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A of E author in alien light signal detection project
W
Winfield Hill
Leon wrote...
Only "involved"? It's Paul's newest oseti project.
http://seti.harvard.edu/oseti/allsky/ - also see
http://seti.harvard.edu/ and http://seti.harvard.edu/oseti/
The new telescope with its 1024-PMT sensors and
400MHz digitizing electronics had been more than
seven years in the planning and making. Its web
pages are a few years out of date at this point;
no doubt because since then all the hard work has
gone into finishing the electronics and software.
The flood of news now comes from his April 11th
first-light ceremony at the telescope.
Most of the funding is from the Planetary Society,
http://www.planetary.org/about/press/releases/2006/
0411_Planetary_Society_Opens_Worlds_First.html
Only "involved"? It's Paul's newest oseti project.
http://seti.harvard.edu/oseti/allsky/ - also see
http://seti.harvard.edu/ and http://seti.harvard.edu/oseti/
The new telescope with its 1024-PMT sensors and
400MHz digitizing electronics had been more than
seven years in the planning and making. Its web
pages are a few years out of date at this point;
no doubt because since then all the hard work has
gone into finishing the electronics and software.
The flood of news now comes from his April 11th
first-light ceremony at the telescope.
Most of the funding is from the Planetary Society,
http://www.planetary.org/about/press/releases/2006/
0411_Planetary_Society_Opens_Worlds_First.html
R
Rene Tschaggelar
Leon said:
72 inches is a rather tiny mirror for such
an ambiguous project. And I'd have had expected
a microchannel plate in front of a higher
resolution CCD array.
Rene
W
Winfield Hill
Rene Tschaggelar wrote...
Did you mean ambiguous or ambitious?
A 6-foot mirror can gather plenty of light - and it's
larger than the first oseti experiment, which suffered
more from having only two PMTs than from mirror size.
A PMT can do a fine job of grabbing single photons.
In this case each of Paul's 1024 PMTs will distinguish
between one, two, three, etc, or more photons, in the
expected all-photons-at-once pulses one would get from
an artificial pico-second laser flash. Furthermore, a
similar intense pulse must be seen by a second set of
PMTs observing the same light flash via a beam splitter.
After this multi-photon nanosecond-scale PMT pulse there
must be only background light, which consists of modest
photon rates. No natural source of light has such a
signature. The basic scheme has been proven in years
of use, see the detailed physics papers on the website.
http://seti.harvard.edu/oseti/
Did you mean ambiguous or ambitious?
A 6-foot mirror can gather plenty of light - and it's
larger than the first oseti experiment, which suffered
more from having only two PMTs than from mirror size.
A PMT can do a fine job of grabbing single photons.
In this case each of Paul's 1024 PMTs will distinguish
between one, two, three, etc, or more photons, in the
expected all-photons-at-once pulses one would get from
an artificial pico-second laser flash. Furthermore, a
similar intense pulse must be seen by a second set of
PMTs observing the same light flash via a beam splitter.
After this multi-photon nanosecond-scale PMT pulse there
must be only background light, which consists of modest
photon rates. No natural source of light has such a
signature. The basic scheme has been proven in years
of use, see the detailed physics papers on the website.
http://seti.harvard.edu/oseti/
P
Paul Hovnanian P.E.
Winfield said:Rene Tschaggelar wrote...
Did you mean ambiguous or ambitious?
A 6-foot mirror can gather plenty of light - and it's
larger than the first oseti experiment, which suffered
more from having only two PMTs than from mirror size.
A PMT can do a fine job of grabbing single photons.
In this case each of Paul's 1024 PMTs will distinguish
between one, two, three, etc, or more photons, in the
expected all-photons-at-once pulses one would get from
an artificial pico-second laser flash. Furthermore, a
similar intense pulse must be seen by a second set of
PMTs observing the same light flash via a beam splitter.
After this multi-photon nanosecond-scale PMT pulse there
must be only background light, which consists of modest
photon rates. No natural source of light has such a
signature. The basic scheme has been proven in years
of use, see the detailed physics papers on the website.
http://seti.harvard.edu/oseti/
Interesting. But it would be a real shame if this detector was only just
sensitive enough to pick up the photon signature of distant
civilizations as they annihilated themselves in one final planet-wide
thermonuclear war.
