Wednesday, December 8, 2010

Alien Talk: SETI

Today, alien is one of the most fascinating word for anyone at any part of globe. People are very much aware about the questions like- Who do we call Aliens? Etc.

On the other hand if we ask someone about SETI, only one in a group of eight persons will be able to answer. This is really sad.

The reason for writing this blog is to create awareness about SETI, its objectives and goals along with its history among the mass. You can also clear you questions and misconceptions about aliens and SETI at this blog by writing us.

The major topics which in general an article on Aliens and SETI should cover are:- Foundation of SETI Research, Spinning Neutron Stars or Pulsars, Project Ozma and Drake Equation. We will be covering all of this in various blog posts.

SETI stands for Search for Extra-terrestrial Intelligence. It is the science of search for the existence of any alien race, by detecting the various signals coming from the outer space, for the search of an artificial signal from any alien civilization.The idea of SETI was laid in year 1959 after the publication of a paper in British journal Nature by Giuseppe Cocconi and Philip Morrison. In this paper, the probability of the existence of any alien civilization and the means to detect there existence were discussed.
Radio waves were chosen as the means of communication because of their capability to travel huge distances between stars, and also for their generation with comparatively less power. The signals that we commonly use like the radio signals, television signals, satellite signals, and the radar signals are being spread at the various parts throughout the galaxy and the universe, so there is also a great possibility that these signals might have already been detected by someone.

At about the same time when Cocconi and Morrison’s paper got published an astronomer Frank Drake was laying the foundation of the first SETI research. His search was named as Project Ozma and begun in year 1960. In Project Ozma, the two nearest sun like stars, namely, Tau Ceti and Epsilon Eridani were detected for an artificial signal, in other words, an alien signal. However, Project Ozma could not detect an alien signal but it laid the foundation for SETI searches.

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Foundation Of SETI Research

In year 1959, Philip Morrison and Giuseppe Cocconi were physicists atCornell University. They were both, very interested in gamma rays. "One spring day in 1959," said Morrison, "my ingenious friend Giuseppe Cocconicame into my office and posed an unlikely question: would not gamma rays, he asked, be the very medium of communication between the stars?" Morrisondid agreed suggesting them to consider entire electromagnetic spectrum for possibility.  

Dr. Philip Morrison

The Image above of Dr. Philip Morrison was taken in the month of September, 1959 Morrison and Cocconi published a short article with heading-“Searching for Interstellar Communications”. In this article they admitted that it is impossible to estimate the probability of the existence of any alien civilization on any distant planet orbiting some star. They believed that if the alien race is more technologically advanced in our comparison, then they will surely try to make contact. But the question that was killing them was the way of communication that the alien race would choose.

On long argument Morrison and Cocconi came to the conclusion, that the aliens should use electromagnetic waves like the radio waves and the light waves for communication with us.
After this, they moved to the second critical question which was regarding the frequency at which the aliens should transmit their signals.
Morrison and Cocconi argued that the most rational frequencies for the communication between the stars were between 1 and 10,000 MHz. At these frequencies the interference of planetary atmosphere interferenceis minimum with the electromagnetic signals.
Frequency range of 10,000 MHz was still very wide for conducting any systematic search. As a result Morrison and Cocconi therefore guessed that the aliens would most probably use the frequency of 1420 MHz as this is the emission frequency of the most common element in the universe-Hydrogen.
Thereafter, another great observation was made on the Doppler shift. It was stated that the signal sent from the aliens planet to our planet will necessarily drift from its actual frequency as a result of Doppler shift. Since the planets are not moving at relatively constant speed, therefore, the frequency of transmission will definitely drift over time. Therefore, the search for alien signal begun taking this deviation into account. 

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Drake Equation

The question of the number of communicating civilizations in our galaxycould, in Drake's view, be reduced to seven smaller issues:
The rate of star formation in our galaxy at the time our Solar System was formed (R*);
The fraction of stars that have planets around them (fp);
The number of planets per star that are capable of sustaining life (ne);
The fraction of planets in ne where life evolves (fl);
The fraction of fl where intelligent life evolves (fi);
The fraction of fi that communicate (fc);
The lifetime of a communicating civilization (L);
Denoting the number of communicating civilization in our galaxy by N, and multiplying the different elements, we get the famous Drake Equation:
N= R* fp ne fl fi fc L  

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Project Ozma

This image Dr. Frank Drake was taken in 1990.

Almost at the same time when Morrison andCocconi were discussing on the alien signal an astronomer Frank Drake was performing his ownresearch on interstellar communications. He was a junior staff member of National Radio Astronomy ObservatoryNRAO, situated in West Virginia. Drake was a graduate student of radio astronomy and he once detected a strong radio signal from the direction of Pleiades, which seemed to be an artificial signal. Analysis of a few weeks led him to the conclusion that the signal was originated on the Earth itself but the possibility of it being an alien signal remained strong in his mind.
Later in the month of March in year 1959Drake calculated that the radio telescope at which he detected the signal was capable to detect a signal transmitted from a distance of about 10 light years. He thereafter noted, within a distance of 10 light years from sun there are many sun like stars. This was a good reason for Drake to begin search for the existence of an alien intelligence.
Drake proposed to use the new radio telescope at NRAO for the search of extraterrestrials to the director of NRAO. His proposal was accepted and Drake dubbed a venture named “Project Ozma”.
For cost saving reasons, Drake and his colleagues concentrated on thehydrogen 1420 MHz band. This was the frequency at which the radio telescopes most commonly work, so the alteration required was very less.

Project Ozama Radio Telescope
Having a fear for their respect, Drake and his colleagues kept the Project Ozmaa secret. However, when the project was revealed, public support turned to give a positive response in terms of support and valuable donations in terms of money as well as equipments.
When Drake heard about the publication of Morrison and Cocconi’s article he was very pleased that such prominent researchers provided a theoretical support for searching at the same frequency that he chose, even though for different reasons.
Ozma began to operate in April, 1960 concentrating at the reception of signalsfrom the two closest sun like stars namely, Tau Ceti and Eridani.
Although, the expectations were very high but project Ozma could not detect asignal from any alien race and was shut down. It was however, a very remarkable model for most future SETI projects.

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Spinning Neutron Stars or Pulsars

Jocelyn Bell was a research student in radio astronomy at Cambridge. As a part of her research work she was monitoring a new radio telescope. She was looking for the signs of interplanetary scintillation and quasars by scanning the sky with the radio telescope she was monitoring. In summer of 1967, when her research was going well, she observed some unexplained signal kept repeating itself in all her charts. At a prior stage Bell and her advisor, Tony Hewish, thought that this signal is because of some radio interference. But soon they realized that the signal was coming, somewhere from outer space.
On further investigation, they found something very remarkable in the signal. They found that the signal pulsated at regular intervals, 3 and 2/3 of a second part. In 1967, no one had an answer to such strange signal and people begun to suspect that it was a transmission from an alien civilization. They begun referring the source of the signal as LGM, standing for “little green men”.
Jocelyn Bell at the Cambridge Radio Telescope 

Further researches gave the answer to this strange signal. Finally, it was observed that the LGM had nothing to do with an alien civilization and it was rather coming from the rapidly spinning neutron stars, which were given the name pulsars.

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