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Old Jan 11th 2016, 11:24 PM   #1
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The big bang or the big fizz?

Black holes are so compressed and densely packed with matter that not even light can escape from beyond the event horizon. How could an even more dense region of space, such as the big bang "egg" explode if larger and less dense objects (black holes) cannot?

Last edited by kiwiheretic; Jan 11th 2016 at 11:26 PM. Reason: Clarity
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Old Jan 12th 2016, 08:01 AM   #2
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Actually a black hole consists of a singularity which is infinitely dense, surrounded by a region of space where from which light cannot escape. So whatever existed at the moment of the Big Bang was not necessarily "more dense" than a black hole.

But you raise a valid point - what mechanism initiated the Big Bang? That is something that no one knows. And it may "unknowable." All we do know is that the evidence from such phenomena as Hubble's Law, the cosmic microwave background radiation, the distribution of galaxies, and the ratio of hydrogen, helium and lithium in the universe, are all consistent with the notion of the Big Bang. But no theoretical model as yet tells us anything about what the universe consisted of at precisely T=0, or "why" the Big Bang occurred.

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Old Jan 12th 2016, 08:55 AM   #3
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I would mildly disagree with ChipB that there is:
no theoretical model as yet tells us anything about what the universe consisted of at precisely T=0, or "why" the Big Bang occurred.
I have heard mention of several theoretical models being developed,
though none of them seems to have been accepted as truly compelling.

A core difficulty with studies on this topic revolves around testing any theory you might dream up.
The scientific method requires that any theory must have a sensible way to check its "success" against the other rival theories.
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Old Jan 12th 2016, 11:20 AM   #4
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Originally Posted by ChipB View Post
All we do know is that the evidence from such phenomena as Hubble's Law, the cosmic microwave background radiation, the distribution of galaxies, and the ratio of hydrogen, helium and lithium in the universe, are all consistent with the notion of the Big Bang.
How do we know the ratio of hydrogen, helium and lithium in the universe when we probably cant even see the entire universe? Are we basing it on the mineral diversity of our own planet whereas the mineral diversity of our planet seems to be radically different to the others in the solar system? How do we know we're not looking at a local phenomenon?
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Old Jan 12th 2016, 11:34 AM   #5
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Big bang production of nucleons and atoms

Have a look at this Dr Physics A video from about 20 minutes in. This is something else I am struggling with. He says that in around 20 minutes after the big bang you have nuclei but its not until 380 000 years that you have electrons. Where do they come from? Surely you cant just borrow them from the vacuum using Heisenberg's uncertainty principle. Pay day (paying it back) must have come around before now!!
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Old Jan 12th 2016, 12:09 PM   #6
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Originally Posted by kiwiheretic View Post
How do we know the ratio of hydrogen, helium and lithium in the universe when we probably cant even see the entire universe? Are we basing it on the mineral diversity of our own planet whereas the mineral diversity of our planet seems to be radically different to the others in the solar system? How do we know we're not looking at a local phenomenon?
One way is by looking at the spectra of stars, which give a pretty good indication of the elements that are in that sta. When looking at very old stars - which are less "contaminated" with heavier elements than younger stars - we see hydrogen, helium, a small amount of lithium, and virtually nothing else. Recall that elements heavier than lithium originate in stars and are distributed into the universe by novae, so a very old star would have been created prior to the synthesis of these heavier elements.
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Old Jan 12th 2016, 12:26 PM   #7
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Originally Posted by kiwiheretic View Post
...He says that in around 20 minutes after the big bang you have nuclei but its not until 380 000 years that you have electrons. Where do they come from?
It's not that electrons first came into existence at T+380K years, but rather that this was the earliest when they could bind to atomic nuclei to form atoms - prior to that time temps were too high. With all those free electrons running around it was impossible for light to propagate prior to T+380K years, hence the universe was opaque. As for electrons - the theory is that they were around essentially from the earliest epoch, along with positrons, photons, neutrinos, and antineutrinos.

There is an excellent book called "The First Three Minutes: A Modern View of the Origin of the Universe," by Stephen Weinberg which I highly recommend. It's a little dated - 1970's time frame - but the essence of what he describes is still very much in line with current thinking.

**EDIT - just checked the video, and indeed it talks not about electrons forming at T+380K years, but rather atoms forming for the first time, due to the fact that the energy density has fallen enough for electrons to be captured and no longer ionize away.

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Old Jan 12th 2016, 01:16 PM   #8
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Originally Posted by ChipB View Post

**EDIT - just checked the video, and indeed it talks not about electrons forming at T+380K years, but rather atoms forming for the first time, due to the fact that the energy density has fallen enough for electrons to be captured and no longer ionize away.
Ok, I guess I misunderstood that. But in a way that makes the problem worse!! The electrons existed but had way too much energy to orbit nuclei and therefore speeding away from them probably away from the original position of the cosmic egg at great velocity. The nuclei are heavier and have way less velocity from the initial explosion. How did they catch up to the fleeing electrons *and* get them to orbit them *and* find other atoms *and* form ionic bonds with them?? The odds to me seem to be staggeringly against.
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Old Jan 12th 2016, 01:29 PM   #9
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Originally Posted by kiwiheretic View Post
The electrons existed but had way too much energy to orbit nuclei and therefore speeding away from them probably away from the original position of the cosmic egg at great velocity.
Cosmic egg? Remember that electrons have mass, so can't "speed away" at faster than the speed of light, which is the speed with which that "egg" is expanding. So the electrons, protons, neutrons, photons, neutrinos, positrons, etc etc are all in one big essentially homogeneous soup, banging into each other over and over again. Given the extreme densities of the early universe they do a lot of banging together! And recall that electrons and protons are naturally attracted to each other - it takes energy to keep them apart. Once the energy level decayed sufficiently there would be no keeping them apart.
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Old Jan 12th 2016, 01:55 PM   #10
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Originally Posted by ChipB View Post
Given the extreme densities of the early universe they do a lot of banging together! And recall that electrons and protons are naturally attracted to each other - it takes energy to keep them apart. Once the energy level decayed sufficiently there would be no keeping them apart.
Yeah, but that would take 380000 years and I am not seeing why they are banging into each other if they have plenty of room to move within a "faster than light" growing cosmic egg shell. Incidentally we bang particles together in the LHC and as far as I am aware with energies a lot lower than those in the big bang and they split apart. Wouldn't it be more so if they were banging together in a very confined space? And yet we are supposed to have stable nuclei!!

Last edited by kiwiheretic; Jan 12th 2016 at 02:03 PM. Reason: Added LHC argument
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