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A Brief-ish History of SETI. Part IV: Arecibo and the WOW! Signal
Welcome back to a Brief-ish History of SETI! In our previous installments, we examined the earliest attempts to find extraterrestrial intelligence (ETI) beyond Earth, as well as one of the most important philosophical underpinnings (Fermi’s Paradox). We also looked at the first true example of the Search for Extraterrestrial Intelligence (SETI) experiment (Project Ozma) and the Drake Equation, followed by the first proposed searches for megastructures (Dyson Spheres) and classification schemes for ETIs (the Kardashev Scale).
Today, we’ll examine the first attempt at “active SETI,” aka. Messaging Extraterrestrial Intelligence (METI), and what remains the best candidate for a possible message of extraterrestrial origin. These are none other than the Arecibo Message, and the WOW! Signal, two pivotal moments in the history of SETI that remain unrivaled to this day. Buckle up, because some big concepts and big names (one of whom was the focus of Part II) are about to be dropped!
The Arecibo Message
In 1960, famed Cornell Professor Frank Drake spearheaded Project Ozma (the first modern SETI experiment) using the radio telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia. For six hours a day, between April and July of 1960, Drake and his colleagues listened to Tau Ceti and Epsilon Eridani – two nearby Sun-like stars – for radio signals in the frequency range of cold neutral hydrogen gas in interstellar space (1420 Hz or near 21 cm). Although the project failed to detect anything beyond radio static, it paved the way for future SETI and METI efforts.
Construction on the National Astronomy and Ionosphere Center (NAIC) – aka. the Arecibo Observatory – lasted from the mid-1950s until the early 60s. Originally, this massive radio telescope was dual-purpose, designed to study Earth’s ionosphere and to detect incoming ballistic missiles as they traveled through the upper atmosphere. When it became operational in 1963, Prof. Drake was the Director of the NAIC and oversaw its conversion into an astronomical observatory dedicated to radio astronomy.
In the early 1970s, Frank Drake organized the first campaign to use Arecibo’s megawatt transmitter, attached to its 305-meter (1000-foot) antenna, to send a message to space. Rather than an invitation to open communications between Earth and an ETI, the message was a technology demonstration intended to convey humanity’s abilities, scientific knowledge, and our location in the galaxy. In essence, it was a way of saying “Hello there” and “This is who and where we are” to any advanced species capable of receiving it.
The message was composed by Drake with the assistance of Sagan and other prominent astronomers and consisted of a 1679-binary-digit picture (210 bytes), the product of two prime numbers, arranged in a rectangular grid of 73 lines, each with 23 characters (also prime numbers). The use of prime numbers was deliberate since it would likely make the message easier for an alien civilization to decode. The message conveyed a series of scientific, geographical, biological, and astronomical information in different colors. These included:
- A counting scheme of 1 to 10 (white)
- The atomic numbers for hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up DNA (purple)
- The chemical formula of the four purines and pyrimidine bases that make up DNA (green)
- An image of the DNA double helix and an estimate of the number of nucleotides (blue and white, respectively)
- A stick-figure of a human being (red), our average dimensions (blue/white), and the human population of Earth (white)
- A depiction of the Solar System, indicating that the message is coming from the third planet (yellow)
- A schematic of the Arecibo Observatory and its dimensions (purple/white and blue)
This signal was transmitted on November 16th, 1974, at a frequency of 2380 MHz, with an effective bandwidth of 10 Hz, and lasted for less than three minutes. The broadcast lasted less than three minutes and was equivalent to a 20-gigawatt omnidirectional broadcast, meaning that it would be detectable by any radio antenna in the galaxy similar in size to Arecibo. The destination for this message was Messier 13 (NGC 6205 or “The Great Hercules Cluster”), a globular star cluster located about 22,000 light-years from Earth.
This cluster, composed of 300,000 stars across 145 light-years, is estimated to be 11.65 billion years old, making it a good candidate for messaging an extraterrestrial civilization. More than fifty years later, the Arecibo Message is still considered one of the most important milestones in the history of SETI and METI. Like Project Ozma, it coincided with the Space Age, taking place just 2.5 years after the last Apollo mission (Apollo 17) landed on the Moon. In this sense, our exploration of space was mirrored by a similar interest in finding intelligent life elsewhere in the cosmos.
A few years later, another major event took place, making scientists and regular folk alike wonder whether someone out there was trying to message us as well!
WOW!
On August 15th, 1977, radio astronomer Jerry Ehman was reviewing printouts of observational data at the Ohio State University Radio Observatory (OSURO) in Delaware, Ohio – aka. the Big Ear Observatory. Between 1965 and 1971, the observatory conducted the Ohio Sky Survey, an astronomical survey of extragalactic radio sources. With this complete, the facility’s Big Ear Telescope began searching for extraterrestrial radio signals two years later, a search that continued until 1995 (making it the longest SETI experiment in history).
