The telescope is humankind’s single greatest technological step toward understanding... universe. Although he did not invent the instrument, Galileo was... Performance Benchmark E.12.B.3

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Performance Benchmark E.12.B.3

Students know ways in which technology has increased understanding of the universe. I/S

The telescope is humankind’s single greatest technological step toward understanding our universe. Although he did not invent the instrument, Galileo was the first to point a telescope to the night sky and his observations helped propel the modern scientific revolution. Galileo made five important observations that directly contradicted the mythological view of our universe that, up to that time, dominated orthodox wisdom: 1.

2.

discovering that Jupiter has moons that rotate about the planet; observing that Venus has phases, a finding that could only be explained by Venus 3.

orbiting the Sun; discovering that the Moon has mountains, valleys, and craters that are similar to features on Earth; 4.

5.

observing that the Sun has blemishes (sunspots) and rotates about once every month; and observing that the Milky Way is not a smooth field of light, but is made up of thousands of stars. The first two observations directly supported the Copernican model that Earth orbits the Sun, rather than the Sun orbiting Earth. The other three observations showed that the heavens, once thought to be perfectly ordered, were in fact quite varied. To learn more about the Galileo and his use of the telescope, go to http://galileo.rice.edu/sci/instruments/telescope.html

Telescopes observe light and it is through this light that scientists gather all their information about the universe beyond Earth. The first telescopes, such as those of Galileo and Newton, observed visible light. But visible is only a small part of the entire light spectrum. In the 20 th century, scientists began to use all other frequencies of the electromagnetic spectrum (radio, microwave, infrared, ultraviolet, x-ray, and gamma-ray) to observe the universe. By observing these wavelengths, astronomers were able to discover a vast universe of phenomena, such as black holes, neutron stars, extrasolar planets, and active galaxies. On good overview of telescopes can be found at http://www.astrosociety.org/education/family/resources/telescopes.html

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Figure 1.

Schematic diagrams of the two basic kinds of telescopes used to observe visible light. On the left is a refracting telescope that uses lenses. On the right is a reflecting telescope that use mirrors. (From http://www.io.com/~hcexres/textbook/recomx6c.html

) Of equal importance to science as Galileo’s first telescope observations are the observations that have been made from space-based observatories. These telescopic observatories have provided an unimpeded view of the universe without Earth’s atmosphere acting as a filter. Indeed, some light frequencies, such as infrared, x-ray, and gamma ray, are only observed from space (or high in Earth’s atmosphere) because these frequencies do not penetrate to Earth’s surface. Of these orbiting observatories, the Hubble Space Telescope is the most famous and has provided a view of the universe in the visible and ultraviolet light that has not yet been equaled from much larger Earth based telescopes. However, other space telescopes, such as the Chandra X-ray Observatory and the Spitzer Space Telescope, have been equally as important to science as Hubble because they provided very high-resolution views of our universe in frequencies outside the visible. To learn more about Hubble, Chandra, and Spitzer space-based telescopes, go to http://hubblesite.org/ (Hubble), http://chandra.harvard.edu

(Chandra), and http://www.spitzer.caltech.edu/ (Spitzer). Although not quite yet equal to our orbiting telescopes, some of the largest Earth-bound telescopes are quickly closing the gap in optical astronomy using such technologies as adaptive optics and interferometry. In adaptive optics systems, optical systems using deformable mirrors and computers adapt to compensate for distortions introduced by Earth’s atmosphere. For more details about adaptive optics, go to http://cfao.ucolick.org/ao/ . In interferometry, multiple telescopes are used together to increase the effective telescope diameter used for viewing astronomical objects, where fainter objects can be observed with larger diameter telescopes. Interferometry has been used most effectively with Earth-bound radio telescopes. Several radio telescopes, thousand of kilometers apart, have been tied together using interferometry, essentially creating continent-sized telescopes. To learn more about interferometry, go to http://planetquest.jpl.nasa.gov/technology/technology_index.cfm

