How slow can slow motion get?

Hi,
ever been wondering how slow can slow motion get? If you hang for a longer time on YouTube eventually you might notice the channel The Slow Mo Guys or Smarter Every Day, both of them feature „quite often“ slow motion videos, meaning videos that have many frames per second (FPS). If you then slow the frames down you will get very slow video showing detail of whatever you are filming, whether it is flame tornado or AK-47 under water.


The slowest I ever watched is this one: https://www.youtube.com/watch?v=xbuvcQrAOSk

It has FPS of 343 915. That is a lot and in the video they are cracking glass container with high temperature difference. The video is so dark because in the short amount of time, not much light can get into the camera and that is often the limit for such high speed filming. You can also see that even though the video is so slow, the crack still propagates through the glass in surprising speed.

MovieBut this is not the limit, you can go much slower but it requires whole different technique. With 1 trillion FPS you can actually see light traveling through medium, it looks pretty impressive but how can it be done?

The scientists use a laser to lighten up what they want to take photo of. They take a 1 dimensional pictures, basically line of pixels[1], couple hundred times and then with a smart mirror they move along the object that they photograph. This technique is called femto-photography and the event on stage has to be performed many times before one gets the picture.

To put it in different words, you take a titanium-sapphire laser. Lighten up the object for a short time. Capture the photons that bounce back to you. Repeat over and over again and with some mathematical reconstruction techniques you got your result:

https://www.youtube.com/watch?v=qRV1em–gaM

Interestingly enough this kind of device is able to see around corners and has very high potential for use in many technical fields if we are able to make it work faster and in smaller devices.

Post based on TED talk.

Dragallur

[1]It is not really line of pixels as you can read in the next paragraph. You are getting back couple of photons and through the mathematical analysing you get the picture.

Gif source. http://web.media.mit.edu/~raskar/trillionfps/

 

How do bearings lower friction?

Hi,
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.

Dragallur

Habitable zone of a star

Hi,
habitable zone of a star. Sounds like a comfy place, right? Well it can be. It is at least on (tiny portion of) Earth which is an example of object in habitable zone. Such a „zone“ is important for astronomers, or maybe it’s just important for headlines in newspapers.


Habitable zone in a Solar System based on luminosity.

Habitable zone is an area around star where we, with quite limited knowledge on this subject, think that life could be. The simplest „definition“ is that it’s the area where satellite (such as planet) would be able to sustain liquid water. We cannot be sure of course if life needs it but it is the case for the one that evolved on Earth.

The true habitable zone is something a bit more complicated. The simplest case of a planet would be one that behaves as a black body, that means that it absorbs all radiation (light for example) regardless of its wavelength. This is immediately just an assumption because such a planet does not exist. Earth just as Uranus or Mercury reflect light, the planet’s albedo describes this. Albedo is an attribute telling us how much object reflects light. 0 means that it is a black body and 1 means that it is white body aka perfect mirror.

There are even more factors that one could consider. For example, when planet has thick atmosphere it can sustain liquid water (and life) even further out from habitable zone on the other hand if that happens to planet like Venus which is already pretty close, you have got hell. If satellite orbits with high eccentricity the conditions are again different.

It’s hard to combine all of this together which results in lot of different outcomes depending what model one picks. Estimates for Solar System are between 0.9 or even 0.6 to 1.3, 2 or 3 astronomical units. In most of them Earth is just on the inner edge. These numbers were pulled from Wikipedia.

When we hear in news that a new exoplanet was found in a habitable zone it might not mean much. This news usually come alongside the information that the planet has similar size that of Earth, it’s not like we could travel there or anything, now we are mostly collecting data and learning.

Dragallur

HZ picture: By Habitable_zone-en.svg: Chewiederivative work: Ignacio javier igjav (talk) – Habitable_zone-en.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8462897

Problems that we will have to face

Disclaimer: This is my opinion, not advised by anybody, feel free to comment below.

Hi,

There are two problems that we as humans will have to face. I will write about the two that I think are crucial and only now people start to appreciate them.


The first problem is Global warming. It poses a lot of threats not only to fragile ecosystems but to whole Earth. Some of the effects listed from Wikipedia are: extreme weather, sea level rise, ocean acidification, changes in agriculture, environmental migration and much, much more [1].

Global warming is the first problem that we need to address but in this post, I will concentrate on the next issue on the list. Humanity will eventually die out if we are not able to spread in the Universe [2].

First, we could of course ask the question when we should colonize other planets or even if it is good idea. Let’s take a scenario, when humanity successfully colonizes Mars and at the same time Earth is becoming more inhabitable. At some point, we simply leave it behind, maybe let it rejuvenate without ever learning how to live in a way that does not cause rest of life extinct. What would continue? Maybe we will be able to spread out in the rest of the Solar System and eventually leave it behind. In what state though? And does it even matter if Mars which is right now mostly empty wasteland suffers any damage if it is even possible? Maybe we would change into species that travels the Universe and leaves dead rocks behind? What if we encountered other life out there, would them await the same fate as Earth? We are authors of our own morality and clearly there does not seem to be objective one. Our values change, we are starting to really appreciate our surroundings, the question is, are we fast enough?

