Does a cesium clock on top of a mountain tick slower then a clock on sealevel due to gravity?.....

Does the same hold true for optical clocks?

the clock... at a higher attitude... will tick slower... barely.

but not due to gravity...

due to the difference in velocities.. at sealevel and at a height.

the higher object... moves in a bigger circle..

i.e.. travels more distance per spin of the earth.. thus it is moving faster.

but im not sure... if it would be enough to measure.

i hear that astronauts... only lose like 1/10,000 of a sec.. or some small number when in orbit FOR A FEW DAYS.

the exact number... i forget.... but it is small.

-MT

I don't think velocity has anything to do with it. Acceleration maybe, but velocity - I don't think so.

But anyway, injus5, you have it backward. A clock will run faster on top of the mountain. A very very miniscule amount, though. Yes, it's the same for all clocks.

RUBIKSMASTER.... HAS IT WRONG.

it is velocity..... NOT ACCELORATION.

and it runs slower.

and only an atomic clock could notice the difference.

-MT

Mosheh Thezion RUBIKSMASTER.... HAS IT WRONG.

it is velocity..... NOT ACCELORATION.

and it runs slower.

and only an atomic clock could notice the difference.

-MT
No, MT, an atomic clock on a mountaintop does not run slower. The frequency of the transitions of the cesium-133 atom increase when locating the clock higher in the gravitational potential. If left uncorrected, it could be said the clock on the mountaintop runs faster than a clock at sealevel. The key term is 'uncorrected'. What time scale are you referring to? 'Time' is a man-made construct and the are several timescales used in current science. The most common is TAI (atomic time), which is uncorrected by leapseconds such as UTC time. GPS time is very similiar to TAI time as it is also uncorrected by leapseconds at the system level. Leapseconds are broadcast by the GPS satellites so users on Earth's geoid can coordinate their time to UTC time, the standard time used by the civilian world. You ask me what is the point of this discussion? Surprising to almost all laymen and even to most physicists, the clock at the top of the mountain officially keeps identical time with a clock at sealevel, and also identical time with clocks located on satellites. The SI definition of a second is the duration of 9192631770 cycles of transition between the hyperfine levels of the ground state of Cesium-133. That is the 'proper time' of any local frame of reference, all TAI, GPS, and UTC clocks are 'adjusted' to beat at this specific rate defining an SI second. All 'official' clocks are synchronized. As I said, time is a man-made concept. Velocity, gravitational potential and enviromental factors are adjusted out of official Atomic time. For example, the pulsation rate of a distant millisecond pulsar will measured as identical in all frames of reference by an clock synchronized to this official time.

time flow.... is velocity dependant.

faster objects... (relatively) experience less relative time flow.

hence the clocks that were in sinc.... become out of sinc.

would you argue with this?

and what would be your arguement?

-MT

I was under the impression that gravity did effect time...due to the whole thing if u were in an elevator in space you wouldnt be able to tell the difference if u were accelerating or if you were just in a uniform gravitational feild but i could be wrong

MT, I'll give a link to a paper that explains what I was stating in more detail. You will have to read the paper carefully, it is not easly understood if you are used to thinking of time as a single 'thing'. When viewing an atomic clock from a remote location, the clock can 'seem' to run slower or faster due to a change in the frequency of the signals recieved. The change in frequency can be due to relative velocity or gravitational potential. It can also be due to other enviromental factors, such as the relative difference in magnetic field strength and relative temperatures. Even the velocity of the cesium atom being sampled relative to the rest of the clock enclosure can affect the transition cycle (the 'tick' rate).
So, what is true time? Depends on your purpose and how you wish to scale time. Scaling time as relative time is necessary for relativity theory to work. Absolute time is what we actually use in our everyday lives (UTC) and most science dealing with telemetry and astronomy. An excerpt from the paper:
When people asked us what kind of seconds we were using in defining Toolkit time, we just said SI (international system) seconds, and, if necessary, we referred them to handbooks such as the Astronomical Almanac. But, dealing with all these time streams, one gets "curioser and curioser" about what the SI (International System) second really is. It is defined on the geoid (essentially a sea-level surface on Earth) as the duration of 9192631770 cycles of transition between the hyperfine levels of the ground state of Cesium 133, when the atom is undisturbed. But what about off the geoid? Einstein's Principle of Equivalence says that a well made clock has to be trusted as a laboratory standard at all different velocities and gravitational potentials. That way, the laws of physics and the fundamental constants of Nature don't depend on where you are or how fast you are moving. As a consequence of relativity, "proper" clocks such as these in relative motion or at different gravitational potentials won't stay synchronized. But synchronized time standards are needed for civil timekeeping, space geodesy, Very Long Baseline Interferometry (VLBI) and other needs. Thus, various bodies in charge of time standards and many experts on clocks have put the most effort into perfecting the determination of time streams such as TAI that are broadcast, and are used to synchronize clocks worldwide, irrespective of their elevations or states of motion. As a physicist rather attached to the Principle of Equivalence, without which laboratory physics would collapse (because physics would be different in virtually each laboratory), I became concerned about the prevalence of statements suggesting that the SI second is reserved for TAI and that clocks off the geoid must be slaved to it. On making further inquiries, it turns out that the International Astronomical Union has affirmed in Resolution A4 that the SI second is, in the first instance, a unit of proper time. That means that it is the unit measured by a "proper clock." The problem that remains to be addressed is that the SI second is based on the "undisturbed" state of the atom, which is understood by some professionals in the field of time standards to mean that you "correct for" the gravitational potential. If you do that and take the resulting second as your laboratory SI second, you define a different physics in violation of the Equivalence Principle. A commission named the "Comite Consultatif pour la Definition de la Seconde," affiliated with the Bureau International des Poids et Mesures - in Sevres, France (BIPM) is preparing a report on the application of general relativity to metrology which we hope will resolve this issue in favor of not correcting proper clocks for the gravitational potential.

To summarize the correct procedure: if you're off the geoid, you can't measure SI seconds as such by counting the ticks of a remote TAI clock (which is on the geoid or controlled as if it were) by telemetry; instead you calibrate to its rate times (1+gh/c2) as shown in Fig. 3-2. For illustration, that figure shows two out of many "official" clocks on or very near the geoid, which are assumed to have been synchronized by telemetry using some kinds of weights reflecting their performance. They are a model for the definition of TAI. An ideal clock on a mountain top like Clock 2 will seem to run fast when compared by telemetry. This is an effect of spacetime curvature; nothing at all is wrong with the clock. One in a deep valley, like Clock 1, will seem to run slow. If you want to do radio interferometry on a distant quasar using these clocks, or to use them for civil timekeeping, you have to slave them to the TAI network. If you want to do local laboratory physics, you should instead calibrate them against TAI with the correction factor shown in the caption. It is easy to go astray in this work for two reasons. One is that in practice, there are several other corrections that have to be made to correct the atomic frequency for various effects, including, of all things, the individual atom's velocity relative to the clock!
http://72.14.209.104/search?hl=en&q=cache:jmuEemDeLJAJ:http://observer.gsfc.nasa.gov/sec2/papers/noerdlinger2.html

<P>You will have to set this to accept html to read this right. This isn't a trivial question as you can see from the varied responses. There is both a velocity dependant term and a gravitational term in the dilation formula which both have to be considered. Lets say the spacetime is approximately Schwarzschild and look at a clock from far away. Our watch time will be t and its time will be <FONT FACE="Symbol">t</FONT>. From the invariant interval, line element, or metric we have</P>
<P>ds<SUP>2</SUP> = (1 - 2GM/rc<SUP>2</SUP>)dct<SUP>2</SUP> - dr<SUP>2</SUP>/(1 - 2GM/rc<SUP>2</SUP>) - r<SUP>2</SUP>d<FONT FACE="Symbol">W</FONT><SUP>2</P>
</SUP><P>dr = 0</P>
<P>ds = dc<FONT FACE="Symbol">t</P>
</FONT><P>dc<FONT FACE="Symbol">t</FONT><SUP>2</SUP> = (1 - 2GM/rc<SUP>2</SUP>)dct<SUP>2</SUP> - r<SUP>2</SUP>d<FONT FACE="Symbol">W</FONT><SUP>2</P>
</SUP><P>dc<FONT FACE="Symbol">t</FONT><SUP>2</SUP>/dct<SUP>2</SUP> = 1 - 2GM/rc<SUP>2</SUP> - r<SUP>2</SUP>d<FONT FACE="Symbol">W</FONT><SUP>2</SUP>/dct<SUP>2</P>
</SUP><P>(d<FONT FACE="Symbol">t</FONT>/dt)<SUP>2</SUP> = 1 - 2GM/rc<SUP>2</SUP> - v<SUP>2</SUP>/c<SUP>2</P>
</SUP><P>(dt/d<FONT FACE="Symbol">t</FONT>)<SUP>2</SUP> = 1/(1 - 2GM/rc<SUP>2</SUP> - v<SUP>2</SUP>/c<SUP>2</SUP>)</P>
<P>dt/d<FONT FACE="Symbol">t</FONT> = 1/(1 - 2GM/rc<SUP>2</SUP> - v<SUP>2</SUP>/c<SUP>2</SUP>)<SUP>1/2</P>
</SUP><P>So you see in general relativity there are two terms in the time dilation factor for this problem. One is gravitational and the other is velocity dependent. Lets say that the clock is a height h above the radius of the earth R, and </P>
<P>h &lt;&lt; R and v&lt;&lt; c </P>
<P>then we can approximate this by</P>
<P>dt/d<FONT FACE="Symbol">t</FONT> <FONT FACE="Symbol">»</FONT> 1 + (GM/Rc<SUP>2</SUP>)(1 - h/R) + (1/2)(<FONT FACE="Symbol">w</FONT>R/c)<SUP>2</SUP>(1 + 2h/R)</P>
<P>Check my arithmetic but I get for the earth</P>
<P>GM/Rc<SUP>2</SUP> = 4.4x10<SUP>-3</P>
</SUP><P>(1/2)(<FONT FACE="Symbol">w</FONT>R/c)<SUP>2</SUP> = 1.2x10<SUP>-12</P>
</SUP><P>So</P>
<P>dt/d<FONT FACE="Symbol">t</FONT> <FONT FACE="Symbol">»</FONT> 1 + 4.4x10<SUP>-3</SUP>(1 - h/R) + 1.2x10<SUP>-12</SUP>(1 + 2h/R)</P>
<P>The last term is so extremely small compared to the others we can ignore it leaving us with only</P>
<P>dt/d<FONT FACE="Symbol">t</FONT> <FONT FACE="Symbol">»</FONT> 1 + (GM/Rc<SUP>2</SUP>)(1 - h/R)</P>
<P>This no longer contains the velocity dependent term as it was to small to consider compared to the gravitational term. So the final answer is that the lower clock runs slower due to gravitation than the one at the top of the mountain.</P>
<P>This experiment was performed only using a tower and sure enough the gravitational time dilation matched general relativity's prediction here.</P>

Trilairian,
This experiment was performed only using a tower and sure enough the gravitational time dilation matched general relativity's prediction here.
Are you referring to the Pound-Rebka experiment at the Harvard tower? If so, no clocks were used and no 'time dilation' was recorded. What the experiment did was to compare the energy shifts (frequency shifts) of gamma-ray photons in upward paths vs. downward paths. The photons gained energy as they fell in a gravitational field and lost energy as they climbed upward out of a gravitational field.

clock at top of mountain is affected by both gravity and velocity. both GR and SR are applied to calculate the offset. due to less gravity it runs faster, due to higher velocity(higher orbit, same angular speed) it runs slower. sum result is i think they run a bit faster.

I've sometimes thought about this...
If time runs faster at the top of a mountain than the bottom then the person at the top will eventually be first a day, then a week, then a year ahead of the person at the bottom. So the person at the top would count more sunrises and sunsets. But how can that be if they are both at the same place on the Earth? But, if only the clock is running faster and all other events are not keeping in synch with the clock, then there is no difference between that clock and a clock that is merely defective and running too fast.

fascinating.... i am always glad to be wrong, if it changes things.

-MT

I've sometimes thought about this...
If time runs faster at the top of a mountain than the bottom then the person at the top will eventually be first a day, then a week, then a year ahead of the person at the bottom. So the person at the top would count more sunrises and sunsets. But how can that be if they are both at the same place on the Earth? But, if only the clock is running faster and all other events are not keeping in synch with the clock, then there is no difference between that clock and a clock that is merely defective and running too fast.

not really, the clock is not defective. it is - if you insist that earth revolutions are the proper way of keeping time, but that decision is purely arbirtary.
fact is, electromagnetic interaction of the fundamental energies/particles etc. simply "run" at a faster rate at the top of the mountain - this is how time is faster. the end result is, you will AGE at the rate of the uncorrected atomic clock in pure physical sense - you will AGE faster and you will not notice it.
if you keep time by looking at the earth revolutions, it will always be the same no matter where you are, heh, earth will always revolve at the same speed.

Are you referring to the Pound-Rebka experiment at the Harvard tower? If so, no clocks were used and no 'time dilation' was recorded. What the experiment did was to compare the energy shifts (frequency shifts) of gamma-ray photons in upward paths vs. downward paths. The photons gained energy as they fell in a gravitational field and lost energy as they climbed upward out of a gravitational field.
You say no and then contradict yourself. Funny. You need to think about what causes stationary observers at different locations who all locally measure the speed of a wave to be the same speed c to measure different frequencies from an also stationary source. There is only one possible answer.

Does a cesium clock on top of a mountain tick slower then a clock on sealevel due to gravity?.....

Does the same hold true for optical clocks?

according to Einstein, stronger gravity slows time, as it is seen near blackholes

Triliarian,
You say no and then contradict yourself. Funny.
What do you find funny, Trilairian? Suppose you show the 'contradiction' you claimed I made. I stated no clocks were used and no 'time dilation' was measured, that the experiment measured energy shifts of gamma photons as the moved in a gravitational field. You stated the gravitational time dilation matched General Relativity's predictions. To measure a difference in clock tick rates, two synchronized clocks must be compared after a specified period of 'time' has passed after they were synchronized. Do you claim a reference hydrogen maser clock located at Schriever Air Force Base, with an elevation of near 1900 meters, records time at a faster rate than an identical hydrogen maser clock located at sealevel or at Paris, France?

Triliarian,
There is only one possible answer.
Really? So 'time' runs at different rates in different temperatures also? The transition frequencies of Cesium-133 atoms vary with temperature.

