The Intro:
How old is Earth? It is one of the first couple of questions people ask when talking about prehistory or space-related and an answer that is very straightforward. In short, Earth is around 4.54 billion years old. Yeah, it is that old and now you might be thinking how do we know Earth is this many years old. Well, other than the fact that first lifeforms appeared on Earth was around 3.7 billion years ago, it is not surprising that Earth would be a little more older than that. But you might be thinking that Earth was supposed to be 5000 years old.
Many people that I have asked thinks the same and not to worry I will explain it to you. Before I get into how did we know Earth is that old, I need to clarify the misconceptions people have with the age of our planet.
I thought Earth was only 5000 years old?:
Yes, you would be right with that number in many cases and it is something scientists, geologist and many people in the science area of things have yet to nicely & logically explain why Earth is not 5000 years old. One of the many signs and ruins prehistoric human civilization dates back 10,000 B.C. or 12,000 years from now. Back then, humans were mainly Hunter-Gatherer but that is the moment in time when the transition happened to be more Settlers. They started constructing very basic structures they could which helped with their survival other than being completely aimless wanderer because that would not be possible for us humans to become widespread like that and our survival chances would not increase.
Now, we know humans actually started civilization but when did we start recording history. Now, the first ever recorded history would be 3200 B.C. or 5200 years from now. Ahh!!! We finally arrived at the so-called age of Earth. So you see, just because we started recording history from then, us humans thought Earth was born yesterday or even a couple of years ago and stories like how Earth and the universe was made in 6 days but that would not never be possible. For us or anyone born would seem like Earth was made just yesterday now because how would you even know, right?
Which is why it is important that science have came about and it helps us explain things a lot more than normally. Think about it, ancient humans who had no education and had no knowledge about anything other than what he could do, what do you think he would have said if someone asked him how old was Earth, of course he would make up something which would then get passed on and on and proliferate that idea.
Many of us reading would fall into a religion at the very least and almost most of them would say that Earth is 5000 years old, accounted for when history was being recorded and also to coincide with the historical figures’ timeline as well. So, these historical figures would tell a version of the Earth’s age that would match with the predecessor and do their best to spread their religion of their time.
Which is why it has become a common knowledge that Earth is 5000 years old as it is passed down from generation and after all what we can see is what existed and nothing we cannot see did not exist which is also why many people believe that Dinosaurs are not real but Dragons are real because they associate Dinosaur fossils with Dragon fossils. And also, science is relatively when compared with religion and thus the spread of factual of information is also a lot less when compared with the idea set by religion and thus the misconception continues but this is where this post comes in to clarity everything.
So how old is Earth really?:
While the Earth really is 4.54 billion years old, give or take a million years but coming to this answer was more complex and hard than what any of us could have thought.
The quest for the ages began around 1800s when a famous Irish physicist and mathematician, yeah we are getting those subjects involved in for this one, Lord Kelvin, estimated that Earth was around 20-400 million years old based on the calculation on how long it would take for the surface lava to cool down as back then it would be more of just a boiling, molten magma ball. As an educated scientist as himself, his methods were correct but the answer was off by a lot more than he could expect.
Later on, scientist tried to use relative dating techniques to find out the age of the planet and this is where Stratigraphy comes in. Stratigraphy is the study of rock layers and this is done by comparing the configuration of layers of rock or sediment in order to determine an age of the rock compared with other rock layers.
The more you go down, the more older the layer is and this is also how paleontologists can know when a certain extinct animal lived. But this process cannot be tested chemically or any other way and the layers can have deviations, could be rearranged or bent which does not provide an exact number but what it did reveal was that Earth was billions of years older, not millions like previously thought.
But not to worry, as humanity’s science progresses further, our methods of testing becomes even more refined than before. Now, with the help of chemistry, geology and physics, scientists discovered a new method of by which the absolute age, an actual number of age, of a rock or mineral sample could be determined. That method, I believe many of you may already know, is radiometric dating. You might be wondering how does radiometric dating work and it is a little complicated but I will try to explain it as simple as I can.
Radiometric Dating, simply put, is when an isotope, an atom with an unbalanced number of neutrons in the nucleus of the same element but has a different atomic weight, of an unstable, radioactive element eventually decay into more stable element. But how does that help you might be asking and this is how. Every isotope element has a constant rate of decay and they always decay in halves.
So, let’s say you have 8 apples, and it takes 4 days for half of 8 apples to decay. After 4 days, you are left with 4 apples and another 4 days you are left with 2 apples and so on. This is called half-life. The elements with half-life does not fully decay into nothing which is why it can stay for longer periods of time.
So, what scientist do is that take a sample of a very old rock and measure the half-life of an isotopic radioactive element and thus you get the answer of billion of years old answer. Some of the oldest rock has been dated to be around 3.8 billion years old while some other tiny materials is dated around 4.2 billion years old. But there is a problem with and that is the rock cycle.
Rock cycle is the process of rocks changing and destroying and coming back as new rocks. Rocks change with enough time, heat and pressure. Some of the most oldest rocks may even be destroyed by the heat of the mantle or the movement of tectonic plates. And those rocks destroyed in the mantle, come back as new rocks from the volcanoes’ lava which is why we needed a sample that is not tampered with.
That’s why the dates mentioned in the previous paragraph has a 400 million years of difference and this is where our Moon and some meteorites come into help. As the samples of the Moon and meteorites are not tampered with rock cycle, the radiometric dating provides the number of 4.54 billion years old for the age of our planet Earth.
And there you go! You now have a nice conversation starter and now everyone in the room will become more smarter along with you. But don’t worry if others do not get it because as long as you get it, I have done what I wanted to do, spread the knowledge of our wonderful Earth and its prehistoric nature.
Now remember, the actual age of Earth is 4.54 billion years old and maybe give 500 thousand years. And the best way to support me in my endeavors is by sharing this with everyone who might be interested in this. And maybe also commission me for some dinosaurs art in Fiverr. I hope to see you again soon in my next post!!!
