Jamaica – the other kind – and a healthy heart

Jamaica Drink

Flowers can be good for more than beauty. I learned about this one while living in a farm valley in Northern California. Summers were very hot, shimmering heat trapped between the surrounding mountains. Farm laborers worked the vegetable fields, hoeing and weeding, then harvesting the crops. They wore long sleeves and covered their heads with hats, fabric falling down from the brims to cover their necks. This was to keep from sunburn. Alongside, narrow roofed wagons provided resting stations with benches. There was also a large thermos for a refreshing drink. More often than not, the thermos was full of a bright red drink, Jamaica (pronounced hahMYca).

The farm workers were often from Mexico and they were often interested in picking up paid work on the side, after their duties in the field were finished. I was introduced to Pablo and Jesus in this way. These gentlemen trimmed the trees in my walnut orchard and mowed my grass. They became friends. And they showed me how to make Jamaica, a refreshing and healthy drink that quenches thirst and lowers blood pressure. I began drinking it regularly and served it to them when they came to my house. It was a godsend in the heat, but healthy anytime.

Jamaica is a species of hibiscus that grows in the hot arid climate of Mexico. The red flowers are steeped in hot water, just like any other tea. The water turns a beautiful red and has a slightly tart, refreshing taste. You can buy jamaica in most Mexican groceries and in some health food stores. In Mexican groceries, it is often seen loose-leaf (although it is really a flower) in huge bins, sold by the pound.

As found in markets: dry Jamaica blossoms

Recipe for Jamaica Tea

One handful of dried Jamaica blossoms, tossed into…

one-half gallon very hot water

Let steep for thirty minutes.

Notes on recipe: Where I lived, it was so hot that I usually made sun tea by adding a handful of blossoms to a large glass jar of water. I’d let it sit in the hot sun most of the day. Then I’d cool it. I prefer to drink jamaica cold, because I think it’s more refreshing, but hot tea is fine. Sugar or not? Some people add sugar to their jamaica tea. I preferred the natural tart taste; and it’s more healthy that way.

Health benefits: Jamaica tops some lists of foods that lower blood pressure. My doctor gave me such a list when she discovered my blood pressure was slightly elevated, and jamaica was listed number one. High blood pressure causes all sorts of problems including heart attack and stroke. Lowering it through frequent drinking of jamaica was very pleasant. Jamaica is also high in vitamin C and anti-oxidants. Drinking the tea also keeps you hydrated, which benefits all body systems.

Cultural Notes:

Jamaica is a favorite drink in many countries. I saw it for sale by Afghan street vendors, as well as on the streets of Cairo, Egypt. West and east African countries, Caribbean countries, Asia countries…it is a part of all their cultures although it goes by different names. If you want to try one tradition, here are two recipes I’ve adapted from traditional Christmas foods served in the country of Jamaica: hibiscus tea and sweet potato wedges.

Sorrel Drink (dried hibiscus blossoms are known as Sorrel in the country of Jamaica):

Prepare tea as for Jamaica (above), but add 2 TBSP ginger before steeping. Another version calls for mixing the steeped tea with purple grape juice. Yummy and doubly healthy.

Sweet Potato Wedges

Wash and slice sweet potatoes into wedges. In a large bowl, toss the wedges with just enough olive oil to lightly coat. Add a sprinkling of salt and pepper and 1 tsp paprika. Spread wedges on a nonstick tray and bake in the oven at 350 degrees for 30 minutes or until tender when pierced with a fork.

Popcorn and Steam Power

Students in Afghanistan learn about popcorn


I like to start this lesson with an electric skillet, an extension cord, and an old sheet spread on the floor. Put the electric skillet atop the sheet and turn it on high. Children can sit around the sheet (not on it) and observe the action. The sheet keeps the floor clean and provides a safety boundary.

Observe what happens to water when it gets hot. Once the skillet is hot, use an eye dropper or straw to add a drop of water to its surface. It’s more dramatic to add the drop from a height above the skillet. Students usually delight in the sound of the hissing water and the sight of the water sizzling and disappearing. What happened to the water? Where did it go? Students often want to see this repeated several times. You might want to add a larger amount of water on subsequent demonstrations so they can watch it for a longer time.

