About 99.9%+ of the ‘stuff’ that makes up the universe is plasma, the fourth state of matter.
No, not quite.
The universe was completely in plasma state, only in the first 377,000 years after the Big Bang, meaning prior to the Recombination Epoch.
Before the Recombination Epoch, electrons wouldn’t bond with atoms, because the temperature were very high, so electron-less atoms were all ionized.
So while atoms remained in plasma state, the universe was not only hot, it was also opaque and photons couldn’t move freely in space, because the heat made photons to be re-aborbed by the plasma.
The
Recombination Epoch (RcE) was when the electrons were bonded to the atomic nuclei, causing the atoms to become electrically neutral for the first time.
This bonding event during RcE, caused the universe to be not entirely plasma, and the universe became transparent and cooler than all other earlier epochs. The bonding also cause photons to decouple and moving freely through space, which left residual heat signature that are detectable, which you might know (or might not know, depending if you done your research on the BB model) as CMBR (Cosmic Microwave Background Radiation).
CMBR was predicted 21 years after Lemaître published his hypothesis on the expanding universe model (1927), called Hypothesis of Primeval Atom; a team of physicists in 1948:
- Alpher and Herman predicted about CMBR,
- while Gamow and Alpher wrote about Big Bang Nucleosynthesis (BBN), which explain how atom nucleus around protons and neutrons.
BBN would have occurred before CMBR, therefore a epoch before Recombination Epoch; BBN started 10 seconds after the Big Bang and lasted for 20 minutes.
Like, I said earlier, these atomic nuclei weren’t bonded with electrons, so the earliest elements - hydrogen, deuterium, helium and lithium - were all ionized.
So for approximately 377,000 years, the whole universe was in plasma state. The Recombination Epoch changed the state of the universe, and the first photons could travel freely in mostly non-plasma universe, as cosmic background radiation (CBR).
CMBR was first discovered by Arno Penzias and Robert Wilson in 1964, and since then other radio telescopes could detect CMBR, including space telescopes like COBE, WMAP and Planck probe, mapping the earliest universe.
Plasma still exist throughout the universe timeline after the Recombination Epoch, mostly as H II regions, which comprised of Giant Molecular Clouds of most ionized gases, especially hydrogen atoms. It is these regions in space that helped form most stars. The stars themselves are mostly made out of plasma of hydrogen, eg the surface, the outer layers of the stars, and even the core.
Anyway, the universe was only entirely in plasma state PRIOR TO the Recombination Epoch.
Did any of that make sense?