as for starters in cosmology i have worked the following short explanation
imagine 2 dimentional creatures living on a surface of a baloon and you are a god of that baloon universe in the sence that you inflate it more and more so that baloon gets bigger and bigger. The surface of the baloon has no edge (like earth has no edge - anywhere you travel you will find no edge of earth) but the surface of the baloon itself is called a boundary and this boundary size (measured in square meters) is increasing with you inflating the balloon.
Now to grasp the concept of superluminal inflation in early universe:
instead of 2 dimentional creatures on the surface of the baloon let's move to one dimentional creatures living on the surface of a circle (also called circumference , its length is 2*pi*r where r is radius of the circle). what i want to do now is to go to quantum level and think of the circumference not as thin line but as a sequence of cells (hm for example a piece of sheet u use in math classes consists of alot of small squares, so these squares i call cells, you can brush some squares to draw different figures with thick borders ).
But for purpose of circle it would be better to draw hexes instead of squares
so imagine you have a piece of paper with hexes like this one [url=http://en.wikipedia.org/wiki/Hex_(board_game)] in this image[/url]
what you do next you draw a circumference on it by brushing certain hexes.
now u can calculate the length of the circumference directly by counting of how many hexes it consists.
Now try to imagine this circumference expanding outwards from the center - you clear the hexes it consists of and brush neighbouring hexes outwards from the center - you get a new bigger circumference, you repeat the operation again and again
This expanding circumference is your universe and it is increasing - consists of more and more hexes with each step. For one dimentional creature living on this expading circumference things look like more and more new hexes appear from nowhere in between other existing hexes.
Now imagine light can travel only to the next neighbouring hex per one step of expansion. It can happen that during one step u get 2,3 more hexes between hex A and hex B on your circumference but light could only travel one hex during that step. So light from A will never reach B because too many new hexes appear in the way literally from nowhere with each step of expansion
P.S.
For advanced ones - if u have ever heard the following possible catastrophe scenario for the universe related to its indefinite expansion i can make u feel better. Namely - if universe expands indefinitely then there will be reached a point when atoms will become so big that it will be impossible for nuclea to hold the electrons and all the matter get destroyed :) hehe
there is however another possibility - with every step of expansion of the universe what happens on the quantum (cells/hexes) level is that atoms get readjusted in such a way that they take the same space(amount of cells/hexes) nomater how long we have universe expanding, so no expansion catastrophe will ever happen - in quantum world things simply do not expand
P.P.S.
it is quite possible that (like in the Conway's Life game) certain rules are defined on the hex board. And these rules are such that make information written on the hexes to move outwards from certain central hex (origin of Big Bang) and that the mass information in given hex somehow ofset that outward expansion (slows it down). So indeed it can be that there is an universal expansion force that causes universe to expand (negative pressure)
But then I have listened to other physicists say that since space is mainly black nothingness even with billions and billions of stars and galaxy's that it could be possible that the Milkey Way and M33 could eventually come together and just pass right through each other with little or no effect.
[Not that we will all live for billions of years but it does make us wonder just what would happen if our galaxy was to "collide" with say M33.
There's a chance that our Galaxy may be due to collide with M31 (AKA The Great Andromeda Nebula) in a few billion years; the light from this nearest large neighbour of ours is blue-shifted, indicating a closing radial velocity. But since we have no way of measuring the tangential velocity (proper motion) of so distant an object, there's no telling whether the galaxies will actually come close enough to interact with each other or just 'pass like ships in the night'.
as for starters in cosmology
)
as for starters in cosmology i have worked the following short explanation
imagine 2 dimentional creatures living on a surface of a baloon and you are a god of that baloon universe in the sence that you inflate it more and more so that baloon gets bigger and bigger. The surface of the baloon has no edge (like earth has no edge - anywhere you travel you will find no edge of earth) but the surface of the baloon itself is called a boundary and this boundary size (measured in square meters) is increasing with you inflating the balloon.
Now to grasp the concept of superluminal inflation in early universe:
instead of 2 dimentional creatures on the surface of the baloon let's move to one dimentional creatures living on the surface of a circle (also called circumference , its length is 2*pi*r where r is radius of the circle). what i want to do now is to go to quantum level and think of the circumference not as thin line but as a sequence of cells (hm for example a piece of sheet u use in math classes consists of alot of small squares, so these squares i call cells, you can brush some squares to draw different figures with thick borders ).
But for purpose of circle it would be better to draw hexes instead of squares
so imagine you have a piece of paper with hexes like this one [url=http://en.wikipedia.org/wiki/Hex_(board_game)] in this image[/url]
what you do next you draw a circumference on it by brushing certain hexes.
now u can calculate the length of the circumference directly by counting of how many hexes it consists.
Now try to imagine this circumference expanding outwards from the center - you clear the hexes it consists of and brush neighbouring hexes outwards from the center - you get a new bigger circumference, you repeat the operation again and again
This expanding circumference is your universe and it is increasing - consists of more and more hexes with each step. For one dimentional creature living on this expading circumference things look like more and more new hexes appear from nowhere in between other existing hexes.
Now imagine light can travel only to the next neighbouring hex per one step of expansion. It can happen that during one step u get 2,3 more hexes between hex A and hex B on your circumference but light could only travel one hex during that step. So light from A will never reach B because too many new hexes appear in the way literally from nowhere with each step of expansion
P.S.
For advanced ones - if u have ever heard the following possible catastrophe scenario for the universe related to its indefinite expansion i can make u feel better. Namely - if universe expands indefinitely then there will be reached a point when atoms will become so big that it will be impossible for nuclea to hold the electrons and all the matter get destroyed :) hehe
there is however another possibility - with every step of expansion of the universe what happens on the quantum (cells/hexes) level is that atoms get readjusted in such a way that they take the same space(amount of cells/hexes) nomater how long we have universe expanding, so no expansion catastrophe will ever happen - in quantum world things simply do not expand
P.P.S.
it is quite possible that (like in the Conway's Life game) certain rules are defined on the hex board. And these rules are such that make information written on the hexes to move outwards from certain central hex (origin of Big Bang) and that the mass information in given hex somehow ofset that outward expansion (slows it down). So indeed it can be that there is an universal expansion force that causes universe to expand (negative pressure)
Not that we will all live for
)
Not that we will all live for billions of years but it does make us wonder just what would happen if our galaxy was to "collide" with say M33.
The Andromeda Observatory
But then I have listened to other physicists say that since space is mainly black nothingness even with billions and billions of stars and galaxy's that it could be possible that the Milkey Way and M33 could eventually come together and just pass right through each other with little or no effect.
I guess we will just have to wait and see
The Hubble telescope imaged
)
The Hubble telescope imaged this in '97 (click it for the accompanying text press release):
Also from Hubble, some galactic collisions are how quasars are born:
RE: [Not that we will all
)
There's a chance that our Galaxy may be due to collide with M31 (AKA The Great Andromeda Nebula) in a few billion years; the light from this nearest large neighbour of ours is blue-shifted, indicating a closing radial velocity. But since we have no way of measuring the tangential velocity (proper motion) of so distant an object, there's no telling whether the galaxies will actually come close enough to interact with each other or just 'pass like ships in the night'.