Unit E Lesson 5: How We Study Space
Completion requirements
Unit E Lesson 5: How We Study Space
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Learning Targets |
Big Question: What tools have humans used to study space?
The specialized tools we use for observing space have come from many years of developing technologies for very specific purposes.
The specialized tools we use for observing space have come from many years of developing technologies for very specific purposes.
At the end of this inquiry, you should be able to answer the following questions:
- How does a refracting telescope work?
- How does a reflecting telescope work?
- How is a refracting telescope different from a reflecting telescope?
- Who is the inventor of the first telescope?
- Who built the first reflecting telescope?
Pages 436 and 437 in your textbook will help you answer questions for this lesson.
Introduction
There is a story from India about a group of blind men describing an elephant. They had no idea what an elephant was and could judge only from what they felt. The man who felt its leg imagined an elephant to be like a giant pillar, but the man who felt
its tail imagined it to be like a rope. The man who felt its ear imagined it to be like a giant fan while the man who felt its trunk imagined an elephant to be like a huge tree. All were correct, though no one had the complete picture.
Now imagine, instead of men, small fleas living on the elephant were trying to describe the elephant. How would the fleas describe the elephant and the world beyond the elephant?
Now imagine, instead of men, small fleas living on the elephant were trying to describe the elephant. How would the fleas describe the elephant and the world beyond the elephant?
- Would they be able to describe its shape and size?
- Would they believe that the elephant moved on its own?
- Would they imagine that the elephant remained in one spot while the scenery revolved around them?
- How would they know what the elephant was if they were not able to get above it, to view the elephant in its entirety?
Humans, for most of history, have been like fleas on an elephant. Incapable of seeing Earth from a distance, we were unable to see Earth for what it was. However, clues to the truth about Earth’s shape, position, and movement were available. Over
centuries, humans developed tools to solve the problem of not being able to see further. Using technology, we have been able to advance our understanding of Earth and its place in the universe.
Background Information
What prevented humans from understanding fully the relationship between Earth and space?
The problem was that the naked eye can only see so far. Ancient people attempted to build many tools to enable them to see further. During the Renaissance, European astronomers wanted to understand space and Earth’s place in the universe. For centuries, astronomers had viewed the cosmos and invented tools to aid their research. Although these tools provided remarkably accurate measurements, they were limited by what could be seen with the naked eye.
Astronomers determined that to see further, the objects far in the distance would need to be magnified. Curved glass, or lenses, had been used for centuries to magnify objects up close, but they had not yet been combined to improve the ability to see objects at a distance.
The problem was that the naked eye can only see so far. Ancient people attempted to build many tools to enable them to see further. During the Renaissance, European astronomers wanted to understand space and Earth’s place in the universe. For centuries, astronomers had viewed the cosmos and invented tools to aid their research. Although these tools provided remarkably accurate measurements, they were limited by what could be seen with the naked eye.
Astronomers determined that to see further, the objects far in the distance would need to be magnified. Curved glass, or lenses, had been used for centuries to magnify objects up close, but they had not yet been combined to improve the ability to see objects at a distance.
Can you think of lenses that magnify images?
List all the devices you can that contain magnifying lenses.
List all the devices you can that contain magnifying lenses.
- reading glasses
- magnifying glass
- microscope
- binoculars
- overhead projector
- can you think of more?
Galileo is often credited with inventing the telescope, but the first patent for a telescope was awarded to Hans Lippershey, a German spectacle maker. This early telescope, called a “spy glass” or “Dutch perspective lenses” could magnify objects up
to 3 times. It was used mainly by the military for spying into enemy camps.
After hearing rumours about this new device, Galileo constructed his own in 1609. His initial design was a tube with two lenses – a convex primary lens that curved outward and a concave eyepiece that curved inward.
After hearing rumours about this new device, Galileo constructed his own in 1609. His initial design was a tube with two lenses – a convex primary lens that curved outward and a concave eyepiece that curved inward.
Refracting Telescopes
Figure 1 – A refracting telescope.
The first telescopes are now referred to as refracting telescopes. Refracting telescopes use two lenses together to gather and focus light. Its lens cannot be larger than one metre in diameter or it distorts the image. Consequently,
refracting telescopes care limited in size.
How do Refracting Telescopes work?
As you read the following, identify the objective mirror, eyepiece, focal point, focal length, and aperture on the refracting telescope illustration.
In a refracting telescope, the objective lens is at the front end of the telescope. The light passes through the objective lens and is bent, or refracted, to a focal point. At the focal point, the light rays converge or meet. A second lens, the eyepiece, refocuses and enlarges the image. The observer looks through the eyepiece to view the enlarged image.
How do Refracting Telescopes work?
As you read the following, identify the objective mirror, eyepiece, focal point, focal length, and aperture on the refracting telescope illustration.
