Physics 62.1 Understanding Space, Time & Relativity (14 of 55) Hafele-Keating Experiment
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In this video I will explain how in 1971 the Hafele-Keating experiment used a series of HP 5661A Cesium beam atomic clock to prove Einstein's special relativity that time does indeed slow down at high rate of velocity.
Next video in this series can be seen at:
• Physics 62.1 Understa...
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You deserve so much more likes and views as I have found your relativity series to be incredibly helpful. Keep doing what your doing.
Thank you a lot, sir. I didn't know about this experiment and now I do because of your video.
Interesting experiment. What I question is the frame of reference used. If we take the stationary clock to be our frame of reference it shouldn't matter in which direction the plane was flying. Adding/subtracting the earth's rotational velocity from the plane's velocity creates a problem. Placing the clock on a plane flying against the earth's rotation but at a speed identical to the earth's rotation, would the clock show no time dilation when the plane returned to the original point 24 hours later? Would this nullify the idea of time dilation since the plane velocity would have been canceled by the earth's velocity. Additionally, including the earth's motion, brings back the idea of the aether. Please explain my misunderstanding.
For a stationary observer (away from the Earth) the two planes flying in opposite directions will have different speed due to the rotation of the Earth.
@@MichelvanBiezen Was there a caesium clock in space used as a control in the experiment?
A few questions.
1/ When both planes are on opposite sides of the planet their relative speed is zero - does this matter?
2/ How are all the relative velocities calculated? For example, when either plane has travelled through a 1/4 rotation, do we use trig to calculate all the absolute velocities between the planes and the ground station? Because the only time you need not do this is when the planes are either at the point of the ground station or on the other side of the planet - you need trigonometry for every other point around the earth, right? Did they do all this calculus?
3/What is the frame of reference - the centre of the earth or the ground station? If it is the ground station then that is clearly not an inertial frame of reference.
I'm sorry, but I will need to see this done in outer space with everything moving in straight lines and gravitational effects greatly insignificant!
Since the plane's speed is relative to the Earth's surface, when they are on opposite ends of the Earth, their relative speed will not be zero. The time effect will depend on the relative speed to space.
@@MichelvanBiezen Relative speed to space? That sounds like the universal frame of reference!
But anyway, what about all the trigonometry required? Or what exactly is the frame of reference for this experiment?
The experiment was done to determine if there would be a difference and indeed there was. Now we need to determine why.
@@MichelvanBiezen Frankly, I put a huge ? over the entire thing. I would go so far as to call this a deliberate forgery. And the numerous follow ups.
None of the FORs are inertial.
From what I see, none of the relative velocities have been calculated correctly at all.
You are certainly entitled to your opinion. And we should all be ready to question anything the "experts" say.
I'd hypothesize the west bound flights should arrive to their destinations faster since the earth is moving the opposite direction and the east bound flights would take longer to arrive at their destination because they have to go faster then the rotation of the earth to reach their destination. But with this evidence relatively speaking the flights take the same time east to west because of time dilation...it's definitely not because the earth is flat...
Although I have now forgotten the details, there was another experiment around 1975 and others after that. I think cesium was the 'clock' in some experiments where precautions were taken to protect the instruments from magnetic field and other effects. The result(s) was/were in agreement with relativity. Naturally, there were given + or - minus error values for the experiments but relativistic values were within these limits. However, what is misleading is that adjustments and error measurements don't just involve relativity (SR & GR). For example the GPS and Russian systems both use complex algorithms for signal delay (receiver & emit), atmospheric and other effects and once that is done then adjustments due to relativistic effects can be made.
The data from the Flying & Stationary Atomic Clocks experiment (Hafele & Keating) was a mess. Hafele & Keating had to massage the data just to get anything sensible. The total range of drift for the 4 clocks was 7000ns. Even if you take the massaged results at face value, those results actually disproved the underpinnings of special relativity. Einstein claimed that all moving clocks are supposed to run slower with respect to the observer (& that all inertial frames are equal), but the west-bound clocks sped up by 273ns compared to the Stationary clock . and the east-bound clocks slowed down by 59ns. Hafele even admitted that the miss-match between Einstein's Relativity predictions and the measured data was "disturbing".
