- #1
DaleSpam said:Hi Skeptick,
Many people will not download .doc files or any other type of file that could contain a macro. I would recommend simply posting your comments directly rather than through a word file if you want a wider review.
By Ross Blenkinsop
Date 29 October 2007
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Time dilation
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Assumptions
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The speed of light is the same in all frames of reference and is C.
2 identical clocks located in a non accelerating frame of reference will keep exactly the same time.
2 identical clock located in a non accelerating frame of reference will be the same length, so long as they are oriented 180 degrees or 0 degrees in relation to each other.
A clock can be calibrated using the time taken for a photon to travel over a constant length.
The clocks in fig 1, fig 2 and fig 3 , fig 4 and fig 5 are all identical in the same frame of reference.
Fig 1
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Depicts a clock of length L
At one end there is a detector (red) at the other end there is a laser (green)
At the red end there is also a clock that is perfectly synchronised with a clock positioned at the green end.
When a photon leaves the laser located at green the clock at green stops. When the photon eventually arrives at red the clock located at red stops. The time difference between the two clocks is noted, say 1 second if the clock is 300,000,000 meters long.
The time taken for a photon to travel from green to red in fig 1 will be t = L/C where C is the speed of light, L is the length of the clock and t is time difference.
A third clock is calibrated off the time difference between the two clocks. This third clock shows the true time.
In fig 1, if L = 300,000,000 meters, C = the speed of light 300,000,000 m/s then the third clock will be calibrated to tick once every second. T = 1 = 300,000,000/300,000,000
Fig 2
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Now we have the same system of clocks within a moving frame of reference that is moving to the right at velocity V.
At some time the green laser will be located at point c and the red detector will be located at point a. At some time later the red detector will be located at point b and the green laser will be located at point d, so the entire system moves to the right.
The length of the clock will be L^ …L hat which will be contracted with respect to L as lengths contract in a moving frame of reference.
As time will be different in the moving frame of reference with respect to time in the stationary frame I will denote it a T^…T hat
From this the following analysis
Length L1 or the length from point a to point b ab = vt^
Length L2 or the length from point b to point c bc = ct^
L^ = L1 + L2
L^ = vt^ + ct^
L^ = t^(v + c)
L^/t^ = v + c
Equation 1 ….t^ = L^/(v + c)
From equation 1 as the velocity of the moving frame of reference increases the time taken decreases ie time goes by faster.
If the length L of the clock in a stationary frames of reference was 300,000,000 meters long then in the moving frame of reference as it will be contracted in length L ie L hat… it will be some value less than 300,000,000. Let's say v is 10,000 m/s then from the above. If v is small compared to C then the length L^ will be close to 300,000,000. As 10,000 m/s is way less than 300,000,000 Ill assume L^ is 300,000,000.
t^ = 300,000,000/(300,000,000 + 10,000)
t^ will be less than 1 and the third clock will be calibrated to tick at every say .99 seconds. The clock in the moving frame of reference is ticking faster than the stationary clock?
As is evident for any value of v, t^, time in the moving frame of reference will be less than T, time in the stationary frame of erefrence.
Fig 3
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Now we have the same system of clocks within a moving frame of reference that is moving to the right at velocity V.
At some time the green laser will be located at point a and the red detector will be located at point c. At some time later the red detector will be located at point d and the green laser will be located at point b, so the entire system moves to the right.
The length of the clock will be L^ same as in fig 2.
As time will be different in the moving frame of reference with respect to time in the stationary frame I will denote it a T^…T hat
From this the following analysis
The distance the photon travels until it strikes the detector is the length from the point a to d which is given by the length from point a to point b plus the length from b to c , plus the length from point c to d
ab = vt
bc = L^ - vt
cd = vt
and the length from a to d is equal to t^C
therefore
t^C = vt + L^ - vt + vt
t^C = vt + L^
using similar reasoning as fig 2
t^ = L^/(C-v)
Intuitively as the velocity increases , time increases.
