"Synthetic Eternity" reimagines digital immortality by delving into the theoretical, technological, and ethical dimensions of transferring human consciousness into non-biological substrates. It introduces novel concepts like the Digital Consciousness Fidelity Index (DCFI) and adaptive synthetic neurons to evaluate the fidelity and integrity of mind uploading. By analyzing two key methods—scan-and-copy and gradual neural replacement—it critically addresses philosophical debates on identity, continuity, and qualia. Practical roadmaps, policy frameworks, and a fictional case study are incorporated to bridge speculative ideas with real-world applications. Ultimately, it frames digital consciousness as a profound moral and societal frontier rather than merely a technical challenge.