Looking Up, Then Looking Closer
Lecture 3: Charting the Paths of the Stars and Planets
(W) Today’s Mystery:
I love looking at the sky. There is just something about staring at the stars that makes me feel both uneasy and small. I remember when I was around 8 or 9, I learned that stars aren’t actually little star-shaped things and I was so devasted. They are basically huge, roughly spherical objects, and the “star” shape we draw is just how we represent them. My little mind couldn’t comprehend that. I felt like I was lied to. And ofcourse, we can’t forget that childhood experience of thinking the moon is following us. So now, our mystery is:
“How do all the dots up there actually move?”
(K) What I Know:
Before this lecture, I mostly knew that planets orbit the Sun and that gravity has something to do with keeping them there. I also knew about the whole Copernicus situation, I just didn’t know It was called like that. It was just taught at elementary that the Sun is at the center instead of Earth, but I never really thought about what came after that.
I guess I thought that once people figured out that the planets revolved around the Sun, the problem was basically solved. Turns out… nope. There was still a whole lot of “actually🤓☝️” left.
(L) Let’s Explore!
The first person who really caught my attention was Tycho Bryche. He made observations of the sky before telescopes were even available. He proposed a hybrid explanation, that… the Sun and Moon revolved around the stationary Earth. That’s kind of wrong, but I’m still jealous that he has all that time to observe the night sky and intelligence to make explanations. Imagine having to spend that much time just watching and recording the movements of planets with your own eyes and instruments. His observations became extremely important because Johannes Kepler later used them to figure out how planets “actually” move.
So, let’s move on to Kepler.
Nicolaus Copernicus had placed the Sun at the center, but he still believed that planets moved in perfect circles. Kepler went ahead and discovered that… they actually don’t. The planets actually travel in elliptical paths. Johannes Kepler even have his three laws that made planetary motion much more understandable. The first tells us about ellipses (Law of Ellipses), the second tells us that planets change speed as they orbit (Law of Equal Areas), and the third shows that there is a mathematical relationship between how far a planet is from the Sun and how long it takes to complete an orbit (Law of Harmonies).
You can also read this: Orbits and Kepler’s Laws
What I found interesting is that Kepler wasn’t just making random observations. He was looking for a pattern in the data. He took what Tycho had carefully observed and used mathematics to figure out what the planets were actually doing.
And then Newton bursts through the room and basically connected everything like the great man that he is.
Kepler could describe how the planets moved, but Newton wanted to explain why. He realized that if planets were constantly changing direction instead of simply moving in straight lines, then some force had to be acting on them. That force was gravity.
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The part that really stuck with me was the idea that the force keeping the Moon in orbit around Earth is the same force that makes an apple fall to the ground.
Like… an apple falling and the Moon orbiting Earth sound completely unrelated when you look at them normally, but Newton showed that they are both explained by the same law. That is honestly one of the coolest things about physics to me.
It also made the idea of physics being universal feel much more real. The laws aren’t different just because something is happening in space instead of here on Earth. The same physics applies.
(L) Did You Know?
- Kepler’s work helped establish the mathematical description of planetary motion.
- Newton connected Kepler’s observations and laws to his theory of universal gravitation.
- The idea that the same laws govern both Earth and the heavens was a huge shift in how people understood the universe.
(L) Real-Life Connection:
What I found really interesting is how this whole story shows that science doesn’t just suddenly arrive at the correct answer. So I won’t make up some random scenario just to call it a “real-life connection.” Instead, I will explain what this actually made me realize and connect it to lecture 1.
It was more like one person figured something out, but there were still problems with it. Then another person came along, found the problem, and improved the explanation. Tycho gave Kepler better observations. Kepler found the mathematical patterns. Newton then used those patterns to explain the force behind them.
It reminded me that being wrong isn’t necessarily the end of the world. Sometimes, it’s literally what gives the next person something to investigate with. Which, in fact, is part of the sense of lecture 1. That science isn’t a path from ignorance to knowledge. It’s cyclical.
Someone observes something, explains it, someone else finds something that doesn’t quite fit, and that leads to another question. Then someone investigates that question, and the cycle continues. Seeing the progression from Tycho to Kepler to Newton made that idea from Lecture 1 feel much more real to me. And this connection seems more real than any real-life scenarios I can make up.
(S) Pursuit of the yet-to-know:
I want to understand more about how people actually made such precise observations of the planets before telescopes. Like, how were they able to track something moving so far away with enough accuracy for Kepler to eventually use the data? Because every star looks like same to me. Is that just me?
I also want to understand more about how Newton actually connected Kepler’s laws to the equation for gravity. I know the basic idea now, but I feel like there is still a whole lot of “huh? paano?” waiting for me there.
(F) How am I feeling this week?:
This lecture made me feel, normal. I didn’t have any special feelings for this week. Though, the sky felt a little different to me. I already liked looking at stars, but now I’m thinking about the fact that everything I’m looking at has its own path, like I do.
It also made me appreciate how much work went into understanding something that we can now explain with a few equations. Looking up at the sky as a kid, I was just seeing pretty little lights. Now I’m starting to see a whole system. That’s appreciatable.
