Jump to content

SETI@home

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 82.0.173.47 (talk) at 08:52, 22 July 2007 (→‎Scientific research). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

File:SETI@Home Logo.svg
SETI@home logo

SETI@home ("SETI at home") is a distributed computing project using Internet-connected computers, hosted by the Space Sciences Laboratory, at the University of California, Berkeley, in the United States. SETI is an acronym for the Search for Extra-Terrestrial Intelligence. SETI@home was released to the public on May 17, 1999.[1][2][3]

Scientific research

There were two original goals of SETI@home. The first was to prove the viability and practicality of the 'distributed grid computing' concept, and the second was to do useful scientific work by supporting an experiment to detect intelligent life outside Earth.

The first of these goals is generally considered to have succeeded completely. The current BOINC environment, a development of the original SETI, is providing support for several computationally intensive projects in a wide range of disciplines. The remainder of this article deals specifically with the original SETI experiment.

SETI@home searches for possible evidence of radio transmissions from extraterrestrial intelligence using data from the Arecibo radio telescope. The software searches for four signals:[citation needed]

  • Spikes in power spectra
  • Gaussian rises and falls in transmission power, possibly representing the telescope beam's main lobe passing over a radio source
  • Triplets — three power spikes in a row
  • Pulsing signals that possibly represent a narrowband digital-style transmission

There are so many variations on how a signal would arrive at Earth that signals are processed to ensure that each possible way it could arrive might be checked. For instance, another planet is very unlikely to be at the same distance from Earth all the time. The distances across the universe between different galaxies is ever changing, so a variety of speeds must be accommodated - the reason being that a signal will look very different if the broadcasting location is moving towards us or away from us. This is the Doppler effect, the same effect that is observed if an ambulance is going past us at speed - the whole pitch of the siren's sound changes as it goes into the distance. So SETI software checks the signal by taking each individual frequency and analysing it as if it were not moving relative to the Earth, or moving away or towards its at different speeds.

The process is somewhat like tuning a radio to various channels, and looking at the signal strength meter. If the strength of the signal goes up, that gets attention. More technically, it involves a lot of digital signal processing, mostly discrete Fourier transforms at various chirp rates and durations.

Results

While the project has not found any conclusive signs of extraterrestrial intelligence, it has identified several candidate spots for further analysis. The most significant candidate signal to date was announced on September 1, 2004, named Radio source SHGb02+14a.

Seth Shostak (2004), a prominent SETI figure, has stated that he expects to get a conclusive signal and proof of alien contact between 2020 and 2025, based on the Drake equation.

While the project hasn't reached the goal of finding extraterrestrial intelligence, it did prove to the scientific community that distributed computing projects using Internet-connected computers can work and even oust the largest supercomputers[4].

Technology

SETI@home version 4.45

Anybody with an Internet-active computer can participate in SETI@home by running a free program that downloads and analyzes radio telescope data.

Observational Data is recorded on 35 Gigabyte tapes at the Arecibo Observatory in Puerto Rico, each holding 15.5 hours of observations, which are then mailed to Berkeley (Korpela et al. 2001). Arecibo does not have a high bandwidth internet connection, so data must go by postal mail to Berkeley at first. Once there, it is divided in both time and frequency domains work units of 107 seconds of data (SETI@home 2001), or approximately 0.35 MB, which overlap in time but not in frequency (Korpela et al. 2001). These work units then get sent from the SETI@home server over the Internet to people around the world to analyze.

The analysis software can search for signals with about one-tenth the strength of those sought in previous surveys, because it makes use of a computationally intensive algorithm called coherent integration that no one else has had the computing power to implement.

Data is merged into a database using SETI@home computers in Berkeley. Interference is rejected, and various pattern-detection algorithms are applied to search for the most interesting signals.

Software

SETI@home under classic client (version 3.08)

The SETI@home distributed computing software runs either as a screensaver or continuously while a user works, making use of processor power that would otherwise be unused.

