The solar system was created from the debris of a cosmic explosion. The Earth and its neighbouring planets mercury, venus, and mars, coalesced from this debris at the same time, and in the same way, over a long period of time. It has been estimated that the Earth was formed roughly 4,550,000,000 years ago. The early Earth was a fiery place where volcanic eruptions greeted continual showers of meteorites, "Infant Earth was a huge ball of rock covered with molten boiling lava." Movie - 212 kb and 13 seconds long.

‘The Day the Earth was Born’ proposes that 25 million years after its formation, the Earth became a molten ball of rock with temperatures around 1200C, "Four and a half billion years ago the Earth was an undifferentiated sphere of rock. Volcanoes spewed vast amounts of lava onto the hot, seething surface. Our hostile planet was about to endure the first of several momentous events that would change it forever. Radioactive elements trapped when the planet was formed were heating it from inside. At the same time, Earth’s gravity was pulling in huge quantities of debris from space, a bombardment that generated excessive amounts of heat on the surface. The combined effect was catastrophic. At eight minutes past midnight on the Earth clock, (about 25 million years after the formation of the Earth i.e. 4,525,000,000 years ago) the entire planet was like a furnace."

In this molten state, iron melted and sank towards the centre of the Earth, "We think the earth, at some point, was totally molten, a big droplet of melt just floating in space. When you have a totally molten droplet like this, the heaviest elements, and that includes things like iron, would sink to the centre of this droplet and the lightest elements, things rich in carbon and water, for instance, the light elements, would float to the top and float there like algae on a lake." (Michael Zolensky, Nasa)." earth003web.mov - 192 kb and 6 seconds long.

The iron catastrophe turned out to be a blessing in disguise for the life that was to eventually emerge on Earth. It was one of a myriad number of factors that would later help to ensure the survival of life on the planet, "As the liquid iron swirled around it produced an invisible force that even today helps keep us alive: the Earth’s magnetic field. Convection currents inside the liquid core behaved like a dynamo and generated electric currents. These transformed our planet into a giant magnet with north and south magnetic poles." earth004web.mov - 188 kb and 7 seconds long. "Without the liquid iron core the early atmosphere would have been stripped away and life could never have evolved on our planet. That’s because space is lethal. It’s full of highly dangerous solar particles that can be ten times more deadly than the radiation from a nuclear explosion. These particles originate from the sun when it spews out massive solar flares. A devastating solar wind streams towards the Earth at 250 miles per second. That’s a million miles an hour. If it ever reached the surface of our planet it would strip away the atmosphere in a few thousand years. But the Earth’s magnetic field creates a protective shield and deflects the solar particles. Without the molten core, today our planet would be a sterile rocky sphere with little or no atmosphere. The tragic fate that befell our neighbouring planet, mars." earth005web.mov - 756 kb and 23 seconds long.

"The time had reached 16 minutes past midnight (about 50 million years after the formation of the Earth i.e. 4,500,000,000 years ago). The iron catastrophe was over, leaving the rocks at the surface depleted in iron. Large areas were cooling and solidifying but the Earth was still hostile and uninhabitable. Incessant volcanic eruptions poured hot gases into the thick, turbulent atmosphere. This alien landscape was enveloped in a noxious mass of hydrogen sulphide, methane, and steam. Humans could not have survived here. There was no oxygen to breathe and no ozone layer to block the lethal ultra-violet radiation."

It took another catastrophe to bring about the creation of the moon. In 1974 Bill Hartmann (of the Planetary Science institute) proposed that the moon was created when a rocky planetesimal left over from the formation of the solar system smashed into the Earth, "The time was approaching 16 minutes past midnight on our 24 hour clock. The rogue object, about the size of mars, was moments away from collision with Earth. The heat of the impact melted both the planetesimal and the outer layers of the Earth. Together they fused into one planet, a new larger Earth. Vast amounts of molten rock were ejected into orbit. Over the next few thousand years, the debris coalesced to form the moon." earth007web.mov - 1012 kb and 34 seconds long. Art bell & whitley strieber also believe the moon was created this way. They speculate that the impact of the collision created what is now the pacific ocean."

