Space survey operation...
Johnny1a
star system, about which you know only what you learned by observation
of the light from primary from a distance of at least several light-
years.
You could learn a lot by that alone over time, but let's assume you
don't have lots of time to observe it, instead you're sending a
scouting mission ahead to the new star to take a look before you
arrive or pass through the system. Let's turn it around and use Sol
as the target star, assume an alien scout ship arrived in the Solar
System at, say, the distance of the Kuiper Belt, knowing nothing other
that that the primary is a G2 with a high metalicity, and (from the
wobble and other long-range obsevations) that is has planets of some
sort.
If you were equipping a vessel to do a survey of the Sol System, what
would you equip it with, and what could be expected to be learned in a
reasonably short time, from the arrival point at Kuiper distance?
Assume a vessel with the volume of the Space Shuttle orbiter, for
convenience, and limit the observations to methods using known physics
and radiations. What would be the most reasonable way to proceed on
this survey (neglecting what happens when they detect Earth's
artificial signals).
Brian Davis
> Hypothetically, suppose you were sending an FTL spacecraft to a new
> star system... sending a scouting mission ahead to the new star to
> take a look before you arrive or pass through the system.
Hmm. If you have magical FTL, then I'm not at all sure why you would
"pass through" the Sol system. And if the scouting mission *doesn't*
have FTL, waiting for the scout report is going to take a loooong time
for a culture that you're claiming doesn't want to wait. Can you
clarify?
> assume an alien scout ship arrived in the Solar System at, say, the
> distance of the Kuiper Belt, knowing nothing other that that the primary
> is a G2 with a high metalicity, and (from the wobble and other long-range
> obsevations) that is has planets of some sort.
Well, it would know the masses and at least reasonably good positions
of those planets. If it was along the ecliptic, it might have the
sizes and densities of those planets (waiting for one transit in a
couple hundred years doesn't sound too unreasonable if you start
looking from several hundred ly away, watching as you approach even at
STL speeds). Transits can get you some chemical information as well as
temperature. So with nothing more than time and a telescope, you've
got a reasonable start.
> If you were equipping a vessel to do a survey of the Sol System, what
> would you equip it with, and what could be expected to be learned in a
> reasonably short time, from the arrival point at Kuiper distance?
If it's going to sit in the Kuiper belt, give it a big telescope.
Optical and IR will tell you a whole lot. Better yet, use sub-probes
to synthesize a multi-element long baseline system. That doesn't take
much (not even much high tech).
> Assume a vessel with the volume of the Space Shuttle orbiter...
How much time? Can it build things (if you have a civilization that
can cross interstellar distances... details like automated mining of
the Oort cloud start seeming minor)? Will it be sending anything
physical into the inner system?
--
Brian Davis
Greg Goss
>If you were equipping a vessel to do a survey of the Sol System, what
>would you equip it with, and what could be expected to be learned in a
>reasonably short time, from the arrival point at Kuiper distance?
>Assume a vessel with the volume of the Space Shuttle orbiter, for
>convenience, and limit the observations to methods using known physics
>and radiations. What would be the most reasonable way to proceed on
>this survey (neglecting what happens when they detect Earth's
>artificial signals).
AC Clarke once proposed detonating a nuclear explosion in space, and
watching for the reflections for dinosaur-killers. Do several of
these and you should get the orbits of a lot of bodies.
Is the "radar" reflection of something like this strong enough to
detect with an omnidirectional detector? How closely could you
resolve the direction to a reflecting body with a detector that
doesn't know what direction to watch?
--
Tomorrow is today already.
Greg Goss, 1989-01-27
Brian Davis
> AC Clarke once proposed detonating a nuclear explosion in space, and
> watching for the reflections for dinosaur-killers. Do several of
> these and you should get the orbits of a lot of bodies.
It might be worth it to do the math on that one - you've already got a
plenty bright enough light source, the Sun, in the same neighborhood.
