# What is Clock: Definition and 482 Discussions

CLOCK (Circadian Locomotor Output Cycles Kaput) or Clock is a gene encoding a basic helix-loop-helix-PAS transcription factor that is believed to affect both the persistence and period of circadian rhythms.
Research shows that the CLOCK gene plays a major role as an activator of downstream elements in the pathway critical to the generation of circadian rhythms.

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1. ### I Question about the reciprocity of time dilation

Hello everyone, After studying time dilation I believe we pick a rest frame as a place we situate a clock and because of time dilation when we have a "moving" clock it will have a longer period when compared to the rest clock. I've heard this is reciprocal and if we situate a clock at either...
2. ### B Is velocity the reason for the time dilation effect?

Hello! I try to understand how in different frames clocks tick and stop simultaneously but show different time? I suppose that velocity is reason of time dilation effect but I'm not sure. Thanks.

About two months ago I had a raduim Looping desk alarm clock which fell on the floor from about 3 ft for those last few days i had been using it as an alarm clock and it was working great, but as someone new to clock collectiong I didn't know it was raidoactive. When the clock fell I was...
4. ### Time dilation for a clock thrown vertically

The non-moving clock will see the other one move upwards and land as predicted by Newton's laws, so using the equation ##z=v_0t-\frac{1}{2}gt^2##, and assuming the moving clock starts at ##t=0##, it will land at ##t=\frac{2v_0}{g}##. Now, using SR only, and the Minkowski metric (with signature...
5. ### A Solving "const. K" in Gourgoulhon's SR in General Frames

In sect. 2.3.2 "Ideal Clock", p. 33, of É. Gourgoulhon's text book on "Special Relativity in General Frames" $$\tau_C [ \, \text{tick}_{j}, \text{tick}_{(j + N)} \, ] = K_C \, N.$$ (equation (2.11); notation adapted.) The only other reference to this "constant K" is on the following page...
6. ### Electrical Perpetual Countdown Clock Project

I want to (try to) build a "Countdown to Launch Day" clock for my sailing club. Ideally, it should require no maintenance (meaning, once I'm gone, it will keep working). Even as my right brain was thinking how cool it will be, my left brain started counting the ways it would be problematic...
7. ### PMM or self winding clock?

i am being told trying to make a self winding clock means ppm when this is a self winding clock https://en.wikipedia.org/wiki/Self_Winding_Clock_Company and this is a self winding watch https://en.wikipedia.org/wiki/Automatic_watch i hope someone speaks on my behalf to be allowed to...
8. ### B Need help designing a clock with a repeating signal

Hello! I am in need of a clock expert. Just a disclaimer, I am vastly unfamiliar with much of the inner-workings of clocks and need some help. I have only built a simple Graham Escapement clock, previously. I need to build a clock that triggers a single signal to occur three times at equally...
9. ### Comp Sci Pipelines and Clock Cycles

I think I am having trouble visualizing the count for the clock cycle. Would this just be the clock cycles divided by the instructions of the pipeline? I'm confused about how each stage of the pipeline takes three clock cycles to complete when there are five stages? The consequence of improving...
10. ### B Time: What We Read On The Clock?

This is a basic question, in the sense that it is simple but could be also considered as fundamental. It has been stated on this forum, that time is what we read on the clock. It is mentioned that this was also a statement by Einstein himself (Zeit ist das, was man an der Uhr abliest). This...
11. ### How does the accuracy of the clock change when the spring stretches?

A longer pendulum swings slower. So changing the length l of the pendulum changes the period T, which affects the timekeeping accuracy. But the problem is talking about the body on the spring, not the string. So the second formula cannot be applied here directly and I don't know how to progress...
12. ### B Build a Time Dilation Clock for 8th Grade Science Project

A science teacher ask if I could help one of her students build a "Time Dilation Clock" so, at launch the Ships chronometer and the local time are in sync. with a 3g continuous thrust, at some point the time, the time at the launch site will be going twice as fast as the ships chronometer. so...
13. ### I Comparing Clock Rates in Accelerated vs Constant Velocity Frames

@PeroK sent me here based on a discussion starting at https://www.physicsforums.com/threads/some-ideas-on-interstellar-space-travel.1006562/post-6550265. Summary: Someone claimed that an accelerated observer's clock (observer at 1g from Earth to halfway to Alpha Centauri, then -1g the rest of...
14. ### I Atomic Clock Exp on Ballistic Flight: Proving Clocks are Accelerometers

In the past, scientists have experimented with atomic clocks aboard airplanes in order to prove the Special Theory of Relativity. In our humble opinion, ALL watches are accelerometers. Effect observed in a chaotic pendulum in free fall: Too bad they didn't do the same experiment with an...
15. ### B Clock Ticking in Gravitational Well: Observation Rate

I was wondering what someone standing far away from a planet with mass would see if he drops a clock towards the mass. And then vice versa if I was standing on the planet, what would I see. would I see the clock tick fast and then slow as it approaches? Thanks!
16. ### I What happens to time on the hands of a clock?

I ask this question as a follow-up of an already answered one (about the effect of velocity on time). I'm looking for the effects of SR and GR on a clock's seconds hand. The effect is very tiny though, as you can imagine. Instead of making the size of the clock vary, we can vary c, the speed of...
17. ### B Finding One-Way Speed of Light: Use One Clock

First off, I'm probably totally incorrect on all of this, so feel free to correct me. Second, I'm only 15, so please just be gentle and helpful when I'm totally off. Now for my idea: Have a huge vacuum and put lasers on the inside with hundreds of different lasers at different angles equally...
18. ### Displacement of clock arm

I calculated the angle as 225 whereas answer says something else.
19. ### The 41 second clock failure syndrome

I'm curious about this failure mode. I had a cheap (\$3.82) wall clock from 2017. On Tuesday, it stopped working, getting stuck at the 41 seconds position. The second hand twitches every 1 second, but it does not advance. Since it was so cheap, I threw it away and bought a new one (also...
20. ### I GPS clock synchronization in ECI frame

Hi, starting from this old thread GPS clock synchronization I've a doubt about the physical process employed to synchronize clocks bolted on GPS system satellites. We said that clock synchronization is frame dependent. In other words we must select a coordinate chart (aka reference frame) that...
21. ### Rear Clock Ahead Effect (Special Relativity)

Time when the left beam hits the left wall in the ground frame ##vt_1-x = c t_1## ##t_1 = \frac{x}{c+v}## Time when the right beam hits the right wall in the ground frame ##ct_2 = vt_2 + y## ##t_2 = \frac{y}{c-v}##Setting the times equal to each other with the constraint x+y=L to find x and...
22. ### I Clock synchronization for ring-riding observers on rotating disk

Hello, reading the wiki entry for Langevin observers on rotating disk - Born_coordinates I'm struggling with the following quoted sentence: But as we see from Fig. 1, ideal clocks carried by these ring-riding observers cannot be synchronized. I do not grasp why, starting from the figure...
23. ### B SR equation seems to depend on orientation of the 'light clock'

One of my first exposures to special relativity was looking at a 'light clock' where a photon is emitted and captured by a detector whilst traveling on a train. The passenger sees the photon go straight up. The distance traveled by this photon in a given time, t, is c t An observer however...
24. ### Looking to find the amount of energy stored in a clock spring

I'm looking to find formulas to calculate the energy stored in a spring you would find in a clock. I have been having a hard time finding formulas that govern these types of springs. I have found formula in similar springs, such as the spiral-torsion spring found here but I believe this type...
25. ### Calculating Clock Cycle --