Explain to students that heat causes the water to expand to the point where it bursts and turns into steam. I like to draw a slo-mo cartoon of this on the board: a spherical drop of water hitting the hot surface, growing larger…and larger…and bursting like a firecracker. Energy is released when the drop turns into steam.

The energy released with a single drop of water isn’t much, but the energy released with large amounts of water can be quite large. This energy has been used to power large machines. Show children pictures of steam trains, large ocean-going ships, boilers on tug ships. Find the heat source and the boilers on these pictures.

Popcorn. Give each child a kernel of unpopped popcorn. Ask them to describe its shape, size, texture, smell, even the sound it makes when dropped onto a hard surface. Some children may have only popped corn in a pouch and never seen what unpopped kernels look like. Have they ever popped corn at home? How did they do it? (they heated it in various ways). What causes popcorn to pop? Why doesn’t corn on the cob pop? There’s something different about popping corn, but it’s clear that heat is involved.

Demonstration: add a small amount of corn oil to the hot electric skillet. The oil helps spread the heat around the kernels. Then add one or two popcorn kernels. Keep the number of kernels small to allow the students to concentrate. Observe the kernels closely. They may begin to jiggle; then pop. Ask the students again why they think the popcorn popped. After waiting for answers, you might suggest there is something inside the kernels that explodes when it gets hot. Return to the previous demonstration about steam. Inside each kernel is a small amount of water. When it gets hot, it turns to steam with an explosion, causing the kernel to pop inside out. Another factor is the tough skin on the outside of the kernel, which holds the water in place until it is heated sufficiently to explode the kernel.

Enjoy: Add more oil if necessary, then add enough popcorn to serve the entire class. Leave the lid off the electric skillet for maximum fun. Stir the popcorn as it heats, to keep it from burning. Instruct the students to keep off the sheet, and to not pick up any popped corn. It will be hot! The teacher or parent can collect all the popped corn from the sheet when the skillet is empty. As the corn pops, think of the power released. Watch the height and distance the corn travels when it leaves the skillet. After the corn has popped, compare it to the unpopped corn the students had at the beginning. How has it changed?

Connections to other cultures and history:

Corn cobs with remnants of popped kernels have been discovered in the mountains of Peru, dating from approximately 6000 years ago. That corn was probably discovered accidentally when roasting cobs directly over the fire. Ancient Peruvians may have begun selecting and saving kernels of this type of corn for later planting. Ancestors of today’s Pueblo Indians knew how to pop corn. Popped corn dated from 1000 years ago was found in a cave in Utah where they lived. By some accounts, it was popcorn that native Americans offered to European pilgrims upon their arrival in the Americas.

Ancient Popped Corn cob found in Peru

Street vendors in Afghanistan and India use an unusual method of heating their popcorn: roasting it in skillets of sand set over a fire. I encountered this method while traveling in Afghanistan and at first could not believe what I saw. But my friends insisted it was true, allowing me to touch the cooled sand in the skillet – to the amusement of the street vendor. The popped kernels rise to the top of the sand and are cleansed of it by shaking the kernels through a strainer. In fact, further research on my part has led to my discovery that Iroquois Indians heated their popcorn in this way. French Canadian explorers were served the popcorn fresh, and in popcorn soups.

Street vendor cooks popcorn in sand

Make a Sundial Part II

Materials needed: face plate (made in Sundial part I), protractor, glue, BBQ skewer, cardboard scrap, cardboard rectangle large enough to hold sundial/BBQ skewer arrangement

Now that you have made the face of the sundial, you need to set it. That requires two pieces of knowledge about where you live. In this brief lesson, we will discuss your latitude.

You can find your latitude by googling “latitude your town“, or you can check a map. The face plate of your sundial must be angled to that same angle. There are a number of interesting ways to make this happen depending on your sundial design. For instance, I have made jiffy sundials from folded postcards of the place I’m visiting. Here is one easy way to use your latitude angle:

