An ageold question
Craig Lindsay, of Totara Park, asked:
Is it true that people living on or near the equator age faster than those living further away due to the rotation of the earth and the speed at which the earth is rotating?
Kirk Hamilton, a physiologist from the University of Otago, responded:
When I read this question, I was immediately transported back to my ecophysiology days and remembered Bergmann's Rule.
In the 1840s, Bergmann noted that the body size of an endothermic (an animal that maintains a constant internal body temperature, e.g., birds and mammals) species increases as environmental temperature decreases compared with individuals of the same species living in warmer temperatures. The idea is that an animal with an increased body size has a smaller relative surface area to volume ratio for heat loss relative to heat production. Also, we can think about this with respect to animals living near the equator versus at higher latitudes. Does this have implications on life expectancy?
From an ecophysiological viewpoint, animals living nearer to the equator may struggle to maintain body temperature and might have a shorter life expectancy. Is this the case?
Depending upon where one lives, plus modern medicine, exercise, lifestyle, healthy eating, and other factors might all contribute to how long we live. Interestingly, the average life expectancy of a New Zealander was 69 years of age in 1950 compared with 82 years in 2019. There is a large difference in climate when one compares the equator to Cape Reinga and Stewart Island. But, if we examine Ecuador, which lies very close to the equator, the average life expectancy was only 47 in 1950 but 77 in 2019. But, what is the effect of rotation and the speed the earth is rotating on aging?
In 1905, Einstein published his theory of relativity. He suggested that time moves more slowly for an object in motion compared to a stationary object. And, that time moves more slowly as the magnitude of gravity increases. This suggests that we are not all experiencing time at the same rate. The faster one moves, the more time slows down. A case in point is Scott Kelly, an astronaut who lived on the International Space Station for nearly one year (March 27, 2015, until March 1, 2016) and was orbiting the earth at 28,200kmh at an elevation of 773km. Scott has an identical twin brother, Mark. It was the perfect experiment to test the question asked about aging, speed, and rotation of the Earth. It was determined that while Scott was orbiting the earth, he had aged five milliseconds fewer than Mark.
I, too, am a twin and it is comforting to know that my brother will always be more or less seven minutes older than me, but even older if I take a trip to Jupiter or Mars.
Send questions to: AskAScientist, PO Box 517, Dunedin 9016 Or email
question.aas@gmail.com