ARECIBO MESSAGE, AN INTERSTELLAR RADIO MESSAGE

Today, The Grandma has received the wonderful visit of one of her closest friends, Joseph de Ca'th Lon.

Josep likes Astronomy and they have been talking about the Arecibo message, that was broadcast from Puerto Rico, on a day like today in 1974.

The Arecibo message is an interstellar radio message carrying basic information about humanity and Earth that was sent to globular star cluster M13 in 1974.

It was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials. It has been noted that the low resolution of the image makes it infeasible for any extraterrestrial recipients to attach the intended meaning to most of its elements.

The message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope in Puerto Rico on 16 November 1974.

The message was aimed at the current location of M13, about 25,000 light years from Earth, because M13 was a large and relatively close collection of stars that was available in the sky at the time and place of the ceremony. When correctly translated into graphics, characters, and spaces, the 1,679 bits of data contained within the message form the image shown here.

The content of the Arecibo message was designed by Frank Drake, then at Cornell University and creator of the Drake equation, who wrote the message with help from Carl Sagan and others.

The message was meant more as a demonstration of human technological achievement than a serious attempt to enter into a conversation with possible extraterrestrials. Because globular cluster M13, at which the message was aimed, is more than 25,000 light-years from Earth, the message, traveling at approximately the speed of light, will take at least 25,000 years to arrive there.

By that time, the core of M13 will no longer be in precisely the same location because of the orbit of the star cluster around the galactic center. Even so, the proper motion of M13 is small, so the message will still arrive near the center of the cluster.

More information: SETI Institute

The message consists of seven parts that encode the following (from the top down in the image):

-The numbers one (1) to ten (10) (white)

-The atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up deoxyribonucleic acid (DNA) (purple)

-The formulas for the chemical compounds that make up the nucleotides of DNA (green)

-The estimated number of DNA nucleotides in the human genome, and a graphic of the double helix structure of DNA (white and blue, respectively)

-The dimension (physical height) of an average man (blue/white), a graphic figure of a human being (red), and the human population of Earth (white)

-A graphic of the Solar System, indicating which of the planets the message is coming from (yellow)

-A graphic of the Arecibo radio telescope and the dimension (the physical diameter) of the transmitting antenna dish (purple, white, and blue)

The entire message consisted of 1,679 binary digits, approximately 210 bytes, transmitted at a frequency of 2,380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 450 kW.

The ones and zeros were transmitted by frequency shifting at the rate of 10 bits per second. The total broadcast was less than three minutes.

The number 1,679 was chosen because it is a semiprime (the product of two prime numbers), to be arranged rectangularly as 73 rows by 23 columns. The alternative arrangement, 23 rows by 73 columns, produces an unintelligible set of characters (as do all other X/Y formats).

More information: NAIC

I think the universe is pure geometry -basically,
a beautiful shape twisting around and dancing over space-time.

Antony Garrett Lisi

AUGUST 15, 1977: 6EQUJ5, THE WOW! SIGNAL

The Wow! signal celestial location

Today it's the 40th anniversary of the Wow! signal. Joseph de Ca'th Lon wants to talk us about it.

The Wow! signal was a strong narrowband radio signal received on August 15, 1977 by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.

Astronomer Jerry R. Ehman discovered the anomaly a few days later while reviewing the recorded data. He was so impressed by the result that he circled the reading on the computer printout and wrote the comment Wow! on its side, leading to the event's widely used name.

More information: WOW Signal recieved at SETI on August, 15 1977

The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses have been advanced on the origin of the emission, including natural and man-made sources, but none of them adequately explains the result. The Wow! signal remains therefore the strongest candidate for an alien radio transmission ever detected.

Astronomer Jerry R. Ehman

In 1973, after completing an extensive survey of extragalactic radio sources, Ohio State University assigned the now-defunct Big Ear telescope, then located near the Perkins Observatory in Delaware, Ohio, to the scientific Search for ExtraTerrestrial Intelligence (SETI), in the longest-running program of its kind in history.

Over a decade earlier, in a 1959 paper, Cornell physicists Philip Morrison and Giuseppe Cocconi had speculated that any extraterrestrial civilization attempting to communicate via radio signals might do so using a frequency of 1420 megahertz, which is naturally emitted by hydrogen, the most common element in the universe and therefore likely familiar to all technologically advanced civilizations.

By 1977, Ehman was working at the SETI project as a volunteer; his job involved analyzing by hand large amounts of data processed by an IBM 1130 minicomputer and printed on perforated paper. While perusing data collected on August 15 at 22:16 EDT -02:16 UTC-, he spotted a series of values of signal intensity and frequency that left him and his colleagues astonished.

More information: Ohio History Central

The alphanumeric sequence circled by Ehman, 6EQUJ5, represents the intensity variation of the radio signal over time, measured as unitless signal-to-noise ratio and ranging from 0 to 36, with the noise averaged over the previous few minutes. Each individual character corresponds to a sample of the signal, taken every 12 seconds. A space character on the printout denotes an intensity between 0 and 1; the numbers 1 to 9 denote the correspondingly numbered intensities -from 1 to 9-; intensities of 10 and above are indicated by a letter: A corresponds to intensities between 10 and 11, B to 11 to 12, and so on. The highest measured value was U -an intensity between 30 and 31-, that is thirty times stronger than normal background noise.

Sky on August 15, 1977

A common misconception is that the Wow! signal constitutes some sort of message. 

In fact, what was received appears to be an unmodulated, continuous wave signal with no encoded information; essentially a flash of radio energy. 

The string 6EQUJ5 is merely the representation of the expected variation of signal intensity over time, expressed in the particular measuring system adopted for the experiment.

At the time of the observation, the Big Ear radio telescope was only adjustable for declination -or height above the horizon-, and relied instead on the rotation of the Earth to scan across the sky. Given the speed of Earth's rotation and the spatial width of the telescope's observation window, the Big Ear could observe any given point for just 72 seconds. A continuous extraterrestrial signal, therefore, would be expected to register for exactly 72 seconds, and the recorded intensity of such signal would display a gradual increase for the first 36 seconds -peaking at the center of the observation window- and then a gradual decrease. All these characteristics are present in the Wow! signal.

More information: Phys

The Wow! signal was a narrowband emission: its bandwidth was less than 10 kHz. The Big Ear telescope was equipped with a receiver capable of measuring fifty 10 kHz-wide channels. The output from each channel was represented in the computer printout as a column of alphanumeric intensity values. The Wow! signal is essentially confined to one column.

A person not familiar with all of the special knowledge about a particular instrument should not try to draw too many conclusions from printed data. Such data typically contains certain assumptions about the equipment not necessarily known to outsiders.
 

Jerry R. Ehman