Vikings Use Crystal “Sunstones” to Discover America?维京人用水晶“太阳石”发现了美洲？

Ancient records tell us that the intrepid Viking seafarers who discovered Iceland， Greenland and eventually North America navigated using landmarks， birds and whales， and little else. There’s little doubt that Viking sailors would also have used the positions of stars at night and the sun during the daytime， and archaeologists have discovered what appears to be a kind of Viking navigational sundial. But without magnetic compasses， like all ancient sailors they would have struggled to find their way once the clouds came over.

根据史料记载，无畏的维京水手航行时仅仅依靠地标、鸟类与鲸鱼，此外并无其他仰仗——他们就这样发现了冰岛、格陵兰岛，最后还发现了北美洲。毫无疑问，维京水手在夜间航行时会参照星辰的位置，白天则借助太阳的方位。考古学家也确实找到了一种似乎是维京人航海日晷的实物。但如果没有磁力罗盘，一旦云层密布，他们就会像所有的古代水手一样难以找到方向。

However， there are also several reports in Nordic sagas and other sources of a sólarsteinn “sunstone”. The literature doesn’t say what this was used for but it has sparked decades of research examining if this might be a reference to a more intriguing form of navigational tool.

不过，在北欧的萨迦传说和其他资料中，还有一些关于 sólarsteinn，即“太阳石”的记载。在文献中，人们没看到太阳石能派什么用场，但由此引发了几十年的研究，研究太阳石是否是一种更奇妙的导航设备。

The idea is that the Vikings may have used the interaction of sunlight with particular types of crystal to create a navigational aid that may even have worked in overcast conditions. This would mean the Vikings had discovered the basic principles of measuring polar-ised light centuries before they were explained scientifically and which are today used to identify and measure different chemicals. Scientists are now getting closer to establishing if this form of navigation would have been possible， or if it is just a fanciful theory.

人们猜想，维京人可能利用了阳光与特定种类水晶的相互作用来创造一种导航设备，甚至阴天也可以使用。这意味着维京人当时已发现了测量偏振光的基本原理，至于它的科学解释，那是几百年之后的事了——如今，人们据此来鉴别测定不同的化学物质。古人真是这样导航的吗？抑或这只是天方夜谭？对此科学家已在进一步求证。

Scattering and polarisation

散射与偏振

To understand how this might have worked， we need to understand some things about the way light， and particularly sunlight， can be affected. Light coming from the sun is scattered and polarised by the atmosphere. This occurs when light is absorbed and reemitted with the same energy by air molecules and by different amounts depending on the light’s wavelength. The blue end of the light spectrum is scattered more than the red， as explained in theory developed by the British physicist Lord Rayleigh in the 19th century. Scattering by particles in the atmosphere explains why the sky appears blue.

要弄懂这种导航方法的原理，我们需要了解光尤其是阳光的传播会如何受到影响。阳光会被大气层散射和偏振。这些都发生在空气分子对光的吸收和再发射能量相同的时候，且吸收和再发射的量依光的波长不同而不同。正如19世纪英国物理学家雷利勋爵在其理论中所解释的那样，光谱中蓝光比红光更易散射。由于大气中微粒的散射作用，天空才呈现蓝色。

More importantly， scattered light waves are also polarised to a certain extent. That means they vibrate in one plane rather than in all directions at once. The amount of polarisation a beam of sunlight undergoes depends on its angle to the viewer and whether the light has been further scattered by cloud and other particles that cause depolarisation.

更重要的是，散射光也发生一定程度上的偏振。这意味着光波是在一个平面上振动，而不是在各个方向同时振动。一束阳光偏振多少取决于光线与观察者的角度，还得看云层及其他微粒是否导致阳光进一步散射，因为它们有消除偏振的作用。

Around the coastline of Norway and Iceland are found crystalline chunks of calcium carbonate known as calcite or Iceland spar. When polarised sunlight enters a calcite crystal， something very interesting happens. Calcite is strongly birefringent， meaning that it splits light passing through it into two separate waves that are bent or refracted in different directions and with different intensities， although the total intensity will be constant.

在挪威与冰岛的海岸线周围，有一种碳酸钙结晶块，人们称之为方解石或冰岛石。阳光经偏振射入方解石晶体时，会出现很有意思的现象。方解石有很强的双折射作用，就是说，在光透过晶体时，一束光会被分成两道不同的波，它们被弯曲或被折射向不同方向，强度也不相同，不过光的总强度不变。

This means that objects viewed through a calcite crystal appear in double. More importantly for our purposes， the different intensities of the two light waves depends on how the original light is polarised and the position and orientation of the crystal compared to the light source.

这意味着，透过方解石晶体看东西，看到的是两个像。这两道光波孰强孰弱取决于入射光的偏振情况、晶体相对于光源的位置和方向，这对于我们的目的更为重要。

Tourmaline and cordierite are crystals with similar properties， except instead of splitting light like calcite they are strongly dichroic. This means they absorb one component of polarisation more strongly than the other. Again， the dichroic properties depend on how the original light is polarised and the position and orientation of the crystal compared to the light source.

电气石与堇青石是与方解石性质相似的晶体，但它们具有显著的二向色性，不会像方解石那样分光。这意味着，它们对一部分偏振光的吸收程度明显高于另一部分。同样，二向色特性能否充分显现也取决于入射光的偏振情况、晶体相对于光源的位置和方向。

So， in theory at least， examining how sunlight passes through one of these crystals—and appropriately calibrated—could be used as a guide for sailors to estimate the position of the sun. This could then allow them to determine the direction of geographic north—even without understanding the scientific principles behind these phenomena.

因此，水手们可能会检查上述晶体经阳光穿入后所产生的现象，并恰当校准——以此作为指引，他们就能估计出太阳的位置，这至少在理论上是成立的。他们能够借此确定正北方位——即使不懂这些现象背后的科学道理。

If we make the huge assumption that the Vikings had these sunstone crystals on board their ships and， more importantly， knew what they were doing with them， the question this is whether the difference in the light would be detectable to their eyes？ And would it be detectable with enough accuracy （after errors because of imperfections in the crystals and depolarisation）， to be used as a navigation aid even in overcast conditions？