Art bell & whitley strieber argue, "Over time, the gradually increasing drag of the moon’s gravity slowed down the rotational wind of the earth, which would otherwise blow in excess of two hundred miles an hour."

After the Earth's impact with the planetesimal the planet’s axis became tilted. "The immense collision that formed the moon also caused our planet’s axis to tilt over at an angle of 23 degrees." earth009web.mov - 556 kb and 15 seconds long. The degree of tilt changes from one extreme to the other over tens of thousands of years so that as the Earth orbits the sun it constantly shows a slightly different face to the sun. This tilt is what causes the Earth to experience a variety of seasons giving it a much more equable climate than would be the case without such a tilt. See the video clip from aubrey manning's bbc2 documentary, 'Earth Story', earthstory04.mov - 1 mb and 26 seconds long.

The Earth revolves around the sun whilst rotating around its tilted axis. But the Earth’s axis does not remain in an unchanging tilted position. It also wobbles - in the same way as a spinning top - because of the gravitational pull of the other planet's in the solar system. (See the video clip from aubrey manning's bbc2 documentary, 'Earth Story', earthstory05.mov - 692 kb and 16 seconds long). Without the moon, the Earth could have wobbled either into a perpendicular position (which would mean no seasons on Earth) or onto its side (which would mean only one side of the Earth receiving any sunlight). The creation of the moon dramatically avoided such extremes. 'The Day the Earth was Born' concludes, "Without the stabilizing influence of the moon, the Earth would wobble dramatically about it axis, the planet would experience wild fluctuations of weather, making it impossible for anything but the most primitive life forms to survive."

(See the following videos taken from Aubrey Manning's bbc2 documentary, 'Earth Story':

The creation of the moon was another factor that would later help the planet to become more habitable. It reduced the Earth’s rotational winds. It tilted the Earth’s axis changing the face of the Earth receiving solar radiation and thereby minimizing the extremes of the Earth’s climate. The moon also reduced the Earth’s wobbling motion which further helped to stabilize the Earth’s climate. Art bell & whitley strieber conclude, "The balance of the earth-moon system is exquisite. Were it not for the moon being just the size that it is and orbiting the earth as it does, nothing more complex than a lichen would ever have evolved here." By themselves neither the planetesimal nor the Earth would have been capable of sustaining life. The collision between them resulted in the formation of the moon which, in effect, sacrificed all of its own chances of sustaining life in order to make the Earth habitable. The barren, lifeless, inhospitable, moon made it possible for life to emerge and survive on Earth.

Simon Wilde of Curtin University found zircon crystals in the jack hills of western australia. They are the only remnants of minerals left over from the Earth’s earliest period. He has been analyzing these crystals to speculate about the conditions prevailing on the early Earth. According to ‘The Day the Earth was Born’, "Simon’s discovery suggests that the Earth must have recovered very rapidly after the trauma of the moon’s formation. The age of the zircons revealed our planet must have cooled and formed a crust as early as 12 minutes to one in the morning on our clock (about 150 million years after the formation of the Earth i.e. 4,400,000,000 years ago). These tiny crystals are last surviving fragments from the first hour of the Earth’s life."

The Earth had been created from an accretion of meteorites and, for hundreds of millions of years after its formation, it continued to be bombarded by meteorites, debris from the explosion that created the solar system, "For the first 600 million years of its life (up until 3.10am on the Earth’s 24 hour clock), our planet was constantly battered by comets and asteroids. This is known as the great bombardment. These missiles could measure 300 miles across." earth018web.mov - 428 kb and 29 seconds long.

