Q&A Hero

Q: Strictly speaking, the ratio of circumference to diameter for a circle equals π as we know it A) in flat space. B) on a spherical surface. C) on a saddle-shaped surface. D) all or any of the above E) none of the above

Q: The measured ratio of circumference to diameter on a disk is π when the disk is A) moving at relativistic speeds. B) rapidly rotating. C) at rest. D) all of the above E) none of the above

Q: The shortest distance between two points on a curved surface is a A) straight line. B) geodesic. C) neither of these

Q: The shortest distance between two points in flat Euclidean space is a A) straight line. B) geodesic. C) neither of these

Q: If the elliptical orbit of Mercury were more eccentric, its precession rate would be A) larger. B) smaller. C) the same. D) nonexistent.

Q: If the orbit of Mercury were perfectly circular, its rate of precession would be A) larger. B) smaller. C) the same. D) zero.

Q: Apart from the effects of other planets, the orbit of Mercury precesses because A) Mercury travels faster than any other planet. B) Mercury's orbit is nearly circular. C) of pronounced variations in Mercury's orbit about the Sun.

Q: Important support for general relativity came from studies of the precession of the orbit of A) Mercury. B) Venus. C) Earth. D) Mars. E) asteroids.

Q: A message from relativity theory is that slowing the aging process A) can occur with correct applications of physics. B) would occur if you fell into a bottomless mine shaft. C) can only happen to "the other guy."

Q: According to relativity theory, you can experience a longer youth when you A) are near a black hole. B) are near a very large gravitational field. C) travel at nearly the speed of light. D) all of the above E) none of the above

Q: If the Sun collapsed to a black hole, Earth would A) be sucked into the black hole. B) follow a straight-line path into space. C) continue in its present orbit.

Q: If the Sun collapsed to a black hole, Earth's speed in space would A) increase. B) decrease. C) remain the same.

Q: An astronaut falling into a black hole would see the universe A) red-shifted. B) blue-shifted. C) with no shift at all.

Q: In gravitational red shift, the quantity that undergoes a red shift is A) spacetime curvature. B) wave direction. C) field intensity. D) wave frequency. E) none of the above

Q: According to general relativity, a photon emitted by a star A) loses energy. B) reduces in frequency. C) is red-shifted. D) all of the above E) none of the above

Q: A clock on the surface of a shrinking star will run progressively A) slower. B) faster. C) no difference

Q: You shine a beam of monochromatic light from Earth to an astronaut friend in orbit. The light your friend receives, relative to light from an equivalent source on the spaceship, is slightly A) slower in speed. B) higher in speed. C) neither of these

Q: You shine a beam of monochromatic light from Earth to an astronaut friend in orbit. The light your friend receives, relative to light from an equivalent source on the spaceship, is slightly A) lower in frequency. B) higher in frequency. C) weaker but no different in frequency.

Q: If you move a clock from Earth to the Moon, the clock runs A) slower. B) no differently. C) faster.

Q: On a giant rotating turntable are two clocks, one at the center and the other at the rim.The clock that runs slower is at A) the center of the turntable. B) the rim of the turntable. C) either of these

Q: In accord with general relativity, a person living at the top of a skyscraper ages A) faster than a person on the ground floor. B) slower than a person on the ground floor. C) at the same rate as a person on any floor.

Q: If you move in the direction in which gravity acts, an observer at rest sees your watch running A) slower than at your starting point. B) faster than at your starting point. C) neither of these

Q: Light bends when it A) closely passes a star. B) closely passes the Moon. C) both of these D) neither of these

Q: In a 1-g gravitational field, 1 second after turning on a flashlight its beam will curve beneath a perfectly straight line by A) less than 4.9 m. B) 4.9 m. C) more than 4.9 m.

Q: Fire a cannonball with enormous speed from a hypothetical cannon and it curves due to gravity. Shine a light from a flashlight parallel to the cannon and it A) follows a straight-line path. B) curves downward as much as the cannonball. C) curves slightly upward.

Q: Inside an accelerating spaceship far from gravitational influences, a flashlight beam will A) not bend. B) curve as it would in a gravitational field equal to the acceleration of the spaceship. C) follow a semi-circular path.

Q: If you shine a flashlight "horizontally" from one wall to an opposite wall inside an accelerating spaceship in deep space, you will see the light traveling A) in a straight-line path. B) in a parabolic path. C) along the arc of a circle.

Q: If you shine a flashlight from one wall to an opposite wall inside a spaceship drifting without acceleration far from gravitational influences, the beam of light will travel A) in a straight-line path. B) in a parabolic path. C) along the arc of a circle.

