ASK THE EXPERTS

Q: While walking along on a Gulf Coast beach one night, I noticed the sand beneath my feet illuminated green for a few seconds after each step. The harder I stepped, the brighter it glowed. What was the cause of this?

--Skip Anderson
Editor, Vanderbilt Register

A: You were almost certainly walking in the wet sand at the edge of the water. In the seawater and the wet sand were most likely bioluminescent dinoflagellates, microscopic algae that are a constituent of marine plankton. Bioluminescent dinoflagellates emit light when disturbed, such as by the bow of a boat passing through the water. Stepping in the wet sand produced such a disturbance, with a harder step producing a greater disturbance and therefore a greater emission of light.

James Staros
Professor and chair of molecular biology
Professor of biochemistry

Q:I've read that sunspot activity is currently at an 11-year high. Are there side-effects to this on Earth?

--Tara S. Donahue
Editorial assistant, Vanderbilt Register

A:One of the most obvious manifestations of activity at the surface of the sun is the presence of sunspots that follows a cycle with an average period of 11 years. Sunspots are small areas which are cooler than their surroundings and thus appear darker by contrast. They are caused by the presence of strong magnetic fields that give rise to other spectacular phenomena such as gigantic explosions (flares) and ejection of huge bubbles of gas into space (coronal mass ejections).

For earthlings, the current peak in solar activity makes the sun far more interesting to study but also more threatening, at least for our high-tech lifestyles. The gas from coronal mass ejections is made of charged particles (electrons and protons, mostly) that take about three days to reach the Earth. When they enter the Earth's magnetic field, they can cause "geomagnetic storms" with a most beautiful and eerie display of auroras. Magnetic storms can cause damage in very long, high-voltage power transmission lines. A very strong magnetic storm during the previous maximum caused a Hydro-Quebec black-out that affected 6 million customers in 1989. The increased amount of charged particles in the Earth's field can also damage the delicate electronics of orbiting satellites. Since the last solar maximum, our reliance on satellite communication technology has increased tremendously and the current level of activity is cause for concern. Fortunately, solar astronomers can give two- to three-day advance warnings to telecommunication companies. A powerful geomagnetic storm could result in significant disruptions but it will all go out with a magnificent display of northern lights!

Didier Saumon
Assistant professor of physics &
astronomy

-- Compiled by Jessica Hathaway

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