Taking a rest from analysing Pulsars for a while, I started to consider what the future might hold assuming that there is no real breakdown/breakthrough in our current understanding in Physics. That is to say that General Relativity and Quantum Mechanics form a really good description of how the Universe ticks, and there is no Warp drive, or hyperspace short cuts from A to B.
My first thoughts were of our future computing structures; I think that the Cloud is a signpost of what is to come - the great granddad of what I guess Asimov was trying to describe with his Multivac machine; an all pervading computer network affecting every aspect of our lives. SetiQuest is possibly leading the way with the ability to download and process in real time the data from ATA being seriously discussed. What I think we are beginning to see is our experiments becoming simply data acquisition systems for Multivac's ancestors. Experiments such as the Large Hadron Collider and its successors, requiring massive storage and processing capabilities will simply dump its output straight into the computing network; The data returned from Meteorological and Earth Resource satellites will be treated likewise. Our Interplanetary probes simply become remote DAQ's for the computer network. With this subcontracting of our research to the network, the lifetime of the researcher becomes much less important, and we can consider projects that take many decades to complete, safe in the knowledge that Multivac is archiving and processing every bit of data that the probe is returning.
Rocketry experts have long known that the key to high final velocity of a space probe is not so much the thrust of the rocket engine, but more the exhaust velocity of the reaction chamber. For years they have imagined devices such as Ion drives (which have now been used in vengeance in probes such as Dawn and others) and even Photon Drive craft, which must represent the ultimate in performance. True they only generate a few ounces of thrust, but left running long enough, they will get the probe up to a large fraction of the speed of light. The current existence of 10Petawatt lasers must point the way to such vehicles being practical.
I guess within about 1000 years or less we would have the technology to seriously consider a relativistic interstellar vehicle, but where would we send it? Sure to Proxima Centuri, and local star systems. But maybe I have become obsessed with Pulsars, what I would give to see a 25 mile diameter block of neutrons weighing more than the Sun revolving in excess of 1 rev per second. Looking at the data sets that Seti Institute has published shows that I am not the only one who shares this interest. The closest Pulsar must be one of the first targets for our probes. Once there it would need to generate huge amounts of power to get the signals back to Earth - it becomes the ultimate beacon. Safe for the likes of Stephen Hawkin, the beacon isn't in the Sol system at all. It is broadcasting from a place that we know Radio Astronomers are likely to be observing, for that is what we have been doing since Joscyln Bell first discovered them. thus increasing the probability that ET is likely to pick up the signal; whilst not telling him where we are are, it will transmit the message “You are not alone” loud and clear.
If this train of though is indeed reasonable, then it will also be true of Alien races that are only about 1000 years (my guess!) in advance of us. Their probes could already be there transmitting pictures and data of the smashed planetary system back to their own home. So perhaps the best chance of detecting ET is not from probing local stars in a random fashion, but looking at interesting astronomical objects, where probes might be situated transmitting data – hopefully loud and clear.
Is it not rather unlikely that we would be in the line-of-sight between the probe and it's home planet? I mean, if we were they might as well have sent the probe here. But I like the notion of using unusual astronomical objects as common reference points for different civilizations.
You may be right, however I believe that the beam divergence from our current space probes is a great deal larger than the beam divergence from our ground based facilities, so there is the possibility of picking up spillage or side lobes from the probe.
In addition, the point I was trying to make, is that a pulsar makes an ideal position to place a beacon, in as much as it gives few clues regarding the home world of the probes creators, thus removing the Stephen Hawkin objections to setting up a beacon, whilst keeping the home world radio sky 'dark' and in addition being in orbit around an 'interesting' object increases the probability of an alien species actually observing the object, and hence detect the beacon.
I'm a big fan of the SETI eavesdrop theory. I have hunch that first detection will be by picking up a signal intended for a remote probe or outpost civilization. This was the basic idea for the collection of the anti-galactic-center datasets. Being in the middle is one layout that works but being on opposite ends past the source or destination also works and is probably more likely. A radio dish's beam spot size grows the farther you are away from it. So if the distances involved are thousands of light years then we could be quite a bit off-axis and still be in the main beam. Though for those sorts of distances dishes a lot larger than Pioneer's or Voyager's would be required. The bigger the dish, the smaller the beam spot size which means we would have to be more on-axis.
It would be nice if we could get some math together for the effects of the ISM on interstellar signals. Then it would be easier to consider what kind of energies a transmitter like this would require. It seems to me that if the communications were not intended for Earth, it is unlikely that spillage would travel very far from the receiver and still be detectable by our instruments. It would be optimized away by its designers.