Hafele had to use “motion with respect to the underlying nonrotating inertial space” to get the math anywhere close to agree with relativity predictions. So basically they had to create an absolute reference frame., in other words an "ether". Because everything in the world around us and clocks are made of atoms and governed by Electromagnetic force, what we call Time & measure as Time is just the rate at which atoms and subatomic processes occur (what you would call local time). So its logical to expect that motion and gravity will have an effect on these process thus effecting "time"
The underpinnings of special relativity are completely flawed. Looking closely at the experiments cited as proving Einsteins relativity, such as the 1919 eclipse, 1971 Atomic clocks, Gavity B probe, the data from these experiments do NOT match the predicted value from Einsteins relativity, the data has to be manipulated to get anywhere close. GPS corrections doesn't match Einsteins relativity predictions. The rotation of galaxies don't match the Einsteins relativity, thus the need for the Mythical Dark Matter.
Yes, okay, so you seem to be in the camp against SR & GR, and I am opposite. That's not a bad thing as long as both of us have reasons for being where we are. When people don't understand the principles but still claim this & that just based on faith, is when I choose to terminate conversations with them. I have to say that working through the equations (various methods) and bearing in mind I am not a practicing scientist (retired with technical background), I have to depend on what both camps have to say in articles etc.. On the particular experiment cited (H & K) I would thought statistically speaking, that the eastbound figures would be of more concern, predicted 40 + or -, measured 59 + or -. I haven't worked it out precisely but that difference will be at least greater than 2/3 of a SD. The westbound showed much less difference in predicted vs measured values being something in the region of 0.1% difference. But in late last century and early this century the NPL conducted further experiments both London to Washington and a later round the world trip. I admit to not knowing the details but closer agreement with SR & GR was apparently obtained.
Having said all that I don't make a good mainstream supporter as I too have concerns about the standard model (both of them) but that's all for other conversations. For the moment I am mainstream (because I don't like to sit on the fence) yet feel that SR , GR and EM theory are infants of something else.
So now tell me what the results should have been if the clocks were flown North-South rather than East-West? Same velocities but no Earth's rotation to add/subtract.
Couldn't other forces cause some clocks to run slower by taking off and landing, or maybe the gravitational pull is stronger at lower altitude?
All that was accounted for in the experiment. The same elevation was kept for both planes.
Please, comment.
My problem with this experiment is that the Earth's gravity is (might be) affecting the Clocks. Therefore, the "observer" is not neutral to the experiment.
Is there a similar experiment conducted outside of the Earth's influence?
Since the planes fly at altitudes of about 10,000 m, the gravitational effect differences are very small and not the dominating factor here.
@@MichelvanBiezen
Thanks for the reply.
However, all the objects on such a low altitude fall to the ground and are affected when flying west or east. So, instead of assuming what you just assumed, I would like to read about any experiments conducted in the outer space, where objects like planes or all kinds of clocks are not affected by the Earth's gravity (whatever the nature of that gravity might be).
Thank you for teaching me how to reset the universe, much appreciated
Happy to help
why is the time difference asymmetrical for the different directions? for general relativity time dilation , i assumed it was because the planes wouldn’t fly on exactly the same altitude. but for kinetic time dilation, shouldn’t it deviate for eastward and westward plane by the same magnitude? because if we’re saying the clocks are on earth, can’t the earth’s velocity be taken as 0, so the westward plane will be -v and eastward will be v. i think the wrong assumption comes from assuming earth’s velocity can said as 0, but im not sure. please help!!
The only thing matters is the speed of the airplanes relative to the position of the Earth Clock. I'm not convinced that the plane flying East has greater V, rather smaller ? There is no numerical proof here. According to Einstein theory, Pilots on the planes must see the Earth Clock slow down too, because the position of the Earth Clock is moving relatively to the plane position. And it's not mentioned here ?
If I understand what you're saying, that would be assuming that the static earth clock had a speed of 0.
So why not explain how much different the clocks were? There's so much information left out for me to analyze it.
This series of videos is geared towards the conceptual description. If you are interested in the actual calculations, we have examples of that in our GPS videos where we have to adjust the clock time for the effects of both the general theory of relativity and the special theory of relativity.
Eastward Clock 120 -196 ns; clock 361 -54 ns; clock 408 +166 ns; clock 447 -97 ns. Westward clocks: Clock 120 +413 ns; clock 361 -44 ns; clock 408 +101 ns; clock 447 +26 ns.
