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Message: <blockquote data-quote="Ovinomancer" data-source="post: 8260250" data-attributes="member: 16814">I mean, sure, okay, you've read an internet page, so clearly I should defer to you on this matter.  Ships radiate much more power than a dedicated transmitter designed to be heard across interplanetary distances, and it only takes 4 hours to scan the entire sky and pick out a ship radiating 20 watts at interplanetary distances.  I mean, the fact that the power loss is 1/r^3, at the distance of Mars from Earth at it's closest point, a ship radiating 200 watts of waste power in a single spectrum (because, I mean, why wouldn't it radiate all of it's power in the same spectrum, right?) would have that signal knocked down to.. lemme see, 200 watts is 200 kg*m^2/s^3 divided by 5.5 x10^6 meters cubed (or roughly 125 x 10^18 meters) would reduce that signal strength by a factor of.... will you'll need to use SI notation because there isn't a name for that small a thing yet.  And the background cosmic radiation strength is higher than that, even outside the microwave range.So, perfectly, a ship radiating 10 times as much energy in a narrow spectrum at the distance of Earth to Mars is lost in the background. The bit about finding Voyager is hiding a lot of information for the purposes of a poor argument on the webpage.  Yes, the Green Bank telescope picked out Voyager in 1 second, but this is eliding the fact that it took a second for a telescope to even see the light from a dedicated and focused active transmitter when it both knew the frequency to look for AND was pointed right at it.  It didn't scan the entire sky and detect the bogey, it was given precise instructions where and what to look for and it still, with some of the best algorithms for detection of anomalous signals, took a second to do it.  With a 100m parabolic antenna dish.Recall that your source webpage is intended to provide science-fiction writers some top cover for realism in their stories, where they can postulate lots of things that are near true or fantastical but lampshaded.  It is not a scientifically accurate webpage, it's just a close enough for sci-fi webpage.  It also makes a number of assumptions about things, like what a torchship is, an uses those assumptions throughout.Let me unpack a bit about how we "see" Voyager.  For one, the assumption set in that is that the signal falloff is much better approximated by 1/r^2 rather than 1/r^3.  That means the signal will be a whatever the magnitude of the distance is times stronger from Voyager than from a similar signal evenly radiating into space.  This makes a big difference.  Secondly, Voyager is radiating on a specific frequency, meaning all of it's power is focused into that one frequency.  This make detecting that signal much better.  To give an indication, it's like everything's an even dull white color (random frequency background radiation) and I shine a red light at you from in this, it will stand out better because it's a specific color.  Similar concepts here.  So, Voyager is doing us some favors -- it's radiating using a focusing antenna that massively improves effective strength of the signal, it's doing it in a narrow frequency band, and we know where it is in the sky.  This allows us to detect Voyager.  And by "detect" we mean "hey, there's a strange signal there along this line of bearing."  Contrast this with a ship, even assume you can say how much more power it radiates, that power will be radiating all around, so you won't get the favorable gain of a focused transmitter.  Secondly, that power will be across a wide range of the spectrum -- so will be radio bands (and that's a huge band), some will be visible light, and some will be heat (infrared), so even if you say it's emitting a lot of power, you can't look across the entire spectrum because it doesn't add together like that.  In any given spectrum you're searching, the actual radiated power will be much less.Finally, given you place so much stock in the webpage, why does it say that the maneuvering thrusters of the space shuttle, which put much more power than anything we're talking about here, would only be detectable out to the asteroid belt?  This is a specific, much higher power release, nominally in a relatively narrow spectrum, and yet your webpage of choice is saying that, when looking for it specifically, you'd only see it within a few AU?  That, alone, should give you pause to consider exactly what set of assumptions that article is using.  Everything they say could be true, if you unpack all of their unstated assumptions.  The reality is that many of those assumptions are perfect for their examples and propose things that wouldn't actually be the case.  Like stealth in space -- very, very doable, but not perfectly doable, and their point here is that perfect stealth is impossible, which is a rather facile argument to make to begin with.</blockquote>

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