A shiny 1 m^2 surface at 3 AU from the Sun reflects 152 W (& from 40
AU out, you're looking at it from a distance of 43 AU... on the far
side of the Sun). To get the same signal, you have to get an object on
the near side of the Sun (37 AU from you) reflecting just 113 W (it's
6 AU closer). Let's say you can get half the yield of a 20 Mt weapon
into light, and *all* the light is in your detection band (tough,
since a high percentage is in UV and X-ray), and that it's all
released in 1 ms. That's a luminosity of 4.23e+16 W, so you can "light
up" objects better than the Sun only out to a range of around 54,700
km. A sphere that size is 6.8e+14 km^3, compared to 1 AU^3 which is
3.3e+24 km... and the volume of the main belt is around 40 AU^3. And
even that assumes you have a detector that can resister really tiny
amounts of energy on single pixels with high (ms scale) time
resolution.
That doesn't look good. It's hard to see a reason to use a tiny
penlight in the middle of the day.
A better use for even a small nuclear warhead would be to detonate it
in an atmosphere of interest to get emission spectra. Although if you
have a technology that can reach FTL or high STL speeds, kinetic
impactors get you there *far* cheaper.
--
Brian Davis
Mike Ash
Greg Goss <go...@gossg.org> wrote:
Isn't the Sun basically doing this for us, all the time, and far more
brightly?
--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon
Mike Dworetsky
The main problem with using a telescope from that distance (around 50 AU) is
that, for example, the Earth will never be more than one degree from the
Sun. Even Jupiter will be at most about 5 deg from the Sun. This will
cause all sorts of problems with scattered light in the optics and
instruments. Most space telescopes that do not observe the Sun are
constrained to point at least 90 deg away from it, and they carry
sunshields. With extended shields you can get that down to maybe 45 deg.
At that distance the Earth will be of order 0.25 arcsec diameter. Even with
a good scope that could be carried on an orbiter, you wouldn't resolve
continents at that sort of distance.
For something as small as the orbiter, you could and should come in a lot
closer unless you have reason to suspect an advanced space-faring
civilization which you do not want detecting your presence.
Sensitive radio telescopes (which need a large area) could help to look for
signs of technology to the radio level.
--
Mike Dworetsky
(Remove pants sp*mbl*ck to reply)
Greg Goss
>On Dec 14, 1:52 am, Greg Goss <go...@gossg.org> wrote:
>
>> AC Clarke once proposed detonating a nuclear explosion in space, and
>> watching for the reflections for dinosaur-killers. Do several of
>> these and you should get the orbits of a lot of bodies.
>
>It might be worth it to do the math on that one - you've already got a
>plenty bright enough light source, the Sun, in the same neighborhood.
That might help if the sun had abrupt pulses. It's the abrupt change
in brightness that tells you that you're looking at a local dot and
exactly how local.
> Let's say you can get half the yield of a 20 Mt weapon
>into light, and *all* the light is in your detection band (tough,
>since a high percentage is in UV and X-ray), and that it's all
>released in 1 ms.
Is light the best? Why not radar frequencies? Or some combo that
watches many bands?
Greg Goss
>That doesn't look good. It's hard to see a reason to use a tiny
>penlight in the middle of the day.
Police use penlight-strength Lidar. In the daytime. Pulses are
important.
Brian Davis
> That might help if the sun had abrupt pulses. It's the abrupt change
> in brightness that tells you that you're looking at a local dot and
> exactly how local.
Blink comparators work pretty darn well... just because something is
old, doesn't mean it's not a workable solution. You take a picture
"now", and one "then", and see what moved. Do it again and you have
rough orbits. Continue. If you want to watch for "flashes" in this
context, you need to not just detect, but image them... which is
significantly different.
> Is light the best? Why not radar frequencies? Or some combo that
> watches many bands?
A unique frequency (one not otherwise prominent) that is easily
detectable would be best. A nuc in space is essentially a black-body
spectrum (a really really *hot* black-body spectrum). And the radar
emissions would be zero (close enough).