Triliarian,

What do you find funny, Trilairian? Suppose you show the 'contradiction' you claimed I made. I stated no clocks were used and no 'time dilation' was measured, that the experiment measured energy shifts of gamma photons as the moved in a gravitational field. You stated the gravitational time dilation matched General Relativity's predictions. To measure a difference in clock tick rates, two synchronized clocks must be compared after a specified period of 'time' has passed after they were synchronized. Do you claim a reference hydrogen maser clock located at Schriever Air Force Base, with an elevation of near 1900 meters, records time at a faster rate than an identical hydrogen maser clock located at sealevel or at Paris, France?

Triliarian,
There is only one possible answer.
Really? So 'time' runs at different rates in different temperatures also? The transition frequencies of Cesium-133 atoms vary with temperature.
I did tell you the contradiction. You just didn't get it. I told you that you would have to think about it and you didn't. Thats your loss. And your temperature statements are completely irrelevent and therefor rediculous.

Trilairian,
I did tell you the contradiction. You just didn't get it.
No, you told me what you thought was a contradiction. I understand your naive view perfectly. You fail to understand the difference between relative time as used in relativity theory and official UTC time as used in the rest of science and the world. You state a change in the energy level of a gamma photon is proof of 'time dilation' instead of just a gravitational redshift. You state 'time' runs at a faster rate on a mountaintop than it does at sealevel. I state that this assumed 'time dilation' is an extrapolation of relativity theory drawn from observations of gravitational redshifts. A cesium clock on a GPS satellite, one at high elevation located at Schriever AFB, or one located at sealevel, are all synchronized to beat at the same rate by official ATI (universal atomic) time.

Now suppose you support your theoretical arguments with experimental facts. I hate to keep repeating myself, but an SI second is the duration of 9,192,631,770 cycles of transition between the hyperfine levels of the ground state of cesium-133. The cesium atoms are excited by a microwave beam and emit light (known as fluorescence, of course)as they fall back the the ground state. The maximum fluorescence is at the frequency stated above. Now you tell me what you think happens with the clock on the mountain. Do you think these 9,192,631,770 cycles will occur in a relatively shorter duration of time for the clock on a mountain? In that case, the clock at Schriever AFB would beat faster than a clock at sealevel, wouldn't it? But that doesn't happen in reality, the world's official clocks at Schriever and Paris, for example, both beat at the same rate and stay synchronized. Both use the same number of cycles to define the duration of a second. So what do you propose as the mechanism for your time dilation in these real clocks?

Trilairian,

No, you told me what you thought was a contradiction. I understand your naive view perfectly. You fail to understand the difference between relative time as used in relativity theory and official UTC time as used in the rest of science and the world. You state a change in the energy level of a gamma photon is proof of 'time dilation' instead of just a gravitational redshift. You state 'time' runs at a faster rate on a mountaintop than it does at sealevel. I state that this assumed 'time dilation' is an extrapolation of relativity theory drawn from observations of gravitational redshifts. A cesium clock on a GPS satellite, one at high elevation located at Schriever AFB, or one located at sealevel, are all synchronized to beat at the same rate by official ATI (universal atomic) time.

Now suppose you support your theoretical arguments with experimental facts. I hate to keep repeating myself, but an SI second is the duration of 9,192,631,770 cycles of transition between the hyperfine levels of the ground state of cesium-133. The cesium atoms are excited by a microwave beam and emit light (known as fluorescence, of course)as they fall back the the ground state. The maximum fluorescence is at the frequency stated above. Now you tell me what you think happens with the clock on the mountain. Do you think these 9,192,631,770 cycles will occur in a relatively shorter duration of time for the clock on a mountain? In that case, the clock at Schriever AFB would beat faster than a clock at sealevel, wouldn't it? But that doesn't happen in reality, the world's official clocks at Schriever and Paris, for example, both beat at the same rate and stay synchronized. Both use the same number of cycles to define the duration of a second. So what do you propose as the mechanism for your time dilation in these real clocks?

No you don't understand what I wrote, the math was over your head and I proved you wrong with it already.

Trilairian,

No, you told me what you thought was a contradiction. I understand your naive view perfectly. You fail to understand the difference between relative time as used in relativity theory and official UTC time as used in the rest of science and the world. You state a change in the energy level of a gamma photon is proof of 'time dilation' instead of just a gravitational redshift. You state 'time' runs at a faster rate on a mountaintop than it does at sealevel. I state that this assumed 'time dilation' is an extrapolation of relativity theory drawn from observations of gravitational redshifts. A cesium clock on a GPS satellite, one at high elevation located at Schriever AFB, or one located at sealevel, are all synchronized to beat at the same rate by official ATI (universal atomic) time.

