
From The Pennsylvania State University
Via

“EarthSky”
11.3.22
Macy Huston
Jason Wright

Advanced civilizations might be expected to produce “technology pollution” in the form of chemicals, light and heat. This technology should be detectable across the vast distances of space, astronomers say. Image via Jay Freidlander/NASA.
“If an alien were to look at Earth, our human technology – from cell towers to fluorescent light bulbs – could be a beacon signifying the presence of life.
We are two astronomers who work on the search for extraterrestrial intelligence, or SETI. In our research, we try to characterize and detect signs of technology – or technosignatures – originating from beyond Earth. Scanning the sky for a TV broadcast of some extraterrestrial Olympics may sound straightforward. But searching for signs of distant, advanced civilizations is a much more nuanced and difficult task than it might seem.
Saying ‘hello’ with technology like radios and lasers

A laser – like the one seen here – or beam of radio waves pointed intentionally at Earth would be a strong sign of extraterrestrial life. Image via G. Hüdepohl/ The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)
The modern scientific search for extraterrestrial intelligence began in 1959 when astronomers Giuseppe Cocconi and Philip Morrison showed that radio telescopes at interstellar distances could detect radio transmissions from Earth. The same year, Frank Drake launched the first SETI search, Project Ozma, by pointing a large radio telescope at two nearby sun-like stars.
He was checking to see if he could detect any radio signals coming from them. Following the invention of the laser in 1960, astronomers detected visible light from distant planets.
These were the first foundational attempts to detect radio or laser signals.
They were looking for alien technology or powerful signals that another civilization intentionally sent to the solar system, meaning for them to be found.
Given the technological limitations of the 1960s, astronomers did not give serious thought to searching for broadcast signals – like television and radio broadcasts on Earth – that would leak into space. But a beam of a radio signal, with all its power focused toward Earth, could be detectable from much farther away. Just picture the difference between a laser and a weak light bulb.
SETI looks for radio and laser signals
The search for intentional radio and laser signals is still one of the most popular SETI strategies today. However, this approach assumes that extraterrestrial civilizations want to communicate with other technologically advanced life. Humans very rarely send targeted signals into space. And some scholars argue that intelligent species may purposefully avoid broadcasting their locations. The SETI Paradox is the search for signals that no one may be sending.

This artist’s impression shows the Square Kilometer Array, a telescope array under construction in both Australia and Africa. This array will be sensitive enough to detect the equivalent of radio broadcasts from distant planets. Image via SPDO/ TDP/ DRAO/ Swinburne Astronomy Productions.
Leaking radio waves
Humans don’t transmit many intentional signals out to the cosmos. But many technologies people use today produce a lot of radio transmissions that leak into space. Some of these signals would be detectable if they came from a nearby star.
The worldwide network of television towers constantly emits signals in many directions that leak into space. And they can accumulate into a detectable [Science (below)], though relatively faint, radio signal. Research is ongoing as to whether current emissions from cell towers in the radio frequency on Earth would be detectable using today’s telescopes. But the upcoming Square Kilometer Array radio telescope will be able to detect even fainter radio signals.


