Intergalactic messages 'in a bottle' are best
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----- Original Message -----
From: "Jan-H. Raabe" <y0001095@...-bs.de>
Sent: Monday, September 06, 2004 12:45 PM
Subject: Ufos in New Scientist
> Intergalactic messages 'in a bottle' are best
> 18:00 01 September 04
> NewScientist.com news service
> Rather than transmitting radio messages,
> extraterrestrial civilisations would find it far more
> efficient to send us a "message in a bottle" - some kind
> of physical message inscribed on matter. And it could
> be waiting for us in our own backyard.
> That is the conclusion of a new analysis of interstellar
> communications by Christopher Rose of Rutgers
> University in New Jersey and Gregory Wright, a
> physicist with Antiope Associates also in New Jersey.
> Assuming the aliens do not care how long it takes for
> their message to arrive, beaming a radio signal that can
> be detected 10,000 light years away, for instance,
> would take a million billion times as much energy as
> just shooting out matter in which data is embedded. "If
> energy is what you care about, it's tremendously more
> efficient to toss a rock," Rose says.
> Radiation loses out to rocks over long distances
> because it spreads out as it travels through space,
> diluting the signal below detection levels unless the
> beam is extremely powerful to begin with.
> Bottle throwing aliens
> If aliens are using a transmitter the size of the dish that
> astronomers on Earth use to look for their signal - the
> 305-metre radio telescope in Arecibo, Puerto Rico,
> which is the largest single-dish telescope on Earth -
> they would have to be closer than Saturn for the
> transmission to be more energy efficient than just
> flinging a bottle at us.
> If the Voyager space probes, which are now at the edge
> of the solar system, were each carrying three DVDs'
> worth of data, they would be a more energy-efficient
> way of sending information to someone 2000 light
> years away than an Arecibo-to-Arecibo radio
> Also, once radio signals pass they are gone for ever. So
> aliens would have to beam signals continuously, or
> other civilisations might blink and miss them. Physical
> objects stay where they land.
> Not everyone is convinced by Rose and Wright's
> analysis. "Their conclusion is that we should be looking
> for the Encyclopaedia Galactica within the Solar
> System," says Fred Walker, an astronomer at Stony
> Brook University in New York who is interested in the
> search for extraterrestrial intelligence. "I'm not sure I
> would expend any effort on this."
> However, Don Yeoman at NASA's Jet Propulsion
> Laboratory in Pasadena, California, who co-ordinates a
> project looking for asteroids on a collision course with
> Earth, accepts that their project could conceivably spot
> such alien objects. "It's not completely out of the
> Journal reference: Nature (vol 431, p 47)
> Jenny Hogan