- #121
matheinste
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m.starkov said:
Aircraft circling the Earth are continually accelerating.
Matheinste.
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Click For Summary
The discussion centers on the concept of time and its perceived "speed," questioning whether it can be quantified meaningfully. While Newton viewed time as constant, Einstein's theories suggest that time is relative, affected by motion and gravity, leading to varying perceptions of time across different frames of reference. Participants argue that asking for the "speed of time" is inherently flawed, with many concluding it can only be described as "one second per second." They also explore the analogy of moving through spacetime, where an object's speed through time decreases as its speed through space increases. Ultimately, the conversation highlights the complexities and misunderstandings surrounding the nature of time in physics.
Aircraft circling the Earth are continually accelerating.
Matheinste.
- #122
m.starkov
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Gigan said:
The Keyword is "linear".
I'm not so sure we can use this formula in this experiment.
Because the movement is not linear.
The major sense of this experiment is that clocks is always under acceleration.
Your formula doesn't "feel" that acceleration.
Dalespam recommends to use always Lorentz transformation formula.
But I'm not strong enough in Math to handle it.
May be someone else can do it.
It will be very good if we can reproduce time dilation effect just at home using ventilator and china's watches.
Yes, temperature will be different and also may be some electrostatic charge can affect results.
But we can reduce these conditions as we can and... since this is not for public this is just for ourselves. If calculated value will be just aprox. as actual - it will be very nice!
- #123
m.starkov
- 35
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matheinste said:
During the flight it suffers only centripetal acceleration which is not so high.
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- #124
matheinste
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m.starkov said:
Circular motion, with or without gravity is accelerated motion. An object following a curved path is accelerating towards the instantaneous center of curvature of that path. In the case of circular motion the acceleration is at all times towards the center of the circle. The acceleration is real.
What would be the point of the aircraft circling the Earth if the only effective accelerations were at landing and take off?
Matheinste.
- #125
Ich
Science Advisor
- 1,931
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Of course you can. It is completely general (in flat spacetime). Have a look at http://www.fourmilab.ch/etexts/einstein/specrel/www/" .
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- #126
Dale
Mentor
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I think you can handle it. You did very well previously, especially considering that I gave some bad advice. Plus, you have access to some math software (Maple?). Just follow the steps:m.starkov said:
1) Pick some inertial frame.
2) Write down the parametric form of the path ( t(r), x(r), y(r), z(r) ) in terms of some arbitrary parameter r.
3) Optionally, (not necessary, will not affect the results, but you seem interested in doing it) use the Lorentz transform to find the path, or worldline, in any other inertial frame. The parameter, r, is unchanged.
4) Find the derivatives: dt/dr, dx/dr, dy/dr, dz/dr.
5) Evaluate the integral form of the metric:
\tau = \int<br /> \sqrt{\left(\frac{dt}{dr}\right)^2-\left(\frac{dx}{c \, dr}\right)^<br /> 2-\left(\frac{dy}{c \, dr}\right)^<br /> 2-\left(\frac{dz}{c \, dr}\right)^<br /> 2} \, dr
- #127
ibcnunabit
- 68
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monty37 said:
I understand the sense of the question, but within a given frame of reference, the question is meaningless. If time "sped up" or "slowed down", it would do so for everything in that frame, and would be indetectible. Also, speed is a concept that's derived from time, so to try to build it into time somehow would be faulty reasoning.
AND YET:
Physicists talk all the time about time speeding up or slowing down in one frame relative to another. You need the 2nd frame of reference to describe the other frame--but even then, that's only comparing to your own frame--it's not an absolute measure. It can be described as a proportion between the two, but that proportion would be unitless. It would be a constant like 1.2 or 0.7. The same would be true if a strong gravitational field were applied. Time would be "slower," but that change in the time stream would be indetectible to the entity upon which it was applied. Others, however, could conceivably detect it and measure relative to their own frame.
Cheers,
Mike from Shreveport
- #128
m.starkov
- 35
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DaleSpam said:
Well, finally I have managed to bring my brains together.
