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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People like exploring things. I don’t know all the history but let’s skip to the part where someone has a telescope for looking out into the coast waters and spotting possible enemy ships or trade ships. One day the moon is big and bright and that person goes “Well fuck let me look at this mf with this thing he’ll yeah brother” and even with a very weak telescope you can see tons of detail in the moon. Try it if you haven’t.
So at the same time people were also just looking at the stars and noticing that some of them were always in the same spot, some were just very so slightly moved a little bit, and other ones were moving a great deal just over the course of one night or a few days or a week. Some of them weren’t even visible anymore. Because of the Earth’s rotation or something fancy like that.
So now these people take their telescopes and keep looking up and they record what they see, these dots and patterns and how they move.
Then one nice clear night someone looks up and sees not a white dot but a ball. A ball with colors and…clouds? Rings? Surface features? What the fuck are these things? Planets. Fucking planets.
It’s also important to remember that back when these things were first being discovered, light polution was basically non-existent. You could see the bright bands of billions of stars of the Milky Way with your naked eyes. Today you have be in the absolute darkest parts of the world and as elevated as you can possibly be to see these things.
There was zero chance people didn’t notice these things in detail with their naked eyes, which is what prompted them to look closer using the tools that they developed for other things (telescopes).
Haha i love light pollution so much, im so glad to be born mid into the proliferation of massive light pollution
How they moved in the sky was ‘odd’. Occasionally they would appear to move the ‘wrong’ way.
Both the Earth and the planet are orbiting the Sun. So sometimes we would ‘catch up compared to the planet and other times we would appear to ‘fall back. So planets would appear to move one way for part of the year and then appear to move the ‘wrong’ way for other periods
Think of runners on a race track. One on the inside line going quite fast and one on the outside line, plodding along. Sometimes it seems that the direct distance between them is closing, but then other times they are moving apart
The name planets derives from a Greek word planḗtai, meaning wanderers. This was due to this odd looping behavior in the observed sky.
It boils down to curiosity. For an example of this, google Galileo Jupiter Moons.
In the early 1600s he persistently pointed his telescope at specific “stars” and noticed some of them moving. He noticed a pattern wherein some of them seemed to disappear and reappear on the other side, eventually hypothesising they were orbiting the larger one. Keep in mind this was before “the larger one” was known as Jupiter or even a planet.
To come to such conclusions when all you have is your mind and (relatively) crude tools, curiosity and genius.
Go work the night shift at an outdoor job. You will quickly notice that every star is not just a star. People spent much more time outside and in darkness in ancient times than we do, so they had plenty of opportunity to observe the differences in the night sky.
even with the naked eye, there is a noticeable difference between stars and planets: stars twinkle, planets don’t.
The clue is in the name. “Planet” means “wanderer”. Because that’s what planets do – they wander.
People used to be able to see the night sky much better than most of us can nowadays (courtesy of light polution). And some of them paid close attention, and got to know the sky well, not least because it’s massively useful knowledge – you can navigate by the stars. And if you watch the sky over days, weeks, months, years, you notice that some of the lights move about. Those are the planets. The actual (so-called “fixed”) stars don’t (or at least, not on any timescale that indivduals are able to experience).
If you go out every night, you will start to notice that the stars form fixed patterns. They don’t change positions relative to each other, they all move across the sky together.
Then one night you notice a new star. It’s a bit brighter then the rest too. Over the next few nights you notice something bizarre. The new star is moving relative to all the other stars! Suddenly, its much close to Orion than it is to Taurus. How can that be? Stars don’t move.
Rather poetically the name “planet” comes from the Greek word for “wander”. Plantes are, to the Greeks, literally stars that wander.
Planets move across the sky in the same plane as each other. If someone is paying attention night over night, they will see something moving across the sky with a rhythm. They make lenses capable of looking closer at these objects, and look! It’s different than the other ones. Could be something like the moon.
And then it took a while to figure out if the earth or the sun was the centre of rotation.
Short version? Some ancient nerds with lots of free time on their hands spent a LONG time looking at the sky and paying attention to the patterns.
Then they started making *notes* because they thought it was important, and then they noticed some of these moved really differently to the others.
To be fair to them, if you don’t know what you’re looking at, the magical sky lights that are probably something to do with the gods and move in strange ways MIGHT be something you consider important enough to make notes in.
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