How do bearings lower friction?

The first time I really encountered object with bearings and was wondering about what they really are was about 3 years back when I was on inline skates with a classmate. There was a nice long and smooth downhill and we both drove down without much beforehand added speed. Soon he was going way faster and was still moving many seconds after me. At that point when we started to talk about it, I thought than my inline skates do not have any ball bearings, which I now think is not true, he only had clean ones since his skates were new. Probably without bearings the skates would not work.

Ball bearing. See how they do not slide, they rotate.

Ball bearings are small balls (often from metal) enclosed between two spaces that are supposed to rotate, for example on some axis. It is possible to just leave the two surfaces touching but then they just rub against each other which causes high friction. The important part is that the balls as you can see on the left, rotate, they do not slide and when circular object is only rotating instead of sliding it does not experience much of a resistance. Try it yourself. Take a pencil and toss it across table so that it does not start to turn (parallel with the direction of the movement). Remember the distance where it got and try the same thing but this time perpendicularly and see how far it gets, that is exactly what the bearings are doing.

There are lot of types made for different purposes. Since the bearings have much lower area with which they are touching they do not distribute pressure so well, also they might need cleaning often or lubrication. In fidget spinners you will of course find bearings. The ones that spin very long time are the ones with ceramic bearings.


SpaceX meets Moon (soon)

private space company SpaceX aka Elon Musk decided to visit make a flyby around Moon in 2018.

Where to start? Well it probably began with two private citizens who were willing to pay many MANY millions of dollars to get a nice trip. Yes, space tourism, exactly.

This trip is planned to be done with Falcon Heavy which is rocket (not build yet) designed by SpaceX and is supposed to have 2/3 of thrust of Saturn V (the rocket that got Apollo to Moon). The crew will stay for about 8 days in Dragov v2 (v standing for version) capsule that is also not tested yet. Both of these things are supposed to be run later this year.

Dragon V2 in hover test [1]

The crew are definitely some rich people but as of now they are staying anonymous. At the end of this year they are supposed to start some training but otherwise the mission will be automated so they wont have to do much stuff.. also that means that they wont do much science either.. only some tests on their bodies but otherwise it really is only “sightseeing” trip.

Why this whole thing though? Well it will add lot of publicity and earn some money and it is place to test Falcon Heavy and D2 capsule[2]. The last time people went to the Moon was in 1972 and this mission is quite similar to Apollo 8 which was also such a flyby.

Otherwise we do not really know much details, SpaceX will have to do a lot to be able to accomplish this goal and right now it is behind schedule.. there were some rocket explosions which slowed the company down. We will see how it looks like in the upcoming months.


[1]When the rocket starts to explode and there are people on board, you need to be able to escape really fast. The capsule was not tested on rocket yet.

[2]Also if part of it is payed by somebody else.. well why refuse?

Picture source: By SpaceX Photos – Dragon 2 hover test, CC0,

Pioneer Anomaly

today I will write about strange phenomena that occurd to Pioneer 10 and 11 spacecrafts.


Pionner – artist’s concept

Both of these missions are quite old in the space exploration sense. One launched in the year 1972 and the other 1973. They were made to explore outer part of Solar System (meaning still quite close) and after that they of course just went on.. there is no way to retrieve object so far and it would not make much sense.

We lost contact with both but before that we knew how far they were because of their signal. There was something wrong about it anyway, every year when we predicted where they would be they would lack behind about 400 kilometers. Thats almost the length of Czech Republic though Pioneer 10 is able to cover the distance in 33 seconds so that is not much of a difference. But… there is a lot known about the forces acting on the spacecrafts and those could not be it. For example gravity from Sun is slowing them down but it is a thing that one can account for quite easily.

It took few decades to solve this problem (paper finally explaining it was published in 2012). Now we know that it was because of radiation from the spacecrafts as it was losing heat. Pioneers were spin stabilised so that their antennas always pointed towards Earth. The way it was build scientists found out that the radiation causes acceleration towards Sun. But it is kind of weak only: (8.74±1.33)×10−10 m/s2

Thats now much but in Viking program if radiation pressure from Sun (which is a different thing of course) would be ignored it would miss Mars by 15000 kilometers which is quite important.


Pionner picture: By NASA –, Public Domain,

Jerks are even in physics

the title is a pun. There are probably jerks yes, but what I want to talk about is physical unit[1] called jerk, it is named like this because jerk not only means, idiot or stupid, but also to move suddenly, because of surprise.

It will be nice, if we first recall that derivation describes the rate of change of something. For example, speed is the first derivative of position because speed describes the rate of change of position, the higher the speed the more position changes!

{\boldsymbol {v}}=\lim _{{\Delta t}\to 0}{\frac {\Delta {\boldsymbol {x}}}{\Delta t}}={\frac {d{\boldsymbol {x}}}{d{\mathit {t}}}}.

