What is Clocks: Definition and 240 Discussions

A clock is a device used to measure, verify, keep, and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units: the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.
Some predecessors to the modern clock may be considered as "clocks" that are based on movement in nature: A sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, a well-known example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments. A major advance occurred with the invention of the verge escapement, which made possible the first mechanical clocks around 1300 in Europe, which kept time with oscillating timekeepers like balance wheels.Traditionally, in horology, the term clock was used for a striking clock, while a clock that did not strike the hours audibly was called a timepiece; this distinction is no longer made. Watches and other timepieces that can be carried on one's person are usually not referred to as clocks.
Spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished. The next development in accuracy occurred after 1656 with the invention of the pendulum clock by Christiaan Huygens. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The mechanism of a timepiece with a series of gears driven by a spring or weights is referred to as clockwork; the term is used by extension for a similar mechanism not used in a timepiece. The electric clock was patented in 1840, and electronic clocks were introduced in the 20th century, becoming widespread with the development of small battery-powered semiconductor devices.
The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates at a particular frequency.
This object can be a pendulum, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves.
Clocks have different ways of displaying the time. Analog clocks indicate time with a traditional clock face, with moving hands. Digital clocks display a numeric representation of time. Two numbering systems are in use: 24-hour time notation and 12-hour notation. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays. For the blind and for use over telephones, speaking clocks state the time audibly in words. There are also clocks for the blind that have displays that can be read by touch. The study of timekeeping is known as horology.

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  1. J

    Will two clocks be synchronized after a period of time dialation?

    As 2 time pieces are moving relative to each other in a non accelerated reference frame, they will both see the other as slow. As time goes on, the amount of observed error in the other clock will continue to grow greater and greater. Let's say that after a while both clocks are 10 hours ahead...
  2. P

    Synchronization of Earth clocks

    If we have two clocks, one stationary at surface of Earth, and the other one very slowly moved at the surface of Earth, in the direction of Earth rotation, the clock that made the trip should be running ahead of the same stationary clock once it makes a complete circle and stops where it started...
  3. W

    Special relativity clocks observed from two frames

    Homework Statement Observers S and S' stand at the origins of their respective frames, which are moving relative to each other with a speed of .6c. Each has a standard clock, which, as usual, they set to zero when the two origins coincide. Observer S keeps the S' clock visually in sight...
  4. K

    I understand time dilation with light clocks, but

    Imagine I were to make a light clock by placing two mirrors facing each other, with a photon bouncing between them vertically, such that one complete round trip for the photon takes exactly one second. I understand that if this contraption were moving horizontally at significant speed, an...
  5. D

    Clocks Falling into Gravity Wells: Variation Observed?

    As I understand it, clocks run relatively slower the closer they are to the center of a "gravity well" and also each other clock for a pair of observers moving relatively to each other appears to be running slower, relative to each frame of reference. So, start with a pair of highly accurate...
  6. P

    Question about calculating time dilation of clocks at sea level

    I am trying to understand how relativity explains that clocks all over the globe count at about the same rate at sea level. One of the papers that I have looked at is "The global positioning system, relativity, and extraterrestrial navigation" at...
  7. L

    A few simple questions about clocks moving slow relative to observers

    Hello, I want to make these questions as simple as possible, so that no one answering it will have to use any mathematics or formulas to explain it. I don’t mean this in a disrespectful way, I’m simply interested in the specific issues. Assume that I am an observer on earth, and a...
  8. C

    Repositioning clocks: continuing from the switch paradox

    In this hypothetical, an experiment is going to be conducted concerning the repositioning of clocks. two clocks are placed at the leading end of a vessel, that is 1 light second long, to an observer at rest relative to it. This vessel is shot into space from an observation station at...
  9. C

    Unlocking the Mysteries of Atomic Clocks

    So I am reading about how an atomic clock works , So they shoot microwaves at cesium atoms and the right microwaves will cause an electron to jump up to the next energy level , are they using this to tune the microwave laser so they know what the frequency of the laser is . and when they...
  10. C

    Do magnetic fields affect the speed of light in the Pound-Rebka experiment?