Q: Inside an accelerating spaceship in deep space, a sideways-tossed ball will A) curve as it would in a gravitational field equal to the spaceship's acceleration. B) follow a straight-line path from one side of the interior to the other. C) fall in a semi-circular path.

Q: If you toss a ball "horizontally" from one wall to an opposite wall inside an accelerating spaceship in deep space, defining "up" as the direction of acceleration, the ball will hit A) below its straight-line path. B) above its straight-line path. C) neither of these

Q: According to the principle of equivalence, observations made of falling objects at Galileo's Leaning Tower of Pisa are indistinguishable from observations made in A) a spaceship orbiting in a gravitational field. B) a spaceship accelerating at g in deep space. C) any uniformly moving reference frame. D) all of the above E) none of the above

Q: In a spaceship with an acceleration more than g far from gravitational influences, with the effort it takes on Earth to do 20 pushups, you could comfortably do A) less than 20 pushups. B) 20 pushups. C) more than 20 pushups.

Q: In a spaceship that accelerates at g far from gravitational influences, with the effort it takes on Earth to do 20 pushups, you could comfortably do A) less than 20 pushups. B) 20 pushups. C) more than 20 pushups.

Q: Galileo dropped two balls of different weights and found they accelerated equally to the ground below. Einstein imagined the same result for a side-by-side drop A) without invoking gravity. B) in an accelerating vehicle. C) whether they were of the same mass or not. D) all of the above E) none of the above

Q: Compared with special relativity, general relativity is more concerned with A) acceleration. B) gravitation. C) spacetime geometry. D) all of the above E) none of the above

Q: As you recede from a steady light source, the wavelength of the emitted light appears A) longer. B) shorter. C) the same.

Q: As you approach a steady light source, the wavelength of the emitted light appears A) longer. B) shorter. C) the same.

Q: As a blinking light source uniformly accelerates away from you, you observe the blinks A) more and more frequently. B) less and less frequently. C) neither of these

Q: As a light source blinking at a steady rate approaches you at an increasing speed (accelerating toward you), the rate at which the blinks encounter you A) increases. B) decreases. C) remains the same.

Q: If the frequency of blinks for a light source appears to double as the light source approaches you, the frequency of blinks as it moves away from you at the same speed A) is halved. B) is doubled. C) stays the same.

Q: A light source blinks with a certain frequency in its own frame of reference, and the speed of light in that frame is c. When the light source approaches you, you observe an increase in A) both speed of light and frequency of blinking. B) speed of light, but not frequency of blinking. C) frequency of blinking, but not speed of light.

Q: A certain light source blinks once per second in its own frame of reference. As you recede from the blinking source, you observe the frequency of blinks to be A) less than 1 Hz. B) 1 Hz. C) more than 1 Hz.

Q: A light source blinks once per second in its own frame of reference. As you approach the blinking source, you observe the frequency of blinks to be A) less than 1 Hz. B) 1 Hz. C) more than 1 Hz.

Q: When a blinking light source moves relative to you, the speed of the light A) changes but the frequency of blinks remains constant. B) remains constant but the frequency of blinks can change. C) stays the same, as does the blinking frequency.

Q: When a moving spaceship emits regularly-spaced flashes of light, how frequently you see the flashes depends on the ship A) approaching you. B) receding from you. C) either of these D) none of these

Q: According to relativity theory, if a space trip finds a son or daughter biologically older than their parents, then the space trip is taken by the A) son or daughter. B) parents. C) either of these D) neither, it can't be done.

Q: Suppose you and your sister travel at different speeds in space and you note a slowing of her clock. Compared with her clock your sister will notice that your clock runs A) faster. B) slower. C) the same. D) need more information

Q: Harry takes a space voyage and returns to find his twin sister has aged more than he has. This is evidence that A) she has changed frames of reference. B) he has changed frames of reference. C) both have changed frames of reference. D) neither has changed frames of reference

Q: We are actually looking into the past when we look at A) a distant star. B) our physics book. C) actually both of these D) none of the above

Q: According to the special theory of relativity, while traveling at very high speed your pulse rate A) increases. B) decreases. C) remains unchanged.

Q: You look at the clock on the Big Ben Tower in London and it reads 12 noon. If you could hypothetically travel away from the clock at the speed of light and view it with a telescope, it would A) run slower than a clock in your vehicle. B) run faster than a clock in your vehicle. C) be frozen at 12 noon.

Q: The clock on the Big Ben Tower in London reads 12 noon. If you travel away from the clock at a very high speed and view it with a telescope, you would see A) run slower than a clock in your vehicle. B) run faster than a clock in your vehicle. C) be frozen at 12 noon.

