Since time immemorial, the human being has been curious by nature. He has always been trying to measure and know the length and magnitude of things to learn more about our planet. One of the aspects that has always been unknown to humans is the radius of the Earth. Since we cannot pierce the earth's crust and travel to the core, we must learn to estimate and calculate the radius of the planet. Thanks to some scientists who created a model to be able to measure this length, it has been possible to estimate with more and more accuracy.
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 is not possible to excavate until reaching the Earth's core, different methods have had to be found to estimate the radius of the Earth. One of the main drawbacks why it is not possible to dig down to the earth's core is the high layer of thick and resistant rocks. High-tech can't drill all these miles of deep rock. Another drawback is the temperature at which the earth's core is. And is that the inner core is 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 the fact that there are all these problems to be able to measure the radius of the Earth directly, the human being has stopped. Different models have been discovered to be able to estimate its value. For example, seismic waves can be used to study the composition of the inner layers of the Earth. These methods can get to know the depth at which an earthquake occurs indirectly. We can know different aspects of the planet without having to see everything with our own eyes.
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.
The convection currents of the earth's mantle are given by the differences in densities that exist between the materials of the interior. All this we can know thanks to different types of indirect measurement methods. We have always been looking for different methods to be able 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 when he noticed that a post on it did not reflect any type of shadow, it was due to the fact that the rays of the sun fell on the earth's surface in a completely perpendicular way. This is the reason 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. Here I would repeat the experiment and see that the sun's shadow was 7 degrees. After this measurement, he realized that the difference between the other shadow that lived in Siena was reason to know that the Earth was round and not flat as was believed at that time.
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.
Today there are other ways to measure the interior of the earth thanks to seismic waves. Depending on the material of which it is composed of the interior and the distance that is from the center of the earthquake, the depth can be known.
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.