Question

The Local Group is only one of many, many clusters of galaxies. All of the galaxies are all moving away from each other causing more and more space to come between them. This means the universe is expanding. That discovery is what led to

Answer 1

Answer: this theory/hypothesis is a result of another idea, i.e. idea according to which after the Big Bang (hypothesis, again) and since then cosmos/Universe is expanding so all the object found in the universe are moving from each other. There is another idea that after expanding will follow shrinking. We found ourselves in pure theorizing, of course.

Step-by-step explanation:

Answer 2

The proposal of the Big Bang Theory.

Step-by-step explanation:

This theory suggests that the universe originated from a singular and incredibly hot and dense point, more than any known black hole or star. And this point quickly (even faster than the speed of light) expanded itself from a subatomic size to the universe that we see today. After the violent blast, the expansion of the universe slowed down, and that is why the universe continues to expand, as a remnant of the Big Bang.

In 1927, the Belgian Catholic priest Georges Lemaître proposed the first expanded model of the universe, and since then scientist has been studying the universe in search for real evidence to confirm this theory.