Theory of relativity

Spooky action at a distance

Hi,
maybe you have already heard it.

“spukhafte Fernwirkung” or “spooky action at a distance” – Albert Einstein

what is it? Are we able to transmit information faster than light using it?

Spooky action at a distance or also quantum entanglement. This is very famous phenomenon which seems to allow information to travel faster than light, luckily not, otherwise we would have to throw all our physical theories to trash (or maybe it would benefit, who knows).

Particles have spin as I have shown countless times in posts about standard model or about particles and so on. They have also other properties which has to do with quantum entanglement.

What experiments shown was that when independently measure two photons for example the results about their attributes are correlated. This is indeed spooky because it does not matter how far away those particles are but always the result will somewhat be similar.

This cartoon helps explain the idea of "entangled particles."

The picture above from NASA page well explains how this works. The people there are detectors called superconducting nanowire single photon detectors which are cooled to be superconductive and when photon hits the wire it changes the resistance in the wire to some higher value so you can record the event.

Why does not this break the rules of speed of light? Because there is actually no data transmitted. You can not use it to communicate since the results are random anyway. And when you know your result you also know the result anywhere in the Universe, that does not matter because it was random.

I will just repeat: you need pair of entangled particles, for example laser beam can create photons that when they go through crystal and they split, they become entangled, measuring one particle will influence the other.

Einstein thought that this is because the particles contain what is called “hidden information”. That when they are created at one point in the crystal from the laser beam for example, that they make their “secret plans” on how their spin will work out when they are measured, which would not need any faster than light travel. In this video, Derek Müller shows the experiment of Bell that shows that there is no “hidden information” and how the measurements work, because what you can do is to measure the spin of particle in various angles which changes the probability of the particle to have that kind of spin.

Dragallur

 

 

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Space NEWS #9 (Gravitational waves detected!)

Hi,
those news are extremely important for modern science, lets just see what is it about.

So today, 11.2.2016 gravitational waves were for the first time detected directly. I already wrote post about gravitational waves here, but anyway in short those are the ripples in space-time made by object accelerating through space-time. Such gravitational waves were predicted by Einstein in his theory of relativity but it took a long time to detect them.

Why? Well gravity is very weak force compared to other fundamental forces so there must be a great of source of so we are able to detect those waves.

This time the source here were two merging black holes. All this information is important since they are black holes which means that they are heavy (36 and 29 solar masses) and also they are merging which means that this acceleration is pretty huge when they rotate towards each other. They merged a black hole of 62 solar masses, the missing mass was converted to gravitational waves, not kidding.

As Phil Plait writes:

And the amount of energy is staggering: This single event released as much energy as the Sun does in 15 trillion years.

How did scientists find this out?

On this video you can watch how it works, anyway here you go if you do not like links:

There is a laser in closed tube. This laser fires hitting glass which splits it on two parts with one beam going in the right angle to the other. Both hit mirrors which are hundreds of meters away. The beams bounce back hitting the mirror which means that they come together. Normally their wavelength will cancel out:

Above the red line is the wave that when everything is normal is canceled out (it is straight line) but when gravitational wave passes one mirror will move a little bit so the light will not cancel but rather go through, towards detector. Here you go, you have just found a gravitational wave!

Dragallur

Gif from here.

Solar sails

Hi,
have you ever wanted to be space pirate? To just fly through Universe close to speed of light and sometimes stop on some planet to steel some stuff? Well now, your space craft can even look like a ship, with huge sail!

Solar sails are sails like any ordinary sails. They even use wind, wind made of photons!

On the picture above, you can see IKAROS spaceprobe, the first succesful probe to use solar sails.

Those solar sails are powered by nothing more than the electromagnetic radiation coming from the Sun. It then pushes the probe because of photon’s momentum[1].

But photon has no momentum!

Yes according to Newton’s mechanics it should not have a momentum because it has no mass.

p=mv

p is momentum, m is mass and v is velocity (speed).
If you would use this you would get that photon does not move and it does not have momentum but if you use theory of relativity as I already showed in the post about conservation laws you will get some real value, using what is called “relativistic mass” which is not zero for photon.

The IKAROS’s sail was 20 meters on diagonal and most of it was 7.5 µm thick so it was very light.

Whole probe had 315 kg while the sails had only 2 kg. This is about average mass for probes since New Horizons had about 450 kg while Jason-3 about 250 kg.

The pressure of the solar wind from Sun was 1.12 milli newton and it was able to gain velocity of even 400 m/s or 1440 km/h.

This method is not much useful for fast speedup and also for deep space travel since the radiation decreases with squared distance, but still you can be a local pirate.

Dragallur

 

[1] The photon’s momentum is transfered to the solar sail and because of conservation of momentum the sail must be pushed a little bit while the photon bounces away, this is the same effect as with a shooting rifle. When you shoot the bullet goes forward while the rifle backwards with the same momentum.

2nd picture
1st picture

 

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

Observing Supernova

Hi,
so what I just found was very very interesting and it is about observing of Supernovas which are those exploding stars or white dwarfs.

The problem with observation of these very bright objects is that first of all there is not much of them and second, it is extremely hard to catch the start of the explosion so we do not have much data about it.

This problem seems to have really awesome solution that is based on nothing else than Einstein’s gravitational lensing.

Gravitational lensing is effect of very massive thing like black hole or galaxy or even galaxy cluster. It can increase the amount of light coming to us or bend the light. So actually when you are looking to star right next to Sun it may appear on different spot than it actually is!

Actually I am pretty sorry but not only that you see everything in past but you see it actually on the wrong place, DAMN! (And if you run it is bluer).

So because of this light bending it can happen that the light even comes from different directions.

The picture above shows how we could observe one event (one supernova type Ia) four times in different time intervals just because it was in huge super cluster which bend the light from supernova so much that it came to us in different directions.

This particular observation was done only by accident when one astronomer was looking at pictures from Hubble and he saw it.

Dragallur

Supernova picture
Gravitational bending

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