1st derivation of position “compared” to time

In the picture above you can see how speed is defined compared to position (x) and time (t). It is its derivative as I said before. Now of course you can define something, that describes how velocity changes over time. That is called acceleration.

\mathbf {a} ={\frac {d\mathbf {v} }{dt}}={\frac {d^{2}\mathbf {x} }{dt^{2}}}

Again, “d” simply means derivation and when it is “squared” it means that you need to derive it twice. Acceleration describes, how velocity changes over time.

This is all you might need for daily life. Of course though, scientists defined next derivations, the change of acceleration in time is called jerk. The change of jerk is called jounce the change of jounce is crackle, next follows pop and then possibly lock, drop, shot and put. The SI units of all of these time, position related things are similar. With each derivation you add one to exponent of time.


and so on..

Just to remind you, if you have lets say “pop”, which is 6th derivation, of 10 m/s^6 you will have a tremendous speed extremely fast. From this next equation it should be pretty clear:

{\displaystyle {\vec {r}}={\vec {r}}_{0}+{\vec {v}}_{0}\,t+{\frac {1}{2}}{\vec {a}}_{0}\,t^{2}+{\frac {1}{6}}{\vec {\jmath }}_{0}\,t^{3}+{\frac {1}{24}}{\vec {s}}_{0}\,t^{4}+{\frac {1}{120}}{\vec {c}}_{0}\,t^{5}+{\frac {1}{720}}{\vec {p}}\,t^{6}}

The power of the higher derivations is that the exponent does extreme changes in a moment. r is the position, v speed, a acceleration… p is pop and t is time.

This is probably not used much, if at all, even in engineering.. but hey, fun!


[1]It is not a unit. It is physical quantity or something like that. I do not really know how it is called in english.

Is this a proper perpetuum mobile?

today I want to investigate one particular perpetuum mobile machine. First when I wanted to write this post I wanted to let it open ended since I did not know the solution for why it does not work but I have found it so here you go:

Physics is basically based on the fact that energy and mass are conserved. If you were able to put enough strong evidence against it, modern physics would basically collapse, this is the foundation.

Now perpetuum mobile is a machine that is trying to break this law, but not very succesfully since none was ever built. Perpetuum mobile is a machine that gives out more energy than it needs for running.

Performance is larger than power and effciency is larger than 100%. This is not possible though you can check your basic physics skills by debunking these machines.

One of the most common “perpetuum mobiles“. As it turns it is supposed to create torgue and rotate forever.

It has been while since I saw what is called “Brownian ratchet” and I was simply stucked. It is kind of different from other “perpetuum mobiles” since it uses what is called brownian motion to work.

Feynmann was one of the guys who popularised this machine and also showed it flaw.

In the box 1 you have small paddle wheel. Particles bump into it because of brownian motion, that is a motion of small particles that goes indifinetely (this is type of thermal fluctuation).

This paddle wheel can only turn in one direction because in the other box you have ratchet as you can see above. The paddle wheel turns one way lifting up something or simply doing work. Where is the problem?

I remember asking my teacher about this. She said that it would really be perpetuum mobile. I knew she is not a good one. Now I did not know but I was sure that there is some flaw in this and I found that there is but I did not find explanation.

Today I found wiki page about this “Brownian ratchet” and they basically say that if the pawl is the same temperature as the paddle it will also undergo the same brownian motion sometimes jumping up and down. The thing is that we can not forget that the thing is also extremely small. If it would be different temperature it would work but based on thermal difference which over time disappears.


Private companies take the space industry by attack

today I want to talk about how private companies like SpaceX ,which I already talked about few times and Blue Origin for example, influence the space industry.

For many years there was NASA and only NASA. Now these days you could have noticed that SpaceX appeared, self-funded company with priority of making space cheap. Same interest has also Blue Origin, space company founded by Jeff Bezos, the owner and CEO of Amazon. (billionare as well as Elon Musk of SpaceX)

These two guys and others are aiming for cheap space which is something that NASA was never able to do. After Apollo 11 they wanted to start to use reusable rockets but it never went to perfection. The primary goal of 25 dollars per pound on the orbit of Earth, changed more into something like 25,000 dollars per one pound.

Now NASA wants to make Space Launch System and Orion capsule to get us to Mars. Noble goal it is. There is one “minor” problem. Look at NASA budget over years:

The peak is when we were trying to get to Moon

Right now NASA has about 0.5% of federal budget compared to 4.5 that got us to Moon. Estimates are that the whole Space Launch System (SLS), which is basically huge rocket, will cost in the matters of tens of billions of dollars (this is just development, see later for launch price)! (0.5% is something like 19 billions of dollars).

