How to contact another solar system

This is from space.com today. So why aren't we doing this?

Cheap Communication Schemes for ET

By Seth Shostak
Senior Astronomer, Project Phoenix
posted: 07:00 am ET
01 April 2004



When it comes to signaling across space, power is paramount.

Project Phoenix, which just wrapped up nine years of observations, was
an acutely sensitive search for radio broadcasts. The experiment could
have discerned an alien signal that was wafting a mere
0.00000000000000000001 watts onto the Arecibo telescope's Cyclopean,
twenty-acre aluminum mirror.


I'll state the obvious: that's a small number. Indeed, if that
incoming energy were collected for the length of time from the Big
Bang until today (that is to say, for all time), the total would only
be enough to blink a flashlight for a thousandth of a second.

Still, if you work out what sort of effort is required to produce that
pipsqueak signal, the numbers get large. At 100 light-years distance,
and assuming that the aliens are broadcasting in all directions
equally, our cosmic buddies would need to pump their transmitter with
100 billion watts in order to drop that miniscule amount of power onto
the Arecibo dish. That's more than produced by all of America's
electric utility plants.

Of course, the extraterrestrials could be clever about their attempts
to signal. For example, a rotating antenna might target only the flat
part of the Milky Way Galaxy, sweeping it like a lighthouse beacon and
doing so with considerably less juice than would be required by the
all-sky, all-the-time approach. Another scheme would be for the aliens
to use antenna arrays that sequentially "pinged" only interesting star
systems. Again, this would save on the electric bills.

Still, there's no doubt that any of these transmitting schemes would
be big-time undertakings, involving large structures, hefty
electronics, and gobs of power.

But let's consider what would be required to get in touch using a
laser, one that communicated with very short pulses of infrared light.
Again, if the aliens are 100 light-years away, and are using a "bare
bulb" approach that flashes light in all directions, we could discern
these pulses if the transmitters could manage an average power of 100
billion billion watts, assuming that they are content to send only a
modest 100 bits per second of information and that we are observing
with a relatively small, college-grade telescope.

That's such a daunting power drain that it's safe to say even advanced
societies for whom power bills are no object would eschew the cost,
and use a mirror to focus their light sources in preferred directions.
For instance, they might limit their broadcast beam to a circle that's
the size of Jupiter's orbit, on the reasonable assumption that planets
able to produce intelligent beings would lie within that distance from
a Sun-like star. The mirror required to do this (again, with infrared
light) would be roughly 20 feet across, which is hardly a challenge.
Using the mirror reduces the power requirement to approximately 10
million watts.

However, there's the bugaboo that we might not be looking when the
aliens are flashing. SETI researchers have given thought to this
"synchronicity" problem, and come up with ingenious (if uncertain)
schemes that might ensure that we are receiving when the
extraterrestrials are sending. One approach, variously proposed by Tim
Castellano (NASA), Ray Villard (Space Telescope Science Institute),
and yours truly, is to assume that some ambitious alien astronomers
using the transit technique have detected Earth. In other words, they
have found our world because it blocks a small amount of light as it
passes in front of the Sun as seen by them. This once-a-year eclipse
is an event that both we, and any extraterrestrials who have observed
it, will know. They might choose to send their laser flashes in our
direction during these transits, on the assumption that we were clever
enough to figure out the synchronization scheme.

Of course, this requires that the aliens have precise knowledge of the
distance to our solar system, and the Sun's motion through space. For
an advanced society, that might not be too much to ask. But the kicker
is this: they will know that, during the transit, our world is
somewhere in front of the Sun's disk. So they could use a mirror array
to focus their signal on that disk, thus reducing the power
requirements for signaling to less than 10 watts, comparable to a
bicycle headlamp! Yes, the mirror would now be a mile across, but it
could be made up of a few small, cheap, and simple individual
reflectors.

In other words, with a collection of mirrors, a small laser, and a
computer to run it all, a knowledgeable and entrepreneurial
extraterrestrial could produce detectable signals with only as much
power as a handful of batteries could supply. No mammoth antennas, and
no beefy transmitters are required. The broadcast could be an alien
science fair experiment.

It's interesting to imagine that attempts by extraterrestrials to
locate other intelligence in the Galaxy might be made not by
officialdom in massive societal programs, but by the personal efforts
of the young and the daring.

(Steve Dufour) wrote:

This is from space.com today. So why aren't we doing this?

Probably because it's a day later than the mandatory
brain-befuddling April-Fool's cascade.

I'm sure that for the cost of a small laser, a PC and
some optics, that you could quite happily get on with
the job without help from anyone else.

Ask Rev. Moon, I'm sure he has all the answers you
seek.

S
--
Remove the Zees to Reply...

This is from space.com today. So why aren't we doing this?

Probably because it's a day later than the mandatory
brain-befuddling April-Fool's cascade.

It was dated April 1!

I'm sure that for the cost of a small laser, a PC and
some optics, that you could quite happily get on with
the job without help from anyone else.

What if you put a powerful laser somewhere on the Earth's equator
pointing up? Wouldn't it have the effect of sweeping the Galactic
Plane that the article mentioned?

Steve the best way to contact intelligent life is to put notes inside
bucky balls. Send out a trillion at a time in rthe direction across our
galaxy. EM signals are a wast of time. Bert

In article ,
Steve Dufour wrote:
I'm sure that for the cost of a small laser, a PC and
some optics, that you could quite happily get on with
the job without help from anyone else.

What if you put a powerful laser somewhere on the Earth's equator
pointing up? Wouldn't it have the effect of sweeping the Galactic
Plane that the article mentioned?

Yes, once it got through the atmosphere. Better to put it in geosync
orbit, with a large solar array or several for power.


Gary

--
Gary Heston

Contrary to popular opinion, _not_ everyone loves Raymond.

What if you put a powerful laser somewhere on the Earth's equator
pointing up? Wouldn't it have the effect of sweeping the Galactic
Plane that the article mentioned?

Most places on the equator get lots of rainy days.

James Nature has invented objects in the universe that eject Laser
beams. My idea of using the hollow interior of a bucky ball is like the
way we find notes in bottles that have floated on our vast oceans for
many years. Bucky balls are very strong,and have been found
around craters showing they can take the impact of hitting the Earth at
great speed. Seeing inside a bucky ball with a structure of 60 atoms
takes a electronic microscope,and only an advanced life form would have
one. Bert James I have a few inventions please email me

"Steve Dufour" wrote in message om...

What if you put a powerful laser somewhere on the Earth's equator
pointing up? Wouldn't it have the effect of sweeping the Galactic
Plane that the article mentioned?

'Lo Steve --

Are you certain that Earth's equatorial plane is the same as the galactic
plane? I think i read somewhere that both the equatorial plane and the
ecliptic are quite a few degrees *off* the galactic plane.

I suppose all one has to do is to compare the Milky Way with the
equatorial plane?

--
Sittin' on the porch stair holdin' your love,
A wonderin' how lucky you are,
A huggin' anda kissin' anda lookin' up above--
There went a Shootin' Star!

Indelibly yours,
Painius

Painius wrote:

"Steve Dufour" wrote in message om...

What if you put a powerful laser somewhere on the Earth's equator
pointing up? Wouldn't it have the effect of sweeping the Galactic
Plane that the article mentioned?

Are you certain that Earth's equatorial plane is the same as the galactic
plane? I think i read somewhere that both the equatorial plane and the
ecliptic are quite a few degrees *off* the galactic plane.

Yes, the two planes form an angle of something like sixty degrees:
nowhere near the same.

--
Odysseus