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Navigation – Science, History, and Cultural connections
How did humans learn how to navigate the world? No one person, from any one culture, ever figured it all out on their own. Navigation developed over time, over the globe, with contributions from different people and cultures. This is a story of world history, of science, of astronomy, of story telling, and of multicultural collaboration over the millennia.
Earliest known maritime navigation
The Austronesian peoples are a large group of various peoples from Taiwan, maritime Southeast Asia, Oceania and Madagascar, united by a language family.
They appear to originate from a prehistoric seaborne migration from Taiwan, somewhere between 5000 to 1500 BCE.
Peoples from these migrations reached parts of the Philippines around 4000 BCE.
They were the first people to invent maritime sailing technology – catamarans, outrigger boats, lashed-lug boat building, and the crab claw sail.
Around 1500 BCE some groups from the Philippines went out and colonized the islands of Micronesia (thousands of small islands in the western Pacific Ocean.)
By about 900 BCE their descendants had spread across the Pacific, reaching Tonga and Samoa. In this region, a distinctive Polynesian culture developed.
Polynesian navigators used a range of tools and methods:
observation of birds, star navigation, and use of waves and swells to detect nearby land.
Songs, mythological stories, and star charts were used to remember navigational information.
(text in this section excerpted and adapted from Wikipedia. Austronesian peoples, Polynesian navigation)
See the PBS TV show Polynesia’s Genius Navigators
Here is the hand method used to find the altitude of the Polaris, to estimate one’s latitude.
from Ben Finney et al., Re-learning a vanishing art
We read in the article (Re-learning a vanishing art, Ben R. Finney)
The clearing skies after the storm enabled Nainoa to make multiple star observations in order to determine latitude. For example, on the night of March 23-24 he was able to estimate that the canoe should reach 10°N around sunrise by measuring, with his outstretched hand, the angular height of Polaris (Figure 7) and the angular height of Acrux (the bottom star of the Southern Cross when upright, Figure 8).
In addition, observations of two other stars confirmed the latitude. This measurement turned out to be only 21 miles off, for at sunrise the canoe was actually 21 minutes of latitude north of 10 °N.
We see this same method used in the Disney film, Moana
“Waialiki using this technique to measure the altitude of a group of stars. Look closely and you can see that she’s measuring the stars in Orion’s Belt. The position of Moana’s hand indicates the star above her index finger has an altitude of 21º. Given that the movie takes place about 2,000 years ago near Samoa, the position of Orion indicates they are travelling exactly due East.”
Screen shot from Disney movie Moana
How far they’ll go: Moana shows the power of Polynesian celestial navigation, Duane W. Hamacher and Carla Bento Guedes, The Conversation
Rebbelib aka Marshall Islands stick chart
Made of bamboo and shell maps.
Possibly used since circa 1000 CE, right up to the modern era.
This comparison of a stick chart with a more modern map was made by Reddit user lander ceuppens.
These charts show
major ocean swell patterns; the ways that islands disrupt those patterns,
made from coconut fronds and shells
Islands are represented by shells tied to the framework, or by lashed junction of 2 or more sticks.
Threads represent prevailing ocean surface wave-crests and directions they took as they approached islands
Charts varied so much in form and interpretation that the individual navigator who made the chart was the only person who could fully interpret and use it.
Use of these ended after World War II when new technologies made navigation more accessible.
Navigation of the ancient Mediterranean
We read from By Dr. Markus Nielbock
Around the middle of the 4th millennium BCE, Egyptian ships sailed the eastern Mediterranean and established trade routes with Byblos in Phoenicia, the biblical Canaan, now Lebanon. This is about the time when the Bronze Age began.”
… Soon, the navigators realised that celestial objects, especially stars, can be used to keep the course of a ship. Such skills have been mentioned in early literature like Homer’s Odyssey which is believed to date back to 8th century BCE.
The original sources are thought to originate from the Bronze Age, in which the Minoans of Crete were a particularly influential people. They lived between 3,650 and 1,450 BCE.
Navigation in the Ancient Mediterranean and Beyond, By Dr. Markus Nielbock
Navigation in the Ancient Mediterranean and Beyond, Astro.edu
Minoan, Greek, and the Phoenician civilizations of the ancient Mediterranean.
Around 200 BCE the Antikythera mechanism was invented. Shockingly, this was a simple analogue computer and orrery. It was used to predict astronomical positions and eclipses for calendrical and astrological purposes. It and its possible sister devices may have been used in navigation.
800 – 1100 CE Viking Navigators
PBS Nova Secrets of Viking Ships
and PBS The Vikings
1200s-1400s Swahili East African coast
The Swahili coast is a coastal area of Southeast Africa on the Indian Ocean. It is inhabited by the Swahili people. It includes the coastal regions of Mozambique, Kenya, and Tanzania as well as the coastal islands.
This area was historically known as Azania or Zingion in the Greco-Roman era, and as Zanj or Zinj in Middle Eastern, Chinese and Indian literature from the 7th to the 14th century.
coastal elites invested in long‐distance voyages at least as early as the 13th century and that a small number of ships owned by Swahili patricians sailed as far as Arabia and, from the 16th to mid–18th centuries, Western India (Vernet in press).”
… Yemeni sources confirm that, during that century, ships from Mogadishu made annual trips to Aden, al‐Shihr, and other Hadramawt ports… the general prosperity of the years 1200–1340 led the Swahili to increase regional navigation and develop regular overseas trade.
When Did the Swahili Become Maritime? Jeffrey Fleisher et al., American Anthropologist, Vol 117, No 1, 3/2015
1300s CE Jacob’s Staff
In 1342 CE the Jewish scholar Levi ben Gershon, known as Gersonides, wrote “On Sines, Chords and Arcs,” proving the sine law for plane triangles and giving five-figure sine tables.
