ASTROBIOLOGY PART III-EXTRA TERRESTRIAL COMMUNICATION

 The first person who thought of communicating with aliens was Friedrich Gauss. In 1822 he suggested setting up of an array of 100 huge mirrors to reflect sunlight towards the moon. It was then believed that life existed on the moon and he felt it would be great to communicate with it.

Later when better observations made the moon lifeless, the attention then shifted to Mars. In 1892 the French astronomer Camille Flammarion proposed that huge geometric shapes be prepared on the Earth to be visible to the Martians. Then Marconi came in created the method of transmission of Radio waves.

In about 1900 Tesla heard something that looked like structured signals to him. However, he did not document it and merely mentioned about it. In all probability, it is more of his imagination than reality. Whether Tesla heard anything or not that gave rise to a new idea, that alien radio messages might be detectable to us and it had been given a name; SETI or Search for Extra Terrestrial Intelligence.

Seen in the visible light galaxies are made up of billions of stars. But there is another component that is more traceable to unravel their structure and that is the all-pervasive Hydrogen gas. It is far too cold to produce light at visible wavelengths, but it generates a prominent spectral line with a wavelength of 21 cm.

Spectral lines are characteristic signatures produced by different types of atoms. This particular one, the 21 Cm neutral Hydrogen line occurs much further down on the Electromagnetic spectrum than the visible light at a radio frequency of 1420 MHz. This magic frequency allows Radio astronomers to scan the galaxies much farther than what can be done with visible light.

Currently, most of our Astronomy is dependent on the analysis of Spectral lines. Because of them, Astronomers can detect the star's chemical composition as well as so much more data including the star's weight, density, distance, luminosity, and so on.

What is this Spectrometry on which a lot of theory of Astronomy is based on?

In an atom, an electron sometimes jumps from a high energy orbit to a lower energy orbit and emits the surplus energy as radiation. Similarly, sometimes an electron jumps from a lower energy orbit to a higher energy orbit which involves absorption of energy. In these cases, there is either release or absorption of energy which emits a specific wavelength of radiation.

If we look at the star through a Telescope we see a combination of all the visible wavelengths it emits. It is possible to split the wavelength in the Spectrometer to reveal the quantum jumps that are going on in the atoms.

Downward jumps produce emission lines that are brighter than the background spectrum and upward jumps produce darker absorption lines. By measuring the wavelength of the line, scientists can measure which element has produced it. Very low energy jumps would produce longer wavelengths associated with the radio waves. That is where the 21 cm Hydrogen line comes in.

The 21 Cm Hydrogen line was originally recognized as a window into galactic structure by Danish astronomer Jan Oort. He is better known for the Oort cloud (a cloud of planetesimals surrounding the Sun at distances from 2000 AU to 200,000 AU). AU is the Astronomical Unit which is nothing but the distance of the Earth from the Sun which is about 151 million Km.

Oort used the 21 Cm line to show that our galaxy as well as many other galaxies is spiral in shape. This can never be seen with visible wavelengths.

In 1959 “Nature” published an article saying that if the aliens were to set up a signal to let beings on other planets know that the aliens exist, nothing is better than to use the frequency of 1420 Mhz corresponding to the 21 Cm Hydrogen line.

The first person to put SETI into practice was Frank Drake (the fame of the Drake Equation for postulating the number of possible civilizations in the Universe) . He did it at the Green Bank Radio Observatory in West Virginia. He pointed the giant dish at 2 stars, Tau Ceti & Epslion Eridani, and listened on the critical frequency of 1420 Mhz but he could get nothing out of it.

I had already posted in another article about the Drake equation for postulating the number of civilizations in the Universe. The problem is too many variables in the equation are inexact and therefore the result would not be in confirmation with reality. Nevertheless, it takes into account all the variables and tries to arrive at some figure rather than leaving it to our wild guesswork and also to show that SETI is not really a waste of time.

In the 6 decades after Frank Drake pointed the Greenbank telescope at the 2 stars the SETI experiment yielded nothing except for a couple of explainable anomalies. The problem with SETI is it expects the aliens to transmit at the 1420 Mhz frequency. Perhaps that is naïve because we are projecting the human ways of thinking onto other civilizations. They may not use radio waves as we do but use some other medium to communicate, we never know.

The biggest problem for SETI is that it is not funded by any country but it is a private project. The funding comes from various private individuals. The Russian billionaire Yuri Milner is funding a 100 million USD program of SETI.

Now, even if we get a message from the aliens, how do we decipher it? The most famous of the messages sent by mankind at the initiative of SETI through the Arecibo dish. This is a 300 meter dish antenna at Arecibo in Puerto Rico. The problem with this dish is that it is built into a natural depression in the landscape and hence cannot choose other directions. Through this dish in 1974 a message was transmitted to the Globular cluster in Hercules 24000 light years away. So, it would take 24000 years to get there. The message contained brief description of the DNA, pictures of human beings, the solar system and the Arecibo telescope itself.

NASA’s Pioneer 10 & 11 carried gold-plated messages which are now heading out of the solar system. However, it would take a fantastic 4 million years before they get anywhere near another solar system.

Both Carl Sagan and later Stephen Hawking said that sending such messages to another aggressive civilization can be dangerous as those would make them spot us and destroy us. But to me, their reasoning looks flawed. Their coming here would mean they have to master the speed of light. If they can do that, then the technology of their instruments would be such that they can easily discover other life forms on other planets, if they do exist. So our helping hand to them would be utterly unnecessary.