How does atom looks like?

Hi,
this was a question that friend of mine asked me on one contest I was this weekend. I was sure with the answer but after I said it I was not able to come up with the reason for it, at least I was not sure enough to say something clear.


So what exactly needs to happen for you to see it? There must be a photon which is reflected off the surface. How does this look like anyway on the atomic level? Well the light hits some electron in its way. There is lot of free space so this is why things that are not transparent can be if they are thin enough. The electron absorbs the photon, jumps to higher level (excitation), then it emits photon. Now on what you see depends upon its wavelength. So different materials will like to absorb different wavelengths making the object to have color. You can only change in what orbital you will have the electron so I guess that this is the fundamental difference between various colors of objects (though I did not check it).

So when electron emits the photon you simply do not know what the electron looked like. The only thing that you can get is just photon of some wavelength and there simply is not any way to look on some kind of surface of electron. Another factor is that the light has too big wavelength and you can not observe surface with that because the photon kind of just flows around and when you get to wavelength of the size of atom or smaller, the energy of the photon is so huge that the electron is anyway blown away.

There is nucleus too of course and normally photons do not get there because of this electron cloud around and nucleus is tiny. Otherwise from what I found it seems that again the proton and nucleus as whole is way too small and you can not actually map the surface.


 

But I was talking only about electrons and nucleus. You can actually see atom as whole. Not by microscope because visible light is way to huge. There is what is called Abbé difraction limit so you have to look for atoms in different way, using for example electrons (electron microscopes[1]) and then recreate the image using some cool physics, this is for example picture of silicon carbide:

And the one below is picture made by IBM of individual atoms that are shaped like the letters of IBM.

So while you can not see the atom, you can observe, not electron though or even the nucleus at least in ordinary way. You can for example measure energy or calculate the shape but you can not see them as physical objects.

Dragallur

[1]Electron microscopes observe how electrons bounce of the surface just like photons.

Read more: 1) 2) 3)

pearshaped-2WEB.jpg

The shape of Radium-224 nucleus

 

Book review 1) The Particle at the End of the Universe

Hi,
I saw already lot of people to do book review, like Joseph from Rationalising the Universe or Abyssbrain from Mathemagical site. I have already used a lot of parts from this book in posts about dark matter, dark energy, particle accelerators and so on.

It is book: The Particle at the End of the Universe by Sean Carroll. It is about particle physics and the Higgs boson.


This book has 13 chapters and three extra three parts explaining some stuff around.
Author starts the book with short introduction to history of particle physics, what people thought that was making up everything. He mentions elements, atoms and so on, then he introduces higgs boson and his role in standard model of physics. He explains why he thinks that it is important to study it and what part LHC plays in this.

In second chapter Sean explains why Higgs is also called “god particle” and the relationship of physicists with god. There is also review of properties of Higgs and some things about fields.

In third chapter author introduces whole standard model and how higgs boson changes it. There are parts about all particles and all four interactions.

Fourth chapter is about the story of accelerators and how they work. This continues to next chapter where there is description of all the work that had to be done to build LHC with credit to all people. Author describes how are particles detected and how they decay.

Whole chapter is just about fields and gravitational waves continuing about symmetries and how they are broken. This is also probably the most complex part of the book which I had to read more times to really get to know what is it all about.

He continues with deep look into finding of Higgs boson with stories about all the people around, and the excitement about it.

There are stories about destroying the world with LHC creating black holes and author perfectly talks about the way news are used in magazines and how physicists were trying their best to not let spread a wrong news about Higgs.

In 11th chapter Sean is talking about Nobel awards for particle physics that led towards Higgs.

The book ends with text about the new things that are now opened for scientists to discover when they know that the particle really exists.

In three extra parts author adds some more context to spin, standard model and Feynman diagrams.


 

This book is really well written and I give it 10/10. I really recommend it to anybody who wants some introduction to particle physics because with all those analogies you will never be lost. I like how Sean also describes all those people around the great work and how all of this makes the whole picture and story behind “The Particle at the End of the Universe.”

Dragallur

Picture of Czech book
Picture of English book

The book review of: The Organized Mind
The book review of: On the Origin of Species

Higgs boson for dummies!

Hi,
finally here it comes, here it goes, post about Higgs boson is coming. Lets look what the “god’s particle” is how physicists found it and what it means.


 

God’s particle

Lets see how Higgs boson was named the god’s particle.

One of the best particle physicists Leon Lederman who found out that there are more types of neutrinos and so on and on. He wrote a book named the “God’s particle”. The book was partially named like this because the publisher did not want it to be named “Damned particle”.

