Doing the rough math, she would consider her people's major era to be maybe twice that. The Dark Ages, the Harrowing, then their era of Independent Enlightenment, the Plague, space travel, all the wars in between... "Yes, the Expansion Age was your three thousand years ago. We stopped exploring soon after that."
What did she know about nuclear energy? Maybe it was possible, but it was certainly not a good plan. Even though no one listened to her when she said so. So she came down and flipped, flying underneath him. "Now, hold arm out and make the five strongest weapons with your armor. You said you've been practicing."