American geologist Stephen Mojzsis at the University of Colorado, Boulder, USA, also carried out experiments on the zircon crystals found in the jack hills of western australia, "In january 2001 stephen announced he had made a revolutionary discovery. The oldest zircon crystals contained a type of oxygen called oxygen 18. Oxygen 18 could only have been present if the crystals had grown in the presence of large quantities of water. Geologists had previously believed that large amounts of water first appeared around one billion years after the formation of our planet. The oxygen 18 revealed that water was present on the surface of the Earth much sooner, as early as 200 million years after its formation. The time was still only 12 minutes to one in the morning." He argues, "By 200 million years after the formation of the Earth (about 4,350,000,000 years ago or 3 minutes past one on the 24 hour clock) you can imagine a landscape of islands and small continents bathed by a primitive ocean where in these zircons were formed." (Stephen Mojzsis).

If there had been any life on the planet before the Earth’s collision with the planetesimal, it would have vanished after the impact, "When a giant body collided with our planet soon after its birth, the outer layers were completely vapourized creating our moon. Any complex Carbon molecules that existed on Earth would have been entirely destroyed by the massive impact."

Early Earth hardly seemed conducive to life, "Early Earth was hostile: an extreme place for life to emerge. It was smothered in a thick, turbulent atmosphere. There was no oxygen and the ultra-violet radiation was lethal. The young sun was weaker than it is today. Its feeble light would have barely penetrated the noxious atmosphere. Carbon dioxide would have mixed with the pungent smell of hydrogen sulphide."

Whenever, and wherever, life may have begun on Earth it eventually moved to the surface of the oceans. According to ‘The Day the Earth was Born’, "On our 24 hour clock, it was now 5 o’clock in the morning. (950,000,000 after the formation of the Earth i.e. about 3,600,000,000 years ago). The great bombardment was over. Most of the debris in the solar system had been swept up and there were far fewer violent impacts on Earth. Microbial life was able to emerge from its protective hiding places. It began to flourish close to the surface and take advantage of a new, powerful, source of energy — the sun. These bacteria evolved a green pigment, chlorophyll, which enabled them to harness the sun’s energy through Photosynthesis and convert Carbon dioxide into Carbohydrates. As the Earth cooled, this new generation of cells began to spread across the oceans. Immense colonies of green slime took over the world and the greatest transformation in the history of our planet was set in motion." earth026web.mov - 556 kb and 32 seconds long. J john sepkoski jr believes Photosynthesis started soon after the Earth became cool enough for life, "Some of the oldest rocks on Earth (were) laid down 3.8 billion years ago. Some chemical analyses suggest there is a 12C surplus in these rocks, and if this is true life must have put it there. As evidence of Photosynthesis it would be startling because it comes a mere 200my at most after the Earth grew cool enough to live on."

The first known Photosynthesizer was Cyanobacteria. This micro-organism relied on the absorption of hydrogen sulphide from the atmosphere to convert sunlight into energy, "Today the green and purple sulfur bacteria still use hydrogen sulphide as their electron donor in photosynthesis. In the early days photosynthesis was largely dependent on a steady source of hydrogen sulphide, and the gas was converted into yellow sulphur deposits on the ground or into globules in the water that were later oxidized to make ocean sulphate." These micro-organisms created strange structures known as stromatolites in the shallow oceans.
(Further videos of stromatolites:
earth027web.mov - 1.7 mb and 60 seconds long;
earth029xweb.mov - 640 kb;
earth016web.mov - 968 kb and 23 seconds long.)

As new types of Photosynthesizing Cyanobacteria began to emerge, some developed the ability to carry out Photosynthesis using water instead of hydrogen sulphide thereby releasing oxygen into the environment. The oxygen released by Photosynthesizers did not immediately begin to accumulate in the atmosphere/stratosphere. It oxidized (rusted) the iron dissolved in the seas which then sank to the ocean floor. "It was still only 5.45 in the morning (1,000,000,000 after the formation of the Earth i.e. about 3,550,000,000 years ago) and the most significant change in our planet was about to begin. Stromatolites had spread out across the entire planet. To derive their energy they absorbed sunlight and Carbon dioxide from the atmosphere and produced a waste gas that would transform the entire planet - oxygen. earth028xweb.mov - 520 kb. At first, all the oxygen was absorbed into the oceans. Underwater volcanoes were spewing out iron from erupting lava. The iron dissolved in the sea water and chemically reacted with the oxygen. It fell as minute iron oxide particles to the ocean floor. Over the next 700 million years the planet literally rusted. All the iron was turned into oxide building up layer after layer of what would become the most significant mineral deposits on Earth — iron ore." earth028web.mov - 1mb and 19 seconds long.

It was only after the oxygen released by Photosynthesizing micro-organisms had oxidized vast quantities of hydrogen, sulphur, and iron, that it was possible for oxygen to accumulate in the oceans/atmosphere, "Once the reduced iron ran out, there was no other chemical sink big enough to hold the continuing biological surge of oxygen and this gas built up, first dissolved in water and then escaping into the atmosphere." Lynn margulis & james lovelock argue, "Prokaryotic microbes (Cyanobacteria) were almost certainly responsible for the original transition to the oxygen-containing atmosphere about 2000 million years ago ..." Unfortunately, the precise rate at which oxygen accumulated in the atmosphere is not known. "When there was no iron left to react with, the excess oxygen from the stromatolites began to build up in the atmosphere. Slowly but surely the planet was transformed. Over the next 8 hours the microbes raised the level of oxygen from less than 1 per cent to the present level of 21per cent. The time was 9pm. Without the cyanobacteria there would be no oxygen and Earth would still be smothered in noxious gases. There would be no plants and animals, and humans would never have evolved."

Lovelock argues that Photosynthesis is the only source of oxygen on Earth, "No one now thinks seriously of oxygen as anything other than a vegetable product. It is easy to forget, though, that 20-30 years ago serious papers were published suggesting that oxygen mainly came from photo-dissociation of water vapour in the upper atmosphere of the Earth." Clive carpenter supports the hypothesis, "Photosynthesis is the source of all the oxygen in the atmosphere." It should be pointed out that there are still commentators who believe that .. "loss of water as vapour was split in the stratosphere and hydrogen escaped."

Lovelock proposes that Photosynthesizers preserved water on Earth. There is considerable disagreement about this proposition.

The conventional scientific assumptions about the presence of water on Earth are firstly, that the water cycle is the dominant feature of the Earth; secondly, that the water cycle rather than Photosynthesis, stabilizes the Earth's climate; and, thirdly, that water is the primary life sustaining process on Earth - Photosynthesis being of only secondary importance.

According to lovelock, if it wasn’t for Photosynthesizers, the planet would have rapidly lost its water, "Water on the Earth enabled life, but without life the Earth would now be dry."; .. "without life and oxygen, the oceans of the Earth would in a billion years (of the origins of the Earth) have vanished forever."

Surprisingly, decentralist greens, most of whom are opposed to space technologies, also propound the view of the Earth as a ‘blue Planet’. In previous publications it has been argued that such greens aren’t green at all but should be regarded as ‘blues’.

Lovelock also raises the issue as to whether Photosynthesizers are responsible for keeping a constant level of water on Earth thereby preserving not merely marine life, but most other life, on Earth, "Keeping the Earth moist, keeping it suitable for organisms, is a cliff hanging existence. If about 25% of the water now in the oceans had dried away, ocean life would not be possible for most organisms." This is a question which, as far as is known, he has not answered.

Photosynthesizers preserved water on Earth and, in effect, prevented hydrogen, one of the lightest elements on Earth, from floating through the atmosphere and escaping into space. They played two critical roles in preventing the escape of hydrogen. Firstly, they extracted hydrogen (in the form of water) from the atmosphere to form Carbohydrates and, secondly, they released oxygen into the environment which reacted with hydrogen to form water. If hydrogen had escaped from the planet’s atmosphere then eventually the Earth would have lost all its water. If, in the future, the Earth should ever lose its capability for Photosynthesis then hydrogen would resume its drift through the atmosphere and be lost to space and the Earth would begin to dry up.

The preservation of water on Earth, courtesy of Photosynthesis, was vital for enabling volcanic islands to grow into continents. Volcanic eruptions contain basalt which, when heated in water, forms granite - the basis of the Earth’s continents.

The presence of free oxygen in the oceans/atmosphere led to a major genetic leap, the emergence of eukaryotic cells, "The world became oxygenated enough through the Photosynthesizing mats (created by Cyanobacteria) to be suitable for their development (nucleated cells) about 2,000 million years ago." Bacteria, prokaryotic life forms without nucleated cells, gave rise to a more complex form of life - Protista, eukaryotic life forms with nucleated cells.

The first Protista life forms were soft bodied marine invertebrates - some of which also acquired the ability to carry out Photosynthesis. Cyanobacteria and Photosynthesizing protista extracted Carbon from the atmosphere but after these individual micro-organisms died, the Carbon contained in their bodies was returned to the atmosphere. It is believed that about a billion years ago, some of the Photosynthesizing marine Protista developed the ability to grow shells using the Carbon acquired through Photosynthesis. This completely changed the destination of the Carbon contained in their bodies which had a fundamental impact on the Earth’s atmosphere and climate, "Although ‘merely’ protoctists, foraminifera are one of the most diverse groups of fossil forming small organisms. An astounding variety of magnificent shells are made by these complex single-celled beings .." As a consequence, the shells of dead Algae sank to the ocean floor permanently removing Carbon from the atmosphere. The burial of Carbon shells liberated an equivalent quantity of oxygen allowing it to accumulate in the atmosphere. Oxygen didn’t start accumulating in the Earth’s atmosphere until after banded iron formations ceased to appear approximately 1.8bya. But it wasn’t until 1 bya ago that micro-organisms developed shells which permanently buried Carbon on the ocean floor thereby ensuring the accumulation of oxygen in the atmosphere.

Over millions of years, vast quantities of Algal shells accumulated on the ocean floor and were crushed, under their own weight and the water above them, into layers of limestone rock. Sedimentary rocks cover vast areas of the ocean floor .. "calcium carbonates, which cover 10% of the continental crust, were generated by life ..." Over the course of time, as the Earth has changed, sedimentary layers of rock at the bottom of the Earth’s oceans have ended up in rather incongruous places. Some have been exposed by falling ocean levels and currently form the landscape of many countries e.g. the white cliffs of dover. Others have been ended up on the tops of mountains after collisions between tectonic plates e.g. sedimentary rocks can be found on the top of the himalayas. (See the video clip taken from Aubrey Manning's bbc2 documentary, 'Earth Story': earthstory03.mov - 196 kb and 8 seconds long).

As basaltic islands grew into granite continents they were invaded by micro-organisms and Plants. Michael benton states, "The first plants moved on to land during the silurian period (439-409mya), with simple small forms like Cooksonia ..."

Richard fortey suggests the greening of the land wasn’t completed until after the silurian period, "There have been many changes since the greening of the Earth in the devonian (409-363mya)." The greening of the Earth was important because it boosted the scale of global Photosynthesis. Richard fortey alleges the invasion of the land by micro-organisms and Plants was followed shortly thereafter by marine Animals, "So the backboned animals followed shortly after the plants made their excursions on to land."

After a vast period of time during which the Earth was dominated by micro-organisms, Photosynthesizers helped to bring about a critical evolutionary change. The oxygen generated by Photosynthesizers brought about a second genetic change, the emergence of Animals .. "there are no documented cases of any metazoa (animals) that can complete their life cycles in the total absence of O2. All Animals are composed of cells that divide by mitosis. The mitotic cell division itself requires O2." All Animals need oxygen to breathe but, more fundamentally, Animal cell division would never have been possible without the presence of oxygen in the atmosphere.