It will have 50 times the sensitivity of current radio telescope arrays.
Not all human-made signals are so unfocused, though. Astronomers and space agencies use beams of radio waves to communicate with satellites and spacecraft in the solar system. Some researchers also use radio waves for radar to study asteroids. These radio signals are more focused and pointed out into space. Any extraterrestrial civilization in the line of sight of these beams could likely detect these unambiguously artificial signals.
Finding megastructures
Aside from finding an actual alien spacecraft, radio waves are the most common technosignatures featured in sci-fi movies and books. But they are not the only signals that could be out there.
In 1960, astronomer Freeman Dyson theorized that, since stars are by far the most powerful energy source in any planetary system, a technologically advanced civilization might collect a significant portion of the star’s light as energy with what would essentially be a massive solar panel. Many astronomers call these megastructures, and there are a few ways to detect them.
After using the energy in the captured light, the technology of an advanced society would re-emit some of the energy as heat. Astronomers have shown that this heat could be detectable as extra infrared radiation coming from a star system.
Another possible way to find a megastructure would be to measure its dimming effect on a star. Specifically, large artificial satellites orbiting a star would periodically block some of its light. This would appear as dips in the star’s apparent brightness over time. Astronomers could detect this effect similarly to how scientists discover distant planets today.
A whole lot of technology pollution
Another technosignature that astronomers have thought about is pollution.
On Earth, chemical pollutants – like nitrogen dioxide and chlorofluorocarbons – are almost exclusively the product of human industry. It is possible to detect these molecules in the atmospheres of exoplanets with the same method the James Webb Space Telescope is using to search distant planets for signs of biology. If astronomers find a planet with an atmosphere filled with chemicals only produced by technology, it may be a sign of life.
Finally, scientists could also detect artificial light or heat from cities and industry with large optical and infrared telescopes. They could also detect a large number of satellites orbiting a planet. But a civilization would need to produce far more heat, light and satellites than Earth does to be detectable across the vastness of space using technology humans currently possess.
Which technology signal is best?
No astronomer has ever found a confirmed technosignature, so it’s hard to say what will be the first sign of alien civilizations. While many astronomers have thought a lot about what might make for a good signal, ultimately, nobody knows what extraterrestrial technology might look like and what signals are out there in the universe.
Some astronomers support a generalized SETI approach which searches for anything in space that current scientific knowledge cannot naturally explain. Some, like us, continue to search for both intentional and unintentional technosignatures. The bottom line is that there are many avenues for detecting distant life. Since no one knows what approach is likely to succeed first, there is still a lot of exciting work left to do.”
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Breakthrough Listen Project


UC Observatories Lick Automated Planet Finder fully robotic 2.4-meter optical telescope at Lick Observatory, situated on the summit of Mount Hamilton, east of San Jose, California


