• Roman Space Telescope launches on SpaceX Falcon Heavy.
• Mission aims to map a billion galaxies to study dark energy.
• Telescope features a 2.4-meter primary mirror from a canceled spy satellite program.
• Roman will use three techniques to constrain dark energy's equation of state.

The Roman Space Telescope's launch may indicate a significant shift in NASA's priorities towards understanding dark energy, which could have profound implications for our understanding of the universe's expansion and ultimate fate. The mission's success suggests that repurposed spy satellite hardware can be effectively utilized in civilian space exploration, potentially opening up new avenues for cost-effective space missions.