# 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 ðŸ˜€ . 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 ðŸ˜€ .

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.

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