Bluesqueak wrote:Dilandu wrote:
Sigh. With early XXI-century equipment.
Guys, you really need to refresh your astronomy. Space is basically the very contrast "cold" background. Any heat source could be easily detected on enormous distances with relatively cheap equipment. We could directly observe exoplanets literally THOUSAND of lightyears away (like CVSO 30 system, 1200 ly from Sun) - and no exoplanet emit as much energy as those supposed planetary-moving engine.
If Gbaba have at least our tech level (and there are "some indications" in books that they, indeed, have ) they could arrange for periodical scans from automated stations around their sphere of influence with literally miniscule resource requirements. So no, you could NOT hide planetary-moving engines even in space.
Sigh. Do they have time travel?
You've forgotten that the exoplanets we are currently 'observing' are in fact the state of play 1,200 years ago in time. If the colonists moved sufficiently far outside the Gbaba sphere of influence (which they did), any automated systems would only note an increase in heat several thousand years in the future.
You've also made an assumption that I was talking about moving a moon, with the consequent ginormous engines - probably because I joked about Iapetus - when I actually said 'build'. Build a moon.
More to the point, the entire premise of Safehold is that it IS possible to hide from the Gbaba if you go far enough.
Dilandu, if the Gbaba are as good at detection as you think, the entire premise of the series is destroyed. There can be no Safehold, because the Gbaba have already detected the planetary system, and will have noticed the energy produced by an entire fleet of Interstellar spaceships.
Except they won't, because one thing we do know about Fed tech is that they can 'stealth'. Likewise, they'll have noticed the energies used in Terraforming- except everyone thought they could hide that too.
So they can hide the energy event of spaceships, they can hide one-off energy events like the high tech gear for terraforming. Possibly they could even hide a one-off event like making a moon a bit bigger. What they can't do is hide the continued emissions of a high tech civilisation.
The Operation Ark mission planners worked from the assumption that Gbaba scouts would capture lightspeed data from their eventual destination system either during terraforming operations or the "silent colony" era. That was the point of temporarily reverting to a pre-technological civilization. When the Gbaba scouts analyzed returns from the Safehold system, they wouldn't pick up anything because the scouts would be too early.
In OAR, Pei Kau-yung openly states the mission planners were worried about an active search. Waiting for signals to reach fixed monitoring installations within Gbaba space might have been how the TF was originally detected, but it wouldn't work for tracking down any escaping humans. By the time the signals reached the Gbaba, a human colony would have had enough time to build up to be an even greater threat than the TF had managed.
This means the Gbaba need to either account for all of their victims' ships--or, more likely--deploy a massive number of scouts to move through hyperspace, drop out to deploy huge distributed radio telescopes and other sensors to listen for a few weeks, and then move out a few light-years before repeating their efforts. For the Gbaba, missing a colony means that their former victims get to come back looking for a war when they're ready. They literally cannot use passive monitoring at home because by then it'd be too late for them. They have no choice but to send out ships.
While I realize you're joking about a time machine, given the ability to effectively bypass the speed of light via hyperspace, the Gbaba (or any FTL-capable species) is equipped with a sort of temporal telescope. That's close enough for their purposes. Peter F. Hamilton used this in Pandora's Star for his Commonwealth Saga. An astronomer observes two stars that were suspected Dyson spheres. All emissions are instantaneously cut off, so he buys time on another telescope light-years away to verify the same moment in time.
Operation Ark was about finding a distant enough colony that their emissions would take millennia to reach the Gbaba, and then hiding long enough that any scouts would move past the colony. Langhorne's modifications merely extend that: no emissions, ever. The scouts are the primary threat, because they're looking for emissions that are only a few years old at best. Time and the inverse-square law are their biggest protection from future detection from within in Gbaba space.
The problem with building a moon is that you don't have millions of years to wait for it to form out of a mass of rock. You need to move 7.342×10^22kg of mass (e.g. Luna) to one location, and then use external forces to effectively condense all of that mass. That generates a ridiculous amount of heat, which would take centuries to radiate away. To say nothing of the energy that'd be radiated during the attempt itself. It'd also take a great deal of time, and we know that Safehold only took a few decades (at most) to terraform.
They could build a hollow moon, I suppose, but there's a problem with that as well. The Gbaba could measure the moon's moment of intertia which would make it abundantly obvious that it's an artificial body. And then they have to look more closely. Or their scouts could just compare their new data to older scan data. Is there a major difference? Plus, building a Dahak or just a regular 'ol hollow moon would require extensive space-based industry. The same sort of industry that sets off a warning flag. If they were going to do that, they'd never have bothered with reverting to a pre-technical society to begin with.
Compared to those energies, the energy and waste heat of terraforming operations (as well as their ships) would be minimal. The TF didn't shift Safehold's orbit. They didn't try to build up or modify an atmosphere, add mass, reshape the crust, or anything else like that. For the most part, they had a perfectly usable Earth-similar planet and just had to modify its biosphere. If they really wanted a moon for whatever reason, they'd just reject the system and move on. Apparently, habitable planets are common enough in the Safehold universe.
The original Operation Ark wasn't about eliminating *any* risk of detection whatsoever. It was just about minimizing it during the critical period when they expected Gbaba scouts to be searching for any escaped humans. Escape the threat of an active search in the first ~500 years (OAR), and don't worry about passive detection in the centuries or millennia or two after that. By the time the Gbaba discovered the humans (if they ever did), the colony would have had centuries to build up a population and space presence that would have made even the TF look positively parochial.
At least, that was the plan until Langhorne screwed it up. On the plus side, we wound up with a much more interesting story as a result.