View source for Arecibo message

{{short description|1974 message into space from the Arecibo Observatory}}
[[Image:Arecibo message.svg|125px|right|thumb|This is a demonstration of the message with color added to highlight its separate parts. The binary transmission sent carried no color information.]]

The '''Arecibo message''' is a 1974 [[interstellar radio message]] carrying basic information about humanity and Earth sent to [[Great Globular Cluster in Hercules|globular star cluster M13]]. It was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials.<ref name="phoneet" /> 
 
The message was [[Broadcasting|broadcast]] into space a single time via [[frequency modulation|frequency modulated]] [[radio waves]] at a ceremony to mark the remodeling of the [[Arecibo Observatory|Arecibo radio telescope]] in [[Puerto Rico]] on 16 November 1974.<ref name="phoneet">{{cite web|url=http://www.news.cornell.edu/releases/Nov99/Arecibo.message.ws.html |title=Cornell News: It's the 25th anniversary of Earth's first (and only) attempt to phone E.T. |date=Nov 12, 1999|accessdate=2008-03-29 |archiveurl=https://web.archive.org/web/20080802005337/http://www.news.cornell.edu/releases/Nov99/Arecibo.message.ws.html |archivedate=2008-08-02}}</ref><ref name="NYT-20170628">{{cite news |last=Johnson |first=Steven |title=Greetings, E.T. (Please Don't Murder Us.) |url=https://www.nytimes.com/2017/06/28/magazine/greetings-et-please-dont-murder-us.html |date=28 June 2017 |work=[[The New York Times]] |accessdate=28 June 2017 }}</ref> The message was aimed at the current location of M13 some 25,000 [[light year]]s away because M13 was a large and close collection of stars that was available in the sky at the time and place of the ceremony.<ref>{{cite web|url=http://www.zwire.com/site/news.cfm?newsid=15663534 |title=Making Contact |author=Larry Klaes |work=Ithaca Times |date=2005-11-30 |accessdate=2007-07-27 |archiveurl=https://web.archive.org/web/20090107165624/http://www.zwire.com/site/news.cfm?newsid=15663534 |archivedate=2009-01-07}}</ref> The message forms the image shown here when translated into graphics, characters, and spaces.<ref name=cassiday>{{cite web|url=http://www.physics.utah.edu/~cassiday/p1080/lec08.html|title=The Arecibo Message|last=Cassiday|first=George|accessdate=12 Oct 2013}}</ref>

==Description==

[[Frank Drake]], then at [[Cornell University]] and creator of the [[Drake equation]], wrote the message with help from [[Carl Sagan]] and others.<ref name="phoneet" /> The Arecibo message was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials.<ref name="phoneet" /> In fact, the core of M13, to which the message was aimed, will no longer be in that location when the message arrives.<ref name="phoneet" /> However, as the [[proper motion]] of M13 is small, the message will still arrive near the center of the cluster.<ref>{{cite web |url=http://www.science20.com/comments/28100/In_regard_to_the_email_from |title=In regard to the email from |author=Dave Deamer |date=December 4, 2009 |publisher=Science 2.0}}</ref>

The message consists of seven parts that encode the following (from the top down):<ref name=cassiday/>
*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 [[formula]]s for the [[Sugar (chemistry)|sugars]] and [[Base (chemistry)|bases]] in the [[nucleotides]] of DNA (green)
*The number of nucleotides in DNA, and a graphic of the double helix structure of DNA (white & blue)
*A graphic figure of a human, the dimension (physical height) of an average man, and the human population of Earth (red,  blue/white, & white respectively)
*A graphic of the [[Solar System]] indicating which of the planets the message is coming from (yellow)
*A graphic of the [[Arecibo Observatory|Arecibo radio telescope]] and the dimension (the physical diameter) of the transmitting antenna dish (purple, white, and blue)

The message consisted of 1,679 [[bit|binary digits]], approximately 210 [[byte]]s, transmitted at a frequency of 2,380&nbsp;[[hertz|MHz]] and modulated by shifting the frequency by 10&nbsp;Hz, with a power of 450 [[kilowatt|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.<ref name="phoneet" /><ref>{{cite web|author=Jay M. Pasachoff|title=Chapter 20: Life in the Universe|work=Williams.edu|url=http://www.williams.edu/Astronomy/jay/ETU5/chapter20_5th.html| accessdate=2007-05-05}}</ref>

