Observatories such as GEO 600 bounce lasers down long tunnels, hoping to pick up the fantastically small disturbances the waves should generate as they pass through the Earth.

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As Facebook is now offering the geo-targeting of ads down to ZIP code, this kind of fine-grained information is invaluable.

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At the closing bell, GEO is up about 0.4%, while APOL is down about 0.2% on the day Monday.

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