T
Tim Williams
Paul Hovnanian P.E. said:
PMTs and mirrors don't pick up X or gamma rays. ;-)
Tim
W
Winfield Hill
Paul Hovnanian P.E. wrote...
Indeed, but Paul's telescope's oseti-processing is tuned to
intentional very short high-power laser pulses, and would
therefore ignore the optical signal from such an event. The
telescope electronics does have an "astronomy" channel which
might see some of a large explosion, but even so its single
photon-at-a-time nanosecond pulse-intensity processing engine
would become overwhelmed, and ignore most of such a signal.
For example, the photon flood from a nearby lightning strike
would not be confused with the sub- to few-nanosecond pulses
Paul's telescope's electronic processing is looking for.
Imagine an advanced civilization that hasn't blown itself up.
They're rich and a bit bored. Interstellar distances are too
large to travel to other stars, or at least beyond the close
ones, so they spend some time and money on an interstellar
communication channel. Assuming such civilizations are out
there and have made the transmitters, why not listen in? In
early seti research it was assumed radio communication would
be used. But now that we know how to make the appropriate
lasers, it's clear that high-power pulse laser communication
is much better (each pulse outshines the adjacent sun) and
would be used, hence the new field of oseti, optical seti.
Indeed, but Paul's telescope's oseti-processing is tuned to
intentional very short high-power laser pulses, and would
therefore ignore the optical signal from such an event. The
telescope electronics does have an "astronomy" channel which
might see some of a large explosion, but even so its single
photon-at-a-time nanosecond pulse-intensity processing engine
would become overwhelmed, and ignore most of such a signal.
For example, the photon flood from a nearby lightning strike
would not be confused with the sub- to few-nanosecond pulses
Paul's telescope's electronic processing is looking for.
Imagine an advanced civilization that hasn't blown itself up.
They're rich and a bit bored. Interstellar distances are too
large to travel to other stars, or at least beyond the close
ones, so they spend some time and money on an interstellar
communication channel. Assuming such civilizations are out
there and have made the transmitters, why not listen in? In
early seti research it was assumed radio communication would
be used. But now that we know how to make the appropriate
lasers, it's clear that high-power pulse laser communication
is much better (each pulse outshines the adjacent sun) and
would be used, hence the new field of oseti, optical seti.
J
James Waldby
Tim said:
Yes, I'm sure you're right ~ those X-ray mirrors in
XMM-Newton and Chandra must be just tinsel decorations.
http://en.wikipedia.org/wiki/Chandra_X-ray_Observatory
http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/technical/Mirrors/
-jiw
P
Paul Hovnanian P.E.
Winfield said:
That seems to be a reasonable assumption. If some advanced civilization
has created a target list of likely solar systems (those with planets
detected) and lasers with sufficiently tight beam width, the resulting
signal at each target would be much higher than that of omnidirectional
radiation (rf or optical) of the same power.
The interesting question becomes: What is the most probable signal
frequency (wavelength) they would use and we should look for? The
shorter the frequency, the tighter the beam width and efficiency
(received signal strength for a given transmitter power). Assuming no
limit to their technology (they can buy $4.99 x-ray flashlights at their
WalMart), the upper limit would be that which would give them a beam
width that would illuminate the orbital space of a solar system
considered habitable. Any shorter wavelength would be pointless. If
their astronomy is really good (ours is getting pretty good), they might
be able to tighten up their beam if they could predict orbital planes at
the time of arrival and focus on that volume. That would suggest a
shorter wavelength.
The other factor which would affect the wavelength question is which
parts of the spectrum would one select that have the lowest probability
of being mistaken for some natural phenomenon.
T
Tim Williams
James Waldby said:
Oh, neato. Didn't know x-rays bounced around stuff.
How about gamma then?
To my knowledge, PMTs don't work great with ionizing radiation, though.
That's a spectrum for a different detector.
Tim
As the bandwidth is reduced so the noise is reduced and less power
required.
As the frequency is increased so the directivitty is increased.
As the time taken for propogation is often thousands of yeares whats
the hurry.
Take 100 years to send a block busting video, ie bandwidth can be very
small.
Dont forget spread spectrum to give quasi narrow band as per GPS.
So many possibilities.
What about a planetry sized heleoscope i.e. wobble a big mirror in
orbit round a sun.
Lots of opportunity for the amateur just like early radio.
required.
