Although Norse seafarers of the early medieval period lacked magnetic compasses, they navigated the open waters of the North Atlantic using calcite crystals known as Iceland spar. By holding these double-refracting crystals up to the sky, navigators could identify the position of the sun even under dense cloud cover or during twilight. A team of researchers led by Stephen Harrigan simulated these voyages under varying atmospheric conditions. The team found that while Iceland spar was highly reliable under overcast skies, its efficacy decreased significantly in heavy fog because the water droplets dispersed the polarized light, preventing the crystal from producing the distinct double-refraction pattern required for alignment. Consequently, during periods of thick fog, Norse navigators relied on alternative sensory cues, such as the behavior of seabirds and ocean swells, to estimate their position.
Based on the text, what is true of the use of Iceland spar by Norse navigators?
- AIt was primarily used to measure the height of ocean swells during overcast weather.
- BIt enabled Norse navigators to travel significantly faster than other medieval seafarers.
- It was less effective under foggy conditions than under cloudy skies.Cevap
- DIt operated on the same magnetic principles as early compasses.