While the mountains of data this search generated were generally nothing more than the background hum of the Universe, Ehman noticed something very different on this day. When searching through endless fields of numbers, he noticed the characters “6EQUJ5,” which indicated a signal of particular intensity. In red pen, Ehman wrote “WOW!” next to it, and the nickname stuck. The entire signal sequence lasted 72 seconds, during which the Big Ear Telescope was able to receive it. Several follow-up observations failed to detect the signal again.
Over fifty years later, the WOW! Signal remains an unexplained one-off event, with now-debunked explanations including radio interference, comets, and space debris. However, in August 2024, the Planetary Habitability Laboratory (PHL) published a paper reporting that the Wow! Signal was likely caused by stellar emissions energizing a cold hydrogen cloud, causing it to suddenly surge in brightness.
A year later, the same team from the PHL published a paper offering updated conclusions on its possible point of origin, peak flux density (250 Janskys instead of 54 and 212), and frequency. The updated frequency, 1420.726 MHz rather than 1420.4556, suggested that the signal came from a galactic source with a substantially higher radial velocity than previously assumed, they claimed. While the updated paper also narrowed the part of the sky the signal could have emanated from, this increased the statistical certainty of its location by two-thirds.
These two events, the first METI signal and the most promising candidate, remain unparalleled in the history of SETI. In addition, they’ve also inspired a great deal of follow-up investigations, surveys, and discussions regarding the ethics of communicating to the cosmos. Tune in for our next installment, where we will look at some more examples of messages intended for other intelligent life forms, as well as other proposed explanations for why we haven’t heard from anybody… yet!
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Surveillance Prices. Hidden Fees. Shifting Costs. This Madness Must Stop.
It’s time to combat commercial surveillance with stronger laws on fair pricing.
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Dry Martian Meteorite Reveals Early Water in Mars’s Crust
Billions of years ago, Mars was hypothesized to have been a habitable world with flowing liquid water and the potential for life. But directly studying its ancient past is currently limited to orbiters and rovers, as scientists have yet to obtain direct samples from Mars. However, meteorites have been found on Earth to have potentially originated from Mars during large impacts that flung chunks of the Red Planet into space, eventually being grabbed by Earth’s gravity and crashing into the Earth’s surface.
Now, an international team of scientists might be one step closer to piecing together Mars’ watery ancient past, and specifically how much water could have flowed across the Red Planet’s surface long ago. In findings recently published in the Geophysical Research Letters, a collaborative team of researchers led by the Technical University of Denmark investigated an intriguing meteorite with an even more intriguing name, “Black Beauty”, with the scientific designation of Northwest Africa 7034 (NWA 7034). What makes Black Beauty so intriguing is its designation as the only known meteorite that originated from the crust of Mars, having been blasted away during an impact billions of years ago, as Black Beauty is estimated to be about 4.4 to 4.5 billion years old.
Using a combination of X-ray and neutron tomography, the researchers analyzed Black Beauty with the goal of ascertaining if the ancient meteorite contained traces of water, also called hydrous materials in the scientific community. While X-ray tomography is used to identify the densest parts of Black Beauty while focusing on iron and silicon, neutron tomography was used to identify that previous “holes” found by normal X-rays were actually hydrous materials.
“Neutrons are particularly sensitive to hydrogen,” said Dr. David Mannes, who is a scientist at the Paul Scherrer Institute (PSI), a co-author on the study. Dr. Mannes collaborated with fellow study co-author, Dr. Anders Kaestner, on the neutron tomography at PSI. “In combination with X-ray tomography, we were not only able to detect tiny hydrated minerals, but also, for the first time, visualize larger, macroscopic hydrogen deposits.”
Essentially, the researchers identified that early Mars contained a water reservoir large enough to engage with the Martian surface and crust, resulting in water deposits into crustal rocks that eventually became Black Beauty. The researchers also note these materials are similar to materials found in Jezero Crater by NASA’s Perseverance rover. Therefore, Black Beauty continues to add a growing pile of evidence that Mars was a much warmer and wetter planet billions of years ago.
While Black Beauty has revealed intricate details regarding ancient Mars and its watery past, arguably the most famous meteorite from Mars is the Allan Hills 84001 (ALH84001) meteorite, which was recovered in Antarctica on December 27, 1984. However, it wasn’t until 1996 before scientists discovered it was potentially from Mars, as ALH84001 had initially been designated as an asteroid chunk, which are frequently discovered on Earth. Once scientists studied ALH84001, they discovered it contained unique structures they hypothesized could indicate signs of ancient Martian life.
While their 1996 study published in Science gained worldwide attention, including an official address from President Bill Clinton, the scientific community was quick to claim these features could have formed from non-biological processes. Regardless of its specific origin, both Black Beauty and ALH84001 demonstrate the importance of bringing back samples from Mars to reduce relying on ancient meteorites.
