Blue eyes: logic puzzle

about one or two weeks back, while scrolling through XKCD comics I have bumped into Blue Eyes logic puzzle, that Randall (the author of XKCD) heard in Boston from some random guy named Joel. Randall titles the puzzle as the “hardest logic puzzle”. It was not the case for me so I would title it as “most interesting (and hard) logic puzzle”. Here is why:

I wont rewrite the setup for the puzzle, you can just read the original here.

So now you know what this is about… if you want to solve it yourself (it might take some time) stop reading.

Why I find this puzzle so interesting is that from the first view it does not make any sense, it shouldn’t be solvable. What the sear (the one with green eyes) says shouldn’t make any difference right? Because everybody knows that there is other person with blue eyes, they can see it, yet when everybody hears it, it makes a difference and in the induction that proves the solution, this information is totally crucial.

If you start with less people like one, then two and so on, it becomes way more obvious that what the sear says actually does make a difference.

It took me together about 2 hours to solve the puzzle and I think it is perfect example of something quite simple working in non-intuitive ways and how our brains still have hard time grasping it.



First experience with hammock


I want to share my experience with sleeping in a hammock for the first time.

So I got hammock for my birthday among other things. After finding some cords to tie it to trees I realized that it will be best to try sleeping in it. Since it is almost November and I happen to live in northern hemisphere, it can get close to 0 degrees (no, not Fahrenheit you dummy). Luckily there seems to be subreddit for anything, including hammocks (or also Flying Whales), one can get some tips there quite easily.

So the pluses after 2.5 nights where one was rainy are: it is extremely comfy, no need to watch out for boughs or stones on the ground, you just need trees. Hammock is very easy to pack and unpack saving ton of space. On the other hand your butt will get cold, I am considering under-quilt which is basically sleeping bag that wraps under the hammock. So far I found it also difficult to find the right trees to be also able to set up the roof but it might just take a little bit more experience to have the right estimate for the separation of the trees.




nobody expected it and yet it happened, nobody has foreseen it and yet it was inevitable, nobody cares and yet I am here once again!

After 5 months, three seasons of Rick and Morty, 2 weeks in CERN and bunch of other stuff, I have returned to strike back with an epic post full of me talking about how I came back while wishing I will write another post after this one.

Now I feel a bit stupid, I have this work that I have to do this semester about GPS. It turned out to be quite complicated and one of the import theoretical facets of my work was to find out how GPS chips differ in various phones. I was googling and googling the phrase “gps chip in mobile” with the false assumption that there is a special chip like that. While gps chips do exist, they are a bit different thing than what I had in mind (costing lets say 150$ or whatever, ready to be implemented to something you build by yourself).

Apparently processors in phones take care of that, like the Snapdragon series, you can find all of the info here.

Everything on one page and I am complete… my final work is not though. It will still require huge time investment and sleepless nights!


What does “x” and “y” even mean?

so after quite a break, I am returning with math post. It is going to be simple analytical geometry or whatever this field is called.

After teaching some people about lines, circles, circles in a hydraulic press (read: ellipse) also vectors and all sorts of shapes that you can think of[1] I bumped into a fundamental issue that my “students” missed out something important even after using it (without knowing what it really was) for a long time.

First, let’s talk points. A point on a number line is quite straightforward. Why? Because you do not need to have a lot of information to describe it. Image result for number line

Any point on the number line can be represented using only one number, one value. If you wanted to represent a line on the number line you would just need to set boundaries for the highest and lowest number, something like 3<x<5 [2]. This line would have the length of 2 and you would find it by just drawing all the numbers like 3,3.1,3.2,3.5,4,5 and all the others in between, those are all the possibilities for “x”.

Image result for grid line

Number lines start to get boring on this level so we have to step up on a grid. Here you need more information. As you can see on the map. Your city/town has two coordinates, latitude and longitude which is just a fancy name for the commonly used “x” and “y”. Here the grid is limited for x which needs to be between +180 and -180 and y between +90 and -90. With these two coordinates, you can locate any point on the Earth. The similar thing is with the commonly used grid but there, “x” and “y” do not have any boundaries[3]. But how do we write a line on the grid? Well, we could just ignore the fact that it is a grid and think about it as a number line. We just need to set “x” or “y” to some number and let it be fixed and unchanging while the other one changes and describes our infinite line (without boundaries) or just a segment (with boundaries). If “y” is constant that means that we can move only left and right and the line will be leveled. If “x” is constant we can only move and find the points on the line by moving up and down and the line will be vertical.

I will continue probably next time with lines that go different directions.


[1] Don’t think of too random shapes, they would be too difficult, you still have to think about “nice” shapes.

