Letters to Nature

Nature 431, 47-49 (2 September 2004) | doi:10.1038/nature02884; Received 8 April 2004; Accepted 16 July 2004

Inscribed matter as an energy-efficient means of communication with an extraterrestrial civilization

Christopher Rose1 & Gregory Wright2

  1. WINLAB, Department of Electrical and Computer Engineering, Rutgers University, Piscataway, New Jersey 08854, USA
  2. Antiope Associates, 18 Clay Street, Fair Haven, New Jersey 07704, USA

Correspondence to: Christopher Rose1 Email: crose@winlab.rutgers.edu

It is well known that electromagnetic radiation—radio waves—can in principle be used to communicate over interstellar distances1, 2. By contrast, sending physical artefacts has seemed extravagantly wasteful of energy, and imagining human travel between the stars even more so3, 4. The key consideration in earlier work, however, was the perceived need for haste. If extraterrestrial civilizations existed within a few tens of light years, radio could be used for two-way communication on timescales comparable to human lifetimes (or at least the longevities of human institutions). Here we show that if haste is unimportant, sending messages inscribed on some material can be strikingly more energy efficient than communicating by electromagnetic waves. Because messages require protection from cosmic radiation and small messages could be difficult to find among the material clutter near a recipient, 'inscribed matter' is most effective for long archival messages (as opposed to potentially short "we exist" announcements). The results suggest that our initial contact with extraterrestrial civilizations may be more likely to occur through physical artefacts—essentially messages in a bottle—than via electromagnetic communication.

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