Timeline for How to measure the mass of Earth?
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
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| Apr 30, 2015 at 1:01 | comment | added | José Jorge Medina Serna | Newton didn't deduce that g=9.8, was Gallileo. Mesuring the time that takes an object to fall, Gallileo estimmate that the freefall aceleration is 9.8 for all object (doesn't matter the mass of the object). The gravitation law was not based in the fact that the mass of the earth. I don't know exactly how Newton deduced it, but the law tell us that the gravitional force between 2 object is proportional to the mass of the onjects and the invert of square of the distance. | |
| Apr 29, 2015 at 21:59 | comment | added | user78939 | I think Newton estimated the mass of the Earth by taking the average density of rocks and multiplying by the volume of the Earth which was known since the time of Eratosthenes. | |
| Apr 29, 2015 at 21:55 | comment | added | dmckee --- ex-moderator kitten | "But the gravitation force was deduced based on the fact that the mass of the Earth was known." No, not really. The gravitational force was measured with a scale. The reason that didn't immediately give the value of $M_{earth}$ is that when you start $G$ is also unknown. | |
| Apr 29, 2015 at 21:19 | comment | added | Abc2000ro | But the gravitation force was deduced based on the fact that the mass of the Earth was known. But it wasn't. So how can you be sure that Newton's gravitation law is correct if you don't have the masses apriori so that you can first test that law ? | |
| Apr 29, 2015 at 21:15 | history | answered | José Jorge Medina Serna | CC BY-SA 3.0 |