Is time universal? NO (and its proof)

[Muslim]

Hello Billy T,

My only comment. I have not advocated universal time. However, I have said, and do say, that if in a common frame an event is simultaneous to two or more observers, that when viewed from other frames they appear to not be simultaneous, that that is merely a perception and in no manner has altered the fact of simultaneity of the events.

Someone correct me if I'm wrong, but it appears you're using the same misapplication of the Lorenz transform which leads to the "twin paradox" as the justification for statements like:

Note that their “non-simultaneous deaths” is not due to the time for light to travel to any observer - I had the two (now dead) stationary observers stand right next to the bombs when they exploded. If a third stationary observer, is standing mid way between the two that get killed, that third observer would observer them die at different times. (The two delays for him to see them die, due to finite speed of light, are equal.)

you might try doing a little math along with something like this. Also, "observer" is a noun, not a verb. At any rate, the relativity of simultaneity is still in respect to two (or three) observers, even though you claim it's not then ramble incoherently off onto some other tangent.

None of this is a compelling argument against the possibility that our universe is inherently discrete-time.

 

[MacM]

Someone correct me if I'm wrong, but it appears you're using the same misapplication of the Lorenz transform which leads to the "twin paradox" as the justification for statements like:



you might try doing a little math along with something like this. Also, "observer" is a noun, not a verb. At any rate, the relativity of simultaneity is still in respect to two (or three) observers, even though you claim it's not then ramble incoherently off onto some other tangent.

None of this is a compelling argument against the possibility that our universe is inherently discrete-time.

Just a little confusing since you posted a quote by me, showing my name but then quotes by Billy T without his name. Those were not my statements.

 

[Billy T]

...None of this is a compelling argument against the possibility that our universe is inherently discrete-time.

You appear to be relatively new here and I doubt if you have read the 57 prior pages (I certainly would not, if new) I think there is all the math you want in Pete's table. There was little math posted here by me and certainly no use of the Lorenz transform.

The first post of this thread was a way to show without complication or math that events in one frame that are simulatneous are not simulatneous in another.
Briefly a flash, equally distant from two small photo sensor triggered bombs, all mounted on outside of fast moving train, cause bombs to explode simulatneously (for train observers).

Two of the ground observers in long line of shoulder-to-shoulder observers standing beside the tracks (Noses just grazed by the passing bomb) are killed, but not simulatneously for groung based observers as the bomb at end of train advance to meet light front traveling towards it but the bomb at front travels further down the tracks while the light is catching up to it. I.e. for the gound observers the blast at the rear of the train proceeds the one at the front. (not simultaneous blasts, as blast were for train observers)

MacM believes: "that if in a common frame an event is simultaneous to two or more observers, that when viewed from other frames they appear to not be simultaneous, that that is merely a perception and in no manner has altered the fact of simultaneity of the events."

By having the multitude of observers, all with noses pressed against the passing bombs, there is no way that the fact that the one killed by the end of train bomb died before the one killed by the front of train bomb can be blaimed on apperances, preception delays, etc. That was the point of this thread. MacM did not get it.

I.e.As you can see, from his post, it failed to show MacM the error of his way, but at least he no longer agrues that all clocks in two different frames can both keep proper time and stay sychronized with those in another frame.

Instead, he says he does not advocate "universal time" but he does believe that all the clocks in frame A and frame B can tick sychronously with others in their frame and that two of them, one in frame A and the other in Frame B could tick at the same time, expecially if they were adjacent when they made this tick. (If you think about it this is the same as "universal time") I.e he does not advacate it, he only believes in it instead SRT.

PS if you are want to argue either for or against the "discrete" nature of time, I suggest you start a new thread. This one is about the exists, or not, of universal time.

 

[2inquisitive]

By Billy T:


"Two of the ground observers in long line of shoulder-to-shoulder observers standing beside the tracks (Noses just grazed by the passing bomb) are killed, but not simulatneously for groung based observers as the bomb at end of train advance to meet light front traveling towards it but the bomb at front travels further down the tracks while the light is catching up to it. I.e. for the gound observers the blast at the rear of the train proceeds the one at the front. (not simultaneous blasts, as blast were for train observers)"
==============================================================

According to WHICH of the ground observers? The observer killed by the bomb at the front of the train will die before the flash of the rear bomb ever reaches him. According to him, or another observer standing shoulder to shoulder beside him, the bomb at the front exploded before the rear bomb. The sequence of events is dependent on the travel speed of light, which is not even 'c' in your example. By stating the rear bomb explodes before the front bomb according to ALL ground observers, you are implying a 'universal' time for those observers in which the information from each of the two explosions travels instantaneously to all ground observers, regardless of their distance from the events. Don't forget, your train was a 'long' train.

