A of E author in alien light signal detection project

Only "involved"? It's Paul's newest oseti project.

- also see and

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 Its web pages are a few years out of date at this point; no doubt because since then all the hard work has gone into finishing the electronics and software.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,

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 Thanks,
    - Win

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

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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.

--
 Thanks,
    - Win

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.

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PMTs and mirrors don't pick up X or gamma rays. ;-)

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

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.

--
 Thanks,
    - Win

Yes, I'm sure you're right ~ those X-ray mirrors in XMM-Newton and Chandra must be just tinsel decorations.

-jiw

[snip]

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.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Misery loves company, especially this one.

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

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

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.

^known

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.

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kensmith@rahul.net   forging knowledge

In article , Paul Hovnanian P.E. wrote: [...]

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.

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kensmith@rahul.net   forging knowledge

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

[snip]

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.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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E-mail returned to sender -- insufficient voltage.

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.)

-- Regards, Carl Ijames carl.ijames at verizon.net

"Leon" wrote in news: snipped-for-privacy@t31g2000cwb.googlegroups.com:

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?

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

Rich Grise wrote in news: snipped-for-privacy@example.net:

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.