Now suppose you support your theoretical arguments with experimental facts. I hate to keep repeating myself, but an SI second is the duration of 9,192,631,770 cycles of transition between the hyperfine levels of the ground state of cesium-133. The cesium atoms are excited by a microwave beam and emit light (known as fluorescence, of course)as they fall back the the ground state. The maximum fluorescence is at the frequency stated above. Now you tell me what you think happens with the clock on the mountain. Do you think these 9,192,631,770 cycles will occur in a relatively shorter duration of time for the clock on a mountain? In that case, the clock at Schriever AFB would beat faster than a clock at sealevel, wouldn't it? But that doesn't happen in reality, the world's official clocks at Schriever and Paris, for example, both beat at the same rate and stay synchronized. Both use the same number of cycles to define the duration of a second. So what do you propose as the mechanism for your time dilation in these real clocks?


GPS atomic clocks ARE INFACT tuned to count more cycles for a single second than standard sea level atomic clocks. This actually keeps GPS clocks in sync with sea level clocks, otherwise they would run faster for like 38 microseconds a day.
This is a fact. They are pretuned before sattelite launch using GR and SR to predict time dilation.
If they were 38 microseconds wrong the whole system would develop a noticable error margin within days and would be rendered useless.

Time has compressed for the GPS clocks, but we have no use for them to keep their "orbit frame of reference time", we need them to keep our sea level time which is why the GPS clocks are modified to count more cycles per second than sea level clocks.

vx220,
GPS atomic clocks ARE INFACT tuned to count more cycles for a single second than standard sea level atomic clocks. This actually keeps GPS clocks in sync with sea level clocks, otherwise they would run faster for like 38 microseconds a day.
This is a fact. They are pretuned before sattelite launch using GR and SR to predict time dilation.
You made a couple of mistakes, vx220, but you still did better than some. First, I never stated that GPS clocks were not corrected to keep synchronized time with Earth surface clocks. In fact, I stated they were synchronized to keep time with standard TAI time. Second, regardless of what you have been led to believe, the transition frequency is not 'adjusted', the main part of the clocks beat at their natural frequency. Yes, this frequency IS relatively faster than a clock at sealevel. The output frequency is what is adjusted, it is adjusted after the clock is turned on in orbit and allowed to stabilize. Now, did you read the link I provided above? If you did, you failed to understand the difference between relative time and ATI/UTC time. The frequency of the atomic transitions in orbit will be naturally faster than the atomic transitions at sealevel. You can call that 'relative time' if you wish. After the satellite clock is corrected to synchronize with a sealevel clock, THAT is ATI/UTC time. It is the time standard we use to keep all of our clocks on Earth synchronized, whether those clocks are located on a mountaintop or at sealevel. It is the time standard we use to keep 'noon' from eventually taking place after dark because of clocks that do not synchronize with universal time and the Earth's rotation. Consider a distant pulsar that is measured to rotate at 1000 times per second by a clock located at the Bureau of International Weights and Standards in Paris with an elevation of appox. 110 meters. A clock located at Schriever AFB, at an elevation of 1900 meters, will also measure the rotation rate of the pulsar as 1000 times per second. That is ATI/UTC time, the time standard we use in science. Relative time would have clocks all over the world beating at different rates, accumilating 'time' at different rates according to their elevation. Telescopes located at different elevations could not use a common ephemeris to point at distant stars. Absolute chaos would ensue. No, we use a time standard that advances at the same synchronized rate, keeps time with the universe, regardless of the individual clock's frequency shifts due to elevation, speed, or enviromental factors. Relative time is only needed to make relativity theory work, as I stated before.

Does a cesium clock on top of a mountain tick slower then a clock on sealevel due to gravity?.....

Does the same hold true for optical clocks?

No - you got it wrong , the clock on the top of a mountain runs FASTER than the clock at sealevel , due to gravitational time dilation !!!!!!!!

;)

http://khouse.org/articles/1999/245/print

http://en.wikipedia.org/wiki/Gravitational_time_dilation

Relative time would have clocks all over the world beating at different rates, accumilating 'time' at different rates according to their elevation. Telescopes located at different elevations could not use a common ephemeris to point at distant stars. Absolute chaos would ensue.
Come off it, 2inq. Clocks do beat at different rates, even if they're located in the same room. This isn't because of relativity - it's because of engineering limitations. It's not possible to construct two clocks to beat at exactly the same rate - there is always some error.

I'm pretty sure that the predicted differences in rates due to relativity between clocks on Earth's surface is too small to be separated out from these engineering imprecisions.

