How Do Scientists Measure the Radius of the Earth?

In summary: But basically what I did was take a series of pictures of a landmark at Yaquina Head and then used a computer program to try and match it up to the pictures. In summary, Scientists measure the radius of the Earth by taking pictures of a landmark and then using a computer program to try and match it up to the pictures. They come up with a result much closer then I believed possible.
  • #1
Koveras00
21
0
May I know how scientist measure the radius of the earth?

And how accurate it is??
 
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  • #2
http://opal.physik.uni-bonn.de/~mkobel/pos/deleg/zapp/zapp1.htm [Broken]
 
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  • #3
The first person to measure the circumference (and thus by calculation the radius) of the Earth was a Greek by the name of Erosthothenese (spelled horribly wrong). He traveled between two cities in Italy and measured the angle of the sun in a well. From there its simple geometry.
 
  • #4
Originally posted by russ_watters
The first person to measure the circumference (and thus by calculation the radius) of the Earth was a Greek by the name of Erosthothenese (spelled horribly wrong). He traveled between two cities in Italy and measured the angle of the sun in a well. From there its simple geometry.

YES! His name is spelled "Eratosthenes", and he (in any inertial frame of reference) da man!

A more modern method used to independently verify this measurement is satellite VLBI. "VLBI" stands for Very Long Baseline Interferometry, and involves two satellites looking at a common object. The two satellites can be placed at a known altitude (using radio altimeters), with a known difference in global position. For example, they could be placed 90o from one another so that when one is directly over the North Pole, the other is directly over the equator. For this example, let us suppose there is a Quasar perfectly lined up with the Earth's axis, so that both satellites can see it by looking directly "North".

Now, quasars have a signature EM wave pattern. Both satellites will see this distinctive pattern, but the satellite directly over the pole will see it first. By measuring the difference between the two wave patterns (how they "interfere" with one another) we can determine how far apart the two satellites are. This gives us an extrasolar source for our measurement. Submitting the information from this alternate source to the same geometry used by Eratosthenes, we can get independent verification of his measurement.
 
  • #5
A few years back Sci. Am. had an article which told of a method to measure the radius of the Earth from a promintory above the sea.

I tried it from Yaquina Head on the Oregon coast.

We must have made some canceling errors because we came up with a result much closer then I believed possible. It's been 20+ yrs so I really can't remember the specifics.
 

1. How is the earth's radius measured?

The earth's radius is measured using a variety of methods, including satellite measurements, triangulation, and the use of specialized instruments such as a laser rangefinder or a theodolite. The most accurate measurement to date is 6,371.2 kilometers, based on satellite data.

2. Why is it important to measure the earth's radius?

Measuring the earth's radius is important for a variety of reasons. It helps us understand the size and shape of our planet, which is crucial for navigation and mapping. It also plays a key role in scientific calculations, such as determining the force of gravity, understanding the earth's orbit, and studying the earth's interior.

3. How has the measurement of earth's radius changed over time?

The measurement of earth's radius has changed significantly over time as technology has advanced. Early estimates were based on simple calculations and observations, while modern measurements rely on highly precise instruments and satellite data. As a result, the accuracy of the measurement has improved significantly over the years.

4. What challenges are involved in measuring the earth's radius?

There are several challenges involved in accurately measuring the earth's radius. One of the main challenges is accounting for the earth's irregular shape, as it is not a perfect sphere. Additionally, factors such as variations in topography and atmospheric conditions can affect the accuracy of measurements. Another challenge is obtaining measurements from remote or inaccessible areas.

5. How does the earth's radius compare to other planets?

The earth's radius is approximately 6,371 kilometers, making it the fifth largest planet in our solar system. It is smaller than Jupiter, Saturn, Uranus, and Neptune, but larger than all other planets, including Mars, Venus, and Mercury.

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