If the length L of the clock in a stationary frames of reference was 300,000,000 meters long then in the moving frame of reference as it will be contracted in length L ie L hat… it will be some value less than 300,000,000. Let's say v is 10,000 m/s then from the above. If v is small compared to C then the length L^ will be close to 300,000,000. As 10,000 m/s is way less than 300,000,000 Ill assume L^ is 300,000,000.
t^ = 300,000,000/(300,000,000 - 10,000)
t^ will be greater than 1 and the third clock will be calibrated to tick at every say 1.01 seconds. The clock in the moving frame of reference is ticking slower than the stationary clock?
As is evident for any value of v, t^ will be greater than T in the stationary frame of reference.
Fig 4
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In Einstein’s classic experiment he proposed that time in a moving frame of reference slows down. In his experiment he used a clock identical to the clock in fig 1, 2 and 3. His analysis for this clock in a stationary frames of reference is the same analysis as is in fig 1.
Fig 5
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Einstein theorized if the clock depicted in Fig 4 was in a moving frame of reference then a photon emitted by the green laser would take the path as depicted in Fig 5 and eventually it would arrive at the red detector. Since the path taken by the photon in fig 5 is considerably longer than the path taken by the photon in fig4 he concluded that time in a moving frame of reference must slow down.
Conclusion
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From my analysis I propose the following conclusions:
The measurement of time is dependent on the orientation and direction of travel of the clock, therefore time is a vector not a scalar quantity.
Depending on the orientation and direction of travel of a clock in a frame of reference time may increase or decrease and therefore I conclude there is no absolute reference point for the measurement of time.
Applications
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This method of measurement may be used to determine if there is an ultimate frame of reference.
Einstein postulated that there was no experiment that could be conducted in a moving frame of reference (“MFR”) to determine if your are in a moving frame of reference. I conclude using this method you can determine if you are in a MFR.
Einstein postulated as you could not determine if your are in a MFR or not, by experiment, then the force due to gravity was identical to the force by acceleration. As I have demonstrated it is possible to determine if your are in a MFR and therefore the force due to gravity only may be the same as force from acceleration.
Probably. I'm just paranoid.robphy said:I wonder... are attachments uploaded to PF scanned for virii or other malware?
DaleSpam said:Probably. I'm just paranoid.
Skeptick said:FYI
You cannot catch a virus from a bitmap file .bmp
You can catch a virus from a word doc but only if you have macros enabled. This word doc does not use a macro so you can view it with macros disabled.
Also you can catch a virus from carney so be wary of them as well
robphy said:It's better to use standard web formats like .gif or .png or .jpg... which have better support for compression. 100kb is a lot for very simple graphics.
DaleSpam said:Probably. I'm just paranoid.
robphy said:I wonder... are attachments uploaded to PF scanned for virii or other malware?
JesseM said:The flaw is that you seem to be unaware of the relativity of simultaneity, which says that there is no frame-independent definition of what it means for clocks to be "synchronized"--if two clocks are synchronized in their own rest frame, they will be out-of-sync in a frame where they are moving. This is a natural consequence of the fact that each frame assumes light moves at c in that frame, so that clocks at rest in this frame can be synchronized using this assumption...if I am on board a rocket ship and I want to synchronize two clocks at the front and back of the ship, .
Skeptick said:If the clock at the green end stopped when a photon from the red end struck it then simultenatoiety may be a problen assuming this whole gizmo is traveling very fast but as the clock at the green end stops when a photon leaves the green end and the clock at the green end is as close as you like to the green end simutenaiety effects can be ignored.