vx220,

You made a couple of mistakes, vx220, but you still did better than some. First, I never stated that GPS clocks were not corrected to keep synchronized time with Earth surface clocks. In fact, I stated they were synchronized to keep time with standard TAI time. Second, regardless of what you have been led to believe, the transition frequency is not 'adjusted', the main part of the clocks beat at their natural frequency. Yes, this frequency IS relatively faster than a clock at sealevel. The output frequency is what is adjusted, it is adjusted after the clock is turned on in orbit and allowed to stabilize. Now, did you read the link I provided above? If you did, you failed to understand the difference between relative time and ATI/UTC time. The frequency of the atomic transitions in orbit will be naturally faster than the atomic transitions at sealevel. You can call that 'relative time' if you wish. After the satellite clock is corrected to synchronize with a sealevel clock, THAT is ATI/UTC time. It is the time standard we use to keep all of our clocks on Earth synchronized, whether those clocks are located on a mountaintop or at sealevel. It is the time standard we use to keep 'noon' from eventually taking place after dark because of clocks that do not synchronize with universal time and the Earth's rotation. Consider a distant pulsar that is measured to rotate at 1000 times per second by a clock located at the Bureau of International Weights and Standards in Paris with an elevation of appox. 110 meters. A clock located at Schriever AFB, at an elevation of 1900 meters, will also measure the rotation rate of the pulsar as 1000 times per second. That is ATI/UTC time, the time standard we use in science. Relative time would have clocks all over the world beating at different rates, accumilating 'time' at different rates according to their elevation. Telescopes located at different elevations could not use a common ephemeris to point at distant stars. Absolute chaos would ensue. No, we use a time standard that advances at the same synchronized rate, keeps time with the universe, regardless of the individual clock's frequency shifts due to elevation, speed, or enviromental factors. Relative time is only needed to make relativity theory work, as I stated before.

so, whats your point?

fact is that GR and SR predicted the exact cesium transitions frequency shift for geostatic orbits.

if time was 2x(it is just a small amount faster, just like GPS satts, but what if...) faster on space spation MIR, im sure they'd sync their clocks to tick together with sea-level clocks and keep sea-level UTC time.

but! a person aboard MIR would manage to do 20 pushups within this UTC synced minute compared to a person at sea level who'd be able to do 10 pushups within that same UTC minute.
the person on the space station would measure 10 pulsar pulses during 20 pushups during 1 minute of UTC synced time on his clock. the person on sea level would measure also 10 pulsar pulses during 10 pushups during 1 minute of UTC synced time on his clock.

so do you see the point? naturally they both measure the same frequency of the pulsar as they tuned both their clocks to UTC. but one can do more pushups - more local action - per one pulsar pulse or UTC tick.

if the clocks were synced to UTC before space station launch and not resynced when reaching orbit, they would both do 10 pushups per minute but the spacestation would measure different pulsar frequency.. also it would be out of sync with sea-level time - earth time where everything happens.

so it is obvious syncing with UTC is more practical for most applications..

2inquisitive (and others are basically) correct.

From the point of view of an observer on the surface of the earth (to be definite, let's say the equator) a clock on a GPS satellite appears to be running both faster (General Relativity - gravitational gradient) and slower (Special Relativity - orbital velocity).

The results are about:
+45 microseconds / day (GR)
- 7 microsecond / day (SR)

The net is:
+38 microseconds / day.

This doesn't sound much, but the GPS system needs nanosecond precision. So relativity (both kinds) has a huge practical effect on the GPS system - probably kilometers per day of potential locational error if it weren't considered.

2inquisitive (and others) are basically correct.

From the point of view of an observer on the surface of the earth (to be definite, let's say the equator) a clock on a GPS satellite appears to be running both faster (General Relativity - gravitational gradient) and slower (Special Relativity - orbital velocity).

The results are about:
+45 microseconds / day (GR)
- 7 microsecond / day (SR)

The net is:
+38 microseconds / day.

This doesn't sound much, but the GPS system needs nanosecond precision. So relativity (both kinds) has a huge practical effect on the GPS system - probably kilometers per day of potential locational error if it weren't considered.

Pete,
Come off it, 2inq. Clocks do beat at different rates, even if they're located in the same room. This isn't because of relativity - it's because of engineering limitations. It's not possible to construct two clocks to beat at exactly the same rate - there is always some error.
You are speaking of clocks, not time. The difference in the two is what I am trying to illustrate. Yes, all clocks keep time, but how do you define time?
I'm pretty sure that the predicted differences in rates due to relativity between clocks on Earth's surface is too small to be separated out from these engineering imprecisions.
Coordinated Universal Time (UTC) is kept by the International Earth Rotation And Reference System Service. It is comprised of a worldwide network of 200 precise clocks. This ensemble of clocks is accurate to a tenth of a billionth of a second per day. The 38 microsecond/day error of a GPS clock would be a HUGE error if it were not corrected to keep coordinated time with UTC time. Clocks on mountains also have to be corrected to keep UTC time. If the montaintop clocks were not corrected, they would not keep official universal time. Precise, synchronized time is required to keep power grids from failing and even the internet working properly. Clocks at high elevations are steered to synchronize with UTC time to keep correct time. Conclusion, time runs at the same rate on a mountaintop and the faster-beating atomic clock has to be corrected to keep proper time. ;)

so does this mean i age faster on a mountaintop than at sea level, hehe?

so does this mean i age faster on a mountaintop than at sea level, hehe?Yes

vx220,
if time was 2x(it is just a small amount faster, just like GPS satts, but what if...) faster on space spation MIR, im sure they'd sync their clocks to tick together with sea-level clocks and keep sea-level UTC time.

