August 30, 2006

FROM THE SEPTEMBER 2006 LEGEND

Studying the Earth’s fluid core is not without its challenges for Dr. Behnam Seyed-Mahmoud (Physics).

The fluid core’s location (approximately 2,900 kilometres below the Earth’s surface) and temperature (it is thought to be 6,000 degrees C near the centre of the planet) make it impossible to conduct first-hand research on the deep interior of the Earth. “I can only study the fluid core theoretically and experimentally,” says Seyed-Mahmoud.

In a positive turn of events, a new rotating model of the Earth is allowing Seyed-Mahmoud to study fluid core dynamics experimentally from his geophysics lab in University Hall for the first time. “We theoretically predict the movement of the fluid, and then use the apparatus to see if the actual movement of the fluid matches our predictions,” says Seyed-Mahmoud.

Seyed-Mahmoud began designing the global geodynamics apparatus last spring after he received an NSERC grant of $21,400 per year for three years. The state-of-the-art apparatus was built at the U of L with the support of NSERC and the help of Arts & Science Technicians Heinz Fischer and Frank Klassen, Department of Physics Research Assistant Ian Schofield and undergraduate student employees.

The model has Earth’s three major parts — the clear acrylic mantle encompasses the fluid core and solid inner core. “The fluid between the inner core and mantle is water mixed with aluminum flakes. These flakes glow in light and allow us to see the motion of the water,” says Seyed-Mahmoud.

The metal divider between the globe and a light source has a horizontal slit that ensures only one thin sheet of the fluid core is illuminated at a time. The divider can be moved up and down to illuminate the fluid’s motion at various levels within the globe.

A camera on top of the globe follows the motion of the fluid. “When we cover the apparatus to prevent interference from other light sources, the camera only captures the particles on one sheet of light. We will use digital imaging to study the motion of the Earth’s deep interiors,” says Seyed-Mahmoud.

Klassen, the master builder behind the high-tech apparatus, says the box beneath the globe hides a lot of horsepower. “The controllable motor turns at 3,600 rotations per minute (rpm). We used pulleys to reduce the speed and ensure that the globe will never turn faster than 300 rpm,” says Klassen.

Third-year humanities major John Heikoop wrote the software that controls the motor’s speed. “The mini computer on the motor is connected to an external computer that can be used to monitor and control the motor’s speed,” says Heikoop.

A 150-lb. disc mounted on a turntable ensures that the globe maintains a constant speed without being affected by external vibrations.

A remote control can be used to trigger a back-and-forth motion that simulates one aspect of an earthquake on the rotating globe. The devices that create this motion are the same type of rotary servo actuators used to operate radio-controlled airplanes.

“Each servo has an arm that normally moves in a circular motion. Ian wrote a computer program that moves the arms in a back-and-forth motion, and I did the electronic debugging. It was a challenge to get the servos moving smoothly, but now the speed of the arms and how far they move can be controlled remotely to easily change the parameters of the experiment,” says Fischer.

With the exception of the remote control, the apparatus is operated through the external computer. Fourth-year physics major Refah Seyed Mahmoud has reduced the potential for user error by automating some of the data inputs required to run the computer’s programs.

Heikoop and Refah Seyed Mahmoud say that their wages weren’t the only payoff from their work on the apparatus.

“It is interesting to work in a lab. You learn a lot about yourself, the skills you’re good at and the skills you’re not good at, and what you enjoy and don’t enjoy. At the same time, it’s nice to know you have a part, even if it is very small, to further just a little bit our knowledge of the world, the stars and planets outside of our solar system,” says Refah Seyed Mahmoud.

Behnam Seyed-Mahmoud says the efforts of the Arts & Science technicians, Schofield and the students put a new spin on his original design for the equipment and improved the end result. “Their invaluable suggestions and contributions made the apparatus work even better than I had in mind,” he says.

The only other rotating global geodynamics apparatus in Canada that Behnam Seyed-Mahmoud is aware of is at York University. He plans to patent the equipment and continue his experimental and theoretical work to learn more about the Earth’s interior.

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