E.T. FIRST CONTACT 'WITHIN 20 YEARS ?
If intelligent life exists elsewhere in our galaxy, advances in computer processing power and radio telescope technology will ensure we detect their transmissions within two decades. That is the bold prediction from a leading light at the Search for Extraterrestrial Intelligence Institute in Mountain View, California.
Seth Shostak, the SETI Institute's senior astronomer, based his prediction on accepted assumptions about the likelihood of alien civilisations existing, combined with projected increases in computing power.
Shostak, whose calculations will be published in a forthcoming edition of the space science journal Acta Astronautica, first estimated the number of alien civilisations in our galaxy that might currently be broadcasting radio signals.
For this he used a formula created in 1961 by astronomer Frank Drake which factors in aspects such the number of stars with planets, how many of those planets might be expected to have life, and so on. Shostak came up with an estimate of between 10,000 and one million radio transmitters in the galaxy.
To find them will involve observing and inspecting radio emissions from most of the galaxy's 100 billion stars. The time necessary for this formidable task can be estimated from the capabilities of planned radio telescopes such as SETI's 1-hectare Allen Telescope Array and the internationally run Square Kilometre Array and expected increases in the power of the microchips that sift through radio signals from space.
Alien civilisation
Shostak assumed that computer processing power will continue to double every 18 months until 2015 as it has done for the past 40 years. From then on, he assumes a more conservative doubling time of 36 months as transistors get too small to scale down as easily as they have till now.
Within a generation, radio emissions from enough stars will be observed and analysed to find the first alien civilisation, Shostak estimates. But because they will probably be between 200 and 1000 light years away, sending a radio message back will take centuries.
Paul Shuch, executive director of the SETI League, a separate organisation in New Jersey, says Shostak's prediction ignores one important factor. "It is altogether reasonable to project the development of human technology, based upon past trends and planned investments," he says.
"But predicting the date, the decade or even the century of contact is another matter because the 'other end' of the communications link is completely out of our hands. It would be nice to think we know something about the existence, distribution, technology and motivation of our potential communications partners in space, but in fact, we don't."
Shostak admits that there are myriad uncertainties surrounding his prediction, but he defends the basis on which he made it. "I have made this prediction using the assumptions adopted by the SETI research community itself."
DES EXTRA-TERRESTRES DANS 20 ANS?
C'est ce qui s'appelle prendre un risque. D'ordinaire, les chercheurs d'extra-terrestres demeurent dans le vague, afin d'être certains de ne pas être contredits. Cette fois, voici l'un de leurs chefs de fil qui annonce un premier contact "d'ici 20 ans".
Seth Shostak, astronome principal à l'Institut SETI (Search for Extra-terrestrial Intelligence) de Mountain View (Californie), vient en effet de prédire que si de la vie intelligente existe ailleurs dans notre galaxie, les progrès de l'informatique (pour le traitement de quantités massives de données) et de la radio-astronomie, permettront de détecter leurs transmissions d'ici deux décennies. Ses calculs sont publiés dans la prochaine édition du journal Acta Astronautica.
Mais ses calculs reposent sur plusieurs hypothèses: tout d'abord, la quantité possible de civilisations dans notre galaxie, sur la base de "l'équation de Drake" (nombre d'étoiles avec des planètes, nombre de ces planètes pouvant abriter la vie, etc.); or, comme les scientifiques ne peuvent que spéculer sur les variables de cette équation, le nombre de civilisations, dans l'estimation de Shostak, varie entre 10 000 et un million. Mais s'il n'y en avait que 1000?
Ensuite, la radio elle-même, que l'on suppose être universelle. Mais si une civilisation extrêmement avancée n'utilisait plus la radio depuis longtemps, tout comme nous avons laissé derrière nous les signaux de fumée?
"Prédire la date, la décennie ou même le siècle du contact est une autre paire de manches", s'objecte un membre de la communauté SETI, Paul Shuch, dans les pages du New Scientist. "Parce que "l'autre extrémité" de cette communication est complètement en dehors de notre contrôle. Ce serait bien d'imaginer que nous connaissons quelque chose sur l'existence, la distribution, la technologie et les motivations de nos partenaires potentiels de l'espace, mais dans les faits, nous ne savons rien du tout."
Sources :
http://www.sciencepresse.qc.ca/archives/2004/cap0208041.html
http://www.newscientist.com/article.ns?id=dn6189
CRUCRAS/YL