The initial software platform, now referred to as "SETI@home Classic", ran from 17 May 1999 to 15 December 2005. This program was only capable of running SETI@home; it was replaced by Berkeley Open Infrastructure for Network Computing (BOINC), which also allows users to contribute to other distributed computing projects at the same time as running SETI@home. The BOINC platform will also allow testing for more types of signals.

The discontinuation of the SETI@home Classic platform has rendered older Macintosh computers running pre-OS X versions of the Mac OS unsuitable for participating in the project.

On 3 May 2006 new work units for a new version of SETI@home called "SETI@home Enhanced" started being distributed. Computers provide the power for even more computationally intensive work than when the project began. This new version is more sensitive by a factor of two with respect to Gaussian signals and to some kinds of pulsed signals than the original SETI@home (BOINC) software. This new application has been optimized to the point where it will run faster on some workunits than earlier versions. However, some workunits (the best workunits, scientifically speaking) will take significantly longer.

Notably, there have also been some distributions of the SETI@home applications that have been optimized for a particular type of CPU. They are referred to as "optimized executables" and have been found to run faster on systems specific for that CPU. As of 2007, most of these applications are optimized for Intel processors (and their corresponding instruction sets). [5]

SETI@home has also been used as a stress testing tool for computer workstations, as it runs the computer CPU at full power for a sustained time period. This is especially useful to overclockers.

The results of the data processing are normally automatically transmitted when the computer is next connected to the internet; it can also be instructed to connect to the internet as needed.

Statistics

With over 5.2 million participants worldwide, the project is the distributed computing project with the most participants to date. Since its launch on May 17, 1999, the project has logged over two million years of aggregate computing time. On September 26, 2001, SETI@home had performed a total of 1021 floating point operations. It is acknowledged by the Guinness World Records as the largest computation in history (Newport 2005). With over 1.36 million computers in the system, as of March 12 2007, SETI@home has the ability to compute over 265 TeraFLOPS [1]. For comparison, Blue Gene (currently the world's fastest supercomputer) computes just over 360 TFLOPS.

Project futures

There are future plans to get data from the Parkes Observatory in Australia to analyse the southern hemisphere.[citation needed]

Competitive aspect

SETI@home users quickly started to compete with one another in an effort to process the maximum number of work units. Teams were formed to combine the efforts of individual users. The competition continued, and grew larger, with the introduction of BOINC.

As with any competition, attempts have been made to 'cheat' the system and claim credit for work that has not been performed. To combat cheats, the SETI@Home system sends every workunit to multiple computers, a value known as "initial replication" (currently 3). Credit is only granted for each returned workunit once a minimum number of results have been returned and the results agree, a value known as "minimum quorum" (currently 2). If, due to computation errors or cheating by submitting false data, not enough results agree, more identical workunits are sent out until the minimum quorum can be reached. The final credit granted to all machines which returned the correct result is the same, and is the lowest of the values claimed by each machine. The claimed credit by each machine for an identical workunit often varies due to very minor differences in floating point arithmetic on different processors.[citation needed]

Some users have installed and run SETI@home on computers at their workplaces — an act known as 'Borging', after the assimilation-driven Borg of Star Trek. In some cases, SETI@home users have misused company resources to gain work-unit results — with at least one individual getting fired for running SETI@home on an enterprise production system (Foreman 2004).

Other users collected large quantities of equipment together at home to create "SETI farms", which typically consist of a number of computers consisting of only a motherboard, CPU, RAM and power supply that are arranged on shelves as diskless workstations running either Linux or old versions of Windows "headless" (without a monitor).

Threats to the project

Like any project of indefinite duration, there are factors that may result in its eventual termination. Some of these are detailed below:

Alternative distributed computing projects

When the project was launched there were few alternative ways of donating computer time to research projects. However, now there are a lot more options, and therefore SETI@home has to compete with other projects. As different people have different value systems, some will (for example) prefer projects with a relatively high chance of benefitting humanity in the short term, while others will avoid these because they are more likely to be associated with commercial profit. Yet there are now nonprofit organizations working for these humanitarian goals, such as the World Community Grid, which likewise has teams and a points system, yet focuses on AIDS treatments and proteome folding.