No, this method won't synchronize them in any universal sense. Are you familiar with the concept of "limits" in calculus? In the limit as the speed of the two clocks relative to one another approaches zero, there will be some frame in which the velocity of both clocks is approaching zero as well (the rest frame of whichever clock is not being changed in the limit), and in this frame and this frame only your method will result in the clocks being arbitrarily close to being perfectly synchronized in the limit as their velocity relative to one another approaches zero. But in some other frame--say, a frame where the first clock is moving at 0.8c and the second clock is moved away from it at 0.800000000000000000000000000000000000000001c, they will not remain close to synchronized if they are given enough time to move some significant distance apart...in fact, if you move them a distance of L apart from one another, in this frame your method will result in them being out-of-sync by an amount that's arbitrarily close to the amount they'd be out-of-sync if you use the conventional Einstein synchronization method involving light-signals. I gave a proof of something basically identical in post #41 of this thread, where someone suggested that you could synchronize two clocks C1 and C2 at a fixed distance apart by moving a third clock C3 very slowly between them, with C1 and C2 set to read the same time as C3 at the moment C3 passed each one. Here's what I said there:Skeptick said:Sorry but I have thought of the synchronisation of the clocks. I would synchronise them thus:
I would place the two clocks as close together as possible. Depending on the physical construction of the clocks this means the actual timing mechnism could be only atoms apart. I would then synchronise the clocks thus ensuring the time difference between the two clocks was virtually zero, or the distnace between atoms divided by C. I would then move the clocks apart to their final positions. As they were synchronised before they were moved apart they will still be synchronised afterwards. All mopvements are as slow as you like say 0.00000000001 m/ 1 billion years.
Presumably you want C3 to move very slowly relative to C1/C2 so there is little difference in the time dilation factor between C3 and C1/C2, but the difference in time dilation factors cannot be eliminated entirely. Assume the distance between C1 and C2 in their rest frame is 10 light-second, and the velocity of C3 in their rest frame is v. In this case, in their frame it takes a time of 10/v seconds for C3 to move between the two clocks. But C3 is slowed down by a factor of [tex]\sqrt{1 - v^2/c^2}[/tex], so it advances forward by
[tex]\frac{10 \sqrt{1 - v^2/c^2}}{v}[/tex]
in that time. So, what's the difference between this, the time on C3 as it reaches C2, and the time that C1 reads at the same moment in this frame, namely 10/v? Well, it'd just be:
[tex]\frac{10(1 - \sqrt{1 - v^2/c^2})}{v}[/tex]
If we take the limit of this quantity as v approaches zero, it will work out to zero (use L'Hospital's rule along with the chain rule of calculus to prove this), which means C2 will get arbitrary close to being synchronized with C1 in this frame as the velocity of C3 becomes very slow compared to c.
But that's just for the C1/C2 rest frame; now consider what happens in another frame where C1 and C2 move at some nonzero velocity, say 0.6c, and C3 moves with some slightly different velocity (0.6c + v)--again, we're going to be taking the limit as v approaches zero. In this frame the distance between C1 and C2 is shrunk to 8 light-seconds.
So if C3 and C1 start at x=0 light-seconds at time t=0 seconds, C3's position as a function of time x(t) is:
x(t) = (0.6c + v)*t
And if C2 starts at x=8 l.s. at time t=0 s, C2's position as a function of time is:
x(t) = 0.6c*t + 8 l.s.
So to figure out when C3 catches up with C2, set them equal:
0.6c*t + vt = 0.6c*t + 8 l.s.