Picture of Mount Sharp on Mars, taken by Curiosity rover.

Dragallur

Note: I am aware that there are different things that could happen. I took time today to write shortly out what I thought about one of them.

[1] There are also problems not related to Global warming but are as well very global, for example what are we going to do with plastic.

[2] See also, gamma ray bursts, solar eruptions (big problem but probably no immediate deaths), huge asteroid collisions and other things that would wipe us out.

Red Bull Stratos and its giantic balloon

Hi,
we all know that helium balloon raises up which makes it such a fun object, most things in every day life do not do that. This attribute can be used to raise objects or even humans quite high, but at one point you get a problem, the atmosphere is less and less dense.


Red Bull Stratos logo.svgRed Bull Stratos was a project involving helium filled balloon and a capsule with human (Felix Baumgartner). In the year 2012 it raised up to almost 40 kilometers and then the skydiver jumped down. He reached supersonic speeds (faster than sound: 1234 km/h).

In my physics class we talked mostly about the balloon because of what I mentioned in the first paragraph. 40 kilometers is very high and the pressure there is only about 0.497325257421 Pa which is basically vacuum since the atmospheric pressure is 100 000 Pa. (I used the barometric equation)

Because of this, the balloon can not rise so high in thinner air even though the helium is lighter than air. There is so little of it that it does not provide the necessary lift and the balloon has to be huge. In this case it had 9 144 000 cubic meters! Thats a huge thing. The problem of course was that it was not lifting up only one human but the capsule with all equipment weighted 1315 kilograms and the material of the balloon had 1681 kilograms[0].

The whole project was kind of supposed to be for science and finding out how body reacts to high speeds and for further development of pressurized suits[1]. At the same time there was a lot of helium used which was then of course lost. Beware because helium is on the list of endangered elements!

Dragallur

Btw. You can check out my Patreon site here!

[0]The helium also has to be lifting itself.

[1]At about 18 kilometers the pressure is so low that the water in human body starts to evaporate (not all because blood is enclosed but for example saliva). I wrote about that in this other post. To survive you need to be in a suit.

Logo source: By Source, Fair use, https://en.wikipedia.org/w/index.php?curid=37329038

These telescopes are huge (E-ELT, OWL, VLT)

Hi,
today I will write more about telescopes. In a previous post I already mentioned why radio telescopes like Arecibo are so huge, its because of the long wavelength. Today though I will concentrate on another type of telescopes and those are the ones that sit on Earth and collect information from visible light (those are called optical telescopes).

Comparison of various telescopes. Note OWL, the big circle in the background and even bigger white Arecibo.


I already mentioned Hubble telescope and James Webb Telescope (JWT) that is planned for launch next year. Those are in space so they have quite limited size. Down here we can build bigger ones. Right now in building phase is the E-ELT (European Extremely Large Telescope). Its primary mirror will have 39 meters [1] making it the largest optical telescope. It has to be so big because otherwise it could not match the ones in space. This is because we have our lovely atmosphere in the way and it makes harder for telescopes to distinquish small objects (though these days we have software that is able to account for that).

VLT aka Very Large Telescope is already working optical/infra-red telescope. It consists of 4 telescopes each of them with primary mirror of 8.2 meters in diameter. They can work together to make images of angular resolution 0.001 arcsecond. In one post I said that we are not able to take an image of star other than just point like source of light but apparently that is not true so I apologize for it:

First Direct Photo of Alien Planet Finally Confirmed

First confirmed image of an exoplanet. The ones that we can see are bigger than Jupiter and usually quite far away from their star. Credit: Gemini Observatory

VLT is second, right behind Hubble in the amount of scientific papers that its work produced (in the field of visible light/infrared telescopes).

There are many other telscopes that I might mention in the future like Thirty Meter Telescope but I will end it with OWL – Overwhelmingly Large Telescope. It was supposed to be the largest telescope ever, with primary mirror of 100 meters! The price was estimated to be about 1.5 billion euro and because of that it was decided that its not worth it. If we do not kill ourselves we might see giants like those in the future though I have no idea how the scientists, or whoever does it, will name them (UGHT – Unimaginably Giantic Huge Telescope).

Dragallur

[1]Just as JWT, the mirror is made from smaller segments. In the case of E-ELT it is because the mirror would be too heavy and we do not have the technology to build it and in the case of JWT it is because you have to somehow get it into orbit.

Comparison of telescopes: By Cmglee – Own workiThe source code of this SVG is valid., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33613161

Knowing the future, brain twist?

Hi,
two weeks back I wrote about the movie Arrival. I did not really get into the problems that arise when somebody knows the future, I will try to settle this today.


Alright, lets say that you just acquired the ability to know what will happen in the future. Cool huh?