He did this and now all physicists can agree on one thing, they hate this phrase because Higgs boson has nothing to do with God.

While all journalists can agree that “God’s particle” is amazing phrase.

So if you want some physicist to be angry on you, just mention the God particle and he will never forget.

Higgs boson was found 4.7.2012 in Large Hadron Collider.


Higgs field

What is actually more important than Higgs boson, the particle, is the field from which it came, this is the Higgs field. I already talked in last post about fields and how specific vibrations can form particles. Higgs field can do this too and it makes the higgs boson which decay almost immediately and is really hard to detect.

Higgs field is a very different from other fields because other fields can get to 0 energy while Higgs field can not. What is more accurate to say is that non zero value of Higgs field is less energetic than zero so Higgs field does not want to fall on the value of 0.


What does it do?

Well you may have heard about Higgs field giving mass to matter. This is partially true since when particle interacts with Higgs field they are kind of slowed so they do not travel at the speed of light. Some particles interact more than others like some people interact with group of people more than others because they are well known [1].

At one post I wrote about symmetries, check it out if you did not already. There is symmetry in particles. They are all the same.
What? Now this symmetry is broken, this means that there are differences between particles, thanks Higgs field! This is the most important effect of the field with the effect that while it would not change much the mass of protons and neutrons, it would change the mass of electron rapidly if it would not exist. Now the space occupied by particles as electrons is set and such a light particles need to have a lot of space around them. If you would turn off Higgs field completely, things would probably gone exploding a lot since the size of atom would increase as the space around electron needed would get bigger.

Dragallur

[1] This does not mean that all the mass is from Higgs field, most mass of neutron and proton is made up of energy m=E/c^2.

Picture

 

 

 

Various fields for dummies!

Hi,
fields? Well yes, this is probably the last post before I will write about Higgs boson. Today you will learn that everything is made up of fields and that particle is just a special vibration.


Take for example magnet, it is something totally special if you think about it. Not that it sticks to stuff but that you can feel how it wants to stick without actually touching anything, just through EMPTY SPACE!

Magnet has his magnetic field all around, that is why we can feel it from some distance and the strength decreases with distance increasing.

On the picture above you can see lines of force around magnet.
This is electromagnetism and now we know that there is electromagnetic field around all the stuff that have charge. We know that we can magnetize needle using electric current.

This field is not only around magnets but also around all things that have mass, this is called gravitational field and even that it does not sound very exciting to us, in Newtonian age it was very cool when Newton found out that there is similarity between apple falling on his head and Moon orbiting Earth!

What happens when you start to rapidly move with source of electromagnetic field? Well you create waves. If you do it well enough such waves will create light! This light then comes to you in quantum! If you do it more rapidly you will get gamma rays and if you do it less rapidly you will get radio waves. This is just a vibration of field.

Or when you take radioactive decay. There is neutron which somehow changes itself into proton, electron and antineutrino. This is just a change of vibration in various fields.

Now there are 4 fields if I do not count Higgs field. What physicists want to achieve is the prove that all those fields are just one field and everything is just a various vibration of it, creating the effect of gravity, electromagnetism and so on. This would be the Theory of Everything.

Dragallur

Symmetry for dummies!

Hi,
as I said, I will continue with the explanation of what I mentioned in some earlier posts. Today I will try my best to learn you what physicists mean when they say something about “symmetry”.


First of all, when you say symmetry you probably mean that it is the same on both sides.

On the next picture you have some shapes with the right and left “lines of symmetry”.
This means that you can flip them around this line and they will be exactly the same pictures.

Square has more than one line of symmetry, there are four of them [1].

This is what we think as symmetry but physicists use it in more kind of complicated way.

When somebody makes experiment with coca-cola and candy [2] it will explode. And it will explode in New York, Prague, under water, upside down if you do it properly and even in space. This is symmetry, it does not matter where you do the experiment. But it does matter what you do it with, if you would have used water instead of coca-cola, or chocolate bar you would see that there is no symmetry [2.5]! Because it is not going to work!

When we talk about particles we can say that there is a symmetry in them, for example you can have 3 quarks, labeled as Paul, Rick and Nick. It does not matter which one you will use, because all of them have the same properties! This is symmetry all quarks are same, all electrons are same and so on.

There is a symmetry in fundamental forces. For example in strong nuclear force there is symmetry in quarks and their colors [3]. It does not matter how you label one of three quarks, it can be red, green or blue.

