Why do stars twinkle (and planets not)?

Hi,
I felt so embarassed that I finally had to find it out and now I am writing this short post about it. For few years, roughly, I am studying astronomy yet, I never knew why stars twinkle and planets not. I confess.


Stars twinkle because the light that reaches us goes through atmosphere and atmosphere is not very homogenous – smooth. Air refracts light and there is different temperature once in a while, humidity and so on, I think that lot of factors play the role. This causes the light of star to scatter a bit and creates the twinkling effect.

Planets do not do it. This is great because you can identify them extremely fast on the sky and you do not mistake them for some other bright star. Why? Their light still goes through atmosphere. Because they are not “point sources”. Stars are so far away that even with best telescopes we see them only as points. Planets with simple telescope on backyard already have shape. Some of their light scatters one direction, some the other and it basically cancels out creating nice image. This is also why it is better to go star-gazing in the winter, colder air does not create so much “noise” on the picture.

Dragallur

Why golden trash bins do not help (modern equipment in schools)

Hi,
(few days back) I am sitting in a classroom, slightly bored by the teacher saying what I heard the day back. After few minutes I am being offered to do experiments alone. I agree with the hope that it is going to be more fulfilling. Instead of getting full access to the laboratory[1] I sadly accept white box, aka trash bin.

https://www.fdgate.com/photo-2/high-school-physical-optical-experiments-box-experiment-box-lens-optical-instrument-physics-experiment-equitment-m-0915.jpg

This is kind of similar, the fact that it is chinese[2] kind of fits the situation since my german is not so good yet.


Such a box contains “scientific” equipment for the study of electro-magnetism. This consists of few cabels, power source, resistors, capacitors, all properly laid on green boards. Function generator, some frequency and amplitude thing, two coils, magnet and some stuff to hold it together. This is probably almost perfect list of things that costs the school hunderds of dollars. I took it with the manual that contained roughly 15 experiments and decided to do one of them. I put components together as it said, found out the thing it said I am supposed to find out, it gave me the formulas to calculate it.. that is all.

So now the rant against these boxes (thrash bins as my host-brother pointed out).
The problem is that such a box with set up equipment and set up experiments does not enhance any creativity in students. Especially building circuits could be one of the cool things where you try what happens when you connect this and that. That is probably the biggest problem, you can just follow some manual and not understand what is going on. Also these components are totally dependant on each other and you can use only this box alone, there is no room for expansion or only limited. Not speaking about the cost, there is another trash bin like this for 800 euro. It had wagon, line on which the wagon could drive, two movement sensors and some things to hold it together and so on. We used it during physics class to demonstrate Newton’s 2nd law (F=ma). It took so much time to set it up, to measure it all to 3 decimal places. Actually it took 90 minutes and we did not get even to the formulation of the law. People were bored and I bet that if you asked half of them what was this whole about they would not have a clue.

This is modern equipment.. and it is useless. If they bought separate components boards to built circuits on, they even have those in the school but they are not used anymore. These days teachers probably think that they can not get better with chalk and a board.

Dragallur

[1] I do not think it would be a good idea to let me there alone though I go there anyway every monday with my host-brother.

[2] I do not know if it is chinese.

Book review 12) Harry Potter and Philosopher’s Stone

Hi,
I have read this book already in Czech and heard it many times on audio and I have seen the movie couple of times. Now in Germany I have finished it in German so I decided to leave it a review here. Of course everybody knows Harry Potter so I will make it little bit different.


Rant against Qudditich.

Despite the fact that the game is awesome, its rules do not make any sense. The obvious part is the snitch which gives 150 points and ends the game. There is no point in catching the snitch if the difference between your team and the other one is more than that. Viktor Krum in the national game in the Goblet of Fire for example, catches the snitch and they lose, good job😀

Rant against Defence against Dark Arts.

While whole Harry Potter series shows us extremely low number of spells which part of are completely useless, Defence against Dark Arts is the best joke. Most of the time they are actually learning about some random creatures and how to fight with them or what is their weakness (this is not what happens in Philosophers Stone) while in 6th year you will learn how to apparate anyway, which is basicall,y how you can escape anything. There might be something said in the upcoming movie about magical animals so we might find out that it is actually useful a bit.