--
Brian Davis
Brian Davis
> Police use penlight-strength Lidar. In the daytime. Pulses are
> important.
Sure. But for tagging a car, you just need to presence or absence of a
return signal (plus some information like doppler shift or delay
interval). Using a bomb as a bright flash source in the inner system
means you need to image lots of returns, distributed in space, and
distributed in time... while ignoring the fact that you have a bright
source sitting in the picture already that dwarfs your bomb by a
factor of 10,000,000,000. I'm not saying it won't work... I'm just
pointing out that it seems to be a tremendously bass ackwards way of
doing things.
Consider my rough calculation previously. If you want to image even
50% of the asteroid belt (from, say, 2 AU to 4 AU and out-of-plane by
+/- 0.5 AU), you need 1e+11 20 Mt weapons. I suspect... that might be
*slightly* inefficient.
--
Brian Davis
Brian Davis
<platinum...@pants.btinternet.com> wrote:
> The main problem with using a telescope from that distance (around 50 AU) is
> that, for example, the Earth will never be more than one degree from the
> Sun... This will cause all sorts of problems with scattered light in the optics and
> instruments.
What about the possibility of simply remaining in the shadow of a KBO?
That would seem to be a plenty big enough sun shield.
> At that distance the Earth will be of order 0.25 arcsec diameter. Even with
> a good scope that could be carried on an orbiter, you wouldn't resolve
> continents at that sort of distance.
How about a Darwin-style array? If you can come up with ways to image
planets ly away... a synthetic aperture system might be something to
deploy even in close... if you consider 50 AU to be "close".
--
Brian Davis
Suzanne Blom
>
> A better use for even a small nuclear warhead would be to detonate it
> in an atmosphere of interest to get emission spectra. Although if you
> have a technology that can reach FTL or high STL speeds, kinetic
> impactors get you there *far* cheaper.
>
just a probe to see what was here?--and how many other extinction events?
Damien Valentine
> Hmm, so are you positing that the asteroid that killed the dinosaurs was
> just a probe to see what was here?--and how many other extinction events?
I don't see how your conclusion follows from Mr. Davis' comment.
John F. Eldredge
An asteroid running into the earth is an example of a kinetic impactor.
--
John F. Eldredge -- jo...@jfeldredge.com
"Reserve your right to think, for even to think wrongly
is better than not to think at all." -- Hypatia of Alexandria
Tim Little
> Brian Davis <brd...@iusb.edu> wrote:
>>That doesn't look good. It's hard to see a reason to use a tiny
>>penlight in the middle of the day.
>
> Police use penlight-strength Lidar. In the daytime. Pulses are
> important.
Lidar energy is both concentrated into an extremely narrow frequency
band and very highly collimated. Sunlight isn't. A nuclear flash
likewise isn't.
If you can detect the reflected pulse at all, you could have detected
reflected sunlight much more easily. If the probe can use FTL at
will, just capture images from positions a hundred thousand or a
million kilometres apart, and compare. Otherwise just compare
exposures over a few hours or days, because essentially everything in
the system is moving with a decent angular speed relative to you and
the stars in the background aren't.
- Tim
Brian Davis
It doesn't (in any reasonable way). I was pointing out that if you
want to gather emission spectra, you can do it with any technology
that can deposit a lot of energy into a small volume. A nuclear weapon
does this. A kinetic impactor does it better... but there's no need to
use a large one (and really good economic reasons to use small ones,
as they'll work better/cheaper). Heck, a high-power laser would work,
but collimation over 40-50 AU is... troublesome.
--
Brian Davis
Greg Goss
>On Dec 14, 1:44�pm, Greg Goss <go...@gossg.org> wrote:
>
>> That might help if the sun had abrupt pulses. �It's the abrupt change
>> in brightness that tells you that you're looking at a local dot and
>> exactly how local.
