User:Daylightless/Communicating With Aliens

Speculation on the nature of extraterrestrial life has existed in one form or another since ancient times when it was still believed that the earth was the centre of the universe, in the form of mythological worlds populated by gods and other fantastical beings. Over time this developed into serious consideration of life on planets orbiting stars other than our own, as well as other bodies in the solar system, most prominently Mars and the Moon. Although the possibility of advanced life anywhere in the solar system has been essentially ruled out with advances in our own telescopes, as well as expeditions to the moon and mars, the idea of establishing communication with civilisations around other stars has been gaining momentum since the 1960’s, when the first attempts to detect alien communications were made. In this article, the reasons, methods, projects and technology behind both detecting alien transmissions and sending our own detectable transmissions into space will be discussed.

SETI
Since 1960, a number of projects have emerged with the intention of detecting signals sent by intelligent extraterrestrial life, under the name SETI, or Search for Extra-Terrestrial Intelligence, seeded by the 1959 paper, “Searching For Interstellar Communications” by Philip Morrison and Giuseppe Cocconi.

Previous SETI Projects

The first such of the these projects, Project Ozma, was founded in 1960 by astronomer Frank Drake at the National Radio Astronomy Observatory in West Virginia, in which two stars Epsilon Eridani and Tau Ceti were observed with a 26m radio telescope over a period of four months, looking for signals in the 21cm band. No legitimate signals were detected. Between 1973 and 1995, Ohio State University’s Big Ear Observatory ran the longest single search for extraterrestrial signals, lasting 22 years. The only signal of note detected was the famous “Wow!” signal, but the project failed to observe the signal a second time. The NASA High Resolution Microwave Survey, which was cancelled in the 1990’s, consisted of a pair of searches; a targeted search aimed at star systems within 100 light years, attempting to detect weak signals from sun-like stars, and an all-sky survey, which attempted to detect very powerful, constant beacons. The project used several antennas. Its funding was pulled early in the 1990’s, but the privately funded Project Phoenix replaced it.

Current SETI Projects:

Project Phoenix: Named for rising from the ashes of the scrapped NASA HRMS, Project Phoenix operates from a number of different locations, including the Arecibo radio telescope. It is capable of monitoring over 20 million narrowband channels at once, over a 2Ghz range of frequencies.

Project SERENDIP: The “Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations” is a project focused on analysing microwave band transmissions. It is a parasitic search program, analysing data collected by other astronomers during their own projects using the telescope that SERENDIP is attached to. The most recent SERENDIP spectrometer, SERENDIP V.v, is currently attached to the Arecibo telescope, and is capable of monitoring 128 million-channels over a 200MHz range.

Benefits Of SETI
SETI has long been criticised by it’s detractors that it is a waste of money, (A criticism that resulted in the withdrawal of public funding from SETI projects, since the 1990’s SETI has relied almost exclusively on private funding.) and that attempts to communicate with alien civilisations are a form of pseudoscience. But the truth is that regardless of whether or not we ever detect signals from an alien civilisation, SETI is nevertheless at the cutting edge of development in radio astronomy, information theory and computer science, not to mention SETI@home[LINK], originally an experiment in distributed computing, which now uses over 2 million personal computers around the world to analyse SETI data, and is essentially the cheapest, fastest supercomputer in the world. Distributed computing is now used in many fields including the analysis of protein folding (Folding@home[LINK], which could eventually lead to the development of cures for diseases related to protein mis-folding, including Alzheimer’s and Parkinson’s.

CETI
Standing for “Communication with Extraterrestrial Intelligence”, CETI is the branch of SETI that aims not to intercept signals from alien civilisations, but to develop and send messages ourselves that might be understood by extraterrestrial beings. This includes the development of languages with which to construct these messages.