    Do clocks tick at different rates in different magnetic fields .
  11. J

    Do the Principles of Special Relativity Require Synchronized Clocks in K and k?

    Consider the following properties of SR clocks. The coordinate systems are the usual K( X,Y,Z,T) and k( x,y,z,t) where k is the coordinate whose origin moves in the positive direction of K. 1.The clocks of K are synchronized with each other using the procedure given in the 1905 paper. Also...
  12. S

    Design digital logic clocks with given frequencies

    Homework Statement Assume you have a symmetrical clock at 100MHz. Design a logic circuit with four outputs of clocks at 100MHz, 50MHz, 25MHz, and 12.5MHz. The logic circuit should have 2 inputs to select output clock rate. Homework Equations N/A The Attempt at a Solution For...
  13. Fra

    Understanding Time and Clocks in Relation to Observers

    A simple question, but I wonder how different people think of this wrt internal vs external clocks. It's been argued rightfullly that a satisfactory formulation of a measurement theory that is to be consistent with gravity (I use this word intead of QM, to not confused current QM with a...
  14. G

    Why do clocks tick slower and faster in different depths of gravity?

    Something just occurred to me today. I've puzzled for some time why it is that normal clocks tick slower when in a deeper depth of gravity but that pendulum clocks do the opposite and actually tick faster when in a deeper depth of gravity. Can time tick slower and faster? I believe I now...
  15. edpell

    Acceleration does not effect clocks?

    Imagine in empty space a pendulum consisting of a small weight suspended above a large weight and displace so that it swings back and forth with period T. Now imagine accelerating (in the right direction) so that the effective gravity felt by the small weight increases. The period will then...
  16. Y

    Clocks running slower is an illusion

    I read this somewhere on a physics forum recently What is meant by this statement? I spent a short while thinking about it but can't follow what the person is going on about. Maybe I misunderstood him, but he seems to be claiming that time dilation is actually an illusion.
  17. J

    Slow clocks on moving body is an illusion?

    Hi, I chanced upon https://www.physicsforums.com/showthread.php?t=321935 and read Doc AI's reply basically saying: if 2 bodies moving near speed of light relative to each other, the clocks on the other body will appear slower on either body. And I think this should theoretically mean the...
  18. M

    Constancy of light speed implied in time and clocks

    From "The conceptualization of time and the constancy of the speed of light", Vasco Guerra and and Rodrigo de Abreu. I just came across this article which proves that the speed of light had to be constant by just assuming "good" clocks record time correctly irrespective of orientations...
  19. D

    A & B Clocks: Why Velocity Time Dilation is Not a Paradox

    We have two clocks, A and B. B is moving with constant velocity with respect to A. From the reference frame of A, B is running slow. From the reference frame of B, A is running slow. Why is this not a paradox?
  20. jinksys

    Time Dilation: Concepts of Modern Physics by Beiser

    I'm reading Concepts of Modern Physics by Beiser, and the chapter example says: A spacecraft is moving relative to earth. An observer finds that in one hour, according to her clock 3601s elapse on the spacecraft 's clock. What is the craft's velocity relative to earth? (This is not a...
  21. A

    About how light clocks would work

    Hi. I've been reading about relativity and time dilation. Also watched some visualisations on youtube. The question I have is about the light clocks which are always used to demonstrate the theories. Explanations always show the light beam on the moving clock moving in a diagonal motion...
  22. J

    Gravitational Effects on Atomic Clocks and Other Forces

    I was thinking that as far as I know, an atomic clock, and a mechanical clock, or a tuning fork clock might be affected differently by gravitation and acceleration. Is there any experimental verification of this? I'm trying to figure out if atoms will decay faster and that is it. Or if...
  23. D

