The universe is all things.
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>Why all of a suddenly did the big bang occur,
A thing can not come from no thing, 
action is reaction and requires cause.
Time did not begin;
the universe is eternal, it has always been.
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>Is it infinite? 
It seems to be unless you are omniscient and quantify all things.
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>Surely the universe is not infinite,
You can not prove that unless you are God.
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>there must be some external influence to allow atoms to congrugate.
There is no thing outside the one thing which is all things( uni-verse).
If it exists, it is in the universe.
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>what is at the edge of the universe 
>some sort of plasma field holding it together.
You are confusing the universe with the known universe;
that is a |---|  --|--  |--|  mistake, common too.
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