DaveC426913 said:You did conclude that time travel exists. You equated time dilation with time travel. Since we see time dliation every day, your logic tells you that time traveling is indeed occurring.
Which it is - if you accept that as a definition of time travelling. That family on the top of Mt. Rainer experienced a few more microseconds than we did. If you want to look at that as time travel, so be it.
jadgerz said:I ASKED the question as to whether other people in the forum consider time dilation as time travel. And did not say that it was. What do you think it is?
edpell said:A person on Earth "observes" the flashes [let us say the clock on the ship emits a light flash every one second ship time] at a lower frequency due to the, distortion caused by the, finite speed of propagation of light. Versus if we have [this is a thought experiment] a signal that propagates at say 10^100 times c would the observer on Earth see the flashes at a rate of one per Earth clock second?
jadgerz said:Edpell, please forgive me. In a later blog I suggested your very same experiment as an experiment to test time dilation. With the exception I proposed trying to speed up a space probe at a "significant" percentage of light speed so there would be no doubt as there are at these nano and micro second variances that any possible change in "flash time" could be attributed to time dilation. I was unaware of this blog on your part and forgive me if I have made it seem it was my proposal. Credit where credit is due. It is yours.
edpell said:My memory is that no one responded to my thought experiment. I still think it is a interesting question.
Janus said:We are not talking coordinate acceleration. We are talking proper acceleration, or the acceleration measured by an accelerometer. An accelerometer attached to a clock in orbit would read zero no matter the altitude of the orbit.
Janus is correct. An accelerometer detects proper acceleration, not coordinate acceleration. So an accelerometer in orbit (or any free fall) reads 0. A spacecraft is not always in free fall, so the fact that it reads 0 in orbit doesn't prevent it from being useful.jadgerz said:Try again Janus. Are you saying all those inertial guidance systems carried on all those spacecraft (mercury, gemini, apollo, etc.) were just for looks?
jadgerz said:Let's say that flash interval was exactly one second as you suggested. If an observer on Earth saw the flash as every 1.01 second he would know that an observer on the probe would be seeing the flash at 1.00 second, because it was pre-set thus, and the Earth observer could conclude there is something to the time dilation theory. I hope I made sense with that. I just don't believe the round the world airplane trips with atomic clocks puts the matter to rest.
edpell said:What about lateral red shift?
DaleSpam said:Janus is correct. An accelerometer detects proper acceleration, not coordinate acceleration. So an accelerometer in orbit (or any free fall) reads 0. A spacecraft is not always in free fall, so the fact that it reads 0 in orbit doesn't prevent it from being useful.
edpell said:What about lateral red shift? That is if an light emitting object in space is moving toward us we see a blue shift and if it is moving away from us we see a red shift. If an object is moving laterally we should also see a red shift due to the time dilation effect slowing the frequency of the particular transition observed. This may have already been done? If not this seems like a great experiment waiting to be done. How exactly you determine the motion of the object by means other than red shift is the question. I would think jets emitted from things that have jets (i.e. neutron stars with accreting matter?) would work.
jtbell said:This called the transverse Doppler effect and has been observed:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html#Tests_of_time_dilation
edpell said:What about lateral red shift? That is if an light emitting object in space is moving toward us we see a blue shift and if it is moving away from us we see a red shift. If an object is moving laterally we should also see a red shift due to the time dilation effect slowing the frequency of the particular transition observed. This may have already been done? If not this seems like a great experiment waiting to be done. How exactly you determine the motion of the object by means other than red shift is the question. I would think jets emitted from things that have jets (i.e. neutron stars with accreting matter?) would work.
jadgerz said:Can any of you geniuses out there ...
In Upton, New Yorkjadgerz said:Where do we get an opportunity to observe near light speed with ordinary matter like this?
DaleSpam said:
So what? It is still ordinary matter at highly relativistic speeds. And the path is actually a rounded off hexagon with six straight sections where the detectors are placed.edpell said:Yes and no. At Brookhaven matter goes in a circle not a straight line.
edpell said:Has anyone done an experiment at Brookhaven with radioactive ions and measuring the decay rate in the straight sections?
DaleSpam said:that is probably how they got the estimate for the speed of the jets.
You know, I am a little tired now, so I may be a little over-sensitive, but I am finding this question rather obnoxious when such experiments have already been cited at least 3 times in this thread alone, twice by me. How many times in a single conversation do I have to provide references before others can be bothered to look at them?edpell said:has the SR affected muon lifetime in fact been measured?
edpell said:When people talk about accelerators they talk about muon tracks that are many times longer than the track length traveled in one muon lifetime. But has the SR affected muon lifetime in fact been measured? To what level of accuracy?
Yes, since the relative velocity drops to zero at one point. But the traveling clock runs faster as it slows down, to a max of the same rate of Earth's clock, then runs slower as the relative velocity increases again. Certainly we can't say the acceleration slowed down the ship clock when it runs the slowest during inertial motion.ThomasT said:So the Earth twin will see no change in the tick rate of the traveling clock during the trip?
