Clocks Definition and 244 Threads

For simplicity I assume a flat radial FRW metric (with c=1): ds^2 = -dt^2 + a^2(t)\ dr^2 Now let us consider the path of a light ray, a null geodesic, with ds=0 so that we have: dt = a(t)\ dr Now at the present time t_0 we define a(t_0)=1 so that we have: dt_0 = dr The interval of radial...

Einstein defined truly or absolutely synchronous clocks as follows: "The simultaneity of two definite events with reference to one inertial system involves the simultaneity of these events in reference to all inertial systems. This is what is meant when we say that the time of classical...

I read that stationary clocks on Earth experience time more slowly than clocks on GPS satellites, so the GPS clocks are calibrated to run more slowly to compensate. Since the satellites are in orbit, wouldn't that mean their clocks would be slower since they were moving faster?

Einstein's article "on the electrodynamics of moving bodies", starts with talking about synchronizing clocks at different places and it is through this that Einstein explains concepts like time dilation and length contraction but in the present books about SR you hardly find things about...

Have there been any experiments using atomic clocks underground as a comparison to those on the Earth's surface?

Here for your consideration is a try at synchronizing clocks on a rim rotating at a constant angular velocity. It is restricted to two clocks, each at the opposite end of a diameter of the rim. It is based on simultaneity as determined in SR. Taylor and Wheeler in Spacetime Physics, page...

The "definition" of synchronized clocks This is a purely terminological question. Consider the following setup: we have two inertial observers A and B at rest with respect to one another each equipped with a clock (clock A and clock B respectively), a means of exchanging light signals between...

Consider a perfectly spherical dust shell with a large internal cavity. Imagine there is a moment when the dust is momentarily stationary and there is a string of clocks strung out along a radial axis. At this instant, I will assume that the spacetime inside the cavity is flat and all the clocks...

I just got an Atomic Clock and googled how they work. It says it picks up the Atoms in the Air and sets the Clock from finding out the Energy they emit or something like this. Can you tell me what I am missing or how they work?

Lets say that we have a spaship(with a man) that has speed,and a woman at ground that has not speed. Man throughs a light at ground and light comes again at spaceship. For man light follow a straight line,but for woman follow a V destination. Both see light speed to run with the same constant...

This was just posted today, and looks interesting http://arxiv.org/pdf/1309.1137.pdf A New Generation of Atomic Clocks: Accuracy and Stability at the 10-18 Level B. J. Bloom et al The exquisite control exhibited over quantum states of individual particles has revolutionized the field of...

Excuse me, if i posted on a wrong forum. I heard this quite a time ago, that one day on Earth is not exactly 24 hours. And I'm pretty sure some unit charts on the back of composition books will say one day is 23.9 hours or something like that. My fantasy about how we defined the length of...

Is the expansion of the universe relative to our clocks and rulers? If so, it seems correct to include relativistic effects. And yet I am told that this is wrong. Regards, Jack Martinelli

If a strong gravitational wave hit Earth would clocks record it? as if i understand it it is space time that is oscillating so the time component must be changing.

In his paper, Chou et. al., 2010 has demonstrated that an atomic clock at the height of our head ticks faster than an atomic clock at the height of our feet. I was thinking that one electromagnetic process can be substituted with any other - so that corresponding atoms in our head tick faster...

I am pretty confused in the following situation: Two identical clocks moving at a constant speed v from each other in x-direction. If each clock is made up of a ball moving at a constant speed of 1 on a ruler in y-direction, then the position of the ball of a clock is the time of the clock...

Greetings from Croatia :) It may seem like a 100 times told story but it's not... Let us imagine that we have a rocket with length 50 m when at rest. The rocket goes on a trip and accelerates to the speed near c. Observer from Earth "measure" it's length as 48m (illustrative value),that is...

We have two clocks within a laboratory. We put one on the table and the other in a centrifuge made of glass so we can observe both clocks existence simultaneously. Now observe the clocks throughout the experiment. And now stop centrifuging the clock. Check the time of both clocks. My first...

Im definitely not an expert in this field but i have a question. From what I've picked up time dilation can be observed when a clock has a velocity or moves away from the centre of Earth and it slows/speeds up. In both these cases the clock has more energy, be it potential or kinetic. Could this...

In special relativity clocks are used to record events and proper time gives the time in an inertial frame so two times are used. In general relativity I only see proper time being used. Is there an implicit understanding about clocks?

My question is as follows: A photon clock (two 100% reflective mirrors exactly parallel and photons whizzing in between) actually possible. My question is made assuming we could get the mirrors exactly parallel. So really, I suppose my question is: Are 100% reflective mirrors possible to make...

Homework Statement What is the velocity of the plane where clocks in two different frames are synchronized? Homework Equations Lorentz Transformations: t' = γ(t - vx/(c^2)) x' = γ(x - vt) Solution should be v(t = t') = (c^2)/v * (1 - 1/γ) The Attempt at a Solution I am getting the...

Einstein, 1905: From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the...

I had such success with all your answers to my last SRT question here I’ll try another. The LT seems very symmetric. To the observers in each frame, the other’s clocks appear slower, etc. Is that true for out GPS satellites? If we ignore the GRT effect of speeding up their clocks, I think it is...

Homework Statement Two atomic clocks are synchronized. One is placed on a satellite which orbits around the Earth at high speeds for a whole year. The other is placed in a lab and remains at rest with respect to the earth. You may assume both clocks can measure time accurately to many...

I have often thought about how the one-way speed of light can be measured without having to use synchronized clocks, which tends to be controversial because the clocks are normally synchronized by using one-way light in the first place. Recently, Don Lincoln of Fermi-Lab suggested a method to...

Homework Statement Homework Equations My question too :) The Attempt at a Solution Can anybody confirm whether I solved the problem right or wrong? As for the next question about verilog and many clocks I am unable to find a source with that information. Thanks a lot for any...

Hello I've got two flip-flops, F1 and F2. And a clock C1. Every time the C1 goes High, it should drive F1 high and F2 low. There's a slower clock, C2. When C2 goes High, it should drive F2 high and F1 low. If C1 and C2 go high at the same time, C2 wins. How to do this? Thank You.

As the title says, imagine two observers with clocks A and B in space which move at vrel relative to each other. Just when clock A passes by clock B, the clocks counter shows zero. Observer A will conclude clock B to tick slower, while observer B will conclude clock A to move slower (both using...

Homework Statement A person "A" with a watch is standing on a train station. A train (which proper length is 100ms*c) passes him with a speed of 3/5c. A person "B" sitting on the front of the train synchronizes his watch with the "A" (both set to 0) when he passes him. At the same time he...

Hello. How big is day – night speed variations for stationary atomic clock placed somewhere on equator? And what experiment can measure such variations?

Hello here is small question: Lets say we have 2 clocks on spacecraft . Both are synchronized with Earth clock before start. Lets synchronize one of them with Earth clock again when they arrive to an orbit. Do relativity predict some faze diference for these two clocks now? If so how...

I understand time dilation exists according to relativity theory. But what I'm not able to understand is this statement, "clock is ticking faster/slower on a moving object compared to observer". How is that possible to measure it? or how does the clock (atomic/quartz) it experience the time...

So clocks _on_ Earth are slower than the clocks in satellites because Earth is massive? it doesn't make sense to me, what does the mass of an object have to do with the passage of time of other objects surrounding this massive object or that lie on it? I can't think of any reasonable...

Hello, The three clocks A, B and C is at rest in S frame. The clocks unsimultaneously change its frame from S to S'. The frame change events is simultaneous in S' frame. Now, clocks is moving in S frame and at rest in S' frame. I am struggling with this. The events on A clock displayed by...

Hi. If two light clocks are put on a rocket at rest and then accelerated to relativistic velocities with one of the light clocks parallel to the direction of motion and one perpendicular, will one clock continue to measure the rate of change of time in the rest plane while the other one...

Clocks and time are not the same thing. Time is a property of nature observable as changes. Day turns to night, summer follows winter, and rivers flow downstream. Clocks, however, are man made objects that do what we tell them to do. For everyday use we regulate clocks to match the noon-to-noon...

Hello, Suppose, A and B is clocks at both end of train. A is at left and B is at right. Observer O is at middle of train at point M. Observer R is on platform. Train is at rest and O synchronize both clock. The clock is synchronized with respect to both observer. Now, train starts moving to...

The ship leaves the station carrying two mirror clocks. One aligned with the motion. The other, orthogonal to the first. One suffers length contraction but the other does not. I suppose time dilation acts on both. So we have a contradiction here. What is happenning in fact?

Hey guys, I've been trying to find out about the expected effect of acceleration and/or motion on a pendulum clock; I asked this question in the mechancial engineering section of PF but didn't get any replies. It pertains to Einsteinian relativity also, specifically the effect of motion on...

I hope this is the right place for this kind of question - please forgive me if it isn't. I am wondering about the expected effect of acceleration and/or motion on a pendulum clock. It pertains somewhat to relativity theory, but [to my understanding] it is equally a mechanical engineering...

I am curious about time dilation of atomic clock positions on and in the Earth. If you had a long tube going through the Earth with one atomic clock on the surface of the Earth and one in the center of the Earth which would experience more proper time?

The depiction of time dilation that is typically used to describe the situation, shows the stationary photon clock, with mirrors one above the other in the observer's frame and the photon "bounces" back and forth between them. In the moving frame the mirror pair moves as a unit let's say to...

Let say we would like to perform such experiment: Let we have 2 small/mobile atomic clocks on a hard rod. (AC1)==============================================(AC2) Distance between clocks about 2 meters. There is no any electrical wire connections between these two clocks for...

I was wondering about two types of clocks that I see often. One is continuous in manner and the other ticks from one second to the next. Which clock properly represents time? Personally, I think time should be represented as a flow and not in unitary fashion. What do you think?

Firstly, hello. This is my first post at Physics Forums, and I want to thank everyone in advance for contributing their thoughts and expertise here. I'd like some help with the following thought experiment. My apologies if I'm posing too basic a problem, but I haven't been able to find...

moving closer to light speed relative to another clock tick slower? I understand that the waves take longer to reach the stationary observer on the turn around, but that's just appearance. It still seems the clocks would be in sync upon the return. What is making time actually slow down...

Is the accuracy of atomic clocks in any way dependent on the speed of light? For example, if the speed of light were to speed up slightly, would that somehow speed up the frequency of oscillations of caesium used in an atomic clock? ...or would those 9 billion (or so) oscillations occur at...

The example our lecturer uses to illustrate the relativity of simultaneity is a light clock, where a photon is bounced between a reflector and a detector. a tick in the clock means the light has made a round trip in the clock. There are two clocks, one is orientated perpendicular to the...

I have just started reading Landau and Ligarbagez' fantastic work Classical Theory of Fields. It has got me thinking about some simple scenarios involving moving clocks... Moving clocks run slower - but which clock is moving? A spaceship passes the Earth say at a constant velocity, the...