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How Old is the Earth?

Updated: Feb 3

In the Christian tradition, the first thing you are told is that God created the earth in six days, and rested on the seventh. Before I was exposed to science, or philosophy, or, indeed, before I could understand what was right in front of my eyes, I was taught from the Bible. Yet, as I was exposed to more things both tangible and intangible, I started to wonder about the veracity of it all.

Einstein brought the world his theory of general relativity during the early parts of the 20th century, that is to say, how space and time interacts in the grand scheme of things. One of the first questions I remember asking was; is time truly constant? I reached a point in my life where I started to feel as though one day was very much shorter than what I remember it being as a child. Could it be that time was speeding up? The truth of it is that the answer is not a simple yes or no. One second in time remains one second. However, after one has experienced 10 years, 20 years, or in my case, 50 years of it, one second becomes an ever shrinking fraction of the whole. Thus, one would experience it both in its concrete form but also as the part of the whole that it represents. Therefore, to the observer, it may be that time, or the experience of it, speeds up.

The obvious next question, therefore was; has a day always been a 24-hour construct. Has the earth always taken this long to rotate once on its own axis? Again, the answer isn't a simple one. As it happens, the length of one day has varied over time due to the influences of forces, both within and without the earth, that have either lengthened or shortened the time that we experience a day to be in the time we live in. Regarding the long term, over millions of years, earth rotation has been slowing down due to friction effects associated with the tides driven by the moon. That process adds about 2.3 milliseconds to the length of each day every century. This means that just a few billion years ago an Earth Day was only about 19 hours.

The caveat to this has been that for the past 20,000 years, another process has been working in the opposite direction, speeding up its rotation. When the last ice age ended, melting polar ice sheets reduced surface pressure, and Earth's mantle started steadily moving toward the poles. Just as a ballet dancer spins faster as they bring their arms toward their body – the axis around which they spin – so our planet's spin rate increases when this mass of mantle moves closer to Earth's axis. This process shortens each day by about 0.6 milliseconds each century.

The bottom line is, our days are getting longer. And they have been getting longer since the beginning of the world. Already, this places a question mark over the literal interpretation of the biblical timeline in terms of creation. This is not to say that it is untrue, just misinterpreted.

I often refer to myself as an evolutionary creationist. What this means is that I apply scientific method and common sense to Scripture, as it is found in the Bible. Ironically, it is this marriage between faith and science that has grown my faith immensely during my lifetime. There came a day when I read 2 Peter 3:8 ...

Beloved, do not let this one thing escape your notice. With the Lord a day is like a thousand years, and a thousand years are like a day.

For me, this was my eureka moment. At once, I recognised Einstein's theory of general relativity and understood what it was like to exist outside of time, outside of the presence of forces that would act upon and change the nature of something.

It was at this time that I realised that it was the word "day" that was getting people confused. A day, as we understand it, is only a day in one place – earth. Of the eight planets in our solar system, every other one has a day that is either longer or shorter than ours. Therefore, if one were to accept a literal translation of Scripture, then the Bible would become untrue anywhere other than on planet Earth. I do not personally believe that the word of God becomes void anywhere!

So, instead of using the word day, I started using the term epoch. What I mean by that? Well, as it turns out, the world as we know it has been made and remade five times. We are living in the sixth epoch. So, when were these other epochs and what characterised their transitions, one to another? As per geological and fossil records, the earth has undergone what is known as five extinction level events, each marking the end of one of these epochs.

1. The Ordovician Period & late Ordovician mass extinction (LOME)

The Ordovician is a geologic period spanning 41.6 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 million years ago.

During this time, there existed four primary continents – Gondwana, Laurentia, Siberia, and Baltica. A fifth smaller continent, Avalonia, had just split from Gondwana at this time, moving north towards Baltica and Laurentia, opening the Rheic Ocean between itself and its parent body. The northern hemisphere was predominantly covered by the Panthalassic Ocean.

Life on earth during that time was made up predominantly of filter feeding organisms, brachiopods, trilobites, echinoderms, corals, bivalves, and graptolites. It was the culmination of the Cambrian explosion which saw a multitude of species appear in our fledgling oceans.

