Big Bang Theory and the Expanding the Universe

I read @sigmund IF THE UNIVERSE IS EXPANDING, THEN WHAT IS IT EXPANDING INTO? It was a beautiful pieces; however one key word that was not mentioned throughout the article was “the big theory”.

I would like add, I like the fisherman’s explanation to the expanding universe using stretching of an elastic band. That is a very vivid example, however if anyone tend to accept that explanation should note that the universe is not elastic, rather the rate of expansion had changed over time.

Hence, I felt the need to write. I appreciate @sigmund the permission he granted me to make my input.

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In a nutshell, @sigmund explains the actual expansion of the universe is space and not the components of space (matter). The effect of this expansion is seen from the distance been observed between matter in space (Metric of space).

Again, he pointed out that the universe is 4 dimensional wrapped in 3D space which makes it much complex at the moment to decipher.

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Some questions came while reading the article as I thought of the role of the big bang theory in all this.

What is the big bang theory?

@sigmund wrote that the cosmological principle and Copernican principle are the theories that explain the features of the universe. The Copernican principle states that

“italicNo place in the universe is preferred and that the universe has no starting point”

The universe actually had a starting point- boldsingularity. The universe was dense hot ball of gas, and at Plank’s time (10^-34s) it exploded into the universe we had today.

Physicists and Astronomy have proved that our universe had a starting point. The explosion birthed a universe. The rate of expansion was very fast at the time and temperature decreased massively from 10^32K to 10^9K and at some point expansion began to slow down.

However, about 6billion year after the big bang explosion, its speed began accelerating as a result of an unknown force, dark energy. Dark energy is far hidden from man and constitutes about 72% of universe.

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Another point raised by the @sigmund in metric expansion of space
“italicThe scale of space is constantly changing implying that the universe did not expand anything instead space changed”

“italicThe truth of the matter is that the universe is not expanding into anything, it is just expanding based on space. Space is stretching. And since the universe is everything, if there is something to expand into, then that thing is also part of the universe.”

To buttress on the above, the expansion of the universe will alter the shape of the universe considering density of the universe and its critical density value approximately, 10^-26Kg/m^3

If the density of the universe exceeds its critical density value, the universe is termed closed and a big crunch will occur that is it will collapse.

If the density of the universe less than the critical density value, the universe is termed opened and will expand forever.

If the density of the universe equals the critical density value, the universe is termed flat. It will expand, but the rate of expansion will gradually reduce to zero.

This article does not discredit @sigmund write up on expanding universe but an extension of his article.

Thanks for reading
sources
Our expanding universe: Age,History and other facts
Big Bang Theory-The premise