This is the 13574th most frequent Russian word.
начинающемся
"In the beginning" or "starting."
Here, 'начинающемся' is used as an adjective to describe 'утре', indicating the emergence or start of the morning.
В начинающемся утре слышались звуки пробуждающегося города.
In the beginning morning, the sounds of the awakening city were heard.
In this sentence, 'начинающемся' modifies 'периоде', emphasizing the commencement of the mentioned discoveries era.
Мы стоим на пороге начинающемся периоде великих открытий.
We stand on the threshold of a beginning period of great discoveries.
The term 'начинающемся' here complements 'проекте', pointing to the initiation phase of the project.