Unfortunately, the long-anticipated NASA-ESA Mars Sample Return mission was canceled by Congress due to ballooning costs, meaning all the sample tubes that NASA’s Perseverance rover has been depositing on the Martian surface is potentially for nought. For now, scientists have to rely on meteorites to unlock the secrets of ancient Mars, but China’s planned Tianwen-3 might be the first to return Mars samples to Earth sometime next decade.
What new insights into the “Black Beauty” meteorite and ancient Mars will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
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Darth Vader to San Diego City Council: The Emperor liked Flock cameras

In a galaxy not so far, far away — well, in San Diego — the controversial police use of Flock surveillance cameras that photograph and record license plate numbers has at least one prominent supporter.
Darth Vader.
“The Emperor is a fan of Flock,” a person wearing a full-body costume of the “Star Wars” villain told a committee of the San Diego City Council this week, referencing Darth Vader’s evil, power-hungry boss, Emperor Palpatine, ruler of the Galactic Empire.
“And we must continue utilizing Flock technologies so that we can follow and surveil the Rebel scum as they move from playground to playground, from playground to pool, from pool to gymnasium,” the person said during public comments at a Wednesday meeting of the Public Safety and Livable Neighborhoods Committee.
The cosplayer, who breathed heavily into the microphone a la the movie villain, was formally called to the podium by the name Darth Vader.
It was a stance a bit out of sync with silver screen Darth, who famously told an Imperial stooge who got too braggadocious about the Empire’s planet-destroying Death Star: “Don’t be too proud of this technological terror you’ve constructed.”
But in a twist not quite as big as Darth telling Luke Skywalker he was his daddy, the bad guy in black showed up to the government meeting in San Diego to be sarcastic about Flock cameras. He didn’t actually support them at all.
Nor, it turns out, did a lot of people in the audience, who hoisted signs from the American Civil Liberties Union reading: “Get the Flock Out!”
The cosplayer’s sarcastic endorsement comes as Flock Safety — the company whose more than 120,000 artificial intelligence-enabled license plate readers can be found along roadsides in every state but Alaska — comes under increasing scrutiny by lawmakers, civil rights groups and members of the public who have expressed privacy concerns.
Dozens of mostly smaller cities have deactivated their Flock cameras or ended contracts with the company over concerns that it provides data to the Trump administration that can be used to track down immigrants for deportation.
And recent reporting by the Washington Post uncovered at least 50 instances nationwide in which law enforcement officials were accused of misusing their access to the cameras, largely to stalk former romantic partners or citizens.
Last month, the Los Angeles Police Department announced it was pausing its relationship with Flock, but police officials later said they were in the process of negotiating a new deal with the company that would include more data-sharing safeguards.
Both Mayor Karen Bass and her opponent in the November mayoral election, Councilmember Nithya Raman, have said the city should stop working with Flock.
The company, whose automated license readers document plate data as vehicles drive past, says it has partnerships with 5,000 law enforcement agencies nationwide.
Amid public backlash, the company announced this month several platform changes, including a shorter data retention window and audit tools for law enforcement customers intended to flag abnormal search behavior.
In San Diego, Flock cameras are affixed to streetlights in about 500 locations, according to the 2025 Annual Surveillance Report by the San Diego Police Department.
In addition to plate numbers, the report states, the cameras record the date, time and location of the scan, as well as vehicle descriptors such as make, model and color.
The information is encrypted and transmitted to a secure database that can be accessed only by San Diego police personnel, according to the department. The data is saved for 30 days and automatically deleted unless it is being used as evidence in an active investigation, according to the department.
The report says San Diego police officers last year conducted more than 244,000 investigative searches of the data and that it played a “key role in advancing 361 cases.”
The data, per the department, helped officers recover 259 stolen vehicles and find four missing people, as well as aiding the investigations of around nine of the city’s 28 homicides in 2025.
In a presentation to the Public Safety and Livable Neighborhoods Committee in November, San Diego Police Capt. Charles Lara said the technology “has been truly game-changing for our department, especially while we continue to operate with hundreds of officers below ideal staffing levels.”
Lt. Kristopher McAndrew said the “vast majority of data is never viewed” and that the police department does not share data with federal or out-of-state law enforcement agencies or private entities.
At the meeting this week, Darth Vader — who, like everyone else who approached the podium, was allotted two minutes of speaking time — said of the Flock camera system: “I need this so I can stalk my ex-girlfriend.”
He asked the City Council members how residents will continue to trust them when they continue to vote “for surveillance technology that imprisons them.”
He advised one of the council members to work on her Jedi mind tricks to fool them, then raised his hand to the audience, saying: “Do it like this.”
“This technology will help us find the Rebel scum and their hidden base on Hoth,” he said, referencing the ice planet in the “Star Wars” universe. “This technology will help us find Luke Skywalker as he traverses the universe in his X-wing. This technology is a necessary, necessary force.”
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