A scientific article titled "Geophysical Definition of Planets" argues that the definition of a planet needs revision. The bold report states that the Moon, Pluto, and some other celestial bodies in the solar system must update their status to planets.
The research team included Alan Stern, best known for leading NASA's New Horizons mission. Scientists say that the geophysics of a space object should determine whether it is a planet or not, and not just the fact that the body revolves around the sun. We used to think that the Moon is a satellite of the Earth. So the idea that it could be a planet is really shocking.
Ancient Greek and medieval astronomers actually believed that the Moon was a planet. Ancient observers knew that the stars retain their relative positions night after night: they saw constellations, such as the constellation Leo or Gemini, just as we see them. And the astronomers of antiquity observed how the seven celestial bodies slowly changed their positions, wandering from west to east across the sky. The most important of these was the Sun. The twelve signs of the zodiac through which it passed formed a circle, which astronomers called the ecliptic. The sun (according to ancient scientists) passed this circle in one year, Saturn in 30 years, Jupiter in 12 years, Mars in 2 years. The Moon planet did this in 1/12 of the year - one month. The word planet itself comes from the Greek πλανήτης, which means "wanderer."
una has always been of particular interest to scientists. Her proximity made her the only "planet" with visible features - "a man on the moon." Aristotle (384-322 BC) asked questions about the physical nature of the moon - why do we always see the same "face" and never see its reverse side? Astronomers now explain that this is the result of the action of gravitational forces between planets and large moons and call it tidal capture. Aristotle came to a different conclusion. He decided that this proves the moon's lack of natural ability to rotate or move. The scientist suggested that this rule applies to all planets, and that they all move only in a circle.
did our ancestors have a good reason to include the moon in the list of other planets? Probably yes, but mostly due to a strange astronomical coincidence. Almost all large moons orbit in the equatorial plane of their planet or very close to it, but our moon does not. It is tilted 28 degrees. However, the equatorial plane of the Earth is tilted relative to the ecliptic by 23.5 degrees. Due to the combination of these two unusual factors, the Moon appears to be moving in the plane of the ecliptic - and no more than 5 degrees above or below it.
The figure of celestial bodies - illustration of the geocentric system of the world by the Portuguese cartographer Bartolomeu Velho in 1568.
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When Copernicus published the heliocentric theory of the world in 1543, the moon was no longer a planet. She became the "satelles" of the Earth, which means "servant."
The dispute over whether the Moon is a planet or not was renewed by Alan Stern. According to his report, "geophysical definition is more useful for practicing geophysicists, teachers and students." Or, as the scientist said very directly in 2015: "Why would you listen to astronomers about the planet, and not planetologists who know something about this topic?"
By the way, the debate continues about Pluto, which in 2006 was "downgraded" to the status of a dwarf planet. The latest application to return Pluto to the planetary rank came from planetary scientist Philip Metzger of the University of Central Florida. He says the International Astronomical Union's definition of a planet is wrong.