More restrictive computer use policies in businesses

As of 16 October 2005, approximately one third of the processing for the non-BOINC version of the software was performed on work or school based machines (SETI@home, 2005). As a lot of these computers will give reduced privileges to ordinary users, it is possible that much of this has been done by network administrators themselves. A number of administrators have also expressed concerns about the automatic software updating in BOINC workunits.[citation needed]

To some extent, this may be offset by better connectivity to home machines.

Funding

There is currently no government funding for SETI research, and private funding is always limited. Berkeley Space Science Lab has found ways of working with small budgets and the project has received donations allowing it to go well beyond its original planned duration, but it still has to compete for limited funds with other SETI projects and other space sciences projects.

Unofficial clients

A number of individuals and companies made unofficial changes to the distributed part of the software to try to produce faster results, but this compromised the integrity of all the results (Molnar 2000). As a result, the software had to be updated to make it easier to detect such changes.

BOINC allows unofficial clients and relies more on cross-checking.[2]

Other distributed computing projects

Further information: List of distributed computing projects

Distributed computing is also being used for medical research, such as to searching for AIDS treatments and in protein folding projects. Since the switch to the BOINC platform however, users can divide work between projects, choosing to give only a percentage of CPU time to each.

However, competition exists between BOINC and the World Community Grid, which uses a United Devices client by default. The World Community Grid, like BOINC, enables access to as many projects as the platform supports. World Community Grid is more centralized and easier to manage than BOINC,[citation needed] at the cost of fewer choices. World Community Grid currently also runs a BOINC client.WCG BOINC However there are a few services which allow the user to manage all of his or her projects and computers running BOINC in one place, such as GridRepublic.

See also

References

  • Carrigan, Richard A., Jr. (2003). "The Ultimate Hacker: SETI Signals May Need to Be Decontaminated". Astronomical Society of the Pacfic: 519.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  • Foreman, Liz (2004-10-08). "State Employee Fired For Using State Property To Search For Aliens". Associated Press. {{cite news}}: Check date values in: |date= (help)
  • Korpela, Eric (2001). "SETI@home - Massively Distributed Computing for SETI" (PDF). Computing in Science & Engineering: 78–83. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  • Molnar, David (2000). "The SETI@Home Problem". Retrieved 2006-06-02.
  • Newport, Stuart (editor) (2005). "Largest Computation". Guinness World Records. HCI Entertainment. Retrieved 2005-12-03. {{cite web}}: |author= has generic name (help)
  • Sample, Ian (2005). "Scientists be on guard..." Guinness World Records. The Guardian. Retrieved 2005-11-25.
  • Shostak, Seth (2004-07-22). "First Contact Within 20 Years: Shostak". Space Daily. Retrieved 2006-06-12. {{cite news}}: Check date values in: |date= (help)
  • SETI@home (2001). "The SETI@home Sky Survey". Retrieved 2006-06-02.
  • SETI@home (2005). "SETI@home computer venues". Retrieved 2006-06-12.

Notes

  1. ^ Dr. Tony Phillips (May 23, 1999). "ET, phone SETI@home!". NASA. Retrieved 2006-10-06.
  2. ^ Robert Nemiroff (May 17, 1999). "Astronomy Picture of the Day". Retrieved 2006-10-06. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ "SETI@home Classic: In Memoriam". December 15, 2005. Retrieved 2006-10-06.
  4. ^ http://www.boincstats.com/stats/project_graph.php?pr=bo
  5. ^ http://lunatics.at/index.php?PHPSESSID=d598ad2faca5400a7e3e91801506c233&
Retrieved from "https://en.wikipedia.org/w/index.php?title=SETI@home&oldid=146283157"