The number 1,679 was chosen because it is a [[semiprime]] (the product of two [[prime number]]s), to be [[raster scan|arranged rectangularly]] as 73 rows by 23 columns.<ref>{{cite book |last1=Oberhaus |first1=Daniel |title=Extraterrestrial Languages |date=2019 |publisher=MIT Press |isbn=978-0-262-04306-9 |page=171 |url=https://books.google.com/?id=2CWzDwAAQBAJ |language=en}}</ref> [[:File:AreciboMessageShifted.svg|The alternative arrangement]], 23 rows by 73 columns, produces an unintelligible set of characters (as do all other X/Y formats).

===Numbers===
[[Image:Arecibo message part 1.png|Part 1 — The numbers from 1 to 10|right]]

 1 2 3 4 5 6 7 8  9  10
 ----------------------
 0 0 0 1 1 1 1 00 00 00
 0 1 1 0 0 1 1 00 00 10
 1 0 1 0 1 0 1 01 11 01
 X X X X X X X X  X  X <-least-significant-digit marker

The numbers from [[1 (number)|1]] to [[10 (number)|10]] appear in [[Binary numeral system|binary]] format (the bottom row marks the beginning of each number).

Even assuming that recipients would recognize binary, the encoding of the numbers may not be immediately obvious because of the way they have been written. To read the first seven digits, ignore the bottom row, and read them as three binary digits from top to bottom, with the top digit being the most significant. The readings for 8, 9 and 10 are a little different, as they have been given an additional column next to the first (to the right in the image). This is intended to show that numbers too large to fit in a single column can be written in several contiguous ones, where the additional columns do not have the least-significant-digit marker.

=== DNA elements ===
[[Image:Arecibo message part 2.png|Part 2 — The elements constituting DNA|right]]

 H C N O P
 1 6 7 8 15
 ----------
 0 0 0 1 1
 0 1 1 0 1
 0 1 1 0 1
 1 0 1 0 1
 X X X X X

The numbers 1, 6, 7, 8, and 15 appear. These are the [[atomic numbers]] of [[hydrogen]] (H), [[carbon]] (C), [[nitrogen]] (N), [[oxygen]] (O), and [[phosphorus]] (P), the components of DNA.

===Nucleotides===
{| style="width: 100%; font-size: 16px; line-height: 20px"
|-
| rowspan="6" style="width: 0%; height: 306px" | [[Image:Arecibo message part 3.png|Part 3 — The nucleotides of DNA]]
| colspan="5" style="width: 100%; height: 59px" |
|-
| style="padding-left: 1.5em" | [[Deoxyribose]]<br />(C<sub>5</sub>H<sub>7</sub>O)
| style="padding-left: 1.5em" | [[Adenine]]<br />(C<sub>5</sub>H<sub>4</sub>N<sub>5</sub>)
| style="padding-left: 1.5em" | [[Thymine]]<br />(C<sub>5</sub>H<sub>5</sub>N<sub>2</sub>O<sub>2</sub>)
| style="padding-left: 1.5em" | Deoxyribose<br />(C<sub>5</sub>H<sub>7</sub>O)
| style="width: 100%; height: 47px" |
|-
| style="padding-left: 1.5em" | [[Phosphate]]<br />(PO<sub>4</sub>)
|
|
| style="padding-left: 1.5em" | Phosphate<br />(PO<sub>4</sub>)
| style="width: 100%; height: 47px" |
|-
| style="padding-left: 1.5em" | Deoxyribose<br />(C<sub>5</sub>H<sub>7</sub>O)
| style="padding-left: 1.5em" | [[Cytosine]]<br />(C<sub>4</sub>H<sub>4</sub>N<sub>3</sub>O)
| style="padding-left: 1.5em" | [[Guanine]]<br />(C<sub>5</sub>H<sub>4</sub>N<sub>5</sub>O)
| style="padding-left: 1.5em" | Deoxyribose<br />(C<sub>5</sub>H<sub>7</sub>O)
| style="width: 100%; height: 47px" |
|-
| style="padding-left: 1.5em" | Phosphate<br />(PO<sub>4</sub>)
|
|
| style="padding-left: 1.5em" | Phosphate<br />(PO<sub>4</sub>)
| style="width: 100%; height: 47px" |
|-
| colspan="5" style="width: 100%; height: 59px" |
|}

The [[nucleotides]] are described as sequences of the five atoms that appear on the preceding line. Each sequence represents the [[molecular formula]] of the nucleotide as incorporated into DNA (as opposed to the free form of the nucleotide).