For the bombs to explode simultaneously for 'train observers', all would have to be located in the exact center between the two bombs. An observer located at one end or the other of the train would see the bomb nearest him explode first, also.

Sorry, Billy T, but you messed up in your personal reworking of the classic simultaneity train example.

 

[MacM]

Muslim,

Welcome.

2Inquisitive's view is correct and Billy T unfortunately is being his usual incorrect self.

Billy has a bad habit of making up his own version of what I believe and/or mis-stating my view or posts.

My position is simple. If for an observer in the same frame and midway between the location of the two blasts sees them as simultaneous then they were defacto simultaneous in a universal way. Anyother observer frame or location will see an altered sequence due to time dilation and/or information delay at the speed of light.

However when I see the blasts does not alter when the blast actually occured, no more than claiming a hammer of a carpenter actually hits the nail when I hear it, or when I see it , not instead of when he (locally) struck the nail.

When he actually strikes the nail is not changed by when I hear or see the nail struck. Billy T has this stupid view that events don't actually occur until you see them occur.

 

[Pete]

Hi 2inquisitive,
As you suggest, each observer must know how far they are from each explosion if they are to determine whether the explosions were simultaneous or not.

If an observer records when they received information about an event, and they also know how far away the event occurred and how fast the information travelled to them, then they can determine when the event actually occurred, right?


This is assumed knowledge, which I think that BillyT is well aware of and assumes that everyone else is too. Because it's obvious, right?

So...

The sequence of events is dependent on the travel speed of light, which is not even 'c' in your example.

By the "sequence of events", we're talking not about the sequence in which information about events arrives at an observer, but the sequence in which the events occurred.

By stating the rear bomb explodes before the front bomb according to ALL ground observers, you are implying a 'universal' time for those observers in which the information from each of the two explosions travels instantaneously to all ground observers...

A time standard common to all ground observers is certainly assumed.
No instantaneous communication is assumed. It is assumed that each observer can determine when each explosion occurred by substracting information travel time appropriately.

 

[2inquisitive]

by Pete:

"Hi 2inquisitive,
As you suggest, each observer must know how far they are from each explosion if they are to determine whether the explosions were simultaneous or not.

If an observer records when they received information about an event, and they also know how far away the event occurred and how fast the information travelled to them, then they can determine when the event actually occurred, right?"
--------------------------------------------------------------------------------

How do they determine EXACTLY how far they were from moving explosion? Exactly how fast DID the information travel to them, Pete?
================================================================

by Pete:

"By the "sequence of events", we're talking not about the sequence in which information about events arrives at an observer, but the sequence in which the events occurred."
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I understood that events have to be 'observed' by the observer in each different frame of reference, leading to the disagreement among observers. The central observer on the train 'assumes' he and the train are stationary. He therefore assumes the travel time of the signal to two equi-distant bombs will be identical, even though the signal is travelling throught the atmosphere on the outside of the train in Billy T's example. Be careful here, Pete. Is the speed of light invariant to all observers when the light is travelling through a medium?

 

[Pete]

How do they determine EXACTLY how far they were from moving explosion?

Does it matter how? Or do you suggest that this distance is impossible to determine, or that it's ambiguous?

Perhaps after the explosions, the observer sets their trip meter and drives (relatively slowly) to the blast zone.

Perhaps the ground observer are standing on a long measuring tape. Each observer may note their own position on the tape and the position on the tape of the dead bodies.

Exactly how fast DID the information travel to them, Pete?

Does it matter?
The information could arrive by light (the observer sees the explosion), by sound (the observer hears the explosion, or feels the vibrations), by courier, or by carrier pigeon, or all the above.

 

[Billy T]

...According to WHICH of the ground observers? ...

You do not quite get the picture. The "observers" are just the stop buttons* of stop watches (designed to survive the micro blasts if you don't like thought experiments) all of which have been sychronized. (Even MacM will allow all the clocks in one frame to be sychronized, so I will not go into the details of the many ways this can be done.) I.e. There are no distant observers who see the light flash of the bombs with propagation delays as you appear to be assuming.

Sorry, if my speaking of observer noses being grazed by passing bombs confused you. Any other objecions you wish to raise, I bet can be answere by: "Make the train longer and / or travel faster (greater % of c)."
_______________________________
*this too discussed in prior post of this thread.

 

[MacM]

There are no distant observers who see the light flash of the bombs with propagation delays as you appear to be assuming.

