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# Using Python to create a solar system

If anyone is looking for a fun exercise to flex their fingers…

Using just gravitational attraction between bodies, you can create your own 2D solar system with as many stars and planets as you want. Here's a binary star system with some relatively stable planets

Here's the article, including a detailed step-by-step tutorial, if you want to read more: **[Simulating Orbiting Planets in a Solar System Using Python](thepythoncodingbook.com/2021/0)**

…and there's also a 3D version _(next post)_

Addendum (some sad news): Since taking those pictures for the article, that sole remaining espresso cup has suffered this fate

I was told I can't say Rest In Pieces

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You press the "On" button—this is equivalent to calling the function.

You can almost see the similarity between the typical "On" button and the parentheses ( ) used to call a function in Python!

3/

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As it's time for my morning coffee (the coffee not the biscuits), it's as good a time as any to share my one of my favourite analogies

_(narrated from a -viewpoint but general enough for in general)_

**The Coffee Machine - Function analogy**

Let's make some coffee…

_[read on]_

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is for serious stuff, sure, but one of the most fun modules is the `turtle` module, but…

I know, I can hear you say: "That's just for drawing simple, boring drawings, right"

Think again! Here's a great learning project that is not merely a "boring set of squares!"

You can follow the detailed step-by-step tutorial here [WARNING: game is addictive and may adversely affect your productivity!]

thepythoncodingbook.com/2022/0

And therefore, you can reconstruct the image by adding all of those sinusoidal gratings together.

The more gratings you add, the closer the result is to the actual image

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Now, here's the "magical" part of theory.

*Any* image is made up of lots of sinusoidal gratings. So, the 2D Fourier Transform of an image gives you thousands of pairs of dots, and each pair represent a sinusoidal grating.

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Now, if you have lots of gratings superimposed on each other, the gives you a pair of dots for each of the components

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You can find the parameters of a sinusoidal grating by using the 2D .

The dots shown contain the amplitude and phase of the grating. Their position from the centre gives the frequency, and their orientation represents the orientation of the grating.

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Or even better, you can use a function of both x and y to make any grating

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There's one more parameter that defines a sinusoidal grating: the phase. Gratings with a different phase are shifted with respect to each other…

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…and different frequencies—these are spatial frequencies, not temporal ones

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It’s called a sinusoidal grating because the grayscale values vary according to the sine function.

If you plot the values along a horizontal line of the grating, you’ll get a plot of a sine function

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**Any** image can be reconstructed from a series of sinusoidal gratings.

A sinusoidal grating looks like this…

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What's an image made of?

There are many correct answers.

But the most fascinating one is: << sines & cosines >>

Read on if you're intrigued👇🧵🪡

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