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Another significant technological advance was the introduction of spectroscopy in the late 19 th century. In spectroscopy, scientists split light from objects using a prism or screen. As scientists view the resulting spectrum of light, they see characteristic dark or bright bands (corresponding to absorption or emission, respectively) of specific light frequencies. Atoms and molecules emit or absorb light at specific frequencies, depending upon their structure. Therefore, using spectroscopy, astronomers can deduce the chemical composition of stars, galaxies, supernovae remnants, planetary atmospheres and surfaces, etc. For more details about how astronomers use spectroscopy to learn about the universe, go to http://violet.pha.jhu.edu/~wpb/spectroscopy/spec_home.html

. In the later half of the 20 th century, humans ventured into the universe. Twelve men landed on the Moon and robotic spacecraft either have visited or will visit every planet in our Solar System. These spacecraft employ similar techniques to telescopic observations, such as spectroscopy, to provide detailed information about the planets and moons they visit. Some missions, Apollo, Stardust, and Genesis, have even returned samples back to Earth (Apollo returned samples of our Moon’s soil and rocks, Stardust returned samples from the tail of Comet Temple-Tuttle, and Genesis returned particles from the solar wind). NASA maintains an excellent database detailing human and robotic exploration of the cosmos. This database includes NASA missions, as well as those sponsored by other countries, and can be found at http://nssdc.gsfc.nasa.gov/database/sc-query.html

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Performance Benchmark E.12.B.3

Students know ways in which technology has increased understanding of the universe. I/S

Common misconceptions associated with this benchmark 1. Students incorrectly think that the Hubble Space Telescope and other orbiting observatories see distant objects more clearly because they are closer to these objects.

The Hubble Space Telescope orbits at an altitude of about 550 km (about 340 miles). This is only about 9% greater than the average distance between Earth’s surface and its center. Furthermore, astronomical distances are considerably greater than the size of Earth. The nearest celestial object to Earth is the Moon, at an average distance of about 380,000 km (about 240,000 miles). This puts Hubble about 0.14% closer to the Moon than an observer on Earth’s surface. Almost all other objects are from millions to more than a billion trillion kilometers from Earth, making Hubble virtually the same distance from these objects as Earth’s surface. Although the Chandra X-ray Observatory and Spitzer Space Telescope orbit farther from Earth than Hubble, when considering astronomical distances, these are also virtually the same distance as telescopes on the Earth’s surface. Orbiting telescopes provide outstanding images of dim objects because they are not affected by the interference of Earth’s atmosphere. To learn more about why we have orbiting telescopes, go to http://coolcosmos.ipac.caltech.edu/cosmic_classroom/multiwavelength_astronomy/multi wavelength_astronomy/orbit.html

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2. Students incorrectly think that radio telescopes detect sounds from space.

Students incorrectly believe that radio telescopes detect sound waves emanating from space. While sound waves can travel through the interstellar medium, the density is so low in space that the sound wave frequencies are tens of octaves below human hearing and intensity of sound waves are just barely measurable. In essence, space is silent. Radio telescopes detect radio waves, which are a low frequency form of light. Like all light waves, radio is produced when electrons are accelerated. Radio waves are often produced by synchrotron radiation, where electrons are accelerated as they spiral around intense magnetic field lines. Black holes and neutron stars create such intense magnetic field lines and radio telescopes have been instrumental in our understanding of these phenomena. To learn more about radio astronomy, go to http://www.nrao.edu/whatisra/ . 4