The major question for me for the moment: how Lorentz transformation formulas can help here?
AFAIK Lorentz transformation formulas can be used only for calculating Position and Time in another INERTIAL frame.
But my clocks frames are NOT inertial!
So I really can't understand how we can find TIME elapsed in not-inertial frame using only inertial-to-inertial transformations?
It is not in Math, I just can't get the principle...
Can somebody help me?
Dalespam?
- #129
Dale
Mentor
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Don't worry, this is a very common misconception (see Baez's http://math.ucr.edu/home/baez/physics/Relativity/SR/acceleration.html" ). Special relativity can easily handle accelerating objects, as long as you do the analysis in an inertial reference frame.m.starkov said:
In other words, don't forget that reference frames are nothing more than coordinate systems. There is never any requirement that you attach a coordinate system to every object, nor is there even a requirment that every coordinate system be attached to some object. In fact, the most generally useful reference frame, the center of mass frame, usually does not correspond to the rest frame of any single particle. The whole point of SR is that you can use any inertial reference frame to do your analysis, not that you need to attach a coordinate system to each object and re-do your analysis multiple times.
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- #130
RLS.Jr
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The speed of time is dependant on our speed of travel. Tell me how fast we are going and I will tell you the speed of our time.
- #131
DaveC426913
Gold Member
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OK, I'll bite.RLS.Jr said:
We're traveling at 93,141 mi/s relative to Milky Way galactic centre. What is the speed of our time?
- #132
GoodPR
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rls.jr your going to have to caculate the effect gravity has on this speed of time your speaking of also
- #133
Austin0
- 1,160
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monty37 said:
I propose that the speed of Time is c.
- #134
Count Iblis
- 1,858
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What is the speed of the x-coordinate? 
- #135
RLS.Jr
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DaveC426913 said:
Our speed is determined by adding all the vectors of travel in respect to the center of the Universe. Picking one vector (93,141 mi/s relative to Milky Way galactic centre) is as incomplete as determining Lance Armstrong's average speed of a 8 hour race by measuring distance in a random 60 second interval.
However, if you wanted the speed of our time based on 'Milky Way Galaxy Time', and added all vectors of travel (earth's rotation: ~900 mph; Earth's orbit: ~66,600 mph; our solar system's motion within the galaxy: ~41,666 mph) and came up with an instant vector (much less than 93,141 mi/s) then it could be done. Let's hypothetically say that at this second it is 84,000 mph relative to Milky Way galactic centre. Now, based on our relative speed compared to C, what is the speed of our time (in Milky Way terms)?
- #136
PaulRacer
- 44
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DaveC426913 said:
Half the speed of light? Now were talkin'. How do we know this? From my understanding time spans from infinity to zero. But 1 second will always be 1 second to the person experiencing it firsthand. Love this site.
- #137
DaveC426913
Gold Member
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RLS.Jr said:
Well, it was your question; presumably you had an answer.
I was just interested if your were going to propose an answer that was anything other than 'one second per second' - to which I would have cried foul.
- #138
RLS.Jr
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DaveC426913 said:
Fine, here is your answer:
Assuming we are traveling at 84,000 mph or 23.333333333 mps relative to the center of the Milky Way Galaxy...the speed of our time is 1.000000007844765 MGT (Milky Way Galaxy Time)
Of course, this is just a hypothetical 'instant'. If we put a vector model together tracking our constantly changing speed relative to the center of the Galaxy we would accurately know the speed of our time (relative to MGT). As it is, we can assume a relative time flux of 1-1.000000013249398 MGT.
This is derived by adding all known speed vectors between the Earth and the center of the Milky Way Galaxy, ~30.323888 mps, which illustrates the highest potential speed if all vectors aligned. With 0 mps being the lowest potential speed relative to the center of the Galaxy, the most accurate assessment of the speed of our time is:
1 - 1.000000013249398 MGT
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- #139
DaveC426913
Gold Member
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All that calculating for nothing...RLS.Jr said:
I picked 93,141 mi/s deliberately because it is half of c.