...and solving this for t gives t=(8 l.s.)/v. So, this is the time it takes for C3 to go from C1 to C2 in this frame. Now, since C1 is slowed down by a factor of 0.8 in this frame, it will have elapsed a time of (0.8)*(8 l.s.)/v in this time. And C3 is slowed down by a factor of [tex]\sqrt{1 - (0.6c + v)^2 /c^2}[/tex] in this frame, so it will have elapsed a time of:
[tex]\frac{\sqrt{1 - (0.6c + v)^2 /c^2} * 8 \, l.s.}{v}[/tex]
So, the difference between the reading of C1 and the reading of C3 at the moment C3 reaches C2 will be:
[tex]\frac{(0.8 - \sqrt{1 - (0.6c + v)^2 /c^2}) * 8 \, l.s.}{v}[/tex]
Now we want to know what this difference will approach in the limit as v approaches zero. Since both the numerator and the denominator of this fraction individually approach zero in the limit as v approaches zero, we can again use L'Hospital's rule, taking the derivative of both the top and bottom and seeing what the new fraction approaches in the limit as v approaches zero...to take the derivative of the numerator we must also use the chain rule again. This gives us the following complicated-looking fraction:
[tex]\frac{8 \, l.s. * [-(1/2) * (1 - (0.6c + v)^2 / c^2)^{-1/2} * (\frac{-1.2c - 2v}{c^2})]}{1}[/tex]
Which simplifies to:
[tex]\frac{8 \, l.s. * (\frac{0.6c + v}{c^2})}{\sqrt{1 - (0.6c + v)^2 / c^2}}[/tex]
And if we take the limit of this as v approaches zero, it just turns out to be:
[tex]\frac{8 \, l.s. * (\frac{0.6c}{c^2})}{0.8}[/tex]
Which is 6 seconds. So, even in the limit as the velocity of C3 relative to C1 and C2 gets arbitrarily small, this method will still leave C1 and C2 6 seconds out-of-sync in this frame (and you're free to imagine that this frame in which C1 and C2 move at 0.6c also happens to be the absolute rest frame of Lorentzian relativity). And not-so-coincidentally, it turns out that if you had synchronized C1 and C2 using the Einstein synchronization convention, they would also be 6 seconds out-of-sync in this frame. So again, this method is useless for absolute synchronization, all it does is to replicate the same type of synchronization as the Einstein convention, which will cause clocks that are in-sync in one frame to be out-of-sync in another (or, if you prefer, will cause clocks that are moving relative to the absolute rest frame to be absolutely out-of-sync).
Incidentally, if you don't trust my calculus, feel free to take the equation I gave earlier for the difference between the reading of C1 and C3 at the moment C3 reaches C2:
[tex]\frac{(0.8 - \sqrt{1 - (0.6c + v)^2 /c^2}) * 8 l.s.}{v}[/tex]
...and instead of taking limits, just plug in some very small v like v=0.000001c, you should end up with an answer very close to 6 seconds.
But if the velocity v of the clocks in the MFR is negligible, then the difference of L^ /(v+c) from L/c will be negligible too (because the Lorentz contraction will be negligible, and the difference between c and v+c will be negligible). To the degree there is any small difference, it will be exactly compensated for by the small Lorentz contraction, time dilation and lack of simultaneity between the two clocks, in exactly the right way to ensure that, if the green clock stops when the light leaves it and the red clock stops when the light arrives at it, then the difference in readings between the two stopped clocks will end up being precisely L/c.Skeptick said:In my scenario the speed of the MFR 10000 m/sec which is too slow for the effects of relativity to make a difference. Make the MFR's velocity as slow as you like 1 kilomteer per 1 million years if you like the maths remians the same. As the speed of the MFR is not relativisitic the effects of simutenaiety can be ignored the time diffrenece of the two clocks would be negligable.
The difference in simultaneity means that in the MCR, if the clock at the green end reads a time of T at the exact moment the light departs from the green end (the moment when the clock is stopped), then at that precise moment in the MCR the clock at the red end will read a time of T + vL/c^2, where L is the distance between the clocks in their rest frame and v is the speed of the two clocks in the MCR (this is assuming the clocks have been synchronized using a method that gives the same definition of 'synchronized' as the Einstein clock synchronization convention, which would include your proposal of synchronizing them at a common spot and moving them apart with an arbitrarily small relative velocity).Skeptick said:Secondly if you look at fig 1 I have a clock at the green end and a clock at the red end. As explained the clock at the green end stops when a phton leaves the green end.
