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02102017, 03:17 AM
(This post was last modified: 02102017, 03:27 AM by Bear.)
I think the understood conversion is that the "zero date" is January 1 of 1970 (the unix epoch and also the first startofyear after the Tranquillity landing) being equivalent to Archimedes 1 of the year zero AT? This tool has it as the date of the moon landing, which makes for really awkward conversions I don't think most people would put up with at the changeover.
And then there's weird conventions about leap years. I wouldn't expect everybody to keep following Earth's particular exceptions to the 'regular' calendar. They'd switch to years of exactly 365 days sooner or later, but exactly when? 'AT day number' might be the only really universal measure.
Anyway there are thousands or billions of different calendars in use across the Terragen sphere. Furthermore, with the Wormhole network, there's only an approximate notion of simultenaeity. Two people can travel different routes from A to B, both experiencing less than a day of subjective time, and arrive years apart.
Given humanity's origin at Sol, the only monotonicallyincreasing measure of time for all locations in the Terragen sphere as a whole would be 'first light' at that location, or the time when the light emitted from Sol on 1 Archimedes AT 0 arrived at a particular location, minus the number of light years from Sol.
But this still does weird things to time when people travel 'instantaneously' via wormhole.
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(02102017, 03:17 AM)Bear Wrote: I think the understood conversion is that the "zero date" is January 1 of 1970 (the unix epoch and also the first startofyear after the Tranquillity landing) being equivalent to Archimedes 1 of the year zero AT? This tool has it as the date of the moon landing, which makes for really awkward conversions I don't think most people would put up with at the changeover.
This article discusses how the Tranquility Calendar works. It actually does start counting from the date of the moon landing. The calendar was adopted by the inhabitants of Luna who likely didn't much care what the inhabitants of Earth found awkward or not
(02102017, 03:17 AM)Bear Wrote: Anyway there are thousands or billions of different calendars in use across the Terragen sphere. Furthermore, with the Wormhole network, there's only an approximate notion of simultenaeity. Two people can travel different routes from A to B, both experiencing less than a day of subjective time, and arrive years apart.
A single standard of time is physically impossible over interstellar distances, even with wormholes. Also, because the wormhole nexus is organized to prevent time machine issues, I don't believe the situation you describe could actually occur. Also, OA wormholes (the stargates at least) take quite a lot longer than a day to transit.
You could have a situation where one person travels via engenerator and another takes a ship and therefore each has a radically different experience of the passage of time. But that would work as readily in flatspace as by traveling via a wormhole.
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(02102017, 03:17 AM)Bear Wrote: I think the understood conversion is that the "zero date" is January 1 of 1970 (the unix epoch and also the first startofyear after the Tranquillity landing) being equivalent to Archimedes 1 of the year zero AT? This tool has it as the date of the moon landing, which makes for really awkward conversions I don't think most people would put up with at the changeover.
Not quite. You are correct, it is for synchronisation. So you can basically enter java.util.Date and output it through the Tranquility Calendar.
Quote:And then there's weird conventions about leap years.
That of course, is debateable. Just enter any other rule you deem appropriate.
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Hmmm. On reflection you're right about travel times. Two people could leave, travel for the same length of subjective time, and arrive years apart  but only if the subjective time spent traveling were at least the same number of years. So they might meet up six years later, with one of them having 'skipped forward' three years relative to the other. On the 'first light' metric everybody always arrives after they left.
Even that, however, would indicate that someone is running their ends of the network right on the edge of Vissier Collapse  which seems like a bad idea.
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(02112017, 04:08 AM)Bear Wrote: Hmmm. On reflection you're right about travel times. Two people could leave, travel for the same length of subjective time, and arrive years apart  but only if the subjective time spent traveling were at least the same number of years. So they might meet up six years later, with one of them having 'skipped forward' three years relative to the other. On the 'first light' metric everybody always arrives after they left.
Even that, however, would indicate that someone is running their ends of the network right on the edge of Vissier Collapse  which seems like a bad idea.
I'm not really seeing how you're reaching this conclusion. Can you explain your reasoning please?
Thanks!
