Rant against Arrival

Hi,
my fellow blogger (Jitka unfortunately writes in Czech) reviewed in her last post the movie Arrival. Since I saw it yesterday I decided that I will continue with my own thoughts.


The movie is about linguist who is offered the chance to communicate with aliens that just landed on Earth on 12 different locations. Her job is to learn how they speak and ask them what is their purpose here.. thats what the movie is about.

Now if you have not seen the movie, there will be spoilers:

First I will comment on what she said on her blog:

So in the movie the aliens apparently know the future, now this puts into question ones free will of course but I do not think we have it anyway so yes, they simply know what will happen. Why do they send 12 vessels and not only one where Louisa would learn the language (which is the whole point of their Arrival). Well they needed the conflict to happen in more countries, how could she save general Shang from China if he was not going to attack? There would be a lot of differences in the story and who knows what would happen. If you know the future and you want it to happen again you will do exactly the same things and not risk small changes, yes you will act accordingly even to small details because of butterfly effect.

Now lets return to the problem of free will here. If you actually had a free will and knew the future you would have to know the future of all your decisions and combination of these decisions with other people’s decision, that would certainly be mess. Then you would choose the decision line that fits you best and would go with it… which also means that you would probably know what you will choose from the beginning, huh..

Then there is this theoretical physicist, alright his being there was completely random. Actually I think that he was there only to say the dumbest line ever in the beginning of the movie when Louisa and he (Ian) were in the helicopter and he was citing her work. It went something like “language is the cornerstone of civilisation” and he said that it is wrong that the cornerstone is science. Aha, ok really? Science would not even exist without language not speaking about the fact that if you do not learn language your mind capability is extremely reduced.. I am not saying that language is cornerstone of civilisation either, I am not really sure about it.

Jitka mentiones the idea of the heptods (aliens) to communicate via smells, that sounds interesting but I think that for animals (as we know them) it is much better to communicate with sound. This simply because sound is more reliable. If you are animal it is a matter of seconds before you and your family gets eaten and you move all the time. When monkey screams on the rest of the tribe to get away they will know it immediately, but if the monkey lets out some aggresive smell it might take minutes before it reaches the right destination.

I guess one of the aliens let himself be blasted away because he knew it was necessary for the future, though I would doubt they would have such a bad glass that would not be able to withstand the explosion.

Oh and it does not make sense how Louisa persuaded the general Shang, she only recited what his wife told him that would not probably impress him so much, there would also be pressure from other people and why would Russia and Saudi Arabia stop so suddenly?

Louisa starts to teach the language, that seems dangerous because anybody can then probably access memories from the future.. ouch, that could cause some problems. At the same time the future that she sees is not really a future since she speaks with general Shang without knowing the phone number but then in the future it can not happen since she knows it already.

Overall it was not very good movie. The amount of time left was decreasing lineary but the same was with thrill in the movie, which finally led me into seeing it whole, sadly.

Dragallur

Book review 14) Grimms’ Fairy Tales

Hi,
so apparently I have to read lot of books for my school in Czech Republic. Just about a week back I finished Grimms’ Fairy Tales. They do not really have much to do with science but here you go, next week something different.Grimm's Kinder- und Hausmärchen, Erster Theil (1812).cover.jpg


Grimms’ Fairy Tales

Grimms’ Fairy Tales (GFT) are collected tales by Wilhelm and Jacob Grimm. For the first time they were published in 1812 and in the next editions more and more tales were added. In 1857 GFT included 211 tales. Thats helluva of stories. In the internet version that I read was only 62 and it was not very short book.

The stories repeat in a way. Kingdoms with princesses and princes. Dwarfs are usually bad. Maidens are beautiful, foxes are smart (except the one where fox dies), people want to kill their pets (Bremen Musicians and others), random forms of magic, dumb people are lucky, step mothers are nasty wenches and on and on.. the themes are simply quite similar.

