In short
Longevity escape velocity is a hypothesis — not an established scientific finding — proposing that if biomedical advances extend healthy life expectancy faster than one year per calendar year, a person alive when this threshold is reached could theoretically avoid dying of age-related causes indefinitely, as each year buys more than a year of additional life expectancy.
The concept was popularized by biogerontologist Aubrey de Grey, who has argued that a combination of therapies targeting the different forms of cellular and molecular damage he associates with aging (outlined in his SENS — Strategies for Engineered Negligible Senescence — framework) could, if developed and deployed continuously, eventually outpace the aging process itself for people who live long enough to benefit from successive waves of new treatments.
This is a forward-looking hypothesis about the trajectory of future biomedical progress, not a scientific finding about any current or near-term therapy, and it depends on several conjectural steps: that damage-repair approaches to aging will continue to be developed and will individually and cumulatively work as intended, that they will be developed fast enough to outpace the aging process, and that they will become broadly accessible. None of these steps has been demonstrated, and no current human life-expectancy trend data shows healthy life expectancy increasing at the rate the hypothesis would require.
This glossary treats longevity escape velocity strictly as what it is — a hypothesis and a framing device used in the longevity research and advocacy community to describe a potential future scenario — and not as a scientific claim implying that any currently available compound, therapy, or protocol will meaningfully extend an individual's lifespan today.