Since time immemorial, human beings have been curious by nature. They have always been trying to measure and understand the length and magnitude of things to learn more about our planet. One of the aspects that has always been a mystery to humans is the Earth's radius. Since we can't drill into the Earth's crust and travel to the core, we must learn to estimate and calculate the planet's radius. Thanks to some scientists who created a model to measure this length, we have been able to estimate it with increasing accuracy. Furthermore, solar radiation that reaches Earth is also a relevant aspect when it comes to understanding the dynamics of the planet.
In this article we are going to tell you what the radius of the Earth is and how it has been measured.
Problems measuring the radius of the Earth
As we know, despite the fact that technology has advanced at tremendous rates, our planet still has many unknowns. There are many areas of the planet that are not accessible to humans. An example of this is the seabed. There is still no technology that is capable of overcoming the pressure of the water and the little amount of sunlight that is found in marine trenches. The same is true of the center of the Earth. Numerous novels have been described about a journey to the center of the Earth but it is something that is still inaccessible to us. The most i know has been able to dig deep have been about 12 kilometers. This is just lifting the thin skin of an apple.
Since it's impossible to dig down to the Earth's core, different methods have had to be found to estimate the Earth's radius. One of the main reasons why it's impossible to dig down to the Earth's core is the high layer of thick, resistant rocks. High-tech methods can't drill through all these kilometers of deep rock. Another disadvantage is the temperature of the Earth's core. The inner core is at a temperature of about 5000 degrees Celsius. Faced with such a temperature, there is no human being or any machine that can withstand these conditions. Finally, at these depths neither is the oxygen that can be breathed.
Despite all these problems in measuring the Earth's radius directly, humankind has come to a standstill. Different models have been discovered to estimate its value. For example, one can use the seismic waves to study the composition of the Earth's internal layers. These methods can indirectly determine the depth at which an earthquake occurs. We can learn about different aspects of the planet without having to see everything with our own eyes. This can be useful for understanding how the Earth behaves. Earth's core and its impact on natural phenomena.
Plate tectonics theory and Eratosthenes
The theory of plate tectonics has helped a lot in understanding how the planet works. It is said that the continental crust is divided into different tectonic plates that move continuously. The cause of displacement is due to convection currents of the earth's mantle. This movement of plates is known by the name of continental drift. Furthermore, this theory is fundamental to understanding how tectonic plates behave and their relationship with the earthquakes.
Convection currents in the Earth's mantle are caused by the density differences between the materials within it. We can determine all of this thanks to various types of indirect measurement methods. We've always sought out different methods to find measurements for everything. The first scientist to be able to measure the radius of the Earth was Eratosthenes. This measure has always had people in suspense since ancient times.
At that time there was not much technology available to be able to measure the radius of the Earth. Therefore, this first method consisted of some very rudimentary elements. Keep in mind that, by this time, these rudimentary methods were considered a revolutionary technology. One of the most important elements that was used to measure the radius of the Earth was the importance of the Summer Solstice.
Eratosthenes took a papyrus from a library and noticed that a post on it did not cast any shadows. He thought it was because the sun's rays hit the Earth's surface completely perpendicularly. This is why Eratosthenes he was curious to know what the radius of the Earth was. The way to measure the radius of the Earth was later when he traveled to Alexandria. There he would repeat the experiment and see that the shadow of the sun was 7 degrees. After this measurement, he realized that the difference with the other shadow he experienced in Siena was reason to know that the Earth was round and not flat as was believed at that time. This is related to the study of different phenomena such as those that can be caused by a solar storm.
Eratosthenes formula to measure the radius of the Earth
Once he completed several experiments, he obtained several experiences of these measurements. From there, he began to formulate a few theories that helped measure the radius of the Earth. Most of the process was based on estimates and deductions. His main deduction was based on the fact that if the Earth was a 360 degree circumference, one fiftieth of that circumference would be 7 degrees. This part of the total circumference was what was measured in the shadow in Alexandria.
Knowing that the distance between the two cities of Siena and Alexandria was 800 kilometers, he was able to deduce that the radius of the Earth was 6.371 km. Keep in mind that, at the time I was calculating Eratosthenes, it was quite complex to be able to get the measurements right. However, he gave figures quite close to what is known today.
Nowadays there are other ways to measure the interior of the earth thanks to the seismic waves. Depending on the material it is made of inside and the distance it is from the center of the earthquake, the depth can be determined.
I hope that with this information you can learn more about what the radius of the Earth is and how it was measured for the first time.