Educator How-to: Learn to Draw a Celtic Triquetra

At the Houston Museum of Natural Science, we know that people are as much a part of natural science as rocks and dinosaurs. That’s why we love social studies and maintain exhibits like the John P. McGovern Hall of the Americas and the Hall of Ancient Egypt. We find the development of societies fascinating!

The historical Celts, a diverse group of tribal societies in Iron Age Europe, ranged over a large swath of land reaching as far west as Ireland and the Iberian Peninsula, east to central Anatolia, and north to Scotland. The Celts used a three-cornered symbol, known as the triquetra, to adorn everyday items and important ritual objects. Similar tri-cornered symbols are seen in the artwork of many ancient civilizations. It is speculated that the symbol illustrates the uniting of the past, present, and future or birth, life, death. As Christianity spread through Europe, the triquetra was used to help new converts to understand the concept of the Trinity.


It is really simple to draw this ancient knot-work symbol. All you need is paper, a compass, an eraser, and some markers.

First, using a compass, draw a circle of at least 3 inches in diameter in the middle of your paper. Make sure to leave room around the circle, as the resulting knot will be slightly larger than the initial circle. Make sure that you do not adjust the compass after the circle is drawn.


Next, use a pencil to make a point on the circle at the twelve o’clock position. Then, place the point of the compass on this point and use it to make marks where it crosses the circle on each side.   


Now, place the point of the compass on one of the marks made in the previous step. It doesn’t matter which one. Then, draw a semi-circle within the initial circle. It should start at the twelve o’clock point and end in the lower quarter of the circle. The arc does not need to be continued outside of the circle. Make another arc, identical to the first one. The two arcs should cross at the center point of the circle. If they don’t, check to make sure that the compass setting has not been changed.


Then, placing the compass point on the lower tailing end of one of the arcs, mark off another tic on the bottom of the circle.celtic5


Now place the point of the compass on the bottom mark and draw an additional arc from side to side within the circle.


You will now need to enlarge the diameter of the compass a bit. Place the compass point back onto the marks made in the upper half of the circle. From each point, draw another arc within the circle, and extending a little beyond its border. It is important to make sure the arcs are extend a bit outside of the circle so they’ll meet up when the arcs are all drawn.


Pick a point where one of the knot strips intersects another, and make it pass over the other, erasing the lines from the underside from within the “over” strip. The next pass for the knot strip, following the same strand, will be to go under the next intersection, so erase appropriately. At this point ,you may erase the initial circle and the arc marks.


Now your trisquetra is complete! Color it in! See designs like this and others this summer in the Medieval Madness Xplorations Summer Camp.


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Mark Your Calendars for these events happening at HMNS 6/20-6/26

Last week’s featured #HMNSBlockParty creation is by Michael (age: 15): 

block party 25

Want to get your engineering handwork featured? Drop by our Block Party interactive play area and try your own hand building a gravity-defying masterpiece. Tag your photos with #HMNSBlockParty.

Lecture – The National Parks – America’s Cathedrals of Nature by Mark Burns
Tuesday, June 2
6:30 p.m.
In honor of the 2016 centennial celebration of America’s national parks, American photographer Mark Burns’ set out on The National Parks Photography Project. In this special evening with the photographer Burns will chronicle the project that took him to each of America’s 59 national parks. Following the presentation, the audience will be invited into the exhibition to see the collection of iconic black and white photographs with the photographer.

Life Under the Microscope: Paleontology
HMNS at Sugar Land
Thursday, June 23
10:30 a.m. – 12:30 p.m.
Learn about the practical applications of microscopy or just look at cool stuff on a micro scale! Travel the world as you view grains of sand collected from various continents, and learn about their origin, composition and transport. Look at microfossils, shells and other natural objects, or bring an item from home and check it out under the scope. As hands-on activities are the best way to learn, we’ll have interactive demo stations with docents to guide you through the amazing visuals you’ll see as you peer through the lens!

