You know, every so often, I get sufficiently irritated with one of these sweeping declarations that I run some numbers.
In this case, I decided to look at moving Iapetus from Saturn orbit to Earth orbit. More or less - I ignored the change in angular momentum needed to get it into a satisfactory orbit at destination since it gets lost in the rounding off.
Since we know nothing about the technology being used I had to make an arbitrary assumption: the change in kinetic energy represents ~10% of the total energy budget for the operation. My own feeling is that this is pessimistic, but even if I'm off by 2 orders of magnitude the difference to the final result is barely noticeable. [that's in the direction of .1% - _improving_ efficiency makes no practical difference at all].
The other assumptions are that the operation takes 8 years, that energy expenditure is constant over that time, and that waste energy is radiated isotropically. Like improving efficiency, making the move faster changes little, but I figure we should take our time so as to minimise the chances of breaking the thing [celestial bodies are really rather flimsy]. Constant luminosity is a simplification, but reasonable given what we know of the tech - we aren't messing around with impulse drives here. Isotropic radiation is necessary, as if it _isn't_ you simply ensure that the radiation is directed someplace the Gbaba aren't and this whole exercise is a waste of time.
Given those assumptions, delta-V is 20km/s, total expenditure is 3.65810^37 ergs [why ergs? that's the way astronomers do things] and bolometric luminosity is 1.44* 10^29 ergs/s. Truly enormous, right?
Well, actually, on an astronomical scale it's pretty meaningless. It's 3.77*10^-5 times the luminosity of the sun, which with early XXI-century tech is detectable to a distance of perhaps 30ly. At the distance the Gbaba would be seeing it from it won't be resolvable so it has to be seen against the glare of the primary. Which _might_ be possible, depending on the actual SED of the radiator [remember, I said the number above is bolometric luminosity] but will be extremely difficult to distinguish from natural variation even if Kau-Yung happens to be in a completely empty background field for them. For a star in the thin disk, the odds of that are slender. They're somewhat better for the thick disk, but the likelihood of a thick disk star having human-habitable planets aren't good, and few if any of them are going to be G6V anyway. There's a much better chance, assuming you're maintaining an all-sky survey, of noticing that a star up in the halo is behaving oddly - but nobody in his right mind is going to be looking out there for a place to settle.
Dilandu wrote:Isilith wrote:
And how would they notice it from 100's of LY away?
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.