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The thought of aging is a major stress factor for many people, perhaps even more so than the physical act of aging. If you are one of those people, brace yourself.
Your head is actually aging faster than the rest of you. Before you freak out, though, know that it’s only by nanoseconds—90 billionths of a second over 79 years, to be exact. That kind of difference isn’t even noticed by humans.
This happens because of a relativity theory that Einstein developed and scientists later proved: The rate at which time moves depends on how fast you’re moving and how close you are to a gravitational field. For example, clocks at higher elevations run slightly faster than those at sea level.
Researchers at the National Institute of Standards and Technology (NIST) wanted to test that theory on an even smaller scale at just a one-foot difference. They used atomic clocks that “tick” as a single aluminum ion vibrates between two energy levels over one million billion times per second. When they raised one clock one-third of a meter (about one foot) above the other, the higher one ran at a slightly faster rate because it experienced a smaller gravitational force.
So if time moves faster at a difference of only a foot, it definitely goes faster at the height difference between your head and your feet, making your head the “oldest” part of your body.
Again, this aging doesn’t make any substantial impact on human appearance—we probably would have noticed by now if it did—although NIST believes the discovery could have practical applications in fields like geophysics.
