# What could happen to our Universe: Big Bounce

Hi,
with little break from Solar System I am returning to last post about end of our Universe. This time it is very optimistic, but we will die anyway..

Right now the Universe is expanding, it is expanding in high speeds but this theory is assuming that this process due to decreased amount of dark energy reverses at one point and everything will start to shrink back. This would heat Universe over time. About 100,000 years before big crunch space would be hotter than surface of stars which would make them cooked from outside (FUN).

Then all matter would fall into black holes and all of those black holes would fall into each other so that final singularity would be created.

Well then it could start all over again, big bang, zero expansion and big crunch. This scenario also assumes that Universe is going through infinite cycles of banging and crunching. While this is most optimistic, in the new Universe would be nothing from the one before.
Measuring of expansion of Universe does not give much points to big crunch because now it seams that expansion is speeding up. Scientists are not yet able to know why is this happening Big Bounce is still an option.

Dragallur

PS: I just lost the game… Here is post about heat death. And here about big rip.

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# Schwarzschild radius

Hi,
I know this title seems that my post will be complicated but actually it is pretty easy.

I want to return to my favourite topic: Black holes, and their size.
You probably know that inside black hole is singularity and that the edge is called event horizon. Its size is different from one black hole to another and we can use Schwarzschild  radius (SR) to count it.
Schwarzschild radius is area from which light could not escape if you pressed this mass to area of sphere with Schwarzschild radius.
Its equation is:
r=2Gm/c^2 where r is radius, G is gravitational constant, m is mass of object, c is speed of light.
Earth´s SR is 9mm and Sun´s is 3km and if you would compress mass of observable Universe you would have SR of 13,7 billions of light years and super massive black hole in the middle of Milky way has Schwarzshild radius 7,8 millions of km which is also how big is its event horizon.

Dragallur

# Dwarfs

Hi,
I had little pause but now I am coming back.
Today I want to write something about dwarfs because I found them little confusing.
We are talking about dwarfs in Universe not Tyrion.. there are six kinds:

1. Brown dwarf

Brown dwarf is the only one which is not star. It is actually extremely big planet which almost made it for the size of star. This term is used because red dwarfs already existed.
Scientist are not really sure when it comes  to the difference of planet and brown dwarf. Jupiter would have to be more than 50x larger to be brown dwarf.
2. Red dwarf

Red dwarfs are “cool” stars. For example Proxima Centauri, the closest star is red dwarf. Their mass has to be about 0.08 of Sun to 0.5 of Sun´s mass. Red dwarfs are extremely common in Milky way as most of stars are smaller than Sun. That picture shows red dwarf and it would be more orange if showed from smaller distance.
3. Yellow dwarfYellow dwarf is not really a dwarf. It is star which is about the same size like our Sun. Its temperature on the “top” is about 5000 to 6000 K.
4. Blue dwarfBlue dwarfs are kind of related to red dwarfs because they are just a stage in their live. When red dwarf uses almost all of its hydrogen it will need to equalize with gravity and for that he uses temperature which rises and from red color it will shine in blue. This stage is only hypothetical because red dwarfs lifetime is really long and this could not yet happen.
5. White dwarfWhite dwarfs are stage of all stars which wont make it to neutron stars or black holes. They are about the size of earth but much denser. From white dwarfs supernovas can explode.
6. Black dwarfBlack dwarfs are only hypothetical but it is almost sure that they will happen when time comes. They are the next stage of white dwarfs. Black dwarf should not shine anymore because it is cool. They should be also really hard to detect because of their black color.

Dragallur

# Wormholes

Hi! So what is a wormhole?
Wormhole is kind of similar to black hole.
It does have really strong gravitational field but not that much as black hole. The thing is that black hole bends space time much more than wormhole — it has singularity in the middle. Wormhole does NOT have singularity, because it does not have enough strong gravity.
When it does not have singularity it also can not have event horizont.
So what makes it a hole?
When it bends spacetime it can create tunnel from one point of universe to another through higher dimension this could be used for traveling really long distances. Black hole cannot do this because its gravity is too strong.

Now it is clear so lets move to spacetraveling through wormholes. First you can imagine it with lower dimensions which are pretty easy. So 0th dimension is pretty useless since it is just point so we will jump right for 1st dimension. It is only line, not very complicated right? You have line which 1km long. You have to get from one end to another but you dont have enough time. You will take shortcut through 2nd dimension! You will take this line and bend it to circle, so now that point which you wanted to visit is right next to you! From 2nd dimension to 3rd it is also very easy to imagine, you can actually see it above. Take a paper (that is your space) and on one edge draw point and draw same one on opposite part. Then bend this paper so those points are touching, you have been traveling faster than light! Well it is not fair, it´s like saying Usain Bolt to run 1000m and you running only 50m, quess who will win, light.
It is named wormhole because worm in apple is using 3rd dimension instead of traveling on the surface of apple.

Problem with wormholes is that higher dimensions than 4th (which is time) are only in really small scale: 10^-33 centimeters. This length is not really usable for traveling but really old wormholes could be bigger caused to expanding of universe. Another problem is their stability because they would need to have lot of “exotic” matter to last longer than moments. Last thing is that wormholes are only hypothetical, wormhole has never been observed.

Dragallur
PS: I have edited it once because there were some mistakes and it did not make any sense before.
PSS (26.11.2015): light is not 4th dimension as you can read in this post.

