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Author Topic: Why did the Big Bang produce only hydrogen, helium, and a little lithium?  (Read 7083 times)

Offline Eric A. Taylor

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At 1 second after the big bang, every bit of mater we can see across 13.7 billion light years was contained in a volume of just 186,000 miles across. This is hard to imagine. All the stuff that would make up hundreds of billions of galaxies, each with several hundred billion stars was crammed into a space smaller than the moon's orbit around the Earth. Yet the atoms could get a little space between each other (some 380000 years later) all this pressure and heat managed to make was hydrogen, helium, and a little bit of lithium. The pressures inside stars, where heaver elements are made today are far lower than what it must have been throughout the entire universe for a long long time. What prevented all the atoms from fusing into some kind super atom. I know big atoms are unstable, and the bigger the nucleus the more unstable it is. But even if this super atom fell apart quickly shouldn't we still have a lot of heavy stuff like lead, iron, and gold?


 

Offline Soul Surfer

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There was not enough time for the atoms to fuse remember that the formation of helium releases a lot of energy and this would have given an already very rapid expansion a big boost.  if there had been lots of time  the universe would have been mostly atoms around iron in the periodic table.

The proportions of hydrogen deuterium  helium and lithium dictate quite precisely the conditions during this critical expansion period are strong evidence in favour of this model of the universe at that period because of their complex interrelations  small changes in conditions could produce large changes in the relative proportions of the various elements
 

Offline Eric A. Taylor

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What I was thinking about was the fact that for a long time after the big bang all the matter in the universe packed into a fairly small space. I know that the entire universe was quite a bit larger than 186000 miles across at +1 second after the big bang due to inflation. But all parts of the universe we can see today were inside the light cone that was only 186000 miles across 1 second after the big bang.

At that time the universe must have been far more dense than a neutron star. I imagine the universe would have been as dense as solid matter hundreds of millions of years.
 

Offline yor_on

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Dense maybe but at a very high temperature, wouldn't you say?
And at such temperatures matter won't be I believe?
A plasma of some sort maybe?
 

Offline Soul Surfer

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Your imagination does not tally with the scientific facts and it is better to study these.   Even when it was at quite an early stage the universe had an average density a great deal less than most people expect and the events took very much less time.

look up 
                 http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang
                 http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis   

  for a detailed explanation of the timing  and nucleosynthesis.

a few details

Nucleosynthesis  only happened in the period from 3 to 20 minutes when the "size" of the universe was about the size of the solar system. The  density of the universe then was around the internal density of a typical star, not a neutron star that period was much earlier and shorter.


Around 300,000 years after the start, at the time of the creation of the cosmic microwave background, the temperature was around the temperature of the surface of the sun and the density about that of the earth's atmosphere.

The reason for these low densities is that the universe is incredibly bigger and lower density than most people can imagine, even though there are a few very high density bits.

 

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