>
>Blink comparators work pretty darn well... just because something is
>old, doesn't mean it's not a workable solution. You take a picture
>"now", and one "then", and see what moved. Do it again and you have
>rough orbits. Continue. If you want to watch for "flashes" in this
>context, you need to not just detect, but image them... which is
>significantly different.
You've just dropped into a solar system. You're gonna wait a year or
two for some of the planets to move significantlhy?
>
>> Is light the best? �Why not radar frequencies? �Or some combo that
>> watches many bands?
>
>A unique frequency (one not otherwise prominent) that is easily
>detectable would be best. A nuc in space is essentially a black-body
>spectrum (a really really *hot* black-body spectrum). And the radar
>emissions would be zero (close enough).
--
Brian Davis
> You've just dropped into a solar system. You're gonna wait a year or
> two for some of the planets to move significantlhy?
First, you'll already know where the planets are... as well as their
masses & orbital eccentricities, as you can do that from ly away with
current technology. Secondly, if you can brake to a stop in the Kuiper
belt, what's the time pressure? Third, how far do you think things
have to move to see them? For the deep inner system, things are moving
fast anyway... while for the more distant parts of the system, where
thing are moving slowly, you have a much *much* larger volume to
search (look again at the rough underestimate I gave above for the
number of 20 Mt weapons you'd need to make a poor census of just the
main belt).
And if time is a problem, how long are you willing to wait to get the
1e+11 nuclear warheads into position 40 AU or more away?
Again, it's not that it's impossible - just that it seems, well...
stupid. If I was reading this as a story, these would be questions
that would pop to mind immediately, and start really challenging my
suspension of disbelief.
--
Brian Davis
Tim Little
> You've just dropped into a solar system. You're gonna wait a year
> or two for some of the planets to move significantlhy?
"Significant" is some small multiple of the angular resolution. With
even pathetic resolution of just an arcsecond, that's a matter of a
day or two at most. For bodies that aren't frozen snowballs, it's
hours. With a quick FTL flit to another vantage point, it's as soon
as you can collect enough photons.
- Tim
alie...@gmail.com
> On 2010-12-14, Greg Goss <go...@gossg.org> wrote:
>
If the probe can FTL at will, just take images of the whole system
on the way in a few light-months apart, eliminate the stars, and
calculate orbits at leisure. Either do it far enough away that Sol
doesn't blind your optics or use an occulting disk.
That way you know where everything is (and will be) before you even
enter the system.
Mark L. Fergerson
Cryptoengineer
@mid.individual.net:
> Brian Davis <brd...@iusb.edu> wrote:
>
>>On Dec 14, 1:44 pm, Greg Goss <go...@gossg.org> wrote:
>>
>>> That might help if the sun had abrupt pulses. It's the abrupt change
>>> in brightness that tells you that you're looking at a local dot and
>>> exactly how local.
>>
>>Blink comparators work pretty darn well... just because something is
>>old, doesn't mean it's not a workable solution. You take a picture
>>"now", and one "then", and see what moved. Do it again and you have
>>rough orbits. Continue. If you want to watch for "flashes" in this
>>context, you need to not just detect, but image them... which is
>>significantly different.
>
> You've just dropped into a solar system. You're gonna wait a year or
> two for some of the planets to move significantlhy?
No. You take a sky survey, move your ship an AU or two, and take another
one. Compare them.
pt
Steve Hix
wrote:
> Brian Davis <brd...@iusb.edu> wrote:
>
> >On Dec 14, 1:44 pm, Greg Goss <go...@gossg.org> wrote:
> >
> >> That might help if the sun had abrupt pulses. It's the abrupt change
> >> in brightness that tells you that you're looking at a local dot and
> >> exactly how local.
> >
> >Blink comparators work pretty darn well... just because something is
> >old, doesn't mean it's not a workable solution. You take a picture
> >"now", and one "then", and see what moved. Do it again and you have
> >rough orbits. Continue. If you want to watch for "flashes" in this
> >context, you need to not just detect, but image them... which is
> >significantly different.