The thing is that there are other players, like SpaceX who can do this much easily. SLS will be using boosters RS-25 that are from 70s and throw them away after every launch while we have New Shepard of the company Blue Origin that has already been used 5 times over!

From what I have read from Phil Plait and others, SLS will probably be one huge fail. Already now it is behind schedule for its first unmanned launch, not talking about the approximation of mission to Mars (something like 2030-40) where as SpaceX is investing huge amount of money to Falcon Heavy that should be able to carry over time enough stuff to build a base on Mars. Falcon H. payload capacity is over one third of SLS though it should be able to fly several times for the same price as SLS. (I found that it would be able to make more than 5 flights for the same price on the Low Earth Orbit, thats some difference!)

The thing is that NASA is underfunded and right now it even spends money on something that may not ever be working while there are smaller players but with clear and cheaper mission.

Mind you that SpaceX is planning to design Interplanetary Transport System and Blue Origin’s New Armstrong (they are working on New Glenn right now which is one of these huge rockets anyway).

From what I have understood, the key in the future of space exploration is reusability.


Check out these pages for more info: 1) 2) 3) 4) 5) 6)

Btw. NASA does not plan to use SLS more than 3 time per year because otherwise they would have to build up huge facilities. Also the first version of SLS will have payload capacity of almost half the one that I counted in this post. They will have to change it a bit and add some things over time to get to the final capacity.

Juno has some real party instruments!

as I promised, today I will write about instruments that Juno has acquired for the journey to Jupiter. Also I wont post anything for something like two weeks again because I am going with my mum and sister to Poland on vacation. After that I will be few days at home and then I will go to Germany for one year (of course I will start writing again at that time).

Juno is very well prepared to gather some data, here are all the things that Juno is capable of:

Gravity measurements

To measure if Jupiter has solid core or not scientists are going to measure Doppler shift of radio waves transmitted back to Earth. The changes of gravity from computed should be from either storms if they go very deep into the atmosphere and/or changes of density and surface of the core if it exists.

JADE – Jovian Auroral Distributions Experiment

Those are three detectors that each covers 120° + one special detector that has 270° view. This experiment is trying to observe the auroras of Jupiter by measuring the charged particles that create them.

JEDI – Jupiter Energetic Particle Detector Instrument

Right this does not correspond to the acronym but you know.. Jedi 😉

This experiment is similar to JADE except that it consists of only one detector and detects particles with lower energy.

JIRAM – Jovian Infrared Auroral Mapper

Again this one watches over auroras but also it makes infrared images of the atmosphere.


This is somewhat unnecessary camera that is going to collect pictures for public. There was even voting for what pictures it should take because it wont have so much time. As I said in the last post it is going to have some cool resolution but we will have to wait about month for it.


Juno also has magnetometer that will measure the strength of the magnetic field and its other attributes. It is quite big instrument with 3.6 meters height.

MWR – Microwave radiometer

Such thing was not used before on Jupiter so it could be huge surprise what we will see in microwave radiation because that is exactly what wavelength this instrument measures.

Ultraviolet Imaging Spectrometer – UVS

This one will watch Jupiter in ultraviolet. Here nice target are again the aurora because they are much easier to watch in UV especially because you can do it even during day.


Waves are basically two antennas which are about 3 meters long and then one smaller electronic device. This instrument is going to measure the interactions between magnetic field and atmosphere. The smaller device is mostly wire, turned 10,000 times around some bar.

From all of this it could seem that Juno is going to measure only magnetosphere and auroras though this is simply what you can do without needing to crush into the planet. (Which will happen anyway though Juno wont survive of course). All of these things are quite observable from far away and yet they can tell you a lot about the planet.


Check out these pages for more info: 1) 2) 3)

Levers are amazing!

today I want to shine light upon one of the simplest machines that there ever were. Those are levers, so intuitive that you will see even small kids use them.

SPOILER alert:

They are amazing in crushing your fingers.

I kind of connect this word with the game Neverwinter Nights where it was used for the handles on walls that opened doors and so on, I had to use translator to make sure it was right because it did not feel so.

With this “door thing” it could come up to your mind that levers are kind of long rods of wood or iron. It is quite useful to have them like that.

Take for example something very close, door handle is an amazing illustration of how levers should look like! It is long quite enough for you to open the door.. now try to take

Epic door handle

just the closest part to your door, the one perpendicular to the plane of door. Sure it is much harder, probably even impossible for you to open them. This is because the further away you are applying force from axis of rotation the easier it is to rotate the whole thing.

Lets assume you have one Czech locomotive of class 363.

V čele orient expresu.

This is old Czech locomotive… there is ENGLISH wiki page about it!

Lets say that you are able to stabilise it and you have unlimitely strong rod of something that is also weightless. Also you have something that works as axis of rotation and it is also undestructible.Levers are amazing!