Assuming a low-density ISM distribution it is just the 1/r^2 inverse square law. So assume that the SETI source is 1000 light years from the destination probe/outpost and Earth is on-axis but 1000 light years past that. The signal we receive would be -6 dB from what the destination received.
And -6 dB is like one fourth or something? Yeah, that doesn't sound too bad. But at that (relatively!) short distance, is the beam likely to be very broad?
Yes, -6 dB is not that bad. Assuming we had the same size receiving antenna then we should be able to detect it. Again, this is assuming their modulation isn't some crazy complicated scheme that humanity hasn't invented yet!
Remember that my 1000 light year example could just as easily been 100000 light years for the same -6 dB drop. In this case the inverse square law is our friend. I also haven't looked at how much power this would require but that's SETI's problem not ours! (:
Still following this point, I have come to realize an interesting consequence of finding an ET probe in orbit about a Pulsar.
I understand that a pretty good estimation of the age of a Pulsar (say T years) can be obtained from its period, and decay rate. It follows that, assuming ET has used a relativistic propulsion unit allowing his probe to reach approximately the speed of light, this means that Home World must be within a sphere of T/2 light years radius of the Pulsar (assuming that they had the probe already built, and launched it immediately they see the Star go Supernova).
From this radius we can compute how many stars in this sphere, and from this we could make a damn good estimate of the number of the density of intelligent species within a relatively typical region of space. Such a measurement would go a long way toward evaluating virtually all of the unknown values in the Drake equation, and would provide some valuable input regarding the number of intelligent species within the Galaxy.
I know the logic isn't totally sound, as I haven't taken into account the time required to accelerate up to cruise speed, and deaccelarate back down to orbital velocity, and with low thrust propulsion systems this could amount to quite an amount of time - but I don't think that it spoils the overall conclusion,
"So perhaps the best chance of detecting ET is not from probing local stars in a random fashion, but looking at interesting astronomical objects, where probes might be situated transmitting data – hopefully loud and clear."
I found your postulated idea above to be insightful and most practical given the overwhelming number of targets (an understatement) we could point our instrumentation towards. An ET race of beings might logically be interested in Astronomical events such a SuperNovae and Pulsars. Perhaps if they were at least 1,000+ years in advance of ourselves, they may have situated their probes in the close vicinity to gather the all important data which would enable them to add to their collective pool of knowledge about this Existence we Humans call Cosmos/Universe.
Since there are varying opinions about whether or not these Beings would be benign, I appreciate your caution about broadcasting our whereabouts. If they are so well in advance of us, they may be able to detect our location from a sort of "vapor trail" given off by the ionic exhaust of our probe's engines, albeit the giveaway from our continuous communications with the craft. However improbable or impractical as it may seem to us at this time, they may even be there "in-the-flesh", themselves.
Yes, 1000+ years hence, we may have devised an early warning detection system from our Astronomical Observations which may enable us to situate a probe there to say: "Hello, you are not alone". Perhaps our probe will be in the form of some holographic projection capable of instantaneous retrieval and storeage of data. We humans have been in the habit of devising simulators for decades now. It may just be that we are learning to devise the ultimate simulator: An Intelligent Holographic Probe capable of observing and assimilating loads of information much in the same way as the human brain processes data and reasons from that data. A thinking, decision-making, "sentient" being. Perhaps I have watched 2001 too many times and have "HAL" on the brain. Yet, one of life's lessons has taught me to: "never say never".
Thanks for your feedback on my earlier post. Although I have the greatest respect for Steven Hawkin's worry about beligerent Aliens homing onto a SOL based Beacon; I personally think that we have very little to fear from this front. My main problem with placing a really powerful beacon here is that the slightest bit of non-linearity in the transmitter could effecively blind all of our radio telescopes, with the harmonic distortion caused by this defect. Rather as short sighted as building a new optical telescope in the heart of London or some such metropolis.
Regarding a nasty alien being able to trace back the exhaust plume of our Ion Drive probe; I would think that with the ultra strong magnetic fields, and radiation environment around the Pulsar, the 'vapour' trail would soon loose coherence, rather like the vapour trail of an airliner flying through the jet stream., and of course if we were using a photon drive, this wouldn't be a problem anyway. If there are any hostile aliens out there, my worry would be that they have already detected the RADAR pulses, TV transmissons and Deep Space probe communications and are already on the way.
