How big was the universe during recombination?
Since the universe was about 300,000 years old at recombination, the horizon size then was about 300,000 light years.
Each atom at the surface of last scattering could only be in causal contact (and therefore in thermal equilibrium) with with other atoms within a radius of about 300,000 light years..
How hot was the universe at recombination?
The epoch at which atoms form, when the universe was at an age of 300,000 years and a temperature of around 3000 K is somewhat oxymoronically referred to as "recombination", despite the fact that electrons and nuclei had never before "combined" into atoms..
How recombination gave us the CMB radiation?
Until recombination, the universe was opaque to electromagnetic radiation due to scattering of the photons by free electrons.
As recombination occurred, the density of free electrons diminished greatly, leading to the decoupling of matter and radiation as the universe became transparent to light..
What is recombination and how did it effect the transparency of the universe?
It is commonly said that after the universe cooled enough for ionized Hydrogen to settle down into neutral Hydrogen, i.e. recombination, the universe became transparent..
Why did the universe become transparent at the time of recombination?
It is commonly said that after the universe cooled enough for ionized Hydrogen to settle down into neutral Hydrogen, i.e. recombination, the universe became transparent..
Why is the universe said to be neutral after recombination?
When the temperature of the Universe fell below a certain threshold, protons and electrons could, at last, combine together to form neutral atoms, mostly hydrogen and helium.
This event occurred about 380,000 years after the initial Big Bang, and the Universe then stayed neutral until much later..
- Recombination in the form of crossing over occurs between homologous chromosomes, in order to increase genetic diversity by changing the assortment of genes.
It does not violate independent assortment since it doesn't affect how traits and genes are actually assorted in gametes. - Recombination was the beginning of the dark age: the universe was transparent but there were not yet stars.
The freed photons traveled freely, many having no subsequent interaction with matter (thus they were free streaming), and now constitute the cosmic microwave background (CMB). - This process of particles pairing up is called "Recombination" and it occurred approximately 240,000 to 300,000 years after the Big Bang.
The Universe went from being opaque to transparent at this point.
Light had formerly been stopped from traveling freely because it would frequently scatter off the free electrons.