If I look into the sky and I see two yellow dots it’s all stars for me. Then I hear one of them is mars and I’m like „ok, still looks the same“. How did the people hundred of years ago discover what’s a close planet and what’s a far away star?
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Because planets move. That’s literally what “planet” means: “wanderer.” If you sat and watched, you’d noticed that some of those dots move perceptibly across the sky while others remain fixed.
Stars are very far away, to someone on Earth they move as one across the sky like dots on a dome being rotated overhead.
Planets are much closer, they moved in a direction that was different from the stars and could be seen over time doing so. They even at times appear to go “backwards” against the motion of the stars.
“Planet” is itself derived from a Greek word for “wanderer”; this included the moon and sun as well as the visible planets since they also did not move with the stars.
In the early days of history, humans spent much time looking at the stars. The skies were clear and there wasn’t much else to do at night. They memorized the locations and when drawing was invented, they drew pictures of them. Sometimes they would notice that one light in the sky slowly moved. Then they would notice the light was different, steadier than then non moving twinkling lights. They were named for the gods.
Eventually in the 1600s people invented telescopes to see better and better. And we learned these were balls of rock and gas. Now we have infra red images taken from space and robot ships doing flybys.
Planet means wanderer.
After people discovered that position of the moon is corelated with hightides and sun brightness more or less indecated season they started to lookat stars and note position of them and found some of them moves.
Thus they found furst planets:
Moon, Sun, Mercury, Venus, Mars, Saturn, Jupiter (in that order)
Until late 16 century no other planets were discovered.
Also discovery of each planet leaded to immense impact on culture and technology.
2 most significant to make thing short:
Jupiter year is equal to 12 Earth years. Thus ancient people got calendar and ability to track seasons. From thet point agreculture turned from random event to technology allowing rise of countries as problems with food became less severe.
Mars is most reddest and biggest (every few ears) on the end of october, when storrages are full of provussion and supplies prepared for winter. Best time for some pillage.
It also is very big but not so red on start if march. Time when all food is mostly consumed, but now storages are full of different crafts which were made during winter. Also wery good time for pillage
Thus in almost every culture which discovered astrology Mars is associated with god of war.
The motion of a planet in the sky is very different from that of stars. This will not be obvious by just viewing one night unfortunately. By tracking the motion of the brightest dots in the sky over a period, it becomes clear that certain objects (planets) move very differently than the others (stars).
The telescope was discovered (at least in the western world) in the 1600s. With even a simple telescope it is pretty clear that these objects are not stars.
When you look up at the night sky, you give it a casual glance at best, and you look for a few moments and then go back inside or walk somewhere else.
Hundreds of years ago, they stared at stars for hours and noticed which ones twinkled differently and moved around over the course of days/weeks/months. You and I don’t notice that because we’re just not looking for it.
Mars could be seen with the naked eye, but the invention of telescopes really pushed the field forward.
Telescopes required (at the time) complex glass production. As a result planetary discovery heavily relied on a large established glass industry that could make the types of specialized curved lenses the teslescopes required. This limited astronomy to some parts of the world only. Chemistry entirely relied on glass as well and also ended up a geographically limited scientific field, but that’s a different topic.
Planets not only move differently than stars, but they more or less move in the same plane as the sun and the moon
The planets are extremely bright. Of the five known to the ancients, all of them except Saturn can appear brighter than any star other than the sun. If you’re regularly outside at night they’re all very conspicuous.
It’s a little hard to stay in ELI5 territory. But as far as they know,1800 BC the Babylonians were already maintaining daily, monthly, and yearly records of the perceived motion of the sun and moon, and other celestial bodies. Pythagoras of Greece, born around 570 BC,mathematically determined the world was round, and realized so were most other celestial bodies. Eratosthenes of Greece (sp?) used math to calculate the circumference of Earth, the tilt of the axis, and even thought up leap days. He was born around 276 BC. Aryabhata of India,born maybe 476 AD, figured out eclipses, figured out the moon reflected the light of the sun, the value of pi to four places, all kinds of mathematics that I need ELI5. Mayan calendar, Egyptian calendar very like the one we use now; look up Nabta Playa, it’s really cool! (A lot of what I’m typing involves a battle with the bloody auto correct!!) Gan De, Chinese astronomer about four centuries before Christ, created the Star Catalogue of Sho. Persian astronomer Abd al-Rahman al-Sufi born 903 AD, discovered the Andromeda galaxy. Abu Mahmud Hamid ibn al-Kidhr al-Khojandi built an enormous mural sextant and figured out the axial tilt so well he even noted that it was decreasing. Look up those mural sextants, they’re slightly mind-boggling. (edited for typos and disappearing spaces between words.)
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