G'day guys,
Two quick questions.
1) How much do you really think FTLing knocks you around? I was just thinking
about the HRH of the NAC splitting their time between the seats of power and
it struck me if its too rough you may not see kids joining them etc... could
also make a good scenario... escort the new royal home and don't let anything
"rock the boat" so to speak.
2) You'd see the same constellations if on a plant in the same solar system,
but how different would the constellations look if I went to Alpha Centuari
(i.e. close so not so different in some respects, but still not the same solar
system)?
Cheers
> Beth.Fulton@csiro.au wrote:
> G'day guys,
Absolutely no idea.
> 2) You'd see the same constellations if on a plant in the same solar
The page at Winchell Chung's 3D star-mapping site has some info on
figuring this sort of thing out:
http://www.projectrho.com/smap05b.html
This page (indeed, the entire site) has more math than I like to consider at
2am. Fortunately, he has links on this page and others to an astonishing array
of star mapping programs. Some of them let you move your viewpoint around so
you can get an idea of what the night sky looks like in other star systems.
> Beth.Fulton@csiro.au wrote:
> G'day guys,
Still no idea.
> 2) You'd see the same constellations if on a plant in the same solar
This page:
http://www.wlsc.wvnet.edu/~onealdb/articles/sunother.html
seems to have a pretty good description of what the differences would be.
G'day Ray,
> Still no idea.
;)
> This page:
Thanks
> Beth.Fulton@csiro.au wrote:
John Leary wandered off topic: Navigation well most likey be done by using at
least three known pulsars to determine location in space. Kind of like looking
at 'lighthouses' in the stars.
No pulsars close by, are there? I'd like we'd use nearby bright stars
eg Sirius--the closer they are, the easier it is to judge your exact
position. (If you're trying to get the right driveway, you might estimate from
the
end of the block--not from the Eiffel Tower, as even though it stands
out well, it's a bit too far away).
> "laserlight@quixnet.net" wrote:
Nice analogy, but for space navigation, doesn't quite work. Star brightness is
irrelevant to distance, so if you pop into an unknown area of space, it won't
work at all trying to figure out whether that bright star you see is nearby
and not. Pulsars much better option. They are far enough away that they are
unlikely to move too much wrt the rest of the stuff around you. That or other
unique objects that are easily identifiable from different angles. Three is
good. More is
better. :-)
Quoth I:
> No pulsars close by, are there? I'd like we'd use nearby bright stars
Quoth Indy:
> Nice analogy, but for space navigation, doesn't quite work. Star
I was thinking of triangulating from multiple stars. Pulksars would be more
idetifiable, I suppose, especially if you're travelling long distances. Siruis
is not going to hard to find in you're in
human-occupied space in the GZG verse, though is it? Call it 20 parsecs
or so.
> "laserlight@quixnet.net" wrote:
20 parsecs is a lot! 64+ lightyears. Sirius is going to dim noticeably
in that distance. At 10 parsecs Sirius is a 1.4 mag star. Double the distance
and it is going to get Sirius-ly lost in all the other stars. You can
calculate it out (oops! WARNING!! math formula approaching!!!) by plugging in
the numbers:
m = M - 5 + 5 * log (d)
Where M is the absolute magnitude (1.4 in the case of Sirius), d is the
distance in parsecs, and m is the apparent magnitude.
The next problem would be trying to determine what stars around you are
"nearby", and how you would go about doing that. The most
straight-forward
way would be parallax by taking measurements from 2 widely seperated
locations. That involves (usually) taking a measurement, moving the ship
somewhere (like 1 AU or more is good), taking another measurement, then
calculating. The moving thing is going to take all your time. And if you are
pressed for time, or rather immobile...
G'day,
> Siruis is not going to hard...
1) Doesn't star brightness change with distance?
2) As the resident nation of Sirius on Nyrath the Great's "noncannon nations"
map, the IAS would like to know how you use the method when you're at Sirius?
;)
G'day John,
> Hi Beth,
Cool.