What??? Quite a feat. You have just claimed instantaneous knowledge over distance. I didn't know we were discussing particle entanglement now.

I guess that is why I never "got it", I always believed that it took a certain amount of time for sound and/or light to travel from an event to some remote observer standing all along the length of the train.

 

[Billy T]

...Billy has a bad habit of making up his own version of what I believe and/or mis-stating my view or posts.

I used your statement in direct quote. My whole point is exactly the opposite of what you state (without any quote of me) as my position below:

...Billy T has this stupid view that events don't actually occur until you see them occur.

NEVER have I suggested that simultaneity is to be judged by when the light sound of a distant hammer is heard or any such nonsense. I insist in many posts, this one included, that the two clocks, in different frames must be adjacent to be simply and directly compared. (No math needed. -No SRT needed.) Fact that events which are simultaneous in one frame are not simultaneous in another is predicted by SRT, but not a consequences of SRT, as this simple example shows.

I have no objection to using the equations of SRT to compare separated ones in different frames, but know you do, so I set this example up to compare only collocated (extremely close at least) observers as I know you would try (As you are now) to confuse the issue by speaking of "perception delays" etc.

 

[MacM]

I used your statement in direct quote. My whole point is exactly the opposite of what you state (without any quote of me) as my position below:


NEVER have I suggested that simultaneity is to be judged by when the light sound of a distant hammer is heard or any such nonsense. I insist in many posts, this one included, that the two clocks, in different frames must be adjacent to be simply and directly compared. (No math needed. -No SRT needed.) Fact that events which are simultaneous in one frame are not simultaneous in another is predicted by SRT, but not a consequences of SRT, as this simple example shows.

I have no objection to using the equations of SRT to compare separated ones in different frames, but know you do, so I set this example up to compare only collocated (extremely close at least) observers as I know you would try (As you are now) to confuse the issue by speaking of "perception delays" etc.

Unadultrated babble, inconsistant with posted information.

 

[Billy T]

...even though the signal is travelling through the atmosphere on the outside of the train in Billy T's example. ...

Some details in thought experiments are not generally stated, especially if they are of no consequence. If you insist, I now tell more details:

The two bomb are the end caps of an evacuated tube and the flash bulb that triggers them is inside that tube at the middle of it.

Furthermore the train is very long, and it takes an hour for the light to travel from the centrally located flash bulb to reach the bombs (train time) exploding them simultaneously (train observers).

During this hour the train's speed is such that the light traveling along the track (ground observers) from the post on ground where the flash bulb went off to the front of the train requires 10% more time (ground clocks) to reach the front of train bomb than to reach the bomb at the rear of the train. (Lets say, just to be clear, that for ground clocks, the rear bomb explodes 5 minutes before the one at the front of the train.)

Also note that the stop watch “observers with noses being grazed by the bomb“, do experience only a 3 milliseconds delay before they stop recording the passage of time. (all effects included, i.e. inertia in their switches, expansion of the explosion gasses, etc.)

IS THE POINT CLEAR NOW?

I. E. Without SRT, without math, I have proven that events simultaneous in one frame need not be simultaneous in another. Not proven, but true, is that this is a general fact.

Later by Edit: I will not reply to MacM's latest directly but do predict he will continue to insist, despite this proof, that the predicted lack of simultanity inherent in SRT equations is just more proof that SRT is wrong and that his view is correct.

That is why this thread was dead for months. - Not worth more effort to demonstate to him that the math of SRT has nothing to do with the physical fact that simultanity is frame dependent, not universal as he claims.

 

[2inquisitive]

by Pete:

"Hi 2inquisitive,
As you suggest, each observer must know how far they are from each explosion if they are to determine whether the explosions were simultaneous or not.

If an observer records when they received information about an event, and they also know how far away the event occurred and how fast the information travelled to them, then they can determine when the event actually occurred, right?"
--------------------------------------------------------------------------------

2inq:
How do they determine EXACTLY how far they were from moving explosion?
===============================================================

"by Pete again:
Does it matter how? Or do you suggest that this distance is impossible to determine, or that it's ambiguous?"
--------------------------------------------------------------------------------

I suggest the location of the explosion is frame dependent. The train observer will not agree with the ground observer of the exact location. According to STR, the train is length contracted in the ground observer's frame. The distance to the explosion point is less than the stationary length of the train would indicate. Light signals from this 'closer' location would reach the ground observer more quickly, correct? According to the train observer, the distance between two points on the ground is length contracted. He can transverse a greater distance along the ground than would be possible if not for the contraction, according to his clock and ruler. So, exactly where does the explosion occur? You mentioned a 'bomb crater'. Assume the distance from the 'flash bulb' in the center of the train to the bomb located at the front of the train is measured at 20,000 feet when measured on a stationary train before the experiment began. Also assume the central ground observer has placed a marker 20,000 feet from his observing location further up the train rails.