Average Eastward -45 ns. Average Westward +124 ns. Predicted results: Eastward -45 ns; Westward +275 ns. Data source: From the Institution of Engineers of Ireland, "Reliability of Relativistic Effect Tests on Airborne Clocks" by A G Kelly PhD (Fellow)
A lot of shuffling, assuming, and manipulation was required to achieve the predicted results. The clocks would have to be orders of magnitude more stable/accurate to prove the theory. What I consider to be the largest blunder was they did not consider the earth's orbit around the sun. The side of the earth that is facing the sun is rotating at 1000 MPH opposite the 66,500 MPH orbital velocity of the earth. At night, the side of the earth away from the sun is rotating at 1000 MPH in the same direction as the 66,500 MPH orbital velocity. The eastward clocks would therefore run faster during the day and slower at night neutralizing any effect of time dilation.
If you're measuring time dilation relative to the earthbound clock all that matters is the speed of the airplane relative to the earthbound clock. In the experiment, the earthbound clock, the atmosphere and the airplane are all moving with the rotation of the earth so that motion is irrelevant. The velocity of the airplane relative to the earthbound clock is the same whether the airplane is going east or west (or north or south). So why is time dilation relative to the earthbound clock not the same for all directions?
I agree with you. By adding and subtracting the earth's rotational velocity, are we not moving the frame of reference to somewhere away from the earth, somewhere like space or the disproved aether?
Is it possible to re-generate the result achieved through Hafele-Keating Experiment? It will be of great help to learn
We could, but why do it again? We have conducted many other experiments that have given us great insight.
@@MichelvanBiezen My motive is to learn by combining the calculations of the special and general relativity. The two papers published about this experiance did not show the calculation for those who are notfrom the field.
if the planes are moving at the same speeds relative to earth, then due to v^2 in the time dilation equation it does not matter if they are moving in the same direction or in opposite directions, relative to earth, since (+v)^2 = (-v)^2.
Since the Earth rotates and the planes are flying at speeds relative to the Earth's surface, they will have a different velocity relative to space. Apparently that makes a difference since their clocks showed a difference in elapsed time.
@@MichelvanBiezen I am not disputing the experimental results. that will not be scientific. what I find bothersome is how the kinematics of STR is used to explain dynamical processes. the planes are not inertial reference frames. people seem to have forgotten that speed and velocity are not equivalent. simply by change in the direction of the velocity vector we can have acceleration and force. the change in the velocity vectors of the two planes will be in opposite directions relative to each other and the earth surface. this will result in inertial acceleration and in turn from Einstein's GTR in gravitational acceleration and gravitational fields associated with each of the two planes. unfortunately, in the love for Einstein people seem to forget Newton who continues to remain valid despite all the developments since Newton.
Newton's equations are only correct at non-relativistic velocities, but are not correct at relativistic velocities as was shown in that experiment (as well as in many other experiments)
@@MichelvanBiezen that is correct. I was just saying that speed and velocity are not equivalent entities as one is scalar and the other vector. I am not sure now but we used 's' for speed and 'v' for velocity to remind ourselves of this difference even if we did not mentioned or put the arrow sign over 'v'. even at relativistic speeds, we use force as dp/dt with 'p' as a vector. we do not use 'mg' because m=m(v). the laws of conservation remain applicable except instead of two separate laws with one for mass and one for energy we have one for mass/energy. but linear momentum, angular momentum conservation laws do not change. also for charge. we have an upper limit for linear speed of 'c', but there is no upper limit for angular speed 'omega' which is linear speed times distance from the center. it can be greater than 'c' in value as we can have v*r, with r>0, with a value > c. similarly no upper limit of accelerations, both linear and angular. for linear acceleration we have a=v/t. if t = 10^-10 sec, then a = v*10^10 which can have value >>> c. I prefer GTR to STR as the former is a dynamical theory dealing with processes and entities that are dynamical rather than STR which is purely kinematical. the tensor is much better than the scalar. for me tensor is equivalent to relativistic "Newtonian vector". of course, the tensor has 16 scalar components instead of the four components of a vector consisting of 3 space and 1 time. my physics professors told me to use GTR instead of STR. it is very easy to apply GTR since gravitational acceleration is equivalent to inertial acceleration and hence is applicable both as a gravitational theory as well as a dynamical theory of inertial acceleration. the results of the experiment you have discussed will be the same but without any paradoxes if we use GTR.
@@MichelvanBiezen "space" has nothing to do with this experiment. And its wrong to claim that the velocities of the planes must include the rotational velocity of the Earth. In any direction, a plane has a speed relative to Earth clock of about 500kph. So there is zero difference between the speeds of the planes relative to any earth clock, Both will be 500 kph, because that how fast a plane flies. Space is not a factor in this experiment, as the relativistic math only ever considers the speeds relative to the earth clock, and the two planes clocks. So no different in a west or east bound plane speed as you claim.
