1. Fossil of light ( Microwave cosmic background radiation )

　Microwave cosmic background radiation is a theory that the cosmic first light ( it happened a few billion years
after big bang. ) lost temperature according to the expansion of the universe and the light became microwave and
filled the universe.
Recently the light was actually observed. The light is actually electric wave. Light and electric wave are same type of thing. It is said that light becomes electric wave when its wave length is long. ( The first observer won
Nobel prize,) It is said that the observation is the direct proof of big bang. So, almost all cosmic scholars now
believe that big bang truly happened.( Big bang is a theory that the universe was made by a big explosion. And the
explosion was named big bang.) About this theory every book of universe explains it. So I don't explain it now.
Bat I have some questions about the theory .
I'm an amateur but I wonder if big bang is a real fact. Now I'd like to write about my questions.
Question 1.
Background radiation is light, so why light can fill the universe? Light goes straight through everywhere on and on, so I think light cannot be kept in a container not like water can be kept. Even if the container is as huge as universe, why is it possible to keep the light of the first explosion in it for 13000000000 years long ?
Some books say that 100000 years after or 300000 years after the big bang ( the time is different along the books, but the latest information says it was 380000 years after the big bang #note 1.) light and water separated and light started flaying freely. ( They call this phenomenon, universal fine weather.) It might mean that at that moment, light flew far away to the other side of the universe,(#note

2) leaving slow matter. I wonder how could we see light which flew far away even if we have very progressed technology. Maybe a real time machine could do it. The fact that Microwave observation satellite, COBE observed light which was 13billion years ago, doesn't mean COBE is a time machine. Our eyes also easily can see light which started stars a few years ago or a few 100000years ago, or even we can see light of milky way which came a few million years ago, when we look up the sky at night. But it also doesn't mean our eyes are time machines.
#note 1. About the size of the universe at the moment of universal fine weather
The universe was born 380000 years ago, so we can say the radius of the universe is 380000 light years, when it expanded at the speed of light speed. It is said that at first so called inflation happened and universe expanded at the speed of super light speed, but it was for a moment, so its diameter was only about 10centimeters long, and we can ignore it, because it was so short. Now let's see, our Milky Way has the diameter of 100000 light years long. It is said that there are more than 100billion milky ways in universe. I wonder how all the milky ways were in the universe which has only 760000 light years long diameter. How crammed universe was ! It is surprising that a black hole didn't appear.
#note 2. Can we call out side of the other end of universe a universe, too?
I wonder what was it like the out side of universe when the diameter of universe was 760000 light years long. They say that the outside of universe was not universe. They, the scholars who are for big bang , say that space and time were both born at the first time at the big bang. So, they say there weren't anything at the outside of universe, time, space, or anything at all. Light could only fly in the universe which has 760000 light years long diameter, in the universe where matter ( they say there were only hydrogen and Helium at that time) filled universe heavily. Don't you wonder what happened to light which was at the outside of universe? Do you think the light ran back scarcely from the edge of universe because 0.1centimeters outside of universe, there were completely nothing. Well, the scholars simply explain that space is not straight, it is curved with theory of relativity, so, light which goes straight goes along the curve and it never goes outside of universe.