Now, let the train pass the ground observer at 10% the speed of light, setting off the flash bulb exactly at the point the bulb passes him. According to the ground observer, the bomb is located 19,900 feet from him when it explodes because the train is contracted in his frame. The bomb explodes before it reaches the marker he placed.
According to the train observer, the distance between ground observer and the marker is contracted, however the distance to the bomb at the front of the train is not. When the light from the flash bulb reaches the bomb, the bomb will be 100 feet past the ground marker.

Where will the crater on the ground be located in relation to the marker?

 

[Pete]

Hi 2inq,
I like your example. Here's my analysis of the situation according to special relativity:

So, exactly where does the explosion occur? You mentioned a 'bomb crater'. Assume the distance from the 'flash bulb' in the center of the train to the bomb located at the front of the train is measured at 20,000 feet when measured on a stationary train before the experiment began. Also assume the central ground observer has placed a marker 20,000 feet from his observing location further up the train rails.

Now, let the train pass the ground observer at 10% the speed of light, setting off the flash bulb exactly at the point the bulb passes him. According to the ground observer, the bomb is located 19,900 feet from him when it explodes because the train is contracted in his frame. The bomb explodes before it reaches the marker he placed.

The bomb is located 19,900 feet from him when the flash is triggered, but it doesn't explode then... the bomb explodes when light from the flash reaches it, right?

In the ground frame, the light from the flash takes 0.0000225 seconds to reach the bomb. In this time the train moves a further 2211 feet, and the bomb explodes 22111 feet from the ground observer in the ground frame. The bomb explodes 2111 feet past the marker.

According to the train observer, the distance between ground observer and the marker is contracted, however the distance to the bomb at the front of the train is not. When the light from the flash bulb reaches the bomb, the bomb will be 100 feet past the ground marker.

At the time the flash goes off the bomb will be 100 feet past the marker (or the marker will be 100 feet past the bomb, since in this frame, the bomb is stationary and the marker is moving). But the light from the flash doesn't reach the bomb until 0.0000203 seconds later. The marker has moved a further 2000 feet in this time, so in the train frame the bomb explodes 2100 feet past the marker.

Where will the crater on the ground be located in relation to the marker?

SR predicts that it will be 2111 feet past the marker in the ground frame, and 2100 feet past the marker in the train frame... As you'd expect, since the proper distance of 2111 feet should be contracted in the train frame by exactly that amount.

 

[2inquisitive]

Well, Pete, Billy T was suggesting to eliminate the time delay of a signal reaching the central observer, so that why I stated the bomb explodes at that location 19,900 feet form the observer. But your example using time delay of the signal reaching the central observers is fine with me.

Light travels at approximately 983 feet per microsecond. In 22.5 microseconds, light will travel 22,117.5 feet. At 10% the speed of light, the train will travel 2,211.75 feet, or 2212 feet, about the same as your 2211 feet calculation. In 20.3 microseconds, light will travel 19954.9 feet. At 10% the speed of light, the train will travel 1995.49 feet, rounded off to 1996 feet.

According to the ground observer, the train will pass the marker and the bomb will explode 2112 feet on the opposite side of the marker from him, 22,112 feet from his location. Mark the bomb crater at this point, according to calculations from the ground observer's position.

Now for the train observer's calculations. Due to the contracted distance between ground observer and marker in this train observer's frame, the bomb will be 100 feet past the marker when the flash is ignited, as you said. The bomb will explode after the bomb has travelled another 1996 feet, for a total of 2096 feet past the marker. Mark this bomb crater with a different colored marker from the rest. This crater will be located 16 feet from the other crater. A single bomb created two different craters. SR predicts the proper distance of 2112 feet should be contracted by about 10.5 feet, not 16, in the train's frame. That is also about a 50% error. Where did I go wrong?

 

[Pete]

Well, Pete, Billy T was suggesting to eliminate the time delay of a signal reaching the central observer...

I think there is a communication problem between you and Billy.

Where did I go wrong?

Hi 2inq,
It looks like you've tried to use numbers rounded to three significant figures to reach six significant figure conclusions. This is an easy mistake to make!

In 22.5 microseconds, light will travel 22,117.5 feet. At 10% the speed of light, the train will travel 2,211.75 feet, or 2212 feet, about the same as your 2211 feet calculation.

The 22.5 microseconds is rounded. If you calculate the precise figure (22.49322), you'll find that in the time it takes the flash to reach the bomb the train travels 2211.08 feet.

