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Offline tony6789

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Big Bang
« on: 26/01/2006 18:50:13 »
the theory of the big bang is a bit fuzzy, can any one help clear it for me?


 

Offline DoctorBeaver

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Re: Big Bang
« Reply #1 on: 26/01/2006 19:00:07 »
I think it was Douglas Adams who described it thus:-

First there was nothing, which exploded. Then it got big - very big.

 

Offline Soul Surfer

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Re: Big Bang
« Reply #2 on: 26/01/2006 20:07:05 »


That IS quite a good simple description but if you want to start to understand what has been going on is to thing about it backwards because after all that's the way the scientists worked it out.

It is a long story and you should look up some references but you will get the same old stuff that you have probably read already so maybe you would like a new look at it so here are a few snapshots of critical times in the early life of our universe.


Simplest bit to understand was probably the time when the cosmic microwave background was generated when the universe was a hot plasma of hydrogen and helium with a tiny bit of duterium. helium three amd lithium at about the temperature of the surface of a star with all the electrons batting around like mad and totally opaque to visible light when it suddenly cooled down enough for the electrons to combine with the protons and there was a brilliant flash of light and the universe became transparent.  we can still see that flash today as the cosmic microwave background.

The bit of universe that we can see today was probably only a few hundred thousand light years across and was at a few thousand degrees K  and the density similar to the earth's atmosphere.  after that stars formed and blew up violently some creating black holes which started to collect material to be the centres of galaxies until we got the cool.  we know the compsition of this early gas quite accurately because we can stil measure it in very old small staers today becose small stars could have lasted all the way from then to now (and much longer still!).

Back in the 1950's Fred Hoyle looked back a bit further and used measurements in nuclear physics to show how before that time when the universe we can see was only s few light minutes across (about the size of the earth's orbit round the sun and everything was at the temperature and density of the centre of a star (a few million degrees K)  the protons and neutrons combined to form these elements in precisely the amounts expected given the time available for them to form.  If it had been any slower most of the hydrogen would have been turned into helium which is one of the most stable nucleii  and it would be very difficult to form stars.

Going back to when the size of the universe was about as big as the moon's orbit around the earth we find a period when temperatures and pressures were like those found in the cenre of neutron stars when the quark gluon plasma formed itself into protons and neutrons and most of the matter and antimatter was anihillated to leave the small residue of matter ant the vast preponderence of radiation that we now see in the universe.

Before that we don't really know but it is a long way to where quantum gravity operated and the whole of our universe was the size of an orange.

Learn, create, test and tell
evolution rules in all things
God says so!
 

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Re: Big Bang
« Reply #2 on: 26/01/2006 20:07:05 »

 

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