[2] Any math is really difficult to write in WordPress so what I actually meant was 3<=x<=5 which means that numbers 3 and 5 are also a possibility.

[3] Of course, Earth is a sphere and that is different geometry but it serves as a good example.

Is consciousness an illusion?

so apparently we have a problem. Noone knows where consciousness comes from. This is quite a big question since that is what we are, right (?) the mind.

I find this idea of consciousness very interesting, we cannot share what being mindful feels like or see that another creature is aware. We have to take it for granted from what others tell, there is no way you can tell that your friend is not just a machine, that is what I mean.

As the title suggests, I will be asking myself if consciousness is just an illusion. This might seem a bit outrageous which makes sense and I am totally open to it being wrong (which it very easily might be, see disclaimer). I think that awareness will raise as an illusion if there is enough complexity added to the system. By the system I mean of course what we perceive through our senses but also the thoughts. The thoughts might actually be the most important part, making our personality.

I am suggesting that with language and thoughts we create a fake personality, the ego which then creates a sense of existence. Through the sheer amount of information that the body receives and reacts to, arises this illusion.

Have you ever tried to notice how thoughts appear? They do so without somebody telling them anything or controlling them [1], this is why there is no one behind them but a shadow. The thoughts tell themselves that they are real but they are just a reaction to the surroundings. That is why there is no special part of the brain that cares for consciousness, it is just an emergent property of huge complexity and in the end, we truly are only robots.


Disclaimer: I’m not neurologist or expert on this topic, those are just my thoughts on this problem.

[1] If you think there is, think again, because those are just other thoughts.

Three year anniversary

apparently, the three year anniversary was already yesterday though I thought that my first post became public on 21.3.2015, I guess I was living in a lie.

What now? I have been very lazy in the past weeks, not posting a lot. I am still planning to continue to write the blog, I have no doubt, definitely.

In the three years I:

Received 2 510 likes
Wrote 126 430 words in a total of 318 posts. (Harry Potter and Prisoner of Azkaban has 107 253 words.)
From my readers, I got 1 250 comments.

This is a small blog, it always was and will be in the future, I am not even really reading anybody else’s posts or trying to get more views. I just let go and write a post about once a week if I feel like it. Whoever reads it, cool, I hope that the posts help or you find them interesting at least sometimes, every like or extra view makes me happy and you are helping with that.



today I will write a short post about the power of mnemonics.

Those are things that help you remember something. One that I used quite a long time ago was Saturn mnemonic. I was not sure if it was Jupiter or Saturn with rings but then I realized that the letter “S” is basically just circle disconnected and changed into the shape with a single movement. One could argue that this does help because “J” could work similarly and it is not foolproof but the beauty in this is that it does not need to make sense, it is enough if it helps you remember something.

Another example would be how in 8th grade at the end of the year we had to remember (in some game) two groups of words, the key to this is for me was visual mnemonic, I simply stacked the objects on top of one another. It went like this: ruler, place, hill, plant sock and the second group was a chandelier, scissors, and map (I do not remember the next two words). The first group was extremely simple because the hill would be kind of roundish in my head, so it would nicely fit on the plate, the plant would grow on top but would be hidden by a sock, does not make sense but did its job.

From my experience, it is best to be able to create your own mnemonics connected with your life. Often they are total nonsense, some kind of absurd story. For example, this is how I remembered what in your skin is responsible for that feeling:

Pacinian corpuscules – Pa like Pascal (not my invention but Pacific as a pressure in the deep ocean would work too)
Kraus corpuscules – From Vampire Diaries, Kraus was quite a cold person (corpuscules responsible for cold)
Ruffini corpuscules – ff like fortissimo in music, fast means hot so corpuscules for heat

Sadly enough I forgot to make one for Meissner corpuscules so I didn’t do that in a test.

Now you should have the idea, I recommend the following tests to try this out or just to test your memory:


Cellular automatons

today I will write about a new thing that I just learned over the weekend. Since it is based on a competition again I will care not to post here too much so as to be fair and not to spoil it.

Cellular automatons, at least in my knowledge so far, are in a sense, computer colonies, comprising of tons of cells. In the simplest version, you have 1-dimensional automatons which means that the cells, signified by squares let’s say, are in one row, every one of them neighboring with two other.

The cell is either dead or alive. You can create rules to make them reproduce and die, when, let’s say some cell is overcrowded. If you decide that what will happen with the cell depends on the state of the cell itself and the two neighbors and the result will always be the central cell either dead or alive there are 256 options for different rules.