Earth, venus, and mars, were formed at the same time and through the same processes. After they cooled, they were covered in something resembling a global ocean and had massive quantities of Carbon in the atmosphere. Venus and mars lost their surface water but retained all the Carbon in their atmospheres. On the other hand, the Earth still has its oceans but has little Carbon in the atmosphere. The reason for these differences is that, on Earth, Photosynthesizers extracted Carbon from the atmosphere and conserved water on Earth. Over the aeons, the Earth’s Photosynthesizers have reduced the concentration of Carbon dioxide in the atmosphere from 30% to 0.04%, "Mars and venus, and the hypothetical dead Earth devoid of life, all have chemically stable atmospheres composed of over 95% Carbon dioxide. Earth as we live on it, however, has only 0.03% of this stable gas in its atmosphere. The anomaly is largely due to .. the process of photosynthesis. Bacteria, algae and plants continuously remove carbon dioxide from the air via photosynthesis and incorporate the Carbon from the gas into solid structures such as limestone reefs and eventually Animal shells."

Tim radford estimates that, throughout the Earth’s history, Photosynthesizers have extracted a gargantuan 10,000,000,000,000,000 tons of Carbon from the atmosphere. Photosynthesizers have brought Carbon down to Earth and transformed it into life forms, soils, mountains, cliffs, land, sea floors, etc.

There was one other major consequence of Photosynthesizers extracting Carbon from the atmosphere - the cooling of the Earth. Photosynthesizers’ ability to extract Carbon from the atmosphere has been vital in cooling the Earth - although it was only when Photosynthesizers acquired the ability to grow shells, permanently removing Carbon from the atmosphere, that they could play a long term role in keeping the Earth cool.

Photosynthesizers transformed the Earth from a planet which could provide a habitat only for simple life forms into one which was suitable for complex life forms. It transformed the Earth from being virtually uninhabitable into a luxuriously habitable planet. But Photosynthesizers also posed a danger to the Earth — by extracting all the Carbon from the Earth’s atmosphere they could plunge the planet into an ice age or, quite possibly, a permanent deep freeze. Although the Earth has experienced ice ages from time to time none of them became permanent. Fortunately for the Earth’s climatic stability, increasing numbers of life forms fed on Phytomass and released Carbon dioxide or methane back into the oceans/atmosphere. Micro-organisms living in the muds and sediments at the bottom of lakes, marshes, rivers, and the oceans, release vast quantities of methane into the atmosphere and boost the greenhouse effect. This was, and still is, a vital part of the Earth’s climate stabilization system, "A world with photosynthesizers only is unstable. They would soon have locked up in their bodies most of the available carbon. Their removal of carbon dioxide would have so weakened the greenhouse that the world would have frozen, and life ceased. This never happened. There co-existed with the photosynthesizers simple fermenters, the methanogens. These organisms processed the organic matter made by the photosynthesizers and returned the carbon to the air as a mixture of methane and carbon dioxide, restoring the greenhouse." If, early in the Earth’s history, Photosynthesizers had removed all the Carbon from the atmosphere, the Earth would have frozen because solar radiation wasn’t intense enough by itself to keep the Earth warm.

All life absorbs Carbon from the environment and releases it back into the environment - including Photosynthesizers. The Earth needs Carbon producers as a counterweight to Carbon absorbers, Photosynthesizers. What it doesn’t need is unrestrained Carbon pollution. In the past, large parts of the Earth froze when Photosynthesizers removed too much Carbon from the atmosphere. Although the sun’s solar radiation has increased significantly over the last few aeons it still doesn’t provide enough heat by itself i.e. without the aid of greenhouse gases, to prevent the Earth from lapsing into a global ice age. But the depth of a present day ice age would be nowhere near as deep and long-lived as that which could have been created in the past because of the greater intensity of solar radiation. Solar radiation is destined to go on increasing until it burns up the Earth. However, at present, the dangers facing life on Earth have nothing to do with the Earth burning up because of increasing solar radiation nor the planet freezing to death because of the absence of greenhouse gases. The danger is a runaway global burning disaster brought about by increasing anthropogenic greenhouse gases and the anthropogenic scalping of the Earth’s Photosynthetic cover.

