The Physics of Time, and Why Living Forever Misses the Point
Physicist Jim Al-Khalili says technology billionaires trying to live for ever are wasting their time. He spoke ahead of his forthcoming Royal Institution Christmas lectures on time, The Guardian reported on 18 September 2026.
The lectures will examine the physics of time, including time travel. Al-Khalili said travel back in time is possible in mathematics. They will cover time as lived experience and as a problem in mathematical physics, where researchers use equations to study how time works.
He tied that physics to longevity research. He said people who spend energy trying to live for ever may miss out on the here and now. His point was opportunity cost, a trade-off in which effort aimed at extending life without limit takes attention from present life.
The same report cited tech CEO Bryan Johnson, who tried injecting plasma from his 17-year-old son and later said he saw no benefit from it.
Al-Khalili is the author of On Time: The Physics That Makes the Universe Tick, published by Princeton Press in September 2026. The book and the lectures both focus on the structure of time, why it points in one direction, and how it is measured.
The broader context here is a clash between two uses of physics. One treats time as a coordinate to bend, through closed timelike loops allowed in general relativity or through medicine aimed at slowing ageing. The other treats time as a constraint that gives physical processes their order. Al-Khalili places himself in the second group. Time travel can be written down, but indefinite survival cannot be built from that maths. Longevity ventures often borrow language from thermodynamics, information theory and systems biology, and that borrowing lends authority. His reply returns the test to physical plausibility. What is possible on paper, like a drawing that cannot be built, is not close in practice.
In my view, the here and now remark deserves as much weight as the dismissal. It shifts the question from can we extend life to what that effort is worth. Even with slow, step-by-step gains, hard questions would stay about who funds the research, who gets the treatments, and what counts as benefit. Johnson's report of no benefit shows the evaluation problem. A personal report, with uncontrolled conditions and short follow-up, cannot settle whether a treatment works, but it can shape public hopes. Time stays finite for observers living inside it. Mathematics can describe paths that living bodies cannot follow, and Al-Khalili's task is to explain how both statements hold at once.