# What is the life cycle of stars?

Hi!
Somehow I wanted to write something from universe… not really I am still sitting in my hometown so here it is:

Well, stars (as our Sun) DO have beginning and end as you probably heard already. It can have different length.
First of all there have to be material. I mean lot of material because as you know our sun is huge. (Sun is bigger that 90% of stars)
This material comes from other stars that are dead now and theirs material probably came up from Big bang.
There are extremely large clouds that are called Molecular clouds. In them is lot of stuff and mostly H2.
If there is enough stuff at one place (it is really dense) it can make up planet which is either stony or made from gas.
If there is enough stuff it will make even larger gas planet than Jupiter or Saturn.
At that point all of this H2 will be pulled toward the center with magnificent force. That will create heat because atoms will be brushing against each other. If there is enough heat termonuclear reaction will occur which will normalize that pull of gravity and whooo! we have new born star!
Termonuclear reaction will change Hydrogen to Helium. Helium is heavier so it will go toward center and just a little bit of Hydrogen will be left on the edges. If the star is enough heavy it will start to change Helium to Carbon or Oxygen (I think). It will continue with couple of rounds until there in the middle is Lead (Pb). Than it will never be able to go forward and the life cycle will kind of end. Few more termonuclear reactions will occur (That is called red giant because it will greatly gain volume and the it will lose it) but then gravitation will win and if that star was small (even like our Sun) White Dwarf will be the END.
White dwarf is only really dense and hot piece of stuff.
If it was heavier.
Neutron star (made of only neutrons) will be the next stage. It extremely dense thing with tremendous gravitational field.
The last thing which can happen is Black hole, you can read about them in one of my first posts, they are absolutely awesome!

Dragallur
PS: if white dwarf gains again enough mass because of some stuff from space it can heavily explode into Supernova

# 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

# What are really bright objects in universe?

Today in my 3rd post I would like to tell you something about two kinds of objects (from universe) which are very bright.

First one is quasar and blazar. As far as i know they are probably same thing but from different angle of view. They are very bright and in middle of them are black holes (if you want to read something about BH then read my second post).

When stars or lot of stuff (dust) around hole starts to accelerate toward the black hole, lot of heat and radiation will be created because particles in high speed will rub againt each other. This will create massive disk around hole. That is called quasar/blazar and it can be even brighter then our own Galaxy!

Second object is Supernova.
It is created in two ways. I will try to explain only the first one because again, i dont really understand how the second works.
Anyway, imagine you have white dwarf (like our sun when it will be few billions years older). It is object which has such mass like our sun but it is big like Earth. It is shining even that termonuclear reaction does not occur anymore. After some time it will turn to black (cold) dwarf. But if this dwarf gains some mass again and heat inside core will be high enough to create another round of reaction it will violently explode! Picture on the left shows galaxy and that “little” point is actually supernova. It does not shine long time, only for weeks or months.

So those are the two bright objects in our universe. I hope i did not miss something important.
Btw. thanks to people who liked my posts, i really appreciate that.
Dragallur
PS. next time I will probably move to something on the earth!

P.1: Quasar. (2015, March 2). In Wikipedia, The Free Encyclopedia. Retrieved 12:47, March 20, 2015, from http://en.wikipedia.org/w/index.php?title=Quasar&oldid=649527988

P.2: Supernova. (2015, March 17). In Wikipedia, The Free Encyclopedia. Retrieved 12:47, March 20, 2015, from http://en.wikipedia.org/w/index.php?title=Supernova&oldid=651800657

# What are Black holes?

Hi,
this is my second post. I would like to say something about my most favourite topic: Black holes. I hope that there won´t be any mistakes so I will not go deep and more complicated stuff.

Black holes are universal objects as you probably already know. Important thing is their size. If you know something about white/black dwarfs and neutron stars you could easily get to right answer about how big are black holes.
You see I said something about dwarfs and neutron STARS. Right, stars. There are not really kind of stars but all of these three objects come from stars like our own Sun!
I will probably make another post for only stars so I will write this short. When gravitation pulls lot of dust from universe together it will have so huge gravitation (like our Sun) that termonuclear reaction will occur. (Jupiter is almost so huge that he would be another small sun if little bigger) This reaction will be able to keep star from falling into itself by gravity. But when fuel (H,He…) runs out it will crush itself under gravity. If it was small white dwarf will be next stage. (That will happen to sun). If gravity pull is very huge electrons won´t be able to hold the force and neutron star will appear (made of neutrons). If it is even larger and strong interaction won´t be enough strong black hole will born!

In black hole there is actually no force to hold it and it will fall into singularity! That is point infinitly dense and infinitly small.
Particles have gravitational pull on other particles. When there is lot of particles, gravitation is very strong and it will start to bend spacetime(P.1).

(Sun does that and stars behind seems to appear somewhere else than they are.) Black holes have such strong pull that even light can not escape, that is why they are black (no light comes to your eye).
Around black hole is event horizont. That is circle which is edge of black hole. Light circles around it. It can not escape but it wont be either sucked by hole.

Long time it was thought that black holes can not decay particles but Stephen Hawking actually came up with Hawking radiation. On this topic I will have to learn something more because I dont really understand how it works. Anyway black hole is actually radiating (lossing mass) and at one point it will explode when strong nuclear force will be again able to fight gravitation. Can happen after 10^66 years.

Surely I forgot to say something but you can ask me in comments.
Please comment this post if there are any mistakes!
Btw. I highly recommend to read The brief history of time by S. Hawking
Dragallur

p.1: Spacetime. (2015, March 5). In Wikipedia, The Free Encyclopedia. Retrieved 18:24, March 19, 2015, from http://en.wikipedia.org/w/index.php?title=Spacetime&oldid=649931558