This will interest
Amok if he's still about the forum ,a few years ago I remember a thread between Amok & HB discussing the pros & cons of each ,Amok thought OSETI was a more viable means of communication but as HB pointed out optical communication has a very narrow beam & thus the chances of establishing contact with ET are better with radio which has a wider spread.
I still have thread ,ahh heck with it I'll paste it here
......hmm hope the format holds out!
Hellburner
Senior Member Date Posted: Jun/26/2000 11:14 PM
1. The allure of Optical SETI is our current ability to achieve much higher optical uplink gains compared to microwave uplink gains.
2. It is generally agreed that there is some type of upper limit to the usable uplink gain, largely related to the ability to predict where to point such a narrow beam.
3. Any advanced civilization setting up a beacon for lower stage civilizations will be transmitting at the upper gain limits regardless of the wavelength.
4. Accepting number 2 and 3, it follows that the effective radiated power(ERP) will be the same at any wavelength the advanced civilization chooses to transmit, limited by whatever power they choose to budget toward the project.
5. Given equal ERP and the limits imposed by various noise sources, largely the 3°K background at microwave wavelengths and quantum noise(approx 44000°K) at optical wavelengths, and our ability to have much larger collection area's for the antenna, the clear choice for a SETI project would be at microwave wavelengths.
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Assimilator1
Senior Member Date Posted: Jun/27/2000 2:17 PM
Good points HB
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amok
Senior Member Date Posted: Jun/27/2000 7:59 PM
1. I'll agree with that. But there are other considerations as well. The most important of which is the "non-allure" of the microwave approach. We only used microwave signals with enough power to penetrate very deeply into space for about 40 years, which drastically reduces the time window in which to catch a technological civilization.
2. Hmm, why is that generally accepted?
Why should we limit possible ETI's intelligence and sophistication to that of our 20th century model (you can't really describe us as 21st century yet, just like 1900 technology wasn't really 20th century technology
)? The very fact that it is generally agreed that "some type" of upper limit exists just points to the fact that we can't accept anything we can't currently do.
3. I'm not really following this one. The fact is that the upper gain limits of optical transmitters is so much higher than that of microwave that this statement is more in favor of an optical approach.
4. Considering that I've refuted both 2 and 3 I have to call this one down as well. Especially based on the 3.
5. The quantum noise argument has been widely used. It can be shown that the effect of the much higher EIRPs of optical uplinks is such to so increase the signal strength at the targeted receiver, that it more than makes up for the increased receiver noise. The bottom-line is that the link signal-to-noise ratio (SNR) of an optical approach is far superior.
I would also like to point out the fact it is more expensive (power wise) to generate photons at microwave wavelengths than at optical or IR wavelengths.
Hellburner
Senior Member Date Posted: Jun/27/2000 8:45 PM
On point one, I can foresee in our future an "active" S@H where volunteers from around the world plant 100 - 1000 watt transmitters on rooftops or back yards that are synchronized by whatever means and effectively turning the entire face of the planet into a huge phased array transmitter. I don't think this would be beyond the capability of an even more advanced civilization.
On point two, as I alluded too, suppose you could achieve "perfect" alignment and keep your beam say 100 meters wide at an infinite distance. Where would you point it?
On point three, yes, we currently have a big advantage on optical uplink gain. That will not hold for a higher stage civilization. A higher stage civilization will use the upper gain limit at any wavelength.
On point four
On point five, if you can't accept that a higher stage civilization can achieve the same ERP irrespective of wavelength then there is no point to this discourse
On your last point, we have been able to convert power into microwaves at near 100% efficiency for decades. I haven't kept up on efficiency of laser technology but the last I recall it wasn't terribly efficient.
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Kwatt
Member Date Posted: Jun/27/2000 8:50 PM
After reading posts from both Hellburner and amok. I realize how little I know about the subject. I do like reading about it though maybe I'll learn something.
Now I'd like to get someone to correct me if I am wrong about this.
This is just my thoughts with no training or schooling on the subject.
Another civilization (if it exists) will technologicaly speaking will be ahead of us, behind us, or about the same as us. I guess their could be choices we don't know about.
1.If they are behind us they won't be putting out any signals we can detect no matter what. So it does not matter how we or where we look for them.
2.If they are about the same as us they have only been putting signals for apx. 40 yrs. so they would have to be apx. 40 light yrs. from us. I don't consider this likely. But, 40 lightyears is a rather big area to a race that has never even made it to another planet in their own solar system. So how and where we look matters.
3.If they are ahead of us and want to be known i.e. put up a beacon.
I would like to think they would put up a beacon that would cover all the spectrums. So we could not miss them if we look in the right direction. So where we look and not how makes the most difference.
Of course they might commuicate only by telepathy,odor(like insects),or something we have never thought of. Or they could be living underground on the moon and laughing their a$$es of at us.
And I really would like to be corrected if I am wrong here. I find this subject to be very interesting.
EDIT: corrected some spelling and grammer
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Message edited by: Kwatt on 06/27/2000 20:57:03
Hellburner
Senior Member Date Posted: Jun/27/2000 10:03 PM
Kwatt, I read a paper decades ago giving reasonable ranges for the different parameters for the Drake Equation. The result was an estimate of between 40 and 10k civilizations in the Milky Way.
That would give a best case of another civilization being approx 1000 light years away
In the end it's all guesswork, but if you don't look you will never know.
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amok
Senior Member Date Posted: Jun/28/2000 12:58 AM
Why would people do that? All we need is to turn the world into one giant microwave
.
Good question. To be honest with you, I suppose that the dispersed nature of microwave signals would be an ideal means for "initial contact". The use of more refined communication methods would probably be employed after a contact. However, I feel strongly that very few civilizations are going to just start broadcasting their existance like crazy across the galaxy. They would probably do as we are and listen for the "accidental" leakage from our early technology. And considering the time required for them to receive that signal they would assume that we have already moved to more advanced communication methods and then proceed to try and contact us via the more advanced method. And considering that it isn't that difficult to pinpoint a radiosource, a more advanced civilization would then proceed to use the more practical form of communication, assuming we have facilities to detect it by the time we receive the signal
. Still, you have proven that microwave communication would be a good way to detect the early blunderings of a civilization.
Your argument for point 3 isn't quite as good though. The problem is that the upper gain limit isn't universal across the board. The very nature of microwave signals sets its upper gain limit far below that of the optical band.
I point to the above regarding the EIRP. As far as we can tell its a fundamental problem not one of technology advancement. However, I will condede that it may be possible. A quantum physicist would be hard pressed to say that anything is impossible
.
And good point! Currently, laser technology isn't at its utmost efficiency. Of course that will improve. Laser technology has also closely followed Moore's Law over the last several decades. It will continue to do so. Assuming good efficiency (and by the way, I wouldn't say that have produced microwaves at 100% efficiency, very seldom does anything achieve perfection
) my statement is correct.
Michael
Senior Member Date Posted: Jun/28/2000 1:12 AM
We also have to consider that different planets will have developed at different times. Our 40-year window for microwave technology will extend into the future as well and the relative age of other star systems has to be factored in as well.
Michael
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amok
Senior Member Date Posted: Jun/28/2000 1:29 AM
Very true, but that's still only a 40 year window per civilization. Whether its already happened or will happen.
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I left the sigs in
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Originally posted by: m2kewl
Originally posted by: Evadman
Evadman goes out side with a 6 Cell Maglite Flashlight and flashes out "Evadman is the leader of Earth" in binary.
m2kewl flashes in the same direction towards space as evadman, "NOT!!" in binary and various quantum states of light in case aliens use quantum computing
LMAO
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