Jumplines and stellar movement

[isf]

For jumplines that are formed or enabled by the interaction between the gravity of stars, it seem plausible that the jumplines would have limited lifespans due to stellar movement.



I think that lifespans on the order of 1-10,000 years gives the most room for a varied and changing galaxy for space opera purposes. That's long enough for successive expansions and collapses of colonization and exploration.



If you are using Fred Brackin's jumpline model where they form more commonly between massive stars, the lines between massive stars may be more robust and longer lasting than smaller stars. Under this assumption, there could be useful hubs around black holes and A, B, and O stars that last considerably longer and have longer ranges than the more habitable F and G stars.

[ericthered]

is 10,000 years the right number? I found this chart of how the stars near earth are moving relative to us, and it does seems that 10k years is a meaningful amount of time in the relative motion of stars, if just a bit on the short side.

[isf]

Originally Posted by ericthered

is 10,000 years the right number? I found this chart of how the stars near earth are moving relative to us, and it does seems that 10k years is a meaningful amount of time in the relative motion of stars, if just a bit on the short side.

It seems to me that a range of 1000-10,000 years is useful, but I don't know if it is plausible.

[Proteus]

Why is time the limiting factor rather than, say, some combination of distance and angular velocity? The Sun orbits the galaxy more-or-less in concert with a number of stars; others, though, move in different directions or speeds.

I believe that Arcturus is currently diving headlong through, rather than along, the galactic disk. Some nearby red dwarfs also have motion very different from the Sun’s (or at least look more like they do, because they’re so close!). Those seem more likely to dislodge some hand-waving hyperspace-ley-line than to have it simply expire like a tub of yogurt.

I’ve always wanted to run a universe where the distance one can travel depends mainly on the degree of gravitational stress (tidal force) at your origin. You’d need to get *close* to a star, rather than far away, and white dwarfs or neutron stars would become major nexus hubs. However, the *accuracy* of your travel (to avoid misjump or disappearance) depends on your ability to measure very small units of arc, which gives higher-tech spaceships a strategic edge because they can travel further in a single hop. Space is big and empty, and stars are very hard to target precisely!

[Irish Wolf]

As Niven and Pournelle showed in The Gripping Hand, sequel to The Mote In God's Eye, such a "tramline" network is also affected by other stellar events. The Mote system could be quarantined because the only tramline from its star terminated within the photosphere of a red giant (the titular Eye, with the smaller yellow star being the Mote from the perspective of New Caledonia system) and the Moties didn't have the defensive field needed to survive it, but the collapse and ignition of Buckman's Protostar into Buckman's Star opened a new tramline to another system "nearby".

(For reference, humanity had been using the Anderson Drive for, IIRC, about a thousand years or so by this point; ISTR Mote being set in the early 3010s.)

[Fred Brackin]

Originally Posted by Irish Wolf

As Niven and Pournelle showed in The Gripping Hand, sequel to The Mote In God's Eye, such a "tramline" network is also affected by other stellar events.

In Michael McCollum's Antares Dawn (plus 2 sequels) there was a big network around Antares....until that went supernova.

https://www.amazon.com/Antares-Dawn-...s%2C170&sr=8-1

Ir's quite a good book and I recommend it on general principles but it's a very good model for jumpline networks.

[ericthered]

Originally Posted by isf

It seems to me that a range of 1000-10,000 years is useful, but I don't know if it is plausible.

Looking at the chart, 10,000 looks plausible, but I have my doubts about 1,000.



On the other hand, if existing connections matter, you can have a single change butterfly its way through the entire network. And you can even have civilizations kill their trade networks the first time someone thinks they can make an artificial one.

[isf]

Originally Posted by Fred Brackin

In Michael McCollum's Antares Dawn (plus 2 sequels) there was a big network around Antares....until that went supernova.
Ir's quite a good book and I recommend it on general principles but it's a very good model for jumpline networks.

Thanks, that sounds interesting enough to order a copy.

[doctorevilbrain]

The chart of the stars near Earth says not found.

[isf]

Originally Posted by Proteus

Why is time the limiting factor rather than, say, some combination of distance and angular velocity? The Sun orbits the galaxy more-or-less in concert with a number of stars; others, though, move in different directions or speeds.

Even if I figure out how to use Astrosynthesis well enough to script that, that's a lot of work for too little return.