  1. Make a hole in the very center of your sundial face with a thumbtack.
  2. Insert a BBQ skewer, having a tight friction fit. The skewer will be your gnomon. The gnomon casts the shadow. “Gnomon” is Greek meaning one who knows.
  3. Prop the other end of the BBQ skewer against a triangle which you cut from cardboard. The triangle will be a right triangle (one angle is 90 degrees) with your latitude angle positioned as shown in the drawing below. Make sure you have the triangle positioned correctly. Apply a strip of glue to the triangle and glue it to the skewer. Optional: Leave a small extending point below the triangle. You can use this small point to stick the skewer into a slab of cardboard as a base for your sundial and move it around more easily.
  4. For example, my latitude in San Francisco is 38 degrees. See the drawing to look at the correct angle position.
  5. The friction fit of the skewer in the face plate will hold the face plate at the correct angle. The friction fit will also hold the skewer at a 90 degree angle to the face place – which is necessary for correct shadow casting. You can double-check that 90 degree angle by putting a square piece of cardboard under the gnomon.
Setting the latitude angle

There is one more step: finding true north. That will be addressed in the next lesson. Apologies for the simple sketch; I will replace it later with a photo.

Make a Working Sundial Part 1

The shadows sweeping across a sundial’s face tells far more than the time. It marks our latitude and longitude, tells us our position in relation to Polaris the North Star, whether the sun has passed through an equinox, and whether the sun is near its zenith in mid-summer or has dropped to its lowest arc in the heart of winter.

Most of us can delight in the knowledge that we have lassoed the sun for a clock when we make a sundial. Even children in kindergarten laugh to see how a shadow marks the hour for recess or a snack. But the study of sundials can pull you deeper and deeper into joyous realms of knowledge: astronomy, geometry, seasons and equinoxes, magnetishm and the north pole, art and poetry, latitude and longitude, time telling around the world, carpentry.

Shadow and sun clocks have been in use over many parts of the world thousands of years. Ancient examples in Babylonia and Egypt were mere sticks in the ground. These sticks evolved into great obelisks, sun temples, sundials, navigational tools, implements used in solstice rituals, and timepieces for the common citizen. Sundials graced buildings, gardens, wrists, necks, fingers and even gravestones. Until the 1700’s, sundials were relied upon for accurate time, and helped navigators find their way across endless oceans.

You can make a sundial that tells accurate time. It will give you correct solar time, without the fudge factors built into modern watches or cellphones to make our lives more standardized. The directions included in this series of sundial lessons will teach you how to correlate true sun time with modern devices. But it is always the sundial that is correct; your cellphone or computer that is off!

The subject matter is simply too great for one lesson, so I have divided it into several. But you’ll want to get started now, because this equatorial sundial does something special on the equinoxes and one is just around the corner on March 21.


Protractor, 4″ (approx) square card stock or cardboard, pushpin, crayons or colored pencils (optional but nice), pencil, pen

Make the Sundial faces. I have put all the photos below, to make reading faster.

  1. Use a pencil to lightly draw two diagonal lines across the card stock to locate the middle. Mark that point neatly but darkly because it will be your beginning point. The diagonal lines will not be used further.
  2. Use a push pin to make a hole through the center point.
  3. Drop a noon line from the center point to the “bottom” of your square. This line must be exactly perpendicular to the bottom edge, or your sundial will not work. Remember, a perpendicular line will have a 90 degree angle. Use a protractor for this step.
  4. Use a protractor to measure 15 degree angles on either side of the noon line. These are the hours lines (photo will help). Mark 9 angles/hour lines on each side of noon, but do not label them yet. Do the same thing on the other side. The noon line must drop to the same edge on both sides. Read these notes first:
    1. Note 1: Why 15 degrees? If the sun travels 360 degrees during a 24-hour day, you divide 360 by 24 to find that the sun travels 15 degrees each hour.
    2. Note 2: Draw as many hour lines as daylight would permit on each side. For instance, you’ll probably need 6 hour lines on each side of the noon line during the winter, (6 a.m. to 6 p.m.) but you will need more during the summer.
    3. Note 3: There are two sides to this protractor because one side is read during summer and the other side read during winter. More on this later; just draw the hour angles now.
    4. I have shown how to use two types of protactor to draw these lines. Since many students have difficulty using the standard protractor, my husband and I patented another type of protractor and that one is deep red. You can obtain one of these protractors by contacting me, but the standard protractor can be used.
  5. Label one face “Summer” and the other “Winter”. The photos will provide other labels you need to add. The labels may seem to be reversed but do as shown.
  6. Now label your hours as shown below on each face. Again, the hours may appear to be reversed but they won’t be once you orient your sundial in a later step of the lesson.
1. Mark center point
2. Draw Noon Line with Barry Protractor
2. Alternate: Draw noon line with standard protractor
Noon line completed
Hour lines: Mark first hour line with Barry Protractor. One edge of the protractor is aligned with noon line.
Add more hour lines by swiveling Barry Protractor. Keep one edge of protractor lined up with noon line as you do so.
Continue swiveling protractor to add more hour lines
Move Barry protractor to the other side of noon line and add more hours as before. Remember to keep one edge of protractor aligned with noon line.
15 degree hour lines on either side of noon line. Not all hour lines are drawn.
Alternate: Using standard protractor, mark 15 degree hour lines on either side of noon line and connect. You may need to move protractor to add all the hour lines you need.
Label one side as above. Decorate if desired.
Flip the card to the back side and label as shown above. Remember to drop the noon line to the same edge on both side.

