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. Astronuc

    How many clocks are there in your home/dwelling?

    Cristo's thread "Clocks go back?" prompts me to ask the question - "How many clocks are there in your home/dwelling/abode?" I count 5 clocks in our kitchen - microwave, stove, coffee maker, wall clock (battery powered with bird sounds), and over-the-counter clock radio. One in the living...
  2. C

    Time Change in US: When Do Clocks Go Back in Illinois?

    Does anyone know when the clocks go back in the United States (specifically Illinois, if that make a difference). Here in the UK, we put them back in about an hour, but it suddenly dawned on me that you lot may not do the same as us! (I presume you do put the clocks back?!)
  3. D

    Qn regarding clocks and voltage

    urgent qn regarding clocks and voltage this is a very URGENT qn that i nid to know the answer in order to get working on my physics proj. we are supposed to calibrate or make an instrument and our grp chose to make a projection clock. so apparently, since it is a projection clock, the time on...
  4. B

    Do Clocks Run Slower in Weaker Gravitational Fields?

    It is often said that a clock will run slower in a stronger gravitational field. This is not always true. Give a case where a clock will run slower in a WEAKER gravitational field. Bob
  5. R

    Considering Relative Simultaneity - Relying on clocks instead of observers

    Einstein’s train-carriage example: A train-carriage is moving at a constant velocity v relative to the ground. An observer is stationed on the ground perpendicular to the midpoint of the train at time x relative to the ground’s frame of reference. At this time, lightning strikes the front and...
  6. S

    Time Dilation: Stationary vs. Moving Atomic Clocks

    Hello, I'm Eddie and this is my first post here. I'm almost a Junior in college going for a B.S. In chemistry but I must say that time dilation is one of the most interesting things in science. I was wondering if anyone has actual figures with regards to the difference in time between a...
  7. R

    Temperature and speed of clocks

    Does temperature affect all clocks - do clocks become slower at higher temperatures (an oscillating inductor -capacitor circuit would slow down because of higher electrical resistance in the wires)? Is high temperature the reason why time stops at the time of the Big Bang?
  8. D

    Medical Internal Clocks: Strange Anecdote of Accurate Timing

    something strange happened to me recently, although this is just an anecdotal story, so i appreciate that what i thought had happened may not have been the case. anyway, I've noticed that if my alarm clock is consistently set to say, 7 AM, i will wake up roughly around that time even if I've...
  9. wolram

    Exploring Cosmic Clocks with General Relativity

    http://arxiv.org/abs/gr-qc/0702082 Cosmic clocks, cosmic variance and cosmic averages Authors: David L. Wiltshire Comments: 72 pages, 5 figures, typos fixed; further summary at this http URL Cosmic acceleration is explained quantitatively, purely in general relativity, as an apparent...
  10. D

    What Causes Clock Desynchronization in Relativity?

    Homework Statement At what speed does a clock have to move in order to run at a rate which is one half that of a clock at rest? Homework Equations \Delta T = \gamma \Delta T_0 The Attempt at a Solution For clocks to run at half it's spd, \Delta T = 2 \Delta T_0...
  11. B

    Help Synchronize Clocks: A & B's Perspective

    Please Help...Synchronized Clocks I've posted this before and I just want to clear things up. If A and B are on a train moving at a constant velocity (A in the front and B in the back) and they are asked to set their clocks to 12:00 when the light from a lightbulb in the center reaches them...
  12. C

    Solving Spacetime Homework: Time, Displacement & Clocks

    Homework Statement spaceship 3 meters wide, v= 2c/3. (a.) calculate ships time, (b) sq. root factor, (c) Earth's time, (d) ships displacement, (e) lights displacement, and (f) which clock "runs slow" Homework Equations a. Ts=(3m)/c b. square root 1-v^2/c^2 c. Earth's time = answer a/b...
  13. B

    Synchronized clocks in special relativity

    This is sort of a long post but I have to explain the following situation in order to ask the question so bare with me. Let's say two people, person A and person B, are on opposite ends of a train moving at a constant velocity and another observer is at rest on the platform outside (most of you...
  14. V

    Inner Workings of Relativity Clocks - Learn More Here!