Gersonides also created the astronomical, surveying, and navigational device known as the Jacob’s Staff.
1400s CE Ancient Chinese Explorers
Ancient Chinese Explorers
A century before Europeans ‘discovered’ the Indian Ocean, Chinese merchants led by the redoubtable Zheng He (1371-1433) journeyed as far as Zanzibar. See the PBS NOVA program Sultan’s Lost Treasure (2001)
1400s CE Astrolabe
Abraham Zacuto (Abraão ben Samuel Zacuto) 1452 – 1515 CE
A Spanish Jewish astronomer, mathematician, rabbi and historian. Served as Royal Astronomer to King John II of Portugal.
He developed a new type of astrolabe, specialized for practical determination of latitude while at sea, in contrast to earlier multipurpose devices intended for use ashore.
(I couldn’t find a good picture of original version. This photo is from a more advanced model in the 1800s.)
18th century astrolabe made in North Africa.. Photo by Evan Bench, https://www.flickr.com/photos/austinevan/3317031220
1400s CE Navigational almanac
Abraham Zacuto’s principal claim to fame is the great astronomical treatise, written while he was in Salamanca, begun around 1470 and completed in 1478.
It was composed of detailed astronomical tables (ephemerides), with radix set in year 1473 and the meridian at Salamanca, charting the positions of the Sun, Moon and five planets. The calculations were based on the Alfonsine Tables and the works of earlier astronomers (notably of the 14th-century Majorcan school
He set the data in a simple format, with the positions of a planet easily interpolated between entries, making it quite easy to use.
His disciple Joseph Vizinus adapted it into a Latin translation. This revolutionized ocean navigation. Prior to the Almanac, navigators seeking to determine their position had to correct for compass error (deviation of the magnetic north from the true north) by recourse to the quadrant and the Pole Star. But this proved less useful as they approached the equator and the Pole Star began to disappear into the horizon.
Zacuto’s Almanach supplied the first accurate table of solar declination, allowing navigators to use the sun instead. As the quadrant could not be used to look directly at the sun, Portuguese navigators began using the astrolabe on board (an old land-based instrument to measure the height of the sun indirectly).
Zacuto’s tables in conjunction with the new metal nautical astrolabe allowed navigators to take accurate readings anywhere. Already in 1497, Vasco da Gama took Zacuto’s tables and the astrolabe with him on the maiden trip to India.
The above section excerpted and adapted from Abraham Zacuto, Wikipedia.
Z is for Abraham Zacuto, Zacuto, Biographical Encyclopedia of Astronomers
1500s CE Mercator map
Perhaps the most useful map made for ocean navigation. Read all about it here, Mercator maps: Use and criticism
1700’s-1800s CE The Binnacle
One of the great advances in navigational equipment was the binnacle: This is a waist-high case found on the deck of a ship, that holds the compass. It is mounted in gimbals to keep it level while the ship pitched and rolled. It has a mechanism to compensate for errors in detecting the Earth’s magnetic field. Every ship’s captain would use one.
With the introduction of iron-clad ships the magnetic deviation observed in compasses became more severe. Methods of compensation by arranging iron or magnetic objects near the binnacle were developed.
Lord Kelvin patented in the 1880s a system of compass and which incorporated two compensating spheres. These are colloquially known as “Kelvin’s balls” in the UK, and “navigator’s balls” in the United States
The Binnacle
Photo by RK
The Chronometer
Making the sea clock practical was critical to improving sea navigation. It was the only way to keep track of the ship’s latitude. See the Chronometer
See the PBS show “Lost at Sea: The Search for Longitude,” and the book Longitude by Dava Sobel.
The Search for Longitude
The Sextant
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects.
It measures the angle between an astronomical object and the horizon for the purposes of celestial navigation.
Sextant by E. & G. W. Blunt, New York, and Quadrant by David White Co. for the US Navy, c. 1930 – Museum of Science and Industry (Chicago) Wikimedia Commons
Justin Shin points out that we can turn ourselves into (approximate) human sextants!
Point at the horizon with one arm and at the north star with the other arm. The angle that your arms make gives you your latitude on the planet.
Pointing to the horizon gives you a tangent line to a circular earth. Pointing at the north star give you a line parallel to the earth’s north/south axis, Everything else follows pretty neatly
Resources
PBS NOVA Secrets of Ancient Navigators
Celestial navigation in the Classroom
Re-learning a vanishing art, Ben R. Finney et al., p.41-90, The Journal of the Polynesian Society, Vol. 95, No 1, 1986
Learning Standards
Ocean Literacy Scope and Sequence for Grades K-12
b) The ocean provides food, medicines, and mineral and energy resources. It supports jobs and national economies, serves as a highway for transportation of goods and people, and plays a role in national security.
c) The ocean is a source of inspiration, recreation, rejuvenation, and discovery. It is also an important element in the heritage of many cultures.
National Standards for History Basic Edition, 1996
5-12 Identify major technological developments in shipbuilding, navigation, and naval warfare and trace the cultural origins of various innovations.
Massachusetts History and Social Science Curriculum Framework
The Political, Intellectual and Economic Growth of the Colonies. Explain the importance of maritime commerce in the development of the economy of colonial Massachusetts, using historical societies and museums as needed.
A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012)
Some objects in the solar system can be seen with the naked eye. Planets in the night sky change positions and are not always visible from Earth as they orbit the sun. Stars appear in patterns called constellations, which can be used for navigation and appear to move together across the sky because of Earth’s rotation…. The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them. This model of the solar system can explain tides, eclipses of the sun and the moon, and the motion of the planets in the sky relative to the stars.