CETI Messages: A number of messages of varying type have been sent to date from radio transmissions to physics objects onboard probes.
 * The Pioneer Plaques: A pair of gold-anodized aluminium on board the Pioneer 10 and Pioneer 11 spacecraft. They display in pictorial form, the male and female human body, the position of the sun in relation to the galactic centre and 14 pulsars, the hydrogen transition which gives rise to 21cm radiation, a schematic of the solar system and an outline of the probe itself.
 * The Voyager Golden Record]: Two gold-plated copper phonograph records, containing a variety of natural sounds, spoken greeting in a wide array of languages, selections of music and a printed message from the then president of the United States Jimmy Carter.
 * The Arecibo Message: A onetime frequency modulated radio transmission, the Arecibo message consisted of 1679 binary digits and contained the numbers one through 10, the atomic numbers of the elements that comprise DNA, as well as formulae for the sugars and bases in DNA nucleotides, and a graphic representation of the spiral structure of DNA itself, a representation of a human, with average height, the population of earth, a representation of the solar system and a graphic, with dimensions of the Arecibo dish used to transmit the message.
 * Cosmic Call 1 & 2: A pair of radio messages sent in 1999 and 2003 respectively, containing the BIG, or Bilingual Image Glossary, a collection of images that help to build a up an understanding of numbers and mathematical operations, a copy of the Arecibo message, ass well as numerous other components including text, audio and video submitted by the public. Each of the Cosmic Call messages were transmitted to a number of star systems from the Evpatoria Planetary Radar.
 * Teen Age Message: A three part message sent from the Yevpatoria Space Centre in 2001, the TAM contained a specially tuned radio signal to make the overall message easier to detect, a collection of musical compositions performed on the Theremin, and the a final part containing a more familiar series of digital information, greetings in Russian and English, and an image glossary.

Despite being among the most famous transmissions ostensibly made to contact alien life none of the above messages are ever likely to be found by any civilisation. Neither the Voyager or Pioneer missions were aimed at any star system in particular and will likely drift into deep space, and the Arecibo message was less a serious attempt at communication, and more a tech demonstration of the newly refurbished Arecibo radio telescope. The message was aimed directly at the M13 globular cluster, an environment that, as mentioned earlier, is almost certainly incapable of evolving life of any kind, or even stable planets. This is not to mention the fact that in the 25,000 years it would take the message to reach M13, the cluster will have drifted out the way, meaning the signal is, and always was headed for deep space.

Where to Aim
One of the biggest problems with attempting to intercept signals from or transmit signals to potential alien civilisations is knowing where to point the equipment. Limitations inherent in radio and laser technology, as well as in terms of power costs prevent a uniformly strong signal from being broadcast across the entire sky, equally as much as it is impossible to monitor the entire sky at once, across all frequencies, for an incoming signal. Thus, when allocating funds or equipment to a project it is of paramount importance to choose a viable target. When choosing a target star to monitor or transmit too, the ideal scenario is a main sequence star, of similar age to the sun in the arms of the Milky Way. Such stars are rich in metals and CHON elements, which appear to be essential to the formation of planetary bodies, and the evolution of life. Planets around very young main sequence stars are unlikely to have had time to evolve life, while very old main sequence stars will have entered the red giant stage, drastically changing the habitable zone of a solar system and most likely destroying any moderately advanced life that might have evolved there. Other targets to rule out include stars in the central regions of the galaxy where intense radiation from supernovae as well as the extremely compact nature of this area would likely prevent life-bearing terrestrial planets from forming, and globular clusters outside of the galactic disk. These systems consist of very old stars containing few metals, which are unlikely to be able to form terrestrial planets, let alone evolve complex life. The intense gravitational anomalies that would occur with close-nit groups of large stars would also make it extremely difficult for a stable planetary system of any kind to form, as close passes to other stars would disrupt the system. In the future, as our technology improves, it will become possible to not only observe earth like planets orbiting distant stars, but also to obtain spectra of them using interferometers such as the proposed Terrestrial Planet Finder. Analysing such information, it would be possible to see the chemical composition of any atmosphere a planet might have. Planets whose atmospheres contain volatiles such as Oxygen (Which would ordinarily react quickly with other elements and form compounds.) would almost certainly harbour life, as without life to replenish the supply, volatile elements would quickly disappear. Finding such a planet would provide one of the most viable targets for attempts to communicate with an alien civilisation.