Get Off the Earth!

I absolutely love this geometric puzzle, which I first discovered when reading a book by Martin Gardner. Martin Gardner, in turn, had been introduced to me by my husband David. Martin Gardner was a long-time contributor to Scientific American; he wrote about mathematic and scientific curiosities. Such things were fun for my husband, and myself. I hope you’ll enjoy this puzzle as much as we did!

Sam Loyd Puzzle Get Off the Earth

Sam Loyd was a chess player and puzzle creator at the turn of the 20th century. Some of his puzzles, such as Get Off the Earth, were sold as novelty items. Count the number of Chinamen on the puzzle above. You’ll see the arrow is pointed to “NE” on the globe. Then rotate the arrow to “NW” and one of the Chinamen has disappeared. Where did he go?

You can recreate this puzzle by printing and cutting out the two pictures below and assembling them with a brad.

This is a type of vanishing puzzle. Parts of the 13 original Chinamen have been cunningly redistributed so that there are only 12 when you rotate the circle. It helps understand this if you take some playdough and create 13 worms. Then distribute parts of the 13th worm over the remaining 12 worms.

Here are some other examples vanishing puzzles using the same principle.

10 eggs here…
How many eggs now?
and how many eggs now?

One practical application of a vanishing puzzle might occur to you when the airport clerk says you have too many pieces of luggage. “You’ll have to pay an additional $200 for that 5th piece of luggage…unless you can divide its contents among the other 4.”

Science yields clues to an ancient salt mine

Two Experiments Help Solve a Mystery

“Residents mined and traded salt” The sign offered little information, but I wanted to know more. Ruins of an ancient Anasazi settlement were huddled into a cliff above a sinkhole full of green water and leeches. “Where did they mine salt?” I asked a ranger. He directed me to nearby Camp Verde. “Look for Salt Mine Road and just keep driving. You’ll see white mounds.” So I was off.

Cliff Dwellings Montezuma Well, New Mexico

These mounds had been worked in historic times. Lumber and twisted railroad ties lay on the ground. I strode up the mound and scooped up the white powdery material, then tasted it. It wasn’t table salt as I knew it, but did have a taste of salt mixed with … something else. Dirt was liberally mixed with the salt.  Was this material good for health? Was it sodium chloride (table salt) or something else? How was the dirt removed before eating? Or was it removed? 

Mine Workings

Crystal structure of sodium chloride could provide some clues. Common salt crystals are cubic. (Not in your salt shaker, as the crystals have been ground to a powder). As I continued to wander, I discovered a salt seep and water running from it. Where the water dropped over a rocky ledge, salty icicles hung. These were pure mineral so I broke off a few icicles and placed them in an empty coffee cup I was carrying. I would analyze these later. I peered closely at some crystal fragments drying in the sun. They weren’t cubic; the white crystals were slender needles. By the way, exploring can be messy. My feet sank unexpectedly into deep goo near the salt creek, leaving my shoe behind. I dug around for it; then walked back to my car with mud peeling off my legs. I washed off in what happened to be a historic irrigation ditch down the road.

I washed off in the Camp Verde Ditch

Experiment: grow crystals

Here’s how to analyze those crystals and discover what they might be. You can do this experiment with many common substances: salt, epsom salts, sugar. Dissolve clean grains in pure water. Start with 1/2 cup of water and dissolve as much powder as the water will take. If you heat the water first, you will be able to dissolve more powder because hot water dissolves salts more easily. Stir until theThen pour the solution onto a cookie sheet with rims to keep it from running off. If you line the cookie sheet with black construction paper, the crystals will be more visible but that’s optional. Put the cookie sheet near a window where it will get indirect sunlight and wait for the water to evaporate. Crystals will be left behind. I learned the hard way not to put the cookie sheet under direct hot sunlight. Evaporation will proceed so rapidly that good crystals don’t have time to grow. But this could be another experiment! Put one tray in the heat of summer sun and another in bright but indirect light near a window. Compare the two.