So does this really actually prove time dilation just because people think it does due to the results of some clocks, or does it show that tools, such as clocks built here on Earth, are merely influenced by gravitational waves of varying velocities?
Time dilation is real. It has been measured in a number of ways.
@@MichelvanBiezen Answers like these are par for the course in modern science, but just fyi, it shows that "trust me" is enough for you, since you expect that to be enough for them.
He didn't say "trust me", he said that time dilation has been measured.
No one asked you to trust what they say. You can just make the same experiment (same conditions etc.) and you will get the exact same reaults.
Why would you did you think that he meant to just trust him?
Explained well thank you :)
So which clock would be slower if the H-K experiment was done North-South? And why?
@Richard Linsley-Hood
? re your comment "So which clock would be slower if the H-K experiment was done North-South? And why?" < That's an interesting question.
The two flying clocks would read about the same, no?
Maybe not information.
I think the only difference here would be removing the speed of the earth's rotation from the equation. Both planes are still flying at the same speed relative to each other. The E-W model just acts as a modifier to widen the gap and make the difference bigger, probably to make the results more evident.
@@jawaring4367 The speed between the planes will be the same regardless in they fly East-West or North-South, so they should show the same differences regardless. Half of the time the distances between them will be increasing, the other half decreasing. Now compare the E-W and the N-S planes. How do they differ?
Thank you
You're welcome
What if velocity be light velocity then what , ?
Objects with mass cannot travel at the speed of light.
Amazing class. Congrats!
Doesn't that indicate that space has absolute reference points albeit warped by General Relativity? Couldn't we map the Universe by comparing clocks all throughout to find the greatest rate of time passage and therefore the slowest velocity through space?
Yeah, i was wondering this too. I was thinking that maybe this only applies to rotational velocity since gyroscopic movement is the only motion detectable on space.
For a thought experiment if you have 3 objects one going left one in the middle and going right, do the left and right have the same time? What if you are standing on one of the moving objects? Would you measure the object in the middle to have less time and the other moving object that is moving twice as fast away to have no difference in time?
Unless time magically turns into a vector i dont see how this can be resolved.
@@tyty8484 Great question only by comparing clocks could you determine the true nature of the objects with respect to the space they occupy.
If the object in the middle was absolutely not moving through space It would experience the most time (events) and if the other two objects are moving away from the one in the middle at 90% the speed of light They would experience half the time as the middle and yes their clocks would run at the same rate.
@@1965ace Hmmm how about this. The one plane going counter rotationally was observed to have experienced a time contraction. What if its speed was increased? Would it experience more contraction? What if it was moving the same speed around the axis as the other plane going the opposite direction? Would it then have the same time dilation as the other plane? Would that signify a local base frame or a universal base frame?
What if the 3 objects going left right and still from the previous example are all moving in the same direction perpendicular to the direction of action. i.e. in a forking direction. Do they experience the same relative time dilations as the ones from the original example? Lets say theyre moving appart at 0.9C and also they set moving in the 3rd direction ate moving away at 0.9C.
I honestly feel like maybe theres a problem with the equation in the way that it treats a vector and a scalar exactly the same. Also i want to see more attempts at recreating this experiment with additional data points. Ive become pretty skeptical after reaching a certain age.
@@tyty8484 The problem is looking at an experiment from the perspective of being part of the experiment. I like the "God" perspective seeing the whole thing from the greatest vantage point.
If you could see space like a medium that is constantly moving speeding up toward massive bodies then the complexity of time dilation is easier to understand. Since spacetime is not a flat linear medium we have to factor objects moving through it and it moving through objects.
We know that momentum is conserved when an object moves through space and it's conserved and accelerated when space moves through objects (gravity).
Adding to this is rotational warping. The basic Idea is what is an object's relationship to the space surrounding it is directly related to the time dilation.
@@1965ace What does this have to do with anything we were talking about?
Thankyou
Glad you liked it. 🙂
Doesn't that disprove the realitive part there was a definitive slowest clock meaning they were all based on universal rest state not an observer chosen one.
Realitivity requires any clock can claim rest state the other two both must be slower that it being in some motion realitive to it
We have not yet observed anything that appears to "disprove" the special theory of relativity.
@MichelvanBiezen the calculation for this experiment only works in the preferred inertal frame of the center of the earth, not all inertal frames. We certainly didn't observe them from that inertal frame
Problems like the twins paradox aren't problems with a preferred inertal frame.