> Have no fear, the human mind will develop local
I was actually wondering how weird it would look from a nearby planet. Aussies
would obviously feel a little disconcerted if they were sitting on a planet
around Alpha Centuari as there would be no "pointers" (you'd be sitting on
one), but I was just wondering how different it would all look, or would there
just be little odd bits? Ray's link says there would be odd bits (due to our
Sun being up there too), the one bit I hadn't clicked to would be that the Sun
would fit into a different constellation depending on which star system you
travelled to.
> Slightly off the subject of your post..
I'll take your word on that;)
I'd have to say your Eiffel tower analogy is very flawed...
A simple, and modern, example is GPS. Something (relatively) far away, and
used every day to predict where on earth (and near Solar system as well!) you
are. I personally have used a GPS unit to determine where I'm going, where
I've been, and where the hell I am right now. They're a
Hiking/Camper's dream! No more getting lost for 8 days in a mountain
range for me, thank you very much. Not my fault, rockslides can happen at any
time, for any reason, and I happen to be _lucky_ it didn't happen when I
was crossing through the pass.
AFAIR, Pulsars have individually distinctive revolutions per time unit, and
with over 700 known to us now, you could get a _very_ accurate position
from almost anywhere.
As to brightness of stars... How do you know star X is Sirius? What
distiguishes it from star Y? Brightness? That's like saying the light in front
of house X is brighter than the light in front of house Y... It does depend on
where you're at, but if I blind fold you, spin you around, plunk you down in a
random point in a subdivision, how're you going to use light brightness to
figure out where you are?
Rand.
> At 02:59 PM 2/21/02 -0500, you wrote:
> --- Beth.Fulton@csiro.au wrote:
Hi again Beth, Thank you for your kind support!
On the other hand, I did start an 'intense discusion'
of navigation in the FT universe. I have not been
able to do that for some time now.
Bye for now,
> On Fri, 22 Feb 2002 Beth.Fulton@csiro.au wrote:
Hey, Beth
> > Have no fear, the human mind will develop local
Well, the further away you get from Sol the more and more distorted the
constellations you are familiar with are are going to look. I couldn't tell
you exactly how what is going to look how depending on which way you go. There
are people who have done this to some degree. But it's vastly complex and
difficult to explain into words how things would look from a given star system
on the fly.
The stars that make up constellations are at vastly different distances
from us - some relatively nearby (Sirius at 8.7 ly, Altair at 16 ly,
Vega at 25 ly), others substantially further (Betelguese at 520 ly, Deneb at
1600 ly). As soon as you move any significant distance, the sky starts to
really change from what you were used to seeing.
> > Slightly off the subject of your post..
Each pulsar's "pulse" is unique into and of itself, sort of like fingerprints
are to a person. So if you have a bunch of these
charted into your astro-database, and you can relocate these pulsars
after an FTL jump, you can fix your position pretty darn accurately.
> I'd have to say your Eiffel tower analogy is very flawed...
:-) You would be wrong...It is easier to see a change in position
relative to a landmark which is close by, rather than one farther away.
However, I'm not saying pulsars may not work. I don't know how easy it is to
distinguish eg Sirius, Altair, Sol from the other stars around, and the
distinctiveness of pulsars may be the key factor.
Quoth Indy:
> The next problem would be trying to determine what stars around you are
I wouldn't bother with that, just use the same identifiable stars...if they're
identifiable. They's the key question. Are spectra unique, like voiceprints?
Or is Sirius going to look pretty much like any other star of its general type
(A2, IIC)?
That's the problem... Pulsar's are unique and identifiable. IIRC, Stars
aren't.
> "laserlight@quixnet.net" wrote:
> Quoth Indy:
That's flawed rhetoric on top of a flawed analogy. Rhetoric fallacy: Just
because A is easier than B, does not mean C is easier than D. Apples and
Oranges. Rhetoric fallacy2: Just because something is true for you, does not
make it universally true. (I have brown hair. Therefor every human must have
brown hair.)
Analogy fallacy 1, apples and oranges: The Effiel tower is equally effective
as a landmark for navigation as any other. It's the means you use. since
you're "estimating" then a short hand method is probably acceptable. But for
navigation, where accuracy is critical (ask anyone who's ever thought about
navigating minefields about the importance of accuracy in both placement of
the mines, of the reporting of the placement, and of your movement) anyway,
for navigation, you want accuracy.
