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Transmitting from Earth
by Ray Norris, Head of Astrophysics, CSIRO Australia Telescope National Facility
rnorris @

Editor's Note: What follows is a message sent by Dr. Norris in reply to a request to use one of the CSIRO radio telescopes to transmit "greetings from Earth" into space. To Ray's list of recommended URLs dealing with the subject, we respectfully add the following three links:

Thanks for your note . . . requesting use of our facilites to send an announcement of humankind's presence to other civilisations. I regret that the ATNF has no transmitters, as all our research is done using passive (listening) equipment, and so we cannot help you.

However, I would like to discourage you from attempting to send such a message, and my guess is that other institutions will do likewise. You should be aware that you are likely to encounter substantial criticism in your endeavour, as it has been agreed by all relevant groups that we should not be actively sending out messages to try to reach other civilisations. Indeed, the last such attempt was in the early 60's at Arecibo. The storm of protest which followed this has discouraged other responsible groups from attempting any such experiment.

The argument is that, by sending out such a signal, you may be exposing the Earth to risk in some way. Although everybody agrees that the chance of this is tiny, it is argued that, as a matter of ethical principle, no small group of individuals should take it upon themselves to expose the earth to a risk without the consent of humanity (as represented by some body such as the UN). Although it can be argued that a great deal of electromagnetic radiation already routinely leaves the Earth, from TV stations, radar, etc., this is undirected, with a broad transmission beam, and so has a much smaller range than a directed transmission, beamed tightly towards a "likely" star. Furthermore, TV transmissions etc. have the implicit consent of humanity (since all nations operate such equipment). Therefore, using a large antenna to transmit a signal out to other solar-type stars does indeed, in principle, expose us to risk.

So, I would urge you to consider your position as a responsible corporate citizen, and consider the ethical aspects of what you are proposing, before you venture any further with this proposal.

For more information on these issues, I suggest you visit the WWW page of the SETI Institute on In particular, you will find a discussion paper, which raises some of the ethical questions involved, on

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