    Clocks & Boxcars: Get Solution to Problem

    Can someone look at the attachment and tell me where I went wrong thanx
  24. D

    Synchronising Clocks: Will They Stay in Sync?

    if you at rest wrt 2 clocks and then you synch the 2 clocks and then you move one of the clocks will they still be synchronised according to you?
  25. Z

    Atomic clocks and temperature

    Are atomic clocks such as the NIST-F1 Cesium Fountain Atomic Clock http://tf.nist.gov/cesium/fountain.htm" sensitive to the ambient temperature Or do they keep very accurate time regardless of the ambient temperature?
  26. MTd2

    Why computer clocks hardly goes above ~5GHz?

    What is the reason chips won't go above 5GHz nowadays, independtly of the micro archicteture? Special cooling makes them go a little bit above, but it's always around this scale. Until 2002 computers were increasing frequency in every generation of produts, but it mostly stopped since then. Why?
  27. B

    What are the physics of changes of timecounts of accelerated/decelerated clocks?

    The Fitzgeral-Lorentz transformation equations describe what is the time, e.g., the timecount, of a clock which has been accelerated or decelerated from an initial reference frame into a different reference frame. If two identical clocks, C1 and C2, are in an initial reference frame, K, and C2...
  28. P

    Moving clocks and time dialation question

    i'm revising for an exam and have this question posed (this isn't homework) what is the maximal velocity for a clock being transported from london to new york if the time difference to a stationary clock should be less than 10^-8 seconds. i'm not allowed to use calculators. i've tried...
  29. M

    Umsynchronization of clocks.

    Hello all. If two clocks are at rest relative to each other and are synchronized using the usual Einstein synch procedure, under what conditions will they appear to be unnsynchronized to another observer who has always been at rest relative to them? Also, if an observer previously moving...
  30. L

    Building 10 Synchronized 7-Segment Clocks

    Hey! I need to build 10 7segment clocks that will be synchronized among themselves. [Just a regular clock that will display the current hour, only 10 of those, and in different places in the room]. I thought about building a microProcessor-based clocks that will be synchronized among...
  31. S

    Why each GPS satellite holds four atomic clocks?

    Each of the 24 GPS satellites holds four atomic clocks! Why four and not one or two? They are not cheap! Thanks
  32. F

    Clocks out of Sync (Special Relativity)

    There are 2 identical 1m rulers (same rest length), and one if going past the other at some velocity. Each ruler has a clock every 10 cm. According to the fixed clock, the moving ruler's clocks will appear to be moving slow, and out of sync. (if t=0 when the rulers pass each other, then the...
  33. D

    Three Digital Clocks at Different Speeds

    Homework Statement Three digital clocks A, B, and C run at different rates and do not have simultaneous readings of zero. Figure 1-6 shows simultaneous readings on pairs of the clocks for four occasions: ___________312_________________512__ Clock A ___25______125_______200_______290__...
  34. D

    Four Clocks Problem: Find Time When All 4 Clocks are Same

    Four 12 hour clocks are lined up. The first reads 10:41 and loses 2hours and 24 minutes a day. The second reads 4:50 and loses 45 minutes a day. The third reads 3:45 and gains 1hour and 20 minutes a day. The fourth reads 1:05 and keeps perfect time. How long will it be before all four clocks...
  35. jtbell

    How two clocks can each run slow in the other's reference frame

    People often have trouble visualizing how time dilation can be "mutual" in special relativity. That is, if you have two clocks moving with respect to each other, in each clock's rest frame the other clock runs slower. The following example illustrates how this can be possible without...
  36. A

    SR and Light Clocks - Confused

    Hello all. I wonder if you could help explain something to me. No matter how much I read I am not sure if my understanding of special relativity is correct. My confusion is with respect to a light clock constructed as one mirror above the other and a photon reflecting between the two mirrors...
  37. B

    Absolute simultaneity with Einstein synchronized clocks?

