How would Earth communicate with a starship or a distant civilization?

USS Enterprise NCC-1701-D, a starship of the Star Trek: The Next Generation era. 

Credit: Memory-Alpha.Org /Paramount Pictures /CBS Studios

Its not a new question but its still a puzzle; How would humans communicate with extraterrestrials.

It may not be as easy as the science fiction writers and film makers would have us believe.

David Messerschmitt

David Messerschmitt, of the University of California at Berkeley, is addressing this potential problem. A new paper by him on Arxiv examines the issue and it provides an intriguing insight into how to communicate outside of our Earth.

Messerschmitt explains that humans already communicate with probes that are astronomical distances from Earth (Voyager 1, now 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 (ISM) gets in the way, and stars shift due to relative motion.

We are adept at communicating with our own satellites and probes but don't know how other civilizations communicate and how they design their systems. So, how could you send a message that would definitely be picked up and understood?

This sequence of images, showing a region where fewer stars are forming near the constellation of Perseus, illustrates how the structure and distribution of the interstellar medium can be distilled from the images obtained with Planck. 

Credit: ESA / HFI and LFI Consortia

Messerschmitt further explains that starships and civilizations would, almost certainly, have different communications protocols and therefore, 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 interstellar medium  (ISM) would have to be contended with (something that pulsar astronomers and astrophysicists are already working on, he said).

In either case, when 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.

More information: "Design for minimum energy in starship and interstellar communication." David G. Messerschmitt. arXiv:1402.1215 [astro-ph.IM] arxiv.org/abs/1402.1215