The last blog concluded only one second after the big bang or the birth of our universe. At this moment, the universe is unrecognizable. No light has yet permeated the darkness, the fundamental concepts of physics are yet to be created, and the universe is extremely hot, dense, and expanding at an incredibly fast rate. HERE is an extremely fascinating cite that I find going into a more depth view relating to the expansion of the universe. I will cover this expansion more in future blogs.
Now let’s jump ahead roughly three minutes after the big bang during what is known as the big bang nucleosynthesis. At this point during the birth of the universe, the temperature has cooled down to 1 billion Kelvin, (still extremely hot if you ask me), and the density has decreased to around the same density as air. The fundamental laws of physics such as gravitational pull was adopted by the universe as well, causing deuterium (a stable isotope of hydrogen) and the first helium atoms to form.
At this point, the universe will stay in the state created from the big bang nucleosynthesis for roughly 379,000 years, (a lot longer than one second). Now something breathtaking takes place. The universe cools down to a little over 3000 Kelvin when the combination of protons and elections form hydrogen atoms and release radiation that separates from matter to create Cosmic Microwave Background (CMB) otherwise known as the first light in the universe.
One interesting fact is that for humanity, the CMB can be seen at approximately 13.8 billion light years in every direction. This is the extent of our observable universe, the key word is observable, as well as the age of our universe. The CMB however is estimated to be about 46 billion light years away from the center of the observable universe.
At our current point in our journey of looking into the history at our universe, we are still in the middle of the birth of our universe. At this time the universe was still forming as light began to spread throughout the darkness and both hydrogen and helium atoms were forming. It seems nearly impossible to imagine our galaxy containing galaxies, solar systems, stars, planets, black holes, and even the beautiful miracle of life emerging from such a foreign land.
Never stop questioning.
Here is both a VIDEO and a WEBSITE that dives into a more in-depth analysis about the birth of our universe!
If you were also confused about why humanity can actually see the arrival of CMB at 13.8 billion light years away while CMB is estimated to be about 42 light years away from the center of the observable universe you can read more here!
Let’s take a minute to pause and recap since the last paragraph may have sparked some questions. The reason we are able to observe the birth of CMB 13.8 billion light years out into space involves taking the speed of light into account. Similar to how looking at a star only reveals what the star looks like in the past since it has taken time for the light to travel to earth, the beginning of CMB is able to be observed 13.8 billion light years away because that is roughly how long ago are universe was born and how long it has taken the light to travel to earth.
We can see CMB 13.8 billion light years away, but CMB is speculated to be around 46 billion light years away from the center of the observable universe. This rather puzzling statement deals with the fact that humanity can only see 13.8 billion light years in every direction because the light past this point has not yet had time to travel to earth, however, the universe is expanding. When the first light of CMB was emitted to earth it was 13.8 billion light years away, but since this time the distance has expanded to 46 billion light years away that we just cannot observe at this moment. With this knowledge, we can assume that the observable universe is about 92 billion light years in diameter while the size of the actual universe is at the moment unable to be determined.
I find it a bit odd how you never once reference time in this. You talk about the CMB being so and so far away, but the reason it is so far away is because it is actually so far back in the past that it takes that much distance for us to be able to see (because distance is time when it comes to the study of space). There will never be a time when we can observe the CMB/the waves from it will be short enough for it because it was so long ago, (we were actually a part of it – and are a part of it for anyone on the other side of the world/big bang/however you want to call the collection of galaxies). For science people this may be pretty well-known knowledge, but I know a lot of people don’t know you can look in the past by looking at something from farther away.