OK, I kind of thought that's what you were going to say.RLS.Jr said:
I don't know why you think our time would change because I've specified our speed relative to some arbitrary object. Note that I can give you my speed relative to multiple objects simultaneously. How are you going to calculate our speed of time if I give you speeds relative to six different galaxies?
Our time is 1s per s.
- #140
RLS.Jr
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DaveC426913 said:
Wasted math? Truth is never a waist.
Had you just posted the speed I would have given you a simple answer. However, using the center of our Galaxy as the reference point makes much more sense. That's why I modified your number to one that fits that reference point. Of course you can see that our speed in relation to the center of the Galaxy is in constant flux. Thus our 'speed of time' is in constant flux.
Thank you for bringing up the idea of multiple galaxies. The best reference point for determining our speed of time is the center of the universe. When we can measure all the speed vectors (actually only three more than I have already added..one of which is known)
then we can accurately determine the speed of our time and any galaxy. It would be in the unit of UT (Universal Time).
Finally, time is 1s/s only at a point of reference. If you consider yourself as the only real point of reference, then yes you are right. That does come across a little egocentric though.
- #141
matheinste
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Just some simple thoughts regarding clock rates.I am not sure if that is what is meant by the speed of time but I suppose it must be.
If our clocks, that is the clocks in the frame in which we are at rest,run at a rate other than 1 second per second then
1-- How would we know.
2-- If we knew to, what did we compare them with to arrive at this knowledge.
3-- If we know they are running at the wrong rate perhaps it would be best to set them at the correct rate, whatever that is.
4-- If a rate with which we compare our clocks, and everybody else compares theirs exists, should we call it universal time or absolute time.
Matheinste.
If our clocks, that is the clocks in the frame in which we are at rest,run at a rate other than 1 second per second then
1-- How would we know.
2-- If we knew to, what did we compare them with to arrive at this knowledge.
3-- If we know they are running at the wrong rate perhaps it would be best to set them at the correct rate, whatever that is.
4-- If a rate with which we compare our clocks, and everybody else compares theirs exists, should we call it universal time or absolute time.
Matheinste.
- #142
DaveC426913
Gold Member
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There was no truth in it. Your logic is flawed. See below:RLS.Jr said:
Had I just posted the speed it would have been nonsensical. Speed is meaningless without providing a reference point by which to measure it.RLS.Jr said:
The speed of our time does not change because of a reference to some far off point. As I point out, the reference point is arbitrary. I can observe a hundred or a thousand of them in less time than it takes to name them. Do you think my speed of time changes everytime I cast my eyes upon a different star?RLS.Jr said:
There is no such thing as the centre of the universe.RLS.Jr said:
You really need to read up on relativity. It would clear up many of the misconceptions you've stated above. All time and velocity is relative; there is no absolute.RLS.Jr said:
- #143
DaveC426913
Gold Member
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Just a clarification: By definition we are at rest in our own frame, as are all clocks in our frame.matheinste said:
- #144
matheinste
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DaveC426913 said:
Yes. What I really should have said was a clock carried with us, which amounts to the same thing.
Matheinste.
- #145
scott haig
- 5
- 0
I can see getting a bit confused because of our language: we say "time is passing" etc.--but in the most basic (Newtonian) sense time is just a ratio of distance (a thing we measure) to speed. Nothing is moving when "time moves" and therefore there is no speed of time.
BUT
I've always wondered--along similar lines-- about the putative "speed" of gravity. (Have assumed it's c but don't remember/never knew why). I'm guessing that its something like this:as a distant mass moves the change in the gravitational force vector's direction does transmit information--which has to move at subluminal speeds to prevent problems with causation.
So the question I'd like to add here is this: why is the vector particle of gravitation so hard to sense? Aren't we "sensing" them when we observe tidal forces of, say, the moon? And couldn't a pretty easy experiment be done with large masses undergoing rapid accelleration (like a a satellite between Earth and moon) to time nearby gravitational effects relative to a light signal?