The Fermi Paradox
If current trends in technology hold, there is no physical limitation on an intelligent civilisation developing technology capable of interstellar travel at sub-light speed, (Between 1% and 10% of c.) and with such technology, it would take a civilisation between 800,000 to 8 million years to colonize the entire galaxy. This is but a fraction of the total age of the Milky Way, and as such, we must ask that of it takes such a relatively short amount of time for an ITC to spread across the entire galaxy, why haven’t we encountered them yet? This paradox, posed by Enrico Fermi in 1950, has a number of possible resolutions, two of which, the Zoo Hypothesis and the Quarantine Hypothesis, have serious ramifications for human attempts to communicate with aliens. The Zoo Hypothesis states that alien civilisations exist, and have simply chosen not to make themselves known to us, deliberately not responding to signals sent from earth, and concealing their own communications. They are observing us, but not interrelating. The Quarantine Hypothesis is essentially the same, but states that the reason for this non-interaction is that mankind has been identified as an aggressive and dangerous species, and as such other more advanced civilisations are avoiding contact with us. Both of these scenarios pose a problem for SETI, as they imply that there may well be advanced alien civilisations all over the galaxy, but no matter how hard we look, and how many times we send messages, we will be unable to communicate with them. The other, more obvious solution to the Fermi Paradox is that there are no alien civilisations even capable of communicating with us in the galaxy at this time. Either there is life in the galaxy, but none of it is advanced enough to engage in interstellar communication, advanced life has developed one or more times in the milky way but has died out from war or some great natural disaster such as an asteroid or most depressingly, the possibility of a planet developing advanced life is so vanishingly small, that earth represents the only life, past or present anywhere in the galaxy.

Methods Of Communication
Radio:

Radio waves are a form of long wavelength electromagnetic radiation, capable of travelling extremely long distances and being generated with relatively low cost in terms of power. Signals can be embedded in these waves and used to transmit information. The major problem with radio waves is that their intensity over distance is subject to a inverse square law, that is to say as the distance a radio wave travels doubles, it’s strength falls to a quarter of its original intensity. As an example a signal sent from earth and measured both as it passes Mars, and as it passes Proxima Centauri, our nearest star, it would be 1/1000th and 1/1000000th of its original strength respectively. It becomes clear then, that over interstellar distances, radio waves will become extremely weak, but this can be overcome by using parabolic antennae to receive radio waves, as many SETI experiments attempt to do. Providing a signal is coherent, which deliberate communications would be, a parabolic antennae will focus the important part of a signal, amplifying it to a point where it can be detected, whereas the random noise that would otherwise make the signal impossible to detect will cancel itself out, as the cosmic background radiation that pervades the universe in homogenous in all directions. Assuming alien civilisations have also developed this relatively basic technology, radio messages we have beamed into space will be detectable by them, and they would assume the same of us.

Laser:

OSETI (Optical SETI) is a subset of SETI which scans the universe for laser communications in the optical and infra-red spectrum. Two main types of communication are searched for, steady beams of light, and pulsed beacons.

While obviously no continuously run earth based laser would be able to outshine a star in terms of total flux at any distance, lasers are characterised by emitting light at a single discreet wavelength, and by tuning a laser to a wavelength that the sun is weak in, such as further into the infrared, it is possible to generate a laser that is brighter than a star in a particular wavelength. To visualise this, imagine we point a telescope at a distant sun-like star, around which is orbiting a planet which is transmitting a continuous beacon of laser light at an infra-red wavelength. Observing this system, we would see a single point of light, as a terrestrial earth sized planet would be impossible to resolve from its star at any interstellar distance with current optical telescopes. By analysing the light from the star at thousands or millions of individual wavelengths, we would be able to build up a spectrum. An ordinary sun-like star would peak in the optical range, and then trail off, but close analysis of the infra-red end of the spectrum would reveal a single peak in one infra-red wavelength. A single wavelength peak in a stars spectrum would be almost irrefutable evidence of an artificial signal, and we would have detected a communication from an alien civilisation. We would expect any comparably advanced alien civilisation to be able to do the same to detect a signal from us.
 * Continuous Beacons: Stars shine incredibly bright, and appear to the naked eye to be of one basic colour, for example a star would appear blue or white to an observer on earth viewing the star in the optical. In reality, the light from a star is an approximate black body spectrum, emitting light in a continuous spectrum; the colour we see is simply the peak wavelength that the star emits at.