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02122017, 05:55 PM
(This post was last modified: 02122017, 06:03 PM by Bear.)
Okay...
A wormhole gets created. Then a linelayer takes one end of it and accelerates to some relativistic velocity where it traverses substantially less time (and more space) than the end that got left behind. Let's say it arrives 50 light years distant having traversed ten years less time than the end that stayed home. Now Alice can enter the end that was left behind, and emerge 10 years "earlier" but 50 light years away. Causality is not broken because neither spacetime location is within the other's light cone (ie, there's no way for Alice to send a signal from 50 light years away to arrive before she leaves, even if it's sent after her arrival which is ten years "before" she leaves.).
But there's absolutely no way for Alice to get back to the first wormhole mouth without giving up that ten years. She can either give it up by traversing the wormhole in the opposite direction (and arrive ten years after leaving) or travel via flat space (more than ten light years) or traverse some other wormhole. But if she traverses some other wormhole, that wormhole has to respect that tenyear constraint. Maybe there's a wormhole back to the origin that won't cost ten years, but the entry to that wormhole is guaranteed to be more than 1 light year distant from the one where she emerged, for every year less than ten.
So, if Alice and Bob both start from A, and Alice traverses a wormhole that advances time (arriving "before" she left) and Bob traverses a wormhole that retards time (arriving "after" he left) Bob and Alice are guaranteed to have arrived a number of light years apart equal to at least the sum of the difference in time. If both of them climb into ships and proceed to a third location, the earliest they could possibly meet would be after closing that distance, which will take them all the time gained and then some.
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02132017, 01:37 AM
(This post was last modified: 02132017, 05:27 AM by Rynn.)
(02122017, 05:55 PM)Bear Wrote: A wormhole gets created. Then a linelayer takes one end of it and accelerates to some relativistic velocity where it traverses substantially less time (and more space) than the end that got left behind. Let's say it arrives 50 light years distant having traversed ten years less time than the end that stayed home. Now Alice can enter the end that was left behind, and emerge 10 years "earlier" but 50 light years away. Causality is not broken because neither spacetime location is within the other's light cone (ie, there's no way for Alice to send a signal from 50 light years away to arrive before she leaves, even if it's sent after her arrival which is ten years "before" she leaves.).
This is a topic that always ties my brain in knots lol. I think you've made a mistake here; if Alice enters the Homewormhole (the one that never went anywhere) and exits the Distantwormhole (the one that traversed 50 light years in 40 subjective years) she will be ten years in the future but outside of her future light cone by 40 years.
Someone traveling from Distant to Home will travel 10 years into the past, but they can't violate causality because they are 50 years away at the speed of light. If they sent a transmission instantly it wouldn't arrive until 40 years after they left.
SIDE NOTE: It occurs to me you could have a lot of fun bouncing messages to your future self from different parts of the Nexus. I've just had an odd image of a man on his hundredth birthday simultaneously receiving a dozen happy birthday messages from distant star systems, sent by laser, from himself years previous whilst travelling.
(02122017, 05:55 PM)Bear Wrote: But there's absolutely no way for Alice to get back to the first wormhole mouth without giving up that ten years. She can either give it up by traversing the wormhole in the opposite direction (and arrive ten years after leaving) or travel via flat space (more than ten light years) or traverse some other wormhole. But if she traverses some other wormhole, that wormhole has to respect that tenyear constraint. Maybe there's a wormhole back to the origin that won't cost ten years, but the entry to that wormhole is guaranteed to be more than 1 light year distant from the one where she emerged, for every year less than ten.
If Alice travelled from Distant to Home she would go back in time ten years. There's no way for her to get back to Distant without giving up those ten years. If she goes back through the wormhole she travels ten years into the future, if she travels by spacecraft she will arrive more than fifty years later. There can't be any wormhole configuration that gets her back in less than ten years because then she would arrive before she left. The instant you arrange a set of OA wormholes into a Roman ring they collapse.
