I have a new exercise routine where I watch Star Trek: The Next Generation most mornings of the week while doing my thing. Besides serving as awesome distraction, the episodes do get me thinking about how humans would talk to extraterrestrials. It likely wouldn’t be as easy as the show portrays to zoom across space to conduct diplomatic negotiations at the planet “Parliament”, for example, so interstellar communication would be a problem.
Luckily for non-engineers such as me, there are folks out there (on Earth, at least) that are examining the problem of talking between stars. David Messerschmitt, of the University of California at Berkeley, is one of those people. A new paper by him on Arxiv examines the issue. Note this is a preprint site and not a peer-reviewed journal, but all the same it provides an intriguing addition to how to communicate outside of Earth.
Messerschmitt explains that humans already communicate with probes that are a fair distance from Earth (say, Voyager 1 in interstellar space) at radio frequencies, and there is some usage now of laser/optical communications (namely between the Earth and the moon).
Across greater distances, however, you lose information, the interstellar medium gets in the way, and stars shift due to relative motion. Besides all that, at first you wouldn’t know how the other civilization designs its systems and you could therefore send a message that wouldn’t be picked up.
He further explains that starships and civilizations would have different communications requirements. Starship communication would be two-way and based on a similar design, so success comes by having high “uplink and downlink transmit times”. The more information, the better it would be for scientific observations and keeping down errors.
Civilization-to-civilization chats, however, would present headaches. As with all diplomatic negotiations, crafting suitable messages would take time. Then we’d have to send the message out repeatedly to make sure it is heard (which actually means that reliability is not as big of a problem.) Then the ISM would have to be contended with (something that pulsar astronomers and astrophysicists are already working on, he said).
In either case — talking to starships or other civilizations — one can assume there’d be a lot of energy involved, he added. “Starships are likely to be much closer than the nearest civilizations, but the cost of either a large transmit antenna or transmit energy is likely to be considerably greater for the starship than for a terrestrial-based transmitter,” he said, suggesting that a solution would be to minimize the energy delivered to the receiver. Other civilizations may have found more efficient ways to overcome this problem, he added.
You can read more details of the research on Arxiv, where Messerschmitt talks about Gaussian noise, channel coding and other parameters to keep in mind during communication.
This is a possible way of contacting another civilization, but in my option not the method that gives us the best shot at relaying information to another HEI (human equivalent Intelligence) extraterrestrial.
Perhaps the best way to reach out across the stars is to do things not the Star Trek way, but the way shown in 2001: A Space Odyssey.
The Monolith on the Moon in that movie represents a Von Neumann probe. In the distant future, we might be able to construct a factory, likely in Earth orbit, that could automatically assemble these probes and launch them at a selection of candidate Earth-Analogs. These probes travel to dustant star systems and enter high orbit around these planets, occasionally activating to scan for signs of HEI or to relay back to Earth.
If these probes detected HEI or were triggered by an attempt to tamper with them, they would activate and relay information both into their surroundings and back to Earth.
These probes might contain an archive of human knowledge along with an advanced A.I. They would contain simple tools to operate them, a tiered rosetta type teaching system, and all the equipment required to sustain these systems over enormous periods of time. As an alien race became more able to access them, they could use the A.I. as a medium to ask questions and receive dynamic answers; an ambassador of sorts.
This type of probe has a few advantages: It has the ability to wait for the development of HEI, which a transmission can’t. It is more likely to be received, as it is difficult to miss, and it could in relay dynamic information. Sending out dozens, hundreds, or even thousands of these probes would mean more access, and to more locations. As a statistics game it plays out well too.
Acting as a repository, these probes could survive and communicate information even if some catastrophe befell Earth. In addition, they could also be outfitted for aliens to use its systems to communicate back to us.
The drawbacks to this type of transmission are technological hurdles and cost. We currently lack the tools in sufficient levels of maturity, but hey, the article referenced star ships, and we don’t have those either.
One slight difficulty with sending physical objects is the long travel time at achievable velocities. Our probe might arrive to the alien equivalent of a ticker-tape parade. They would be expecting it, having already got the news through other forms of transmission.
Agreed, assuming they are actively looking for our transmissions at the right times. Note that our general broadcasts degrade out to noise around 2 light years. We’d have to directly target stars with powerful arrays, and assume powerful arrays are listening in on us at the other end. That’s a lot of assumptions.
I feel the odds are far higher of with probes. Even derelict ones could communicate a lot of information about us over a period of millions, perhaps even billions of years. We could potentially cover the entire life-cycle of a planetary system with these.
That makes we wonder what’s a reasonable radius of action for probes. I read somewhere that there are 63 stars within 5 parsecs. Some mental math gives me a travel time of a bit under two centuries to the furthest of those, at a tenth the speed of light. It may not be able to stop when it gets there. It’s a lot easier to go fast if you minimize mass by expending all of your propellant. 63 stars. For less than the cost of one interstellar probe we could point powerful space-borne lasers at all of them and transmit 24/7. We could get a response in our lifetimes: “OK, prime numbers, we get it. Please send something else now!”
Lets do both!
You hit the nail on the head with this reply. Getting up to. 10 of c is nearly impossible for us for the foreseeable future. The only working hypothesis that I am aware of to date that doesn’t require unbuilt tech involved several very close passes by the Sun and Jupiter.
Assuming that this part is do able, there is no way for it to slow down enough to enter orbit in the targeted system. What we’d get would be a very brief snapshot of the system as our probe went screaming through.
Energy problem? The universe is full of energy, just use what is available. Find a star or pulsar on the opposite side of earth, in relation to the target civilization, modify its light signal by passing it thru a variable transparency object. Energy problem solved.
I would go with Dr Neil deGrasse Tyson. I mean the apes almost have our DNA and AFAIK we are not exactly in a rock and roll band or exploring space together.