Also charged particles are created in pairs. This means that you have to conserve the charge so if you create electron you must create positron or something else with positive charge.

Only weak nuclear interaction of all fundamental forces has special kind of symmetry. Weak force is the only force which makes difference between particles which are right and left handed.

Such a particles  are in pairs:

  • quark u ←→ quark d
  • quark c ←→ quark s
  • quark t ←→ quark b
  • electron ←→ electron neutrino
  • mion ←→ mion neutrino
  • tauon ←→ tauon neutrino

This is also called the breaking of parity.

So weak interaction breaks symmetry and behaves differently with right and left handed particles while other forces do not do this, take for example gravity, everything is attracted by it and it does not matter if it is quark u or quark d.

Of course those particles are diametrically different their mass varies a lot, but this is only because of what is called: Higgs field, and I am going to talk about it another time.

Dragallur


 

[1] Star has 5 lines of symmetry, triangle has 3 and arrow only 1.
[2] I do not know if it is in English mentos.
[2.5] This is also called “broken symmetry” if it would not be broken, in this analogy anything would work as the mentos candy and there would be no difference between coca-cola and oil.
[3] Quarks have colors as I mentioned in last post and also in post about strong nuclear force.
[4] Maybe you remember from chemistry how you were filling the orbitals with pairs of electrons: ↑↓. Those arrows mean that one electron has negative and second positive spin (but still the same value: 1/2  .. -1/2)

The Standard Model for dummies!

Hi,
last time I talked about some stuff like dark matter (1 & 2), dark energy and I did not explain a lot of things which I mentioned and this time I will talk about Standard Model.


Standard model or Standard model of particles and interaction is the model of all observed and proved particles.

The next picture shows how it looks like, you could say that it is the “modern” periodic table or some kind of holy grail of physics.

So in this standard model you have particles that make up everything we know [1].

There are four main groups which are sorted by the forces they interact with.

All of those particles interact with gravity. Quarks also interact through strong nuclear force while leptons do not interact that way, also all of them have whole numbers for charge.

The red part has inside particles which are what is called “force carriers” they carry the fundamental forces with graviton excluded because he is not proven yet.

The most mysterious is the yellow part with only Higgs boson inside, I will make sure to make a whole chapter only about it.

Quarks

Already months and months ago I made post about quarks. Here I will cut it short so, quarks are particles that made everything there is except just a little part which is made from electrons. Quarks normally group together into hadrons – protons, neutrons, pions. Quarks have charge of either +2/3 or -1/3. They also have a property called color which is not color at all and they must group together so their colors cancel into white (white) [2].

Leptons

There are three main particles called: electrons, muons and tauons. Only electrons are actually somewhere while we can create other in the particle accelerator.

All of those have -1 charge but there are other particles called neutrinos. Electrons, muons and tauons all have their neutrino.

I already wrote about neutrinos but they are actually extremely light particles sometimes called “ghost” particles because they can easily go through whole planet Earth without touching anything. They are also electrically neutral.

Force carriers

Gluons are particles that are mass less and they carry the strong nuclear force.
Photons are also mass less and they carry electromagnetism.
Gauge bosons (W+- and Z) carry weak nuclear force.

Most of those particles have mass and that is because of Higgs boson, but that is whole new story which I will have to start with symmetries and fields, stay tuned.

Also main difference between force carriers and everything else is that they do not need any space to exist, there can be millions of them at one spot while only one lepton or quark.

Dragallur


 

[1] I do not talk about dark matter which I mentioned in earlier posts. WIMPs are not here since they do not belong into standard model, those are particles beyond the model even if they exist.

[2] Quarks have 3 basic colors: Red, Green and Blue but there are of course anti quarks which have just opposite colors: Antired, Antigreen and antiblue.

The riddle of DARK MATTER! (Part 2)

Hi,
about three days ago I was asked by the writer of “Oopsmymistake” to update about dark matter, so today I decided to write something more about it, here you go.


Last time I talked about dark matter as stuff that fills about 25% of all matter in whole Universe but we can not feel it and the only way to observe it is by its gravitational effect, for example it is extremely important in whole galaxies.


Now there are some things that I did not mention because actually there are more things that we can deduce from its behavior.

As I said, it is assumed that dark matter is composed of new kind of particle/s beyond standard model.

Lets assume that this is right, now this particle does not react much as we know, it has to be electrically neutral, otherwise it would react through electromagnetism and we would be able to observe the photons which would come out of the interaction.

