Sunstones - the Viking navigation crystals

[NomoneyNohoney]

https://www.heritagedaily.com/2022/07/s ... als/144085

How Vikings Used “Sunstones” for Navigation at Sea?
The above is a populist report of their usage, if it interests you enough, below is a contra point of view for consideration:
https://skjalden.com/viking-sunstone/

[XFool]

https://www.heritagedaily.com/2022/07/sunstones-the-viking-navigation-crystals/144085

How Vikings Used “Sunstones” for Navigation at Sea?
The above is a populist report of their usage, if it interests you enough, below is a contra point of view for consideration:
https://skjalden.com/viking-sunstone/

Interesting. I haven't fully read the above yet, so this comment is a little premature. However...

When I first read the post my immediate thoughts were: "Crystals? Sunstones? Oh yeah..."

But when I followed the first link and saw the picture of a hand holding up the transparent crystal my next thought was: "Polarised light?"
My understanding being that this method is used by honey bees to navigate, even when the sun is obscured by clouds. They can perceive a 'bar' across the sky related to the position of the sun. I have tried to see this myself with polaroid sunglasses, but cannot claim to have succeeded, possibly because unlike me, the bees can see into ultra violet wavelengths? So how this could work with human eyesight I do not know.

Long ago at work I used this 'understanding' of bee navigation techniques, to apparently great effect, to rapidly get a bee out of small office occupied by two women who had called on me to help. A bee had got into the room and was 'staggering' around all over the place alarming the occupants. I reacted instinctively (bearing in mind the bees use of UV in navigation). The small room had one casement window and was lit by florescent lights, which were on. I fully opened the top of the casement window and then turned the lighting off.

The bee immediately made a literal beeline exit through the open window from the far end of the room. The reasoning(?) being: florescent light work via producing UV radiation - possibly swamping the bees navigation system, leading to its confusion and erratic behaviour. Turn off the UV and let the bee see the sky through the (now open) window - navigation system reset. Whether the reasoning was sound I cannot really say, not being a bee, but the bee left the room very smartly so object achieved!

Better read the articles now.


PS. From the second article:

"There is no doubt, that a sunstone can be used to locate the sun. This method with a dot has been tested, and it was possible to find the location of the sun within one degree, even on cloudy days, or under dark twilight conditions when the sun was just 4 degrees above the horizon."

[GrahamPlatt]

I opened the heritagedaily link, and saw another article to the right "Discover Roman London" (https://www.heritagedaily.com/2022/07/d ... don/144044). This article states that "During the 2nd century AD, Londinium had reached its peak, with about 45,000-60,000 inhabitants , covering an area of 330 acres north of the river Thames."
Now an acre is ~4046 square metres. So each individual had between 22-29 square metres. Doesn't seem feasible.

[mc2fool]

I opened the heritagedaily link, and saw another article to the right "Discover Roman London" (https://www.heritagedaily.com/2022/07/d ... don/144044). This article states that "During the 2nd century AD, Londinium had reached its peak, with about 45,000-60,000 inhabitants , covering an area of 330 acres north of the river Thames."
Now an acre is ~4046 square metres. So each individual had between 22-29 square metres. Doesn't seem feasible.

Do you think that's not enough or too much?

Wikipedia's Londinium page supports the population figure,"During the early 2nd century, Londinium was at its height, having recovered from the fire and again had between 45,000 and 60,000 inhabitants around the year 140".

Unfortunately it doesn't give a contemporaneous size, saying only that following its foundation in the mid-1st century "early Londinium occupied the relatively small area of 1.4 km2 (0.5 sq mi), roughly half the area of the modern City of London". However, Wikipedia's London Wall page says that the wall, which was built late 2nd to early 3rd century "was 2 mi (3.2 km) long, enclosing an area of about 330 acres (130 ha)".

So, WIkipedia at least seems to support those figures.