At around 443 million years ago, the LOME event began. It is believed to have consisted of two "pulses". The first was characterised by a glaciation which abruptly expanded over Gondwana and shifted the Earth from a greenhouse to icehouse climate. Cooling, and a fall in sea level, led to habitat loss for many organisms along the continental shelves. The second "pulse" occurred as the glaciation abruptly receded and warm conditions returned. It was characterised by intense worldwide oxygen depletion and toxic sulphide production, which persisted thereafter.

This event killed 85 percent of the fauna and flora on the planet.

The Devonian period & late Devonian extinction event

The Devonian is a geologic period and system spanning 60.3 million years from the end of the Silurian, 419.2 million years ago, to the beginning of the Carboniferous, 358.9 million years ago. It is named after Devon, England, where rocks from this period were first studied.

Devonian palaeogeography was dominated by the supercontinent of Gondwana to the south, the small continent of Siberia to the north, and the medium-sized continent of Laurussia to the east. Major tectonic events include the closure of the Rheic Ocean, the separation of South China from Gondwana, and the resulting expansion of the Paleo-Tethys Ocean. The Devonian experienced several major mountain-building events as Laurussia and Gondwana approached; these include the Acadian Orogeny in North America and the beginning of the Variscan Orogeny in Europe. These early collisions preceded the formation of Pangaea in the Late Paleozoic.

The Devonian period saw the first significant diversification of life on dry land occurring. Free-sporing vascular plants such as ferns, horsetails, and lycophytes began to spread, forming extensive forests which covered the continents. By the middle of the period, several groups of plants had evolved leaves and true roots, and by the end of the period, the first seed bearing plants appeared. Arthropod groups including centipedes and millipedes, spiders, and insects became well established early in this period.

Fish reached substantial diversity during this time, leading the Devonian to be referred to as the Age of Fishes. The placoderms (armoured fish) began dominating almost every known aquatic environment. The ancestors of four limbed vertebrates began adapting to walk on land, as their strong pectoral and pelvic fins gradually evolved into legs. Primitive sharks also became more numerous. The first ammonites, a subclass of molluscs, appeared. Trilobites, mollusc-like brachiopods, and the great coral reefs were still common.

The late Devonian extinction consisted of several events within that epoch taking place over a period of 23 million years. Two significant events, the Kelwasser event and the Hangenberg event brought about the extinction of 75 percent of the world's species, most of which were marine invertebrates that lived at the bottom of the sea. It was a period characterised by global warming and cooling, a rise and fall of sea levels and a reduction in oxygen and carbon dioxide in the atmosphere.

The Permian period & the Permian extinction

The Permian is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 251.9 million years ago. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia.

The world at the time was dominated by the supercontinent Pangaea, which had formed due to the collision of Euramerica and Gondwana. Pangaea was surrounded by the super ocean Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior.

The Permian witnessed the diversification of the two groups of amniotes, the synapsids (mammals etc) and the sauropsids (reptiles). Amniotes, which could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors.

At least three, possibly four extinction events made up the Permian extinction. The end of the early Permian saw a major faunal turnover, with most lineages of primitive pelycosaur synapsids becoming extinct, replaced by more advanced therapsids. The major Capitanian mass extinction event was associated with the eruption of the Emeishan Traps at the end of the Capitanian stage of the Permian. The Permian ended with the Permian-Triassic extinction events, the largest mass extinction in history in which nearly 81 percent of marine species and 70 percent of terrestrial species died out, associated with the eruption of the Siberian traps. Large amounts of carbon dioxide emitted by the volcanic eruptions elevated global temperatures, and in the oceans it led to widespread anoxia and acidification.

The Triassic period & the End-Triassic extinction event

The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251 million years ago, to the beginning of the Jurassic Period 201 million years ago.

During the Triassic, almost all the earth's landmass was concentrated into a single supercontinent, Pangaea. The supercontinent was more or less centred on the equator and extended between the poles. Southern Pangaea, also known as Gondwana, was made up by closely appressed cratons corresponding to modern day South America, Africa, Madagascar, India, Antarctica, and Australia. North Pangaea, also known as Laurasia, corresponds to modern day North America and the fragmented predecessors of Eurasia.

Three categories of organisms can be distinguished in the Triassic record: survivors from the previous extinction event, new groups that flourished briefly and other new groups that went on to dominate the Mesozoic era. Reptiles, especially arcosaurs, were the chief terrestrial vertebrates during this time. A specialised subgroup of arcosaurs, called dinosaurs, first appeared in the late Triassic but did not become dominant until the succeeding Jurassic period.

The causes for the Triassic – Jurassic extinction event are the subject of a few theories. Gradual processes such as climate change, sea level fluctuations, or a pulse of oceanic acidification late during the period may have reached a tipping point. However, the actual effect of such processes on Triassic animal and plant groups is not well understood.

Impact from a meteor or comet has also been suggested but no crater on earth has been discovered that coincides with the Triassic – Jurassic boundary. A third culprit may have been massive volcanic eruptions, specifically the flood basalts of the Central Atlantic Magmatic Province (CAMP) that might have released carbon dioxide or sulphur dioxide into the atmosphere, causing intense global warming (from the former) or cooling (from the latter). Either of these conditions would have put pressure on certain species, as well as added to oceanic acidification which would have contributed to marine extinctions.

The Cretaceous period & the Cretaceous – Paleogene extinction event

The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.

During the Cretaceous, the supercontinent of Pangaea completed its tectonic breakup into the present day continents, although their positions were substantially different. Gondwana had begun to break up during the Jurassic period, but this fragmentation accelerated during the Cretaceous and was largely complete by the end of the period. South America, Antarctica, and Australia drifted away from Africa, though India and Madagascar remained attached to each other until around 80 million years ago. Thus, the South Atlantic and Indian oceans were newly formed.

On land, mammals were generally small in size, but a very relevant component of the fauna, with cimolodont mutituberculates (the ancestors of modern day rodents) outnumbering dinosaurs in some sites. Neither true marsupials nor placental's existed until the very end of the period, but a variety of non-marsupial metatherians and non-placental eutherians had already begun to diversify greatly, ranging as carnivores, aquatic forages and herbivores.

The apex predators were archosaurian reptiles, especially dinosaurs, which were at their most diverse stage. Avians such as the ancestors of modern day birds also diversified. They inhabited every continent, and were even found in cold polar latitudes. Pterosaurs were common in the early and middle Cretaceous, but as the period proceeded they declined for poorly understood reasons.

Approximately 66 million years ago, there was a sudden mass extinction of 75 percent of the plant and animal species on earth. It marked the end of the Cretaceous period. In the geologic record, the event is marked by a thin layer of sediment called the K – PG boundary which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.

It is believed that the K – PG extinction event was caused by the impact of a massive asteroid, 10 - 15 kilometres wide, which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton. This impact hypothesis was bolstered by the discovery of the 180 kilometre Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s. It provided conclusive evidence that the K – PG boundary clay represented debris from an asteroid impact.

All of the aforementioned epochs, and their culminations, meant that the world had to reset, beginning again in its evolutionary path. We, as human beings, are now the dominant specie on a planet which, as history has shown, can change track on the top of a dime. It should not be thought that these have been the only catastrophic events in Earth's past. As recently as 13,000 years ago, remnants of a comet impact on us as we traversed through the Taurid meteor trail. We do this twice a year, but at that point, we came into contact with rather large fragments which abruptly brought the last ice age to an end, killing most of the megafauna in the northern hemisphere, and bringing our last ice age to a watery end. It is this event that has been strongly linked to Noah's flood in the Bible as well as the Epic of Gilgamesh from Sumerian mythology.

I truly believe that all one needs to confirm for oneself the incredible age of the universe we inhabit and, by extension, the planet we call home is to ask one simple question; how far is the furthest visible star from us? Considering that light travels in a constant velocity over time, and that the distance covered is called "light years", the answer should be quite apparent. After one has wrapped one's head around the fact that we go back far further than we can even imagine, the next obvious question is this – are we the first iteration of civilisation in our world? Based on the calamities that have befallen us, and the gaps in time between them, I would suggest that we are not, and that we might not even be the most advanced that has ever been.

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