Observe the shape of the crystals. If they’re cubic, you have sodium chloride. If it’s needles, you may have magnesium sulfate. (epsom salts).

Magnesium Sulfate Crystals

Experiment: Clean dirty salt

If you don’t have clean crystals, you’ll have to remove the dirt first. How to do this? Dissolve the material, dirt and all, in water and pour it through a filter. I use paper towels or cloth in a colander. Then you can proceed as above. You can also try growing crystals using dirty salt/powder. How are they different from the cleaned substance?

How did the ancient Anasazi clean the salt? They had no paper towels, colanders, and possibly no cloth as we know it. Think about this. Perhaps they let the “salt” water solution sit in a pot until the dirt settled out, then poured off the liquid for evaporation. Did they have flat stones for an evaporative surface? Or did they mix the salty solution into their foods? Or eat the salt with the dirt included?

What were the effects of eating magnesium sulfate? This mineral is actually important for many cellular functions and is sometimes used as a laxative. There are rarely negative side effects from eating it, but using it in place of salt may have left a salt deficiency in Anasazi diets. Sodium chloride is vitally important for survival. If they weren’t getting it from the “salt” mine, what other sources of salt were available? Meat and blood are one source. Some desert plants contain salt.

NOTE: The term Anasazi is outdated, but I use it here because it is still widely understood. Today’s Hopi Indians are descendants of the “Anasazi” so ancestral Hopi is a better description of cliff dwellers at Montezuma’s Well.

Balance and Center of Gravity

Vertigo: the sensation of spinning or whirling. The sensation can be associated with balance problems. A friend of mine woke up dizzy several nights ago. “I had trouble walking without feeling like I was going to fall down,” she said. Her doctor had diagnosed vertigo and given her some exercises to do. “Boring! Boring!” she complained with a chuckle.

“Maybe boring, but helpful,” said her husband who came in with his cellphone buzzing. It was an alarm to remind him when it was time for her to do her exercises. Calcium crystals in her inner ear had likely become dislodged somehow. They are critical in maintaining balance. Always ready with a joke, I shook my head rapidly back and forth: “Is this the exercise?” I asked. “Close,” her husband said. My friend demonstrated the real exercises, turning her head to the side and holding it in position for 30 seconds before turning it even further and repeating. “Just boring!” she groaned.

This started me thinking about balance and some experiments. These are geared with children in mind, but adults have fun doing them, too.

Are you in balance?

  1. Stand with feet slightly apart. Are you in balance now? How can you tell? (you feel solid and fixed in position) Now stand on one leg. Are you still balanced? Perhaps, but not immediately. How can you tell you’re not in balance? What can you do, to help become safely balanced on one leg? You need to re-center yourself so that you are standing over your center of gravity or center of balance. Sometimes it helps to throw an arm to the side. Where is your center of gravity when you’re standing on two feet? (right down the midpoint of your body). Where is it when you stand on one leg? Why can it help to hold an arm out to the side?
  2. Now try this (good party trick, too!). Tell a friend you’ll give them a sack full of gold if they can only pick it up without falling. Put the “gold” or other treasure on the floor and demonstrate picking it up. Simple! Can you do it, if you keep your knees straight and your feet unmoving? Yes. Now position them against a wall as shown, with the treasure in front of them. Ask them to pick up the treasure without bending their knees or moving their feet – or falling. It is impossible. Why? To discover the answer, watch a person carefully as they bend to pick up an object without the constraint of staying against the wall. What do you notice? How does your body change so that you keep your balance?

Image courtesy of Scientific American

I led the previous experiment with a group of giggling Afghan students in Kabul. I offered them an American penny if they could pick it up. How they tried to cheat, laughing uproariously: moving away from the wall, using their arms against the wall to stabilize themselves. I let them each have the penny afterward.

Tight Ropers

Consider how type rope walkers balance themselves. Examine these photos to see how they do it.

