Field of Science

Earthquakes and Telescopes

On Friday, February 26 at 10:34 PM PST there was an 8.8 magnitude earthquake in Chile. This earthquake released some 500 times more energy than the Haitian earthquake, but the death toll is only about 1/500 than that of Haiti. Thankfully, because Chile was prepared and because the epicenter was more distant from urban areas the destruction and human suffering was limited. My heart goes out to all those affected by the Chilean and Haitian earthquakes.

The astronomer in me immediately brought my mind to the telescopes in Chile. Chile is host to many present and planned astronomical observatories. If the telescopes there were to be destroyed or even minimally damaged it could set back astronomical research for years. How did the telescopes in Chile manage? So far I am only certain that the two 8.1 meter Gemini telescopes are okay and will carry on observations as normal tonight. High in the Chilean Andes there are many more astronomical observatories including the European Southern Observatory's Very Large Telescope, which is actually four separate 8.2 meter optical telescopes. The more I considered the region I realized that they are prepared for exactly this kind of event. Anil Ananthaswamy on the Edge of Physics blog explains with an excerpt from his new book why the VLT is most likely perfectly fine:
The primary mirror is 18 centimeters thick. Because of its weight, the mirror’s precise shape can warp when it is tilted, so 150 actuators, upon which the mirror rests, continually push and pull at least once a minute to ensure that the optimal curvature is maintained. More impressive than the actuators are the clamps around the edges of the mirror, which can, at a moment’s notice, lift the entire mirror, all 23 tons of it, off the actuators and secure it to the telescope’s support structure in case of an earthquake (moderate quakes, of less than 7.75 Richter, are not uncommon here, thanks to the ongoing collision of the Nazca and South American plates). The entire telescope is designed to swing during an earthquake, and securing the primary mirror prevents it from rattling against the metal tubes that surround it.
very large telescope mirror, VLT mirror
A Very Large Telescope primary mirror. The support structure and clamps are visible. Image by Dirk Essel

Update: Also NASA reports that the Chilean quake may have shortened earth days. The explanation for this  is of course the conservation of angular momentum: the earth is an ice skater pulling in its arms to spin faster.

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