What't is an hurricane? And why him to come-up? We have reponse to this hard question.

< What't is an hurricane? And why him to come-up? We have reponse to this hard question.

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CARTA STELLARE DEL MOMENTO

The Search for Extraterrestrial Life

Will living creatures arise on every planet where favorable physical conditions occur? No certain answer can be given, but those best qualified to judge the matter, the biologists, seem to think that life would in fact arise wherever conditions were able to support it. Accepting this, we can proceed with greater assurance. The extremely powerful process of natural selection would come into operation and would shape the evolution of life on each of these distant planets. Would creatures arise having some sort of similarity to those on the Earth? The distinguished biologist, C.D. Darlington, suggests that this is by no means unlikely. To quote Darlington's own words: "There are such great advantages in walking on two legs, in carrying one's brain in one's head, in having two eyes on the same eminence at a height of five or six feet, that we might as well take quite seriously the possibility of a pseudo man and a pseudo woman with some physical resemblance to ourselves....

A further question: Will travel between different planetary systems ever be possible? I am sorry to give an unpopular answer, but I believe this to be an uncompromising, no. Communication is a different matter. If living creatures at a high technological level exist on planets belonging to any of the nearest thousand stars it would be feasible to establish communication. A two-way interchange of information would take many centuries to develop. Even so, perhaps we should be starting now? (Hoyle, 1950)

Classification of Galactic Civilizations

Type I civilizations have a technological level close to the level presently attained on Earth. The energy consumption of Type I societies is approximately 4x10¹⁹ erg/s.

Type II civilizations have the capability of harnessing the energy radiated by their own star (4x10³³ erg/s). They may construct large Dyson Spheres to capture the energy from their primary star.

Type III civilizations are those who have an energy utilization equal to that of their galaxy (4x10⁴⁴ erg/s).

What Would a Sought-After Signal Look and Sound Like?

The narrower the band-width of a transmitted signal is of fixed total power, the greater the range of successful transmission. Thus, we can expect the signals to be of narrow band-width. This has the advantage of providing simple methods for distinguishing the signals from naturally occurring cosmic noise, which is extremely broad in band-width. For those using Microsoft's Internet Explorer you should hear what a narrow-band signal would sound like.

Detection Range of Cosmic Signals

Given an effective radiated power of the transmitter (in watts), the effective area of the receiving antenna (in square meters), the excess receiver noise temperature of the receiver used (in K), the averaging time of the receiver (in seconds), and the accepted band-width of the signal (in Hz), the range at which we can detect a signal transmitted by an intelligent civilization, is

R=8x10^-6(P_eA/T)^1/2(t/B)^1/4 light years.

where the constant is calculated from 1/[9.4608x10¹⁵(4pik)^1/2]. Here the constant is the number of meters per one light year, and k is the boltzmann constant.

A Good SETI Receiver Should

1. Operate at a frequency greater than 1420 MHz, with performance near 1420 MHz (21 cm) desirable. 2. Operate over a very large range of band-widths, including 10 MHz and less. 3. Have receiver frequency much less than the band-width during the averaging time of the receiver, specifically not more than about 1 MHz in several minutes. 4. Have the highest sensitivity available.