Radians
Learning goals: Students will understand
why we traditionally measure angles in degrees
that the usually stated number of degrees in a circle is a social/cultural convention, not a scientific or mathematical fact
that there exists a purely natural measure of angles (radians)
that natural units are not social/cultural conventions: rather they are relationships that exist independently of human choice.
We usually measure angles in degrees. But today we’re going to learn about another way to measure angles, called radians.
First let’s think about everyday life: Outside of school, in any construction project, we measure angles in degrees.
That just seems like the only and obvious way.
Plumbing and Heating (46.0503) T-Chart
We’re told that there are 360 degrees in a circle.
But once we get to high school trigonometry we start using a different way of measuring angles.
Asking “Why change?” might be wrong question.
A better question would be “Why did we start measuring angles in degrees to begin with?”
Because 2500 years ago ancient Sumerians discovered that there were about 360 days in a year, that’s why.
This knowledge was picked up by the ancient Babylonians.
That’s not exactly correct – we now know that there are about 365.25 days in a year.
Geography connections: Where was ancient Babylon?
Because of this, the ancient Sumerians and Babylonians used 360 and 60 as building blocks for their counting systems.
The Babylonians knew, of course, that the perimeter of a hexagon is exactly equal to six times the radius of the circumscribed circle, in fact that was evidently the reason why they chose to divide the circle into 360 degrees (and we are still burdened with that figure to this day).
A History of Pi, Petr Beckmann
That system then passed down to later Greek and Roman civilizations, Islamic civilizations, and then to the European and Asian civilizations.
We’re so used to using it that dividing a circle into 360 parts seems natural. But there’s nothing necessary or natural about this. We didn’t discover this – we defined this. It’s just a convention.
The degree is an arbitrary unit; basically any division of a circle would work as a system of measurement. The degree has the advantage that 360 divides evenly by 2, 3, 4, 5, 6, 8, 9 & 10 making it easy to mentally calculate an angle; indeed this is the major advantage of all old imperial units.
Ray Gallagher, Belfast, Northern Ireland
We could have chosen any other number. During the French Revolution there was an attempt to make a metric system version of angle measurement.
Metric right angles were defined as having 100 “degrees”
(obviously, these degrees were smaller than regular degrees.)
A metic circle would had 400 metric degrees instead of 360.
To avoid confusion these slightly smaller degrees were called gradians, or the gon grad.
360 degrees = 400 gradians
This system was used by some surveyors and engineers in Europe for some time. It is not common anymore. Here we see a French compass from 1922, divided into 400 degrees.
compassmuseum.com/diverstext/divisions.htm
From Compassipedia, part 2, the division systems.
In the end this new metric degree system didn’t catch on.
Using 360 is just easy for people to use. It is an abundant number, i.e. there are many factors. People find it easy to mentally divide the circle into 2, 3, 4, 5, 6, 8, 9, 10, 12, etc.
But there is one way to measure angles that is natural:
Radians
A radian is a special, natural angle.
There are a few equivalent ways of defining it:
the angle defined when the radius is wrapped round the circle’s perimeter
the angle defined when the arc length = radius
the angle subtended from the center of a circle which intercepts an arc equal in length to the radius of the circle. (this is the more complete, most accurate phrasing.)
Construct an angle of one radian
Know these abbreviations:
θ = subtended angle (in radians)
s = arc length
r = radius
We can measure any size angle, small or large, in radians.
The size of an angle θ, in radians = the ratio of the arc length to the radius of the circle
θ = s/r
Conversely, the length of the intercepted arc = radius multiplied by the magnitude of the angle
s = rθ
How does this relate to π?
The magnitude (in radians) of one complete revolution = 360 degrees
The magnitude (in radians) of one complete revolution = length of the entire circumference divided by the radius
1 revolution = (2πr / r) radians
1 revolution = 2π
Thus 2π radians = 360 degrees
Thus 1 radian = 180/π ≈ 57.295779513082320876 degrees.
What is π?
When a circle’s diameter is 1 then its circumference is π.
Distance halfway around a circle will be 3.14159265… Pi
When a circle’s radius is 1 – a unit circle – then its circumference is 2π.
Here we see a circle rolling out to 2π.
In calculus and physics, radians are usually more useful and natural to use than degrees.
Further lessons
Intuitive Guide to Angles, Degrees and Radians
Thanks for reading. While you’re here see our other articles on astronomy, biology, chemistry, Earth science, mathematics, physics, the scientific method, and making science connections through books, TV and movies.
Learning Standards
Math Common Core
Understand radian measure of an angle as the length of the arc on the unit circle subtended by the angle.
CCSS.MATH.CONTENT.HSF.TF.A.2
Explain how the unit circle in the coordinate plane enables the extension of trigonometric functions to all real numbers, interpreted as radian measures of angles traversed counterclockwise around the unit circle.
Derive using similarity the fact that the length of the arc intercepted by an angle is proportional to the radius, and define the radian measure of the angle as the constant of proportionality; derive the formula for the area of a sector.
Science of sci-fi movies and TV shows
Time to look at the Good, the Bad, and the Ugly, of science in movies and TV shows! 🙂
Science of sci-fi movies and TV shows
Ant-Man, Fantastic Voyage & Honey I Shrunk The Kids: Miniaturization
2001 A Space Odyssey & Babylon 5 – Artificial gravity in a space station
Batman The Dark Knight
Doctor Who
Godzilla vs the scaling laws of physics
Jurassic Park
Megalodon: The Monster Shark Lives
Mermaids: The Body Found
Star Trek: The physics of warp drive
Superman Returns (2006) – Calculating his strength
The Core (Earth Science & Physics ideas)
The Expanse, TV and books, Leviathan Wakes
Tremors (featuring Graboids)
Up – Buoyancy of balloons
Books
Insultingly Stupid Movie Physics
Hollywood’s Best Mistakes, Goofs and Flat-Out Destructions of the Basic Laws of the Universe
by Tom Rogers
Would the bus in Speed really have made that jump? -Could a Star Wars ship actually explode in space? -What really would have happened if you said “Honey, I shrunk the kids”? The companion book to the hit website (www.intuitor.com/moviephysics), which boasts more than 1 million visitors per year, Insultingly Stupid Movie Physics is a hilarious guide to the biggest mistakes, most outrageous assumptions, and the outright lunacy at work in Hollywood films that play with the rules of science.
