Don't phone ET, send an encoded object
American scientists say writing, rather than phoning, is probably the best way to contact extraterrestrials.
So instead of phoning home, it could have been more energy efficient if ET had inscribed information and physically sent it, because radio waves disperse as they travel.
"Think of a flashlight beam," said Professor Christopher Rose, of Rutgers University in New Jersey, who reported his finding in the science journal Nature.
"Its intensity decreases as it gets farther from its source. The same is true of the beam of a laser pointer, though the distance is much longer."
Professor Rose and his colleague, physicist Gregory Wright, were pondering how to get the most bits per second over a wireless channel when they concluded that the detectability of a signal diminishes with distance.
If the recipient is not listening or misses it, the message may have to be sent numerous times but a physical message encoded in an object lands somewhere and stays there.
Messages from aliens could possibly be embedded in organic material in an asteroid, for example.
"If haste is unimportant, sending messages inscribed in some material can be strikingly more efficient than communicating by electronic waves," Professor Rose said.