but! a person aboard MIR would manage to do 20 pushups within this UTC synced minute compared to a person at sea level who'd be able to do 10 pushups within that same UTC minute.
the person on the space station would measure 10 pulsar pulses during 20 pushups during 1 minute of UTC synced time on his clock. the person on sea level would measure also 10 pulsar pulses during 10 pushups during 1 minute of UTC synced time on his clock.

so do you see the point? naturally they both measure the same frequency of the pulsar as they tuned both their clocks to UTC. but one can do more pushups - more local action - per one pulsar pulse or UTC tick.
I'm not sure about using pushups as a reference, but you just illustrated the error in thinking that relativity theory fosters. You are correct about the pulsar timing staying in synch with UTC time and spacestation time if spacestation time is synchronized with UTC. That IS the universal time scale. Suppose we use a rotating flywheel instead of pushups for a reference. If the flywheel rotates at 10rpm, it will rotate at 10rpm according to the pulsar, the UTC clock and on the spacestation, if spacestation time is synched with UTC time. Only when spacestation time is not corrected will the flywheel rotate at a different rpm according to the local spacestation clock. The local clock is in error, not the universe and universal time.

pushups is indeed a better example than your flywheel as i will explain.

if a flywheel is set up to run at 10rpm it will run at 10rpms, it's that simple.. so that makes the example useless.

lets say you have two capacitors each with the same amount of charge-energy "trapped" in them.
lets say the energy is somehow used to spin up a flywheel, one flywheel on my hypothetical space station MIR and one at sea level. the flywheel on MIR will achieve a higher angular speed - more rounds per UTC minute(!) for the same amount of energy.
if the RPMs were timed using unsynced - "local time" clocks(they were synced on earth to standard 1 second, but the orbiting one was not resynced when it reached orbit) they would time the same RPMs for both flywheels.
so, the local time clock is correct for local action.

this is why i used pushups as example of local action. the whole action must be executed exactly the same both at sea level and orbit level -same amount of energy must be used - and then the result momentum is timed. if both are timed using UTC synced clocks then it will be shown that energy is more "worth" in geostatic orbit.

so, the local clock is in error if it is used to time nonlocal action(pulsar) and then the result is compared to sea level measurements. naturally they will not show the same results.
the orbit local time it is not "in error" though, it is just that we chose UTC time as dominant for practical reasons - most of humanity does work and live near or at sea level.

You are speaking of clocks, not time. The difference in the two is what I am trying to illustrate.
Unsuccessfully, since you specifically spoke about the misalignment of clocks causing chaos.

Coordinated Universal Time (UTC) is kept by the International Earth Rotation And Reference System Service. It is comprised of a worldwide network of 200 precise clocks. This ensemble of clocks is accurate to a tenth of a billionth of a second per day. The 38 microsecond/day error of a GPS clock would be a HUGE error if it were not corrected to keep coordinated time with UTC time. Clocks on mountains also have to be corrected to keep UTC time. If the montaintop clocks were not corrected, they would not keep official universal time.
All clocks have to be corrected to keep UTC time. Each individual clock in the ensemble has to be corrected at intervals to keep to the average of the ensemble.
Clearly, "absolute chaos" does not ensue from "clocks all over the world beating at different rates."

vx220,
lets say you have two capacitors each with the same amount of charge-energy "trapped" in them.
Does the capacitor retain the same amount of energy in orbit as it had on the ground? Do atoms gain energy when moved to higher gravitational potential, do they lose energy, or do they keep the same amount of energy as they had on the surface? If they keep the same amount of energy as they had on the surface, the surface time scale is correct at both locations. Measuring energy by a 'local' clock that was unsunchronized with the surface clock would change the relative energy measurement. If the energy level of the capacitors is different in orbit, then physics is a relative measurement and not is invariant between reference frames.

“ Originally Posted by 2inquisitive
You are speaking of clocks, not time. The difference in the two is what I am trying to illustrate. ”

Pete,
Unsuccessfully, since you specifically spoke about the misalignment of clocks causing chaos.
Clocks that are not synchronized in time will cause chaos. Clocks that do not keep time with UTC are faulty according to the universal time scale, whether they are atomic clocks or a cheap wind-up ararm clock.

Pete,
Clearly, "absolute chaos" does not ensue from "clocks all over the world beating at different rates."
If all our power grids were using clocks that beat at different local tick rates, they would get out of synch and inaccurate switching between grids would cause the power gids to fail. Same with our communication networks. Worldwide blackouts and severe communication loss would seem to lead to chaos to me, but not you Pete?

If all our power grids were using clocks that beat at different local tick rates, they would get out of synch and inaccurate switching between grids would cause the power gids to fail. Same with our communication networks. Worldwide blackouts and severe communication loss would seem to lead to chaos to me, but not you Pete?

2inq the clocks do beat at different rates. This is nothing to do with relativity - it's due to engineering limitations.
They need to be adjusted regularly to stay synchronized.

I haven't seen this lead to chaos - have you?

