Concept explainers
The original “clock” used to define the length of the second was the daily rotation of Earth about its axis. Why has this clock been replaced by one based on the oscillation period of light waves emitted by atoms like cesium and rubidium?
The reason clocks based on the daily rotation has been replaced by the oscillation period of light waves emitted by atoms like cesium and rubidium.
Answer to Problem 1CA
The time period of the earth’s rotation is not fixed and to have a proper clock, it requires giving error free time period which is not possible. Hence, it is replaced by the oscillation period of light waves emitted by atoms like cesium and rubidium. The oscillation period of light waves emitted by atoms is fixed. Hence, the clock will give error free time.
Explanation of Solution
Introduction:
The earth’s rotation period is four minutes less than what we call a day. Due to this, the Sun’s position in the sky at noon is roughly fixed, but the stars slowly drift apart. So, the stars which are overhead today will slowly move in the sky until they will be overhead at noon 6 months apart.
If instead, a day was defined to be the time taken for earth to rotate, then according to above stated reason, the sun will be overhead on some day at midnight. The time period for oscillation of light waves emitted by the atoms of cesium and rubidium is always fixed. Hence, they will always give error free time period forever.
Conclusion:
The time given by the earth’s rotation won’t be same everyday as the earth’s rotation speed is not fixed. Hence, the clocks based on it will give wrong time. Hence, we use clocks based on the oscillations of light waves emitted by atoms like cesium and rubidium.
Want to see more full solutions like this?
Chapter 1 Solutions
Inquiry into Physics
- A house is advertised as having 1 420 square feet under its roof. What is area in square meters? (a) 4 660 m2(b) 132 m2 (c) 158m2 (d) 132 m2 (e) 10.2m1arrow_forwardWhen observed from the sun at a particular instant, Earth and Mars appear to move in opposite directions with speeds 108,000 km/h and 86,871 km/h, respectively. What is the speed of Mars at this instant when observed from Earth?arrow_forwardThe speed of light is about 3 x 108 meters per second. The Millennium Falcon is traveling from Earth to Mars at the speed of light. The distance between the Earth and Mars fluctuates between 5.46 x 10¹0 meters and 4,01 x 10¹¹ meters. If the day the Millennium Falcon makes the "Mars Run," the distance is 2.25 x 10¹¹ meters, how long will it take them? Note: distance = rate time, and time = distance/rate Express your answer in scientific notation. Use for the multiplication. seconds Convert your answer to minutes. Include at least 3 decimal places in your answer, which can be expressed in standard notation. minutes Suppose the Millennium Falcon flies for 5 hours at the speed of light. How far will they travel? Express your answer in scientific notation. metersarrow_forward
- 1) Two identical atomic clocks are manufactured at a factory. One clock remains at the factory, and the other is transported across the country to a physics lab. When the clock arrives at the physics lab, it reads 9:00 a.m. At this same time, does the clock at the factory read a time that is before 9:00 a.m., equal to 9:00 a.m., or after 9:00 a.m.? Explain. 2) Suppose you are a traveling salesman for SSC, the Spacely Sprockets Company. You travel on a spaceship that reaches speeds near the speed of light, and you are paid by the hour. (a) When you return to Earth after a sales trip, would you prefer to be paid according to the clock at Spacely Sprockets universal headquarters on Earth, according to the clock on the spaceship in which you travel, or would your pay be the same in either case? Your goal is to get paid as much as possible. (b) Choose the best explanation from among the following: I. You want to be paid according to the clock on Earth, because the clock on the spaceship…arrow_forwardIs 3 m/s is greater than 2.9 m/s²? What is the explanation for this?arrow_forwardAll of the stars of the Big Dipper (part of the constellation Ursa Major) may appear to be the same distance from the earth, but in fact they are very far from each other. Figure shows the distances from the earth to each of these stars. The distances are given in light-years (ly), the distance that light travels in one year. One light-year equals 9.461 * 1015 m. (a) Alkaid and Merak are 25.6 apart in the earth’s sky. In a diagram, show the relative positions of Alkaid, Merak, and our sun. Find the distance in light-years from Alkaid to Merak. (b) To an inhabitant of a planet orbiting Merak, how many degrees apart in the sky would Alkaid and our sun be?arrow_forward
- A planet with mass 9.69x1023 kg orbits a star with mass 9.21x1030 kg. The orbit is circular, and the distance from the planet to the sun is 225x106 km. What is the length of a year on this planet? Give your answer in earth years (1 earth year = 31,557,600 seconds).arrow_forwardSuppose the speed of light were 1000 mi/h. You are traveling on a flight from Los Angeles to Boston, a distance of 3000 mi. The plane's speed is a constant 600 mi/h. You leave Los Angeles at 10:00 A.M., as indicated by your wristwatch and by a clock in the airport. According to your watch, what time is it when you land in Boston?arrow_forwardSuppose that, while lying on a beach near the equator watching the Sun set over a calm ocean, you start a stopwatch just as the top of the Sun disappears. You then stand, elevating your eyes by a height H = 1.70 m, and stop the watch when the top of the Sun again disappears. If the elapsed time is t = 11.1 s, what is the radius r of Earth?arrow_forward
- Given the distance from Earth to the Sun is an astronomical unit (149,597,870,700 m) and takes one year to complete a revolution around it (365.2425 days), what is the mass of the Sun? (The mass of the Earth is not needed for this problem) (6.674×10−11 m3⋅kg−1⋅s−2).arrow_forwardHow do you convert from days to years?arrow_forwardHow long should it take the voices of astronauts on the Moon to reach the Earth? Assume that the only significant time is the transit time from the Earth to the Moon, at the speed of light. Suppose that the astronaut on the surface of the Moon, the receiver on the surface of the Earth, and the centers of the Earth and the Moon are aligned. The distance between the centers of the Earth and the Moon is 384×103km, the radius of the Earth is 6.38×103km, the radius of the Moon is 1.74×103km.arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningAstronomyPhysicsISBN:9781938168284Author:Andrew Fraknoi; David Morrison; Sidney C. WolffPublisher:OpenStaxUniversity Physics Volume 3PhysicsISBN:9781938168185Author:William Moebs, Jeff SannyPublisher:OpenStax
- Physics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning