,000 times more mass - however, on a cosmic scale, this is a small star. 'Red Giants', which are nothing but a star at the end of its lifespan, are several times larger!
Up to our present time, physicists have built quite a reasonable picture of our universe. However, it has been far from being anything but a smooth ride, and still some questions hound the text book pages of quantum mechanics and cosmology. We have had to alter theory after theory, since problem after problem arose.
Theory suggests our universe began with an infinitesimally small size - something like the size of a human skin cell. However, it was here the first problem came about. As small as this was, the universe would have still been far too big! This would ultimately result in light (the first subatomic particles of energy) not having enough time to reach the four corners of the universe.
The universe grew quite old before light first emerged. The very beginning of our universe has been come to be commonly known as the 'first chronon' - even though it sounds like a Star Trek villain it is in fact a time period. It is also called the 'Planck time' - which is 5.3 x 10^-44 seconds.
A chronon is the billionth part of the billionth part of the billionth part of the billionth part of the billionth part of one second. Accordingly, a billion chronons passed, before there was any light in our universe. Thus, if our universe had started with the size of a cell, it would mean there was not enough time to start the universe to assure that all background temperatures in space would show different frequencies - but they don't. It all has the same temperatures.
To eliminate this paradox, physicists brought together a dubious 'inflationary phase' - the need for inflation was to start the universe on a much smaller scale - like the size of a subatomic particle so that light could reach those corners of space and expanded faster than light. Light travels at 299,792,458m/s or 186,000 miles per sec. The model, mediated with rapid expansion seemed to wipe away the problematic situation - it also added another 5 billion years onto the age of the universe.
However a new problem persisted. Apparently, our universe should show initial start-up conditions that where never wiped out - we would still see evidence of such conditions today. No one has yet solved this problem with clarity - some have brought into the picture 'parallel universes' to wipe out these conditions (more on parallel universe theory later).
Though, it still stands that Big Bang is still a theory - nothing is set in stone - and not everyone believes that everything originated with a tremendous spill of energy and matter via a Big Bang. Some believe that everything came around by other means. Even Einstein once said, concerning the 'Hubble Shift' - (the Hubble Gravitational Red Shift showed that all planets and stars where rushing away from planet Earth, proving that everything was in fact moving away from each other);
'There does arise, however, a strange difficulty. The interpretation of the galactic line-shift discovered by Hubble as an expansion leads to an origin of this expansion which lies only a billion years ago, while physical astronomy makes it appear likely that the development of individual stars and systems of stars takes considerably longer. It is no way known how the incongruity is to be overcome.'
Yes, Einstein did indeed have problems excepting the Hubble Red Shift. Einstein, before the discovery of the Hubble Red Shift did not believe the universe was expanding. He said, 'it was my biggest blunder,' and passed in physics history as nothing but a curiosity. However - his protest might not have been in vain - some cosmologists say that certain supergalaxies must take around 80 billion years to form!
Thus, many cosmologists are painfully aware of the time scale posed by the age of our universe, and posits much doubt on the validity of the Big Bang - whilst many observables in the universe seem to compliment the theory, just as physicist Lerner writes;
'Present evidence shows that the Big Bang initially introduced to explain the Hubble expansion, does not make predictions that correspond to observation. It is clear supercluster complexities arise and by the more recent confirmations of large-scale structures. This returns us to the problem; what caused Hubble expansion? The cosmological debate will not be resolved until this basic question is answered. The question of the Hubble remains unanswered until an adequate theory is found. Far more theoretical and observational work is needed.'
While complex structures like some certain supergalaxies take tens upon tens of million years to form, the issue of Hubble Expansion might never be fully understood. Just as Einstein informs us, until a more appropriate theory comes along, we can but stand in protest. Perhaps we might even find the long sought-after GUT - the grand unified theory. This mathematical theory, supposed to be only a few notations long would explain everything. In order to do this, some mathematicians are attempting to combine relativity theory and quantum mechanics together. If such an equation existed, it might even be simple enough that we might even have it as logos on t-shirts or even on school pencil cases!
I, however, do not believe we will ever discover the Unified Theory - i simply do not believe that all of the universes complexities will [allow] itself to be deduced so easily by humans.
Part Two
Our Galaxy
Right... let's encapsulate our universe, with some whole facts.
Our Sun is 15 million km away - and even at this large distance, it is still able to give us heat. The sun is always burning away at its fuel. In the suns core, it is 15 million degree Celsius and is 5 times denser than lead. Here, hydrogen atoms convert into helium atoms. As the nuclei of hydrogen form the nuclei of helium, the superfluous loss of mass is converted into pure energy. Each second, the sun converts 4 million tones of mass and will keep it burning for another 5 billion years or so.
The sun is 70% hydrogen, 28% helium and 2% heavy elements - the stuff earth is made of. The earth came from a 'Supernovae' 6 billion years ago. All planets and stars are thought to have come from the death of Supernovae - including our own solar system, where the sun makes up 99.8% of the mass.
The surface of the sun is called the 'photosphere' and it is a melting 6000 degrees Celsius. Outside the surface of the photosphere is the 'red chromosphere.' This inner solar sphere blasts out gas called 'prominences,' hurtling billions upon billions of electrically charged particles towards earth every second.
Our sun will eventually die out in 5 billion years time - and when it does it will expand 200 times larger and will consume mercury and Venus. By that time, it will be a red giant, and will scorch the earth to a cinder. Not the smallest organic life will survive. Once the sun has stripped away its outer layers and its core be exposed, it will shrink to the size of earth and become a 'white dwarf' - as it cools down and dims, it will then become a 'black dwarf' over time, and will leave us in eternal darkness - not that it should bother us by that time - we will all be long gone.
