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Old Feb 7th 2016, 02:30 PM   #31
MBW
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I admit I don't really understand, proper study of the big-bang requires maths skills I don't possess.

In the original singularity of the big-bang we have an entire universe worth of energy in a single point.
This can surely not be a stable situation.
This energy creates the universe and starts it expanding.
As the universe expands, random happenstances cause local variations in density.
At certain locations the energy levels become just right to create particles, including protons and electrons.
However, even if these protons and electrons come close enough to bind into atoms, there are far too many gamma rays (etc) flying about the early universe and within a pico-second (or less) the nascent atom is ripped apart.
It is only when the universe has expanded enough for the surrounding energy to be calm enough to leave the protons and electrons alone for a while that the protons and electrons can properly start to form atoms.
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Old Aug 28th 2017, 03:53 PM   #32
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Originally Posted by ChipB View Post
Actually a black hole consists of a singularity which is infinitely dense,
Actually it couldnt have been infinitely dense. density is mass per unit volume. If the singularity had no volume its density would be undefined not infinite because any number divided by zero is undefined. If the singularity had any size at all its density by definition could not be infinite.
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Old Aug 28th 2017, 04:03 PM   #33
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Originally Posted by jlr01 View Post
Actually it couldnt have been infinitely dense. density is mass per unit volume. If the singularity had no volume its density would be undefined not infinite because any number divided by zero is undefined. If the singularity had any size at all its density by definition could not be infinite.
You're quite right. When things get to be that small quantum effects become important and there's not as yet a fully developed and widely accepted quantum theory of gravity.

And when something is a point its best to leave the notion of density out if it. After all we don't speak of the energy density of sub atomic particles yet we believe that are point like. As such there's no meaning given to mass density. Mass density is a concept that was created to speak of continuous media, not point objects.
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