Yes, but not necessarily acceleration of the clock. The change in the rate of a clock depends on a change in v in exactly the same way whether the clock accelerates or the reference frame accelerates instead.I thought that "change in v" = "acceleration".
Mentz114 said:For the umpteenth time, may I point out the confusion between 'time dilation', the fact that IFRs in relative motion see each others clocks slowed by the gamma factor, and differential ageing. The first is an observer dependent effect, the second is not.
If you believe that the mutual apparent slowing of clocks is not observer dependent, then this leads to an apparent paradox.
Instantaneous observations of another frames clock cannot be used to extrapolate to what will happen when the clocks meet and are compared. They are different phenomena.
I don't expect this post to make any difference because some posters here (jadgerz ) don't understand SR and are clearly driven by some prejudice or other.
atyy said:Ashby, Relativity in the Global Positioning System
http://relativity.livingreviews.org/Articles/lrr-2003-1/
"Also, experimental tests of relativity can be performed with GPS, although generally speaking these are not at a level of precision any better than previously existing tests."
"There is an interesting story about this frequency offset. At the time of launch of the NTS-2 satellite (23 June 1977), which contained the first Cesium atomic clock to be placed in orbit, it was recognized that orbiting clocks would require a relativistic correction, but there was uncertainty as to its magnitude as well as its sign. Indeed, there were some who doubted that relativistic effects were truths that would need to be incorporated [5]! A frequency synthesizer was built into the satellite clock system so that after launch, if in fact the rate of the clock in its final orbit was that predicted by general relativity, then the synthesizer could be turned on, bringing the clock to the coordinate rate necessary for operation. After the Cesium clock was turned on in NTS-2, it was operated for about 20 days to measure its clock rate before turning on the synthesizer [11]. The frequency measured during that interval was +442.5 parts in 1012 compared to clocks on the ground, while general relativity predicted +446.5 parts in 1012. The difference was well within the accuracy capabilities of the orbiting clock. This then gave about a 1% verification of the combined second-order Doppler and gravitational frequency shift effects for a clock at 4.2 Earth radii. "
This is simply wrong. The math and how you use the math to make experimental predictions are the theory. So you cannot make math equations fit any theory because if you change the math you have changed the theory.jadgerz said:Yes! The MATH for SR and GR all work out well on paper. It's comprehensible by anyone who has taken any math course up to differential equations. But math equations can be made to fit any theory.
A simple look at history debunks this critique. The first accurate atomic clock was built in 1955. So none of the many experimental confirmations of SR before 1955 could possibly be subject to this weakness. See: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html. There are also many experiments after that time, such as Kuendig's 1963 experiment with a Mossbauer absorber on a rotor, that did not rely on atomic clocks.jadgerz said:His "complaint" was that atomic clocks can not be used to accurately test relativity due to intrinsic problems related to atomic clocks themselves. Thus any test on relativity using atomic clocks must be suspect. Note however, that neither of these gentlemen deny relativistic effects. They simply critique the means used to test it.
DaleSpam said:First, I would like to remind you that PhysicsForums is not for personal theories nor for crackpot arguments against mainstream science, there are plenty of other internet forums for that. PhysicsForums is for helping students and others learn about mainstream science. You specifically agreed to those terms when you signed up for your account, and citations of notorious crackpots like Van Flandern are a violation of your agreement. This is simply wrong. The math and how you use the math to make experimental predictions are the theory. So you cannot make math equations fit any theory because if you change the math you have changed the theory.
What you may be thinking of is the fact that you can always produce multiple interpretations of the same theory. I.e. you can ascribe different meanings to the various mathematical quantities. A good example is the relationship between SR and Lorentz's Aether Theory which are both different interpretations of the same mathematical theory, the Lorentz transform. I am not sure if your stance is that the Lorentz transform is correct, but SR is an incorrect interpretation, or if you believe that the Lorentz transform is wrong.
A simple look at history debunks this critique. The first accurate atomic clock was built in 1955. So none of the many experimental confirmations of SR before 1955 could possibly be subject to this weakness. See: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html. There are also many experiments after that time, such as Kuendig's 1963 experiment with a Mossbauer absorber on a rotor, that did not rely on atomic clocks.
Let me be clear here, I am not in any way accepting your critique of atomic clocks, but for the sake of argument I am just pointing out that the success of SR does not hinge on that.
I know, that is why I said "PhysicsForums is not for personal theories nor for crackpot arguments against mainstream science". Please review the rules.jadgerz said:So why do they still let you in here? I don't propose any theory "of my own".
Then please, address the substance of my rebuttals and show where I was wrong. The fact remains that the experimental support for SR is broad and overwhelming. It simply does not hinge on a couple of key technologies.jadgerz said:quite frankly, it is YOU who are wrong.
Mentz114 said:may I point out the confusion between 'time dilation', the fact that IFRs in relative motion see each others clocks slowed by the gamma factor, and differential ageing. The first is an observer dependent effect, the second is not.