Analogy fallacy 2, unnaturally narrowing choices: Assumption that
sight, human non-enhanced specifically, is the only means to judge with.
With a simple range-finder, anything within range is a good navigation
point.
Analogy fallacy 3, assumption: If the right driveway, and/or the end of
the block are either not visible to you directly, OR at large distance
away, then how does your analogy stand-up?
Still want to tell me I'm wrong, and your analogy isn't flawed? Rand.
> "laserlight@quixnet.net" wrote:
> >I'd have to say your Eiffel tower analogy is very flawed...
However, I'm not saying pulsars may not work. I don't know how easy it is to
distinguish eg Sirius, Altair, Sol from the other stars around, and the
distinctiveness of pulsars may be the key factor.
> --------------------------------------------------------------------
> Randall L Joiner wrote:
Dude, you need to chill out a little... this is a friendly mailing list, not a
dick size war...
> Rick Rutherford wrote:
Now, wasn't it our own Jon T who posted the joke about condoms
from WWII?? ;-) ;-)
Spectra are unique, they are formed by different amounts of various elements
that produce more of one color when burned. A problem arises when dust,
hydrogen or nebula are in the way as they might absorb parts of the spectra,
reducing the usable parts and making ID more difficult.
You would determine range to a star the same way astronomers currently do. How
do you think they know Alpha Centauri is 4.3 light years away?
--Binhan
> -----Original Message-----
> B Lin wrote:
Parallax. But again, you run into the whole travelling from point A to point B
in order to get that parallax thing, and how long it'll take.
> That's flawed rhetoric on top of a flawed analogy.
If it weren't a reasonable analogy, then you would be correct.
> Rhetoric fallacy2: Just because something is true for you, does not
I think you're taking a roundabout way to say "but what if you live close to
the Tower?" If you happen to live close to it, then it may
very well be useful--in that case, substitute "a landmark 5000km away."
I wasn't aware that any Listers lived in or near Paris, though.
> Analogy fallacy 1, apples and oranges: The Effiel tower is equally
Not true. It is only as effective as any equally visible landmark at a similar
range.
> Analogy fallacy 2, unnaturally narrowing choices: Assumption that
With a simple range-finder, anything within range is a good navigation
point.
You are quibbling about an argument that I haven't made. I'm not talking about
measuring range to anything, I'm talking about triangulation.
If there is a precise method of determining range across interstellar
distances--other than by parallax, ie triangulation--I'm not aware of it
(which doesn't mean there *isn't* one, of course). The closer you are to an
object, the more apparent displacement there will be when you (or it) move. A
large displacement is easier to measure than a small one.
> Analogy fallacy 3, assumption: If the right driveway, and/or the end
If I had put "block that you're on, and the end of which you can see", would
you be happy? Or would I need to add more fine print to say "and this block is
not subject to mirages, holo projections, illusions, space time distortions,
etc"?
> Still want to tell me I'm wrong, and your analogy isn't flawed?
Yes, but I won't :-) JohnA is away, and I'm sure the List has no
desire for a stand-in.
> B Lin wrote:
Parallax ie triangulation. Works well on nearby stars, not so well on distant
objects. Actually there are other methods astronomers use on more distant
stars, about which Indy could probably go on at much greater length than I.
Some numbers regarding GPS and using pulsars in the same way.
A good GPS can fix your position to about 1 meter. Assuming most satellites
are 11,000 miles (17.6 thousand klicks) then you get an
accuracy of plus/minus 0.006% (1 meter of error per 17,600,000 meters).
If a pulsar is 100,000 LY away, your error is going to be 568.2 LY. If it's
10,000 LY then the error is only 56.8 LY.
GPS gets this accuracy from three sources - the receiving station is
kept on time by auto-correcting from 4 signals. If there is error in
the receiving unit, the apparent location of the receiver will not form a
single point, but show 4 possible points. The receiver tries to find a single
correction value that makes the 4 points combine into one.