It is not known whether the Earth was the only planet in the solar system to develop life-forms nor whether it was the only planet to have Photosynthesizers. It is possible that mercury, venus, and mars, all had life forms including Photosynthesizers. There may be dozens of factors which were critical for the survival of Photosynthesizers on Earth e.g. the moon’s influence over the Earth. Whatever they were, once Photosynthesizers had established themselves on Earth they were able to keep the planet cool - this is the main role they have fulfilled for the last couple of aeons. Perhaps there was also another stroke of luck in that during the aeons when Photosynthesizers were gently, imperceptively, cooling the Earth, no species emerged which fed on Photosynthesizers and threatened their survival on Earth.

The history of the Earth’s global temperatures is not known with any degree of accuracy. It is difficult assessing the precise contribution of all the different, and sometimes opposing, factors influencing the Earth’s early climate. However, in broad terms, it can be summarized as follows. During its formation and for millions of years thereafter, the Earth’s temperatures were fiery. Meteorite impacts, continual volcanic eruptions, high levels of nuclear radiation in the mantle, and dense levels of Carbon in the atmosphere, kept the Earth hot. Although the sun was much cooler than it is now, the Earth had so much Carbon in its atmosphere it was able to retain a much larger proportion of solar radiation. Gradually, however, as meteorite impacts, volcanic eruptions, and nuclear radiation, contributed less and less to global average temperatures, the Earth began to cool. It cooled enough for the formation of a global ocean. If the Earth hadn’t had so much Carbon in its atmosphere then it is likely it would eventually have frozen - at that time solar radiation was not sufficient by itself to keep the Earth warm. It was the presence of vast quantities of Carbon in the Earth’s atmosphere that prevented global freezing. As the aeons passed the sun’s continually increasing solar radiation would have caused the Earth to overheat if the large amounts of Carbon in its early atmosphere had persisted. This didn’t happen because Photosynthesizers extracted Carbon from the atmosphere and cooled the climate. The Earth has thus never become either too hot, or too cold, for life to survive. On the one hand, the Earth faced the threat of a permanent ice age if Photosynthesizers extracted all the Carbon from the Earth’s atmosphere. On the other, it faced the threat of a runaway global burning disaster if polluters dumped too much Carbon back into the Earth’s atmosphere.

The Earth’s Photosynthesizers also help to preserve the Earth’s ph balance ensuring that it never becomes too alkaline or too acidic. Lynn margulis argues, "The breathable oxygen, the humid air, and mildly alkaline oceans result from the growth and metabolism of uncountable and always changing numbers of bacteria, plants, and algae, which produce oxygen using solar energy."

Photosynthesis also helps to maintain the ocean’s ph balance, "By laying down limestone skeletons, Polyps remove carbon dioxide from the atmosphere and thus play a major part in lowering the temperature of the Earth’s surface. According to jim lovelock, they may also play a role in regulating the salt balance of the oceans. Given that the seas receive copious quantities of mineral salts every year through run-off from the land, it has always been a mystery how salt levels in the sea have remained so constant. Coral reefs may provide part of the answer. As they build up over thousands of years, they form lagoons and closed seas, effectively creating natural evaporation basins. Exposed to the sun, these basins eventually dry out, leaving behind enormous salt deposits. Large quantities of salt are thus removed from the seas. Significantly, all the major salt deposits on land are contained within limestone barriers - which suggests that this process has been going on for millenia."

In the Carboniferous period (363-290mya) large Trees began to emerge. The first big Trees were the gymnosperms which extracted huge amounts of Carbon from the atmosphere. When the climate changed and Forests sank into swamps Phytomass was eventually crushed into layers of coal, oil, and gas, "Their production (gymnosperms) was so rapid that the swampy environment of their growth would soon become oxygen deficient. Some of the organic Carbon is preserved in the form of thick coal seams." Thomas algeo suggests that .. "in the short interval from 400 to 380 million years ago, the size of the biggest land plant soared from inch-short dwarfs to hundred-foot giants, an amazing case of evolution in action."