So far I have come to the understanding that a nanosecond is one billionth of a second or 10-9 seconds. So I found this formula to calculate the clock cycle in nanoseconds, for a CPU running at 2.5 GHz. 10^-9 x 2.5 x 10^9 = 2.5 nanoseconds Am I missing any important steps with my calculation...
26. ### Calculate time passed on a ship clock seen by Earth observers

In this case, γ = 1/√(1-v^2/c^2) = √(1-0.6^2) = 0.8 However, I'm not sure if time observed by Earth is proper time or moving time. The definition of proper time in my textbook states that it is 'the time measured in a frame of reference where the events occur at the same points in space. I'm...
27. ### B Why do you need a light clock?

what is wrong with the thought experiment below?! If I consider a light beam going straight towards an observer in motion it makes it look the moving clock ticks faster, but if you use a light clock it makes it look like the clock turns slower. What am I missing here? “Two observers convene in...
28. ### B Light Clock: Why Aren't Delta T and 2D/c Equal?

With this light clock delta t' in S' would be 2 Ls proper time. Since time measurements were done in same location delta x'=0 . Then from stationary S frame delta t = gamma delta t' . With gamma equal to 1.25 then that is 2.5 Ls. However the path the light takes as calculated from S frame in...
29. ### Setting up a pendulum clock

Hello! So we are given this very interesting physics question, that we should only discuss and not do any calculations. So for a) I've though this if the clock is running too fast,the way to adjust this would be to lengthen the pendelum length,my logic behind this the longer the pendelum the...
30. ### Angle between the hands of a clock (IWTSE)

I understand this working all the way up until the '2n-1' part, where n is a positive integer. I understand that delta theta is 90 degrees (i.e. pi/2 radians), as the hands are at right angles to each other.. I also understand where the angle equations are derived from and why you have to find...
31. ### B Moving clock ticking slower

How moving clock ticking slower? Let assume we have mechanical watch which moving at very high speed. To make clock ticking slower ,frequency of balance wheel must be changed.. Why and how frequency of balance wheel will be changed when clock is moving at high speed? I don't see any physical...
32. ### I SR: which clock was slower?

I don't know much about the math of SR, but this is what's bothering me: if a moving clock B ticks slower than the stationary one I have (A), then from the viewpoint of B, my clock (A) is ticking slower. So if we turn around and meet each other in the middle, which clock was slower than which...
33. ### B Light Clock & Length Contraction in GR

Hi, can i use a light clock made out of mirrors a distance appart to measure whether there is length contraction in different regions of spacetime? If the clock speeds up then the distance between the mirrors decreased. If the clock slows down the distance between mirrors increased.
34. ### I Light Clock Animation App: Find, Start & Feedback

I have written a Javascript/HTML5 app that simulates a Light Clock as a way to understand the kinematics of relativity. It shows special and general relativistic effects, and how they are related. I would appreciate any feedback on the app, it's correctness, and it's usefulness as a learning...
35. ### A Atomic Clock theory

I have searched in vain for a detailed calculation of the frequency 9192631770 Hz from basic physical constants using Quantum Mechanics. Can anyone help with this please
36. ### B Falling Clock & Black Hole: Measure Time or Disappear?

Hi, This question is so simple - sorry if the answer is also that simple... It is pretty clear that every matter can cross the event horzion of a black hole. It is said that this process can be even very smooth if the black hole is big enough ("the bigger, the better for you", this is how I...
37. ### B Einstein-Poincare Clock Synchronization Convention

Hi, There are three clocks - Clock A, Clock B, and Clock C. The distance, D, between each clock is 6 light-second. The clocks are situated in a frame of reference which is moving toward the right at speed of 0.5c where 'c' is taken to be 300000000 m/s. Please look here...
38. ### Pendulum clock in a lift

I think the answer will be either (b) or (d). If the pendulum is at its amplitude when the cable breaks, then the oscillation will stop since the pendulum is also not moving at that instant. If the pendulum is at any points except amplitude, then it will hit the ceiling since it still has...
39. ### I Notion of a "clock" in Quantum Mechanics

