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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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40,000 UC workers gird for a strike, disrupting medical services, cafeterias at all campuses

The University of California is bracing for a massive strike Thursday that would disrupt services at all campuses, hospitals and medical centers as more than 40,000 workers — patient transport staff, nursing aides, custodians, campus dining hall employees — are prepared to walk out if an agreement is not reached.
The threatened strike could halt or delay scores of medical appointments, although hospitals and medical offices will remain open, and it would limit campus dining operations. UC campuses and hospitals are making contingency plans and communicating with patients, students, faculty and staff about potential disruptions.
Late Thursday afternoon, the American Federation of State, County and Municipal Employees Local 3299 remained deep in contract negotiations and had not reached an agreement with UC. The union is poised to launch an open-ended strike that its leaders say would not end until its demands are met for better wages, lower healthcare costs and opening talks with UC over how the university can help alleviate ballooning housing costs.
UC has said it has offered to increase salaries, give contract ratification bonuses and cap some healthcare premium increases. When the union announced the strike nearly a month ago, a UC spokesperson said the university was “disappointed” by the decision “despite the significant progress made at the bargaining table.”
The union said picket lines and rallies would begin 8 a.m. Thursday at every UC campus and medical center, including Ronald Reagan UCLA Medical Center. The threatened strike would culminate more than two years of contract negotiations after several one- and multi-day strikes
What jobs do AFSCME members hold?
AFSCME’s members include custodians, gardeners, dining hall food service workers, transportation workers and skilled craft workers such as plumbers and electricians. At UC hospitals, union members work in cafeterias, as radiology technologists, nurse’s aides and patient transporters, among other roles.
UCLA Health and the David Geffen School of Medicine were “developing plans to minimize disruptions to campus and clinical operations,” and all UCLA Health hospitals and clinics “will remain open and operational,” officials said in a Monday announcement.
The message did not specify whether procedures, surgeries or imaging will be rescheduled, or detail how work including custodial services would be carried out.
At UC Santa Cruz, Interim Campus Provost Paul Koch said in a campus statement the strike would have “noticeable impacts” on health services, transportation and dining, with dining halls operating under “minimized staffing” and the Student Health Center having “reduced appointments and services.”
When the union staged a two-day strike in November, multiple UCLA dining halls closed, some offered only takeout service amid long student lines, and students turned to food trucks for meals.
Union demands
The union is asking for higher wages, lower healthcare costs and the right to bargain over housing assistance. Leaders says some members are sleeping in their cars to be close to work, falling behind on rent or commuting hours because they cannot afford housing near campuses, particularly in Los Angeles and the Bay Area.
In a Monday update on bargaining posted to its website, UC said it had offered a “further sweetened” deal to give members up to 34% in pay increases over a three-year contract. The proposal offered a $2,000 ratification bonus and caps on HMO premium increases that UC said could save members up to $3,000 each year on healthcare costs.
“We know employees are looking for certainty, stability and meaningful economic support, and UC remains committed to reaching an agreement that puts additional money in employees’ pockets and provides long-term support to address affordability,” Missy Matella, UC’s associate vice president for systemwide labor and employee relations, wrote in a statement.
The union contends UC is misrepresenting who would receive the raises and by how much, arguing the examples are not representative of a membership with an average salary of $62,000. It says that rising healthcare costs would erode any wage gains. It also says UC has not responded to its requests to open up discussions on how to help members struggling with housing.
The wage increase “doesn’t apply to a third of the members,” said AFSCME 3299 spokesman Todd Stenhouse. Stenhouse said UC’s offers would leave members “falling behind.”
“In real wages, they are making 10% less than they were 10 years ago. So you’ve got people that are already living on a razor’s edge making less,” Stenhouse said, citing inflation and healthcare costs among other areas.
The threatened walkouts come after the union filed two labor practice complaints with the state’s Public Employment Relations Board.
One accuses UC of refusing to bargain over its housing demand, arguing workers “should not be living out of their cars” while UC offers “low-interest mortgages and cash for down payments to its much more affluent senior executives and faculty.”
The second accuses UC of imposing “unilateral changes to the terms and conditions of employment,” including a July action automatically raising employees to $25 per hour or granting a 5% wage increase — whichever was higher — after the university issued its “last, best and final offer.”
The union said the rollout was done “in a scattershot manner,” with hundreds either not receiving the raises or waiting months, and alleged UC also imposed new healthcare rates without bargaining.
The labor board has not determined whether UC engaged in wrongdoing.
