Earth is not the largest planet in the solar system (far from it) , but it is not light either: it weighs 5.975 trillion tons. In fact, our planet is the densest world in the solar system (despite being the fifth largest). How is it possible? The explanation is because it is one of the few rocky planets in our solar system (composed mainly of silicate rocks or metals and have a solid surface). The largest planets, such as Jupiter or Saturn, have a gaseous density (they are mainly composed of hydrogen, helium and water in various physical states).
The density of the Earth is: 5.514 g/cm³ (for comparison, that of Mars is 3.93 g/cm³, that of Venus 5.24 g/cm³, that of our star, the Sun, 1.41 g/cm³). cm³ and that of Saturn, just 0.69 g/cm³).
How did scientists determine the weight of our planet?
Logically, we cannot place the planet on a scale. Efforts to determine the weight of planet Earth began as early as the 18th century . The experts studied the gravitational attraction that the planet has on other objects and used mathematics to calculate its size. That is, the measure of the weight of the planet is derived from the gravitational attraction that the Earth has for objects close to it.
But, initially, the English physicist Henry Cavendish, to make the initial calculation of the Earth in 1778 , was based on the law of universal gravitation formulated by the English physicist Isaac Newton. Newton showed that, for spherical objects, the simplified assumption can be made that the entire mass of the object is concentrated at the center of the sphere. And Cavendish used this starting point by devising a somewhat rudimentary apparatus with lead spheres, but which helped him determine the gravitational force of the large and small spheres. Actually, in all honesty , what he did was make some minor improvements to the invention of seismologist John Michell (who was also a priest) to measure the attraction between two lead balls of 0.73 kilograms and 158 kgs.
How exactly did you calculate the mass of the Earth?
He measured the force of attraction between metal spheres with the help of a torsion balance. He already knew the mass of both spheres and the distance between them. By carefully measuring the force between these spheres, he calculated their gravitational attraction. Since the Earth’s gravitational force on the smaller ball could be measured by weighing it, the ratio of the two forces allowed the Earth’s density to be calculated, using Newton’s law of universal gravity.
Cavendish concluded that the Earth weighed 6,600,000,000,000,000,000,000,000 kilograms or 6,660 trillion tons. It’s funny how the results of their study were pretty accurate when compared to the results of other recent finds.
Despite the elementary way in which Cavendish calculated how much the Earth weighed, he was not too far wrong in his figure because, over the centuries, this number has only been corrected by 10%. It is currently known that our planet weighs, as we have mentioned before , 5,975 trillion tons.
Did you know that the Earth is getting lighter every year?
Scientists estimate that about 95,000 tons of hydrogen gas are lost from Earth’s atmosphere to outer space each year. Although there are other processes involved, such as loss of mass due to radioactive decay within the Earth’s core (about 160 tons per year) and loss of helium from the atmosphere (about 1600 tons per year), it is about a fairly small effect.
And it gains about 40,000 tons of dust from meteor storms, for example, so a conservative estimate implies that the Earth is losing about 50,000 tons of mass every year. However, given that the mass of the Earth is about 5.975 trillion tons, it would take about 120,000 trillion years to completely disappear at this rate of depletion. That’s many millions of times the age of the universe, so we don’t have to worry.
Referencia: John Michell and Henry Cavendish: Weighing the Stars. Russell McCormmach The British Journal for the History of Science Vol. 4, No. 2 (Dec., 1968), pp. 126-155 (30 pages) Published By: Cambridge University Press www.jstor.org/stable/4025143