Regarding your observations about our trend to devise simulators for almost every thing these days. I often ponder that if we take the concept of intelligent design at is base level; then maybe the 'creator' of the Universe would probably run a Simulator using a Machine whose power we could only dream of. Suppose now that he, it, them were using something like Neural Net techniques or Genetic Algorithms, then the simulation would exhibit Darwinian characteristics. Also there would probably be multiple populations being simulated simultaneously. If the simulation was that detailed, would the simulants actually be able to tell that the environment that they found themselves in was artificial. Maybe when we eventually contact an alien species, all we will have done is form a link between one simulation population and another. However I must admit that I find such a train of thought rather disheartening, and rapidly remind myself that I really don't believe that this idea reflects the reality I live in. However this of course be mearly a safety feature within the simulation that has been included to prevent the simulation from reaching deadlock due to complete population apathy on dicovering they dont really exist;-)
Dave, I completely agree with you that belligerent aliens should be our least concern.
If they do exist, they can hurl a large enough object from the asteroid belt at us and game is over for us. Until we can leave this planet in a sustainable way, we have no way to defend against such an attack. No point to spend resources on that. We should instead focus on doing everything we can not to be perceived as a threat, or better yet, make them WANT to talk to us.
This thread is about where might we look for aliens?
In another post under 'why have we not been contacted' I postulated that SETI would be well served to simply assume EVERY galaxy has at least one form of intelligent life.
For intelligent life in the Andromeda galaxy this means that realizing like us that we are moving towards a collision with each other, they would send probes as soon as their technology allows it to explore the galaxy they will be merging with, and specifically find out what intelligent life exists there and if it is more advanced than they are.
In that same post I also postulated that the most probable assumption SETI can make is that any alien life we CAN detect has a high probability to be more advanced than us. Detectable aliens from another galaxy would by definition be more advanced (they came here after all) and detectable alien technology from this galaxy has a high probability to be more advanced simply because ours is only 100 years old (minuscule in cosmic time scales). If they are more advanced than us - they already found us.
So 'finding' alien intelligent life is more about making them want to get in contact with us, not the other way around. We already are broadcasting our presence enough for them to find us. I don't think that is our problem here.
lol, cool. A man made space dragon. I think I read a book about a ship like that.... That improves itself based on its understanding of the universe as it travels along... Don't remember the name... Good Idea but. :) Personally, I want a gene-bonded 'void hawk.' :) (-Peter F. Hamilton)
If you aren’t already familiar with the DARPA/NASA 100 year starship study, you might want to take a look at it. They are trying to motivate and encourage the current generation of students and technologists to solve the technological challenges of interstellar space flight and create an organization that can maintain funding and focus for this challenge more quickly than your 1000 year guesstimate. They will be holding a public symposium in Orlando, Florida from 30 Sept – 2 Oct, 2011 and there will be a discussion track on ‘destinations’. Although the abstract submission deadline was 8 July, you might consider submitting a late abstract giving your arguments for pulsars as being good destinations because their technologies are already likely to be there.
Over the years a number of different astronomical objects have been suggested as targets for SETI – pulsars among them (e.g. see Edmonson and Stevens, 2003). Novae and supernovae have been suggested as referants for a SETI ellipsoid to determine when to look at specific targets. Transmission directly towards or away from astrophysical rarities has been suggested as a way to insure that when an emerging technology along that line of sight begins to explore the cosmos, the signal will be discovered. For other special target ideas, take a look at the archive of SETI searches (and by the way, let me know about any omissions or corrections needed).
Thanks for bringing this to my attention, no I wasn't aware of the DARPA/NASA study, I must do some digging to learn about it.
I was aware of the BIS (British Interplanatary Societys)' Project Daedalus(?) published quite a while ago, which was a plan to evaluate the engineering feasibility of building and sending a star probe to Barnards Star. It was a really nice piece of work; which investigated the engineering aspects of such a project, which was to be built with technology which was a feasible extrapolation of what was available then (e.g. it didn't rely on finding a star gate just beyond Pluto). The results were very convincing, that the project might be expensive, but would have been certainly doable. It was this study that convinced me that at least local Interstellar travel was feasible. I was a bit concerned at their proposal to mine Jupiters atmosphere for probe propellent; however finding huge balls of solid ice in orbit round the outer planets makes the concept look much more practical.
I believe that the BIS have now embarked on what they call Project Icarus (Son of Daedalus) in which they are to effectively replan the project in light of modern knowledge and engineering. Something I am looking forward to reading about.