Class – Water-Wise Gardening
Saturday, June 25
9:30 a.m.
A garden that conserves precious water resources is a rewarding investment. An irrigation system is a practical choice for most garden locations. This class will teach design, installation and maintenance of drip and micro-spray systems.
Be able to take a summer vacation without losing your landscape and vegetable garden investments to drought. Grow a beautiful summer garden while protecting the watershed and reduce waste of one of our most important natural resources.

Summer Cockrell Butterfly Center Events 
Summer Cockrell Butterfly Center events continue through Aug. 19.

  • Wing It | Tuesdays at 10:30 a.m.
    Come fly away into the world of butterflies at the Cockrell Butterfly Center with Wing it! Introduce yourself to your favorite winged wonders and watch the release of hundreds of new butterflies into the rainforest.
  • Small Talk | Wednesdays at 11 a.m.
    Join our Cockrell Butterfly Center team as they take their live collection of insects out “for a walk” during Small Talk. Our experts will entertain and educate with all types of insects and arachnids.
  • Friday Feeding Frenzy | Fridays at 9:30 a.m., 10:30 a.m. & 11:30 a.m.
    Join us this morning in the Cockrell Butterfly Center for our Friday Feeding Frenzy! See science in action as snakes, spiders and centipedes enjoy a meal right in front of you!
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Cloudy Views Through a Clear Lens: George Observatory Anticipates Research Explosion When Wet Weather Dissipates

It’s been a wet, cloudy year for George Observatory, but flooding and poor viewing nights at Brazos Bend State Park haven’t kept astronomers from dreaming. Big breakthroughs have happened at the George in the past, and with a complete restoration of the 36-inch, deep space Gueymard Research Telescope, a return to astronomical research is quite simply a waiting game. And with even more rainfall this week, astronomers will have to wait a little longer. The park will remain closed until at least July 12.

“We couldn’t do research forever because of the lens,” George Director Peggy Halford said, referring to the heavy deposits of grime the telescope suffered during its 50 years standing in the muggy climates of Louisiana State University and west Texas wetlands. “And as soon as we got the lens restored, the park flooded.”


Photo posted June 3 on Brazos Bend State Park Facebook page. The post reads, “In the history of the park (since 1984), water levels have never been this high.”


In spite of this development, both amateur and professional astronomers have been using the past 13 months, April and May 2016 in particular, to prioritize future projects using the refreshed equipment. As water over park roads continues to prevent access to the observatory, and cloud cover access to the night sky, these scientists are keeping their heads in the game through planning and pitching sessions.


Photo posted June 2 on Brazos Bend State Park Facebook page. The post reads, “We awoke this morning to find water over Park Road 72 for a roughly 1.25-mile section between Park Headquarters and the Nature Center and a small section between the park entrance and Park Headquarters.”

In an age of computer-guided photometry and NASA probes, the science of star-study from the ground “may not be that glamorous,” Halford offers, but it’s not without significant value. One project idea, for example, involves the study of what happens in space after a supernova goes off, or in science-speak, cataclysmic variable star system follow-up observations.


Artist’s rendition of a cataclysmic variable star. By Mark A. Garlick.

Not all stars are alone; some come in pairs. Cataclysmic variables are double-star systems that include a super-dense white dwarf and a normal star rapidly orbiting each at a rate of about once an hour. Because the white dwarf is so close to its partner, it strips off material from the normal star’s corona, creating an accretion disk around itself as it accumulates more and more mass..As this energy vacuuming proceeds, unstable matter in the accretion disk occasionally ignites, ejecting a flash of light called a nova. Eventually, the white dwarf will absorb enough of its partner’s energy to detonate a super-massive thermonuclear explosion of incredible power — a supernova. The novae and supernovae of cataclysmic variables are recorded in all cases, but few events are studied, according to Halford.

