http://bbs.stardestroyer.net/viewtopic.php?t=123249
Maybe my argument about radio and distances and signals was right after all!
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http://bbs.stardestroyer.net/viewtopic.php?t=123249
Maybe my argument about radio and distances and signals was right after all
Order of Kilopi
He talks about the issues of detecting radio intended for internal or "local" use with current hardware, but current radio SETI efforts are focused on looking for deliberate transmissions, so it seems a rather pointless article. There are endless debates on how likely deliberate transmissions would be, all based on different assumptions. Strangely enough, people who want to find a signal tend to find ways to say it is likely, and people who don't want to find a signal tend to find ways to say it is unlikely. The debate seems rather pointless to me.
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Order of Kilopi
The original essay is here.
http://www.bidstrup.com/seti.htm
I can find fault with only one paragraph; this oneActually our type of solar system is quite a good candidate, because of the Jupiter-sized giant removing most comets from the inner system. On the other hand, the possibility of inhabitable moons is still debatable; I think that life may evolve on moons of gas giants in the habitable zones, but only those with minimal magnetic fields- this might be a rare case. On the gripping hand an extraterrestrial civilisation might have detected the oxygen and chlorophyll in our planets atmosphere and biosphere and be deliberately targeting us periodically with a ping of data.Why would they suppose that this very ordinary star of ours, with its very ordinary solar system is any different than most, in that it harbors a supposedly intelligent civilization? Our solar system does not really stand out in any way that would presuppose they would think it a likely candidate. A far more likely candidate would be a solar system with a Jupiter-like planet orbiting about the same distance from the sun as us, a planet with a large family of moons, one or more of which is likely to be the right size to be earthlike. That lets us out. Our solar system is more unlikely than most - an earth-sized body too close to its star to be habitable (Venus), and another body at just the right distance, but too small to retain an atmosphere that is thick enough to make it hospitable or even habitable (Mars). The planet in the middle between them has a large moon, meaning it has been the object of a collision with a sizeable planet in the distant past, and that reduces the likelihood of its habitability. Likely to be a desert planet, with a thin atmosphere, bombarded by lots of meteorites, enough to make a civilization unlikely.
We don't want to miss the next ping.
Established Member
Well, why only weak magnitic field?Radiation belts are narrow and by that logic his argument about "not likely habitable Earth" is valid.Originally Posted by eburacum45
I hate this when someone's saying "only planet most similiar to ours can harbor complex life", how can you know what kind of peculiarities other types of life prefer.Extremophiles on Earth never developed beyond relatively primitive organisms IMHO not because it would not be possible, but because they are not viable on a planet where most of the enviroment cannot sustain their extreme tastes.
And do you really belive that it's simple to detect life on a planet based solely on some spectroscopic observations that cannot be done if the planet is too far and the planet have to make transits?
Order of Kilopi
Well, if you include the possibility of life as we don't know it, then life could probably exist anywhere there is an energy gradient. In that case all forms of SETI would be made more difficult.
But I would expect that over time, a civilisation with good instruments could begin to make informed guesses about which worlds harbour life-like processes. One indicator might be chemical imbalance; our own oxygen-rich atmosphere is unlikely, and is caused directly by biological action. Atmospheres with other unlikely components, such as chlorine or fluorine, might also be supected to have biological processes associated with them. Speculation about this sort of thing is already occuring in astrobilogical circles, I believe; it is difficult to anticipate what form 'life as we don't know it would take, but it is a lot of fun trying.
Established Member
That's not quite correct. Much of the early Earth was just like the kind of climates that extremophiles live at, but because they were out-evolved by other organisms, the climate of Earth shifted to one less favorable to them. There are some pretty good arguments for life needing a planet with conditions similar to Earth to evolve intelligent life. Chemical reactions happen easier at temperatures where water (AKA the universal solvent) is liquid, oxygen rather energetically combines with other elements, which is also beneficial for intelligent life. Its certainly possible that life could evolve on a planet other than an Earthlike one, however, us being able to find and identify that life is pretty danged near impossible. For heaven's sake mankind, Europa's only forty four light minutes away you know. I'm sorry, but if you can't be bothered to take an interest in local affairs that's your own lookout.
Established Member
Life creates unstable (on geological scale) conditions. If these conditions are visible on surface and atmosphere, we have at least theoretically possibility to detect these unstable conditions and infer presence of life from distance.
Of course, with totally alien biochemistry will be another problem: mistaking non-living weird chemistry with weird life.It is difficult, because life IS most weird chemistry in universe, showing most awesome emergent properties.
Order of Kilopi
One thing that may make SETI much more difficult is that maybe everyone is listening, but no one is speaking. Is there any program at present like the 'shout' sent from the Arecibo Observitory in 1974?
Established Member
Nope. We're probably all sitting around listening, and no one's talking, because they're too busy listening.
