How SETI@Home Screens ET Candidates

SETI@Home volunteers have found 4.2 billion signals of interest since the project began in 1999. What happens to them?

SETI@Home is a distributed computing initiative that analyses radio signals for signs of extra terrestrial intelligence. It relies on volunteers who use their own computers to download and crunch data from the Arecibo Radio telescope in Puerto Rico using bespoke software available from the SETI@Home website.

The project’s central challenge is to spot a real ET signal against a background of noise and interference. The software searches for five different types of patterns that are unlikely to be produced by noise, things like three power spikes in a row and pulses that could represent digital signals.

Using these criteria, SETI@Home volunteers have identified some 4.2 billion signals of potential interest. That’s a significant number. But even though these signals have all been screened by the SETI@Home software, most, if not all, of them are likely to be the result of noise or interference.

So today, Eric Korpela at UC Berkeley and a few buddies outline how they analyse these candidates. One important task is to identify common sources of interference that produce intelligent-like signals. “By far, the most common source of interference in the SETI@home data set is radar stations on the island of Puerto Rico,” say Korpela and co.

Most of these and other types of interference can be identified and removed automatically. However the team is hoping to crowdsource the analysis of the signals that slip through using software that trains volunteers to inspect signals visually and identify those that are the result of interference.

One important criteria for ET signals is that they must be persistent in time and frequency. In other words, an interesting signal must be observable in the same area of sky at a later date. To monitor this, Korpela and co and have designed a program called the Near-Time Persistency Checker or NTPCkr that creates a kind of heat map of interesting signals in the sky.

When an interesting candidate turns up, a certain area of sky becomes ‘hot’. If the signal continues, that area of sky remains hot, otherwise it cools down over time. Anything that remains hot over a decent period of time is worth looking at in more detail.

So what has SETI@Home found? Nothing really. The most significant candidate is a sourse called Radio source SHGb02+14a which the team revealed in 2004. But even this is an unconvincing candidate. In the area of sky in which it was found, there are no stars within 1000 light years of Earth and most commentators think the signal is probably due to random variation.

Nevertheless, the search continues.

Ref: Candidate Identification and Interference Removal in SETI@home

Life in the Universe by Stephen Hawking

In this talk, I would like to speculate a little, on the development of life in the universe, and in particular, the development of intelligent life. I shall take this to include the human race, even though much of its behaviour through out history, has been pretty stupid, and not calculated to aid the survival of the species. Two questions I shall discuss are, ‘What is the probability of life existing else where in the universe?’ and, ‘How may life develop in the future?’

It is a matter of common experience, that things get more disordered and chaotic with time. This observation can be elevated to the status of a law, the so-called Second Law of Thermodynamics. This says that the total amount of disorder, or entropy, in the universe, always increases with time. However, the Law refers only to the total amount of disorder. The order in one body can increase, provided that the amount of disorder in its surroundings increases by a greater amount. This is what happens in a living being. One can define Life to be an ordered system that can sustain itself against the tendency to disorder, and can reproduce itself. That is, it can make similar, but independent, ordered systems. To do these things, the system must convert energy in some ordered form, like food, sunlight, or electric power, into disordered energy, in the form of heat. A laptopIn this way, the system can satisfy the requirement that the total amount of disorder increases, while, at the same time, increasing the order in itself and its offspring. A living being usually has two elements: a set of instructions that tell the system how to sustain and reproduce itself, and a mechanism to carry out the instructions. In biology, these two parts are called genes and metabolism. But it is worth emphasising that there need be nothing biological about them. For example, a computer virus is a program that will make copies of itself in the memory of a computer, and will transfer itself to other computers. Thus it fits the definition of a living system, that I have given. Like a biological virus, it is a rather degenerate form, because it contains only instructions or genes, and doesn’t have any metabolism of its own. Instead, it reprograms the metabolism of the host computer, or cell. Some people have questioned whether viruses should count as life, because they are parasites, and can not exist independently of their hosts. But then most forms of life, ourselves included, are parasites, in that they feed off and depend for their survival on other forms of life. I think computer viruses should count as life. Maybe it says something about human nature, that the only form of life we have created so far is purely destructive. Talk about creating life in our own image. I shall return to electronic forms of life later on…… Continue reading Life in the Universe by Stephen Hawking

Status of the UC-Berkeley SETI Efforts

Distribution of Astropulse candidates on the sky. The dots are the potential sources. Contours are LAB HI survey logarithmic contours. The dashed horizontal lines represent the limits of Arecibo’s viewing range.

We summarize radio and optical SETI programs based at the University of California, Berkeley. The SEVENDIP optical pulse search looks for ns time scale pulses at visible wavelengths using an automated 30 inch telescope. The ongoing SERENDIP V.v sky survey searches for radio signals at the 300 meter Arecibo Observatory. The currently installed configuration supports 128 million channels over a 200 MHz bandwidth with ~1.6 Hz spectral resolution. SETI@home uses the desktop computers of volunteers to analyze over 160 TB of data at taken at Arecibo looking for two types of continuous wave signals and two types of pulsed signals. A version to be released this summer adds autocorrelation analysis to look for complex wave forms that have been repeated (and overlayed) after a short delay. SETI@home will soon be processing data of Kepler exoplanet systems collected at the GBT. The Astropulse project is the first SETI search for $\mu$s time scale dispersed pulses in the radio spectrum. We recently reobserved 114 sky locations where microsecond pulses were detected. This data is in process of being transferred to Berkeley for analysis….
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Search for ET: The high-profile supporters

The resumption of operations at California’s Search for Extraterrestrial Intelligence Institute (SETI) was made possible by donations from celebrity supporters including Jodie Foster.

Jodie Foster - Contact

Following an appeal on the website of the Allen Telescope Array project, named after its first financial backer, Microsoft co-founder Paul Allen, donations from more than 2,200 supporters – known as SETIStars – meant the institute easily reached its $200,000 initial fund-raising goal.
Miss Foster has made several films about alien life, including Contact in 1997, about an SETI astronomer who makes radio contact with extraterrestrials. She is due to star as the head of an alien planet in District 9 director Neill Blomkamp’s latest blockbuster Elysium, which is planned for release in 2013.
She has also indicated that she plans to direct a science fiction film once her current commitments have ended.
In a post on the SETIStar website, Miss Foster said she was supporting it because “we need to return it to the task of searching newly discovered planetary worlds for signs of extraterrestrial intelligence”.
“In Carl Sagan’s book/movie Contact, a radio signal from a distant star system ends humanity’s cosmic isolation and changes our world,” she said.
“The Allen Telescope Array could turn science fiction into science fact, but only if it is actively searching the skies. I support the effort to bring the array out of hibernation.”
Another SETIStar is Larry Niven, the science fiction writer who penned books including the multi award-winning Ringworld, The Magic Goes Away and The Draco Tavern.
“Finding intelligent tool users would reset all parameters. All of human history would look like a preface,” he said on the SETIStars website.
Astronomers and astronauts are also supporting the project, including former Apollo 8 crewman Bill Anders, who said on the website that it would be “absolutely irresponsible” not to search for evidence of extraterrestrial life.