3. Students incorrectly believe that humans have visited other planets in our Solar System.

Many students incorrectly think that humans have explored other planets, such as Mars. The root of this misconception may lie with the fertile science fiction imagery presented by movies and other popular media. Along with this misconception is the incorrect belief that samples from other planets have been returned to Earth. In fact, only twelve men have visited another celestial body, Earth’s Moon. These twelve men were part of NASA’s Apollo Missions in the late 1960s and early 70s. Since that time, there has been a somewhat active astronaut program by the United States, Russia, and other countries, but no human has ventured beyond Earth orbit. Some students incorrectly believe that humans have not been on the Moon. In recent years, programs on television have perpetuated this hoax. These programs use a form of pseudo science to make a convincing argument. However, there are some excellent Web sites that refute each false claim made by such programs. Once such site is http://www.badastronomy.com/bad/tv/foxapollo.html

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Performance Benchmark E.12.B.3

Students know ways in which technology has increased understanding of the universe. I/S

Sample Test Questions

1.

Which image best represents the orbit of the Hubble Space Telescope compared to the orbit of Earth’s Moon? a.

b.

c.

d.

Image A Image B Image C Image D 2.

The Hubble Space Telescope can detect very dim astronomical objects because it a.

is closer to these objects than telescopes at Earth’s surface. b.

c.

d.

has very large lenses to magnify very distant objects. orbits beyond the distorting effects of Earth’s atmosphere. has larger mirrors than any of the Earth-bound telescopes. 6

3.

Human astronauts a.

have been landing on the Moon with regularity since the Apollo 11 Mission in July 1969, but have not ventured farther. b.

landed on the Moon and Mars, but have not ventured to these objects or c.

beyond since the late 1970s. landed on the Moon in the late 1960s and early 1970s and then landed on d.

Mars in the late 1990s. landed on the Moon with the Apollo Missions in the late 1960s and early 1970s and have not returned. 4.

Radio telescopes are used by astronomers to a.

detect sound waves from space that are emitted by distant space objects. b.

c.

detect electromagnetic radiation emitted from distant space objects. transmit messages to space in hopes of contacting extraterrestrial d.

intelligence. transmit signals that reflect off of space objects to determine their distances. 5.

Which invention revolutionized our scientific understanding by providing evidence that the Earth is not the center of the universe? a.

Telescopes b.

c.

d.

Compasses Astrolabes Rockets and Spacecrafts 7

Performance Benchmark E.12.B.3

Students know ways in which technology has increased understanding of the universe. I/S

Answers to Sample Test Questions

1. (b) 2. (c) 3. (d) 4. (b) 5. (a) 8

Performance Benchmark E.12.B.3

Students know ways in which technology has increased understanding of the universe. I/S

Intervention Strategies and Resources

The following list of intervention strategies and resources will facilitate student understanding of this benchmark.

1.

Build a Telescope Lesson

One of the best ways for students to learn how a telescope works and its importance to science is to have them actually build a telescope. Building a simple refracting telescope is not difficult and a good lesson to serve as a guide is found at http://www.life.uiuc.edu/boast1/sciencelessons/telescopes.htm

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2.

NASA Imaging Activities

NASA’s Chandra X-ray Observatory has created a directed-inquiry activity that guides students through the techniques that scientists use to create images from raw data. This is a particularly powerful activity that helps students understand how we visualize light in frequencies beyond the visible. The activity can be used at different grade levels and is found at http://chandra.harvard.edu/edu/formal/imaging/index.html

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3.

Telescope and Robotic Exploration Activity

NASA’s Phoenix Mars Mission has modified an activity originally developed by the Mars Education Program. Although this activity, called “Blind Mice,” is targeted for elementary students, it can be adapted for secondary students. The activity has students reflect on how scientists use Earth-bound and space-based telescopes, as well as robotic exploration missions, to gather different information about the universe. The activity is found at http://phoenix.lpl.arizona.edu/pdf/lesson_8.pdf

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4.

Multi-frequency Astronomy

The National Radio Astronomy Observatory has created a tour of the constellation Orion from all the different frequencies of light. This is a computer based demonstration that may be best easily shown to students as a class. This tour is found at http://www.gb.nrao.edu/~rmaddale/Education/OrionTourCenter/index.htm

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