#2317-Feature: Full Spectrum


Galileo GalileiGalileo

“The Bible tells us how to make it to Heaven, not how Heaven is made.”  1615, Cesare Cardinal Baronio

In 1633 the Roman Catholic church hauled Galileo Galilei, an astronomer, before the Pope’s court, the Inquisition, and forced him to deny what he had seen with his own eyes: the earth revolves around the sun.  More than 300 years later the same church pardoned him and acknowledged the truth of his discovery.  Despite the censorship of Galileo’s ideas, they lived on in other people’s writings and discoveries.

When Galileo came up with observations about the stars, both ancient philosophers and the Church had believed that the earth was the center of the universe for several centuries.  By arguing with them, Galileo threatened the authority of a religious system that asked its followers to accept many beliefs on blind faith.  Disagreeing with the church was called heresy, a serious crime punishable by torture and sometimes death. To avoid punishment, Galileo bowed before the charge of heresy and denied his observations, but later he passed his ideas on to his son and others.

Galileo made his first discovery at the age of 20 when he timed a lamp swinging above his head using the beat of his pulse. He observed that no matter how wide the lamp swung, it always took the same amount of time.  This was called the Law of the Pendulum.  Clocks kept time using pendulums until the 1950’s when electricity replaced pendulums as regulators. You can still see the law of the pendulum in action in a grandfather clock.

Galileo used his observational powers and scientific reason to discover other laws and tools over the next few decades.  He found that objects of unequal weight drop at the same speed, The Law of Falling Objects.  He invented a thermometer to measure heat, a hydrostatic balance to measure the gravity of materials like gold and silver, and a microscope to look at insects.  But the discoveries he found using a telescope shook the world he lived in more than any others did.

When Galileo heard of a spyglass made by a Dutch eyeglass maker, he was fascinated.  He built one for himself that magnified objects thirty-three times their size and turned it to the sky, creating the first astronomical telescope.  He published his findings in a book called The Starry Messenger and became famous.  After a few decades he published another book that became a best seller.  In it three characters debated whether the center of the universe was the earth or the sun. One of the characters that was portrayed as ignorant seemed to be the Pope.  Galileo had gone too far.  The Pope called him before the Inquisition.

Although he took back what he said under pressure of possible death, Galileo was placed under house arrest for the rest of his life. Four years later he went blind from an infection.  Fortunately his son and two other assistants helped him continue to write – though not about the sky.  He wrote about force and motion and his work became the basis for some of Isaac Newton’s ideas. 

Galileo’s influence extends beyond the realm of astronomy. Sometimes he is called the father of modern science, because he thought it was important to test ideas through experiments, before he accepted them as the truth.


Arecibo Observatory


With a dish measuring 1000 feet in diameter, 167 feet deep, and covering an area of about twenty acres, this enormous radio telescope, located at the Arecibo Observatory in Arecibo, Puerto Rico, is by far the biggest telescope in the world.  The surface, made up of almost 40,000 aluminum panels, acts as a super-magnet, collecting radio waves from the deepest parts of space.  The waves then reflect upward towards a 900 ton platform.  A huge dome attached to this platform then focuses the waves toward several antennae that hang below.  Astronomers can easily interpret these waves, which is very beneficial, because they can then effectively learn much more about our Solar System, our Galaxy, and even the farthest reaches of the Universe!

Use the latitude and longitude coordinates below to find other big telescopes located at these observatories around the world:

globe1)   32:39N, 105:42W

2)   32:50N, 109:42W

3)   19:44N, 155:05W

4)   33:19N, 116:53W

5)   29:15S, 70:44W

6)   31:16S, 149:17E



Eric FiegelsonEric Fiegelson, an Astronomer and Astro-Physicist at Penn State University, sure knows a lot about the sky.  Click below to see and hear what he has to say.

To contact Eric with any questions you may have about Astronomy, feel free to send him an e-mail:  edf@astro.psu.edu


When scientists search deep space, they’re often looking for objects they’ll never see. Black holes, for example, give off no visible light, so scientists must instead search for objects nearby that may be affected by the black hole. 

Have one student in your class hide an every day object underneath a dark cloth. Then discuss ways you and your classmates might figure out what is under the cloth without touching or looking at the object.




Glass has been an important building material ever since the Egyptians first learned how to make it about 5,000 years ago.  That’s because it’s transparent.

