Flashcards
astronomy october term test flashcards
Cards in this deck (29)
- 1What is our physical place in the Universe?Earth
Solar System
Milky Way Galaxy
Local Group
Local Supercluster
Universe - 2Describe our cosmic origins and why we say that we are "star stuff"The Universe began in the Big Bang, which produced only two chemical elements: Hydrogen & Helium. The rest have been produced by stars; which is why we are "star stuff."
- 3Why does looking into space mean looking back in time?Light takes time to travel through space. Thus, when we look farther away, we see light that has taken a longer time to reach us.
- 4How do human time scales compare to the age of the Universe?On a cosmic calendar that compresses the history of the Universe into one year, human civilization is just a few seconds old.
- 5Describe the basic motions of "spaceship Earth."Earth rotates on its axis once each day and orbits around the Sun once each year. Our Solar System orbits the center of the Milky Way Galaxy. Galaxies in the Local Group move relative to one another, while all other galaxies are moving away from us with expansion of the Universe.
- 6How do we know that the Universe is expanding?We observe nearly all other galaxies to be moving away from us, with more distant ones moving faster.
- 7What is a constellation?A constellation is a region of the sky.
- 8What is the celestial sphere?An imaginary sphere surrounding the Earth upon which the stars, Sun, Moon, and planets appear to reside.
- 9Why do we see a band of light called the Milky Way Galaxy in our sky?It traces the Galactic plane as it appears from our location in the Milky Way Galaxy.
- 10Describe the basic features of the local sky.The horizon is the boundary between Earth and sky. The meridian traces a half circle from due south on your horizon, through the zenith (the point directly overhead), to due north on your horizon. Any point in the sky can be located by its altitude and direction.
- 11How does the sky vary with latitude?As the celestial sphere appears to rotate around us each day, we see different portions of the paths of stars from different latitudes. The altitude of the celestial pole (north or south) is the same as your latitude (north or south) .
- 12Why are some stars above the horizon at all times?All stars appear to make a daily circle. Circumpolar stars are those for which their entire daily circles are above the horizon, which depends on latitude.
- 13What is the cause of seasons on Earth?As the Earth orbits the sun, the tilt of the axis causes different portions of the Earth to receive more or less direct sunlight at different times of the year. The two hemispheres have opposite seasons. The summer solstice is the time when the northern hemisphere gets its most direct sunlight; the winter solstice is the time when the southern hemisphere gets its most direct sunlight. The two hemispheres get equally direct sunlight on the spring and fall equinoxes/
- 14How does the night sky change through the year?The visible constellations at a particular time of night depend on where the Earth is located in its orbit around the Sun.
- 15Why do we see phases of the Moon?At any time, half the Moon is illuminated by the Sun and half is in darkness. The face of the Moon that we see is some combination of these two portions, determined by the relative locations of the Sun, Earth, and Moon.
- 16Why do planets sometimes seem to move backwards relative to the stars?Apparent retrograde motion occurs over a period of a few weeks to a few months as the earth passes by another planet in its orbit.
- 17What are Kepler's three laws of planetary motion?(1) The orbit of each planet is an ellipse with the Sun at one focus. (2) As a planet moves around its orbit, it sweeps out equal areas in equal times. (3) More distant planets orbit the Sun at slower average speeds, following a precise mathematical relationship (p2 = a3).
- 18How can we distinguish science from nonscience?It's not always easy, but science generally exhibits at least three hallmarks. (1) Modern science seeks explanations for observed phenomena that rely solely on natural causes. (2) Science progresses through the creation and testing of models of nature that explain the observations as simply as possible. (3) A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with the observations.
- 19What is a theory in science?A model that explains a wide variety of observations in terms of just a few general principles, which has survived numerous tests just to verify its predictions and explanations.
- 20What is the basic structure of an atom?An atom consists of a tiny nucleus made of protons and neutrons surrounded by a "smeared out" cloud of electrons that give the atom its size.
- 21In what way is light a wave?Light is an electromagnetic wave - a wave of vibrating electric & magnetic fields - characterized by a wavelength and a frequency and travelling at a speed of light.
- 22In what way is light made of particles?Light comes in individual photons, each with a specific energy that depends on its frequency.
- 23How are wavelength, frequency, and energy related for photons of light?Frequency increases when wavelength decreases, and vice versa. Energy is proportional to frequency.
- 24List the various forms of light that make up the electromagnetic spectrum.In order of increasing frequency (energy), the forms of light are: radio, infrared, visible light, ultraviolet, X-rays, and gamma-rays.
- 25What are the two rules of thermal radiation?(1) Hotter objects emit more total radiation per unit area. (2) Hotter objects emit photons with a higher average energy.
- 26Are there any material objects that don't give off any light?No. All objects radiate light by virtue of their temperatures. This light is called thermal radiation.
- 27What is the main purpose of a telescope?A telescope is designed to collect as much light as possible. It also improves resolution and magnifies images.
- 28How do astronomers use the light collected by a telescope?(1) Imaging: use a camera to take pictures (images), photometry measure total amount of light from an object.
(2) Spectroscopy: use a spectrograph to seperate the light into its different wavelengths (colours) - 29—
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- Astronomy Flashcards on astronomy october term test flashcards, created by Michelle Ballentyne on 24/10/2017.
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