Green Bank Radio Telescope, West Virginia, now the center piece of the Green Bank Observatory, being cut loose by the National Science Foundation, supported by Breakthrough Listen Project, West Virginia University, and operated by the nonprofit Associated Universities, Inc.
CSIRO-Commonwealth Scientific and Industrial Research Organisation (AU) Parkes Observatory [ Murriyang, the traditional Indigenous name] , located 20 kilometres north of the town of Parkes, New South Wales, Australia, 414.80m above sea level.
SKA SARAO Meerkat telescope(SA) 90 km outside the small Northern Cape town of Carnarvon, SA.
Newly added
University of Arizona Veritas Four Čerenkov telescopes A novel gamma ray telescope under construction at the CfA Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, altitude 2,606 m 8,550 ft. A large project known as the Čerenkov Telescope Array, composed of hundreds of similar telescopes to be situated at Roque de los Muchachos Observatory [Instituto de Astrofísica de Canarias ](ES) in the Canary Islands and Chile at European Southern Observatory Cerro Paranal(EU) site. The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev. ___________________________________________________________________
Science paper:
Science 1978
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The The Pennsylvania State University is a public state-related land-grant research university with campuses and facilities throughout Pennsylvania. Founded in 1855 as the Farmers’ High School of Pennsylvania, Penn State became the state’s only land-grant university in 1863. Today, Penn State is a major research university which conducts teaching, research, and public service. Its instructional mission includes undergraduate, graduate, professional and continuing education offered through resident instruction and online delivery. In addition to its land-grant designation, it also participates in the sea-grant, space-grant, and sun-grant research consortia; it is one of only four such universities (along with Cornell University, Oregon State University, and University of Hawaiʻi at Mānoa). Its University Park campus, which is the largest and serves as the administrative hub, lies within the Borough of State College and College Township. It has two law schools: Penn State Law, on the school’s University Park campus, and Dickinson Law, in Carlisle. The College of Medicine is in Hershey. Penn State is one university that is geographically distributed throughout Pennsylvania. There are 19 commonwealth campuses and 5 special mission campuses located across the state. The University Park campus has been labeled one of the “Public Ivies,” a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.
The Pennsylvania State University is a member of The Association of American Universities an organization of American research universities devoted to maintaining a strong system of academic research and education.
Annual enrollment at the University Park campus totals more than 46,800 graduate and undergraduate students, making it one of the largest universities in the United States. It has the world’s largest dues-paying alumni association. The university offers more than 160 majors among all its campuses.
Annually, the university hosts the Penn State IFC/Panhellenic Dance Marathon (THON), which is the world’s largest student-run philanthropy. This event is held at the Bryce Jordan Center on the University Park campus. The university’s athletics teams compete in Division I of the NCAA and are collectively known as the Penn State Nittany Lions, competing in the Big Ten Conference for most sports. Penn State students, alumni, faculty and coaches have received a total of 54 Olympic medals.
Early years
The school was sponsored by the Pennsylvania State Agricultural Society and founded as a degree-granting institution on February 22, 1855, by Pennsylvania’s state legislature as the Farmers’ High School of Pennsylvania. The use of “college” or “university” was avoided because of local prejudice against such institutions as being impractical in their courses of study. Centre County, Pennsylvania, became the home of the new school when James Irvin of Bellefonte, Pennsylvania, donated 200 acres (0.8 km2) of land – the first of 10,101 acres (41 km^2) the school would eventually acquire. In 1862, the school’s name was changed to the Agricultural College of Pennsylvania, and with the passage of the Morrill Land-Grant Acts, Pennsylvania selected the school in 1863 to be the state’s sole land-grant college. The school’s name changed to the Pennsylvania State College in 1874; enrollment fell to 64 undergraduates the following year as the school tried to balance purely agricultural studies with a more classic education.
George W. Atherton became president of the school in 1882, and broadened the curriculum. Shortly after he introduced engineering studies, Penn State became one of the ten largest engineering schools in the nation. Atherton also expanded the liberal arts and agriculture programs, for which the school began receiving regular appropriations from the state in 1887. A major road in State College has been named in Atherton’s honor. Additionally, Penn State’s Atherton Hall, a well-furnished and centrally located residence hall, is named not after George Atherton himself, but after his wife, Frances Washburn Atherton. His grave is in front of Schwab Auditorium near Old Main, marked by an engraved marble block in front of his statue.
Early 20th century
In the years that followed, Penn State grew significantly, becoming the state’s largest grantor of baccalaureate degrees and reaching an enrollment of 5,000 in 1936. Around that time, a system of commonwealth campuses was started by President Ralph Dorn Hetzel to provide an alternative for Depression-era students who were economically unable to leave home to attend college.
In 1953, President Milton S. Eisenhower, brother of then-U.S. President Dwight D. Eisenhower, sought and won permission to elevate the school to university status as The Pennsylvania State University. Under his successor Eric A. Walker (1956–1970), the university acquired hundreds of acres of surrounding land, and enrollment nearly tripled. In addition, in 1967, the Penn State Milton S. Hershey Medical Center, a college of medicine and hospital, was established in Hershey with a $50 million gift from the Hershey Trust Company.