Don’t Try This At Home!: The Physics of Hollywood Movies\
by Adam Weiner
A fresh look at the basics of physics through the filmmaker’s lens. It will deconstruct, demystify, and debunk popular Hollywood films through the scientific explanations of the action genre’s most dynamic and unforgettable scenes.
Websites
Intuitor: Insultingly Stupid Movie Physics
PHYSICS IN FILMS by Costas J. Efthimiou
Thanks for reading. While you’re here see our other articles on astronomy, biology, chemistry, Earth science, mathematics, physics, the scientific method, and making science connections through books, TV and movies.
Teaching ionic formulas with Legos as manipulatives
We can use giant Legos as manipulatives to teach students about ionic bonding formulas.
We can explore cation-to-anion ratios.
The blocks may represent trivalent, divalent, and monovalent cations and anions.
from “An Interlocking Building Block Activity
in Writing Formulas of Ionic Compounds”
You might be able to get them at low cost from a community yard sale group. Just label them yourself.
Ruddick and Parrill write
LEGO blocks provide excellent representations of ions, particularly because the blocks are color coded, and the valency of the ion can be represented by the number of “dots”, or raised knobs, on a brick. For example, a blue 1 × 3 brick (1 dot wide and 3 dots long) can represent cationic Al3+. The oxide ion, O2−, can be represented by a red 1 × 2 brick (1 dot wide and 2 dots long) (Figure 1). These two types of bricks can then be assembled to make a product that helps students determine the cation-to-anion ratio in aluminum oxide and write the chemical formula.
Materials
This is just one example. Mega Bloks.
References
JCE Classroom Activity #113: An Interlocking Building Block Activity in Writing Formulas of Ionic Compounds, Kristie R. Ruddick and Abby L. Parrill, J. Chem. Educ. 2012, 89, 11, 1436–1438, 9/19/2012
https://doi.org/10.1021/ed200513y
Related
Teaching chemistry with LEGO bricks
Ryo Horikoshi, Chemistry Teacher International, 12/21/2020
“Since LEGO bricks possess varieties of shapes and colors, they can be employed to design various teaching aids, including periodic tables, molecular models, polymer structure models, and frameworks for handmade measuring instruments. The polymeric structure models are generally difficult to build with typical ball-and-stick type molecular models; however, they can be easily built, employing LEGO bricks.”
DOI: https://doi.org/10.1515/cti-2020-0017
Thanks for visiting. See our articles on
Astronomy, Biology, Chemistry, Earth Science, Mathematics, Physics
Beyond immediate death count: Long Covid and blood clots: Covid-19 as a blood clot disease
Coronavirus disease 2019 (COVID-19 ) is caused by a virus. Its name is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2.) This is one of a number of respiratory viruses.
Myth: Covid only affects the lungs. And only about 0.5% of infected people get sick and die, so the rest of us will be okay.
Fact: Covid-19 is an endothelial blood clot disease as well as a pulmonary disease. Blood clots travel to all other organs in the body, including the brain, and can cause serious damage even in survivors. People are at least ten times more likely to get blood clots issues and neurological issues,than dying.
Many covid-19 survivors report painful and debilitating symptoms. Some report feeling like they were being suffocated. During these episodes their blood oxygen levels drop, which causes biochemical stress in many organs.
The death rate alone is staggeringly higher than what we normally see from influenza.
A death rate of .5% is higher than any other viral pandemic that has hit the United States since the Spanish flu, the 1918 flu pandemic. The United States of America has a population of over three hundred million people. Over eight hundred thousand Americans have already died due to this disease. If left unchecked, Covid-19 would kill millions Americans.
Deaths are just a small part of the coronavirus story: Covid-19 is an endothelial blood clot disease.
Many covid-19 patients have blood clots in the legs, lungs, and cerebral arteries leading to the brain. Likely in other locations as well.
Above image: formation of an occlusive thrombus in a vein.
Take blood clots seriously
Blood clots are no joke. They may lead to.
* strokes
* encephalitis (swelling of the brain)
* heart attacks
* inflammation of the heart
* deep vein thromboses in the legs
* clots in the lungs
* stroke-causing clots in cerebral arteries.
* pain, shortness of breath
* fatigue, dizziness due to lack of oxygen to the brain
* kidney failure
* degradation of kidney dialysis: clots can clog kidney dialysis machines.
Doctors have documented short term neurological damage in covid patients, even in some otherwise asymptomatic people.
It is likely that there is long-term neurological damage as well.
“If you start to put all of the data together that’s emerging, it turns out that this virus is probably a vasculotropic virus, meaning that it affects the [blood vessels],”
In a paper published in April in the scientific journal The Lancet, Mehra and a team of scientists discovered that the SARS-CoV-2 virus can infect the endothelial cells that line the inside of blood vessels.
Endothelial cells protect the cardiovascular system, and they release proteins that influence everything from blood clotting to the immune response. In the paper, the scientists showed damage to endothelial cells in the lungs, heart, kidneys, liver, and intestines in people with Covid-19.
