The riddle of DARK ENERGY!

Hi,
today I will write about dark energy since last time I briefly covered the dark matter. The dark energy is even more unknown than the dark matter, let’s see why.

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As I said before, there is about 70% of dark energy in the Universe of all the energy that there is, rest belongs to dark matter and tiny bit to normal matter.

Dark energy has to do a lot with expansion of Universe which was find out last century by Edwin Hubble. He found out that the Universe is expanding and right now we even know that the rate of expanding even increases (The Big Rip scenario).

Why? Because there is something called dark energy and we know that it works kind of like “anti-gravity” this could be misleading since the gravity is still there so it is also said that it has “negative” pressure.

Dark energy is everywhere at the same amount and as the space is expanding there is more of it created. This does not violate conservation of energy since the force of gravity decreases at the same time with the distance increasing. I guess that this is why the expansion increases.

There are four theories which I found about the dark energy, the first one is that dark energy is not a thing but rather property of empty space and empty space is expanding and as the expansion increases so does the rate.

Second idea is the idea of cosmological constant which was made by Einstein. At the start it was constant which would be zero so that space would be static but as Hubble found out Universe is expanding so the cosmological constant, which is kind of property of space must be higher than zero. Now lot of cosmologists are trying to measure this constant, this is a big problem since when we try to calculate it, it goes with orders of magnitude away from what we can observe and it is simply wrong.

Or also virtual particles popping in and out of existence in space could give energy to this dark energy.

Simply we do not know much about it but we know that it must exist in some kind of form.

Dragallur

 

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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)

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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 decay

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.

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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:
P is the magnitude of the momentum of vector p.

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

Eclipse, bus ride and theory of relativity

Hi guys!
It is two days since eclipse of sun.
First of all I will just remind you what eclipse is.
So, it is shadow of moon, because of its rare position between sun and you.
Imagine having lamp. It is your sun. Take your hand (moon) and move it between you and lamp. That is how eclipse works.

There few kinds of it. There is full eclipse.
This one on the left is full eclipse from year of 1999. Picture was taken in France. For full eclipse you usually need to go to some specific place which is calculated by some math quys 😀 . Because that is the only position you can change… you can not change position of sun, moon or earth but you can travel yourself.

Here on left is picture of solar eclipse. You can see that shadow of moon is not visible everywhere… only on very small spot (about 250km^2) is full shadow.
There are lots of things that have to work together if you want for example to have full solar eclipse visible from window of your house.
Because moon is 400x smaller than Sun, Sun has to be 400x further away. At same point your house has to point exactly towards sun and at the same moment moon at right distance has to orbit across your point of view when you are looking at sun.
Well that wont happen 😀 .

Because moon is slowly going away from earth and sun is gaining volume, last full solar eclipse we will be able to see will be 600,000,000 years from now.
You can see list of eclipses on wikipedia. Next total one will be March 9 2016. But it will be somewhere in pacific ocean.

Anyway, two days ago I was in bus by the time when eclipse was seenable. Luckily i was sitting in back seat from which you can see huge part of sky. Well I forgot to take some kind of black glass so I saw it for few seconds before I was too blinded, hope nothing happened to my eyes. Anyway I am looking forward to next eclipse and I hope that you guys did see it!

Eclipse was very important when Einstein wanted proof for theory of relativity. He was predicting that as huge objects bend spacetime, light will be curved if between sun and you is some object with huge gravitional field. Actually moon has too weak gravity so you cannot really see it but when you have quasar and black hole is between quasar and you, you can see that effect of bended spacetime. It is called effect of gravitational lens. http://en.wikipedia.org/wiki/Gravitational_lens On wikipedia page you can see short video of how it looks like, it is pretty amazing.

Thank you for your likes,
Dragallur

2) Four fundamental forces: Gravitation

Gravity or gravitation is one of four fundamental forces in the universe. It is also the weakest one as I said in the last post. Unlike other forces it works on much bigger distances. And it only pushes things together.
Imagine having a planet like Earth. It has poles. South pole and north pole. We can see that Earth gravity is pretty strong, it holds us here. So if electromagnetic force is 10^40(something like that) stronger, shouldn´t be electromagnetic field of earth insanely strong? No because electromagnetism works with +(plus) and -(minus) and they will cancel out (almost). Strong and weak interaction are working only on short distances so when you are forming galaxy or star you will work only with gravity.

There are two ways of imagining gravity. (Actually there are more but those are basic)
1) Newton´s way
It says something like this: Every particle in universe attracts all other particles in universe by force which is higher when mass of particles is bigger and is lower when particles are far away each other. Its equation is F=G*(m1*m2)/r
F is force of gravity
G is gravity constant (you can find it on wikipedia)
m1,m2 are masses of your objects
r is distance of objects
2)Einstein´s way

Spacetime is bended by all particles with mass. And it works with all particles even those which are massless, like photons.
Newton´s way does not actually explain some things like orbital of Mars (so it is kind of broken).
On the left is picture of spacetime. You can also imagine your bed which is probably very soft and when you push your matress it goes down. At that point your fist is actually kind of planet, star or black hole and it atracts other stuff around. If you take a ball lay it next to your hand it will go down to center of that hole you created.
I have found awesome video on gravity so here is link: https://www.youtube.com/watch?v=MTY1Kje0yLg
You will see that all forces have some force carrier. Gravitational carrier is massless particle called graviton. It is theoretical, which means it was not detected. Scientists even think that it cannot be detected, but we can see what it does: Gravity!

Thanks for your follows,
Dragallur

P.1: http://www.aldebaran.cz/bulletin/2011_44/krivost.jpg