Modern era
In the 1970s, the university became a state-related institution. As such, it now belongs to the Commonwealth System of Higher Education. In 1975, the lyrics in Penn State’s alma mater song were revised to be gender-neutral in honor of International Women’s Year; the revised lyrics were taken from the posthumously-published autobiography of the writer of the original lyrics, Fred Lewis Pattee, and Professor Patricia Farrell acted as a spokesperson for those who wanted the change.
In 1989, the Pennsylvania College of Technology in Williamsport joined ranks with the university, and in 2000, so did the Dickinson School of Law. The university is now the largest in Pennsylvania. To offset the lack of funding due to the limited growth in state appropriations to Penn State, the university has concentrated its efforts on philanthropy.
Research
Penn State is classified among “R1: Doctoral Universities – Very high research activity”. Over 10,000 students are enrolled in the university’s graduate school (including the law and medical schools), and over 70,000 degrees have been awarded since the school was founded in 1922.
Penn State’s research and development expenditure has been on the rise in recent years. For fiscal year 2013, according to institutional rankings of total research expenditures for science and engineering released by the National Science Foundation , Penn State stood second in the nation, behind only Johns Hopkins University and tied with the Massachusetts Institute of Technology , in the number of fields in which it is ranked in the top ten. Overall, Penn State ranked 17th nationally in total research expenditures across the board. In 12 individual fields, however, the university achieved rankings in the top ten nationally. The fields and sub-fields in which Penn State ranked in the top ten are materials (1st), psychology (2nd), mechanical engineering (3rd), sociology (3rd), electrical engineering (4th), total engineering (5th), aerospace engineering (8th), computer science (8th), agricultural sciences (8th), civil engineering (9th), atmospheric sciences (9th), and earth sciences (9th). Moreover, in eleven of these fields, the university has repeated top-ten status every year since at least 2008. For fiscal year 2011, the National Science Foundation reported that Penn State had spent $794.846 million on R&D and ranked 15th among U.S. universities and colleges in R&D spending.
For the 2008–2009 fiscal year, Penn State was ranked ninth among U.S. universities by the National Science Foundation, with $753 million in research and development spending for science and engineering. During the 2015–2016 fiscal year, Penn State received $836 million in research expenditures.
The Applied Research Lab (ARL), located near the University Park campus, has been a research partner with the Department of Defense since 1945 and conducts research primarily in support of the United States Navy. It is the largest component of Penn State’s research efforts statewide, with over 1,000 researchers and other staff members.
The Materials Research Institute was created to coordinate the highly diverse and growing materials activities across Penn State’s University Park campus. With more than 200 faculty in 15 departments, 4 colleges, and 2 Department of Defense research laboratories, MRI was designed to break down the academic walls that traditionally divide disciplines and enable faculty to collaborate across departmental and even college boundaries. MRI has become a model for this interdisciplinary approach to research, both within and outside the university. Dr. Richard E. Tressler was an international leader in the development of high-temperature materials. He pioneered high-temperature fiber testing and use, advanced instrumentation and test methodologies for thermostructural materials, and design and performance verification of ceramics and composites in high-temperature aerospace, industrial, and energy applications. He was founding director of the Center for Advanced Materials (CAM), which supported many faculty and students from the College of Earth and Mineral Science, the Eberly College of Science, the College of Engineering, the Materials Research Laboratory and the Applied Research Laboratories at Penn State on high-temperature materials. His vision for Interdisciplinary research played a key role in creating the Materials Research Institute, and the establishment of Penn State as an acknowledged leader among major universities in materials education and research.
The university was one of the founding members of the Worldwide Universities Network (WUN), a partnership that includes 17 research-led universities in the United States, Asia, and Europe. The network provides funding, facilitates collaboration between universities, and coordinates exchanges of faculty members and graduate students among institutions. Former Penn State president Graham Spanier is a former vice-chair of the WUN.
The Pennsylvania State University Libraries were ranked 14th among research libraries in North America in the 2003–2004 survey released by The Chronicle of Higher Education. The university’s library system began with a 1,500-book library in Old Main. In 2009, its holdings had grown to 5.2 million volumes, in addition to 500,000 maps, five million microforms, and 180,000 films and videos.
The university’s College of Information Sciences and Technology is the home of CiteSeerX, an open-access repository and search engine for scholarly publications. The university is also the host to the Radiation Science & Engineering Center, which houses the oldest operating university research reactor. Additionally, University Park houses the Graduate Program in Acoustics, the only freestanding acoustics program in the United States. The university also houses the Center for Medieval Studies, a program that was founded to research and study the European Middle Ages, and the Center for the Study of Higher Education (CSHE), one of the first centers established to research postsecondary education.
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