In terms of Earth's technology alone, if learning to use fire in ancient times marked the first generation of civilization, and later learning to use electricity and magnetism was the second, then now that Earth Humans had mastered controllable nuclear fusion—with an abundant supply of ideal fuel like helium-3—they could be considered the third generation.
Each generation represented a qualitative leap and was of epoch-making significance.
To be precise, it was Country C's Underground Cities that possessed Nuclear Fusion Reactors. City No. 03, in particular, had now built a total of eight, meaning its power supply was extremely abundant.
It was precisely because of the helium-3 controllable nuclear fusion technology that Jiang Cai'Er's Artificial Little Sun and Aerospace Carrier projects were initiated and had been developing steadily.
