Discovering the Mass of Earth: How Did Scientists First Calculate It?

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In summary, The mass of the Earth was originally estimated by using the Cavendish experiment, which was conducted approximately 200 years ago. This experiment involved suspending a rod from a thread and measuring its movement in response to a large object of known mass placed near it. The gravitational constant was then calculated, allowing for the computation of the Earth's mass using the formula M=gr^2/G. This method may seem strange, but it has been proven to be an effective way of estimating the Earth's mass.
  • #1
argonurbawono
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i know nothing about astronomy, so please excuse my silly question here.

how did people originally estimate the mass of earth?

i sense our current data of Earth mass (10^24 kg? or so) has been there for quite sometime. how did they do it?
 
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I forget the name of the experiment, but ~100 years ago, a scientist suspended a rod from a thread. He knew the resistance the thread would have in keeping the rod from spinning. Then he put a large object of known mass near the rod and watched how much the rod moved. Kinda like how much the Earth's magnetic field makes a compass needle turn. Except this "compass needle" responded to gravity.

Measuring how far it moved and knowing how hard the thread would resist this motion, he calculated G, the gravitational constant. With that, he used the formula g=GM/r^2, re-written as M=gr^2/G. g is known. It's 9.81 m/s/s. r is known. It's 6378000m. Now that he knew G, M is computable.

** edit **
Cavendish experiment. Just Google for "weighing the Earth" or "Cavendish experiment" and you'll get a whole collection of web sites describing the experiment in detail. I pretty much got it right. But it was ~200 years ago.
 
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  • #3
thanks.

i feel it is very strange that gravitational force can be observed in that way. if it were just an experiment proposal, i would definitely say it wouldn't work.
 

1. How is the mass of the Earth estimated?

The mass of the Earth is estimated using a variety of methods, including measuring the gravitational pull of the Earth on objects in orbit, studying the Earth's motion around the sun, and analyzing data from satellite missions.

2. What is the current estimated mass of the Earth?

The current estimated mass of the Earth is approximately 5.97 x 10^24 kilograms.

3. How accurate is the estimated mass of the Earth?

The estimated mass of the Earth is considered to be very accurate, with a margin of error of only a few percent. This is due to advancements in technology and data collection methods.

4. Has the estimated mass of the Earth changed over time?

Yes, the estimated mass of the Earth has changed over time as our understanding of the Earth's composition and gravitational pull has improved. However, the changes have been relatively small and the current estimate is considered to be the most accurate.

5. Why is it important to accurately estimate the mass of the Earth?

Accurately estimating the mass of the Earth is important for a variety of reasons. It helps us understand the Earth's composition, its gravitational pull, and its relationship with other celestial bodies. It also has practical applications, such as for satellite missions and space travel.

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