This is how it would look like if the rule would be that cell always reproduces to the rest of the fields that it neighbors with but dies if the two spots around are full [1]:



Not here, but it had 5000×5000 pixels. Feel free to use this picture for anything.


This is one of the interesting most of the 256 rules ain’t doin’ a thing but this is the rule #126 so remember that 😉


[1] The picture is not a line because every line of pixels is one second let’s say during which cells reproduce and die and so on, yellow means alive, purple means dead and in the beginning (top of the picture) you have only one alive.

How societies keep their members from leaving

today I will write about societies and generally some at least partially closed groups of people that even if they seem different from each other, they share one ultimate tactic to survive.

I will start with the most common and intuitive example which is, of course, a dictatorship. For a dictator to be in reign for a long time he needs the people of the state (no ruler rules alone). Of course, they can’t be just free to leave so dictator has some simple means to keep them. Let’s say fence, it is quite effective against most folk. Also violence in general, there is this threat, if you try to leave the society you will get punished. This is simple but not perfect, there is a better way to do this and for example, democracy found that out.

I am not saying if this is good or bad, that is not the point here, what I want to illustrate is that democracy needs its people too and like in a natural selection only the strongest regimes will last [0]. Western states no longer need a brute force to keep their members from leaving because most people are from young age taught how where they live is the best [1.5], yes we have bias towards democracy, teachers in schools have bias towards democracy and there is no need to have a brute force because your family, your friends and simply your surroundings will pull you back in case you start to diverge paths with what you have been taught. Do I find this concerning? No, not really (a bit) because I am PART of the system! Which of course means that the system is doing exactly what it should do.

Those are not the only examples. Religion too, whether you like it or not. You will be looked down upon by your fellow believers if you start to question the society. The pressure on you, once again (in Western society at least), won’t be physical, rather psychical. For the system to survive it must teach it’s members that it is the best one and that it is wrong to question it, after that, it is just a cycle.

School is another example. You are forced to stay in it by everybody around you (of course we are not discussing the consequences of leaving school [1]). There are other countless examples and always the pull on oneself is stronger when more people around you are in a group that you want to leave, like let’s say if everybody in your family is religious.

Just food for thought, feel free to leave comments and proof me wrong!


[0] Here I am not comparing dictatorship and democracy as to which is stronger (because they both exist), rather democracy to anything you can think of that never really existed (anarchism maybe?).

[1.5] Dictator can also brainwash (a bit too strong word [1]) their people but I was thinking of let’s say communism in Czechoslovakia where my parents certainly did not think anything good about the regime.

[1] For exactly the sentence that I wrote, is this topic so nuanced. I think I should not leave school because it will worsen my life, everybody taught me to believe that, it is apparent that it might be hard for me to earn money but maybe I would be happier, who knows, but I  know I am not planning to try it.

Disclaimer: I am not an expert in whatever field this is.


Unrealistic radioactive decay

today I am going to write about one of the problems that I had to solve for a physics seminar. The submissions for this series are already closed and you can look up the solutions so I know that I answered correctly to this very interesting problem.

Imagine you have two types of particles, A and B. They are radioactive, meaning they keep falling apart but in a very peculiar way, A decays into B and B decays into A. This doesn’t happen in a real world because the particles decay into something smaller, they break up, but this is a hypothetical scenario very simplified, we do not care about what is happening on the inside. The question is, what is the ratio of the particles at any point in time?

Since the answer itself and the calculation are not trivial I will mainly try to make some facts about this problem obvious and then show the answer.

There is one part that I didn’t mention in the setup. Radioactive particles do decay but there is a very important value that characterizes how fast. It is either (half-life) which tells you in what time will half of particles decay (if there is enough of them it will give the right results) or in other words when the time passes one particle has 50% chance to decay. It seems that also decay constant, which I like better, is used which is basically half-life except the larger the value is, the faster the particles will decay.

The problematic part of this exercise is that when part of the A particles decay they will increase the pile of B particles which means that more particles will decay into A and so on, this is a cycle. To get to an important point it is good to try some simple case of such decay.

Let’s say we have 200 of A particles and 100 of B and half of both will decay in 1 hour. In 1 hour:


Next hour:


It is obvious that from now on the amount won’t change. This little experiment revealed something obvious, there, first of all, no particles get lost, there is always the same amount present: A+B=constant and with a bit more experimenting it would become more apparent that there is an equilibrium between A and B meaning there is always some amount of A that when it decays it will equalize the amount that decayed from B, this equilibrium will shift depending on the length of half-life or the decay constant. From these thought experiments that reveal the behavior of this problem, we need to use some math that I will not get into here to get the result that you can try to play around with in Desmos.