Ask Dr. SETI ®

How long do you think a civilization's radio communication phase will last? My question is based on the fact that the universe is 13,800 million years old, and it is impossible for any two civilizations to be at exactly the same level of development. This means that other civilizations may now use more advanced media (possibly even exceeding the speed of light). By this might we conclude it would be impossible to communicate with other ET intelligence?
 
Ruben, Portugal

The Doctor Responds:

You raise an important point about the temporal challenges of SETI, Ruben. It's not enough for another technological civilization to exist - they must exist at a level of technological development which we can recognize, and which will enable them to recognize ours, if dialog is to ensue.
 
Working to our advantage (as well as disadvantage) is the fact that radio telescopes are time machines. Because photons travel at a fixed velocity (300 Million meters per second -- the speed of light), any electromagnetic evidence we receive from Beyond (as well of any of OUR messages that THEY may receive) may have been traveling hundreds, thousands, or millions of years. That means any SETI evidence we receive on Earth may have originated from a civilization now long dead (and any of our messages received by our neighbors may not get there until our civilization is long dead). So, I consider the likelihood of establishing any sort of dialog to be negligible -- SETI is a one-way enterprise.
 
Can we receive any meaningful communication from other civilizations that do not share our time-frame? I believe we can. I can walk into a library any day of my (admittedly short) life-span, and read messages from artists, philosophers, and scientists long dead. That doesn't mean their words don't reach me, or that I can't benefit from them. Presumably, my writings may still enrich and inform lives of those who will live long after I am gone. At least, that is every author's hope.
 
More problematical is the question of whether we can even recognize the technology used by others, and vice-versa, when messages are received. Here, we rely upon the likelihood that civilizations evolve at different rates, and started at different points in time. We must assume that any civilization developing technology will go through a radio-polluting phase at some point along its path to something better (as, in fact, have we). So, at some point in the broad expanse of time, at least some of our cosmic companions may have generated (or may yet generate) recognizable signals. It's just a question of which ones we detect, and when. Given enough life-sites, maybe SOMEBODY's signals will reach us at a time in which we can share their technology -- even though, by the time we get the Signal, they may have advanced far beyond their technological infancy.
 
My point is, each civilization will follow its own technological trajectory. And, since radio telescopes are time machines, no alien civilization need be exactly at our level of development for SETI to succeed. It need merely be at the right distance from us for its primitive emissions to reach us at the right time.