Q&A Hero

Q: If we increased the pressure in a gas, how will its spectral lines be affected?

Q: Explain what types of information can be obtained from a line spectrum.

Q: A binary star system is one with two stars orbiting each other. How can the Doppler Effect be used to find binary stars whose orbital plane is along our line of sight and determine their periods?

Q: What information about a star can be inferred from its Doppler shift?

Q: Explain how Bohr's model creates emission and absorption lines in the spectrum.

Q: Explain how the Zeeman effect allows us to study stellar magnetic fields.

Q: State the relationship between frequency, photon energy, and wavelength.

Q: If the magnetic fields are very strong, such as around sunspots, how are spectral lines affected by the Zeeman effect?

Q: According to Kirchhoff's first law why do dense, hot bodies create the type of spectrum they do?

Q: The Great Nebula in Orion, M-42, is a low-density cloud of hot gas. Use Kirchhoff's laws to describe its spectrum.

Q: Give at least two advantages of the Kelvin temperature scale for astronomers.

Q: How does human vision's peak in color sensitivity relate to the Sun?

Q: What do gamma rays, X-rays, light, and radio waves all have in common?

Q: What do infrared and ultraviolet waves have in common? How do they differ?

Q: Newton found that when light passed through a prism, it was dispersed into the component colors. Which bent the least, and why?

Q: How can you determine the distance to a spacecraft from the time it takes its radio signal to reach Earth?

Q: What two regions of the electromagnetic spectrum are best utilized by ground-based astronomers, and why?

Q: No one can hear you scream (or fire a weapon) in space, regardless of the Hollywood special effects. Explain why.

Q: An AM station is broadcasting at 980 kHz, while an FM station up the road is assigned 98 MHz. How do their carrier waves compare?

Q: How do sound and light waves differ?

Q: Why can't we be certain that the Andromeda Galaxy exists today?

Q: The energy of the photon depends on its ________.

Q: The most energetic photons are ________.

Q: An electron has a ________ electric charge.

Q: How can astronomers determine the mass of the Sun?

Q: According to Newton's third law, the Voyager probes pulled just as hard on Jupiter as it did on them when they flew past it. Why were they accelerated enough to leave the solar system but Jupiter still is in orbit about the Sun?

Q: Explain how Kepler's laws allow us to use the motion of an asteroid to find its average distance from the Sun.

Q: While the Copernican model was simpler than Ptolemy's, it was no more accurate in predicting planetary behavior at first. How did Kepler improve it?

Q: Explain how the telescopic discoveries of Galileo could be used in support of Copernicus.

Q: How would Ptolemy explain the rising of the Sun? Contrast this to Copernicus' explanation of the same event.

Q: Why argument did the Aristotelian school present to reject the concept of Aristarchus that the Earth could be revolving around the Sun? Why was it wrong?

Q: Why was Copernicus' model much simpler than Ptolemy's?

Q: Why do Newton's Laws show a force must be acting on the planets?

Q: How do the two factors (mass and distance) in Newton's law of gravitation each affect the force on the two bodies?

Q: According to Newton's first law, if a body is moving in the absence of any net external force, describe the continuing motion of the object.

Q: Explain how the eccentricity describes the shape of an ellipse.

Q: What did Galileo discover when looking at the Sun with his telescope, and how did this support Copernicus?

Q: The speed of light (and radio waves) is 300,000 km/s. How far away is a spacecraft if its radio signal takes 10 minutes to reach Earth?

Q: What did Galileo discover through his telescope when he looked at Jupiter, and how did it refute the Ptolemaic model?

Q: How did Tycho's detailed observations of Mars' brightness help show that its orbit could not be circular?

Q: What is meant by the astronomical unit?

Q: What "imperfections" on the Moon were visible to Galileo's telescopes?

Q: How did Ptolemy explain the retrograde motion of Mars?

Q: How did Ptolemy explain the retrograde motion of Venus?

Q: Newton found that gravity varied with the ________ of the distance between the two bodies pulling on each other.

Q: According to Newton's second law, when the same force acts on two bodies, the body with the larger mass will have the ________ acceleration.

Q: In Newton's first law, the ________ of a body causes it to resist changes in its motion

Q: According to Newton, the gravity of the ________ is needed to explain planetary orbits.

Q: According to Newton's laws, the planets orbit the Sun due to ________.

Q: Kepler's theories were based on the very accurate observations made by ________.

Q: While both Ptolemy and Copernicus assumed all orbits were ________, Kepler's first law corrected this and made planetary motion predictable.

Q: The three laws of planetary motion by ________ allowed us to predict planetary motion.

Q: The ________ hypothesis is that the Earth does not occupy any special place in the universe.