(sorry to branch off here but it seems the crowd on this thread would know)
svh
BUT
I've always wondered--along similar lines-- about the putative "speed" of gravity. (Have assumed it's c but don't remember/never knew why). I'm guessing that its something like this:as a distant mass moves the change in the gravitational force vector's direction does transmit information--which has to move at subluminal speeds to prevent problems with causation.
So the question I'd like to add here is this: why is the vector particle of gravitation so hard to sense? Aren't we "sensing" them when we observe tidal forces of, say, the moon? And couldn't a pretty easy experiment be done with large masses undergoing rapid accelleration (like a a satellite between Earth and moon) to time nearby gravitational effects relative to a light signal?
(sorry to branch off here but it seems the crowd on this thread would know)
svh
- #146
RLS.Jr
- 10
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matheinste said:
First, remember that as a primary reference point your time always runs at 1s/s. It's only when using an object traveling a different speed as the primary reference point that your time is either faster or slower than 1s/s (1s/s is always the clock speed of the primary reference point).
1-- We know that everything traveling at different speeds have different speeds of time (rates of clock speed). Since it makes more sense to have a standardized point of reference as a primary reference point than everyone using themselves. We can conclude that our clock speed is only 1s/s when our speed equals that of the primary reference point.
2-- When comparing time speeds in and around Earth (satellites, planes, the moon) , it would be best to use the Earth as the primary reference point and have units ET (Earth Time). Progressively more significant primary reference points would be the sun (SST-Solar System Time); the center of the Milky Way Galaxy (MGT); with the center of the universe as the best (UT) when all vectors of speed can be calculated.
3-- There is no wrong or right rate. Just more significant primary reference points when talking about two or more objects that have different velocities.
4-- UT or Universal Time (when we are able to calculate all the speed vectors) would be most significant when dealing with referencing objects outside our galaxy. For most practical purposes ET is adequate. Absolute time would only be a valid unit if we were able to determine that space had limits and what all the speed vectors from the center were.
Lastly, an example showing that it is less valid for each of us to use ourselves as primary points of reference:
If you are sitting in a seat. Are you motionless? What if that seat is on a train traveling
80 mph? You could still consider yourself as the primary point of reference and think that the Earth and everyone on it was traveling, but you can see the inherent problems with this point of view. It is more valid to use the Earth as the primary reference point and describe yourself as traveling 80 mph along it's surface.
- #147
RLS.Jr
- 10
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DaveC426913 said:
Ok, my logic is flawed? Let's see:
- If only a speed is given then the 'speed of time' difference can be calculated using 0 mps as the primary reference point (which is inherent in the statement). Is it nonsensical to say that you are in a rocket ship traveling 17580 mph?
- If your speed is constantly changing in relation to a primary reference point (e.g. center of the Milky Way Galaxy) then your speed of time is constantly changing in direct proportion. It is easier to see using the center of our solar system as the primary reference point. When the revolution of the Earth (~900 mph) aligns (is the same direction) with it's orbit around the sun, then you are traveling ~1800 mph faster than when it's traveling in the opposite direction of the orbit.
- Your speed of time is always experienced as 1s/s as you can only experience reality with yourself as the primary reference point. But in relation to every star you see in the sky, your speed of time is different. You said it yourself "All time and velocity is relative; there is no absolute".
- There is no center of the universe? Is there a center of your room? If there was a 'Big Bang' and mater/energy continues to spread outward in all directions, then there is a center. If fact, there is most likely a massive black hole at the center of the universe as there is at the centers of Galaxies.
- #148
Hyrage
- 8
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There should be a center to everything that exists.RLS.Jr said:
Time is created by existing things & doesn't exist; it's a perception and you can act and think faster than it.
- #149
DrGreg
Science Advisor
Gold Member
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No, in the same way that there is no point on the Earth's surface that is the centre of the Earth's surface.RLS.Jr said:
- #150
RLS.Jr
- 10
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DrGreg said:
Are you then saying that our Universe is two dimensional? Because there is most certainly a center of our three dimensional Earth.
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