For example, deoxyribose (C<sub>5</sub>H<sub>7</sub>O in DNA, C<sub>5</sub>H<sub>10</sub>O<sub>4</sub> when free), the compound in the top left in the image, is read as:

 11000
 10000
 11010
 XXXXX
 -----
 75010

i.e., 7 atoms of hydrogen, 5 atoms of carbon, 0 atoms of nitrogen, 1 atom of oxygen, and 0 atoms of phosphorus.

===Double helix===
[[Image:Arecibo message part 4.png|Part 4 — The DNA double helix structure|right]]

 11
 11
 11
 11
 11
 01
 11
 11
 01
 11
 01
 11
 10
 11
 11
 01
 X

 11111111 11110111 11111011 01011110 (binary)
 = 4,294,441,822 (decimal)

DNA double [[helix]]; the vertical bar represents the number of nucleotides. The value depicted is around 4.3 billion, which was believed to be the case in 1974 when the message was transmitted. There are approximately 3.2 billion base pairs in the human [[genome]].

===Humanity===
{|
| style="vertical-align: top" |[[Image:Arecibo message part 5.png|Part 5 — Human form, the height and population of humans|thumb]]
|<pre style="width:35em">  ʌ             X011011
  |              111111
  |              110111
X0111            111011
  |              111111
  v              110000
</pre>
 1110 (binary) = 14 (decimal)

 000011 111111 110111 111011 111111 110110 (binary)
 = 4,292,853,750 (decimal)
|}
The element in the center represents a human. The element on the left (in the image) indicates the average height of an [[Average human height by country|adult male in the US]]: {{cvt|1.764|m|ftin|1}}. This corresponds to the horizontally-written binary 14 multiplied by the [[wavelength]] of the message (126&nbsp;mm). The element on the right depicts the size of human population in 1974, approximately 4.3&nbsp;billion (which, coincidentally, is within 0.1% of the number of DNA nucleotides). In this case, the number is oriented in the data horizontally rather than vertically. The least-significant-digit marker is in the upper left in the image, with bits going to the right and more significant digits below.

===Planets===
[[Image:Arecibo message part 6.png|Part 6 — The Sun and the planets|left]]
<pre style="width: 60em">                  Earth
Sun Mercury Venus       Mars Jupiter Saturn Uranus Neptune Pluto</pre>
{{clr}}

The [[Solar System]], showing the [[Sun]] and the planets in the order of their position from the [[Sun]]: [[Mercury (planet)|Mercury]], [[Venus]], [[Earth]], [[Mars]], [[Jupiter]], [[Saturn]], [[Uranus]], [[Neptune]], and [[Pluto]]. (Pluto has since been [[Pluto#IAU classification|reclassified]] as a [[dwarf planet]] by the [[International Astronomical Union]], but it was considered a planet at the time the message was transmitted.)

The Earth is the third planet from the [[Sun]]; its graphic is shifted up to identify it as the planet from which the signal was sent. Additionally, the human figure is shown just above the Earth graphic.

In addition to showing position, the graphic provides a general, not-to-scale size reference of each planet and the Sun.

===Telescope===
[[Image:Arecibo message part 7.png|Part 7 — The Arecibo radio telescope|left]]
[[File:The Arecibo Observatory 20151101114231-0 8e7cc c7a44aca orig.jpg|thumb|A photograph of the Arecibo radio telescope]]
<div style="white-space:nowrap"><pre style="width: 35em">bottom two rows:
     100101
<--- 111110X ---></pre><pre style="width: 35em">100101 111110 (binary) = 2,430 (decimal)</pre></div>

{{clr}}

[[Image:AreciboMessageShifted.svg|The Arecibo message as decoded into 23 rows and 73 columns, although unintelligible, the message in this format appears sufficiently organized to show that it is not a random signal.|thumb|right]]

The last part represents the [[Arecibo radio telescope]] with its [[diameter]]: 2,430 multiplied by the wavelength gives {{cvt|306.18|m|ftin|0}}. In this case, the number is oriented horizontally, with the least-significant-digit marker to the lower right in the image. The part of the image that resembles a letter "M" is there to demonstrate to the reader of the message that the curved line is a [[paraboloid]] mirror.

