Re: How could we transmit information to a far distant culture 250Myrs from now

Well I'm stumped as well.  I tried out this question on a few likely 
suspects but no cigar.  My best guess would be to put the information on a 
large monument (great pyramid) on a 'dead' planet like the moon.  Actually 
you'd want several such monuments, just in case a big chunk of rock smashes 
into one or more over 250 Myears.  Maybe you could find someplace(s) on 
Earth, but that is something you geologists would know far better than I.

Another strategy would be to encode the information into the 'junk' DNA of 
some very persistent organism -- blue-green algae have made it through 
billions of years.  But I'm no geneticist, it could well be that changes in 
the genome would garble the information.  On the other other hand, one could 
use the kind of error correcting encoding schemes used for computer data 
storage.  Hey!  Maybe that's what all that 'junk' in the human genome is...  
(Old idea: shaggy dog story --> it says "Don't forget the milk'-- I forget 
the author's name.)

The really hard question to my way of thinking is what kind of message would 
be meaningful to the strange beings that will exist on the Earth in 250 
Myears.  It's rather like the SETI anti-cryptography problem.  IMHO, all the 
"good stuff" is impossible to communicate in any simple way.  Sure, you can 
communicate the Pythagorean Theorem or something -- but they/we already knew 
that in the first place.  Something interesting, a T. S. Eliot poem for 
example, is going to be (nearly?) impossible to pass on to some being with 
no intellectual/cultural/emotional referents in common with us.  The most 
important message that is easily communicated is just the fact we exist(ed), 
i.e. "Kilroy was here". 

For another perspective, take a look at 
 http://www.longnow.org