In the case you think that all of them are happy and tell a tale like Hansel and Gretel or Ashputtel.. no way. Lot of them are quite brutal and throughout the editions they somewhat changed. For example in Hansel and Gretel it was their own mother who wanted to kill them and not their step-mother.. then there is this tale where the step-mother kills her son and mixes him in pudding, I am not kidding.

The Straw, The Coal and The Bean

That one is extremely random tale. Some woman wants to cook and one straw, coal and bean escape. They decide to go together and then they have to cross a stream. Straw lays itself across and the coal starts to walk over it. It is still hot though so both of them fall into the stream and die, the bean starts to laugh and bursts out. Luckily tailor walks around and sewes the bean together … thats why beans have black seams.

Overall because of fairy tales like these, it was great book, nice for relaxation. Bit too long, I would not be able to read 211 of those since as I said, they repeated in the main points.

Dragallur

Picture source: Public Domain, https://commons.wikimedia.org/w/index.php?curid=471797

Cryptography and passwords

Hi,
today I will write about passwords and their security. Mostly I want to explain what “hashing” means in this context. Its certainly important issue considering that for example last year in May there were 164 million passwords from LinkedIn offered for sale.


Good site that user needs to log in wont safe your password. You should be the only person who knows it. How can they check when you log in then? Well they hash your password.

This means that when you create your account instead of storing the password which could be simply stolen away, the website will run the string through one-way function that will put out some long combination of various letters and numbers, unrecognizable from the original password.

One-way function means that you can not take the nonsense, put it into the function other way around and get the password out, one-way function may for example lose some of the original information so that the process is not reversible.

Now on the server is only saved hash of the password[1] but even that is not enough to be quite secure. The thing is that there are only several commonly used hashing functions and crackers (correct term for hacker) can still break it…

What crackers can own is called rainbow table. That is huge (in terms of gigabytes easily) table of hashes. These hashes were made from random letters or from combination of words from dictionaries. When somebody cracks the database of some website and get hands on all those saved hashes they will start to compare them in huge amounts with their rainbow table. The hash functions always create the same string from the same password so the cracker only needs to have these rainbow tables for couple of most used hash functions.

This is of course why it helps from the side of the user to have long and random password, one can not have everything on the rainbow table because of its size and it takes a long time to compate a lot of hashes.

For extra protection most pages also “salt” hashes. That means that after your password they add some random characters and makes a stronger hash with it. Every password has to have original long salt. With the salt it does not matter if it is known or not because cracker can not precompute rainbow tables for all the possible strings and the technique will become unusable.

Sites might also add time that it takes to log into account, not noticable for user but catastrophic for cracker. For example if user has to use CAPTCHA or if simply you use hash function that takes longer time to go through, you will be way more secure from brute force attacks attacks which are cracking hashes one by one simply by trying random strings.[2]

On this page you can check if your account have been breached.

Dragallur

[1]When you log in the password that you entered will be hashed again and compared to the hash that is already saved in the database.

[2]On the other hand you might me more fragile against attacks that try to make your site overloaded.

Source

Vacuum decay and Trump

Hi,
today I want to do a fun post inspired by a meme that I saw some weeks ago on Theoretical Physics Memes. Well here it is:

https://qph.ec.quoracdn.net/main-qimg-0be932f563bde21614fc7bfbcff409d9


If you dont understand the joke, its alright, I will explain. If you do understand the joke you can continue reading for the sake of… reading?

Disclaimer: I have not been using disclaimers before but the truth is I am no physicist so I do not claim to actually comprehend this stuff.

So vacuum decay or also false vacuum is the idea that you could die any second. (See I am no physicist)

Basically fields (meaning electromagnetic and other types) want to get into the lowest energy state possible. Also electrons rather like lower energy states to be more stable so, if they have more than they “need”, they will radiate it away in form of photons. Now it is assumed that these fields are either in stable position (lowest energy level) or they might be in metastable position[1], which means that there is energy barrier between the metastable level and stable, if it is “reached over” and the field drops into lower stable or again metastable level it will release energy.

If we were in false vacuum[2] we would just need to reach over the hill to get to true one.