[[Image:Chilbolton_crop_circle.svg|125px|right|thumb|The Arecibo reply was the name given to a crop circle that appeared in farmland next to the Chilbolton radio telescope in Hampshire, UK, on 19 August 2001. It was 75 feet wide and 120 feet long. The design is so named because it appears to be a response to the Arecibo message, which SETI transmitted into space in 1974.]]

==Arecibo answer hoax==
The "Arecibo answer" is a hoax by people that created an imprint in a crop field ([[crop circle]]) in 2001 near the [[Chilbolton Observatory|Chilbolton radio telescope]] in [[Hampshire, UK]], portrayed as a response from an extraterrestrial civilization. The crop circle is a near replica of the Arecibo message. The feature forms the same 23 x 73 grid because these numbers are primes and most of the chemical data remains the same with the exception that in the section detailing important chemical elements, the main focus is altered from [[carbon]] to [[Hypothetical_types_of_biochemistry#Silicon_biochemistry|silicon]], and the diagram of DNA has been rewritten. At the bottom, the pictogram of a human is replaced with a shorter figure with a large, bulbous head.<ref>{{Cite web|title=Is the Latest Crop Circle a Message from E.T?|work=[[SETI|SETI.org]]|url=http://seti.org/general/ao_message_crop.html|archive-url=https://web.archive.org/web/20041013062350/http://seti.org/general/ao_message_crop.html|archive-date=2004-10-13|access-date=2019-11-18}}</ref><ref>{{cite web|url=https://qrius.com/arecibo-message/|last=Chitnavis|first=Urvashi|title=The Arecibo Message: What happened when humanity tried to communicate with aliens|date=2018-03-30|website=Qrius|language=en-GB|access-date=2019-11-18}}</ref><ref>{{cite news|last=Griffin|first=Andrew|title=Arecibo message: What happened when people claimed aliens contacted them – and why we might never want to|newspaper=[[The Independent]]|location=London|pages=|language=|publisher=|date=2018-11-16|url=https://www.independent.co.uk/life-style/gadgets-and-tech/news/arecibo-message-decoded-meaning-google-doodle-reply-audio-response-explained-a8636856.html|access-date=2019-11-18}}</ref>

[[Image:Chilbolton_crop_circle.svg|125px|right|thumb|The Arecibo reply was the name given to a crop circle that appeared in farmland next to the Chilbolton radio telescope; in Hampshire, UK, on 19 August 2001. It was 75 feet wide and 120 feet long. The design is so named because it appears to be a response to the Arecibo message, which SETI transmitted into space in 1974.]]

==See also==
{{Portal|Astronomy|Biology}}
* [[Active SETI]]—METI (Messaging to Extra-Terrestrial Intelligence)
* [[METI (Messaging Extraterrestrial Intelligence)]]
* [[A Message from Earth]]
* [[Communication with Extraterrestrial Intelligence]] (CETI)
* [[Cosmic Call]]
* [[Pioneer plaque]]
* [[Voyager Golden Record]]
* [[Wow! signal]]

== References ==
{{reflist|30em}}

==External links==
{{commons category|Arecibo message}}
* [https://www.seti.org/seti-institute/project/details/arecibo-message SETI homepage on the message]
* [http://www.cplire.ru/html/ra&sr/irm/index.html Interstellar Radio Messages]
* [http://www.physics.utah.edu/~cassiday/p1080/lec06.html The Arecibo Message explained]
* [https://www.fourmilab.ch/goldberg/setimsg.html Self-Decoding Messages]

{{Interstellar messages}}

[[Category:Interstellar messages]]
[[Category:Search for extraterrestrial intelligence]]
[[Category:Time capsules]]
[[Category:Technology in society]]
[[Category:1974 in science]]
[[Category:1974 in Puerto Rico]]