Q: The Lorentz factor, γ, A) is always greater than 1 for any speed greater than zero. B) lets the time-dilation equation be expressed t = γ t0. C) both of these D) none of these

Q: Clocks on a spaceship moving at high speed relative to the Earth run more slowly when viewed from A) within the spaceship. B) Earth. C) both of these D) neither of these

Q: Compared to clocks in a stationary reference frame, clocks in a moving reference frame run A) slower. B) faster. C) at the same rate.

Q: The stretching out of time due to motion is called time A) stretching. B) dilation. C) contraction. D) warp. E) expansion.

Q: An observer moving with a light clock in a spaceship sees a light flash bouncing up and down between parallel mirrors in 1 nanosecond. An observer at rest outside the spaceship sees the same up-and-down flash in A) 1 nanosecond also. B) less than 1 nanosecond. C) more than 1 nanosecond.

Q: You and a friend can share the same space and time measurements when A) you are side by side at rest. B) you both are side by side moving at constant velocity. C) either of these D) none of these

Q: All events and all things exist in "the spacetime continuum" with coordinates A) of distances in three dimensions. B) of time. C) both of these D) none of these

Q: When you run along the hall from one classroom to another you're moving through A) space. B) time. C) both of these D) none of these

Q: Event A occurs before event B in a certain frame of reference. In another frame of reference, event A could occur A) after event B. B) simultaneous with event B. C) either of these D) neither of these

Q: Two lightning bolts are seen to strike two distant locations at the same time. Seen from a different location, the two lightning bolts A) will also be seen at the same time. B) will not be seen at the same time. C) may or may not be seen at the same time.

Q: According to Einstein, events that are simultaneous in one frame of reference A) are simultaneous in all frames of reference. B) are not simultaneous in other frames of reference. C) may or may not be simultaneous in other frames of reference.

Q: A postulate of special relativity is that the speed of light A) like all motion, is relative. B) for all observers is a constant. C) both of these D) neither of these

Q: How fast would a light beam appear to Einstein if he were traveling in the same direction at 90% of the speed of light? A) 0 B) c C) 0.1c D) 1.10c E) none of the above

Q: According to the special theory of relativity, all laws of nature are the same A) in all reference frames. B) for both linear or circular motion. C) in all uniformly moving reference frames. D) all of the above E) none of the above

Q: What is special about the ratio distance traveled per unit of time? A) it is constant for light B) it is relative to a frame of reference C) distance traveled very much depends on time

Q: The speed of light is A) relative to the frame of reference from which it is measured. B) a speed approached but never quite reached by photons. C) constant for all observers.

Q: Einstein rejected the classical idea that space and time are A) two parts of a whole. B) connected to each other. C) independent of each other.

Q: The ether theory of light propagation is A) much used. B) incomplete, but still useful. C) unexplained. D) discredited.

Q: To the surprise of Michelson and Morley, their interferometer experiment provided evidence that the speed of light is A) invariant. B) the same whether its source approaches or recedes. C) constant. D) all of the above

Q: The place from which motion is observed and measured is called A) a frame of reference. B) a starting point. C) an initial location.

Q: Relativity equations for time, length and momentum hold true for A) relativistic speeds. B) everyday low speeds. C) both of these D) neither of these

Q: When an electron and a positron meet and annihilate, the mass-energy of the particles is carried away by A) a gamma ray. B) two gamma rays, otherwise momentum wouldn't be conserved. C) nothing at all, gone.

Q: If an antimatter meteor of mass m were to strike the Earth, the amount of radiant energy produced would be A) less than mc2. B) mc2. C) 2mc2. D) none of the above

Q: When you shake an apple to and fro, you're shaking A) energy. B) nothing. C) the universe.

Q: According to the well-known equation E = mc2, A) mass and energy travel at the speed of light squared. B) energy is actually mass traveling at the speed of light squared. C) mass and energy travel at twice the speed of light. D) mass and energy are related. E) none of the above

Q: According to Einstein's theory of special relativity A) space and time are aspects of each other. B) energy and mass are aspects of each other. C) both of these D) neither of these

Q: What does c2 have in common with γ? A) they are both proportionality constants B) they have similar numerical values C) they both involve different kinds of speed D) all of the above

Q: Electrons fired in vintage TV tubes traveled at about 0.25 times the speed of light, having more momentum and energy than would be required classically to get that speed. Strictly speaking, this A) increased your electric bill. B) decreased your electric bill. C) had no effect on your electric bill.