Distance from earth to sun
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Mean Distance from Earth to Sun: Astronomical Unit (AU)
The average distance from the Earth to the Sun is about 149.6 million kilometers (1.496 × 10¹¹ meters), a value known as one Astronomical Unit (AU) 1345. This unit is widely used in astronomy to measure distances within our solar system 134.
Variability: Perihelion and Aphelion Distances
The Earth's orbit around the Sun is not a perfect circle, so the distance changes throughout the year. At its closest point, called perihelion (around early January), Earth is about 147.1 million kilometers from the Sun. At its farthest point, called aphelion (around early July), the distance increases to about 152.1 million kilometers 8. This variation is due to the elliptical shape of Earth's orbit.
Historical and Measurement Methods
Historically, ancient civilizations estimated the Sun’s distance using various models, with early Indian and Greek theories suggesting much smaller values, such as 500 Earth diameters 2. Over time, more accurate methods were developed, including parallax measurements and observations involving the Moon 10. Modern techniques use radio telescopes and astronomical observations to refine the value of the AU 69.
Practical Measurement Techniques
Several practical methods exist for measuring the Earth-Sun distance, such as the shadow method and pinhole methods. These approaches are accessible for educational purposes and can provide reasonably accurate estimates, though professional astronomical techniques yield the most precise results 7.
Conclusion
The mean distance from Earth to the Sun is about 149.6 million kilometers, defined as one Astronomical Unit. This distance varies slightly throughout the year due to Earth's elliptical orbit, ranging from about 147.1 million km at perihelion to 152.1 million km at aphelion. Over centuries, measurement techniques have evolved from ancient estimates to highly accurate modern methods, making the AU a fundamental unit in astronomy 13458.
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