As the frequency is increased so the directivitty is increased.
As the time taken for propogation is often thousands of yeares whats
the hurry.
Take 100 years to send a block busting video, ie bandwidth can be very
small.
Dont forget spread spectrum to give quasi narrow band as per GPS.
So many possibilities.
What about a planetry sized heleoscope i.e. wobble a big mirror in
orbit round a sun.
Lots of opportunity for the amateur just like early radio.
I
Ian Stirling
Winfield Hill said:
^known
K
Ken Smith
Sodium iodide is clear than glass. If you don't care about the color of
the "light" you can put a slab of it infront of the PMT and make something
at responds to gamma rays.
K
Ken Smith
Paul Hovnanian P.E. said:
The "mistaken for" would be less of an issue than the "lost in". You can
modulate the light in some way that would be obviously not natural but it
needs to have a reasonable SNR at the receiver.
R
Rich Grise
Then again, by the time they get so advanced to have an interplanetary
civilization, they might well have discovered telepathy or subspace
radio, or something we've never even dreamed of, which we don't know how
to receive yet. ;-)
Cheers!
Rich
P
Paul Hovnanian P.E.
Rich said:
A highly advanced civilization might figure out how to generate
wormholes (Einstein-Rosen Bridges) and cause one end to 'appear' at a
distant location. Not the big ones that science fiction novels propose
which an invading alien army could pass through (physics shows that too
much energy would be required) but one just large enough for a photon to
get through.
At our end, we wouldn't need to understand their level of technology.
All we need to do is to figure out what one end of such a microscopic
wormhole would look like, how to capture and hold it, and then peer into
it for signs of a modulated light beam.
The advantage such an approach would have would be that bi-directional
communication could (theoretically) be established through such an
opening that would not suffer from the latency inherent in
interplanetary optical communications.
C
Carl Ijames
Then again, by the time they get so advanced to have an interplanetary
But they would probably still broadcast instructions on how to build the
subspace radio by other, lower tech means such as the laser flashes, so
less advanced civilizations could catch up and talk with them. Then we
could write a book about it, and call it Macroscope, and ... Oh wait,
someone already did. (Not directly what the book is about but close
enough.)
But they would probably still broadcast instructions on how to build the
subspace radio by other, lower tech means such as the laser flashes, so
less advanced civilizations could catch up and talk with them. Then we
could write a book about it, and call it Macroscope, and ... Oh wait,
someone already did
. (Not directly what the book is about but closeenough.)
L
Lostgallifreyan
I've wondered about this for some time, and didn't know if it was being
done. (I posted the thought on a forum or two and the thought was
dismissed).
My own take on the idea (cw emissions from modest sources) might be why,
but to me it's still an interesting idea.. How powerful do the pulses have
to be? Could we detect CW? There is one source of CW that we might easily
look for. Amateur and professional astronomers have both used lasers to
guide scopes, and if the laser is tracking a star, and pointing at it,
might some pulses be detected as a constant train? Especially in the case
of copper vapour lasers, which make small highly intense pulses
continuously. One thing about a planet full of people with lasers is that
there might always be something pointing from one star to another, so might
it be just a case of analysing the stars' light a bit more closely?
R
Rich Grise
I seriously doubt if anyone who has the power to communicate between star
systems would use electromagnetic radiation to do it. What's the status
on gravity waves these days? How about quantum black holes? ;-)
Thanks,
Rich
L
Lostgallifreyan
This thread was started on the assumption that they might. I didn't say
'communicating' anyway. I've considered the idea of nonlocal links between
particles as a likely channel for info but that's a tad big a step to make
assumptions about, so I think my question still stands.
People here have already suggested that even if 'they' are out there and
communicating, they might send some basic stuff in ways that are fairly
basic so initial contact can be made that way, or to send details of other
ways. I think it's more likely that there might be things similar to what
we do, so those are what we might best start looking for instead of making
assumptions about how ET communicates when we don't even know if ET
exists...
Anyway, what is the status on black holes and gravity waves? I think we
should stick to things we can more easily measure and quantify. If you
start from a perspective of total disbelief, why even look?
I'm asking those who are, not those who make rash assumptions, it hard
enough to find people taking this at a sensible level, which is why I'm
glad I found this thread. I think there are people posting in it who have
probably examined the idea of light and lasers in detail, with this in
mind.