During the Paleozoic era, Photosynthesizers continued to release oxygen into the environment but, much more critically, the demise of shell forming Photosynthesizers led to the burial of Carbon on the sea bed thereby setting free the oxygen component of Carbon dioxide. The accumulation of oxygen in the troposphere led to the emergence of the stratospheric ozone layer. It is not known whether the stratospheric ozone layer emerged in parallel with the build up of tropospheric oxygen or developed only after oxygen had reached saturation point in the troposphere.

Conventional scientists believe it was only after the formation of the stratospheric ozone layer that Plants and Animals emerged from the oceans to colonize the land. They believe that ultra-violet radiation posed a serious threat to life on Earth - not forgetting that solar radiation at that time was less intense than it is now. Richard fortey represents this viewpoint, "The explanation that the level of oxygen had reached a critical level for the respiration of large Animals has a pleasing continuity with the role of the humble, inconspicuous photosynthesizers, which had transformed the atmosphere through the previous vast stretches of geological time .. Oxygen may have increased to a point where it was sufficient to supply a protective ozone layer high in the atmosphere, which served to shield vulnerable animal tissues from harmful radiation."

In contradistinction to this conventional view, lovelock believes that life’s colonization of the land was not threatened by ultra-violet radiation and that the creation of an oxygen atmosphere and a stratospheric ozone layer occurred after the colonization of the land. J john sepkoski jr argues that Photosynthesizing Cyanobacteria, which lived in the shallow waters producing stromatolites, were not damaged by ultra-violet radiation, "Ultra-violet radiation from the sun does not harm cyanobacteria that exude their insulating mucus, a very efficient sunscreen."

Dorian sagan & lynn margulis believe that Photosynthesizers have stabilized the level of atmospheric oxygen for the last 300 million years. If oxygen declined too much then the higher Animals would have been asphixiated. On the other hand, if it rose too much there would have been large scale conflagrations, "Thus the quantity of oxygen in the atmosphere must have remained relatively constant since the time that air-breathing Animals have been living in Forests - which has been over 300 million years."

The first Plants to colonize the land had virtually no roots, "The earliest land plants were confined to a rhizome, an underground stem that could put out shoots but did not sink a solid grip into the ground." When these Plants died they decayed and created soils. The decomposition of terrestrial Photosynthesizers led to the creation of soils, "No cubic centimetre of the soil and sediment beneath is without its billions of microscopic organisms: the top soil has its photosynthesizing bacteria and nitrogen fixing microbes often attached to the roots of plants; its fungi, stones, moulds and teeming invertebrate life. The air in the soil is rich in carbon dioxide pumped down by life; dissolved in water near the rock surface, this causes rock weathering, speeded by microorganisms. Without life there would be no soil, but only regolith, the rock rubble of dead planets." Tyler volk states,"Without life and thus soil, every sunny day would be a drought, every rain a flash flood." As soils became deeper, Plants grew bigger, more complex, and their roots became longer.

Terrestrial Plants, especially Trees, absorb Carbon from the atmosphere and then pump it through their roots into the soil. In the soil it forms Carbonic acid. This reacts chemically with rocks creating chemicals and minerals which are nutrients for Photosynthesizers. Some of these nutrients leech through the soil to the sea where they are absorbed by marine Photosynthesizers. This boosts the burial of Carbon on the sea floor. The bigger the Photosynthesizers, the deeper their root systems, the greater the amount of Carbon pumped into the soil, the greater the extraction of nutrients, the greater the quantity of nutrients leeching into the sea, the greater marine Photosynthesis. The process of rock weathering is beneficial not only to terrestrial Photosynthesizers but to marine Photosynthesizers.