Help wanted with an explanation

  • Thread starter MaeWest
  • Start date
  • Tags
    Explanation
In summary: GPS. What is being measured is not time, but clock inaccuracy. That is the experiment.The experiment is to take two clocks, one on a satellite and one on the ground, and compare their accuracy. The satellite clock will be inaccurate because it is in a zero g environment. The ground clock will be accurate because it is in a zero g environment.
  • #1
MaeWest
9
0
I have a BS in physics from some time ago. In another forum on another board I have become embroiled in a discussion with another poster about SR and the need to adjust the clocks on GPS satellites to account for SR effects. I need some help trying to explain things. As expressed by the other poster, our positions are

"And you keep missing the point about HOW they correct for the supposed time dilation. Time dilation, according to theory, DOES affect time itself. You could not, therefore, correct for it by adjusting the clock. IF it were really being observed, you would have to adjust for the variance via a different method of correction, but not through physically adjusting the clock to run slower.

"And no, the difference between what you are saying and what I am saying is this: you are saying that what is being observed is SRT/time dilation (effectively saying that time is what affected by the velocity of the satellites). I am saying the CLOCK is affected by the motion, NOT TIME. It may seem to give the appearance of affecting time, but it is the clock's mechanism that is affected."

Any suggestions on how to approach this? Nothing I've tried has worked to get through so far.
 
Physics news on Phys.org
  • #2
MaeWest said:
I have a BS in physics from some time ago. In another forum on another board I have become embroiled in a discussion with another poster about SR and the need to adjust the clocks on GPS satellites to account for SR effects. I need some help trying to explain things. As expressed by the other poster, our positions are

"And you keep missing the point about HOW they correct for the supposed time dilation. Time dilation, according to theory, DOES affect time itself. You could not, therefore, correct for it by adjusting the clock. IF it were really being observed, you would have to adjust for the variance via a different method of correction, but not through physically adjusting the clock to run slower.

"And no, the difference between what you are saying and what I am saying is this: you are saying that what is being observed is SRT/time dilation (effectively saying that time is what affected by the velocity of the satellites). I am saying the CLOCK is affected by the motion, NOT TIME. It may seem to give the appearance of affecting time, but it is the clock's mechanism that is affected."

Any suggestions on how to approach this? Nothing I've tried has worked to get through so far.
Well, what does it mean to say that time dilation affects clocks but not "time itself"? Does this imply that there is some objective truth about the factor by which a given clock is running slow relative to "time itself"? As a purely philosophical matter you can choose to adopt an "interpretation" of SR where there is a single inertial frame whose views on time/simultaneity/length are the objectively correct ones, so a clock moving at a speed of v relative to this preferred frame is "objectively" running slow by a factor of [tex]\sqrt{1 - v^2/c^2}[/tex] (this type of interpretation is sometimes called a Lorentz ether theory). But as long as SR is correct on an experimental level, the laws of physics should work the same in all inertial frames, meaning there would be no possible experiment you could do that would tell you which of the infinite possible inertial frames is the one whose opinions on clock ticking rates are "objectively correct". Assuming you are the person who takes the position that time really slows down, I guess you could explain to the other poster that different inertial frames can disagree about which of a given pair of clocks is ticking slower, and ask if the poster thinks there is any experimental way to determine the "truth" about this matter.
 
  • #3
you said:
Time dilation, according to theory, DOES affect time itself. You could not, therefore, correct for it by adjusting the clock.
Since a GPS essentially is nothing but a clock, it's of course enough to adjust the clock. How could it not be enough? Time goes faster, the clock is going slower, and everything is fine again. All other effects of time dilation are uninteresting for GPS.
another poster said:
I am saying the CLOCK is affected by the motion, NOT TIME. It may seem to give the appearance of affecting time, but it is the clock's mechanism that is affected.
Tell him what "time" means in this context: time is what a clock shows.
Operationally, this means: A satellite is a zero g environment. You go and build clocks that work in a zero g environment. Build all varieties you can conceive of, decaying muons, cesium, quartz, biological, whatever. All these clocks will have different accuracies, as can be seen by comparnig clocks with identical technology.
Now you adjust them once. Now observe the clocks at different velocites, with exactly this adjustment.
a) If they all show the same time within their accuracies, but different times than similar clocks with different veocities, it is said that time is affected, not the clocks. By definition.
b) If they all show different times according to their mechanisms, you'd say that the clocks are affected by something. But that's not what we observe.

