I am immortal in the interstellar eternity

The Earth was destroyed by gamma rays, and Yan Xia, as the only surviving human, embarked on a journey through the universe with the artificial intelligence Ella aboard the rocket. They constructed interstellar battleships ranging from ten thousand to one million meters, gigantic interstellar cities spanning billions of kilometers, and witnessed the ascent of countless technologies, all in search of the truth behind Earth's destruction. By harnessing powerful technology, they united dozens or even hundreds of civilizations, creating a formidable Federation of Civilizations, controlling billions of stars, and waging wars across dimensions. Each voyage was meticulously calculated over millennia