Struggling to place himself over his center of gravity
This long bar has weights on end
The bar has weights and. is drooping

In the lower two photographs, professional tight ropers use bars to broaden their mass and/or to lower it. Broadening your mass (spreading it out) makes you less likely to tip or rotate off your center of balance. Lowering your mass lowers your center of gravity, which is another method stabilizing yourself. When I was learning to roller blade down hills, I found myself naturally bending my knees to keep low to the ground. Lowering my center of gravity helped stabilize me. Weights on the end of tight rope bars aid in spreading and lowering the mass of the tight rope walker.

A caterpillar and balancing butterfly

Image adapted from ThinkingFountain.org
  1. Cut two of these patterns from medium weight cardboard. Shoebox cardboard is perfect but others will work, too. From one of the butterflies, cut out the center portion and decorate it to look like a caterpillar. Find its center of gravity and balance it on your finger. Then try balancing it by placing only its nose on your finger.
  2. Color the remaining butterfly as you wish, or use a photo to color a butterfly you’d like to study. Find its center of gravity and balance it on your finger. It should be easier to balance than the caterpillar. Why? Then try to balance the butterfly by its nose on your finger tip. Can’t do it.
  3. Tape a penny on the underside of each wing in the position shown. Now you should be able to balance the butterfly by its nose on your fingertip…your nose…your toe…your ear…a pencil tip. Why?
  4. NOTE: It might be easier to download the pattern directly from: https://www.thinkingfountain.org/s/symmetry/butterflypattern.gif

Your built-in balance tools

We’ve discussed how distributing weight can help tight rope walkers balance. But of course those aren’t necessary for humans to run, jump, walk, stand, or even walk on tight ropes. Our hearing, sight, sense of touch and air movements all send messages to the brain. The inner ear sends its own messages. The inner ear has three canals, lined with hairs and containing fluid and calcium crystals. As you move, the crystals brush against the hairs. Get this: (amazing, I think!) One canal senses up and down movement of your head, one senses tilt, and the other senses sideways movement. How glorious is that?

So, back to my friend with vertigo. After a day or two, the condition went away. She had done her exercises as asked. Did the exercises get her inner ear crystals in the proper condition, or did time just do its healing work? I don’t know but I’m glad she’s feeling better. Now I’ll see if I can get her to undertake tight rope lessons.

Update: African long distance runners and center of gravity

Kalenjin runners from west Kenya, tend to have tall lean bodies which may help them win marathons. Their ankles, far from their center of gravity, are thin. It has been theorized that thin ankles make it easier for them to move their legs…as opposed to stockier body types that have thicker ankles. Allen’s Rule is a scientific theory that suggests people who live in warmer climates, such as the Kalenjin, have long thin bodies. People who live in colder climates, such as Inuit, have developed stockier bodies.

Catch Your Shadow

On the recent winter solstice (Dec 20, 2020) I asked a friend to help me capture my noon shadow.

“How would I do that?” she asked.

I unrolled a length of black felt and gave her a piece of tailor’s chalk. “Follow me outside. But be quick,” I added. “Solar noon is about to happen.”

Shadows are so much fun to have in your drawer. I used to have an entire collection of them, which I would take to elementary schools. Those have been lost during my several home moves, so I decided to start a new collection. Now I asked my friend, “How long do you think my shadow will be?” “Well, it will be short since it’s noon. Maybe you won’t even have one.” She eyed my yardage. Then we went outside. I looked at my watch: 11:59 a.m., exactly solar noon.

I unrolled the fabric and stood so that my shadow fell on it. My friend began tracing it with the chalk. She had to move quickly because the shadow began shifting away from her tracing. Luckily, it was noon, when the shadow moves slowest. If we’d been working at sunset, she wouldn’t have been able to keep up. When I had caught sunset shadows for my previous collection, two of my children would trace frantically to beat the sun as it advanced and my shadow slid out from under me. “Oh, Mom,” they would complain. “Why do we have to do this?” I had interrupted their computer game.

This isn’t my real shadow; it’s a piece of felt fabric

On winter solstice, the sun carves its lowest arc across the sky. A low angle meant shadows would be longer than on any other day of the year. I’d purchased 3 yards of felt at the fabric store the previous night and even that wouldn’t be long enough to capture my shadow. I had to cut off a piece of fabric from the excess folded part and use it to extend the fabric. Even I was surprised at the length of my shadow: it was approximately 10 feet!

