The Earth, How Big is it Really?

How would you weigh something as big as the Earth? There is not a scale large enough to just prop the Earth on top. These three scientists figured out a way to measure the Earth over 200 years ago. Charles Hutton, John Michell, and Henry Cavendish were brilliant scientists that had lived during the 18th century. Astronomy during that century was booming and many people wanted to answer the age old question, how big the sun, moon, and Earth really is.

Charles Hutton: The Designer of the Scale

 

Charles Hutton was a mathematician who was a part of a group of researchers trying to figure out the density of a mountain in Central Scott Highlands, called Schiehallion (Bryson). After some long and arduous research, Hutton had eventually created contour lines, which are basically straight lines that show that elevation stays consistent if you go along those straight lines. From these contour lines, Hutton was able to deduce a general estimate of the mass of Earth, which he predicted to be around  5,000 million million tons (Bryson).  All of this was based on the mass of a mountain, sound crazy? Assumptions built on assumptions, yet Hutton was actually close to the actual mass of the Earth. Contour lines are used all the time on maps to show the elevation of mountains and hills, or even used to express the elevation of the sea. Without contour lines, we would not know that elevation stays consistent when a straight line is drawn from it. Which is crucial information to know when Hutton was calculating the mass of Schiehallion. Charles Hutton’s contributions to Geology had impacted the geology boom that was going on in the 18th century, eventually inspiring our next scientist.

John Michell: The Creator of the Scale

 

John Michell created an apparatus to accurately deduce the weight of the Earth. Due to Charles Hutton’s experiments with the mass of Earth, John Michell was inspired as well.  The apparatus John Michell had come up with “...incorporated weights, counterweights, pendulums, shafts, and torsion wires. At the heart of the machine were two 350-pound lead balls, which were suspended beside two smaller spheres” (Bryson). The apparatus looks similar to Newton’s balancing cradle with the framework being similar, except there were two balls and they expressed two different things.  The idea of the machine was to measure the gravitational deflection of the smaller sphere on the side using the bigger one. This allowed the gravitational constant to be measured, which in turn led to the mass of the Earth being measured. John Michell was never able to do this himself due to dying early. Before his death, he had handed his research and apparatus to a scientist by the name of Henry Cavendish.

 

Henry Cavendish: The User of the Scale

 

Henry Cavendish in his later years of his life had finally decided to use the apparatus to measure the scale given to him by John Michell. By using the apparatus, Henry Cavendish discovered that the Gravitational constant was 0.0000000000667310 Nm2/kg2 (Union), which then allowed Cavendish to go on and calculate that the Earth weighed six billion trillion metric tons. Based on modern day research and technology, the best estimate scientists could come up with for the weight of the Earth is “5.9725 billion trillion metric tons, a difference of only about 1 percent from Cavendish’s finding” (Bryce). Having said this, Cavendish was really dang close to his calculations and scientists today were only able to figure out that number due to the technology available to them.

 

 

 

 

 

 

Conclusion:

Now that you have gone through history and have determined the mass of the Earth, Can you think of anything else that is very difficult to measure with today’s technology? One thing I can think of that is difficult to measure is dark matter. Scientists have come to the consensus that, “research shows that the dark matter particles can neither be super light nor super heavy unless there is a force acting on it that is yet unknown” (DowntoEarth). Dark matter is a very talked about topic in the scientific community today. You could search Dark Matter and the latest news would be about new discoveries about it. Are we able to accurately describe something as not heavy or light without knowing the specific weight? Do objects truly have a weight or are they given a weight once we have measured it ourselves? Comment your thoughts below!

Works Cited

Britannica, T. Editors of Encyclopaedia (2021, March 22). James Hutton. Encyclopedia Britannica. https://www.britannica.com/biography/James-Hutton

Bryson, Bill. A Short History of Nearly Everything. Abridged. New York: Random House, Inc, 2003.

How did mankind first determine the mass of the Earth, and what is the known value today? (2002, June). Retrieved April 20, 2021, from https://www.uu.edu/dept/physics/scienceguys/2002June.cfm#:~:text=A%20kilogram%20of%20mass%20weighs,and%20the%20gravitational%20constant%2C%20G.

Sangomla, A. (2021, January 28). Dark matter not 'SUPER HEAVY' or 'SUPER LIGHT': In a first, scientists calculate its mass range. Retrieved April 21, 2021, from https://www.downtoearth.org.in/news/science-technology/dark-matter-not-super-heavy-or-super-light-in-a-first-scientists-calculate-its-mass-range-75243#:~:text=%22This%20is%20the%20first%20time,mass%20range%20for%20dark%20matter.&text=Calmet%20and%20Kuipers'%20research%20shows,it%20that%20is%20yet%20unknown.