Q: For Galileo, the observation of the phases of ________ proved that Ptolemy's geocentric model with epicycles was wrong.

Q: Galileo's discovery of four moons orbiting ________ provided new support for the ideas of Copernicus.

Q: The "guest star" observed by the Chinese in 1054 is now known to have been a ________.

Q: When Earth overtakes Mars, the outer planet retrogrades near ________.

Q: The time for a planet to revolve around the Sun is its ________.

Q: The model of ________ used circular deferents and epicycles in a geocentric universe to explain planetary motions.

Q: Ptolemy's model was ________, with the Earth fixed in the center of the universe.

Q: The mean distance between the Earth and Sun is called the ________.

Q: Because he failed to observe stellar ________, Aristotle wrongly concluded we could not be in orbit around the Sun.

Q: If the distance between two asteroids is doubled, the gravitational force they exert on each other will A) also be doubled. B) be half as great. C) be one fourth as great. D) will be 1/16 as great. E) be four times greater.

Q: How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU? A) 5 B) 10 C) 25 D) 100 E) 250

Q: A circular orbit would have an eccentricity of A) 0. B) between 0 and 0.5. C) between 0.5 and 1. D) exactly 1.0. E) infinity.

Q: The force of gravity varies with the A) product of the two masses. B) inverse of the distance separating the two bodies. C) inverse square of the distance separating the two bodies. D) Both A and B are correct. E) Both A and C are correct.

Q: A planet whose distance from the Sun is 3 AU would have an orbital period of how many Earth-years? A) 3 B) C) D) 9 E) 81

Q: When a planet's orbit takes it closest to the Sun, it's called A) vernal equinox. B) aphelion. C) perihelion. D) crossing the ecliptic. E) none of these; a planet's distance from the Sun never changes.

Q: Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as A) elliptical, not circular. B) much larger than Copernicus had envisioned. C) around the Sun, not the Earth. D) being on equants instead of epicycles. E) complex, with epicycles to account for retrograde motions.

Q: Tycho Brahe's contribution to Kepler's Laws of Planetary Motion were A) his detailed and accurate observations of the planets' positions. B) his observations of Jupiter's moons. C) a mathematical explanation of epicycles. D) a precise lunar calendar. E) the correct explanation of lunar phases.

Q: Galileo found the rotation period of the Sun was approximately A) a day. B) a week. C) a month. D) three months. E) a year.

Q: Which of these observations of Galileo refuted Ptolemy's epicycles? A) the complete cycle of Venus' phases B) the rotation of sunspots across the Sun's surface C) the revolution of Jupiter's moons around it D) the craters on the Moon E) the visibility of many more stars with the telescope

Q: Which of these was NOT seen telescopically by Galileo? A) sunspots B) Venus' phase cycle C) Four moons around Jupiter D) stellar parallax E) craters and mare on the Moon

Q: A fatal flaw with Ptolemy's model is its inability to predict the observed phases of A) the Sun during an eclipse. B) the Moon in its monthly cycle. C) Mercury and Venus. D) Mars and Jupiter. E) Jupiter and Saturn.

Q: According to Copernicus, the retrograde motion for Mars must occur A) at inferior conjunction, when Mars laps the Earth and passes between us and the Sun. B) at superior conjunction, when Mars lies on the far side of the Sun. C) at quadrature, when Mars lies exactly 90 degrees east or west of the Sun. D) at greatest elongation, when Mars can get up to 47 degrees from the Sun. E) at opposition, when the Earth overtakes Mars and passes between Mars and the Sun.

Q: According to Copernicus, retrograde motion for Venus must occur around A) inferior conjunction, when it passes between us and the Sun. B) quadrature, when the planet is 90 degrees away from the Sun. C) greatest elongation, when the planet is farthest from the Sun. D) superior conjunction, when the planet is on the far side of the Sun. E) opposition, when the planet lies opposite the Sun in the sky.

Q: Copernicus' Heliocentric theory explains that A) planetary orbits are elliptical in shape. B) the Sun lies at one focus of an ellipse. C) Venus retrogrades when she overtakes us at inferior conjunction. D) all planets lie between the Sun and Earth. E) Mars will retrograde when it reaches a certain position on its epicycle.

Q: In Ptolemy's geocentric model, the normal eastward motion of the planets was along A) a deferent. B) an epicycle. C) a retrograde loop. D) an ellipse. E) the equant.

Q: In Ptolemy's geocentric model, retrograde motion occurs when the planet is closest to us, on the inside portion of the A) deferent. B) ellipse. C) epicycle. D) equant. E) ecliptic.

Q: Copernicus believed the Earth was the center of all celestial motion.