>
> You've just dropped into a solar system. You're gonna wait a year or
> two for some of the planets to move significantlhy?
You've just spent x years traveling to the system. What's a few more days?
Erik Max Francis
Not to mention: Even if this idea would work, how quickly do you think
you're going to be able to spread your "detector" nukes around the
stellar system? Surely not much more quickly than just watching the sky
with a good telescope for a while.
--
Erik Max Francis && m...@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM/Y!M/Skype erikmaxfrancis
Moving to the rhythm / Can you feel me breathe / What else do we need
-- Oleta Adams
Damien Valentine
> An asteroid running into the earth is an example of a kinetic impactor.
Yes, of course. But to go from "a kinetic impactor might be useful in
this hypothetical situation" to "OMG Chixulub was an alien space
probe!!!11" seems a bit of a leap.
Mike Dworetsky
> On Dec 14, 1:17 pm, "Mike Dworetsky"
> <platinum...@pants.btinternet.com> wrote:
>
>> The main problem with using a telescope from that distance (around
>> 50 AU) is
>> that, for example, the Earth will never be more than one degree from
>> the
>> Sun... This will cause all sorts of problems with scattered light in
>> the optics and instruments.
>
> What about the possibility of simply remaining in the shadow of a KBO?
> That would seem to be a plenty big enough sun shield.
Good point, but requires considerable effort at station keeping.
>
>> At that distance the Earth will be of order 0.25 arcsec diameter.
>> Even with
>> a good scope that could be carried on an orbiter, you wouldn't
>> resolve
>> continents at that sort of distance.
>
> How about a Darwin-style array? If you can come up with ways to image
> planets ly away... a synthetic aperture system might be something to
> deploy even in close... if you consider 50 AU to be "close".
A Darwin array would need something bigger than a Shuttle to carry and
deploy it. If you increase the size of the survey craft you could probably
do this.
alie...@gmail.com
What's the resolution of a Nicoll-Dyson laser? Suppose the lasers
are replaced with solid-state imagers that can be phaselocked. I'm
sure this has been proposed?
This:
http://en.wikipedia.org/wiki/James_Nicoll#Nicoll-Dyson_Laser
claims planet-sized targeting capability at millions of light years
range, which seems a bit overoptimistic. If it's correct, what can a
Nicoll-Dyson *telescope* see of Sol system from forty or fifty ly?
Hm. How else would you sight a N-D laser?
Mark L. Fergerson
Suzanne Blom
Ah, but I'm a science fiction person. Leaping in space is one of my
specialties.
Tim Little
> http://en.wikipedia.org/wiki/James_Nicoll#Nicoll-Dyson_Laser
>
> claims planet-sized targeting capability at millions of light years
> range, which seems a bit overoptimistic. If it's correct, what can a
> Nicoll-Dyson *telescope* see of Sol system from forty or fifty ly?
It's equivalent to a lens a few AU across, assuming the system can be
kept properly coherent across that diameter.
With sufficient data processing (which is a given for entities that
can build such a thing), pretty much everything in the system should
be resolvable down to a metre. Basically whatever you could see with
acute eyesight from a few kilometres distance, only brighter (since
our eyes can't do long exposures).
The image processing task for imaging an entire solar system at once
would be immensely difficult, but I suspect that any entities capable
of building a N-D telescope would be able to deal with it. Some of
the challenges would include motion of the objects being studied
(typically 10000 "pixels" per second) and depth of field (on the order
of 3000 km).
--
Tim
Mike Ash
Tim Little <t...@little-possums.net> wrote:
A 4-byte-per-pixel image of a 2AU x 2AU square would require about 300
zettabytes of storage, a number so large I had to look up the definition
to see exactly how big it was. This image would thoroughly exceed the
normally absurdly-large memory address space of a modern 64-bit CPU.
It's approximately equal to one thousand years' worth of worldwide
internet traffic at 2010 levels. Fun.