“The big surveys are great at catching these things in outburst, but there’s little value in the discovery if no follow-up is done,” Halford stated. “The follow-up photometry gives us the rate of fade, and an idea of the characteristics of a particular type of variable, or an idea of the angular momentum of accretion disk in a binary system, et cetera.”

In other words, the moments after novae are some of the most crucial in the effort to know more about these systems, and the lives and behavior of stars in general. Science being an empirical pursuit, the more data, the better. The Gueymard is particularly suited to this type of research given its deep-space capabilities as well as its accessibility to Houston local astronomers.


The relative size of all asteroids visited by spacecraft as of November 2010.

For the purists, the observatory offers an opportunity to discover asteroids — large bodies of rock and ice within our solar system — through classic methods. While computerized telescopes can now scan for inter-planetary bodies and minor planets much faster than a human ground observer, the pursuit is no less exciting or valuable when new discoveries are made.

“In years past, we’ve had astronomer teams that have discovered more than 500 asteroids,” Halford said. “We have a few people who are going to continue to do it by hand and by eye. If they did discover one coming toward Earth, it could potentially be life-saving.”

George astronomers have also proposed a project that could track light pollution in the area using the magnitude of stars. With this set of data, they could fight for more governmental regulation of municipal lighting. Halford and other interested volunteers at the George have already won battles in the fight to keep the skies dark.


Photos of the night sky before and during the Aug. 14, 2003 blackout in the northeast U.S. and Canada. In urban areas, the Milky Way and orbiting satellites suddenly became visible without light pollution.

“About 15 years ago when we heard the Grand Parkway was going to be built, with the museum’s support, we talked to the state legislature and got a bill passed that allowed us to talk to county commissioners about light in unincorporated areas,” Halford said. “There is currently a lighting ordinance around the George Observatory.”

As Houston and surrounding cities continue to grow, studies of how light affects the appearance of the night sky will provide continuing support for the astronomy community and preservation in general. From the star-lover’s perspective, the sky is yet another endangered species or threatened environment.

While the water continues to recede, these astronomers will continue to plan. The McDonald Observatory in west Texas is always an option, but that means a 12-hour drive and it’s expensive to get time on the telescopes, according to Halford.

“We can’t get to our telescope, so now’s the time to throw out some ideas,” she said. “For the local astronomer who wants to contribute to the scientific body of knowledge, this is the best place to do it.”

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Sand Fleas Are Real! (But They’re Not What You Think They Are…)

Well, it’s summer time again and millions of people will be spending lots and lots of time outdoors. They will go to the lake, they will go to the beach, they will have picnics and barbecues and luaus. All the while, they will be joined by many unwanted guests — of the arthropod kind!

Many people think about the summer in Houston a little like this:


Cartoon by Gary Larson

Bugs, or arthropods, are everywhere, and our favorite time of year to play outside just happens to be the prime of most of their little lives. Every year I hear horror stories about bugs, particularly about the beach. Perhaps it’s because creatures that inhabit such an environment are so foreign to us. The oceans are the earth’s last known frontier, and animals that live inside or near it might as well be aliens to most of us!

We are so lucky to live in the age of having information at our fingertips. Want to know something? Just Google it! The almighty “internets” can’t be wrong! But anyone is allowed to write anything about any topic they desire, so the almighty internets are sometimes wrong.

If you want to go to the beach, and you Google, say, sand fleas, you’ll very likely read articles that will keep you away from the beach for good! So allow me to fill you in on some of these mysterious critters that call the beach home.

Arthropods are the most abundant and successful animal life-form on the planet and they can be found surviving and thriving in almost any environment. Naturally, they enjoy the beach as much as we do. The warm temperatures, that nice ocean breeze… If you walk along the beach at any time of day, especially the morning or evening, you will see all sorts of activity — mussels that have been unearthed by the waves wiggling back down into the sand, little crabs skittering around, flies buzzing about, and perhaps seaweed washed ashore, covered in small creatures.


Sand hopper, a crustacean in the order Amphipoda and the family Talitridae. Many different genera have a similar appearance.

