u/LegalGeneral7817

Do we slow down the rotation of the Earth?

I read that the Three Gorges Dam in China slows down the rotation of the earth by 0.06 µs, because of it being massive. But this is where my question comes in. Massive in what way? Does the weight of the structure make the earth slow down? If so, has the amount of buildings we have built over time not slowed down the earths rotation massively, and thus made our days longer? And did the boom in population we have witnessed, especially in the 20th century not have an influence? If the word "massive" refers to size, then wouldn't the same be true? I have surely missed something in my way of thinking, but what have i missed? Explain it like im 5 years old please.