Rant against other stuff.

Somebody killed unicorn, very strong animal which is extremely fast and its blood has unique attributes. What are we going to do? Send bunch for 1st year students, dog and guy who is not allowed to do magic!
Did Hermione, Harry and Ron really thought that it is good idea to go after Snape/Quirell? They must have known that teacher would be able to wipe them out in matter of moment from the Earth’s surface.
The points for the Cup kind of lost most of its meaning after Harry, Hermione and Ron getting 160 points and next year Ron and Harry getting each 200, people would really hate Dumbledore for doing this (not mentioning the 250 in 5th year).
Quirell could use Avada Kedavra on Harry right when he came to the mirror instead of talking about stuff. Or use Legilimence or use Imperius to get the information, not so hard really..

I like this book still of course, though I have read or seen it so many times that I just can not unsee some paradoxes that are there.

Dragallur

Eating the spiciest natural chilli

Hi,
last Sunday I was at neighbors with my host family for dinner. We ate some pumpkin soup and then I noticed these nice small peppers piled up in the bowl. Already I heard that it is not good to put them in your food so I decided to take it as challenge and take one. People at the table noticed and warned me that I probably do not want to eat it. I was soon persuaded not to take it and rather wanted my host brother to try it and see how it goes.

Yup, this is what it looks like.

“These peppers are the spiciest natural growing peppers.”
“Oh, ok then.”

He said that he is going to split with me. I finally agreed and stuffed half of the pepper into my mouth with some milk next to me and bread with thick layer of “Philadelphia”

https://i2.wp.com/groceries.iceland.co.uk/medias/sys_master/root/h8e/h01/8830465802270.jpg

This is called lifesaver.

After few bites it started to burn a lot. It is quite nasty but the real pain came when I swallowed for the first time. When it hurts in the mouth you can just calm it with bread as it touches the sides of your mouth but when you throat starts to burn it is way more difficult. In something like 15 minutes it was over. Not so much because of pain but simply the pepper, I cried a lot but hey it was quite interesting.

If you decide to try it out, there is one thing to keep in mind. The pepper is going to burn more than one time, actually it might burn three times.. you will know what I mean after you eat it😉


Anyway there is a chart called Scoville scale, I thought I already wrote about it but then could not find it so here you go.

Spicy peppers have inside neurotransmitter called capsaicin. It fakes your feeling as it bounds on the nerves that are responsible for you to experience heat. Capsaicin is not solluable in water which explains why it wont help you to drink it when you eat something spicy. Milk is better and dairy products generally help. HCl of course helps too.

Capsaicin itself has 16 million points on Scoville scale which is about 8 times as much as the spiciest pepper which is right now Carolina Reaper with individuals well over 2 million. The pepper that I was eating is 1.5 million almost (which is average) and it is called Trinidad Scorpion Butch T Pepper.

Dragallur

Jerks are even in physics

Hi,
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.

v=m/s¹
a=m/s²
j=m/s³

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!

Dragallur

[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.

How long is a year actually?

Hi,
today I will write about a year. The thing is that as in many other subjects when you look down into the simplest things you might find that they are not as simple as they seem. So how long is year? 365 days? 366 days?


You very well know that every 4 years we have 1 extra day in February. You might also know that this is because year is not 365 days long exactly but roughly 365.25 .. its important to say roughly because it is not perfectly true and it matters how you define one year.

First lets see how we define one day. One would say that it is the time that it takes for Earth to rotate once. Problem is that we need to define some object to compare it to, some ground, some reference point. It might be the Sun, but Sun is too close and since we go around it, this would change the length of the day.

Sidereal day is the day that is defined as a rotation of Earth around its axis compared to very distant stars that are relatively stable. 23.9344699 hours… that is pretty close to 24 that we use, but it is not what we use.

The thing is that we decided to use what is called solar day, which is in fact compared to Sun. As Earth rotates around its axis, it also rotates around Sun, which makes the solar day different length.

