The conversation started over a backyard fence. An ecologist said surveying animals is a pain. An astronomer, said he could see objects in space billions of light years away. The neighbors, astronomer Steven Longmore and ecologist Serge Wich, of Liverpool John Moores University, developed a system of drones and cameras that can record rare and endangered species on the ground, day or night. Computer-vision and machine-learning techniques that help researchers study the universe’s oldest and most distant galaxies can now be used to find animals in video footage.

How did Vikings navigate? Crystals

When the Vikings left the fjords of Norway for uncharted territories, how were they able to traverse open ocean?

Norse sagas refer to a “sunstone.” In 1967, Danish archaeologist Thorkild Ramskou suggested it meant crystals. Multiple crystals fit the bill, calcite, cordierite and tourmaline. None have been found at Viking archaeological sites, but a calcite crystal was discovered in a British wreck from the 1500s, indicating it might have used by advanced navigators.

A study in Royal Society Open Science advances this idea, suggested that the Vikings had a high chance of reaching a destination in cloudy or foggy weather if they used sunstones. When polarized light passes through calcite, it splits into two beams. By rotating a calcite crystal against the sky and noting changes in brightness between these beams, one can find the atmosphere’s polarization rings and figure out where the sun is.

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