archive: Re: SETI modulation of ETI transmission

Re: SETI modulation of ETI transmission

Dr. H. Paul Shuch ( (no email) )
Sun, 30 Aug 1998 10:03:18 -0400

At 16:26 08/29/1998 -0400, Matthew G Cheung wrote:

>I also had a strange idea. Is it possible for another civilization to
>move just perfectly so there is no apparent doppler shift. This might
>make a candidate signal look terrestrial.

For this to happen, Matthew, the two planets would have to have the same
radius, and the same rotational rate (but in opposite directions), and the
observers would have to be at the same latitude, pointing at the same
relative azimuth and elevation. Yes, that's theoretically possible, but
the beauty of the Doppler test is that it's different for different
observers at different locations, so that if one station in the Argus
network were so fooled, the others wouldn't be. Then too, such
synchronized planetary rotation would change the time the signal stayed in
the antenna's beamwidth (assuming a directional antenna), so the
amplitude-over-time pattern would be decidedly non-terrestrial.
You can fool all of the stations some of the time, and some of the
stations all of the time, but you can't fool Project Argus.
H. Paul Shuch, Ph.D. -- Executive Director, The SETI League, Inc.
433 Liberty Street, PO Box 555, Little Ferry NJ 07643 USA
voice (201) 641-1770; fax (201) 641-1771; URL
email work:; home:
Project Argus Observatory FN11lh

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