Our Galaxy, the Milky Way has something like 200 billion stars, being 100,000 lightyears across and 10,000 lightyears thick - light years measure how far light travel in one year - light will travel around 65.5 billion miles in one year.
It takes 222 million years for our sun to orbit the galactic center. Our galaxy is one of an estimated 50 billion in the universe, where some galaxies have grouped with 12 other galaxies, whereas others have grouped in thousands! They make up 'supergalaxies', which are thought to have supermassive black holes at their centers.
Part Three
Life
We have always been fascinated with life. We know that life, given the right conditions will thrive and teem in some of the harshest climates on earth. The elements of earth originated from the swirling disks of debris and remnant of supernovae, around 6 billion years ago that slowly began to fuse together - a process called accretion.
During the early years, the earth was highly volatile - nothing more than a molten rock, bombarded by asteroids crashing to earth for hundreds of millions of years. Then, as solar activity began to subside, everything in the observable universe began to take shape - however, life still had a long way to go, considering 'mobile matter' did not come into existence until only 4 billion years ago.
Volcanic eruptions constantly reshaped the face of the planet, forming the geological structures we see and admire today. By now, oceans had formed from volcanic condensed water vapor and also from large chunks of ice from comets carried to earth from deep space. In fact, 'Panspermia theory' states that comets could have brought 'polycyclic aromatic hydrocarbons' to earth, and could have brought the origins of life to earth in the form of simple microbes. The strongest evidence of this was announced, rather bizarrely by President Clinton standing on the Whitehouse lawn, saying that NASA had discovered evidence of possible life in the subsurface of Mars.
A cabbage-sized meteorite, found recently in Antarctica, dubbed ALH84001 that seemed to have come from the 'red planet' had in it tiny features, that according to NASA scientists could have been fossilized microbes. The only problem is that the little marks are under high controversy, and not every scientist is convinced it is in fact, fossilized Martian life. The skeptics however admit, the tiny marks do have all the appearances of bacterium - but are considered far too small to be living organisms - which is all very interesting, considering this presumed life came from an entirely different planet; you would expect some biological differences wouldn't you? However, NASA did find organic chemicals inside of the meteorite, including carbonates, which also included tiny magnetic grains that can be produced by bacterium - but such grains can be produced without the aid of life.
More importantly, was a recent discovery in 2006 that seemed to prove the existence of subsurface water channels. Recent photography of the red planet displayed that a substance that looks like water had seeped out of loose rocks on the planets rocky surface - which most geologists believe itself hold all the characteristics of being formed by water itself that might have flowed around 3.5 billion years ago! This discovery will indeed make scientists think twice about astrobiology in the future, considering water is one of the fundamentals needed to sustain life.
Gases from the interior of the earth created the early atmosphere, which were mainly nitrogen and carbon dioxide. And it is believed lightning was needed as a catalyst to charge the first simple organisms. These organisms needed four basic elements; they are carbon, nitrogen, oxygen and hydrogen. The first life would have been very simple, called 'prokaryotes,' which are single-celled organisms. It is thought that the single-celled life formed in hot springs, heated by the earth around 3.8 billion years ago. There is still evidence of them today, clinging to hot vents deep under the ocean... not changed after 4 billion years! It was only when they began to 'photosynthesize,' that the atmosphere changed. These photosynthesizing organisms released oxygen into the atmosphere.
Then, mulitcellular organisms came about and life began to double every 12 million years. However, its not been a steady ride for life at all! It has initially been very hard for any ecosystem to survive - this is because earth has undergone some heavily catastrophic events.
From what we know, nature first came from single-celled life, that eventually evolved into mulitcellular life - but a great extinction would wipe out nearly every life form off the planet, leaving the oceans decimated and empty. Then, very slowly, plants would begin to evolve, then the first insects, only to be wiped out in a second great extinction. This cycle repeated again and again until reptiles emerged dependant of the sea, only to be killed off again. Then dinosaurs came about, with the first birds, and fern plant life, yet to be destroyed in a 5th great extinction.
Only 100,000 years ago, homosapians (humans) appear. We have managed to survive an ice age 20,000 years ago - however, scientists warn us that the next great extinction is just around the corner. This is easy to imagine, especially when global warming accelerates at its disturbing rate.
O'k, that sums up life on earth... but what about life outside our own terrestrial sphere?
Scientists do not deny the rather, probable existence of alien life. After all, we live in a universe with infinite space and matter (well, not so much infinite matter. There are about 10^80 particles in our universe, but an infinite potential in the vacuum) - there must be an equally infinite amount of possibilities for a planet, just like earth, neither too hot, nor too cold, teeming with strange and wonderful life. However, whether alien life has the intelligence to master deep space travel is a whole other game.
Given the distances and energy required, it would far exceed a space crafts capabilities - it just seems unlikely that aliens have ever visited earth. Nevertheless, aliens must exist in my opinion - it would be selfish to presume we are the only life forms in the infinite vacuum of space and time. After all, if they are alien, what are we? In fact, during the writing of this book, astrologists discovered a planet extremely similar to our own, with a blue atmosphere, indicating that the atmosphere would probably contain similar gasses found here on earth. Only one problem... the planet a whopping 5 billion light years away... thus we won't be visiting this planet in the near-future.''