‘Going on … strike is a sacrifice’
Union members said the strike is a last resort.
“I deserve long-term stability. Not short-term tricks and ploys,” Rosalba Montoya, a medical assistant at UCLA, said in recent statement posted on the union’s social media. “Going on an open-ended strike is a sacrifice, but it’s one that will pay off in the end.”
At a recent UC Board of Regents meeting at UCLA, another AFSCME member told the board: “You guys keep offering us crumbs. I don’t have a home of my own. I’m one emergency away from being on the streets and yet you tell us that there’s no money, no solution, no real effort to address the housing crisis, or provide livable wage.”
The union has also received supportive messages from several elected officials.
U.S. Sen. Adam Schiff, in a video this month on AFSCME 3299’s X account, urged UC to “bargain in good faith.”
In another social media video addressed to union members, Assemblymember Cecilia Aguiar-Curry said she hoped UC would reach a deal that “honors the work you do and the patients you look after every day.”
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Silicon Valley’s A.I. Lobbying Blitz Reaches a Fever Pitch
OpenAI and Anthropic are opening offices in Washington, hiring lobbyists and spending more than ever to win over federal lawmakers.
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Were Martian Tides Strong Enough to Shape its Ancient Landscape?
You’re an anaerobic microbe sunbathing on a Martian beach billions of years ago listening to the small waves hit the shoreline as you take in the perchlorates in the Martian regolith. This is because while Mars is warm and wet, it still lacks sufficient oxygen, so anaerobic life like yourself doesn’t need oxygen to survive. You’re chilling for several hours and eventually notice the water hasn’t touched you. You remember over-hearing some otherworldly fellows who briefly landed and discussed the landscape didn’t look well formed, so they left.
Anaerobic microbes may or may not have existed on Mars billions of years ago (the “otherworldly fellows” might have, though), but scientists have strong evidence that flowing liquid water existed on the surface of ancient Mars. However, there’s been a longstanding debate regarding whether tides helped shape the landscape in Gale Crater and Utopia Planitia, which have been explored by NASA’s Curiosity Rover and China’s Zhurong Rover, respectively. The findings were recently published in the Journal of Geophysical Research: Planets and could provide key insights into how tides played a role in landscape formation on ancient Mars billions of years ago. While Gale Crater is hypothesized to have been a lake on ancient Mars, Utopia Planitia is hypothesized to have been a vast ocean during that time.
For the study, the researchers used a series of computer models to simulate the speed and movement of tides on ancient Mars to ascertain if they could be responsible for depositing sedimentary rocks previously observed by the aforementioned rovers. This is because tides on Earth are responsible for sustaining life and climate regulation through driving ocean currents, resulting in circulating vital nutrients and mixing oxygen in deep ocean waters.
In the end, and after incorporating the one-third gravity of Mars, the researchers found that the maximum tide speed at both rover locations, which are located on vastly different locations on the Red Planet, was calculated to be approximately 0.01 meters per second (0.03 feet per second). For context, the tide speeds on Earth vary on location. For example, the open ocean is estimated to have tides as fast as 0.05 meters per second (0.16 feet per second), whereas coastlines can experience tidal speeds between 0.5-1.0 meters per second (1.64-3.28 feet per second).
The study notes, “Our research suggests that tides should rarely be considered a primary factor when analyzing sedimentary structures on Mars in the future. They may be considered a secondary driver of sediment suspension and transport, but the sediment transport capacity of Martian tides was too small across most of the ocean and coastal areas for it to be considered a primary driver of sediment transport. However, there are uncertainties that should be considered when interpreting these results, especially around the size of an ancient Martian ocean.”
Tides on Earth are possible from the gravitational influence between the Earth and the Moon, as both are tidally locked, which is why the Moon always has one side facing the Earth. This ultimately comes down to the Moon being a large enough companion to exert this gravitational tug-of-war being approximately one-quarter the diameter of the Earth. In contrast, while Mars has two moons, Phobos and Deimos, they are both far too small to exert any significant gravitational influence on Mars. Phobos is approximately 300 times smaller than Mars with Deimos being even smaller. Therefore, Mars relies on what’s known as solar tides, which is when the Sun’s gravitational influence is exerted on a planetary body. Solar tides are experienced on Earth when the Earth, Moon, and Sun are aligned (spring tides), or when the Moon is at a 90-degree angle relative to the Earth and Sun (neap tides).
What new insight into tides on ancient Mars will researchers make in the coming years and decades?
As always, keep doing science & keep looking up!
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