Everything is put like above. Lets say that you weight 70 kilograms (if less than you have sack of sand with you, if more than you touch the ground with your feet).

How far away do you need to be if you were able to put the locomotive 1 centimeter from the axis?

Well, we have to calculate it precisely because if you sit too close you are going to be thrown across a long distance!

What you want for balance is that the final moment of force is equal to 0. Both you and the locomotive has this moment which means that:


You calculate the moment here pretty easily, there have to be to things in the equation and those are very intuitive. If you push on door handle very hard (force) it is easier. If the door handle is longer it is also easier (r for distance).


This type of locomotive weights 87 tons. Now we can calculate the moment (F=m*g):

M=87 000*10*0.01=8 700 N*m

You moment of force must be the same and you know your weight (times gravity acceleration) so there is last thing the distance.

r=8 700/700
r=12.4285714286 meters

Wow, only if you are 12.5 meters from the train you can easily rest down! The problem here is that usually in this type of physics we consider that all of mass of one object is compressed on one place called center of mass. This is the problem because in reality whole locomotive simply wont be 1 centimeter away from the center. Cool anyway 😉

I mentioned at the start that levers are good in crushing fingers.. and they are. Take for example door that is 0.8 meter long and somebody pushes it with the force of 5 Newtons which is like lifting 500 grams. If your finger is 2 centimeters from the door it is literary going to be crushed with the force of 200 N which is like putting 20 kilogram thing on your pinkie.



My thoughts on mission Voyager

as the title suggests I will be talking about the mission Voyager 1 and 2. I never mentioned them in separate post until today. It is also connected with my presentation I had on the contest.

What are those missions anyway?

Those are two space missions that had quests to check out furthest planets of our Solar System. Because of rare occasion, Voyager 2 was able to check out 4 planets (+ Earth).

Right now both Voyager 1 and 2 are still capable of transmitting signal because their battery working on radioactive materials is still ok, it is not much though, not pictures or something like that.

Sonda na fotografii NASA

Voyagers are twins.

Both were launched in the year of 1977 and are about 19 billion kilometers away from they Earth.

The thing is that both missions are very cool and they collected lot of data but they also have this “Voyager golden record”. It is record of “The sounds of Earth” which are voices  from various languages and also the plate contains some information on how to play it and where in Universe it was launched from.

I know that this was not the main reason for the mission to be launched but at the same time it was not really well made up.

Above you can see the information on how to play the record. How could anyone in the hell know what is this supposed to do? I mean, how can we know that aliens have similar technology like us and that five pictograms can explain how to use it!

There are also images on this thing! There is image of woman in supermarket, photo of Jupites and so on (you can check it out here).

The left circle explains in binary how fast it should be playing. Than the wave is typical frequency of the sound that should come out and under it is something called “scan triggering” (wut?). The boxes under it represent how the image is made and the circle is the first picture that should appear. The lines represent the position of Sun compared to 14 brightest pulsars out there and the two circles represent two hydrogen atoms.

Though this whole thing seems a bit dumb to me, I at least like that they included piece of uranium so that “alien” can know how long it is flying (via radioactive decay).


What is going up on Mars?

while thinking about today’s topic I find some random stuff and decided to share it with you. So here you go, new exoplanets, tsunami on Mars, good view on Mars and SpaceX announcement.

Artist’s impression of exoplanet.

Thanks to new statistical method there were 1,284 exoplanets confirmed[1].
This is biggest number ever in one shot. There is of course lot of data form Kepler which observes stars for those exoplanets. You can not be sure always if what you saw was really exoplanet so you need more data. When uncertainity is below 1%, it is officially agreed that the planet is there. With this new method, lot of those uncertainities went below 1% so yes they were “discovered”. Other data was “thrown away” because the percentage went lower and generally this was nice breakthrough.[2]

For long time it was thought that Mars’s terrain was shaped by its ocean that later on evaporated. But the shoreline would be graduall which is not what we observe, rather exact opposite with many geological features along it. These features could rather be explained by huge tsunamis that were formed by asteroid impacts.

Also Mars is going to be these weeks in oposition to Sun and basically really close to Earth, on about 1/2 of AU. The closest it could be would be about 1/3 of AU because its orbit is kind of excentric. If you want to see it well, just take a telescope and with good one you should be able to see even some of its geological features. If you get to see (if it is possible for normal people) Olympus Mons, say hello from me 😉

After SpaceX landed second time on the barge, Elon Musk stated that they want to land on Mars in the year of 2018, which is in two years! They have really lot of work to do so lets see where they will be in that time! (Read more here on the blog of Phil Plait)


[1]Exoplanets are planets that orbit around other stars.
[2]From the data we also know that 550 are probably rocky and 21 are in habitable zone.