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Thread: The WOW! Signal

  1. #11
    Quote Originally Posted by kenf View Post
    Mark makes return being mean. way go dude , hanging with fag boy I see.
    That's proud fag boy.

  2. #12
    Quote Originally Posted by Wise Young View Post
    One of the most fascinating questions is whether there are other SETI signals that are coming in and we are just not recognizing them. After all, if there is one thing that is potentially worse that the plastic garbage we are polluting our earth with, it is the enormous radiofrequency pollution that we have imposed on the universe. Can you imagine some other world out there being bombarded by "Desperate Housewives" or Rush Limbaugh? If I were an alien, I would steer many light years clear of this solar system.
    I've heard that this idea of aliens picking up our radio and tv signals is something of a myth. Apparently, various natural phenomenon cause the signals to deteriorate quite rapidly, so by the time they ever reached an exoplanet they'd be little more than static.
    "I'm lost. I'm no guide, but I'm by your side." - Pearl Jam

    "It decomposes, mendicant, therefore, truly, one calls this the world." -- Loka Sutta

  3. #13
    Quote Originally Posted by Saorsa View Post
    I've heard that this idea of aliens picking up our radio and tv signals is something of a myth. Apparently, various natural phenomenon cause the signals to deteriorate quite rapidly, so by the time they ever reached an exoplanet they'd be little more than static.
    I've read this as well. An alien intelligence would have to have some very advanced technology to pick up the weak signals and identify them as being from an intelligent source. And it's quite unlikely they'd be able to reconstruct the signal into meaningful information. Of course this assumes that they would even care about other civilizations!

  4. #14
    Quote Originally Posted by Saorsa View Post
    I've heard that this idea of aliens picking up our radio and tv signals is something of a myth. Apparently, various natural phenomenon cause the signals to deteriorate quite rapidly, so by the time they ever reached an exoplanet they'd be little more than static.

    While that may be true for a lot of the radiofrequency emissions from earth, we should remember that we are able to communicate with satellites that we have sent to Mars, Venus, and even Pluto. Not only can the satellites detect that signals that we are sending but we can detect the return signals that they are sending.

    Would these signals reach the stars? It is true that the intensity of signals fall by the inverse square relationship, whether one is using light or radiowaves. Thus, the signal intensity will diminish to very low levels quite rapidly.

    This relationship can be illustrated by the diagram below, which shows the apparent brightness of a source with luminosity L0 at distances r, 2r, 3r, etc. Notice that as the distance increases, the light must spread out over a larger surface and the surface brightness decreases in accordance with a "one over r squared" relationship. The decrease goes as r squared because the area over which the light is spread is proportional to the distance squared.
    On the other hand, a coherent beam that does not spread should retain its intensity over quite long distances. Of course, laser beams can be used to carry information. A significant part of the SETI project is to search for laser-like information carriers

    While most SETI sky searches have studied the radio spectrum, some SETI researchers have considered the possibility that alien civilizations might be using powerful lasers for interstellar communications at optical wavelengths. The idea was first suggested by R. N. Schwartz and Charles Hard Townes in a 1961 paper published in the journal Nature titled "Interstellar and Interplanetary Communication by Optical Masers". In 1983, Townes, one of the inventors of the laser, published a detailed study of the idea in the US journal Proceedings of the National Academy of Sciences. Most SETI researchers agreed with the idea.

    The 1971 Cyclops study discounted the possibility of optical SETI, reasoning that construction of a laser system that could outshine the bright central sun of a remote star system would be too difficult.

    Some SETI advocates, such as Frank Drake, have suggested that such a judgment was too conservative; early 21st century humans have no means of knowing how a superior technology is communicating or would communicate, and negative results may simply mean humans are making the wrong searches.[citation needed]

    There are two problems with optical SETI. The first problem is that lasers are highly "monochromatic", that is, they emit light only on one frequency, making it troublesome to figure out what frequency to look for.

    However, according to the uncertainty principle, emitting light in narrow pulses results in a broad spectrum of emission; the spread in frequency becomes higher as the pulse width becomes narrower, making it easier to detect an emission.

    The other problem is that while radio transmissions can be broadcast in all directions, lasers are highly directional. This means that a laser beam could be easily blocked by clouds of interstellar dust, and Earth would have to cross its direct line of fire by chance to receive it.
    Optical SETI supporters have conducted paper studies[14] of the effectiveness of using contemporary high-energy lasers and a ten-meter focus mirror as an interstellar beacon. The analysis shows that an infrared pulse from a laser, focused into a narrow beam by such a mirror, would appear thousands of times brighter than the Sun to a distant civilization in the beam's line of fire. The Cyclops study proved incorrect in suggesting a laser beam would be inherently hard to see.

    Such a system could be made to automatically steer itself through a target list, sending a pulse to each target at a constant rate. This would allow targeting of all Sun-like stars within a distance of 100 light-years. The studies have also described an automatic laser pulse detector system with a low-cost, two-meter mirror made of carbon composite materials, focusing on an array of light detectors. This automatic detector system could perform sky surveys to detect laser flashes from civilizations attempting contact.

    In the 1980s, two Soviet researchers conducted a short optical SETI search, but turned up nothing. During much of the 1990s, the optical SETI cause was kept alive through searches by Stuart Kingsley, a dedicated British amateur living in the US state of Ohio.

    Several optical SETI experiments are now in progress. A Harvard-Smithsonian group that includes Paul Horowitz designed a laser detector and mounted it on Harvard's 155 centimeter (61 inch) optical telescope. This telescope is currently being used for a more conventional star survey, and the optical SETI survey is "piggybacking" on that effort. Between October 1998 and November 1999, the survey inspected about 2,500 stars. Nothing that resembled an intentional laser signal was detected, but efforts continue. The Harvard-Smithsonian group is now working with Princeton University to mount a similar detector system on Princeton's 91-centimeter (36-inch) telescope. The Harvard and Princeton telescopes will be "ganged" to track the same targets at the same time, with the intent being to detect the same signal in both locations as a means of reducing errors from detector noise.

    The Harvard-Smithsonian group is now building a dedicated all-sky optical survey system along the lines of that described above, featuring a 1.8-meter (72-inch) telescope. The new optical SETI survey telescope is being set up at the Oak Ridge Observatory in Harvard, Massachusetts.
    The University of California, Berkeley, home of SERENDIP and SETI@home, is also conducting optical SETI searches. One is being directed by Geoffrey Marcy, an extrasolar planet hunter, and involves examination of records of spectra taken during extrasolar planet hunts for a continuous, rather than pulsed, laser signal. The other Berkeley optical SETI effort is more like that being pursued by the Harvard-Smithsonian group and is being directed by Dan Werthimer of Berkeley, who built the laser detector for the Harvard-Smithsonian group. The Berkeley survey uses a 76-centimeter (30-inch) automated telescope and an older laser detector built by Werthimer.

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