Brian Davis
> A 4-byte-per-pixel image of a 2AU x 2AU square would require about 300
> zettabytes of storage...
Although to be fair, why would you ever record that as an image?
Simple image compression would drastically compress this (BY FAR most
of the field pixels are of course black, for a suitable threshold of
'black'), and custom compressions (coordinates of spots, with perhaps
brightness and total pixel size of the spot) would do far far better.
How do you record an orbit? As a series of 6 numbers, or as a multi-
frame series of pixel images?
*Analysis* would still be tough... but again, there's absolutely no
need to have the "left half" of a 4 AU^2 FOV handy to compare to the
"right half".
--
Brian Davis
alie...@gmail.com
> On 2010-12-16, n...@bid.nes <alien8...@gmail.com> wrote:
>
> >http://en.wikipedia.org/wiki/James_Nicoll#Nicoll-Dyson_Laser
>
> > claims planet-sized targeting capability at millions of light years
> > range, which seems a bit overoptimistic. If it's correct, what can a
> > Nicoll-Dyson *telescope* see of Sol system from forty or fifty ly?
>
> It's equivalent to a lens a few AU across, assuming the system can be
> kept properly coherent across that diameter.
>
> With sufficient data processing (which is a given for entities that
> can build such a thing), pretty much everything in the system should
> be resolvable down to a metre. Basically whatever you could see with
> acute eyesight from a few kilometres distance, only brighter (since
> our eyes can't do long exposures).
A *meter* ‽‽‽ Expletive deleted!
> The image processing task for imaging an entire solar system at once
> would be immensely difficult, but I suspect that any entities capable
> of building a N-D telescope would be able to deal with it. Some of
> the challenges would include motion of the objects being studied
> (typically 10000 "pixels" per second) and depth of field (on the order
> of 3000 km).
I'm thinking basically an optical phased array antenna.
ISTM that manipulating the phase relationships between the elements
should allow the focal plane to be swept through the volume around a
star. Solar system tomography...
Decreasing the aperture will increase the depth of field (and
decrease the resolution but determining orbits just requires planet-
scale resolution), so do the imaging with part of the array rather
than the entire facing hemisphere; say only the elements within ~10(?)
degrees of the "subsolar point".
Sweep the focal plane back and forth through Sol's immediate
neighborhood, note the positions of resolved planets, then blink-
compare the planets in software (a full orbit of an inner planet WAGs
an ecliptic to help find outer planets). Find something really
interesting like American Bandstand, and you can recruit more sensors
on that hemisphere to improve resolution and reception. And aiming...
With one of these, funding an actual manned interstellar trip might
be a tough sell.
Mark L. Fergerson
Tim Little
> A *meter* ‽‽‽ Expletive deleted!
I had to triple-check the figure too. But then, it would require
maintaining phase relationships to within a fraction of a femtosecond
over distances of a couple of AU. Anyone who can do that deserves
ridiculously fine resolution.
Objects significantly smaller than a metre could still be seen, though
detecting the faint track of photons from such an object as it sweeps
across the field would be an incredible image-processing challenge.
On the other hand, a Dyson swarm probably has processing power in
extreme abundance.
> Decreasing the aperture will increase the depth of field (and
> decrease the resolution but determining orbits just requires planet-
> scale resolution), so do the imaging with part of the array rather
> than the entire facing hemisphere; say only the elements within
> ~10(?) degrees of the "subsolar point".
Planetary resolution only needs an array a hundred kilometres across.
We could possibly achieve that resolution with a small constellation
of interferometric space telescopes in the relatively near future. I
suspect this sort of approach would be sufficient for roughing out the
orbits of planets in a target system. Sensitivity would depend upon
resources available for extending the area of the collectors.
With such a reduced aperture, depth of field would be irrelevant.
> With one of these, funding an actual manned interstellar trip might
> be a tough sell.