– Covid-19 May Be a Blood Vessel Disease, Dana G. Smith
How covid-19 attacks the brain
John Hamilton writes
Many patients who are hospitalized for COVID-19 are discharged with symptoms such as those associated with a brain injury….
COVID-19 also appears to produce many other brain-related symptoms ranging from seizures to psychosis, a team reports in the Jan. 5 issue of the journal Alzheimer’s & Dementia…. it may even increase a person’s risk of developing Alzheimer’s disease.
For many affected patients, brain function improves as they recover. But some are likely to face long-term disability, de Erausquin says.
… “What we found was that the very small blood vessels in the brain were leaking,” Nath says. “And it wasn’t evenly — you would find a small blood vessel here and a small blood vessel there.” The injuries resembled those from a series of tiny strokes occurring in many different areas of the brain, Nath says.
How COVID-19 Attacks The Brain And May Cause Lasting Damage, Jon Hamilton
Conclusions
Many covid-19 survivors may die many years or decades earlier than they otherwise would have, due to the blood clots and endothelial damage.
The full death toll of Covid-19 will likely be many times higher than the current toll. As 1/2022 over 839,000 Americans have died. It is certain that that over the coming years and decades many more people will die from their covid-19 damage. As such, we should be diligent in protecting ourselves, our loved ones, and everyone in our communities.
How to protect ourselves
Gather knowledge, e.g. Covid 19 is an airborne virus
Wearing masks in certain situations – Unmasking mask myths
Note that vaccinated people can be protected yet still transmit covid-19.
Social distancing
Washing hands
Zinc supplements and coronaviruses, rhinoviruses, common cold
Getting a covid-19 vaccination
Covid-19 Vaccine Tracker, Bloomberg
High effectiveness of covid-19 vaccines, breakthrough cases and the base rate fallacy
References
High effectiveness of covid-19 vaccines, breakthrough cases and the base rate fallacy
What Does COVID Do to Your Blood? John Hopkins Medicine, Panagis Galiatsatos, M.D., M.H.S. and Robert Brodsky, M.D.
Covid-19 May Be a Blood Vessel Disease, Which Explains Everything, Dana G. Smith, Elemental, 5/29/2020
How COVID-19 Attacks The Brain And May Cause Lasting Damage, Jon Hamilton, Shots: NPR Health News, 1/5/2021
Microvascular Injury in the Brains of Patients with Covid-19 Letters, New England Journal of Medicine, Myoung-Hwa Lee et al, DOI: 10.1056/NEJMc2033369
The chronic neuropsychiatric sequelae of COVID‐19: The need for a prospective study of viral impact on brain functioning, Gabriel A. de Erausquin et al, Alzheimer’s & Dementia [journal,] 1/5/2021, https://doi.org/10.1002/alz.12255
Our Covid-19 articles
Respiratory viruses (influenza, rhinoviruses, coronaviruses etc)
How do viruses spread? Airborne vs non-airborne
Beyond immediate death count: Long Covid and blood clots: Covid-19 as a blood clot disease
High effectiveness of covid-19 vaccines, breakthrough cases and the base rate fallacy
How vaccinated people can be protected yet still transmit covid-19
Vaccines – what does 95% efficacy actually mean?
Simple DIY masks could help flatten the curve. We should all wear them in public.
Unmasking mask myths
Why teachers are skeptical about standardized tests
Why are many teachers skeptical about standardized tests? Why do many parents and teachers wants us to reduce our reliance on mandatory high stakes testing, like the Massachusetts MCAS exam, New York Regents exam, Texas STAAR, etc.? Why not just continue to insist on them?
In response to questions like these, Jeff Bigler writes
Often, that kind of sentiment comes from districts where students perform well on the tests. The problem with the tests is that they end up increasing the very achievement gap that they’re purported to reduce. Let me start with an example:
This is a story about three AP teachers. Granted, AP is not the same as MCAS, but it is also a high-stakes (at least for college-bound students) standardized test.
The first teacher is from a wealthy district. That teacher’s students all earned scores of 4 & 5.
The second teacher is from a middle middle class district. One-third of the second teacher’s students earned passing scores (3 or higher). None of that teacher’s students received a 5 (over a three-year period).
The third teacher is from an economically disadvantaged district. Only about 1% of that teacher’s students earned passing scores.
If you’re like most people, you would conclude that the first teacher is the best of the three, and the third is the worst, and that the best course of action is to fire the third teacher and incentivize the first teacher to teach in the third school.
However, all three of those teachers are the same person: me. Moreover, I taught in the wealthy district (Belmont) first, the middle middle class district second (Waltham), and the economically depressed district third (Lynn).
If anything, because of having more experience, I am a better teacher in Lynn than I was in either Belmont or Waltham. Those students in Lynn are getting the benefits of a teacher from a wealthy district whose students successfully earned high scores—those same benefits that are supposed to magically transform them into high-achieving scholars instantaneously.
What happened? Nothing. The students in Belmont were academically superior because their families made sure to educate them from the time they were babies. It’s like compound interest—students who have more academic capital invested from an earlier date get more returns. I could have stood in front of the Belmont kids picking my nose for 180 days and they would have done just as well, either on their own or because their parents would have hired tutors.
The kids from Lynn may have been well cared for in daycare, but for most of them, education didn’t really start until kindergarten. Both of their parents worked. (And in many cases, their parents spoke no English and never went to high school.) Many of my students have to figure out everything for themselves with no help other than from their teachers, and often while caring for younger siblings and sometimes even for their parents.
Now back to MCAS. In the 1990s, when Massachusetts created the standards that MCAS would be based on, they looked at the average developmental level of students across the state, and made that the minimum.
This means fully half of the children (the ones who were below average) were now being required to perform at a level beyond their developmental level. Of course, the averages are statewide; more of the children in poorer communities are being required to work beyond their developmental level than in wealthier communities.