In 20.3 microseconds, light will travel 19954.9 feet. At 10% the speed of light, the train will travel 1995.49 feet, rounded off to 1996 feet.

Again, the 20.3 microseconds is rounded. If you calculate it properly, you'll find that the travel is exactly a tenth of the train length - 2000 feet.

According to the ground observer, the train will pass the marker and the bomb will explode 2112 feet on the opposite side of the marker from him, 22,112 feet from his location. Mark the bomb crater at this point, according to calculations from the ground observer's position.

I notice you've also used the rounded 100ft figure in here. If we're doing things to more than three significant figures, we need to be more precise.
The 20000ft distance is contracted by 100.25 feet.
According to the ground observer, the crater should be 2211.08 - 100.25 = 2110.83 feet past the marker, 22,110.83 feet from his position.

Now for the train observer's calculations. Due to the contracted distance between ground observer and marker in this train observer's frame, the bomb will be 100 feet past the marker when the flash is ignited, as you said. The bomb will explode after the bomb has travelled another 1996 feet, for a total of 2096 feet past the marker. Mark this bomb crater with a different colored marker from the rest.

Putting in the corrected figures (100.25 feet and 2000 feet), we find that according to the train observer, the crater should be 2100.25 feet past the marker.

This crater will be located 16 feet from the other crater. A single bomb created two different craters.

The ground observer's crater is 2110.83 feet from the marker in the ground frame. In the train frame, this distance is contracted to 2100.25 feet.
So in the train frame, the "two craters" are in the same place - both are 2100.25 feet from the marker.

 

[2inquisitive]

I see, thanks Pete. I used your posted times, i.e. .0000225 = 22.5 microseconds.

by Pete:
"The ground observer's crater is 2110.83 feet from the marker in the ground frame. In the train frame, this distance is contracted to 2100.25 feet.
So in the train frame, the "two craters" are in the same place - both are 2100.25 feet from the marker."
===============================================================

Yes, but in the proper frame, the ground frame in which the craters were marked, the 'true' distance is 2110.83 from the marker. The reason the train observer measured
FEWER numbers of meters was because his clock was running slower than the ground clock. He could cover a greater distance in one of his 'ticks', resulting in LONGER meters compared with the ground meter. Longer meters result in fewer numbers of them in a certain proper distance, the 2110.83 meters. Remember this arguement, hehe. It is my way of looking at the situation, it seems more logical to me. And, yes, I
know I can't convince others to see it this way. I know clocks beat at different rates in different reference frames. I believe the 'length contraction' is not real, but is a direct result of the slower clock in the train's frame.

 

[2inquisitive]

I see Pete is now offline, so I will go ahead and do my follow-up post.

We have established the crater will be in the SAME location in both reference frames.
The 'calculated' difference between reference frames was due to the slower beating clock in the train frame, resulting in using different units of measurement.

If the crater is in the same physical location in both frames, how can the light signal of the explosion arrive at different 'times' for each of the central observers? It can't. The difference in the two frames is the tick rate of the clocks, they record time differently.

Now, synchronize the clock on the train with the clock on the ground, in other words speed up the train clock's tick rate. The same thing that is done with GPS satellite clocks. The explosion is now synchronized in both frames of reference, both observers will agree when, and at what distance, the explosion occured. The explosion will occur simultaneously in both frames of reference, after the forward travel of the train observer is factored out. There is no 'true' length contraction, only differences in clock tick rates between frames.

 

[Billy T]

...Billy T was suggesting to eliminate the time delay of a signal reaching the central observer,...

No No NO I was not. There is no "central observer." Read what I wrote. See first post of thread. etc. Again:
All along the track, are stopwatch "observers" so close together than when the bombs explode, several are less than 1mm for the exploding bomb. Time of flight from bomb to stop watch closest to the bomb is entirely negligible compared to the hour (train time) required for the light to travel from the flash bulb to either bomb (They explode simultaneously for train observers)

For ground clocks, all of which are of course synchronized, the bomb at the rear of train exploded 5 minutes before the one at the front of the train. All this discussion about "central observers" bomb craters etc. is an irrelevant waste of time. Think of the "bombs" as the smallest fire cracker ever made! Observers are stop watches. "shoulder to shoulder" was my picturesk way to say that the stopwatches are several to the millimeter along the track. etc. This is a thought experiment. Do a little thinking (as well as better reading.) Pete is right - a huge communication problem.

The point is clear!
The explosions were simultaneous for train observers and not for ground observers (Read that as for ground clock's time and train clock's time.)