I suppose it depends upon how expensive interstellar travel is. I
think it would have to be incredibly expensive to compare with the
cost of running a Nicoll-Dyson telescope. Both are insanely large
engineering projects dependent upon technology we are nowhere near
achieving, with the limiting resources unknown in both cases. I don't
think we could even hazard a ballpark guess as to which would be more
expensive.
With a Dyson swarm, there's enough raw power available to accelerate a
million tonnes to 0.9 c every second. I'm sure a billionth of that
would suffice for a small interstellar exploration program, if energy
were the limiting resource. I doubt it would be.
- Tim
Waddell
chapter describing what you would see at different distances on
approaching a new solar system.
On Dec 13, 6:53 pm, Johnny1a <shermanl...@hotmail.com> wrote:
> Hypothetically, suppose you were sending an FTL spacecraft to a new
> star system, about which you know only what you learned by observation
> of the light from primary from a distance of at least several light-
> years.
>
> You could learn a lot by that alone over time, but let's assume you
> don't have lots of time to observe it, instead you're sending a
> scouting mission ahead to the new star to take a look before you
> arrive or pass through the system. Let's turn it around and use Sol
> as the target star, assume an alien scout ship arrived in the Solar
> System at, say, the distance of the Kuiper Belt, knowing nothing other
> that that the primary is a G2 with a high metalicity, and (from the
> wobble and other long-range obsevations) that is has planets of some
> sort.
>
> If you were equipping a vessel to do a survey of the Sol System, what
> would you equip it with, and what could be expected to be learned in a
> reasonably short time, from the arrival point at Kuiper distance?
> Assume a vessel with the volume of the Space Shuttle orbiter, for
> convenience, and limit the observations to methods using known physics
> and radiations. What would be the most reasonable way to proceed on
> this survey (neglecting what happens when they detect Earth's
> artificial signals).
Johnny1a
> On Dec 13, 9:53 pm, Johnny1a <shermanl...@hotmail.com> wrote:
>
> > Hypothetically, suppose you were sending an FTL spacecraft to a new
> > take a look before you arrive or pass through the system.
>
> "pass through" the Sol system. And if the scouting mission *doesn't*
> have FTL, waiting for the scout report is going to take a loooong time
> for a culture that you're claiming doesn't want to wait. Can you
> clarify?
You read a little too much into my McGuffin.
My actual chain of thought started with some old TV space opera shows
like the original Battlestar Galactica, with the concept of the
‘scouting mission’ flying ahead of a large starship. Trying to apply
logic to those specific shows is pointless, of course, but that set me
to thinking about the more general concept, _would_ it ever really
make sense to send a ‘scouting ship’ ahead of a travelling FTL
starship?
I thought about it and concluded that the answer _could_ be ‘yes’,
depending on the FTL abilities one handwaved. If you assume a big
vessel that is relatively slow in its FTL performance, say taking
months or more to travel from star to star, OR the big vessel needed
huge amounts of energy or consumable resources or effort to go
quickly, making them reluctant to do it without knowing it would be
justified, it might make sense, if you also assume that they can build
a small craft that is much faster, or much cheaper to make the trip.
You also need to assume that they don’t have long-range FTL sensing
and communication. (Short range doesn’t necessarily matter.)
Given those assumptions, then sending a scout ship ahead of the main
vessel to investigate a potential star system could make sense. Not
the one-man fighters of TV space opera, of course, but a survey ship
equipped to take a good look at the target star system. Using local
stars as an example, if it would take your big vessel, say, six months
to go from, for ex, Alpha Centauri to Sol, or if it would require
colossal amounts of fuel or unobtainium or whatever to jump instantly,
but you could send a much smaller ship to Sol in a week, or jump it
there very cheaply, then a scouting mission might very well make sense
to see if Sol is worth visiting, safe to visit, or otherwise
interesting/scary.
(This of course incorporates a bunch of assumptions itself about why
you might be interesting in visiting Sol to begin with.)
