Tuesday 25 June 2024

Wonder-filled Solar System – Part IV


Wonders in Venus

Venus, the second planet from the Sun, is no less mysterious. Structurally, Venus has a lot in common with Earth. The size, mass, and density of both Venus and Earth are quite similar. However, when it comes to their environments, Earth and Venus are completely different. Earth's temperature is suitable for habitation, while Venus's temperature is 460 degree Celsius. Venus is filled with toxic carbon dioxide and liquid sulfuric acid. Its surface pressure is 90 times that of Earth. Venus is 108 million kilometres away from the Sun, while Earth is 150 million kilometres away. What could have happened within just 42 million kilometres? The main issue with Venus is its volcanoes. NASA's Magellan space probe has explored 98% of Venus's surface, revealing millions of active volcanoes. However, the mystery lies in the direction of its rotation.

Venus Spins Backwards

The planets orbit the Sun in a direction opposite to the movement of clock hands, that is, from west to east. Venus, like the other planets, orbits the Sun in this west to east direction. When planets spin on their own axes, they also generally rotate counter-clockwise, from west to east. Our Earth rotates in this way as well. However, Venus is an exception. Venus rotates on its axis in the same direction as the clock hands, which means it spins from east to west. Among the planets, only Uranus, like Venus, also rotates from east to west on its axis.


Scientists are still not unanimous about why Venus rotates in the opposite direction to other planets. They have proposed three different theories. Scientists believe that Venus, like the other planets, initially started spinning from west to east after its formation. However, for some unknown reason, the planet flipped 180 degrees, turning its top side down and bottom side up, resulting in the reverse rotation direction. Many scientists think this flipping might have been caused by Venus's internal geological processes or the intense pressure of its atmosphere. Others believe it could have been due to a significant impact from a large asteroid.

French astronomers Alexandre Correia and Jacques Laskar demonstrated through computer simulations that Venus's orbital direction and axial rotation direction were initially the same. At that time, the curvature along Venus's equatorial line was very pronounced. Venus was spinning rapidly on its axis then. However, due to the curvature and the intensity of Venus's atmosphere, its rotational speed gradually decreased until it eventually began rotating in the opposite direction.


On Venus, the Sun Rises in the West

On Venus, the events of sunrise and sunset occur in the opposite direction compared to Earth. Venus rotates on its axis from east to west. If someone were standing on Venus watching the Sun, it would appear to move slowly from the west to the east. Therefore, it can be said that on Venus, the Sun rises in the west and sets in the east. However, unlike Earth, where the Sun rises and sets every 24 hours, on Venus, it takes 243 days for the Sun to rise again after one sunrise. This is because: A Day on Venus is Longer than a Year.


On Earth, we measure a year by the number of days it takes for Earth to orbit the Sun once. Similarly, a year on Venus is the number of days it takes for Venus to complete one orbit around the Sun. Venus takes 225 days to orbit the Sun once (in Earth days, where 1 day = 24 hours). Thus, one year on Venus is 225 days.

We measure a day by the time it takes for our planet to rotate once on its axis. Earth rotates on its axis once every 24 hours, so one day on Earth is 24 hours long. For Venus, it takes 243 Earth days to complete one rotation on its axis. Therefore, one day on Venus equals 243 Earth days. This means a day on Venus is longer than a year on Venus.

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