Monthly Archive: November 2017

Educational GIFs

I'm slowly preparing a new post for the category "Physics for everyone". The post will describe the Lorentz transformation a bit more in depth, and say something about the consequences of it being the correct description of reality. I prepared two GIFs for this purpose:

The transformation of the coordinate system by a rotation (click for an animation)

The transformation of a coordinate system by a Lorentz transformation (click for an animation)

A more detailed description of those GIFs will be a part of the new post in the category Physics for everyone :)

I published the code I used to generate them on GitHub: https://github.com/fizyk20/spacetime-graph/tree/blog-post

Events and space-time

The first entry in the series will be quite basic, but I think that some problems will nevertheless be quite interesting. We'll be talking about what is the space-time, events, and we will show where the theory of relativity comes from. So, let's go :)

The notion of space-time is briefly mentioned at school, but usually the profound consequences of combining space and time into a single entity aren't explained too much. To understand this, one must first go a bit deeper into the details of this idea.

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Hyperbolic functions - what sorcery is this?

If you are like me, your first contact with the hyperbolic functions was as "this strange, useless something on the calculator". There were just some weird buttons labeled "sinh" and "cosh". The school finally explained what "sin" and "cos" are, but there was no mention of those variants with the final "h". What is this about? The names suggest some similarity to the trigonometric functions, let's see what happens:

 \begin{array}{ll} \cos (1) = 0.54030230586 & \cosh (1) = 1.54308063482 \\ \cos (10) = -0.83907152907 & \cosh (10) = 11013.2329201 \end{array}

(You will get these results if you have the calculator set to radians - if you use degrees, then the cosine results will be different; it has no influence on the hyperbolic functions and we'll see later why that is.)

Right, these 11 thousand for cosh(10) look very similar to the trigonometric functions. This "h" apparently changes quite a bit, but what exactly...?

If you encountered complex numbers during your later education, you could stumble upon such definitions:

 \begin{array}{ll} \cos x = \frac{e^{ix} + e^{-ix}}{2} & \cosh x = \frac{e^x + e^{-x}}{2} \\ \sin x = \frac{e^{ix} - e^{-ix}}{2i} & \sinh x = \frac{e^x - e^{-x}}{2} \end{array}

Some similarity is visible here, but... Why such a form? What does this have to do with hyperbolas? If you don't know it yet, you will know after reading this article.

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Generic-array reached 100 000 downloads!

My project, generic-array (a Rust crate) has now been downloaded 100 000 (in words: one hundred thousand) times! This is my first project of such a popularity.

It began with a simple hack, working around a limitation of the language - and apparently this limitation bothered many people, because a few sent me pull requests (also a first for me), and a large number downloads the library. I actually have no idea what else to write, I'm just happy that people are finding it useful ;)