If another poster believes that all conceivable clocks are affected exactly the same way by velocity, that's also case a) by definition.
 
  • #4
MaeWest said:
I am saying the CLOCK is affected by the motion, NOT TIME. It may seem to give the appearance of affecting time, but it is the clock's mechanism that is affected."
Well every physical process aboard that satellite is affected the same way, not just clock mechanisms. So let me ask you this: what do you think the problem is in saying that time is affected?
 
  • #5
Thanks for all of the responses. They are appreciated.

I did, by the way, try to get across the point that the "motion" of which he was speaking is simply the motion of the inertial frame, which is accounted for in SR and appears as time dilation - and got nowhere. It is almost as though he is on a hidden variable kick.
 
Last edited:
  • #6
MaeWest said:
Thanks for all of the responses. They are appreciated.

I did, by the way, try to get across the point that the "motion" of which he was speaking is simply the motion of the inertial frame, which is accounted for in SR and appears as time dilation - and got nowhere. It is almost as though he is on a hidden variable kick.
You might get somewhere by pointing out it is permissable to adopt an interpretation like the Lorentz ether theory I mentioned where there is a preferred frame and things like time dilation and motion are defined relative to it, but then mention that it would be absolutely impossible to decide which frame it is experimentally--that way, if he disagrees with the second part you can press him on what experiment he would propose to do it, and if he doesn't disagree with the second part you can just "agree to disagree" on the philosophical issue, pointing out that the complete "hiddenness" of the preferred frame is seen by many as a good reason to abandon such a notion.
 
  • #7
Just a general comment about GPS clocks. They run faster than the clocks on Earth. This you cannot explain by applying SR, it can only be explained by applying GR.
 

Related to Help wanted with an explanation

1. What is "Help wanted with an explanation" about?

"Help wanted with an explanation" is a phrase commonly used in job postings or advertisements. It indicates that the hiring company is looking for someone who can provide a clear and thorough explanation for a particular task or job role.

2. What skills are required for "Help wanted with an explanation"?

The skills required for "Help wanted with an explanation" may vary depending on the specific task or job role. Generally, strong communication, critical thinking, and problem-solving skills are important for providing clear explanations. Additionally, knowledge and expertise in the subject matter may also be required.

3. How do I provide a good explanation for "Help wanted with an explanation"?

To provide a good explanation for "Help wanted with an explanation", it is important to first understand the task or job role thoroughly. Then, use clear and concise language to explain the process, steps, or reasoning behind the task. Consider the audience and their level of understanding, and use examples or visuals if necessary.

4. Can I use different methods to explain for "Help wanted with an explanation"?

Yes, different methods can be used to explain for "Help wanted with an explanation", depending on the task or job role. Some common methods include written instructions, verbal explanations, diagrams or flowcharts, and demonstrations. The most effective method will depend on the audience and the complexity of the task.

5. How can "Help wanted with an explanation" benefit a company or organization?

"Help wanted with an explanation" can benefit a company or organization in several ways. It can ensure that tasks are completed accurately and efficiently, leading to increased productivity. It can also improve communication and understanding among team members, leading to a more cohesive work environment. Additionally, clear explanations can help prevent mistakes and misunderstandings, leading to better overall results.

Similar threads

  • Special and General Relativity
2
Replies
44
Views
480
  • Special and General Relativity
2
Replies
54
Views
1K
  • Special and General Relativity
2
Replies
61
Views
4K
  • Special and General Relativity
Replies
16
Views
872
  • Special and General Relativity
3
Replies
70
Views
4K
  • Special and General Relativity
2
Replies
45
Views
3K
  • Special and General Relativity
2
Replies
36
Views
2K
  • Special and General Relativity
3
Replies
95
Views
5K
  • Special and General Relativity
2
Replies
40
Views
1K
  • Special and General Relativity
Replies
26
Views
2K
Back
Top