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The distance between the Earth and the sun

The sun is located in the center of the solar system, and a large number of planets, asteroids and comets revolve around it, due to the influence of the sun’s gravity on it.

 

There are planets in the solar system very close to the sun that have a very high temperature and planets far from the sun that are very cold.

Mercury is the planet closest to the sun, as it is 29 million miles, equivalent to 47 million kilometers from the sun.

There are objects that are very far from the sun, such as those in the Oort Cloud, which are a group of cold bodies that lie 9.33 trillion miles away from the sun, equivalent to 15 trillion kilometers.

The planet in which we live is an appropriate distance from the sun that makes it moderate in temperature for living organisms, and this is crucial and is considered one of the most important elements of life on planet Earth.

Scientists call the distance between the earth and the sun as the “astronomical unit” and this distance is 149597870700 meters.

The astronomical unit is used to measure the distances between the bodies within the solar system. For example, we say: Jupiter is 5.2 astronomical units away from the sun, and Neptune is 30.07 astronomical units.

Scientists do not use astronomical units to measure distances outside the solar system but instead use the one light-year .

A light year is the distance light can travel in a period of time estimated as one Earth year.

For example, the closest star to the sun is about 4.25 light years away.

Earth’s orbit is elliptical

We said that the Earth is 149597870700 meters away from the sun, but this distance is the average distance, and the Earth could be closer and farther from this distance, depending on its position during its orbit around the sun.

Planet Earth revolves around the sun in an elliptical orbit, and it takes 365.25 days to revolve around the sun in a complete cycle, and this period is known as the Earth year.

When the Earth is at its closest point to the sun, scientists call this point “perihelion” and that is in early January, when the Earth is far from the sun an estimated distance of 91 million miles (equivalent to 146 million kilometers).

When the earth is at its farthest point from the sun, scientists call this point “apogee” in early July, when the distance between the earth and the sun is estimated at about 94.5 million miles (equivalent to 152 million kilometers).

 

How was the distance between the earth and the sun calculated?

The first person who tried to measure the distance between the earth and the sun was the Greek astronomer Aristarchus, in the year 250 B.C. The measurement process at that time was completely inaccurate, and the scientist used a comparison between the sizes of the moon and the sun to estimate the distance.

The Greek scientist estimated the distance between the earth and the sun as equivalent to 19 times the distance between the earth and the moon, believing that the sun is only 19 times larger than the moon, but in fact it is 400 times larger than the moon.

Despite the imprecision of Aristarchus’ measurements, this scientist was able to understand the relationship between the three celestial bodies, namely the Earth, the Moon and the Sun, and was able to conclude at that time that the planet Earth revolves around the sun, and that is 1,700 years before the scientist Nicolaus Copernicus, who proved that The sun is at the center of the solar system.

In 1653, the astronomer Christian Huygens tried to measure the distance between the Earth and the sun, and he used the phases of Venus to determine the angles of a triangle whose vertices lie at the planet Earth, the sun and Venus. The Earth, Venus, and the Sun form a right-angled triangle when viewed from the planet, and through the theories of the right triangle, the distance between the Earth and the Sun can be calculated.

But Huygens’ measurements were not 100% accurate, because he did not even know how far apart the planet Earth and Venus was, and the distance separating Venus from the sun.

In 1672, the astronomer Giovanni Cassini used geometric theories to calculate the distance between the Earth and the Sun, and used astronomical observatories in French Guiana and Paris to make these measurements.

Because Giovanni Cassini used scientific theories and was able to calculate the distance between the earth and the sun with a lower margin of error than other scientists, he is credited with determining the distance between the earth and the sun.

The benefit of knowing the distance between the Earth after the sun

Before calculating the distance between the earth and the sun, scientists had difficulty estimating the distances between the celestial bodies and their distances from each other because the astronomical units used were small. But measuring the distance between the earth and the sun led to the emergence of a new one in astronomy, the astronomical unit, and it is now used to measure the distances between objects in the solar system.

In addition, the distance between Earth and the Sun plays a role in astrobiology, which is the science that investigates the possibility of other life in another place in the universe than Earth. The astronomical unit is useful for determining the locations of potential living organisms in it. Scientists search for planets orbiting stars at approximately the same distance, because this distance means the presence of moderate temperature and liquid water on the surface of that planet.

Modern techniques in measuring the distance between the earth and the sun

With the development of astronomy and the emergence of spacecraft, satellites and radars, scientists were able to measure the distance between the Earth and the Sun with great accuracy.

In August 2012, the International Astronomical Union changed the definition of the astronomical unit by adopting the number 149597870700 meters, this number represents the distance between the earth and the sun based on the speed of light and not on the mass of the sun as it was in the past, and because the speed of light is constant and the mass of the sun is variable, the measurements were That depends on the speed of light much more accurate.

Source

https://www.space.com/17081-how-far-is-earth-from-the-sun.html

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