(02122017, 05:55 PM)Bear Wrote: So, if Alice and Bob both start from A, and Alice traverses a wormhole that advances time (arriving "before" she left) and Bob traverses a wormhole that retards time (arriving "after" he left) Bob and Alice are guaranteed to have arrived a number of light years apart equal to at least the sum of the difference in time. If both of them climb into ships and proceed to a third location, the earliest they could possibly meet would be after closing that distance, which will take them all the time gained and then some.
Lets imagine three systems arranged in a triangle; Alpha, Beta and Gamma. Alpha and Beta are 50 light years apart. At some point in the past Alpha created a wormhole pair and sent one to Beta at 0.6c. The Betawormhole arrives after 40 subjective years of travel, the crew clock says its only been 40 years and Alphans can traverse the wormhole to Beta 40 years after they sent it. The wormhole connects Alpha to Beta 10 years into the future, and Beta to Alpha 10 years into the past.
Also at some point in the past Gamma, which is also 50 light years from Alpha, created a wormhole pair and sent one to Alpha. The linelayer travelled at 0.6c and also took 40 subjective years to get there. A Gamman travelling to Alpha advances ten years into the future. If a Gamman then travelled to Beta through the ABwormhole they are now twenty years into the future. Therefore Beta and Gamma must be more than twenty light years away from each other.
Alice and Bob start at Alpha. Alice takes the ABwormhole to Beta and travels ten years into the future. Bob takes the AGwormhole to Gamma and travels ten years into the past. Lets say they intend to meet again without taking wormholes and they both have space craft capable of travelling at 0.6c. If they immediately set off towards each other the moment they step out of the wormholes they will meet each other in interstellar space four light years out from Beta, sixteen light years from Gamma, 16.66 years into the future from when they left Alpha according to a Calendar on Alpha. Subjectively it would have been 3.2 5.33 years for Alice and 12.8 21.33 years for Bob.
Bringing it back to the calendar if they left on the 1st of Archimedes 9000a.t. (according to the Alpha calender that they set their DNIs to) and the year they left was a leap year they'd meet again on the 11th of Imhotep 9016a.t. according to those still back on Alpha. Alice's calendar will read the 21st of Brahe 9003a.t. 13th of Darwin 9005a.t. and Bob's will say 27th of Jung 9012a.t. 6th of Einstein 9021a.t. All valid, all different, but no causality violations.
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(02122017, 05:55 PM)Bear Wrote: Okay...
A wormhole gets created. Then a linelayer takes one end of it and accelerates to some relativistic velocity where it traverses substantially less time (and more space) than the end that got left behind. Let's say it arrives 50 light years distant having traversed ten years less time than the end that stayed home. Now Alice can enter the end that was left behind, and emerge 10 years "earlier" but 50 light years away. Causality is not broken because neither spacetime location is within the other's light cone (ie, there's no way for Alice to send a signal from 50 light years away to arrive before she leaves, even if it's sent after her arrival which is ten years "before" she leaves.).
OK. OA wormholes/metric technology have limitations that would prevent this exact situation from coming up, but correct in principle.
(02122017, 05:55 PM)Bear Wrote: But there's absolutely no way for Alice to get back to the first wormhole mouth without giving up that ten years. She can either give it up by traversing the wormhole in the opposite direction (and arrive ten years after leaving) or travel via flat space (more than ten light years) or traverse some other wormhole.
Actually no. This isn't how wormholes work. The two frames of reference are both equally valid and independent of each other. While they may be years, decades, or eons apart in time within their own frames of reference, the wormhole connects those two points in both space and time in both directions. The only time that Alice with 'lose' in transiting the wormhole (in either direction) is the time it takes her to cross the distance within the wormhole itself. OA wormholes have internal transits measured in hundreds of AUs (if you count the entire structure of the wormhole). But for sake of our thought experiment that distance could be no more than the distance through a standard household doorway (ala Stargate SG1 more or less).
To put it another way, if Alice goes thru the WH to a point 50 lightyears away in distance and 40yrs away in time (taking 1 second to make the transit), spends a week there and then comes back through the wormhole  she will not be away from Earth for 10years, 1 week, and 2 seconds. She will be away for 1 week and 2 seconds. The 10 year differential between the two mouths of the wormhole doesn't have any effect on transits through the wormhole in either direction.
