The tree · Biology · World event · Mid: 5 to 20 years
A person lives a full year in partial gravity and comes home without disqualifying harm
The longest stays off Earth are a year or more in free fall on the space station, where bone, muscle, eye, and heart changes are well documented. Nobody has lived even a month in partial gravity. A year on the Moon (or in a spinning facility set to lunar or Martian gravity) with published health outcomes that would not bar a return trip is what a rotation of months, the A2 tier, assumes.
What counts as it having happened
A person completes twelve continuous months at a sustained gravity level between one-sixth and one-half of Earth's, and a peer-reviewed report of their health outcomes finds no condition that the responsible agency's own standards would count as disqualifying for a further mission.
Settled by: The peer-reviewed health report and the agency's crew-health standards
Probability, by longevity scenario
| baseline2071 ± 8 | moderate2080 | strong2095 | radical2136 | openno deadline |
|---|---|---|---|---|
| 35% | 42% | 50% | 65% | 70% |
Each number is the chance this resolves yes before that scenario's window closes, given that everything it depends on resolves first. Estimated 2026-09-08.
Why these numbers: Given people on the Moon or a spin facility, a year-long stay is a matter of decades, and then roughly two in three that the health outcomes clear the bar; bone and eye effects in free fall are the warning.
Notes
Edge drawn at step 7 (2026-09-08): a year in partial gravity needs either people on the Moon or a spinning facility; either route will do.
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The record itself is data/B-biology.toml in the public repository.