Also dark matter still exists which means that it has to have half life at least the age of Universe (top and bottom quarks for example do not form anything because simply they are not here, they have too small half life).

We know that it does not interact much, otherwise it would concentrate in the middle of galaxies and not all around. So dark matter can not interact via strong nuclear force.

Now this kind of hypothetical particle is called WIMPWeekly Interacting Massive Particle.

It is assumed that the mass of such WIMP is about 10-1,000 GeV which is roughly around Higgs boson and other bosons like W and Z.

The amount of WIMPs with such a energy almost perfectly corresponds to the real amount of dark matter. Also model of super-symmetry predicts such particle with the properties we know now. It is definitely more complicated but it is called the WIMP miracle, while it could be just coincidence.

Scientists think that with this model WIMPs should interact with Higgs boson which would create something we call: “The Higgs portal” because Higgs boson would be the particle through which we would be able to observe whole dark universe (the portal between standard model and dark matter).

Of course particle physicists designed special detectors to detect WIMPs. There are two main way to do that, first is cryogenic, which is the detection of heat made by WIMP interacting with some super cooled element and the second one is to measure flash of light during interaction of WIMP and liquid xenon or argon. Such detectors are buried deep under Earth so that normal radiation does not disturb it.

Approximately in the volume of cup of coffee is always one WIMP and it is assumed that they travel at the speed of hundreds of kilometers per second, which means billions of them whizzing through you every second. Also about 10 interactions of WIMPs happen every year with atoms in your body (this is kind of similar to neutrinos).

Dragallur

PS: if you did not understand some terms I will mention them in next posts: Standard Model, Higgs boson and so on..

 

 

Conservation laws of physics

Hi,
today I want to talk about conservation laws of physics, at least some which I know about since there are just lot of them. Probably during your middle school/high school you have already encountered them. In chemistry when you have some reaction, for example:

Li + H2SO4—> Li(SO4)­ + H2

This could seem good but WordPress does not let me write upper index and (SO4) is -II which is by rule transfered to lithium —> Li2(SO4)


If you ever saw this in school you may remember that now you need to add something since if we count there are two lithium atoms coming from the reaction while only one was there before, we have violated the law of conservation of matter, mass and probably many other laws.
It should go like this:

2Li + H2SO4—> Li2(SO4)­ + H2

Now there is equal amount of stuff on both sides of equation, only thing that happened was that those atoms changed their place.

Neutron decayimg_lrg/virtual_w.jpg not found

To see some laws of conservation we can write up the neutron decay during radioactive decay:

Neutron(0) —> Proton(+) + Electron (-) + anti-neutrino(0)

There is conservation of electric charge, we can test it: neutron has charge exactly 0. Proton has positive charge and electron has exactly the same charge but it is negative, when you put this together it is exactly zero. There is also anti-neutrino but it has charge zero too, so as you can see it does not violate the conservation of electric charge (I am not saying it is right, I am just saying that one law was not violated).

So as you can see from this rule, it may seem that this anti-neutrino thing was not necessary at all, but there are other laws of conservation which would be violated without this tiny particle.

Also here the conservation of quarks is not violated, there are three coming in and three coming out.

Leptons are particles that are not affected by strong nuclear force, those are electrons, mions, tauons and all types of neutrinos.

There is conservation of leptons, there is none coming in the reaction and two are coming out.. hmm
Electron is one lepton while anti-neutrino is anti-lepton which means that they will cancel out and there is zero of leptons in whole reaction, kind of.

So those are some basic laws of conservation but I read that there could be some special circumstances under which the amount of leptons or quarks could change.. look at the amount of matter in the Universe, it is much greater than the amount of anti-matter maybe this is such a case.

Still the most important law is the conservation of energy. Energy or mass since as Einstein’s equation says: E=mc2  —> mass is just different form of energy.

Neutron has little higher mass than proton, this little mass left is the mass which is than transferred to create electron and anti-neutrino.


At last I was very curious how does it work with photon.
Everyone knows that photon has 0 mass and that is why he is able to travel at the speed of light.

E=mc2
E=0*c2
E=0

What? So photon does not have energy or what?  (c2=E/m … c2=E/0 (Universe just exploded))

The problem here is that E=mc2 works only for objects that are not moving, that are on one place which photon is not.

The full equation goes like this:
E^{2}=p^{2} c^{2} + m^{2} c^{4}.P is the magnitude of the momentum of vector p.

\boldsymbol{p}=\hbar\boldsymbol{k},Where ħ is the reduced Planck constant and k is the wave vector which is:
k=2π/λ

Where λ is the wavelength of photon!! Finally we got to something which is understandable for me.

