ambience: Running river
Since the days of the earliest irrigation systems, thousands of years ago, humans have been moving and redirecting water to fulfill our needs. As a result, there’s evidence that we’ve changed the rotational speed of the earth. I’m Jim Metzner, and this is the Pulse of the Planet, presented by DuPont.
“It’s been said that humans were just an invention of water to get itself moved around the planet and obviously, it’s kind of a humorous thing to say but nonetheless if you actually look at what humans have done to water, yeah, you could sort of believe that.”
Melanie Stiassny is a curator of fishes at the American Museum of Natural History.
“Sixty percent of the earth’s river flow has been changed by humans and one of the large things we do is build dams and these dams create reservoirs.”
All those dams and reservoirs mean that a significant portion of the Earth’s water never makes it to the ocean, and is instead diverted to fulfill human needs. Its this global redistribution of water which has apparently had an affect on the Earth’s rotation.
“Just the fact that we humans have dammed so many rivers. Have built so many reservoirs. We’ve actually redistributed the weight of the planet. And that has actually had a measurable effect on the geodynamics of the planet. In fact it has had a measurable effect, albeit in nanoseconds but a measurable effect. It’s changed the length of day on the planet because it’s changed the rotation of our planet.”
And how can we tell if the earth is spinning a little a more slowly? Well, with the help of a network of radio telescopes around the world, scientists use the position of a distant star as a kind of benchmark against which they can check variations in the earth’s rotational speed.
Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation. I’m Jim Metzner.