(02-12-2017, 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 space-time 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 Home-wormhole (the one that never went anywhere) and exits the Distant-wormhole (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.

(02-12-2017, 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 ten-year 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.

(02-12-2017, 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 Beta-wormhole 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 AB-wormhole 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 AB-wormhole to Beta and travels ten years into the future. Bob takes the AG-wormhole 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.

OA Wish list:

- DNI

- Internal medical system

- A dormbot, because domestic chores suck!