[Spaceships] Sneaking up on a Megastructure

[Fred Brackin]

Originally Posted by AlexanderHowl

We do plenty will less than 1 photon per second, a lot of the deep space photos are long exposure photos that might only gather a few dozen photons.

We don't do it real time which is what you wanted the AIs to be doing. Heck, now you've got them being Arisians "sensing" things over thousands of LY.

[Anthony]

Originally Posted by Fred Brackin

Over interstellar distances (at least) I believe you will hit numbers that are so small that they will be less than 1 photon of that wavelength per second. I don't think even hypothetical/indescribable AI geniuses can do much with less than 1 photon per second.

Depends on the read noise in your detectors, and the resolution (which determines background noise).

[doctorevilbrain]

Why is it 4700 light years?

[AlexanderHowl]

I believe that is 30 million AU (-95 to detect).

[Anthony]

The main problem for the AIs is that this isn't really an AI problem, it's a hardware problem; no quantity of AI can make up for insufficient data. A SM+2 probe at 1 AU will have an apparent magnitude of around 30, and can be detected by 2-3 meter optics if you spend enough time looking (e.g. Hubble Deep Field), though you'd need something like ten thousand of them to monitor the entire sky (no new tech required, just lots of money).

A deep space object at 10,000 AU, if not internally powered, has +20 apparent magnitude from distance (increasing our 2 meter optics to 20 kilometers), and another +20 apparent magnitude for temperature (magnitude 70, increasing the optics to 200,000 kilometers). Our probe probably can't actually run that cool, if we set it to a mere magnitude 55 we can make do with 200 kilometer optics (and as we noted above, 10,000 of them).

Is that doable at TL 12? Eh, maybe. Current curves suggest that max practical telescope size should be something like TL*2-12 (so SM+4 today, or about 10 meters, and a mere 200 meters at TL 12), but you can certainly justify other numbers.

[Anders]

Originally Posted by AlexanderHowl

Well, there are ways to redirect emissions. For example, it is possible to reflect and redirect IR using very thin sheets of aluminum, so the outer shell of an MB could channel the majority of the emissions in a specific direction, if the builders desired. In fact, a sophisticated system could reflect and redirect IR emissions to pump IR lasers for a defense system.

I don't know enough about physics to state it definitely, but this sounds like you're trying to make energy flow from a cold area to a hot one without using energy... that's a 2nd law violation.

[Anthony]

Originally Posted by Anders

I don't know enough about physics to state it definitely, but this sounds like you're trying to make energy flow from a cold area to a hot one without using energy... that's a 2nd law violation.

Well, the IR lasers are a problem. Directional emissions are not a problem per se as long as they don't have intensity exceeding the normal brightness of an object that size.

[DataPacRat]

Originally Posted by Anders

I don't know enough about physics to state it definitely, but this sounds like you're trying to make energy flow from a cold area to a hot one without using energy... that's a 2nd law violation.

Well, not necessarily. It's possible to take a ship's heat emissions, so that instead of being emitted in all directions equally, more of the heat gets shoved across a smaller area. Say, having (almost) all of a ship's heat radiated to the rear of the ship instead of ahead of it. It does require generating higher temperatures in the radiators, but is technically physically possible.

This doesn't allow for true stealth in space against a well-equipped opposing force because it's relatively easy to scatter sensor platforms across a wide area, enough of them to get intercepted by any feasible heat-emission cone.

... Of course, trying to do the same for a SM+53 Matrioshka Brain, which emits a star's entire output as heat, adds a new set of challenges, and it seems unlikely to be worth the required effort.

[DataPacRat]

For some quick figuring of the probe detecting a Matrioshka Brain, I'm getting the factors:

Base skill 12
Single-Minded +3
Size +53
Time Spent 30 minutes +5
Range 25 lightyears (150T mi) -103
Array Level +2
Zooming in on target star +2
In Plain Sight +10
In Space +24
IR Signature +10
= effective skill 18 at 25 lightyears.

... Can anyone tell me if I'm getting any of that wrong?

[DataPacRat]

Can anyone think of how to adapt the 'Interstellar Signal Detection' guidelines in SS5 p32 to snagging whatever transmissions spill out of a Matrioshka Brain? Eg, what should I count the MB's population as, and does it count as having a spaceport?

(For this part, I'm mainly interested in how far out the probe would be when it most likely starts collecting language samples to start decrypting and analyzing with the Linguistic Assessment rules, a few pages later.)