If the clock at the green end stopped when a photon from the red end struck it then simultenatoiety may be a problen assuming this whole gizmo is traveling very fast but as the clock at the green end stops when a photon leaves the green end and the clock at the green end is as close as you like to the green end and the whole gizmo is traveling at the pace of a snail simutenaiety effects can be ignored.
I thought you were using the "MFR" to refer to the frame in which the two clocks are in motion, ie the frame where you calculated the time to be L^ /(v + c). If you intend the MFR to be the frame where the two clocks are at rest, then of course if the distance between the clocks is L and light moves at c in this frame, the time for the light to go from the green end to the red end will be L/c. But my analysis shows that if you analyze the situation from the point of view of the frame where the two clocks are in motion--whatever you want to call this frame--then even though the time measured in this frame will be L^ /(v+c), the difference in readings between the two clocks after they both stop will still be predicted to be L/c, because of the way the clocks are ticking slowly and the way the distance between them is less than L and the fact that they are out-of-sync in this frame.Skeptick said:from wikipedia
Length contraction, according to the special theory of relativity, which was formulated in the early twentieth century through the seminal work of Einstein, Poincaré and Lorentz, is the physical phenomenon of a decrease in length detected by an observer in objects that travel at any non-zero velocity relative to that observer
In my example the observer is in the MFR there is no relative movemenet hence no LC so that can be diregarded.
Again, I'm not entirely clear on what you mean the "MFR" to be--is it the clocks' own rest frame, or the frame in which they are in motion? Your figures 2-5 seem to be drawn from the perspective of a frame where the clocks are in motion, since they show the position of the green and red end being different at the moment the light departs the green end and the moment the light arrives at the red end.Skeptick said:The person in the MFR synchronises the clocks, runs the experiments as shown in fig 1, 2, 3, 4, 5
If by "external observer" you mean the observer in the frame where the clocks are moving, I've already shown that this observer will predict the difference in the two clocks' readings will be L/c (although the time as measured in this frame will be different from L/c).Skeptick said:In the experiment depicted by fig 2 an external observer would percieve time to speed up
In the experiment depicted by fig 3 an ext observer would percieve time to slow down
It depends what you mean by "synchronize"--you can synchronize them relative to a particular frame's definition of simultaneity (like the rest frame of the ship), but you can't synchronize them in any objective frame-independent sense. Every inertial reference frame in relativity has its own separate definition of simultaneity, so if the event of one clock reading 3:00 PM happens simultaneously with the event of another clock at a different position reading 3:00 PM in one frame (meaning that the clocks are synchronized in that frame), then these events are not simultaneous in all other frames--there might be some frame where the event of the first clock reading 3:00 PM was simultaneous with the event of the other clock reading 2:59 PM, for example. This is what is meant by "the relativity of simultaneity".Skeptick said:Ill attempt to clear up one problem at a time
I am in a space shipthat is moving, can I sunchronise two clocks in the spaceship Yes / No?
Time dilation refers to the slowing down of time as an object moves closer to the speed of light. This phenomenon is predicted by Einstein's theory of relativity and has been observed in experiments with high-speed particles.
Time dilation occurs because space and time are connected and can bend and stretch. As an object moves faster, space and time around it become distorted, causing time to move slower for that object compared to a stationary observer.
The "tick tick skeptick" experiment is a hypothetical thought experiment that involves two identical clocks, one stationary and one moving at a high speed. According to time dilation, the clock in motion would tick slower than the stationary clock, leading to a discrepancy in time when they are brought back together.
Yes, time dilation can be observed in everyday life, but the effects are extremely small at everyday speeds. However, GPS satellites, which move at high speeds, have to account for time dilation in order to maintain accurate time measurements.
Time dilation has significant implications in the field of physics, particularly in understanding the behavior of particles at high speeds. It also has practical applications in technologies such as GPS and particle accelerators. Additionally, time dilation challenges our traditional understanding of time as a constant and raises philosophical questions about the nature of reality.