These herbivorous creatures are most likely what we sometimes call “sand fleas,” though they are actually land hoppers or in beach environments, sand hoppers. You may have heard terrible things about these little guys, that they suck your blood, leaving awful welts, or even that they burrow into your skin to lay eggs. None of these things are true of sand hoppers. They are crustaceans, cousins to the insects, with five to seven pairs of legs and two pairs of antennae. Other well-known and delicious crustaceans are crabs, shrimp, lobsters and crawfish. Sand hoppers belong to the order Amphipoda and sort of look like a cross between a giant flea and a roly-poly. They mostly live in water, but some species are terrestrial and live in damp areas. They are scavengers that feed on rotting organic matter, so a nice pile of washed-up seaweed looks really good to them. They can hop, but that’s where the similarities with actual fleas begin and end! They do not suck blood, and in fact they want nothing to do with you. If you approach them, they will jump away, the obvious origin for their common name.


Mole crab (Emerita analoga) digging in the sand.

Another crustacean incorrectly called a sand flea is a tiny little crab called a mole crab — AWWWWW!!! (Oh wait, am I the only one who thinks it’s cute?) They are filter feeders, meaning they filter plankton from seawater. They burrow down into the sand where the waves break on the shore, and they’d also prefer to stay away from humans.


True sand fleas are native to central and south America and Africa. They lay their eggs in mammalian flesh, leaving a bad infection on the hands and feet.

Now, the true sand flea, the one that is an actual flea, is a nasty parasitic insect. But, they don’t inhabit North America. You can, however, find them in Central America, South America and Africa. Sand fleas, also called the chigoe flea, are the smallest known flea species (about one millimeter across). They burrow into mammalian skin to feed and may cause an infection known as tungiasis. But this is only really an issue in areas of poor sanitation. So please folks, don’t worry yourself over sand fleas.

2006 Frank Collins Leishmaniasis is transmitted by the bite of infected female phlebotomine sandflies, injecting the infective stage (i.e., promastigotes) from their proboscis during blood meals.  Promastigotes that reach the puncture wound are phagocytized by macrophages ,and other types of mononuclear phagocytic cells, and inside these cells, transform into the tissue stage of the parasite (i.e., amastigotes), which multiply by simple division and proceed to infect other mononuclear phagocytic cells.  Parasite, host, and other factors affect whether the infection becomes symptomatic and whether cutaneous or visceral leishmaniasis results.  Sandflies become infected by ingesting infected cells during blood meals.  In sandflies, amastigotes transform into promastigotes, develop in the gut, (in the hindgut for leishmanial organisms in the Viannia subgenus; in the midgut for organisms in the Leishmania subgenus), and migrate to the proboscis. See PHIL 3400 for a diagram of this cycle.

Sand fly (Phlebotomus papatasi), but the name can refer to any species of biting, blood-sucking insect found in sandy environments.

The only arthropods that may feed on you at the beach are things that will feed on you everywhere else, mosquitoes, and biting flies (sometimes called sand flies). Unfortunately, I don’t have much to say in defense of mosquitoes you’ll find at the beach, especially salt marsh mosquitoes (Aedis sollicitans), they’re kind of the worst! They’re large, fast, and pretty relentless. They breed in inter-tidal pools of brackish water and the eggs can lay dormant for years waiting for water!


Sand midges beside a dime and a pencil point to show their relative size.

Other flies that feed on you at the beach are small midges, commonly known as “no-see-ums” (yes, really), and just like mosquitoes, only the females feed on blood in preparation to lay eggs. The most you’ll get from these are classic signs of a bite, small red bumps that itch. A good bug spray containing DEET, or even some that contain effective essential oils such as lemon and eucalyptus, are effective at repelling all of these types of insects.

So if you’re heading to the beach this summer, don’t forget the sunscreen, don’t forget the bug spray, but leave the entomophobia (fear of bugs) at home. You have nothing to fear!

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