Tag: jupiter

Posted in Science & Nature

The Closest Planet

Posted on by Jinavie

Which planet is closest to Earth? If we look at a typical model of the Solar System with each planet neatly lined up, we can see that Venus approaches Earth closer than any other planet. However, this is only one interpretation of the question.

Technically, Venus is the planet that comes closest to Earth. However, as they do not orbit in synchrony, this approximation happens about once a year. At other times, Venus will orbit away from Earth and can go on the other side of the Sun, making the distance between Earth and Venus vast. In those times, Mars may seem like the next obvious choice to be closest to Earth.

But then again, Mars has the same issue where it and Earth are often on opposite sides of the Sun. Because of the nature of circular orbits, the distances between the planets swing and fluctuate, meaning that the real question should be:

Which planet is closest to the Earth most of the time on average?

The answer to this question happens to be Mercury. If we look at a “top-down” model of the Solar System, we can see that Mercury – being closest to the Sun – orbits rapidly around the Sun and often lies between Earth and the two other planets, Venus and Mars. If we plot the distance between each of these three planets and Earth, we can see that on average, Mercury is closer to Earth because the distance fluctuates less.

Interestingly, if we take this question further, we find that Mercury is also Mars and Venus’ closest neighbour on average. This is a property of the Solar System being formed of concentric circles, meaning that Mercury’s smallest orbit makes it average a closer distance to all of these planets.

Fascinatingly, if we go even further than that, we find that the same pattern holds for every other planet in the Solar System, despite the vast distance between Mars and Jupiter due to the Asteroid Belt. Even Pluto (not formally a planet anymore) with its massive elliptical orbit has Mercury as its closest neighbour on average compared to the other planets, due to the unique property of concentric circles.

No matter the distance, if you are orbiting the Sun, Mercury is the closest planet to you.

This video from CGP Grey explains it in a concise and informative way, complete with clean diagrams and animations!
Posted in History & Literature

Week

Posted on by Jinavie

In Genesis from the Old Testament of the Bible, it is said that God created the world in six days and rested on the seventh. But the system of a seven-day week can be found in many other cultures and religions. The origin of the seven-day week system is ancient Babylonia. The Babylonians believed that every seventh day was one of misfortune, with 7 having the significance that it is the largest single-digit prime number and the number of heavenly bodies known at the time (sun, moon, five planets). This was passed on to the Jewish people who made the seventh day the Sabbath. This was then adopted by Catholics in Rome and in 325AD, it was officially decided at the Concilium Nicaenum (official council that was held to vote for the official religion of Rome) that every week would be seven days long.

There is also a reason for assigning a heavenly body to each day (Monday = Moon, Tuesday = Mars, Wednesday = Mercury, Thursday = Jupiter, Friday = Venus, Saturday = Saturn, Sunday = Sun). At first, the order of the days was the same as the order of heavenly bodies by their distance from the Earth: “Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon”. This was then cross-referenced with the astrological 24-hour system of planetary hours, resulting in a new order of “Saturn, Sun, Moon, Mars, Mercury, Jupiter, Venus”. Because of this, the week started on Saturday in ancient times. It was only during Roman times when the week was changed to start on the Sunday, with Sunday becoming an official day of rest.

The Romans named the days after the heavenly body assigned to that day. For example, “Sunday” obviously comes from “Sun”, with the same applying to Monday and Saturday. This system is used in Korea and China, where each day is labelled according to the assigned planet. For example, Thursday is 목요일(mok yo il) in Korean, where 목 means wood, with 목성(mok sung) meaning Jupiter.

In English, the names of each day are mixed. Some are based on planets like the Korean system (Saturday, Sunday, Monday), while others inherit their name from the Germanic people. The Germanic people assigned one of their gods (from Norse mythology) to each day (except Sunday and Monday, which are related to the Sun and the Moon, while Saturday had a completely different name). Tuesday stands for “Tyr’s day”, Wednesday stands for “Wodan’s(or Odin’s) day”, Thursday stands for “Thor’s day” and Friday stands for “Frigg’s day”.

Interestingly, the Norse god assigned to each day correlates with the Greek/Roman god assigned to it. For example, Thursday is “Thor’s day” and also “the day of Jupiter”. Jupiter is the Roman king of gods (same as Zeus from Greek mythology) who uses lightning, while Thor is the Norse god of thunder.

Not every country calls each day a meaningful name. In China, Monday is simply 星期一(xing qi yi), or “first star period”, with each day after that being one number higher (Sunday is specially called 星期日(xing qi ri), where the number is replaced by the character for “Sun”). Although China used the same system as Korea and Japan based on 음양오행설(eum yang oh hang sul, system of Five Elements and Yin Yang), the days were renamed with the simplification of the language.