Suppose the unitary operator ##e^{-\frac{i}{\hbar}\hat{H}t}## acts on ##|\psi (0) \rangle##, does it make sense for one to think of the time-evolved state as some sort of time-keeping device? If not, why? If so, is such a notion useful? Thanks in advance!
40. ### Comp Sci Calculating UART DLL and DLM contents from Baud Rate and Clock Frequency

I understand that, Baud Rate = Clock Frequency / (16 x N) and that N = DLL + DLM when I substitute the figures to get an answer for N to be 576, how do I then convert this into the HEX contents of DLL and DLM, especially considering the maximum value for DLL or DLM is 255? I have uploaded...
41. ### Pendulum Clock -- Change in frequency with change in temperature

1) I do not quite understand how the phrase remain accurate to 1 second in 24 hours? , means ΔP = 1 second, 2) I also don't understand how pendulum period P should be 24 hours What is the reasoning for both? The solution is as such P = 2π √(L/g) P' = 2π √((L+L α δT)/g) ΔP = P'- P = 2π...
42. ### I Shouldn't a moving clock appear to be ticking faster instead of slower?

Hi. Im looking into special relativity and everything i found about time dilation on internet seems to say that moving clock appear to tick slower than the stationary one. However what I found about this is following, in § 4. (Physical Meaning of the Equations Obtained in Respect to Moving Rigid...
43. ### Relativity light clock problem

1. I'm fine with this one, I simply calculated L = L0/γ = 5/1.2 5= 4m. 2. This is the one I'm having problems with. My approach was to say that both observers would measure the light beam to have velocity of ‘c’. Therefore, if 4m is the distance between the mirrors as observed in the frame of...
44. ### How to solve this fast and slow clock problem?

My friend showed me: Each hour clock A runs 5 minutes fast, after 12 hours, clock A is indicating 1 hour later than it should be. Although it is 3, it shows 4. Similarly, because each hour clock B runs 5 minutes slow, after 12 hours, clock B is indicating 1 hour earlier than it should be...
45. ### Freezing Clocks: Accuracy Impact & Reasons

Fairly Simple Question: If a clock, I suppose ideally an atomic clock, is cooled to near a Absolute Zero, does the cooling process have any impact on its ability to keep time accurately? If not, what types of clocks would be impacted by the cooling process? I assume any clock that uses a...
46. ### I Why are atomic clocks so accurate?

For any clock, the way I define accuracy of the clock is based on the Q factor (the ability to reject noise) and the inherent noise in the system. In that case, can you explain me why atomic clocks are so accurate? Do they have high Q factor? (if so, how)? or low noise to begin with?
47. ### I Isotope clock reset debunks earth's age?

<< Mentor Note -- typo fixed below with strikethrough history shown >> I am in a heated debate with a client climate change denier (he created some of the software for their instruments, he says all evidence of how Earth's age is determined is flawed because the Earth's crust is continually...
48. ### Solving an Irregular Clock: No Continuous 576 Minutes

Homework Statement A clock runs irregularly but after 24 hours it has neither gained nor lost overall. Find a way the clock can run irregularly such that there is no continuous 576 minutes during which the clock shows that 576 minutes have passed. Homework Equations 24 hours = 1440 minutes and...
49. ### MHB How far to the nearest hundreth cm, does the tip of the hour hand on a clock move

How far to the nearest hundreth cm, does the tip of the hour hand on a clock move in exactly 3 hours if the hour had is 2.00 cm long? I think you are supposed to use arc length formula. This is what I got so far: s=r(radian symbol) = 3=1(radian symbol)
50. ### Switching clock synchronization off under Debian

I am working on a project* in which I need to fake a pendrive so that it looks like if it was used for several years. That means copying files, making directories, removing them and so on. It needs to be done in such a way that all dates looks OK, which makes it less trivial than it sounds...