My one memory of the Secchi disk was when I took Earth Science during summer school one year. We went to a park by the bay and one of my classmates slowly lowered it into some murky water. He then proceeded to drop it in the river. The poor teacher had to get down to his skivvies and retreive it!
Even as someone who's read a lot about the Papacy it is hard for me to grasp how similar the Papal States were to neighboring Italian city-states. Here's a painting of Papal soldiers fighting bandits. Could you ever guess who they worked for from the uniform?
Indeed, the papal states were a fascinating institution. From a link in the submitted article:
> It is easy to forget that even if its political constitution was at odds with Europe’s ascendant liberalism, the Papal States of the 19th century was a fully functioning, modern state. Secchi contributed much to its welfare, helping with the construction of electric railways, installing lightning rods on important buildings, coming up with a system for the lighthouses in the ports and ensuring drinking water was potable. He supervised a precise geodetic survey along the Appian Way that became the basis for accurate maps of the region.
I'm reading a biography of Erasmus, and while he visits Italy, the Pope is waging war on Bologna and Venice, I believe. For fear of excommunication, Erasmus has to flee.
"Nicknamed the Warrior Pope or the Fearsome Pope, he chose his papal name not in honour of Pope Julius I but in emulation of Julius Caesar." https://en.wikipedia.org/wiki/Pope_Julius_II
True! But this was before the Papal States were incorporated into Italy and the same pope who commissioned the research detailed in the article became “a prisoner in the Vatican”.
We still use these in environmental science measurements! Both in school and in the real world. Friend of mine was a limnologist (lake scientist) and we'd paddle out in rowboats and take measurements, then have some beer and a picnic on the lake. All paid for by some grant or another.
Like the humble measuring tape around a tree at chest level, sometimes the simple tools are the best. They're timeless.
Often, having a higher quantity of cheap, mediocre data is better than a tiny handful of ultra precise measurements.
It's awesome going from the software world, counting double precision numbers, to field biology where you'd just lay ropes out in random places and count pine cones by hand, hoping you didn't miss too many.
It's funny, I always had this image of NASA and NOAA supercomputers doing detailed climate modeling (and sure, those exist too) but don't underestimate the power of just having hordes of boots on the ground (or in a boat) taking simple measurements.
This reminds me of the folks who walk up and down the New Jersey transit trains with little hand clickers measuring the number of passengers per transit leg.
With electronic ticketing apps you probably need this less but if you really want to get the accurate number of folks on the train, hand counting is still the best bet.
How do you quantifiably determine the point where something has slowly faded from view?
Edit: an idea — instead of “can you still see it?”, ask “can you prove you can still see it?”.
If the disk had an arrow then statistically you could measure how many times you fail to correctly see the direction in which the arrow is pointing.
As the disk gets deeper you’ll see the failure rate increase and maybe there is either a clear spike in failures or, more likely, a point where the error rate is above 50% / guessing for that particular field scientist’s eyesight. Maybe you could even calibrate eyesight so that results from different teams match up?
When the Secchi disk disappears from sight, note how deep the rope was submerged. They would probably also have factored in the ship's speed, I'm guessing.
I was canoeing in Minnesota two weeks ago as part of a Boy Scout camp and they offered a patch if we came back with several readings. The boys were interested and looked forward to taking the measurements.
Didn't realize the device was named after someone, we were told it was an acronym and the name morphed a bit to sound like a "sucky" disk.
"...The depth at which the disk disappeared from view would then establish the level of turbidity."
"...“Higher turbidity levels,” according to the EPA, “are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria.” "
In other words, the clearer water is often a sign of higher microorganism contamination? Quite surprising.
No, it's murkier water. The microorganisms cause the light to scatter, giving the water a duller appearance. Similar to how scuffed up glass will appear duller than polished glass. The microorganisms can also have a strong color, the most obvious example being algae. I imagine most of us have seen a bucket of water left in the sun turn green after a couple of days.
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[ 2.8 ms ] story [ 49.0 ms ] threadhttps://upload.wikimedia.org/wikipedia/commons/thumb/0/03/Ho...
> It is easy to forget that even if its political constitution was at odds with Europe’s ascendant liberalism, the Papal States of the 19th century was a fully functioning, modern state. Secchi contributed much to its welfare, helping with the construction of electric railways, installing lightning rods on important buildings, coming up with a system for the lighthouses in the ports and ensuring drinking water was potable. He supervised a precise geodetic survey along the Appian Way that became the basis for accurate maps of the region.
-- <https://www.americamagazine.org/arts-culture/2018/07/26/ange...>
"Nicknamed the Warrior Pope or the Fearsome Pope, he chose his papal name not in honour of Pope Julius I but in emulation of Julius Caesar." https://en.wikipedia.org/wiki/Pope_Julius_II
Like the humble measuring tape around a tree at chest level, sometimes the simple tools are the best. They're timeless.
Often, having a higher quantity of cheap, mediocre data is better than a tiny handful of ultra precise measurements.
It's awesome going from the software world, counting double precision numbers, to field biology where you'd just lay ropes out in random places and count pine cones by hand, hoping you didn't miss too many.
It's funny, I always had this image of NASA and NOAA supercomputers doing detailed climate modeling (and sure, those exist too) but don't underestimate the power of just having hordes of boots on the ground (or in a boat) taking simple measurements.
With electronic ticketing apps you probably need this less but if you really want to get the accurate number of folks on the train, hand counting is still the best bet.
Edit: an idea — instead of “can you still see it?”, ask “can you prove you can still see it?”.
If the disk had an arrow then statistically you could measure how many times you fail to correctly see the direction in which the arrow is pointing.
As the disk gets deeper you’ll see the failure rate increase and maybe there is either a clear spike in failures or, more likely, a point where the error rate is above 50% / guessing for that particular field scientist’s eyesight. Maybe you could even calibrate eyesight so that results from different teams match up?
Didn't realize the device was named after someone, we were told it was an acronym and the name morphed a bit to sound like a "sucky" disk.
"...“Higher turbidity levels,” according to the EPA, “are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria.” "
In other words, the clearer water is often a sign of higher microorganism contamination? Quite surprising.
Thanks. This is the missing piece in the otherwise informative and in-depth (...ahem) article.