I’m lying atop my felt shadow

Now my friend’s husband Mike joined us. “What is the angle of the sun now?” he wondered. “Can you measure it from your shadow?” Yes, you could. My vertical body and the length of the shadow created a right triangle. The angle of the solar height could be computed from this. The angle cast by a stick and its shadow on a summer solstice several thousand years ago is the means used by Eratosthenes to calculate earth’s circumference. That will eventually be another lesson plan!

Mike took out his cellphone and used an app to find true north and we marked its line directly on the shadow for reference. I was surprised, but shouldn’t have been, to find that my shadow was pointing due north, directly toward the north pole. At noon in the northern hemisphere, shadows will always point true north, which is why taking noon sightings were so important for mariners in the days before geo-positioning satellites. (You can have fun confounding people by asking them if they can make their shadow reverse direction, pointing in the opposite direction. Often, they will try repositioning their body before they realize it’s impossible and then they will ask why it’s impossible. We all know that shadows move as the day goes on. Why can’t you get it to point south? North of the tropic of Cancer the sun is always to our south, meaning that shadows will always point northward)

Think of all the ways shadows can be used! Really, the list is endless. Sundials, moondials, Marsdials. Shadows give you an idea of the quality of light in pictures and are used to create realism in cartoons and paintings. As above, shadows can give direction and help determine latitude. Shadows have helped astronomers identify craters on the moon. Over 2000 years ago, Eratosthenes used a noon shadow at summer solstice to determine the circumference of the earth.

What is “solar noon?” That’s when the sun is at its highest point in the sky. It would be easy to say, “when the sun is directly overhead” but that’s not true on most parts of the earth. Where I live at latitude 38 degrees north, the sun will never be directly overhead. And, solar noon is rarely at 12:00 on our watches. Time zones have put our watches out of sync with the sun. To find the “watch time” that corresponds to solar noon, you can look at the NOAA website or merely google solar noon on the date in which you are interested. It was a coincidence of factors that made solar noon nearly the same as clock noon on this latest solstice 11:59 p.m.

What is “true north”? That is the line that runs directly to the north pole, or to the north star at night. It is not the same as magnetic north. because the magnetic north pole is to the east of the true north pole. True north is the one used for navigation. The difference between true north and magnetic north varies from place to place and is computed as an angle. At latitude 38 north, the difference is a whopping 15 degrees. Before cellphone apps, you could use a compass to find magnetic north, look up the angular difference on a table; then use a protractor to redraw the line. Of course, you can still do this. Pay attention to the direction of the angle! Since magnetic north is to the east, the true north line will be rotated to your left.

The best time to take standardized shadows is on the solstices and equinoxes, but any time is fun. Best to take each shadow at solar noon for accurate comparison among them. So much fun! Use felt because it doesn’t ravel when cut. I like to decorate my shadows with embroidery.

Teachers in Ghazni, Afghanistan learn about shadows in a workshop led by Camilla Barry

Make Litmus Solution

Here is a familiar science lesson. I include it here because it correlates nicely with a previous lesson about using alkali to process corn. An alkali is a caustic or corrosive substance such as lye or powdered lime that is added to soil. As a caustic substance, it can help break down the coatings on corn. As lime, it helps lower or neutralize the acid in some soils. Thus, two important uses of alkalies are to break down difficult material, or to react with acids.

A gentle alkali is baking soda. A dangerous alkali is lye. The difference between the two is their position on the pH scale. The pH scale rates the acidity or alkalinity of a material. High pH can burn your skin and mucous membranes. Low pH can be used in baking. But how do you know the pH of a substance? Litmus paper, purchased at lab supply stores or some garden centers, will give you a reading. However, you can make your own litmus solution. This lesson shows you how.

Commercial litmus paper is soaked in a solution of water and lichen species. When you dip the paper into a liquid to be tested, the paper changes color. Match the color with the key that comes with the litmus paper and you’ll discover the pH value, ranging from 0 to 14. Low numbers are for acids, high numbers are alkali, 7 is neutral. The more extreme the number, the higher the acidity or alkalinity. Different litmus papers have different color values, but the numbers are standard.