This internal, self-correction keeps the receiver on "atomic time"
without having to have an actual atomic clock.
The second source is that it knows the exact position of the satellite at any
given time. An almanac is generated to predict the exact position of the
satellite at any given time. Due to small disturbances due to the Sun, Moon
and other large bodies, this acutally varies slighty. Ground stations using
highly accurate radar to constantly monitor the position of each satellite.
The actual position is then transmitted up to the satellite and incorporated
into the signal that each one sends out so that each receiver can make the
appropriate corrections.
The third source is signal delay correction. Light/radio waves travel
at 186,000 miles per second - IN A VACUUM - interference with the
atmosphere (ionizing radiation and such) can reduce the signal speed by a few
nanoseconds. Signals from different satellites might pass through different
conditions, which means there is no single correction factor. Ground stations
are used that are relatively close, and thus would be likely to see the same
errors from the satellites. The ground stations
operate in reverse - they have a known position, they know what the
timing of the signal should be, the measure the incoming signal and determine
how much off it is. They then send this correction to the GPS receiver
(through normal radio channels, not the GPS signal)
One other issue is that the signal from GPS satellites is highly coded
into a pseudo-random signal. It is a complex signal with no repeating
sequences (which allows you to know that the signal you are getting now is not
the same one that occured a second ago) and it also encodes infomation about
the satellite's position.
> From these details, I find it hard to believe that using pulsars will
Some food for thought.
From: <laserlight@quixnet.net>
> :-) You would be wrong...It is easier to see a change in position
> On Fri, 22 Feb 2002, laserlight@quixnet.net wrote:
> B Lin wrote:
There are, I could, but sitting at home trying to type anything "lengthy" in
at 2400bd ain't high on my list of finger exercises
this evening. ;-)
Trigonometric parallax is good out to about 100 parsecs. After that, at this
time, it falls off rapidly in accuracy (as technology gets
more refined, though, it will slowly expand - when, how, etc I couldn't
begin to tell you ;-). However, it's the most straight-forward of
the various methods used.
Using combinations of spectra and mass/luminosity a rough idea of the
absolute magnitude can be derived, and from the equation I posted in an
earlier message, the distance approximated (you'll note that for most stars
100 parsecs or further away have round numbers for their distances; e.g.,
Betelgeuse is listed as 520 ly as opposed to, say, 512 or 531 ly).
Other methods involve using special classes of variable stars, such as RR
Lyrae and Cepheid variables. From these extremely
regular variable stars one can use period-luminosity relations
in order to determine distances. These are *generally* used for determining
distances to entire galaxies, rather than individual stars (since you would
only be measuring them, not
other, non-variable, stars).
Okay, I stop here before I get "lengthy". ;-) Have a good
evening (or morning, or afternoon, or...)
*nod* You're right. *sigh* I respond poorly when arrogance and ignorance are
mixed in my general direction.
> At 02:47 PM 2/22/02 -0500, you wrote:
Rick "Bulletproof" Rutherford enjoined:
> >Dude, you need to chill out a little... this is a friendly mailing
Randall L Joiner sniped:
> *nod* You're right. *sigh* I respond poorly when arrogance and
oops! I was aiming to achieve ignorance and *apathy*...but who cares?
[quoted original message omitted]
G'day,
> On the other hand, I did start an 'intense discusion'
Anytime a dumb question of mine can help you just give me a call;)
> The original Voyager "To Occupant" message used Pulsars and
IIRC I specified 20 parsecs diameter for HM space, which is why I wasn't
discussing about the "area code." I agree that if you didn't know what part of
the galaxy you were in, pulsars would be the first step in narrowing it down.
Although if you're that badly lost, you might need to look for angelic
visitation before you look for pulsars.
> someone wrote:
... so when we Earthlings finally make it to the nearby stars, we're going to
find lots of empty planets, until we get to Sirius... then
we'll suddenly find a half-dozen (or so) different alien starships,
all waiting for us to show up!
Heh heh heh... "Dinner is served"...
> At 02:07 25/02/02 -0500, Rick wrote:
Aliens who are humanitarians just like some people are vegetarians:)
Cheers