Since the 'constraint' you mention doesn't apply, it won't apply to the rest of your example either.
While different wormhole mouths can have a fair bit of time differential between them, the arrangement of the wormholes (such as is done in the Nexus  a treelike branching acyclic graph) can minimize or avoid this issue, as can moving wormohole mouths at lower speeds to reduce time dilation.
Attempting to create a time machine, either by moving a distant WH mouth back toward its origin or by setting up a network of wormholes will result in the destruction of the gateways (least stable first) to prevent a CTC from forming.
Moving to OA itself  linelayers are largely limited to speeds where time dilation is not really very significant (around .74c or so) since Lorentz contraction will cause WHs to destablize at higher speeds. This works out to time dilation that is equal to the distance crossed (50 lightyear trip takes 50yrs shiptime). While there is certainly some amount of differential between the mouths in this situation, it isn't very large. Note also that most linelayers can't start/stop instantly and so will take years or decades to speed up and slow down, further reducing the time dilation effect. And a lot of linelayers don't travel at the max possible speed.
Voidship linelayers can start/stop instantly and travel arbitrarily close to the speed of light  but because their interiors are 'at rest' in their frame of reference, no time dilation occurs inside them (a 50 ly trip will take 50yrs no matter how close to c the ship gets) and so there is not time differential between the two mouths. Voidship linelayers are extremely rare however.
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Drashner, I think we're in vehement agreement. Travel one way and gain ten years, travel the other way and lose ten years. Different places in spacetime are linked via wormhole with one metric and via flat space with another metric, and both linkages work subject to the same physics, in both directions. But there's no metric, and no combination of metrics (closed timelike curves) that would allow you to reach your own light cone at a speed less than c.
Rynn's example where two travelers take trips lasting 16.66 years according to the firstlight framework, but have subjectively experienced 3.2 and 12.8 years respectively, sounds correct to me. He's right, on further reflection, about the direction of the clock adjustment involved in traveling from the older to the younger end of the same wormhole.
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02132017, 04:34 AM
(This post was last modified: 02132017, 05:30 AM by Rynn.)
(02132017, 03:51 AM)Bear Wrote: Rynn's example where two travelers take trips lasting 16.66 years according to the firstlight framework, but have subjectively experienced 3.2 and 12.8 years respectively, sounds correct to me. He's right, on further reflection, about the direction of the clock adjustment involved in traveling from the older to the younger end of the same wormhole.
Working through it again I seemed to have made an error and stated the journey times as too short. I've edited my post and am pretty sure I'm correct now. I don't have access to anything useful like excel atm so this is all being worked out with pen, paper, calculator and brain. My working out for anyone to check:  Alice and Bob start in Alpha on the 1st of Archimedes 9000a.t.
 Bob travels to Gamma and from the perspective of Alpha has travelled back in time to 8990a.t.
 Bob sets off immediately towards Beta, a distance of 20 light years, at 0.6c. He experiences time dilation of 80% relative to the three systems and when he starts his journey his DNIcalendar says it's still 1st of Archimedes 9000a.t.
 Alice travels to Beta and from the perspective of Alpha has travelled forward in time to 9010a.t.
 Alice sets off immediately towards Gamma, a distance of 20 light years, at 0.6c. She experiences time dilation of 80% relative to the three systems and when she starts her journey her DNIcalendar says it's still 1st of Archimedes 9000a.t.
 At the point in time in which Alice sets off Bob has been travelling for 20 years from Alpha's perspective. At 0.6c he has travelled 12 light years. Due to relativity his calendar now reads 9016a.t.
 At this point Bob and Alice are now 8 light years apart, travelling towards each other at 0.6c.
 Given their speed and distance they meet up 4 light years from Beta. Bob has travelled a total distance of 16 light years in 26.66 years but due to relativity his calendar says that only 21.33 years have passed.
 Alice, having travelled 4 light years at 0.6c, has taken 6.66 years to reach Bob but due to dime dilation it feels like 5.33 years.
Interestingly (and probably obviously to anyone who doesn't find it hard to think about this) the sum total of their subjective journey time is equivalent to Bob's journey time as measured from any of the systems.
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