Since particles arise from these fields some new types would appear and Universe in this place would look a bit different inside. The reason why this is connected to the discovery of Higgs Boson is that the mass that it has indicates that we may live in false vacuum, if our physics is right than we could die any moment since the false vacuum is expanding almost at the speed of light.. means we can not know if it is coming on us or not, which also means that you do not need to worry really.

Now you understand the joke though if you are Trump supporter than you do not find it very funny in which case I pity you because it is great joke 😉 [3]

Dragallur

Pic. source: By User:Stannered – Adapted from en:Image:Falsevacuum.png, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1711800

Post source mostly.

[1]They can also be in unstable position but not for long.
[2]The name false vacuum has nothing to do with the vacuum of space.
[3]Proper explanation: it is so bad that Trump is elected, I hope that Universe will end soon, oh hmm.. what is the probability of it happening?

SpaceX meets Moon (soon)

Hi,
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.

Dragallur

[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, https://commons.wikimedia.org/w/index.php?curid=46531492

Its about Trappist-1

Hi,
I noticed that in the last days lot of attention was given to this new exoplanets. Well, I guess I have to stay in the “popular sphere” and follow with my post!


Around star called TRAPPIST-1 also known as 2MASS J23062928-0502285 were found together 7 exoplanets, more on this down in the post.

First the star.

Trappist-1 is very small star in special category L which means that it is a red dwarf. You wont find this category in the normal stellar classification because this one and other are made for brown and red dwarfs and were introduced later on. This of course means that Trappist-1 is not very bright or very hot and NOT visible to naked eye (it has apparent magnitude of 18.8 which is way outside of what human eye can see).

All pictures of these planets are artist’s impression.

 

The planets were discovered using transit photometry. Method that takes advantage of the planets blocking out some of the star’s light. In 2015 there were 3 discovered already and in February this year, astronomers in Belgium found another 4.

There names are truly beautiful: b,c,d,e,f,g,h (aka. Trappist-1b…)
b,c,e,f,g have similar size to Earth and d,h have radius somewhere between Mars and Earth. e,f,g also orbit in the habitable zone of planet which is an area around the star where liquid water might stay on the surface.

Bit of a problem is that since the planets are so close they receive lot of radiation from Trappist-1 and are also probably tidaly locked, which means that they are facing the star with always the same side, thats what is happening to our Moon too. All of their orbits’ radiuses (semimajor axes) are in matter of few millions of kilometers. For Earth this is 1 AU or 150 millions and for Mercury roughly one third. Their years last few days, for Trappist-1b it is just 1,5 days. Those are definitely some crazy numbers but since we know so little about formation of new life we can not really say how high the probability of something living there is.

NO signals were detected from that direction.

Dragallur

PS: You would have amazing view from the planets since they are so close together.

Source of picture: By NASA/JPL-Caltech – Catalog page · Full-res (JPEG · TIFF), Public Domain, https://commons.wikimedia.org/w/index.php?curid=56513150

Pioneer Anomaly

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

Pioneer10-11.jpg

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.

Dragallur

Pionner picture: By NASA – http://nssdc.gsfc.nasa.gov/image/spacecraft/pioneer10-11.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2878008

Europa Multiple-Flyby Mission

Hi,
today I am going to write about proposed mission to investigate Europa.


Europa Multiple-Flyby Mission is a plan consisting of orbiter and a lander directed towards Jupiter‘s moon.

The reason why to choose Europa is quite clear. There is probably liquid water under its surface and if one launches such a thing, it might get public’s attention.[1] (Which might be now more important than ever considering how Trump wants to cut down NASA’s budget especially on the most important thing that they do: Earth’s climate monitoring.)

First of all the orbiter, which would be launched in the next decade, would learn as much as it could about the surface of the moon, Jupiter’s magnetosphere (see later), weird water

Composite image of Europa superimposed on Hubble data

This is two images of course. The original does not have the Europa in middle but only black spot. You can see the plumes on roughly 7 o’clock.

plumes and so on. There are 9 instruments together planned.