If this explanation were true, the West-bound plane doesn't have to travel to reach the destination. It has to be up in the air for some time and the rotating earth will bring the destination below the plane due to its rotation. It doesn't happen in reality. I guess, the rotation of the earth doesn't affect the speed of the planes. For the planes, the Earth is stationary like a high jumper's perspective.
When a flying clock is diametrically opposite the Earth clock their relative speed is very small.
Actually their relative speed is greater. Meaning relative to fixed spots on the earth passing below them.
You mean actual speed with respect to what effects time dilation.
But maybe I didn't understand what you meant ?
Even still you cover more ground flying against the rotation of the earth with the same apparent speed and time , apposed to with it.
Ergo relative speed is increased , because more distance relative to earth = faster.
We are taking the relative velocity's but plane is flying apart from Earth, is not it? Why do we add the earths velocity then ?
Because the earths atmosphere is moving with the Earth at the same speed as the Earth. When the planes are stationery on the runway, they are moving with the earth eastwards at approximately 1000 mph. When the plane heading eastward takes off and speeds up, if the plane is travelling at 500 mph, it is actually travelling east at 1500 mph because it still has it's initial eastward speed of 1000 mph, so you just add the extra 500 mph to its speed. The plane flying eastward is therefore travelling 500 mph faster than the clock on earth's surface. If the plane travelling westward is flying at 500 mph, this plane is actually still moving east with earth, but it is moving east 500 mph slower than earth is moving east and it is moving east 1500 mph slower than the plane flying eastward. If you walk, drive or fly west, you're still actually moving east with earth, unless you're moving west faster than 1000 mph. This is my interpretation anyway. Someone please correct me if I'm wrong!
@Daniel Smith Exactly and the refrence clock on ground is also moving relative to the earth's core.
Atomic clocks are not necessarily accurate, but they are precise.
What kind of clock they use😅
They used atomic clocks based on the oscialltion frequency of cesium.
if it is proven in some case, that gravity and acceleration affect the frequency of the atoms in the clock mechanism.and you have several documentary about this scenario.There is no space time curviture.
That is an interesting thought.
what a beast
It is a fascinating topic
@@MichelvanBiezen thank you tho :)
Was. Perhaps the magnetic field of the Earth, Sun and or Moon effecting the clocks in some mechanical sense? What type of clocks were these? Iron clad infalable mechanisms?
No.
Atomic clocks are extremely accurate and work on the principle that the natural vibration of oscillators does not change.
But don't the oscillators oscillate in space and time as well?
No.
Floyd Pinkerton
Okay then Floyd:
a. What exactly is 'space'?
b. What exactly is 'time'?
c. How exactly do space and time 'vary'?
d. What exactly is 'gravity' and how exactly does it do what it does?
Post this 1971 experiment any recent experiments done?
according to Wikipedia they repeated the experiment in 1996 and 2010 with the same results.
Great
A lie (in literature and textbooks). These atomic clocks, four: 120, 61, 408, and 447 were not accurate in order to record the tiny difference in clocks recordings. Check the original result in US Naval Observatory (now online and in Science,vol177- details by. A.G.Kelly,www.cartesio-episteme.net. Only one clock, nr 447 had a fairly steady performance but it showed no difference between East and Westward flights. All the data was "fixed"(447: from (-51nsec to -97) in Eastwood, from (=26) to +266 nsec) in Westwood. Only later experiments proved mainly a gravitational time dilation (Doppler effect) and not the Lorentz formula though mathematically they are equal (easy to calculate) in reference to the reference system at the center of Earth. You don't see it in this lecture.
Thanks for the information. With our GPS satellites today we adjust for both time dilation and the gravitational effects
I was trying to post a more direct link to the A.G. Kelly paper but for some reason TH-cam would not let my link be posted as yours is. Any suggestion how to do this?
@@rogerg4916 what i see is one cannot just "copy"+"past"-it does not work (for some reasons) One has to type it by himself
@@krzysztofciuba271 Thanks for the advice but I tried that several times, even using words like dot and slash but I still get a "Returned Error". Actually, to go directly to the paper all you need to do is add /H&KPaper.htm after net on your link.
I'm not a scientist so I'm not really understand the equation. But thank you very much for the experiment, it simply explained and proved the truth of the Holy Qur'an, came out way centuries before Einstein via the Prophet Muhammad PBUH, an uneducated man was lived in the desert land of Saudi Arabia 😄. The experiment really amaze me 😍
You dont understand, but you say it explains and proves the koran? which? You do not make the slightest sense. if you dont understand it, how can it prove anything - to you? have you heard of logic? Why are you here?
Sänks