# How to determine the diameter of Earth?

• oem7110
In summary, the conversation discusses the challenges of measuring the diameter of Earth and how this approach can be applied to measuring the diameter of other planets. Suggestions are given to use historical methods such as Eratosthenes' method or modern techniques such as studying the cut-off time of radio signals or using stellar occultation. It is mentioned that asteroids can also be sized using stellar occultation, similar to how a solar eclipse occurs.
oem7110
We cannot measure the diameter of Earth inch by inch using rulers, and must somehow estimate the distance on Earth, Does anyone have any suggestions on what approach they use to measure the diameter of Earth? and how does this approach apply to measure the diameter of other planets?
Thanks in advance for any suggestions

Google Eratosthenes, then google 'The Great Arc' and perhaps 'The Prime Meridian through Paris'.

And after that, maybe also google Struve Geodetic Arc

how does this approach apply to measure the diameter of other planets?

it doesn't.

A planet's diameter may be estimated by occultation, such as studying the cut-off time of a radio signal from an orbiting probe as it swings behind the planet.

Asteroids have been 'sized' by stellar occultation, where many observers watch for a star's cut-off time. From their position on Earth, the asteroid does or doesn't eclipse a background star.
http://www.physorg.com/news/2011-10-faraway-eris-pluto-twin-dwarf.html

Analogy is a solar eclipse, where folk off the centre-line see shorter and shorter eclipses...

## 1. How was the diameter of Earth first calculated?

The first recorded calculation of the Earth's diameter was done by the Greek mathematician Eratosthenes in the 3rd century BC. He used the angle of the sun's rays at two different locations on the same day to estimate the circumference and diameter of the Earth.

## 2. What is the current accepted value for the diameter of Earth?

The current accepted value for the diameter of Earth is approximately 12,742 kilometers (7,917.5 miles). This was determined through modern techniques such as satellite measurements and advanced geodetic surveys.

## 3. How do scientists measure the diameter of Earth?

Scientists use a variety of techniques to measure the diameter of Earth, including satellite measurements, precise ground-based surveys, and mathematical calculations based on the Earth's curvature. These methods take into account the Earth's shape, rotation, and gravitational pull.

## 4. How accurate are the measurements of the Earth's diameter?

The measurements of the Earth's diameter are very accurate, with a margin of error of only a few kilometers. This is due to the use of advanced technology and precise calculations. However, as the Earth's diameter is not a perfect circle and varies slightly at different points, there may be slight variations in the measurements.

## 5. Why is it important to know the diameter of Earth?

Knowing the diameter of Earth is important for a variety of reasons. It allows us to understand the Earth's size and shape, which has implications for various scientific fields such as geology, geography, and astronomy. It also helps us to accurately map the Earth's surface and understand its relationship to other objects in the universe.

• Earth Sciences
Replies
2
Views
1K
• Earth Sciences
Replies
42
Views
3K
• Astronomy and Astrophysics
Replies
48
Views
1K
Replies
4
Views
177
• Cosmology
Replies
11
Views
2K
• Science Fiction and Fantasy Media
Replies
0
Views
962
• Mechanical Engineering
Replies
19
Views
340
• Astronomy and Astrophysics
Replies
17
Views
2K
• Introductory Physics Homework Help
Replies
3
Views
832
• Electrical Engineering
Replies
9
Views
553