    1. Absolute simultaneity with standard synchronized clocks In an one space dimensions approach we propose the following scenario. At the origin O of the inertial reference frame I we find a clock C0(0) and a source of light S(0). An observer R’ moves with constant speed V in the positive...
  38. N

    Ok so u have two twins, both have clocks set to zero.

    ok so u have two twins, both have clocks set to zero. One of them takes off at close to the speed of light. That twins clock would run slow. However If the twin were to reset both clocks and take of at the same speed in the opposite direction for the same distance. would the clocks be off by...
  39. R

    Synchronised Clocks in Motion: Einstein's Method and the Observer's Experiment

    Referring to Fig A We have a spaceship in the spaceship is an observer at point D. There is also 4 identical clocks, clock 1 (C1), clock 2 (C2), clock 3 (C3) and clock 4 (C4). At the same point as the observer is a light so there is a light at point D as well. The observer also has...
  40. R

    How Can Clock Synchronization Be Achieved in a Moving Spaceship?

    Synchronising clocks Referring to fig 1 I want to synchronise two clocks. I have a spaceship traveling at v in the direction of the arrow. In the ship I have two identical clocks one at point A (clock1) and on a point D(clock 2). I also have a light source at point B. Length AB = length...
  41. A

    Atomic clocks & general relativity

    Hi all, I have recently been listening to one of Professor Richard Wolfson's physics lectures, and a question has occurred about an aspect of general relativity; that time 'slows down' in strongly curved spacetime. In this particular lecture, he mentions an experiment done some years ago in a...
  42. R

    Clock Synchronisation in Stationary and Accelerated Frames

    if 2 clocks are synchronised in a stationary frame of refernece and then that frame of ref is accelerated up to a constant velocity will the clocks still be synchronised ?
  43. R

    Understanding Synchronised Clocks: Definition and Explanation

    I was wondering what is the definition of synchronised clocks...is it "2 clocks in a frame of reference that measure time at the same rate and appear to an observer within that same frame of reference to show the same time"
  44. A

    Stationary and moving clocks

    1. Let S be an x-coordinate system. The origin of S is located at x = 0m. Let S' be an x'-coordinate system. The origin of S' is located at x' = 0m. This information is not sufficient in order to determine where the origin of one system is located with respect to the other. 2. Let system S'...
  45. Y

    Proper time of accelerated clocks

    In other threads the topic of how the proper time of a clock under acceleration has come up a number of times so I have decided to analyse this subject in a little more detail. For this analysis we have these conditions: a)Two clocks are initially at rest separated by a distance L_o along...
  46. M

    Can Atomic Clocks Accurately Measure Time in Accelerating Bodies?

    First I'm not a native English speaker so sorry for grammar errors . Ok let's start my hobby is to learn things and I tried to study relativity while I where reading some example of time dilation in atomic clocks. However I remembered something the speed of a electromagnetic wave is equal to...
  47. A

    Exploring the Effects of Relativity on Clocks

    Now according to special relativity when in the case of two people traveling at different speeds have their own clocks running differently depending on their velocity I have understood the theoritical part of this that as c=d/t and as d= space and t= time and c= velocity of light . thus...
  48. C

    Calculate Magnitude & Angle of Clock's Vector Displacement

    The minute hand of a wall clock measures 12 cm from its tip to the axis about which it rotates. The magnitude and angle of the displacement vector of the tip are to be determined for three time intervals. What are the (a) magnitude and (b) angle from a quarter after the hour to half past, the...
  49. B

    A question with the readings of synchronized clocks

    Consider that from the origin O of the inertial reference frame O start at the origin of time a particle that moves with speed u<c and a photon with speed c both in the positive direction of the OX axis. At each point of that axis we find a clock all the clocks being synchronized following the...
  50. P

    Clocks on spaceship travelling at the speed of light

    Homework Statement Hi guys, I'm in a Physics for poets class? Could you , please, help me with these questions? Suppose you are watching a spaceship go past you toward the right at close to the speed of light. 1. How do the clocks on the spaceship appear to run compared to your own clock...
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