“ Originally Posted by iam
so does this mean i age faster on a mountaintop than at sea level, hehe? ”
Trilairian,
Yes
The Earth has been rotating for over 4 billion years. Since 'time' is accumilating faster on mountaintops, is that the reason we see sun rise earlier on a mountaintop than in a valley? :)

vx220,

Does the capacitor retain the same amount of energy in orbit as it had on the ground? Do atoms gain energy when moved to higher gravitational potential, do they lose energy, or do they keep the same amount of energy as they had on the surface? If they keep the same amount of energy as they had on the surface, the surface time scale is correct at both locations. Measuring energy by a 'local' clock that was unsunchronized with the surface clock would change the relative energy measurement. If the energy level of the capacitors is different in orbit, then physics is a relative measurement and not is invariant between reference frames.

These are all irrelevant questions IMO.

If energy mysteriously increases its "value" due to elevation from earth, that means energy "value" is depends on the local gravity field strength.

In the end, it must be realized this is irrelevant as energy IS spacetime. So it really doesn't matter if energy is "declared" static/fixed/flat or spacetime is "declared" flat/fixed/static. It is a question of preference, and since most of our commonly used physics laws insist on energy preservation rules - spacetime is the "declared" to be curved and energy is static/fixed/flat through this curved spacetime.

Anyway, the point is, time - as a dimension, really does "run faster" in geostatic orbits local frame. But we have no use for a clock to keep this time as nobody cares about the satellites local time frame.

Come off it, 2inq. Clocks do beat at different rates, even if they're located in the same room. This isn't because of relativity - it's because of engineering limitations. It's not possible to construct two clocks to beat at exactly the same rate - there is always some error.

I'm pretty sure that the predicted differences in rates due to relativity between clocks on Earth's surface is too small to be separated out from these engineering imprecisions.

As long as we don't get into THEORETICAL matters that would strain your brain.

Does a cesium clock on top of a mountain tick slower then a clock on sealevel due to gravity?.....

Does the same hold true for optical clocks?

According to Einstein Relativity, there is a time slowing due to velocity, and also a time slowing due to gravity.

At a higher relative velocity any physical process is observed, by a slower observer, to be slower.

In a higher gravitational field strength any physical process is observed, by an observer in a weaker field, to be slower.

On a mountain on Earth the mountain top is moving faster due to the planet's rotation.

On a mountain on Earth the mountain top is further away from the center of mass of the planet and tends to be in a weaker field.

On a mountain on Earth the mountain top has the mass of the mountain itself near it which tends to put it in a stronger field.

So all the pertinent factors for a specific case would have to be taken in account to derive a sum for the slowing or speeding up predicted by Relativity.

I almost forgot to mention what might happen to an hourglass. You know, those things with two chambers one atop the other, with one chamber initially filled with grains of sand.

In a very strong gravitational field, such as on the surface of a neutron star, Relativity says the hourglass will run slow. But plain logic says that the strong gravity will suck the sand down quicker and make it run faster.

Lest anyone quibble about frictional sand grain viscisity, we could just as well consider a water clock, very similar in principle to an sand hourglass but using water rather than sand grains.

In a very strong gravitational field, such as on the surface of a neutron star, Relativity says the hourglass will run slow.
:D Perhaps you should think before spouting, cnagas.

You say that GR says it will run slow... compared to what? An hourglass on Earth? An hourglass in freefall? An hourglass in a centrifuge?

Think it through. I know (well, I hope :rolleyes:) you can do it.

Perhaps it would help if you thought about pendulums first - there is a well known Newtonian formula for the period of a pendulum. If you adjust that formula for relativity, do you think it says that a pendulum has a faster period on Earth, or on a neutron star? Now prove it.

Anyone who is both able and interested in reading authoritative information about the Einstein Relativity predictions of time dilation, due to velocity and due to gravitational field, may obtain and read these excellent books:

Relativity by Albert Einstein. The equations and the logic of the assumption is explained by the inventor of gravitational time dilation himself.

Einstein's Legacy by Julain Schwinger. This is a really good expose' of Relativity time dilation in more depth than Einstein's book. I highly suggest it reading it for anyone who is eager to understand the time dilation predictions of Relativity.

Gravitation by Misner/Thorne/Wheeler. This huge book is an overdose of General Relativity for many but will answer a great number of questions about every aspect of Relativity predictions.

:D Perhaps you should think before spouting, cnagas.

You say that GR says it will run slow... compared to what? An hourglass on Earth? An hourglass in freefall? An hourglass in a centrifuge?

Think it through. I know (well, I hope :rolleyes:) you can do it.

Perhaps it would help if you thought about pendulums first - there is a well known Newtonian formula for the period of a pendulum. If you adjust that formula for relativity, do you think it says that a pendulum has a faster period on Earth, or on a neutron star? Now prove it.



You never think about your post before submitting it. Practise what you preach, then maybe someone will believe you.

My post was intended to provoke intelligent thought and discussion on the issue. I regret to see that once again you did not get the point.