    Hello to all, Could someone give me a link that would point me towards a description of the inner workings of the famous clocks that are part of all discussions and experiments dealing with the relativity of time. What kind of clocks are those ? Thank you, VE
  15. K

    Synchronizing Shed Clocks w/Leading Clock Lag: Explained

    This is rod and shed problem (rod is moving with v towards shed) Length of rod measured when the rod is stationary = L0 Length of shed measured when the shed is stationary l0 = 0.5 L0 Two clocks are fixedd to the front and back of the shed. Explain how these clocks may be synchronised. I...
  16. M

    Evaluating the Elapsed Time Difference Between Clocks in a Gravitational Field

    Clocks show less elapsed time in gravitational field right? So clocks on Earth seem to apply. Consider one clock stationed on the north pole and one somewhere on the equator, both at sea level. It seems there are a couple of factors in order to calculate the difference in time between...
  17. K

    Magnetic Permeability and Electric Permittivity effects on atomic clocks

    Speed of Light c= \frac {1} {\sqrt{\varepsilon_0\mu_0}} Phase Velocity v= \frac {1} {\sqrt{\varepsilon\mu}} Electric Permittivity of Free Space \varepsilon_0 = 10^{7}/4\pi c^2 \quad \mathrm{(in~ A^2\, s^4\, kg^{-1}\, m^{-3}, \, or \, F \, m^{-1})} Magnetic Permeability of Free Space...
  18. P

    24 GPS satellites carry atomic clocks

    Quoted from http://hyperphysics.phy-astr.gsu.edu/hbase/gps.html#c1" How do they know which of the points is the correct one? (see sentence in blod) Thank you!:approve:
  19. D

    What is the scientific definition of time?

    A direct quote from "Science News", April 22, 2006! :wink: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: As I first said, some forty years ago, "someday clocks will be so accurate that the academic community will recognize the fact that they are confusing two very different...
  20. K

    Is the speed of light measurement dependent on local clocks?

    Is the speed of light measurement dependent on the tick rate of different clocks? Hello I want to ask the following questions: If Clock A is undergoing only a natural gravitational time dilation, and possesses 0 rate of change in time dilation, and if it is measuring seconds at a different...
  21. ranger

    Flip Flops and clocks with multisim

    Hey all, I'm trying to build a circuit using flip flops that passes data in series using multisim. My problem is with the clock. I know that data isn't moved until a clock pluse comes along. My problem is that what exactly is the source of this (clock) pulse. Could it be a voltage source and a...
  22. Pengwuino

    Don't forget to turn your clocks back

    It's that time of hear folks :tongue2:
  23. K

    Special Relativity and atomic clocks

    The question is have is as follows: In 1971 four portable atomic clocks were flown around the world in jet aircraft, two east bound and two westbound, to test the times dilation predictions of relativity. a) If the westbound plane flew at an average speed of 1500 km/h relative to the surface...
  24. H

    Atomic clocks / Dynamic clocks?

    I must be confused about the differences between atomic clocks and orbital clocks. Here is what I read on one site. http://www.ldolphin.org/setterfield/redshift.html The faster the velocity of light, the faster an atomic clock beats. I can undertand that. Dynamic clocks run independently, but...
  25. I

    How is the concept of simultaneity affected by relativity?

    I think I asked this a while back but I don't think I worded my question properly... so here it is: Imagine if you're in space traveling at a speed in which the time dilation is 1:4 (ie from Earth's frame of ref, 1 hour pass in spaceship for every 4 hours pass on earth). Suppose that we...
  26. W

    Grandfather Clocks: Why do they Keep Going?

