Age Of The Earth – And How To Put It Into Understandable Perspective

Since ancient times, humans have been fascinated by the age of our planet. Early scholars made guesses that seem far too young by today’s standards, while pioneering geologists later used emerging scientific techniques to make better estimates. Now with advanced methods like radiometric dating, scientists have narrowed down the Earth’s age to about 4.54 billion years, with an error of only 100 million years either way.

This vast expanse of Earth’s history and geology can be difficult for our human minds to grasp. To put the planet’s lifetime in perspective, this article explores some clever attempts throughout history to conceptualize Deep Time. We’ll also look at how researchers determined the Earth’s current accepted age based on evidence like radioactive decay. Along with reviewing key developments and events in our world’s geology over the eons, we’ll consider the relatively tiny sliver of time humans have existed.

Almost a century ago, a multitude of highly venerated academicians put a lot of effort into determining the Earth’s age. The figure they could come up with was 100 million years, only to be refuted by a more advanced study that came half a century later.

The then new study put the Earth’s estimated age at around 3 billion years. But sadly, this claim was also invalidated. The work must have been exhausting considering the lack of technology and sparseness of scientifically knowledgeable individuals during the time.

Now, scientists have determined the Earth’s age to be 4.54 billion years old, plus or minus 0.1 billion years. So how did they figure out this number? And how can we put this into a comprehensible perspective?

How Scientist Figured Out the Age of Earth

Estimating the age of Earth centers around finding the oldest piece of rock, and working out how old that rock is through a scientific technique called radiometric dating. Of all the methods, radiocarbon dating is the most popular. The process focuses on the ratio between radioactive isotopes of carbon – carbon-14 and carbon-12 – in any formerly living thing. This ratio determines that organism’s age.

The elements that can be dated are not limited to just carbon, because many other elements exist. For example, to determine the Earth’s age we use uranium-lead dating – the radioactive decay of uranium into lead. This is the oldest and most reliable of all isotopic dating methods.

Using this technique on ancient lead-filled zircon rocks found in Western Australia, we know the Earth is at least 4.4 billion years old. Other evidence from meteorites suggests the Earth is even older, so we tend to agree the planet formed 4.54 billion years ago, with an error of 0.1 billion years. The determined age of the Earth now seems very credible.

Putting the Age of Earth into Clearer Perspective

If you’re familiar with the concept of Deep Time – the time scale indicating the Earth formed about 4.5 billion years ago – we know humans struggle to comprehend the vastness of this span. And I can say with certainty that even if lay people try to make sense of such an immense period, the effort would be futile.

The issue here is that this concept falls victim to esoteric interpretation, so it’s best left to experts. However, many scientists, geologists and archaeologists stepped in, and came up with different analogies in an attempt to help us overcome this stumbling block.

D.J. Mahony was one of the iconic archaeologists of the 16th century. His analogy takes you down an avenue reaching into the past, where each step covers a thousand years. The first step would take you back to the Battle of Hastings, the second to the beginning of the Christian era, and the third to Homeric Troy. If you managed to walk more than 250 miles, you would arrive at the era of the most ancient fossil organisms. The man was a genius, but he exists only in history books now.

In the 18th century came James Hutton, considered by many the father of modern geology. From studying soils and rocks, he proposed Earth’s formation took much longer than Archbishop Ussher’s 17th century assertion: that the planet was created on the evening of October 22, 4004 BCE.

This may sound absurd, but if Ussher had not made such a preposterous claim, we could not have built the body of knowledge we currently possess.

In the 19th century, geologist Charles Lyell studied the Earth’s current geological processes to understand past changes. This gave rise to the idea of continental drift, later known as plate tectonics.

However, the concepts proposed by Hutton, Lyell and Wegener were initially met with repudiation before gaining acceptance.

From Pangaea – a supercontinent 200 million years ago that later split into the present continents – scientists have extrapolated these concepts of continental drift were valid. The processes have been recurring again and again.

Although speculations about the Earth’s origin and formation seem to conflict with radiometric dating, scientists continue working to gather evidence and reveal the exact age of Earth’s formation with new technologies.

Studying the Earth’s Interior

The Earth’s core, with a radius of almost 3,500 km (2,200 miles), consists of hot, molten material. Above it sits the mantle, a layer of semi-fluid material. This enables heated material to rise up and cooler material to sink down.

Through this process called convection, the Earth gradually loses heat layer by layer. Convection also weakens the crust, the region just above the mantle comprising magnesium-silicate and alumina-silicate layers that make up today’s landmasses. It also shifts the crust sideways, sometimes spewing out molten material in seafloor spreading.

Landmasses created by volcanism, faulting, and upheavals from continental collisions became exposed to the atmosphere. Eroded sediments were carried by water, wind and ice to be deposited in lower elevations or seabeds.

This ongoing crustal deformation has continued through time, consolidating into a complex surface.

Geologic Time Scale

Here we have the geologic time scale break down to help you put the age of earth in better perspective.

An Overview on the Aforementioned

The Precambrian period spans over 80% of Earth’s geologic record. Due to its vast length, it was divided into the Archean and Proterozoic Eons. Numerous deformations, major orogenies (mountain formation), erosion, deposition including ice ages occurred then.

Evidence of the Precambrian exists on every continent as shields rich in minerals and elements like iron, cobalt, copper, nickel, silver and gold.

The Paleozoic era had six divisions: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.

Trilobites, fusulinids, blastoids and other marine fossils emerged in the Cambrian, but most of these invertebrates went extinct due to climatic warming at the end of the Proterozoic ice age.

The Ordovician was the period of greatest marine transgression. Reef systems and marine fossils from the tropics to the arctic can still be seen.

Prior to Pangaea incorporating almost all landmasses, the continents had different shapes. From Paleozoic rocks we get gas, oil, marble, slate, limestone, hematite, zinc and lead.

The Silurian was relatively tranquil. Terrestrial life began flourishing with scorpions and millipedes. Diversification of marine life also continued.

The Devonian was mostly calm too, with some upheavals. Flora and marine fauna proliferated. It marked the rise of fish and amphibians.

The Mississippian and Pennsylvanian (Carboniferous) periods were known for swamp vegetation, ending with the Permian’s major orogenies and widespread deserts plus glaciation in the southern hemisphere.

The Mesozoic era had the Triassic, Jurassic and Cretaceous periods. It is best known as the dawn of dinosaurs, but many smaller reptiles, birds and mammals also emerged. Most modern plants and animals originated then. It ended with orogenesis and cold climatic conditions.

The Cenozoic era continues to the present day. It began 65 million years ago. The continents acquired their current positions and configurations during this time, after previously having different shapes.

Gauging the magnitude and duration of major Cenozoic events like mountain formation, volcanism, earthquakes and faulting provides perspective on the scale of time in which humans emerged.

While the immensity of Earth’s nearly 4.5 billion year history remains abstract for us mortals, reviewing the major milestones, catastrophes and shifts that shaped our modern landscapes and lifeforms allows some insight. The story of our planet is one of constant change – breaking apart and reforming continents, catastrophic extinctions giving way to new species’ dominance, violent upheavals and tranquil periods both.

Looking back through the lens of geology makes it clear just how young we are as a species. Homo sapiens emerged only 200,000 years ago, barely registering on the timeline of Earth’s existence. Yet armed with our ingenuity and curiosity, we’ve been able to piece together the ages-long processes, occurrences and events that came before us. As we continue studying our world’s almost unfathomably long past, what new perspectives might we gain on our own ephemeral lives and future?