First problem, do you have free will (meaning if you can choose to do something or there is no way to actually choose anything)? Lets start with the answer: yes, you have free will. Basically two things can happen, if you truly know what will happen then you can not choose any other option which means that by knowing the future you and everybody else will lose free will if you could choose something else than what the ability tells you then it would not be telling the future. Something else could happen though, you could know all the possibilities that arise from your decisions and the decisions of others. Funny would be if you would see it for the decisions of others, then the ability would be useless for longterm predictions where people all across the globe would interconnect with their decisions (do animals have free will, which ones do and which ones do not?). You could for example see that in 40 years there are couple (a lot) of lines that go to Third World War but there would be so many people involved in changing couple of important people that you could hardly do anything with it. At the same time if your brain would be organized in the mess you would immediately know what option you need to take to optimize whatever you want to optimize. Much easier would be if everybody else lost their free will and you alone had it.

The real fun begins if you consider no free will aka determinism. You know exactly what will happen but you can not change it. Imagine standing on cross roads, you know you will turn to left, its the future and you can not decide otherwise but there does not seem to be anything that would actually prevent you from turning right. If you do it, it means that the ability was telling you exactly that from the beginning but then you would turn left…

Lets consider thought experiment:

There is a robot that has very strict type of thinking. It is standing in a hall way that splits into two corridors, left and right (it is driving towards the left). Nothing miraculous can happen there, nothing that would prevent the robot to go where it is programmed to go.

You are at the headquarters and know where the robot will turn or simply what will happen there. You tell this information to the robot and the robot will turn exactly the other way. For example you know that he will turn left. You send him the information and he according to his program turns right which means that your ability is not working and this simply can not happen, you can not tell him the direction because he would do the opposite. What will you tell him? What is the future?

There is one more line of code in the robot: if you get the information “you did not decide”, you will turn left. This is to make it harder, the future would switching between left and right indefinitely, meaning the robot would not do anything and we do not want it. The only solution that I came up with is that he will actually not decide, you will send him the information: “You will start going left but when you will get this information you will turn right. After hearing this you will turn left but when you hear this information you will turn right again…” it will continue and then it depends how the robot is made. If it waits until the stream of information halts then it wont ever decide and you will speak to him forever. If it will take the information and while it processes the next part it will start to act accordingly to it (meaning the opposite way), the robot will slowly move towards left or right. At some point it will be on the threshold which raises a problem of course and I guess there is nothing stable to tell him without destroying the ability that you gained, you know what he will do but you can not tell him.

The last part would be the same scenario as if the robot could teleport from the beginning but if you have to say the information then it will result in a paradox. In normal non-robot life you would probably run into more complicated scenarios where knowing the future would not alternate you decision which is the whole problem we are dealing with. But if you would not and your ability would HAVE TO work then… ???

BOOM!

Dragallur

Pareidolia

Hi,
today I will write about pareidolia a commonly seen phenomena. People often see familiar objects in completely random things, like rocks.


Clearly there is face in the upper middle part of the picture on the left. There is definitely sign of both eyes, of nose and mouth, thats more than one needs to SNice.svgrecognise face in something, consider the following one on the right. Do you see the black thick circle filled with yellow color, two ellipses and curved line extended in the ends? Yeah me too.

The point is that humans are great in recognizing (most often faces) in things that are actually not them. The first picture is photo of region Cydonia which is a area on Mars. It was taken in 1976 by Viking 1 and of course people thought that it was proof for extraterrestrial life! Well if you take enough photos of Mars there is high probability that some of the rocks there will resemble primitive faces.

Pick me! Some may bypass this pear for its blemished skin while others will see how eager it is to please

“I am the evidence of life on Earth, beware!”

Pareidolia does not happen only in images but also in sounds. For example there is a group of people who listen to so-called “ghost boxes” (sub category of ghost hunters). Ghost box is a box that is skimming quickly through radio channels. This creates lot of background noise and static noise with mix of what you can hear from the actual radio.. they say that the ghost can easily communicate through it.

Simplest explanation is of course that they just interpret extremely bad audio as some kind of words, plus if they listen for many hours they will eventually pop out something that will be an answer to your question, here is a link so you can consider for yourself, remember humans are great in interpreting random noise as actual words[1] (skip like 3 minutes for actual talk).

The story of the original Mars picture got stretched over many years. 2 decades after taking the picture, there was much better one taken by Mars Express as you can see below it was just the low resolution of Viking spacecraft.

There are many things that can trick us so it is not best to take the first explanation that we can think of, be sceptical and do not share if you do not know anything about it.

Dragallur

[1]The “answers” should be mostly made by random quotes from songs.

Smiley: By en:User:Mystìc – Originally created by en:User:Mystìc at en:Image:SNive.gif. Vectorized by Psiĥedelisto, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=55079042

Pear: http://www.dailymail.co.uk/femail/article-3280816/What-photos-s-faces-suffer-facial-pareidolia.html

 

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?