When students are required to “learn” something before they are developmentally ready (because it’s on MCAS, and schools are punished based on MCAS scores), all their teachers can do is teach them procedures that generate the right answers. So the children dutifully learn those procedures.
They get the right answers, but those procedures can’t really be used as building blocks, and the students forget them shortly after learning them. So everything needs to be reviewed every year, and students are not learning in a way that they retain long-term.
This problem compounds itself every year. By the time they get to my physics class in 11th and 12th grade, many of my students can’t do basic Algebra 1 problems even though they had to pass Algebra 2 in order to take my class.
Children from economically depressed areas are also much more likely to form strong attachments to their teachers. The ones who live in abusive homes often develop a high level of empathy – it’s a coping mechanism that helps them protect themselves by sensing when it’s time to hide.
Those children have a heightened sense of their teachers’ stress about the test, and they worry that if they fail, they will be the cause of the one stable adult in their life getting fired.
Small wonder that those kids are so anxious that they throw up on the tests or take dangerous levels of ADHD medications—in their minds they are performing heroic actions to save their teachers. I cling to the vain hope that one day we will have a commissioner of education who understands child development and is trauma-informed. But I’m not going to hold my breath.
Related articles
Here’s a great example: Sara Holbrook, a poet, found that even she couldn’t even answer questions about her own work on a Texas state standardized exam because the questions are so poorly conceived. Valerie Strauss 1/7/2017, The Washington Post,
Poet : I can’t answer questions on Texas standardized tests about my own poems
I Can’t Answer These Texas Standardized Test Questions About My Own Poems
Standardized Testing Misses The Mark When It Comes To Student’s Cognitive Competency. The truth is, learning, insight, intellectual development are not quantifiable. By George Popham, Bay State Learning Center
Standardized Testing Misses The Mark When It Comes To Student’s Cognitive Competency
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Helium cycle
On Earth, the production of new helium is result of radioactive decay.
Helium is found in large amounts in minerals of uranium and thorium.
About 3,000 metric tons of helium are generated per year throughout the lithosphere.
Earth’s crust [He] =8 parts per billion
Seawater [He] = 4 parts per trillion.
Earth may gain He atoms from outer space, from cosmic rays
Most He in Earth’s atmosphere escapes into space by several processes.
Near Earth’s surface, the average KE of He atoms is not enough for them to escape Earth’s gravitational field.
In the exosphere, He atoms have a greater KE, so some do escape.
Much 3He leaves Earth in this way. Some 4He leaves in this way.
Some He undergoes photoionization by the polar wind. This then escapes along open lines of the Earth’s magnetic field.
Some He goes into space due to direct interaction of the solar wind with the upper atmosphere.
This occurs during the short periods of lower magnetic-field intensity while the Earth’s magnetic field is reversing.
talkorigins.org Helium gas discussion
Learning Standards
Next Generation Science Standards
HS-LS2-4. Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.
A Framework for K-12 Science Education Practices, Crosscutting Concepts, and Core Ideas (2012)
LS2.B: Cycles of Matter and Energy Transfer in Ecosystems
College Board Standards for College Success: Science
Standard ES.4 – Cycles of Matter and Energy: Matter on Earth is finite and moves through various cycles that are driven by the transformation of energy
LS.4.1 Matter Cycling – Students understand that matter is continuously recycled within the biological system and between the biological (biotic) and physical (abiotic) components of an ecosystem.
ESH-PE.4.2.2 Construct a graphical representation of the global carbon cycle (or the cycle of some other element or molecule), and use this representation to predict the effects of some environmental change (e.g., evolution of life, tectonic change, human activity) on carbon cycling (or the cycling of some other element or molecule).
Enduring Understanding 3A – Biogeochemical cycles are representations of the transport, transformation and storage of elements on a local, regional or global scale.
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Hydrogen cycle
Like carbon, nitrogen, and phosphorus, there is also a cycle of hydrogen here on Earth. Hydrogen atoms move between biotic (living) and abiotic (non-living) sources.
Hydrogen (H) is the most abundant element in the universe.
On Earth, common H-containing inorganic molecules include water (H2O), hydrogen gas (H2), methane (CH4), hydrogen sulfide (H2S), and ammonia (NH3).
Organic compounds contain H atoms (as well as C.)
The chemistry of the Hydrogen cycle is highly relevant to the development of life on Earth and mostly likely elsewhere in space.
Hydrogen fuels rockets, but what about power for daily life? We’re getting closer. Phys.Org
Image from, Development and testing of new materials for high temperature PEM water electrolysis, Antonio Luis Tomas-Garcia
Where does our H2 come from? (sources)
biological processes in the oceans
biological (microbial) processes in soils
photochemical production in the troposphere via CH2O also written as H−CHO, formaldehyde.
Where does the H2 go? (sinks)
soil uptake
photochemical destruction in the troposphere by OH radicals
Free H2 can then be consumed by other microbes, oxidized photochemically in the atmosphere, or lost to space.
Cycling: H2 molecules usually exist within the atmosphere for 4 to 7 years before they get taken up in a soil sink.
Hydrogen production and leakage
As we develop hydrogen based industries, in what ways will we be producing, distributing, and using hydrogen? In what ways will hydrogen leak out into the atmosphere?
In the left column we see H2 production.
In the middle column we take into account the fact that once H2 gas is made, it needs to be distributed by trucks, ships, cargo trains, etc.
In the third column we see H2 being used by end-use customers.