In a refracting telescope, the objective lens is at the front end of the telescope. The light passes through the objective lens and is bent, or refracted, to a focal point. At the focal point, the light rays converge or meet. A second lens, the eyepiece, refocuses and enlarges the image. The observer looks through the eyepiece to view the enlarged image.
A telescope’s size is referred to by its aperture. The aperture of a refracting telescope is the diameter of the objective lens.
Refractors are recognizable by their long, thin tubes. The length of a refracting telescope is determined by its focal length, which is the distance from the objective lens to the focal point. As the size of the aperture increases, the focal length must also increase.
Galileo's Refractor
Refractors are recognizable by their long, thin tubes. The length of a refracting telescope is determined by its focal length, which is the distance from the objective lens to the focal point. As the size of the aperture increases, the focal length must also increase.
Galileo's Refractor
With his refracting telescope, Galileo Galilei was able to discover that Venus had phases similar to the phases of the moon, but it was revolving around the Sun. He also observed that the moons of Jupiter were clearly orbiting Jupiter and not the
Earth. These observations led to his belief that the heliocentric model of the universe was more accurate.
Galileo’s prototype was an improvement on the spyglass that inspired it, he continued to test, evaluate, and modify his design until it was able to magnify objects up to 30 times.
Reflecting Telescopes
Even Galileo’s best telescope had flaws.
Often, the images were blurry and distorted, and the telescopes were growing to more than 30 metres (100 feet) long, and becoming increasingly difficult to handle. Astronomers continued to pursue greater and greater magnification to see further into space.
In England in the 1680s, Isaac Newton was studying the properties of light. He built a small but powerful telescope by replacing the objective lens with a spherical mirror that reflected and focused light. This type of telescope is called a reflecting telescope.
Reflecting telescopes use mirrors instead of lenses to gather and focus light. The advantage of reflecting telescopes is that they are not are not limited in size.
The following diagram has some parts of a reflecting telescope labelled, but not all. Read below the diagram and see if you can identify the primary mirror, secondary mirror, eyepiece lens, focal length, and aperture on the reflecting telescope in Figure 3.
Often, the images were blurry and distorted, and the telescopes were growing to more than 30 metres (100 feet) long, and becoming increasingly difficult to handle. Astronomers continued to pursue greater and greater magnification to see further into space.
In England in the 1680s, Isaac Newton was studying the properties of light. He built a small but powerful telescope by replacing the objective lens with a spherical mirror that reflected and focused light. This type of telescope is called a reflecting telescope.
Reflecting telescopes use mirrors instead of lenses to gather and focus light. The advantage of reflecting telescopes is that they are not are not limited in size.
The following diagram has some parts of a reflecting telescope labelled, but not all. Read below the diagram and see if you can identify the primary mirror, secondary mirror, eyepiece lens, focal length, and aperture on the reflecting telescope in Figure 3.
Figure 2 – Newton investigating the properties of light.
Figure 3 – All reflecting telescopes have a similar structure to this diagram.
In a reflecting telescope, light from the image enters from the front and travels through the telescope tube to the primary mirror at the back. Light reflects from the primary mirror to the secondary mirror that is tilted at 45°. The light is then reflected
through the hole at the top part of the tube and into the eyepiece.
A telescope's size is determined by its aperture. The aperture of a reflecting telescope is the diameter of the primary mirror. The focal length is the distance from the primary mirror to the focal point. As the size of the aperture increases, the focal length also increase.
As light passes through a lens, it breaks into various colours. In refracting telescopes, this produced a halo effect around the objects being observed, which frustrated astronomers. Isaac Newton was the first to replace the primary lens in the telescope with two mirrors. This improvement allowed astronomers clearer views of celestial objects.
A telescope's size is determined by its aperture. The aperture of a reflecting telescope is the diameter of the primary mirror. The focal length is the distance from the primary mirror to the focal point. As the size of the aperture increases, the focal length also increase.
As light passes through a lens, it breaks into various colours. In refracting telescopes, this produced a halo effect around the objects being observed, which frustrated astronomers. Isaac Newton was the first to replace the primary lens in the telescope with two mirrors. This improvement allowed astronomers clearer views of celestial objects.
Figure 4 – Newton's Reflector
Interactive
Telescopes
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This BrainPOP video reviews telescopes.
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to watch "Telescopes".
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- Username: 0099
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Password: students
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Click here
to complete the quiz on Telescopes. Remember to check your answers at the end!
Try It!
Practice Worksheet: Telescope Advantages Chart 1
- DOWNLOAD this practice worksheet (S9_UE_S2_L5_telescope1). If you prefer to use a Google Drive or PDF version of the worksheet, click here.
- Answer the questions on the worksheet.
- When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below.
Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
Figure 5 – Modern telescopes provide excellent views of the night sky.