Such a signal would be collected with a photon detector or photomultiplier, capable of counting the number of photons detected by a telescope in very small time intervals, and thus are capable of detected pulsed laser light.
 * Pulsed Beacons: Pulsed beacons adopt a different technique to be noticed. Lasers can be turned on and off with incredible speed, even down to emitting pulses of light that last only billionths of a second. By focusing all of the power of a laser into these brief flashes, and considering the fact that lasers can be focused very accurately on a relatively small area over a great distance, a series of pulses can be generated that are capable of outshining an entire star when viewed over interstellar distances. By tuning these lasers, as with the continuous beacon, to a particular wavelength and spacing the pulses by a fixed period of time, a very obviously artificial signal can be generated, one that either we, or aliens would recognize as being generated by an ITC.

Optical Vs. Radio/Microwave SETI: Both laser beacons and radio methods have their pros and cons when considering how to transmit or detect an interstellar communication depending on the parameters of the project; Microwave signals (UHF radio.) can be generated relatively cheaply, and can travel long distances without suffering from the extinction that effects optical transmissions. They can also be used to cover a large portion of sky, or focused into a tighter beam if so desired. The major downside of microwave transmissions is on the receiving end, as very complex signal processing equipment, huge radio telescopes and powerful computing capabilities are required to detect and analyse such signals. Optical transmissions, by contrast require nothing more than a slightly modified optical telescope, two or more photon detectors and a spectrometer to detect, with nowhere near as much computing power required to analyse, and if someone wishing to transmit a laser signal has a single target system, then a highly focused, easily detectable signal can be generated. They do however, cost far more in terms of power required to run, and cannot be transmitted to a large area of sky at once. It is possible of course that advanced alien civilisations would have a developed a cheap, renewable source of power, in which case a major barrier to widespread use of lasers for transmitting is removed.

Constructing an Interstellar Message
When constructing a message to be sent into space, several points must be considered, most importantly, what sort of transmission will be used, and how will the signal be modulated to contain the data, what information will the message contain, and how will the information be expressed, such that an extra-terrestrial might understand it?

Encoding The Message:

While the pros and cons of optical and radio signals have already been discussed, once a method of transmission has been chosen there are a number of ways that the signal being sent can be modulated to embed actual data into it. The easiest way to do this is to vary the signal between two discreet states, allowing information to be embedded in the signal using binary code, a series of 0’s and 1’s. Three main methods for encoding radio waves with data are amplitude modulation, frequency shift keying and phase shift keying. Amplitude modulation works by varying the power of signal between two levels, with for example a higher level meaning 1, and a lower level meaning 0. Amplitude modulated signal are useless for interstellar communication, as they are especially prone to interference. Background noise can cause the 0’s and 1’s to be misinterpreted easily. Frequency shift keying works by using different frequencies to encode binary, a higher frequency for 1, and a lower frequency for 0. FSK is better than AM as the signal can be transmitted at a uniform power, meaning someone receiving such a signal can extract data regardless of noise or other interference affecting the signals intensity. FSK has a major flaw however. An observer will see the signal as two separate signals because of the different frequencies, turning on and off repeatedly. This makes the signal more difficult to different from background noise, and so may be ignored completely. Because of the problems inherent in using AM and FSK over interstellar distances, phase shift keying is preferable. PSK works by transmitting a continuously varying signal that appears like a sine wave and reversing the phase to signify a 1 where a normal oscillation would signify a 0. (That is to say, a peak followed by a trough, as normal would signify 00, whereas two peaks in a row would signify 01.) [Picture of phase shift keying] This method is an excellent way of transmitting information across interstellar distances as it allows information to be embedded in a single pure signal that does not vary in intensity. It would appear to an observer to be a strong, obviously artificial signal, and the data would be revealed when analysed more closely. If the transmitting civilisation chooses to use a pulse or continuous beacon to transmit their message, data can be encoded using wavelength modulation, polarisation or pulse timing. Wavelength modulation is fairly straightforward, and relies on using one or two lasers to emit light in two discreet wavelengths, each corresponding to a binary digit. This method is analogous to using frequency modulation with a radio signal. Polarisation works by exploiting an interesting property of light, namely that individual photons can “vibrate” in different axes. (Up and down/left and right.) By using specialised filters, photons of one polarity can be blocked and the other allowed through, by switching between these filters, or using two lasers each with a different filter on and pulsing them, a continuous signal can be generated in which the polarity is used to encode binary into the signal, by switching between the two states. An observer with two receivers and knowledge of polarity can easily decipher the signal. Finally, when using a pulsed beacon, the time interval between pulses can be varied slightly (By only a few 10th of a second.) to behave in a similar manner to Morse code, in this case for example, a short pulse could represent a 0 while a long pulse could represent a 1. Obviously, this technique cannot be used with a continuous beacon. When using a pulsed beacon, all three of these techniques can be layered on top of each other. This allows someone transmitting a signal to send either a very large quantity of information with each pulse by using each method to encode a different piece of information.