Instruments on those orbiters are able to collect data faster than we can receive it. This is because there are more mission that need attention of our receivers. Those are not some small receivers but specialized ones and all missions have some time to send information. For example New Horizons, just from its flyby of Pluto kept sending data for some 6 months.

In case of Jupiter oriented mission this might be a problem because Jupiter has extremely strong magnetosphere which will probably damage the instruments in matter of few weeks. This way it is best to get close to Europa and then get away as soon as possible and send the data later. This can not be done for the lander so it really lasts in matter of days. (Yes, it is still a problem even if you cover your equipment under 150 kilograms of titanium as is planned!)

The lander is thing planned even further into future, around 20 years or so. Much can change and we will see what the priorities are at that point.

Dragallur

[1]People will probably get quite excited by mission promising founding signs of extraterrestrial life.

How do we know that Sun is a star?

Hi,
today I will shortly explain how is it that we know that Sun is a star and why it is not so trivial.


When you look up on the clear sky in night you see dots and they are said to be basically the same thing as our close Sun. They definitely shine, but not so much, they are not very warm, light up in different time than Sun, for some reason twinkle and are way smaller, even with binoculars they are still dots.

Hell yeah, they are quite small dots! Even if you take our best telescopes you will always have them so tiny! They are “point source of light”, which means that they are simply so small that from our view and practical purposes they are dimensionless.

They are huge though, most a bit smaller then Sun but still big, but so far away that they seem only as points. If even now we can not see the star’s surface as anything else than a dot, how do we know that it is the same thing as Sun?


The thought of Sun being star was there for some time. I found that already guys in ancient Greece thought that, the same idea came to the famous row of astronomers like Copernicus, Galileo, Kepler, Newton and others but they still did not have an access knowledge that would prove it.

In 1838 Friedrich Bessel measured the distance to star for a first time without considering anything about it (I guess he might have used stellar paralax but I am not sure). He found that the distance is huge, as we know today and soon we calculated that these dots are actually about as bright as Sun, also with astronomical spectroscopy scientists found out that what is happening there is also happening here. To make it clear, we do not have a “close up” image of any star, nor do we have image of any exoplanet.. for now that is simply impossible, still we can admire the cool Jupiter that Juno is taking pics of! (it is literally porn for eyes 😉 )

Dragallur

Precession

Hi,
in the last post about Polaris I mentioned precession as the effect that causes change of North and South stars. I did not really explain what is happening there so I decided to make a short post only on that topic.


There are two other good examples of objects that precess alongside Earth. Take gyroscope for example:

On the left you can see gyroscope. It consists of spinning wheel (orange/yellow) and a pin on which it stands. When you speed the gyroscope up it will be able to stand as you can see on the animation. This is basically what Earth looks like and what it does in matter of 26,000 years.

There is a thing called torque in physics. If you hold a pole on one side and something is hanging on the other side it will be very hard to lift it up. You will have to use both of your hands and one will push down and the other up to counter the torque that the objects has, that is a force causing it to rotate around one of your hands.

If you spin the thing though it will suddenly be easy to lift the thing, why? Because of angular momentum and conservation of angular momentum. If you spin on your chair and stretch your arms and legs you will slow down but if you do the opposite you will speed up. No force is acting on you only conservation of angular momentum takes place. Angular momentum is calculated as the amount of mass spread in distance from axis of rotation. If it is further away it does not need to be so fast as then the mass is closer to the axis.

When you speed the object up the angular momentum will stay conserved so you do not need to provide the torque anymore, in other words it is going to be easy to lift the thing up. If you try to change the angle in which it spins it will feel weird and it wont like it.

Even than gravity is still pushing down. If you add the vectors of the forces together, you will find out that the object will rotate –> precess. The slower it is the bigger the angle in which it precesses. If the force would be applied only on one spot all the time then it would not precess. Take a round sheet of cardboard and rotate it on tip of pencil. If you blow on the spot close to you the thing will tilt left from your point of view. Gravity though will try to tip the thing over always on the side that is lower and thus it will continously change and rotate – precess. If Earth had no tilt there would be no precession.

Dragallur