But that led me to the question of what you could learn from a
distance before you sent your scouting mission, whether you could
learn enough at extreme distance to make a scouting mission
superfluous, etc.
You could learn a _lot_ about Sol itself at extreme distance, of
course.
Likewise, telescopic observation of Sol could reveal the existence of
planets at light-years of distance, or at least the existence and a
hint of the details about Jupiter and Saturn. With good enough
observations over a long period, you might be able to tag all the
planets, but I’m not sure what the practical limits of that would be.
(I’m neglecting the detection of Earth’s signals because they’re a
dead giveaway of something potentially important in the Sol System.
I'm not sure just how hard it would be to detect Earth’s artificial
signals at A Cent, but I’m sure it could be done with a big enough
receiver dish. The question is how big is big enough?)
The flip side of that would be the question of what such a survey ship
could be expected to learn once it arrived in the Sol System, and in
what amount of time. I picked the volume of the SSO because it’s a
widely known figure, it strikes me that it might make a reasonable
approximation of a small scouting craft, big enough to carry some
instrumentation and a crew that knows how to use them [as opposed to
the silly TV show trope of the one-might fighter as a scouting
mission :roll: ].
I’m assuming that they’re limited to real-universe light-speed and
slower phenomena for this.
Anyway, that was my chain of thinking that led to the original
question.
Jack Bohn
>A better use for even a small nuclear warhead would be to detonate it
>in an atmosphere of interest to get emission spectra.
"Nitrogen, oxygen, partially-burned hydrocarbons... I would say there
is a technologically advanced civilization down there... or, rather,
there WAS a technologically advanced civilization down there."
--
-Jack
Suzanne Blom
Except that I really suspect partially burned hydrocarbons are some sort
of intermediate stage on the way to a technologically advanced civilization.
John F. Eldredge
It all depends upon how advanced your minimum threshold is. You will
also have some minor degree of partially-burned hydrocarbons as long as
the sapients in question enjoy cooking meat over a fire. At the low end
of the spectrum that will be because they lack other cooking methods; at
the high end, that will be because they enjoy the taste.
Dr J R Stockton
21 Dec 2010 21:39:57, John F. Eldredge <jo...@jfeldredge.com> posted:
>It all depends upon how advanced your minimum threshold is. You will
>also have some minor degree of partially-burned hydrocarbons as long as
>the sapients in question enjoy cooking meat over a fire. At the low end
>of the spectrum that will be because they lack other cooking methods; at
>the high end, that will be because they enjoy the taste.
>
Partially-burned hydrocarbons also occur naturally on Earth,
independently of anthropic effects, because of the presence of ignition
sources (volcanors, lightning) and combustible material.
--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05 IE 8.
Web <http://www.merlyn.demon.co.uk/> - FAQ-type topics, acronyms, and links.
Command-prompt MiniTrue is useful for viewing/searching/altering files. Free,
DOS/Win/UNIX now 2.0.6; see <URL:http://www.merlyn.demon.co.uk/pc-links.htm>.
John F. Eldredge
> In rec.arts.sf.science message <8ncl5d...@mid.individual.net>, Tue,
> 21 Dec 2010 21:39:57, John F. Eldredge <jo...@jfeldredge.com> posted:
>
>>It all depends upon how advanced your minimum threshold is. You will
>>also have some minor degree of partially-burned hydrocarbons as long as
>>the sapients in question enjoy cooking meat over a fire. At the low end
>>of the spectrum that will be because they lack other cooking methods; at
>>the high end, that will be because they enjoy the taste.
>>
>>
> Partially-burned hydrocarbons also occur naturally on Earth,
> independently of anthropic effects, because of the presence of ignition
> sources (volcanors, lightning) and combustible material.
True. I had been thinking in terms of animal fats from grilling, but any
forest fire would release partially-burned hydrocarbons as well from
plant resins. A planet on which there had never been life would probably
have a lower hydrocarbon content, but some of the theories for how oil is
formed state that no biological content is needed.