Composing the Message:

Obviously a major component of a transmission to an alien civilisation is its content, the information to be sent, and how it is written. Binary code embedded in signals can be used to transmit a huge range of data, simple streams of numbers can be used to build up bitmap images, and even encode colour and shade into them, allowing simple images to be sent. In this way, languages that should be decipherable by alien civilisations can be developed, using pictograms, and mathematical concepts that any civilisation capable of receiving such a signal would necessarily understand in some form. As a simple example, for an alien civilisation who may have a different number of fingers, or none at all, it is extremely unlikely that they would count in base 10, so the number 3.14, however it is expressed, would be meaningless. But using a picture, expressing the concept of pi would be easy, and from something that simple, an alien civilisation could extrapolate the way our civilisation uses numbers. Languages specifically developed to be used in interstellar communication such as LINCOS could be used to convey much more complex ideas, including abstract concepts such as emotion, (Assuming of course the aliens in question have analogous behaviours.) and interaction between individuals. There are of course a great many things that could be sent in a message to an alien civilisation, but the question to ask is what would we be interested to hear from aliens should they contact us, leading to concepts such as human history and evolution, relationships between species on planet earth and the specifics of our planet such as geography and the local value of g. This information would give aliens a good initial insight into our species. All of this assumes a lot, such as that alien species will communicate using sounds or light in a way that we could comprehend, it may well be that a conversation between two civilisation would consist of a mutual affirmation of our mathematical knowledge, with nothing more complex even being possible. And of course, a truly major problem with conversing with an alien species is that with our nearest star, Proxima Centauri lying at 4.2 light years distance, this is the absolute shortest time between messages possible with an alien civilisation. Having received a message from a more distant alien civilisation and sent a reply, there is every chance the species in question no longer even exists, or has suffered some upheaval that prevents it from responding or receiving another message.

Summary
To conclude, the technology to receive a message from or transmit a message to an idealized Intelligent Technological Civilization is very much available, and improving constantly, but the fact is that huge number of assumptions are made in the search for extraterrestrial life. That aliens will communicate using recognizable radio or laser signals, that should contact be made, any kind of meaningful communication would be possible, that other life would be adapted to live on earth-like planets and not that least, that there is anyone out there at all. Nevertheless, SETI and its contemporaries represent an important frontier of technological development for humanity, and maintain a wonderful sense of hope that we are not alone in the universe.

Images
Upload and place Arecebo Telescope: http://4.bp.blogspot.com/-kWymEYnSfaw/Tae8iQ9bGBI/AAAAAAAAAOk/Xl2LTCUwoHY/s1600/arecibo_observatory.jpg

Arecebo Message: http://uploads.neatorama.com/wp-content/uploads/2009/09/Arecibo-message.png

Voyager Plaque: http://www.notreespace.free.fr/plaque_voyager.jpg

TPF: http://www2.astro.psu.edu/users/niel/astro1/slideshows/class44/025-tpf_380.jpg

Hopefully won't be anything like this: http://idiotflashback.files.wordpress.com/2010/03/alien23.jpg

Interstellar Messages (REFERENCE): http://www.matessa.org/~mike/messages.html