archive: RE: SETI The assumption

RE: SETI The assumption

Clements, Robert ( (no email) )
Mon, 17 May 1999 14:01:41 +1000

Taking your assumptions only - that the only plausible interstellar
trips are two-way, which i don't actually accept - how long do you
consider a lifetime to be: 100 years?; 200 years?; 1000 years?;
practically infinite? Since you accept that potential interstellar
technologies exist & that space-based power supplies need not be an
issue, the useful life-expectancy of a technological intelligence is one
of the major variables in assessing the value of interstellar travel
technologies... ie, a century-long round trip to the Alpha Centauri
system - perfectly feasible using a beamed energy/solar sail technology
- may seem an astonishingly heroic self-sacrifice for a race living for
just a century; but is a change of career for one living five centuries
or more. Since i see no reason for assuming that such roundtrips are
essential - unless a race is _extremely_ longlived, they really don't
make an awful lot of sense in a relativistic universe; notwithstanding
the fact that _an awful lot of sense_ & _universe_ aren't normally
expressions used in the close proximity to each other - you can halve
these journey times; which make them more plausible still....

(None of this should be taken as meaning that there aren't
transrelativistic approaches to travel: there may be, for all i know.
But it does negate your particular argument that such approaches are
essential for interstellar travel)

Intriguingly, Dan Goldin is on record as saying that he expects to
launch (robotic) interstellar probes within 40 years; but with
reasonable - ie, _not_ project-Apollo styled - experimental funding,
this estimate could be very conservative in the extreme. Manned missions
would take a lot longer, of course; not least because (i suspect) that
such missions won't be launched until we know we have something worth
sending people to on the other side....

All the best,

Robert Clements <>

>From: Jas[]
>Sent: Monday, May 17, 1999 11:36 AM
>To: Clements, Robert; seti
>Subject: Re: SETI The assumption
>I don't doubt that there are many energy sources to be harnessed in space.
>I expect is that the concept of propelling some craft can never attain a
>by which anyone can arrive somewhere in their lifetime, return to their home,
>communicate in either direction. 186,000 miles per second isn't fast enough.
>There must be some other 'transport' mechanism found for intersteller and
>intergalactic travel to make it feasible. When it is found, Arecibo will
>a huge planter for banana trees.
>J. Assenza
>"Clements, Robert" wrote:
>> Your basic assumption is wrong: assuming that advanced technological
>> intelligences are capable of living longer than the biblical three score
>> years & ten (something which is basically truer of the human race even
>> now), there are already a number of relativistic techniques on the table
>> which make interstellar travel possible.
>> (Intergalactic travel, on the other hand...)
>> The simplest to builds seems (currently) to be solar sails; with beamed
>> energy as a secondary (or even primary) power source. Theoretically: one
>> could create a kind of highway of beamed energy between two nearby star
>> systems, along which sailcraft could silently flow; & (assuming an
>> efficient means of turning stellar energy into a concentrated beam), the
>> process would essentially run on maintainence only....
>> All the best,
>> Robert Clements <>
>> <>
>> >----------
>> >From: Jas[]
>> >Sent: Saturday, May 15, 1999 12:29 AM
>> >To: Carl Sagan List;
>> >Subject: SETI The assumption
>> >
>> >Being new to this discussion, I will undoubedly raise questions that have
>> >already been discussed.
>> >I will certainly use the screen saver, given the choice between flying
>> >windows,
>> >etc.
>> >The premise of SETI is that any civilization will eventually discover, use
>> >and
>> >emit high frequency signals into the universe. What if this (fact) is
>> >a
>> >temporary phase for a century or two, followed by discovery of something
>> >better? After all, space exploration will require something much faster
>> >the speed of light to travel and communicate.
>> >The search could be for something so rare that discovery is nearly
>> >impossible.
>> >Joe Assenza
>> >
>New and Collectible items at Auction now at
>Meet Your Match! Extreme Online Personals: