What if aliens exist

It's something Forgan and his colleagues are already working on. The International Academy of Astronautics SETI Permanent Committee created a post-detection protocol in that was slightly updated in ; a new update is starting soon and should be finished in a few years, Forgan said.

For the most part, scientists assume alien contact would happen through a signal purposely sent toward Earth. In this era of news leaks, he said that situation is very unlikely to hold. So, scientists try instead to stick to a protocol that includes informing the public. The IAA protocol is only two pages and covers facets such as searching for a signal, handling evidence and what to do in the case of a confirmed detection. If the evidence gets out to the public while the scientists are still analyzing the signal, Forgan said they could manage the public's expectations by using something called the Rio Scale.

It's essentially a numeric value that represents the degree of likelihood that an alien contact is "real. If the aliens did arrive here, "first contact" protocols likely would be useless, because if they're smart enough to show up physically, they could probably do anything else they like, according to Shostak. I have no idea what they are here for. But there's little need to worry. An " Independence Day " scenario of aliens blowing up important national buildings such as the White House is extremely unlikely, Forgan said, because interstellar travel is difficult.

This feeds into something called the Drake Equation , which considers where the aliens could be and helps show why we haven't heard anything from them yet. To find a signal, first we have to be listening for it. SETI "listening" is going on all over the world, and in fact, this has been happening for many decades. The first modern SETI experiment took place in He scanned at a frequency astronomers nickname "the water hole," which is close to the frequency of light that's given off by hydrogen and hydroxyl one hydrogen atom bonded to one oxygen atom.

The Aug. In terms of the foreseeable technological developments on the earth, the cost per photon and the amount of absorption of radiation by interstellar gas and dust, radio waves seem to be the most efficient and economical method of interstellar communication.

Interstellar space vehicles cannot be excluded a priori, but in all cases they would be a slower, more expensive and more difficult means of communication. Since we have achieved the capability for interstellar radio communication only in the past few decades, there is virtually no chance that any civilization we come in contact with will be as backward as we are.

There also seems to be no possibility of dialogue except between very long-lived and patient civilizations. In view of these circumstances, which should be common to and deducible by all the civilizations in our galaxy, it seems to us quite possible that one-way radio messages are being beamed at the earth at this moment by radio transmitters on planets in orbit around other stars.

To intercept such signals we must guess or deduce the frequency at which the signal is being sent, the width of the frequency band, the type of modulation and the star transmitting the message. Although the correct guesses are not easy to make, they are not as hard as they might seem. Most of the astronomical radio spectrum is quite noisy. There are contributions from interstellar matter, from the three-degree-Kelvin background radiation left over from the early history of the universe, from noise that is fundamentally associated with the operation of any detector and from the absorption of radiation by the earth's atmosphere.

This last source of noise can be avoided by placing a radio telescope in space. The other sources we must live with and so must any other civilization.. There is, however, a pronounced minimum in the radio-noise spectrum. Lying at the minimum or near it are several natural frequencies that should be discernible by all scientifically advanced societies. They are the resonant frequencies emitted by the more abundant molecules and free radicals m interstellar space.

Perhaps the most obvious of these resonances is the frequency of 1, megahertz millions of cycles per second. That frequency is emitted when the spinning electron in an atom of hydrogen spontaneously flips over so that its direction of spin is opposite to that of the proton comprising the nucleus of the hydrogen atom. The frequency of the spin-flip transition of hydrogen at 1, megahertz was first suggested as a channel for interstellar communication in by Philip Morrison and Giuseppe Cocconi.

Such a channel may be too noisy for communication precisely because hydrogen, the most abundant interstellar gas, absorbs and emits radiation at that frequency. The number of other plausible and available communication channels is not large, so that determining the right one should not be too difficult. We cannot use a similar logic to guess the bandwidth that might be used in interstellar communication. The narrower the bandwidth is, the farther a signal can be transmitted before it becomes too weak for detection..

On the other hand, the narrower the bandwidth is, the less information the signal can carry. A compromise is therefore required between the desire to send a signal the maximum distance and the desire to communicate the maximum amount of information. Perhaps simple signals with narrow bandwidths are sent to enhance the probability of the signals' being received. Perhaps information-rich signals with broad bandwidths are sent in order to achieve rapid and extensive communication. The broad-bandwidth signals would be intended for those enlightened civilizations that have in vested major resources in large receiving systems.

When we actually search for signals it is not necessary to guess the exact bandwidth, only to guess the minimum bandwidth. It is possible to communicate on many adjacent narrow bands al once. Each such channel can be studies individually, and the data from several adjacent channels can be combined to yield the equivalent of a wider channel without any loss of information or sensitivity.

The procedure is relatively easy with the aid of a computer; it is in fact routinely employed in studies of pulsars. In any event we should observe the maximum number of channels because of the possibility that the transmitting civilization is not broadcasting on one of the "natural" frequencies such as 1, megahertz. We do not, of course, know now which star we should listen to. The most conservative approach is to turn our receivers to stars that are rather similar to the sun, beginning with the nearest.

Two nearby stars, Epsilon Eridani and Tau Ceti, both about 12 light-years away, were the candidates for Project Ozma, the first search with a radio telescope for extraterrestrial intelligence, conducted by one of us Drake in Project Ozma, named after the ruler of Oz in L. Frank Baum's children's stories, was "on the air" for four weeks at 1, megahertz. The results were negative. Since then there have been a number of other studies. In spite of some false alarms to the contrary, none has seen successful.

The lack of success is lot unexpected. If there are a million technical civilizations m a galaxy of some billion stars, we must turn our receivers to , stars before we have a fair statistical chance of detecting a single extraterrestrial message. So or we have listened to only a few more than stars. In other words, we have mounted only. Our present technology is entirely adequate for both transmitting and receiving messages across immense interstellar distances.

For example, if the ,foot radio telescope at the Arecibo observatory in Puerto Rico were to transmit information at the rate of one it binary digit per second with a bandwidth of one hertz, the signal could be received by an identical radio telescope anywhere in the galaxy.

By the same token, the Arecibo telescope could detect a similar signal transmitted from a distance hundreds of times greater than our estimate of light-years to the nearest extraterrestrial civilization.. A search of hundreds of thousands of stars in the hope of detecting one message would require remarkable dedication and would probably take several decades.

It seems unlikely that any existing major radio telescope would be given over to such an intensive program to the exclusion of its usual work. The construction of one radio telescope or more that would be devoted perhaps half-time to the search seems to be the only practical method of seeking out extraterrestrial intelligence in a serious way.

The cost would be some tens of millions of dollars. So far we have been discussing the reception of messages that a civilization would intentionally transmit to the earth. An alternative possibility is that we might try to "eavesdrop" on the radio traffic an extraterrestrial civilization employs for its own purposes.

Such radio traffic could be readily apparent On the earth, for example, a new radar system employed with the telescope at the Arecibo Observatory for planetary studies emits a narrow-bandwidth signal that, if it were detected from another star, would be between a million and 10 billion times brighter than the sun at the same frequency.

In addition, because of radio and television transmission, the earth is extremely bright at wavelengths of about a meter.

If the planets of other civilizations have a radio brightness comparable to the earth's from television transmission alone, they should be detectable. Because of the complexity of the signals and the fact that they are not beamed specifically at the earth, however, the receiver we would need in order to eavesdrop would have to be much more elaborate and sensitive than any radio-telescope system we now possess.

One such system has been devised in a preliminary way by Bernard M. The system, known as Cyclops, would consist of an enormous radio telescope connected to a complex computer system. The computer system would be designed particularly to search through the data from the telescope for signals bearing the mark of intelligence, to combine numerous adjacent channels in order to construct signals of various effective bandwidths and to present the results of the automatic analyses for all conceivable forms of interstellar radio communication in a way that would be intelligible to the project scientists.

To construct a radio telescope of enormous aperture as a single antenna would be prohibitively expensive. The Cyclops system would instead capitalize on our ability to connect many individual antennas to act in unison. The Very Large Array consists of 27 antennas, each 82 feet in diameter, arranged in a Y-shaped pattern whose three arms are each 10 miles long. The Cyclops system would be much larger. Its current design calls for 1, antennas each meters in diameter, all electronically connected to one another and to the computer system.

The array would be as compact as possible but would cover perhaps 25 square miles. The effective signal-collecting area of the system would be hundreds of times the area of any existing radio telescope, and it would be capable of detecting even relatively weak signals such as television transmissions from civilizations several hundred light-years away.

Moreover, it would be the instrument par excellence for receiving signals specifically directed at the earth. One of the greatest virtues of the Cyclops system is that no technological advances would be required m order to build it.

The necessary electronic and computer techniques re already well developed. We would need only to build a vast number of items we already build well. The Cyclops system not only would have enormous power for searching for extraterrestrial intelligence but also would be In extraordinary tool for radar studies If the bodies in the solar system, for traditional radio astronomy outside the solar system and for the tracking of pace vehicles to distances beyond the each of present receivers.

For example, researchers have looked at worlds that were not in the CHZ of their stars, had no surface oceans of liquid water, and yet were possible homes for life and even advanced civilizations. Considerations like these have led scientists to take a much broader view of the conditions necessary for the appearance of life. The type of star around which a planet revolves can have important consequences for the development of life, even for planets in a CHZ.

Small, dim stars, for example, which are called red dwarfs and make up the largest fraction of stars in the Milky Way, often go through periods of extreme activity.

Stellar flares and ejections of massive amounts of charged particles would make life on any planetary surface very difficult, whether the planet was in the CHZ or not. In such situations, the CHZ simply becomes irrelevant. Scientists are beginning to abandon the idea that life has to evolve and persist on the surface of planets. Many current arguments, for example, conclude that any living organisms on Mars will be found beneath the surface.

In addition, if life exists in subsurface oceans in the outer solar system, such as in the oceans of Europa and Enceladus, it will be, by definition, beneath the surface. Even on Earth, it appears that there may be a greater biomass beneath the planetary surface than on it. Thus, the intense radiation environment associated with small stars need not preclude the development of life, even though that life would probably be impossible to detect directly with our current technology.

More massive stars, on the other hand, provide a more benign radiation environment, but they can have relatively short lifetimes. In some cases, they may live for as little as 30 million years. It is unlikely that anything except simple microbial life could evolve on a planet in such a short amount of time. In addition, such stars end their life in a massive explosion called a supernova, which would surely destroy any nearby planets.

Thus, even if life did manage to develop in the CHZ of such a star, all trace of it would be wiped out when the star died. It is because of these constraints that exoplanet hunters have concentrated their attention on planets in the CHZ of medium-sized stars like the Sun.

The second source of complexity in the discussion of habitability arises because planetary atmospheres are not stable, unchanging systems but evolve over time. Regardless of the temperature, however, there will always be some molecules that are moving faster than the average and some that are moving slower. The bigger the planet, the stronger its gravitational force and the easier it is to retain the atmosphere.

It is important to note that it is harder to boost heavy molecules to high velocity than it is to boost light ones. This means that lighter molecules are more likely than heavy ones to be lost to gravitational escape. Earth, for example, has lost a large amount of its original hydrogen and helium—the lightest members of its atmosphere—while Mars has lost even heavier gases such as oxygen and nitrogen.

A related loss mechanism called photodissociation is particularly important for water molecules. If there is water on the surface of a planet, there will be some water vapor in the atmosphere. The resulting hydrogen, being light, will be lost through gravitational escape, and the oxygen will combine with atoms on the surface to create various oxidized minerals. Every time a volcano goes off on Earth, carbon dioxide is released from deep within the mantle and pumped into the atmosphere.

Thus, the general geological processes on a planet can affect the amount of carbon dioxide in its atmosphere, and this, in turn, will influence its temperature. Thus, Venus had no way of removing carbon dioxide from its atmosphere, and, lacking a deep carbon cycle, the planet suffered a buildup of that gas in what is known as a runaway greenhouse effect.