Explain expansion of universe like am 5:)

Question

At a particular instant roughly 15 billion years ago, all the matter and energy we can observe, concentrated in a region smaller than a dime, began to expand and cool at an incredibly rapid rate.All this started as a dime? what is matter and energy on a empty space?https://www.scientificamerican.com/article/the-evolution-of-the-universe/

ktpsns · Accepted Answer

Forget about this explanation. The tale of the expanding universe is just the interpretation of an interesting solution of Einstein's famous equations of "general relativity". They are interesting because it matches observations. That discovery made people so crazy because many of them did not believe in Einstein's novel equations.That's something a five year old could understand. But it won't give him anything because the idea of big bang etc wasn't explained at all.