This is how the effect looks like. You need to turn Earth n.2 by little bit more since it moved around the Sun too.

Problem is that the length of solar day changes since our orbit is sligthly elliptical and when we are closer to Sun we are faster which means that the solar day is shorter and there is more time needed for the same spot to face Sun again. This effect adds up to almost 365.25 solar days in a year. If it was so simple we could just add one leap day every 4 years to make up this 0.25 difference but it is actually 0.242181 which makes difference over time.

 

Julian calender ran with 0.25 for a long time but after about 1500 years it was already 10 days behind of the real date and Christians wanted to predict Easter exactly so they changed on Gregorian calendar. This calendar is the same, except that if the year is divisible by 100 it wont be a leap year, though if it is also divisible by 400 it will be a leap year. This almost fixes the problem, though every 3216 years one day is still off from the real time. Yup. Check out this video to see how we can improve this slight mistake:

https://www.youtube.com/watch?v=qkt_wmRKYNQ

So thats it. But you can not really capture the length of year or day since it changes all the time (effect of other planets and what happens on Earth). Check out this video which I used mostly as a source, it has got cool animations that will help you understand it:

Dragallur

Is this a proper perpetuum mobile?

Hi,
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.

Dragallur

Solution to 12 coins balance problem

Hi,
in the last post I described this cool balance problem with 12 coins where one of them is false one (heavier or lighter than others). You are allowed to weight them 3 times to find out which one of them it is and if it lighter or heavier.


The hint that I gave you is to separate them on 3 groups of 4 coins. Otherwise it is not possible to solve it. For the first one there are two options as you weight 4 coins against 4 coins.

If the outcom is even it goes as follow:

  1. If nothing happens the 4 coins that you have not used must have the false one. Now this is quite tricky. You have probably come out to this part but you have to use all the facts that one weighting will get you as you will see. If something goes down, it is good to know it and vica versa.
    1. a) Now you know that the rest of the coins (4) have to have the false one since it was even. You take one away and put the three against 3 that you are sure about (you have 8 of those). If it is even you know that it is the last coin and you just weight it against one of those normal ones to see if it is lighet or heavier. If you find out that one of the three has to be false you will remember if they were heavier or ligher. Then you take two of them and weight them against each other. The one that did the same thing like in the last weighting is the false one. (If in the 3 vs 3 it was heavier you are searching for the heavier side again.) If they are even you know that it is the last one.
  2. Now it can also happen that one side from the first weighting is heavier than the other. All of the 8 coins are unknown but you can use the fact that one went down and the other up so you need to remember that fact. You also need the 4 coins that you know must be all ok. Put three of those on the “lighter” part. From the lighter part move three original to “heavier” part and from there away three.
    1. b) The easiest thing is when the heavier part is again heavier. Then it has to be one of the original coins from both side which are only 2. You weight one of them against any other coin to get the result.
    2. b) If the part that was heavy is lighter this time, one of the three coins that you moved from lighter to heavier last time must be the wrong one. It is also lighter as you know. Weight two of them against each other. If they balance it is the third one if they do not it is the lighter part.
    3. b) If they balance it must be one of the three coins that we removed completely. We use the procedure described in the last post to find the solution, it is heavy coin then.

Now that is for solution. It is not easy to come up with it and there are some even more difficult versions. Thanks for reading and thanks to Wikipedia for the solution.

Dragallur

12 coins balance problem

Hi,
today, in this short post I want to show you this cool puzzle that I first encountered on my summer camp. The problem goes like this:


You have got 12 coins. One of them may be false one. You can not know by looking but you have a balance weights. You are allowed to use it 3 times and find out which one of the coins is heavier or lighter (you do not know and it might happen that none is).

I really recommend you to try it out. I almost had a solution though when I checked it I saw that I had mistake in one of the scenarios. Try it out for yourself and in next post I will reveal the solution.

Dragallur

HINT BELOW:

 

Try to take first step of weighting 4 coins against 4 coins, it will help you😉

 

Private companies take the space industry by attack

Hi,
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.

Dragallur

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.