Observing with Street Lights

Observing with Street Lights
Dark sky sites not always necessary to see the Milky Way (This image was taken ouside of a B&B in Julian, CA)

Thursday, September 28, 2017

Vikings at L'anse aux Meadows; How did Viking sun tracking work? Viking Sea ship cruise map; Great classical mechanics and astrophysics website; Time zones and martini service!

Greetings from Palmia Observatory

Well we just left L'anse aux Meadows, Newfoundland last night and headed into the Gulf of St. Lawrence as our journey "In the wake of the Vikings" continues on the cruise ship Viking Sea.  The stop in the location of the first and oldest Viking settlement there was very educational and I identified at least two topics that i want to study further and they are: (1) Smelting of "bog iron" for weapons, jewelry and nails, and (2) Viking navigation westward by looking at the sun.
Leif Erikson is credited with making the voyage from Greenland to here in the 10th century.  The establishment in Newfoundland did not last very long and was eventually abandoned.  But the archeological ruins reveal something of their lifestyle under the harsh conditions and the remains of a smithy for forging nails for ship repair and other implements.  The photo below shows a recreation of a Viking forge for melting and converting bog iron into useful tools.  First off for we was to understand what bog iron is and where it was found.


Recreation of Viking establishment and forge at L'anse aux Meadows, Newfoundland (Source: Palmia Observatory)
Recreation of Viking establishment and forge at L'anse aux Meadows, Newfoundland (Source: Palmia Observatory)
A Wikipedia search tells us that Bog iron is apparently found quite often along the coastline where rivers and associated ponds allow for the deposition and concentration of dissolved iron by bacteria which concentrates the iron in little nodules.  The nodules can be dug up and separated from the earth and then refined by heat and hammering.  Pretty neat!  I thought they might have had to have big pit mines or some such of thing in order to get iron, but no just dig up the dirt in shallow ponds that have the tell tale sign of an oily film due to the bacteria.

The second interesting idea for more study has to do with how Viking navigators could find their way westward when no shoreline was visible.  The TV series called "The Vikings" was playing again on the ship TV and I payed special attention this time as the main character, Ragnar, explains to his brother how he plans to track the sun during a westward voyage of discovery to new lands.  He describes a floating sundial to be used to measure the highest position of the sun in the sky and marks the length of the shadow.  On the next day, he does the same thing and if the length of the shadow at high noon is greater than at the start he changes course so that the length on the next day remains close to that at the journey start.  This way he says he can steer just plain westward.  But what if the clouds are out at noon for days at a time, which we know is quite common now?  Ragnar explains that he has a "Sunstone" and he can use that to mark the position of the sun on cloudy days.

How could this sunstone work?  Well, Wikipedia says that the sunstone could have been some type of easily available birefringent crystal, such as calcite, which produces two separate images of an object seen through the crystal, due to differences in light polarization.

Wow, could this really work?  My astronomical question is: (1) Does the sun navigation method outlined in the TV series really result in a path that is just plain westward?  (2) Can you see enough of a difference in the solar image due to polarization effects such that you can indeed identify the location of the sun through the clouds?



Was a birefringent crystal such as this one an example of Viking "Sunstone" (Source: Wikipedia)
Was a birefringent crystal such as this one an example of Viking "Sunstone" (Source: Wikipedia) 

Ok, all of you astronomer and physicist wannabes, take that on as your homework!  While you are at that you might also want to check out a really neat website that mirrors the textbook "Physics from Planet Earth" and offers a lot of free interesting problems and interpretations on the associated website.  This web reference was provided by Searching for Gravity Waves, Dr. Gary.  He has found the site very informative, but beware it is not for the mathematical faint of heart.  I looked at it and found that the author uses many interesting recent astronomical and astrophysics examples to use to as teaching tools to learn classical mechanics from an advanced point of view.  Thanks for that Gary.  Check it out at: https://physicsfromplanetearth.wordpress.com/

So, we have also experience many cloudy skies on our journey and we have no sunstone or sundial but luckily can look up our location by watching TV.  The screenshot below shows our journey starting in Bergen, Norway and now just past L'anse aux Meadows and entered the Gulf of St. Lawrence on the way to Montreal and Quebec.  It is easy for us today to know where we are and with airconditioned staterooms we can sail in comfort while the early Vikings in their open boats faced high risk every day.


"In the Wake of the Vikings" ship tracker screenshot (Source: Viking Cruises)
"In the Wake of the Vikings" ship tracker screenshot (Source: Viking Cruises)


Our westward journey required turning our clocks back an hour every day or so.  The ship operates on ship time which roughly corresponds to the conventional time zone, but when we approached Newfoundland, the time change was just for 1/2 hour.  What was this all about?  Well, remember that Newfoundland is an island and was independent from Canada until the 20th century and they had elected the best time zone for their longitude.  When they joined Canada, they had a public referendum and decided not to change their time zone to match the other close Canadian provinces, so this is what we have to deal with.  I wonder if my goto telescope can be set to this time zone with the 1/2 hour offset?

Now that we have left Newfoundland, the ship clock time is retarded 1.5 hours to make up for all of this.  Note the circuitous route of the time zones around the island Newfoundland in the following screenshot.



Time zones and the odd 3 & 1/2 hour shift from GMT for Newfoundland (Source: Wikipedia)
Time zones and the odd 3 & 1/2 hour shift from GMT for Newfoundland (Source: Wikipedia)

Well, no matter what time zone we find ourselves in, it has to be 5:00 somewhere and the ships bars are mosly always open to make our favorite drinks and martinis.  Except, now that we have entered Canadian waters, the local rules apply and the ship is allowed to have only one bar per deck open.  This is something I had not anticipated bu we should be able to survive.  Luckily the early Vikings had no local customs to follow and could drink and pillage as they saw fit.



Luckily it's always 5:00 in one of the ships bars (Source: Palmia Observatory)
Luckily it's always 5:00 in one of the ships bars (Source: Palmia Observatory)


We have the option of watching the sea from many different locations, but here Resident Astronomer toasts to our view from the forward Explorers Lounge.



 Resident Astronomer Peggy enjoys the view and a cosmo from the Explorers Lounge (Source: Palmia Observatory)
Resident Astronomer Peggy enjoys the view and a cosmo from the Explorers Lounge (Source: Palmia Observatory)

Our geographic latitude is now continuously decreasing and the clouds seem to almost be increasing so we might be at the end of our ability to see more northern lights.  The shipboard lights have been quite bright also and I haven't even tried to find and get a good image of the Milky Way.  Oh well, it has been a lot of fun.


Until next time




www.palmiaobservatory.com



No comments:

Post a Comment