Notice that in every step some H2 gas leaks out. Leaks are unintended, and unavoidable. We can minimize them but they will never be zero.
image from, Emission scenarios for a global hydrogen economy
Possible effect on ozone layer
“Increased atmospheric emissions of hydrogen will therefore inevitably lead to increased levels of water vapour in the stratosphere which will in turn lead to increased stratospheric cooling. This cooling may change the distribution of polar stratospheric clouds which play an important role in the formation of ozone holes and hence may delay the recovery of the ozone layer.”
A mitigating factor is that “The potential environmental risks from the hydrogen economy were found to be small in comparison with the environmental benefits. ” …. “the few available studies all point to the impact of large potential hydrogen leakages on the stratospheric ozone layer as being small”
– Hydrogen for Heating: Atmospheric Impacts – A literature review
Possible effect on global warming
Hydrogen gas indirectly acts as a greenhouse gas because it interferes with the global chemical reactions which control the methane levels and the formation of ozone.
Methane and ozone are the second and third most important greenhouse gases after carbon dioxide.
There is still much uncertainty about how much H2 gas would affect global warming, although the effect is currently considered to be very small.
– Hydrogen for Heating: Atmospheric Impacts – A literature review,
Possible effect on air quality
H2 is relatively inert. It offers almost no chemical reactivity with urban pollutants such as NOx, O3, SO2, CO, VOCs and suspended particulate matter. Thus it has no direct influence on urban air quality.
However, because of its reaction with hydroxyl radicals: OH + H2 → H2O + H it plays a weak role in the long-range transport of photochemical ozone. This may affect ozone levels in the lower atmosphere, although the effect is currently estimated to be very small.
Caution in relying on Hydrogen power
Using hydrogen as a source of power for vehicles certainly has its drawbacks—among them the cost and the inefficient use of energy—but researchers are now warning against hydrogen for another reason, The Guardian reports: scarcity and a subsequent dependence on fossil fuels….
“Hydrogen-based fuels can be a great clean energy carrier, yet their costs and associated risks are also great,” said Falko Ueckerdt, at the Potsdam Institute for Climate Impact Research (PIK) in Germany, who led the research.
“If we cling to combustion technologies and hope to feed them with hydrogen-based fuels, and these turn out to be too costly and scarce, then we will end up burning further oil and gas,” he said. “We should therefore prioritise those precious hydrogen-based fuels for applications for which they are indispensable: long-distance aviation, feedstocks in chemical production and steel production.”
The research, published in the journal Nature Climate Change, calculated that producing and burning hydrogen-based fuels in home gas boilers required six to 14 times more electricity than heat pumps providing the same warmth. This is because energy is wasted in creating the hydrogen, then the e-fuel, then in burning it. For cars, using e-fuels requires five times more electricity than is needed than for battery-powered cars.
text above from Researchers Warn Against Becoming Too Dependent On Hydrogen To Power Cars Elizabeth Blackstock, May 2021, Jalopnik
Using hydrogen fuel risks locking in reliance on fossil fuels, researchers warn Damian Carrington, 5/6/2021, The Guardian (UK)
Potential and risks of hydrogen-based e-fuels in climate change mitigation Falko Ueckerdt et al., Nature Climate Change volume 11, pages384–393(2021)
Hydrogen Production and Distribution Alternative Fuels Data Center, US Dept. of Energy,
Some critics of Hydrogen power
The government’s embrace of ‘clean hydrogen’ helps no one but the fossil fuel industry, Richard Denniss, The Guardian , 5/2/2021
External articles
Atmospheric researchers present new findingson the natural hydrogen cycle. CalTech
Assessing Leaks in a Global Hydrogen Infrastructure: Can it Perturb the Natural Hydrogen Cycle?
Leaked hydrogen fuel could have small negative effects on atmosphere
Hydrogen fuel could widen ozone hole
Global Environmental Impacts of the Hydrogen Economy
Hydrogen Effects on Climate, Stratospheric Ozone, and Air Pollution
Impact of a possible future global hydrogen economy on Arctic stratospheric ozone loss, with graphic
What Are The Pros And Cons Of Using Hydrogen To Generate Electricity?
The Hydrogen Hoax , The New Atlantis, by Robert Zubrin
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References
Bas van Ruijven et al., Emission scenarios for a global hydrogen economy and the consequences for global air pollution, Global Environmental Change, Volume 21, Issue 3, 2011, Pages 983-994,
Hydrogen for Heating: Atmospheric Impacts – A literature review, BEIS Research Paper Number 2018: no. 21, Dept. for Business, Energy and Industrial Strategy, UK
Learning Standards
Next Generation Science Standards
HS-LS2-4. Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.
A Framework for K-12 Science Education Practices, Crosscutting Concepts, and Core Ideas (2012)
LS2.B: Cycles of Matter and Energy Transfer in Ecosystems
College Board Standards for College Success: Science
Standard ES.4 – Cycles of Matter and Energy: Matter on Earth is finite and moves through various cycles that are driven by the transformation of energy
LS.4.1 Matter Cycling – Students understand that matter is continuously recycled within the biological system and between the biological (biotic) and physical (abiotic) components of an ecosystem.
ESH-PE.4.2.2 Construct a graphical representation of the global carbon cycle (or the cycle of some other element or molecule), and use this representation to predict the effects of some environmental change (e.g., evolution of life, tectonic change, human activity) on carbon cycling (or the cycling of some other element or molecule).
Enduring Understanding 3A – Biogeochemical cycles are representations of the transport, transformation and storage of elements on a local, regional or global scale.
Birds
Definition of birds
Birds are a group of warm-blooded vertebrates
They are characterized by the presence of feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
Birds live worldwide; range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. There are about ten thousand living species.
Evolution of birds
Almost all dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years.
Almost all branches of the dinosaur family tree died out, except for the branch with small feathered dinosaurs. That branch proliferated and developed into the birds that we know today.
