| http://www.w3.org/ns/prov#value | - So Ramskou argued that by holding a crystal such as calcite up to the sky and rotating it to check the direction of polarization of the light passing through it, the Vikings could have deduced the position of the Sun, even when it was hidden behind clouds or fog, or was just beneath the horizon.The obvious -- and probably fatal -- objection is that there is no real evidence the Vikings actually had
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