using the sun and shade(s) - - to send morse code messages across the galaxy

using the sun and shade(s) - - to send morse
code messages across the galaxy. Any thoughts anyone?

I know nothing about mirrors, but could one have a million small
"one-way" mirrors (like the police use in interrogation rooms)
orbiting a star - - and then rotate them so as to alternate blocking
and then letting pass the sunlight ???

Alex William Russell wrote:
using the sun and shade(s) - - to send morse
code messages across the galaxy. Any thoughts anyone?

Using the sun gives one something to work with, rather than having to
generate energy for a laser or radio.

For maximum return on one's investment, could one dump some material
to serve as a catalyst in a limited system, and either - - - 1)
temporarily flare the sun on command by satisfying the need for a
scarce element in the "fusion process" - - or 2) dump metals upon
which sunspots might form and dim the sun - - - or 3) simply nuke the
surface of the sun to stir things up to maybe elevate temporarily
light output ???

Ah, but all of these -- or any method that would shade or intensify
the Sun -- require energy input. (How are you going to, for example, get
materials to dump into the Sun? Use a rocket? Doesn't it take energy to
build the rocket and send it into the Sun?) Now, the crucial question is,
do you save energy by plugging in a laser, or by exepnding the energy
necessary to modulate the Sun's apparent intensity to a noticeable degree?
--
-- With Best Regards,
Matthew Funke )

"Christopher M. Jones" wrote:

Doesn't even have to be fully on/off, nor intentional.

Oh, I certainly wouldn't disagree.

The subject of the rest of your post was very compelling.



--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

Alex William Russell wrote:
using the sun and shade(s) - - to send morse
code messages across the galaxy. Any thoughts anyone?


I know nothing about mirrors, but could one have a million small
"one-way" mirrors (like the police use in interrogation rooms)
orbiting a star - - and then rotate them so as to alternate blocking
and then letting pass the sunlight ???

Those 'one way mirrors' don't work quite that way. But mirrors that
turn edge on to let light pass would in princible work. A whole heap
lot of mirrors.

"Henry Spencer" wrote:
In article ,
Alex William Russell wrote:
Using the sun eliminates the need to use massive lasers, radios, etc.,
so maybe it's the only way to go.

You don't actually need that huge a laser for interstellar communications,
as it turns out. The low beam divergence greatly increases the effective
power, and the extremely narrow band makes detection a lot easier.

Reusing the "old" and now well worn BOTE calc. I did several
months ago, given reasonable near future technology a figure of
well below 30 transmitted Joules per received bit over 10 ly
would be very achievable (e.g. 30 kW / kilobit/s). If you're
talking what would reasonably be possible in, say, 2030 maybe
(excluding the interstellar travel bit, of course), then lop
off a factor of 10 to 100 (e.g. circa 1 J / bit over 10 ly, or
less). Plus, it's a simple matter to double the transmitters
and double the combined bandwidth (and a fairly simpler matter
to configure one receiver to be able to receive multiple data
streams from the same location).

I'd like to follow up some on my previous points.

One thing I'd especially like to point out is that the
instruments which will come online in even the next decade
or so (not to mention improvements after that) there will
be several different ways of detecting large (planet sized)
objects in extra-terrestial systems. Some of them will, as
now, detect masses, others, however, will detect *sizes*.
I think that's an important point, because the ability to
build something the mass of the Earth (or even the Moon) is
quite a lot different than the ability to build something
the *size* of the Earth or the Moon. Especially since
mostly we're just talking cross-sectional size, so that
sets up a whole different degree of scaling. Even more
importantly, the increasing sensitivity of "planet"
detection systems will increasingly favor detection of
large rather than massive objects. Increase the
sensitivity of a mass detection system (doppler velocity,
astrometric) by many orders of magnitude and the amount
of mass is still huge (1/10,000th the mass of Jupiter is
the mass of the Moon). But increase the sensitivity of
size detection systems (precision photometry, deep nulling
imagery) by the same amount and the problem becomes
within the realm of possibility for technological
civilizations only moderately more advanced than ours
(1/10,000th the the area of the Earth is 128,000 km^2,
which is a lot, but our rate of "area production" for
manufacturing structures not even optimized for such is
high enough to make a project designed to create an
object with that area (even in space) just a, decently
reasonable, matter of time and money).

One specific example I can think of is a very large
"movable" sunshade. You'd want it to be as large as
possible, in as close an orbit as possible to the
parent star (this helps) and capable of changing the
amount of light it blocks from its parent star by as
much as possible (i.e. making the possible variance in
light blocked as great as possible, such as between
the sunshade blocking all light over its maximum area
and blocking none). Changing the degree of blocking
might be tricky, considering the scales and masses
involved, but controlling the rotation and thus the
angle of the sunshade relative to the star ought to do
the trick. Then, it would be a "simple" matter of
modulating the sunshade's blocking over successive
orbits to create a signal. The low orbit helps for
several reasons. First, it helps increase the angle
of offset from "edge on" from which full transits
would be viewable (though it won't increase the
magnitude of dimming for such transits). Second, it
will decrease the time between transits, which aids
detectability (if that's what you're going for) as
well as bit rate.

The main advantage of this method of communication over
other forms of achievable interstellar communication
would be that it transmits into a "slice" of the sky
(imagine two very shallow cones attached at the apex,
the "reception volume" would be in the space between
the two cones (which would be a pretty shallow angle,
maybe 10 or 20 degrees, maybe more, out to whatever
distance). If you're just wanting to broadcast to the
galaxy then you'd probably want to align the sunshade's
orbit with that of the galaxy. I'd imagine the tricky
part might be ensuring that you kept the modulation
such that it enhanced early detection (attracting
attention to, and thus further monitoring of, the
system) without hurting the bitrate too much. In other
words, if you just broadcast data constantly then the
signal will look mostly like random brightness
fluctuations with a certain period, and that might not
attract as much attention as something mimicking a
planetary object to some degree. Perhaps you could
use two systems in similar orbits, a static one which
says "hey, watch this sytem! I look like a planet!" and
another which broadcasts data via modulation.

Alternatively, a similar system using scattered rather
than blocked sunlight (using a "matte" finish solar sail,
perhaps?) would also work, and would probably have a
larger angle of detectability, plus being closer to the
parent star *would* increase the signal strength.

using the sun and shade(s) - - to send morse message

To try to salvage the idea of simply blocking sunlight to message
(lasers do seem to be better choice according to everyone), how about
setting up 1) sun orbiting satellites in efficient close orbit (just
far enough so they don't melt) 2) designed to be of large area 3) with
power (and structural strength) to rotate to alternate between
blocking sunlight and letting it pass edge-wise, 4) built in
sufficient number so that they form a half-dyson-sphere every orbit (a
"h-d-s"), with 5) their orbits designed so all are on one side of sun
at same time - - at which time they either block or let through the
sunlight, thus making a cheap-to-operate binary signalling device
available every orbit forever and ever (or until orbits decay).