    Why do grandfather clocks keep going? The only way I see htis working is if the chamber has no air (vacuum).
  27. D

    Fast enough clocks to beat the speed of light

    fast enough clocks to beat the "speed of light" fast clocks, how fast? the speed of light is approx 300 000 000 m/s, is there some way to translate that into an effect that can be compared to the "speed" of a clock. and if so, are there any fast enough clocks to beat the "speed of light"...
  28. F

    Revising for Exam: Questions on Pendulum Clocks & Barometers

    this is my second set of questions today, revising for an exam just now. would be grateful to anyone that can answer 1) The pendulum of a clock consists of a thin steel rod carrying a small heavy bob. the clock keeps correct time at 15 degrees centigrade, calculate the error in twenty four...
  29. J

    An illustration of relativity with rulers and clocks

    This is an explanation and illustration of how different reference frames assign coordinates to points in space and time, which I wrote up a while ago on a different forum. I figure it might be interesting to people here, especially in terms of showing how two different observers can both see...
  30. R

    How does the Earth's rotation affect time and weight at different latitudes?

    With a speed of about 460m/s for the Earth's surface at the Equator as it spins around its axis. Using 2 Atomic Clocks tested to be accurate and match each other and both weighing exactly 100 lbs at an arctic lab site pretty much at the north pole. Moving one clock to Ecuador pretty much...
  31. Les Sleeth

    Relativity and Clocks on Airplanes Calibrated from the Ground

    I asked this question in another thread, but wonder about the answer I got: Question: I bought an atomic-timed clock and wondered if while I am taking off from an airport my clock would record time slower than a clock inside the airport. Since time on the clock is actually maintained by a...
  32. W

    Can Life exist if Clocks were not discovered?

    And thus, is it feasible that if the Cosmos has life in other Galaxies, could they evolve without the discovery of Time Measurement Device's, namely clocks? What if the standard measure were just Length and Distance?..could a civilisation comprehend the Cosmos without Clocks?
  33. turbo

    Revolutionary Clocks: Improved Navigation & Trade With Pragmatic Innovation

    That "totally irrelevant" clock may mean little to you, but it and its competitors made global navigation and trade (and projection of military force) a lot safer and more viable. Historically, pragmatic, results-oriented innovations have made investment and risk-taking more attractive, and...
  34. K

    Mass-giving particles slow clocks

    If particles like quarks and electrons get rest mass by interacting with electrically charged particles that fill space,we can imagine them being surrounded by a cloud of such mass-giving particles.Let's postulate that for a force carrier like a photon to exert a force on a quark,for...
  35. D

    So we have problems with clocks measureing time ?

    So we have problems with "clocks measureing time"? Well well, the big guys are beginning to think about the problems in their definition of time [i.e., to quote Gambini et. al.: "a fundamental limit exists on how accurate a clock can be" and "Every physicist notes, upon being introduced to...
  36. Ivan Seeking

    Clocks in town mysteriously changing by 10 minutes

    http://www.saultstar.com/webapp/sitepages/content.asp?contentID=70613&catname=Local+News Just in time, North Shore fast-clock mystery solved http://www.saultstar.com/webapp/sitepages/content.asp?contentID=70740&catname=Local+News
  37. A

    Question about frames of reference and clocks

    Hey everybody, this is my first post! :biggrin: I've always had a problem understanding why, if a space-explorer left on a ship, traveled at nearly the speed of light for a while, and then came back to earth, he might have only aged a few months whereas the people of Earth would have aged...
  38. S

    Photons are clocks and SR says they shouldn't tick

    Suppose the time dilation formula is true: \Delta t = \frac{\Delta t^\prime}{\sqrt{1-v^2/c^2}} if v = c then the denominator is zero. If the denominator is zero and there is division by zero error then the numerator is nonzero. If the denominator is zero and there isn't division by...
  39. S

    Does Time Move Differently on the Space Shuttle?

    I just read that the clocks on board the space shuttle go more slowly than the clocks on earth. does that mean time has speeded up for those on the shutte or slowed down ? i reckon it means time has slowed down. if they stayed up for a year by their clocks then by our clocks more than a year...
  40. M

    A simple explination of why clocks move faster in space

    i am sure that you all know experiments have been done with atomic clocks in outer space and it was found that the atomic clocks that had been in orbit of the Earth were further ahead than the ones on earth, does this mean that you travel slightly faster through time while in orbit of the earth...
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