Dragallur

PS: I tried to get to some normal value using wavelength of orange light but I was not able to get something normal so I will update with new post when I will know what I did wrong.

Pictures from Planck constant page and neutron decay page

How does particle accelerator work?

Hi,
so as I continue with the book I am reading right now about particle physics I will write about the basics behind particle accelerators.


There are several types of accelerators, they can be divided into groups by either the energy they can create or what kind of particles they are colliding, some accelerators even do not have this circle but they rather just hit some big target.

Inside accelerator you will surely have some great detector which is going to collect the data for you. In Large Hadron Collider (LHC) in CERN there are two main detectors: ATLAS and CMS. There are two so you can compare their results.

Those detectors are huge, ATLAS has 21 meters in diameter.
Then there is the tube in which you have got those particles running. In LHC there are protons in both direction. Those protons are taken from little bottle with hydrogen, this bottle would serve for billions of years because there are 10^27 particles inside.

When you take these particles you will speed them up. The particles in LHC those are protons are separated to groups. Between each group is seven meters of vacuum. In each of those clouds of protons are 100 billions of protons. This cloud can get thin as 1% of millimeter right before collision.

Protons are all positively charged so it is hard to keep them in the cloud. Because of their charge, you can speed them up using magnets. To get the top speed you have to use extremely strong magnets, which means electromagnets [1]. Those magnets will speed the particles to 99.999996% of speed of light, so obviously that is where theory of relativity comes to role, for example those particles are not spheres but rather pies because of their huge speeds — effects of relativity.

After you speed up those particles you are going to collide them. This happens at the detectors which are going to measure all the stuff that is flying away from the collision. You may identify particles by their direction of traveling, by this you may know their charge. Also how deep they were able to fly. Mions for example have longer life times than most other particles so they are able to fly through the accelerator, while bosons w and z or tauon have such a low life time that they wont fly very far and most of the time you are going to observe their products rather that those particles alone.

Dragallur

[1] Electromagnets are magnets powered by electricity because when you have electricity, it creates (electro)magnetic field. This gets stronger the stronger is the current. In particle accelerators it can get so strong that the magnets would melt at a moment because of friction with electrons, that is why they must be cooled to little over absolute zero, using liquid helium.

Only picture

Superconducting Super Collider

Hi,
so yesterday I was in Prague, the capital city of Czech Republic, because of some serious business. When I was waiting on the train station I went to bookstore there and bought really cool book, it is called The Particle at the End of the Universe, by Sean Carroll (By this particle author means Higgs boson). So, I already read 80 pages and now I want to make post about Superconducting Super Collider or SSC.


This book is about Higgs boson, which is particle I will write about some other time. Anyway it was discovered in Large Hadron Collider but there is whole history of other particle accelerators before this one.
Today lets see why SSC was never build.


Ssc mdl.JPGThe most important thing about particle accelerators is their power they can create. LHC which is the strongest on the Earth right now is able to create force of 13 TeV (tera electron volts.) At the same time this may sound powerful and weak.

1 TeV is around the energy of flying mosquito. Well that does not sound like it is much but the other thing is that LHC is able to make 13 TeV and at the same time give this energy to only one proton. When LHC is active, there may be billions of protons flying with this energy, when you add it up it may be as much as the energy of whole locomotive.

But SSC was planned to be even stronger so that it would be able to reveal even more energetic things. It was planned to be about 40 TeV strong which is quite mind blowing.

In the year of 1987 president Reagan accepted the construction of SSC. Then the place to build it had to be found.
Such a place must be geologically inactive, there must be no floods and so on. Of course all most of the states (43) wanted to have it in their city. Finally place called Waxahachie in Texas was accepted as the most safe one (it is located bit south from Dallas).

It was planned to be 87 kilometers long and activated in the year of 1996. First it was thought that it would cost 4.4 billions of dollars, but soon afterward the price rose to 12 billions of dollars. At the same time huge project needed money: ISS (50 billions of dollars, later it rose to over 100 billions of dollars).

When there were 2 billions already invested, it was decided that it was not worth it. Reasons for this were that it was poorly leaded, with prices that were underestimated all the time and so on.

This had some serious causes, like lots of particle physicists were without work. The area was then sold to guy who wanted to create super protected area for computer data, but he fell on the ice and died. Luckily USA decided that they will donate some money to LHC (particle accelerator in CERN) which was activated in the year of 2008.

Dragallur

1st picture