# What is the distance between the Earth and Sun?

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Distance from the Sun to Earth is about 147.2 million km or 93 million miles. This distance between Earth and Sun is also known as AU or Astronomical Unit. It’s a primitive element that comes in handy to find the distance between the earth and unknown planets, Stars, etc. For a measurement, tape to measure a table length. Here 1AU is the measurement scale.

# How can we measure the distance between the earth and the sun?

Since 1961, after the discovery of radar, scientists have been using this device to measure the distance between planets. Before that, astronomers rely on trigonometry and another relative planet Venus. Venus and the earth revolving the sun in the same plane; that’s why they choose Venus for this calculation, and I hope you know why they choose trigonometry.

Because they two revolve around the same plane, at some point, Earth-sun-venus will come at 90 degrees(as shown in the image). Where the game begins; The distance between the earth and Venus is determined as a*cos(e). With little more calculation, we find the distance between the Sun and Venus as a*sin(e). Here e is the sun-earth-venus angle.

The famous astronomer Aristrachaus calculated this geometrical measurement method. His reasoning is correct, but the measurement is wrong. He said the sun is about 19 times farther than the moon. But it’s 390 times. Another Greek astronomer, Eratosthenes, determined this distance as the unit of the stadium that is either 40,80,000 stadia or 80,40,00,000. Later, converting this to modern units. It turns out that only 150 meters to 168 million km.

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The second one almost comes to the actual measurement range. Later 1672, Cassini measured the distance using the Parallax measurement technique. In 1961, astronomers sent radio waves repeatedly and measured the distance between Venus and earth.

From this, they applied mathematics to find the distance between the earth and the sun.