Traveling 120 light years depends entirely on the speed of the spacecraft:
- At the speed of light (about 299,792 km/s), it would take exactly 120 years to travel 120 light years, since a light year is the distance light travels in one year.
- The fastest human-made spacecraft as of 2025 is the Parker Solar Probe, which can reach speeds up to about 192 km/s (692,000 km/h), roughly 0.00064% the speed of light
Using the Parker Solar Probe's speed as a benchmark:
- Time to travel 1 light year at 192 km/s is approximately 5,000 years.
- Therefore, to travel 120 light years at that speed would take roughly 600,000 years.
If we consider a hypothetical spacecraft traveling at 99% the speed of light, relativistic effects come into play. For an observer on Earth, it would take about 121 years (120 / 0.99) to cover 120 light years. However, due to length contraction, the travelers would experience a shorter duration, roughly around 14 years for a 100 light-year journey, so approximately 17 years for 120 light years
. In summary:
Speed| Time to travel 120 light years (Earth frame)| Traveler's experienced
time (approximate)
---|---|---
Speed of light (c)| 120 years| 0 years (photons experience no time)
99% speed of light (0.99c)| ~121 years| ~17 years (due to relativistic
effects)
Parker Solar Probe (~192 km/s)| ~600,000 years| Similar to Earth frame (non-
relativistic)
Thus, with current technology, traveling 120 light years would take hundreds of thousands of years. Only near-light-speed travel could reduce this to a human lifetime, but such speeds remain theoretical for crewed spacecraft
