Why does seti use radio

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This is especially the case for one-off events. One way forward would be to abandon the traditional approach of using large single dishes for SETI. While a parabolic dish has the useful property of being sensitive to a fairly large area of sky, if a candidate signal is detected, there is no way of knowing exactly where it came from. So, while the Parkes telescope was nominally pointing at Proxima Centauri, literally hundreds of thousands of other galactic stars were also present in the field of view.

Ultimately, any one of them could potentially be the source of the BLC We can overcome this problem by observing with several large dishes simultaneously, preferably separated by hundreds and even thousands of kilometres. By combining their signals using a powerful technique known as Very Long Baseline Interferometry , we can pin-point the position of a signal with exquisite accuracy, such as to a single star. For nearby systems such as Proxima Centauri, we can achieve a precision of approximately one thousandth of an astronomical unit the distance between the Sun and Earth.

This should allow us to identify not just the stellar system but the associated planet that transmitted the signal. At lower frequencies our galaxy emits prodigious amounts of radio waves creating a loud background of noise. Hydrogen atoms emit at MHz a wavelength of 21 cm. Hydroxyl molecules, composed of one atom of hydrogen and one atom of oxygen OH , emit at four specific radio frequencies ranging from MHz to MHz.

When a hydrogen atom combines with a hydroxyl molecule it forms a molecule of water, the most essential molecule for life as we know it. Thus, the range of frequencies from to MHz is called the Water Hole. It has been a popular frequency range for many SETI programs. For example, the radio emission from a quasar would span most of the diagram above and the amount of power would change very slowly over the frequency range.

As mentioned above, hydrogen and hydroxyl emit radio waves at particular frequencies. The diagram below shows the power emitted by a cloud of hydroxyl OH molecules near a red giant star. The cloud rotates around the star so some of the molecules are moving toward us and some are moving away.

When she receives a radio message from a distant star, there are profound implications for humanity. SETI is an extremely controversial scientific endeavor. Some scientists believe that it is a complete waste of time and money, while others believe that detection of a signal from ET would forever change our view of the universe. In this article, we will examine the SETI program. We'll look at how radio telescopes work and how they are used for SETI searches, what the probabilities of detecting alien life are, what might happen if or when such a signal is detected and how you can participate in SETI yourself.

The universe is an awfully big place. How can you best search the huge sky for a radio signal from ET? There are three basic dilemmas:. When you're in an unfamiliar area and want to find a station on your car radio, you have to turn the dial until you pick something up, or press the "search" or "scan" button if your radio has these features.

Well, the question is, where might ET broadcast? This is perhaps the biggest challenge for SETI researchers because there are so many frequencies -- "billions and billions," to quote Carl Sagan. The universe is filled with radio noise from naturally occurring phenomena, much like a summer night is filled with the sounds of crickets and other insects. Fortunately, nature does provide a "window" in the radio spectrum where the background noise is low. In the 1- to gigahertz GHz range of frequencies, there is a sharp drop in background noise.

In this region, there are two frequencies that are caused by excited atoms or molecules: 1. Because hydrogen and hydroxyl ions are the components of water, this area has been called the water hole. Many SETI researchers reason that ET would know about this region of frequencies and deliberately broadcast there because of the low noise. So, most SETI search protocols include this area of the spectrum.

Although other "magical" frequencies have been proposed, SETI researchers have not reached a consensus on which of these frequencies to search. Another approach does not limit the search to any one, small range of frequencies, but instead builds large, multichannel-bandwidth signal processors that can scan millions or billions of frequencies simultaneously. Many SETI projects use this approach. The number of radio telescopes in the world is limited, and SETI researchers must compete with other radio astronomers for time on these instruments.

There are three possible solutions to this problem:. Much of SETI research has been done by "renting" time on existing radio telescopes. This is the way it was done in the movie "Contact. Project Phoenix has a tractor-trailer full of signal-analysis equipment that it attaches to the telescope for the search. Project SERENDIP takes advantage of large amounts of telescope time, but its researchers do not have control over which targets are studied and cannot conduct follow-up studies to confirm a possible ET signal.

Located northeast of San Francisco, in the "radio quiet area" of the University of California at Berkeley's Hat Creek Observatory, the array will be dedicated entirely to SETI, using hundreds or perhaps thousands of backyard-type satellite dishes to collect radio signals by interferometry see the section Dishes for the Sky for information on radio telescopes.

If a signal is detected, there are a series of steps that follow to confirm that the signal is extraterrestrial:. Once a signal has been confirmed, there are very specific steps that must be followed in the release of this information see SETI Institute: Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence for details.

The movie "Contact" has a good depiction of the detection of an ET signal and subsequent events. What are the possibilities that we will find ET signals? To address this issue, astronomer Frank Drake introduced an equation to calculate the number of ET civilizations in the galaxy in The equation, now referred to as the Drake Equation , considers astronomical, biological and sociological factors in its estimates:.