### Science Lesson: Bridges & Arches

Bridges are built based on physics principles, so the engineers who design bridges have to understand physics. The opposing force of a bridge's construction has to be greater than the downward pull of gravity and side-to-side pull of wind and water. A good bridge is built to withstand every force against it—even earthquakes, in the case of San Francisco's Golden Gate Bridge. How a bridge overcomes the forces of gravity, wind, and waves depends on what type of bridge its engineer designed it to be.

Arch bridges were one of the first types of bridge. The Romans used arches in their bridges and aqueducts as well as in their triumphal arches and other great architecture. See a picture of Constantine's Arch here and Minnesota's Stone Arch Bridge here. Arches are designed with an odd number of stones, with the top, middle one being the keystone on which the bridge's weight rests. These stones have slanted sides so that they fit tight against each other. The downward force of the bridge's weight spreads out to the stones on either side of the keystone.

Truss bridges utilize the rigid 180 ° total angle of triangles to spread out force. A web system of sturdy beams between two girders forms a zigzagging triangle pattern, stiffening the bridge and spreading out weight so that no one section bears all the weight at that spot.

The Brooklyn Bridge in New York is one of the most famous bridges, now not so much for its size as its beauty. Built in 1883, it was the first great suspension bridge and a feat of engineering. Suspension bridges use a combination of strong cables and solid towers to achieve a balance of forces. The stone and steel that Brooklyn Bridge was built with combined to make it both solid and graceful. See a picture of it here.

For a simple project that demonstrates how one type of bridge support works, use sugar cubes to build an arch. Taper the sides of the cubes with an old nail file (or scrape them with a kitchen knife) so that they fit snugly against each other to form an arch. Be sure to use an odd number of cubes, so that there's only one cube in the middle. If you used two cubes in the middle, the frictional force between those blocks would be overcome by the load force on the arch, causing it to buckle.

If you want to learn more about bridges and construct your own models of an arch, truss, and suspension bridge, we highly recommend the Amazing Bridges kit.

### Science Lesson: The Science of Art

Just taking a look at the creation around us shows that the study of science doesn't need to be ugly or boring! God not only created iridescent butterflies and majestic mountains, he created mankind in his image and gave us an interest in his world. Science and art are two ways of using that interest to glorify our Creator, and often they complement each other.

One way you can help your children to develop their scientific and artistic skills at the same time is by having them keep a notebook of things they observe. Both artists and scientists need to be good at observing, describing, and reproducing results—whether through experimentation or through drawing and other mediums. In the notebook make sketches of birds, insects, leaves, flowers, and other interesting things that you find. Describe color and eating habits (if any), social behavior, or any other odd features that you observe. If you have a microscope, study different specimens with it and make notes and drawings for each one. How does using a microscope better show you God's artistic design? Compare pictures you make of a specimen (such as a small insect or flower) with and without magnification.

Scientific knowledge has affected art throughout the centuries—advances in fields such as chemistry, physics, biology, and math have changed the way artists create and think. For example, in the 14th century painters began to paint using perspective to give a look of depth to their works. This method was developed from principles of geometry.

With the development of new pigments in the late 19th century, artists such as Georges Seurat and Claude Monet were able to afford a wider variety of paint colors. Earlier painters had to mix their own paints from natural pigment sources, and some of the colors could be quite expensive. The synthetic paints invented after World War II expanded the color palette even further. Better chemical technology has also enabled people to clean or restore old works, such as Leonardo da Vinci's 'The Last Supper'.

New ways of using science and art are constantly being developed. In movies such as The Lord of the Rings and Finding Nemo, science has been really useful. From designing indoor sets with natural lighting to creating and filming virtual worlds, science is key in creating amazing visual effects.

### Science Lesson: Paper & Ink

In Egypt, the first paper was made from the water grass papyrus. In medieval Europe, calfskin was used to make vellum and the under lining of sheep skin was used for parchment, on which scribes recorded financial transactions and monks copied scripture. But paper as we know it was invented by the Chinese by 105 AD—they used hemp pulp to form sheets of it. The papermaking process was refined by the Arabs and arrived in Europe by the 1100s.

Now we have technology that allows us to make shiny book covers and photo paper, fine-grained printer paper, and cheap newsprint. Better paper-making technology allows us to have access to paper in all sizes, shapes, colors, and textures.

Inks were originally made from the natural pigments in living materials such as berries, nuts, and leaves. The pigments in a green leaf, for example, absorb all the color wavelengths of light except for green. Therefore the green color is the only one reflected back to our eyes and the only color we see. (Remember ROY G BIV? A beam of light contains the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Under normal circumstances, though, we don't see all of those colors because some or all of them are absorbed by the material they shine on.) Through chemical processes, these pigments can be extracted and turned into dye or ink. Here are some easy recipes for ink you can make at home.

Berry Ink. Use 1/2 cup fresh berries or thawed frozen berries; push them through a strainer so that you get pulp-free juice. Add 1/2 teaspoon of vinegar (to hold color) and 1/2 teaspoon salt (as a preservative) and mix well. You can use a glass baby food jar as your 'inkwell', if you have one.

Walnut Ink. Crush the shells of 12 walnuts by putting them in a sock and hammering them lightly. Pour the shells into a saucepan and cover them with water, then let them simmer for 30 minutes. After that, remove them from heat and let them soak overnight. Add 1/4 teaspoon of vinegar to help preserve the color.

Invisible Ink. Try writing with lemon juice on a piece of paper using a paintbrush or Q-Tip. When the ink has dried, hold the paper over a toaster to heat it. Your writing should appear in brown lettering as the parts of the paper with acid from the lemon juice brown faster than the other parts. You can also make ink from equal parts baking soda and water. Brush grape juice over your secret message to reveal the writing—the acidic grape juice reacts with the baking soda, which is a base.

#### Science Bites

Camera Obscura. Originally, this instrument (in the scientific sense of the word) consisted of a dark room with a tiny hole for light to come through—a reversed image of outside objects was projected through the hole and onto the opposite wall. This was used as early as 330 BC for viewing solar eclipses. Later cameras used a glass lens and a sheet of glass to more accurately project the image so that it could be sketched. This device was helpful for astronomers and artists; Vermeer is thought to have used a camera obscura while he was painting A View of Delft. The name comes from the Latin for 'dark chamber.'

Scientists/Artists. Some artists are famous in the scientific world as well as the art world—or vice versa. John James Audubon gained international fame in the mid-1800s for his lifelike drawings of American birds. He observed birds in their natural habitats as well as stuffed bird specimens, and made careful representations of them. The National Audubon Society, a conservation group, is named in his honor. In the later 1800s, Dr. Henry Gray wrote a medical school textbook that has become a classic, Gray's Anatomy. Its detailed illustrations help students better understand how the body works. Check out our Gray's Anatomy Coloring Book!

The Scientific Speaker

Voussoir (say it 'voo-swar') is the name for the stone in an arch, from the Latin for 'turn' or 'roll'.

Sfumato (say it 'sfoo-mah-toh') is a technique that Leonardo used incomparably well in some of his paintings—including 'La Gioconda'. This technique involves blurring and blending of paint so that the texture and color fade as distance increases. This gives the picture a feeling of depth.

Another painting technique used by Leonardo is chiarascuro—using light and shadow to show something, rather than painting outlines. (Van Gogh and Cezanne, among others, practiced the opposite of this in many of their great paintings, using dark outlines.)