The word transparent comes from the Latin word trans, meaning “through” and parere meaning “to show oneself.”  A transparent material allows light to pass through it without scattering the rays. (Literally, “to show oneself through.”)  No material is completely transparent. Some light energy will always be absorbed by the material that it passes through. The thicker the material, the more energy it will absorb. That’s why it’s easier to see through a thin frosting of ice on your window than to see through a thick block of ice.

The word translucent comes from the Latin word trans and lucere meaning "to shine." A translucent material allows some light to shine through, but scatters the rays so much that you can’t see clearly through it. Colored glass or white gauzy fabric are examples of translucency.

The word opaque comes from the Latin word opacus meaning “shade” or “darkness.” An opaque material lets no light through. Most metals are opaque. They may reflect light, but they don’t let light pass through them.

Look around your classroom for examples of transparent, translucent, and opaque materials. Hold the objects up to a light to test them. Try a lampshade, a book, eyeglasses, a photographic slide, a plant leaf or petal, a ruler, a piece of paper, and a glass of water.




In the 1700s, the British scientist William Herschel discovered that different colors had different temperatures. You can test his findings for yourself.

Here’s what you’ll need:

4 clear 2-liter bottles.
1 2-liter bottle of Pepsi, Coke, or other cola beverage.
5 thermometers
5 straws
red, blue, and yellow food coloring
pencil and paper
a sunny day

Here’s what you’ll do:

1.Fill the four empty bottles with water.

2.Add food coloring to three of the four to make one bottle each of red, yellow, and blue water. Leave the fourth bottle clear.

3.Place all four bottles, along with the bottle of cola on a sunny windowsill for about one hour.

4.Cut string into five 15 cm. pieces.

5.Tie one end of each string securely around a thermometer. Tie the other end to the middle of a straw.

6.Shake down each thermometer until they all read about the same temperature.

7.When the bottles have been on the windowsill for about an hour, lower one thermometer into each bottle. Rest the straw across the mouth of the bottle. The string should be short enough so that the thermometer will be suspended about halfway between the top and bottom of the bottle.

8.After they have been submerged for about five minutes, bring each thermometer up and record the temperature.

9.Move the bottles away from the windowsill so they’re no longer in sunlight. Keep them away from any heat source for 5 minutes.

10.Repeat steps 7 and 8.

Based on your observations, which color absorbs the most heat?

Which color reflects the most heat?

If you placed these colors on the electromagnetic spectrum, which order would they be in from least heat energy to most?

How could this information be used by building or clothing designers?


camera guyPICTURE THIS!

Using the full spectrum of wavelengths, telescopes and cameras have produced beautiful images of space. Search these sites on the web to compile a scrapbook or bulletin board of spacescapes. Be sure to note which types of electromagnetic waves were used to produce each picture.

NASA’s Origins Program

Space Telescope Science Institute

NASA’s Solar System Exploration Program

Cassini-Huygens Mission to Saturn and Titan.

The Messier Catalog of Space Images



Before his execution, convicted murderer Joseph Paul Jernigan willed his body to science for the Visible Human Project. Soon after his death in 1993, Mr. Jernigan’s body was sliced into 1,871 layers. Each layer was scanned into a computer creating a unique view of the human body.

Get beneath the surface at:  http://www.nlm.nih.gov.



See for yourself why stars twinkle.

Here’s what you’ll need:

- Flashlight
- nail
- empty cereal box
- electric hot plate

Here’s what you’ll do:

1.Use the nail to poke about a dozen small holes in one side of the cereal box.

2.Turn on the flashlight, and stand it upright in the cereal box.

3.Close the box flaps so that the only escaping light is through the holes or “stars.”

4.Place the hot plate on one end of a safe surface such as a table, making sure that it doesn’t touch anything flammable, and turn it on.

5.Place the box on the table about 20 centimeters from the hotplate with the starry side of the box facing the hotplate.

6.Position yourself at the other end of the table so that the hotplate is between you and the box.

7.Observe the twinkling stars!

Here’s why they twinkle:

The warm air from the stove rises with varying temperatures, causing the air to have different densities. When a beam of light travels from air of one density to another, it bends or refracts slightly.  Just as the warm air from the hotplate bends the light coming from the cereal box, the varying temperatures and densities of Earth’s atmosphere bend the light from stars. The scattering starlight makes the stars seem to twinkle. But only from Earth. In space where there is no atmosphere, stars do not twinkle.