Established Member
That guy is right: because the odds against it are great, we have no business attempting it.
I don't think SETI will succeed, yet I'm foolish enough to believe that you have a one hundred percent chance of failing anything you don't try.
Banned
It's refreshing to see yet again that the term "zealot" isn't relegated to those of various religious faiths, and can be equally, regardless of philosophical or religious belief, or even the lack thereof.
Since binary is the most basic of all numbering systems, I believe it's the best approach, beginning with a bang.
The smallest word is one bit long. We need to demarcate times between both bits, as well as between words.
Let's say we're going to use 4 bit words. Remember, all we're trying to do at this point is get someone's attention, nothing more. Assuming a 5 second interval between bits, and a 60 second interval between words, we start with a 1 to get their attention, then follow by counting from 0 to 15:
1 0001 (attention-getter)
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001
10 1010
11 1011
12 1100
13 1101
14 1110
15 1111
Thus, we have a total of 32 1's. The zero's are represented by the absence of an event at the prescribed interval.
We also have 16 60-sec intervals between bytes (subtotal of 960 sec), and 16*three 5-sec intervals (subtotal of 240 sec) between the bits which make up a byte.
Thus, the entire message could be sent using 32 events over a duration of exactly 1200 seconds, which is 20 minutes.
Now the question becomes, what might we use as an "event?"
I propose that the best source would be a series of space-based X-ray lasers pumped by a nuclear explosion. Thirty-two, to be exact, and targeting the future whereabouts (when the x-rays will reach it) of a nearby star most likely to have an Earth-like planet.
To get more bang for the buck, we could even employ separating strata, so that we can target several such systems with each blast.
Furthermore, to ensure that the full message is received, we can repeat as required, perhaps three times every twenty-four hours, then over a space of, say, ten days, repeated again a month later for three months, then beginning anew the same time next year, for three years.
Thus, the requirement for 32 weapons becomes a grand total of 2,592 weapons, AND we've communicated, in the process, the length of our hour, our day, our month (perhaps we should use a lunar month, as that's what they'll be observing), and our year (they'll be observing that, too).
Then, we sit around and wait for about 50 to 100 years. If we don't hear anything, we can assume either they're not there, they weren't paying attention, they don't care, or they're not yet at that level of technology.
If we do see massive craft dropping in for a meal, then we can assume, "oops, we goofed, and we're toast."
Or perhaps just a side dish...
Banned
On second thought, let's do the listening, not the sending.
And since this sort of pattern is NOT found in nature, we should be looking for it in the X-ray band, not the radio frequency bands.
Established Member
As Mugalliens illustrated talking is expensive, so talking to distant stars is not in my budget and I hope not in the USA budget. If ET gets our message they may have no idea (or a wrong and dangerous idea) of what we ment. They might not reply. I hope we will not reply to a message, when and if, we get one. Round trip for a conversation is likely more than 8.5 years. Who wants to wait that long for a doubtful payback on a few billion dollars?
Worse ET may come here if we indicate there is a likely civilization here. Even if ET's intentions are good, the results of meeting may be bad for most humans. Listening is relatively inexpencive and much safer. Neil
Member
This is my first post here so if I messed up please cut me a little slack. Perhaps the most detectable signals sent by Earth so far are not Mr. Ed, Lucille Ball, the Berlin Olympics, or that Arecibo radar transmission. Radio, TV, Arecibo, HAARP, even the total power generating capacity of the USA are all just small fractions of the energy released by a nuclear explosion. It's true that the nuke's energy is spread out all over the EM spectrum - but maybe that makes it even more likely to be detected.
According to Seth Shostak at SETI, with our present equipment and if everything was pointed just right we could detect an Arecibo transmission from 500 light years away (http://www.seti.org/news/features/good-timing.php). Arecibo puts out 2.5 megawatts. Compare that to a relativly small 1 megaton nuclear blast at about 4 x 10^15 watts. Or what about the USSR Tsar Bomba test at 50 megatons? That one was sure to be an attention getter! I wonder what kind of first impression that would leave with the ETs and if it would influence their attitudes. Would they be a little less inclined to be nice after all?
I can only hope that if some ETs did detect our nuclear tests that they wouldn't jump to conclusions and instead tune in and see what else was going on over here. Maybe they would pick up My Favorite Martian and conclude we were just long-lost relatives or something.
Established Member
Nukes are also not beamed, which drastically reduces their detectability, even 200 petajoules doesn't count for much radiated across the whole sky when compared to 2.5Mw beamed over a fraction of a degree. Also a nuclear blast is a transient event making it much harder to detect than a prolonged transmission, particularly as it won't be poking much above the random noise level.
Established Member
I think its foolish to think SETI can't succeed. It can but that doesn't mean it will. The program is full of assumptions. Educated assumptions but what is to say that "they" are not broadcasting on something we won't know how to detect for another 2k years? But to NOT look is insane. It would be like not looking for a new species on earth because you've never seen one before. They should be there. So look. And keep looking until you can completely confirm something.
