Tech billionaires aiming for immortality through extreme measures may be missing the point, according to physicist Prof Jim Al-Khalili. While some people are experimenting with unregulated peptide injections, cold plunges, and supplements to slow aging, the ultra-rich are pursuing more radical interventions. Bryan Johnson, a tech CEO, once injected his own 17-year-old son’s plasma in an attempt to stay young, though he later admitted it didn’t help. Al-Khalili, who will deliver the Royal Institution’s Christmas lectures on time, argues that focusing on extending life might distract people from enjoying the present. “We have a finite time in the universe,” he said. “The more I study time, the more I realize I want to make the most of the time I have.” He compares human existence to a “blink of an eye” compared to the age of the universe, suggesting that chasing more time might not be worth the effort. Al-Khalili has long been fascinated by time, dating back to his childhood when his engineer father said no one truly understood what time was. As a physicist, he learned that our everyday understanding of time is very different from the way it is treated in physics. For instance, Albert Einstein showed that time does not pass at the same rate for everyone. If someone is moving quickly past you with a clock, their second might feel longer to you. Similarly, gravity affects time, causing it to pass more slowly in stronger gravitational fields. This concept, Al-Khalili says, is “spine-tingling” because it means time can run at different rates depending on where you are. Einstein’s theories also offer an intriguing explanation for a classic Christmas tale. In Charles Dickens’s A Christmas Carol, the ghosts of past, present, and future appear on the same night to visit Ebenezer Scrooge. Al-Khalili explains that according to Einstein, all times—past, present, and future—might coexist in the same way that all points in space do. However, we only experience the present moment. The idea of meeting someone from the past or future is, in a way, a form of time travel. Al-Khalili plans to explore this concept in the Christmas lectures, explaining how time travel is mathematically possible, though in reality it’s complicated, like looping around a rollercoaster and returning to where you started. The direction of time—why it only flows forward—is another mystery Al-Khalili will address. Everyday experiences, like batteries running out or people growing older, suggest time moves in one direction. Yet the equations of physics do not favor any particular direction. After years of pondering this, Al-Khalili believes he has found an answer, which he will reveal in the lectures. The Royal Institution’s Christmas lectures, supported by CGI, will air on the BBC and iPlayer in late December, offering a fascinating exploration of time, its mysteries, and the science behind it.