Here is a simple pH scale:

Make Your Own Litmus Solution or Paper

Chop or tear leaves of purple cabbage. Put into a large pot and cover with water. (Note: the water source could make a difference. Tap water is generally neutral, which is what you want. Well water may start off being alkaline or acidic, which will affect the results of your homemade pH test.) Bring the water to a boil; then allow it to cool. Strain out the cabbage leaves and discard. Keep the water, which will be blue. This is your litmus solution.

Distribute the solution among several clear glasses. Keep one for comparison. This will be your “neutral”, unchanged solution and it represents #7 on the pH scale. Add a small amount of a substance you wish to test, into each of the other cups and stir. The color will change due to the acidity or alkalinity of each substance. Pink to deep red are acid; green to yellow are alkaline, also known as “basic.” Arrange the cups in order of color on each side of the neutral cup and you have your own litmus color scale. Be sure to label each cup.

From left: vinegar, orange juice, neutral, hardwood ash, calcium hydroxide, lye

Make litmus paper

Soak paper towel strips in the solution and allow them to dry. The color changes are not as dramatic as the litmus solution. You can drop liquids onto the paper, or dip the paper into liquids you want to test. If you want to test a powder, or soil, mix it with water first. Again, make sure your water is neutral.

Standardizing your tests

It is impossible to be completely accurate with the cabbage juice indicator, but you can approximate the standard pH test. Test the items on the standard test (graphic above) and note the color you get with the cabbage juice indicator. Either take a photo of your solution and then write the pH number on the photograph, or try to match the color with crayons/colored pencils. Keep these for future reference.

Don’t be limited by the items on the standard pH scale! Try all sorts of powders and liquids you find around your house. So much fun!

An experiment that didn’t turn out the way we anticipated (but we learned something important):

I taught this subject to a group of Kabul university chemistry students. The class was held in a hotel conference center. I instructed students to get a large pot of boiling water from the hotel kitchen. The hotel kitchen had just finished serving lunch to students and staff. Students were delighted to learn they could make their own litmus solution because litmus paper was difficult to come by, but purple cabbage was readily available from street vendors. The indicator solution was rapidly made, but the test colors kept coming out wrong. Everything was testing too alkaline. I decided the human dishwashers in the kitchen hadn’t rinsed the pot sufficiently after washing. It still had soap residue in it, which is alkaline. I was somewhat insulting of their care in rinsing pots and thought ruefully of the lunch we had just eaten, cooked in those same pots. Then it occurred to me that the well water serving the kitchen – and all of Kabul – might be alkaline itself. I checked this with local geologists who told me that the famously good Kabul water came from wells sunk deep into limestone layers. The limestone filters the water but adds alkali to it. Then I asked a physician whether this could be a cause of kidney stones that many residents had. “Yes,” he said. “Alkaline water can cause them.”

Copper Doorknobs and Your Health

I was so excited by something I learned yesterday that I stayed up long into the night on my motel internet reading about it.

Here’s the back story. I’m traveling cross country looking for a new home and exploring along the way. In Arizona I stopped at Jerome, a once-ghost-town that is now an artist colony. Jerome was a copper mining town perched high on a mountain slope. Because the town began slipping down the slope, and for other reasons, a company town Clarkdale was built in the Verde valley below. Had to visit that! A sweet little town full of Craftsman homes built around a square…and a great copper museum inside the old high school!

The display that caught my attention was about copper’s ability to destroy microbes. Who’d a thunk? Maybe everyone else knew this. The museum curator told me that many metals disrupt microbes but that copper is possibly the best. A scholarly article I read explained that copper releases electrically charged particles (ions) when a microbe lands on its surface. A microbe includes viruses and bacteria. The ions punch holes in the surface of the virus and destroy the rna and dna inside, so it can’t reproduce. (See my earlier article about hand washing and the corona virus).

This is one reason some hospitals use copper doorknobs. The old high school itself had copper door knobs. Copper reduces infections. Why don’t more health centers use copper? It is expensive.

This article doesn’t yet include photos or citations because I’m using my iPad and I haven’t figured out how to paste them. I also can’t do experiments while traveling but here is an idea for an activity:

Moisten some bread and allow it to sit in a bowl for a few days until it is moldy. Then place some pure copper wire across part of it and see what happens. Is mold considered a microbe? I’m not sure. A piece of copper pipe or sheet of copper would be better. Why not use a penny?