Banned
Probably not, as it radiated it's energy in all directions.
In order to dramitically increase the amount of EM radiation received at the intended destination, you've got to channel that energy into a coherent beam which points in one direction. Even if only 1% of the nuke's energy input into an X-ray laser comes out in the beam, that beam is still pointing at perhaps 1/10,000th of the cross section area as the unfocused bomb, thereby increasing by a factor of 100 the amount of energy that will reach the intended destination.
Banned
I agree with you, Neil. My post was merely a "if you insist on doing it, do it right" response.
But I'd rather be the fly on the wall...
Member
Sorry but I haven't mastered doing quotes properly yet but I would like to thank you Grashtel and Mugaliens for taking the time to address my comments about the detectability of the nuclear tests. I agree that they probably will not be easily detectable by ET. At least I hope not.
I am still curious about the relative power levels and detectability and I would appreciate being enlightened. The Arecibo transmission was 2.5 x 10^6 watts and per the SETI web article cited (http://www.seti.org/news/features/good-timing.php) the Arecibo beam focuses on .00001 percent of the sky. If my math is correct, to maintain the same power level across 100% of the sky would require 10^7 more power or 2.5 x 10^13 total watts total. That's still less than 1/100th the total output of a 1MT nuclear explosion. In terms of sheer energy, nuclear explosions still seem to me to be the strongest "signals" we've sent out into space thus far. And those signals are not focused on a single target like Arecibo; They go everywhere. All things being equal I would think that would make nuclear blasts much more likely to be detected than the Arecibo transmission.
However, are all things really equal? How much does the EM spectrum spread affect detectability? Does it make it more or less likely? How about the transient nature of a nuclear explosion energy spike? Would ET's version of our own Compton or Swift or Chandra be able to detect one? How about if they had some much more sophisticated version that looked at the whole spectrum at once? Is there anything occuring naturally that would produce a similar low power but local spike across multiple frequencies simultaneously?
Order of Kilopi
Lets use a metephor. Lets say you have an equil amount of watercolours. You can mix them with a lot of water and spread it out further, but create a weaker colour over all, or you can use a litttle water and create a stronger colour in a smaller area. The amount of pigment is the same (amount of energy being radiated), but the area it is concentrated in is much smaller.
Banned
Over what time period? Energy, such as joules, are measure relative to a time frame. In English units, it's wattseconds, kilowatt hours, etc.
Why disperse it all over the sky such that the received signal strength is but a very small fraction of what would be received if you focused the nuke's energy into an X-ray laser and directed it towards where your target will be when the laser beam reaches them?That's still less than 1/100th the total output of a 1MT nuclear explosion. In terms of sheer energy, nuclear explosions still seem to me to be the strongest "signals" we've sent out into space thus far. And those signals are not focused on a single target like Arecibo; They go everywhere. All things being equal I would think that would make nuclear blasts much more likely to be detected than the Arecibo transmission.
You gotta remember that we're but a stone's throw away from a star that puts out millions, if not billions or trillions, of 1 MT-worth chunks of energy every second. Trying to spot a 1 MT fusion detonation in our solar system from 50 light-years away would be like trying to spot a firefly's 1/4-second glimmer of bioluminecense during the height of a Tsar Bomba event.
The wider the spread, the less likely the detection.However, are all things really equal? How much does the EM spectrum spread affect detectability? Does it make it more or less likely?
No, as the various spikes from the sun itself occur all the time and are many orders of magnitude larger than a 1 MT detonation.How about the transient nature of a nuclear explosion energy spike? Would ET's version of our own Compton or Swift or Chandra be able to detect one?
The nuke would be lost in a much louder noise. To address this with yet another metaphor, it would be like you and your friend, both sitting front and center on the 50-yd line, but on opposite sides of the stadium, trying to out-shout 80,000 fans so crazed that the none of the linesmen nor the backs can hear him.
There's a point where this might be possible. While a nuc-det does radiate across many frequencies, it's not an even spread, and the various strengths within any given frequency vary differently over time. Thus, a very sensitive detector programmed to spot the pecuiliar signature of a nucdet may be able to pick up this anomoly.How about if they had some much more sophisticated version that looked at the whole spectrum at once? Is there anything occuring naturally that would produce a similar low power but local spike across multiple frequencies simultaneously?
Member
Here you have another problem, if we could beam that amount of energy. To which region must we aim the signals.
Member
Thank you for the replies. It's good to hear that the consensus is that our nuclear blasts are probably not too likely to be detected. I think that is a good thing. Maybe I am just a wuss but I also think that for the time being it's better to keep a low profile and listen rather than broadcast. Just in case resistance really is futile.
Established Member
Yep, SETI is impossible. And here's why:
Terry Bisson - They're Made of Meat
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