Zina Deretsky, National Science Foundation. Air sac system of birds and of Majungasaurus.
This infographic is one way to show the relationship between various forms of dinosaurs.
It illustrates that today’s birds are the last remaining branch of the dinosaur family tree.
Image by Shawn Gould and Jen Christiansen, from How Dinosaurs Grew So Large—And So Small, John R. Horner, Kevin Padian and Armand de RicqlèS
Scientific American 293, 56 – 63 (2005)
Groups of birds
Raptors, also known as birds of prey, are birds that primarily hunt and feed on vertebrates, and that are large relative to the hunter.
Raptors have keen eyesight for detecting food at a distance or during flight, strong feet equipped with talons for grasping or killing prey, and powerful, curved beaks for tearing flesh.
The term raptor is derived from the Latin word rapio, meaning to seize or take by force.
In addition to hunting live prey, many birds, such as fish eagles, vultures and condors, eat carrion.
Condors are under vultures, in the order of Cathartiformes.
Notice that raptors, like reptiles, are not a true clade.
“There’s No Such Thing As Reptiles Any More – And Here’s Why”
Phylogeny of core landbirds modified from Mindell et al. (2018). The shaded box encompasses the raptorial grade (see text), within which we propose that all orders are considered raptors. Raptors as a group is paraphyletic and mostly share the raptorial lifestyle passed down from their single common ancestor.
Such grouping assumes then that the raptorial lifestyle was lost twice independently with the ancestors of both the Coraciimorphae and Passeriformes/ Psittaciformes clades.
Commentary: Defining Raptors and Birds of Prey
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Learning Standards
Benchmarks for Science Literacy, American Association for the Advancement of Science
Students should begin to extend their attention from external anatomy to internal structures and functions. Patterns of development may be brought in to further illustrate similarities and differences among organisms. Also, they should move from their invented classification systems to those used in modern biology… A classification system is a framework created by scientists for describing the vast diversity of organisms, indicating the degree of relatedness between organisms, and framing research questions.
Evolution and diversity: Origin of life, evidence of evolution, patterns of evolution, natural selection, speciation, classification and diversity of organisms.
Teaching About Evolution and the Nature of Science, National Academy Press (1998)
Biological classifications are based on how organisms are related. Organisms are classified into a hierarchy of groups and subgroups based on similarities which reflect their evolutionary relationships. Species is the most fundamental unit of classification.
Measuring mass in the metric system
In science and engineering we often have to make measurements of mass. Now, I understand that a lot of American students have affinity for the traditional English system of measurements.
But we can’t make much progress in any field of science or engineering without first becoming conversant with the metric system. It is used worldwide.
How do we measure mass? To learn practical, hands-on skills, see our lesson here.
Measuring mass with a triple beam balance
But in this lesson we’re going to get a feel what various masses would actually look like in real life.
Kilograms
A kilogram is 1,000 grams. It is abbreviated as kg.
Can we convert between kilograms and pounds…. not quite [TBA]
But if all measurements are done here on Earth then 1 kg of mass has a weight of about 2.2 pounds.
Here’s a 1 kg steak dinner
image from TripAdvisor, Outback Steakhouse, Las Vegas Blvd
How can we visualize this? About the mass of a liter bottle of water or soda.
About the mass of good size hardcover book. About the mass of a quart of Gatorade.
Or about the mass of an adult Black-Footed Ferret.
Grams
A metric unit of mass is the gram abbreviated as g.
What kind of things are about a gram in mass?
Centigrams
Centi means 1/100th 0.01 10-2
A smaller metric unit of mass is the centigram abbreviated as cg.
It is one one-hundredth of a gram.
What kind of things are about a cg in mass? Many medications come in 1 cg size, although they more often are measured as 100 mg. Here are magnesium supplement pills.
When a pencil tip breaks, a bigger piece could be about 1 cg.
(We could name something that has a mass of gram and divide it in ten pieces)
milligrams
milli means 1/1000th 0.001 10-3
This is 1/1000th of a gram.
What kind of things are commonly measured in milligrams?
Many doses of medications are measured in milligrams:
Amitriptyline (Elavil) treats chronic pain and depression.
Atorvastatin (Lipitor) treats high cholesterol.
Amlodipine (Norvasc) treats high blood pressure and angina.
Here is crushed powder of a medication shown next to a penny for comparison.
Penny, 1 mg, 10 mg, 25 mg
Micrograms
Yet even smaller is the microgram abbreviated as μg
micro means 1/1,000,000th 0.000001 10-6
Just one one-millionth of a gram
What kind of things are commonly measured in micrograms?
Grains of sand are around 30 to 50 micrograms.
Mass of a grain of sand
Nanograms
Abbreviated as ng.
nano means 1/1,000,000,000 th 0.000000001 10-9
Imagine cutting a raisin into a billion pieces. Each of those tiny pieces has a mass of about one ng.
What kind of things are about a nanogram in mass?
A human cell or a grain of birch pollen. Note that in this picture, each dot that you can see is likely dozens of pollen grains stuck together.
Each individual grain by itself is so small that you’d need a microscope to clearly see it.
Nanograms are very small compared to anything we see in our daily lives, but they are large compared to a single atom
Chemistry math & mass problem
How many atoms of iron (Fe) are in 1 ng (1.0 x 10-9 g) of iron?
This problem from xaktly – Chemistry – The Mole.
We start by finding the molar mass of iron from the periodic table. It’s 55.85 g/mol.
We use the molar mass to convert to moles.
Then multiply by 6.022 x 1023 atoms per mole to get the number of atoms.
1 ng of iron atoms is about 1 x 10 ^ 13 atoms!
That’s 10,000,000,000,000 atoms.
Videos
Powers of Ten and the Relative Size of Things in the Universe
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