For thousands of years, humans have looked up at the night sky and wondered, “are we alone?”
For the longest time, it remained nothing more than a philosophical question, but in the 20th century, some researchers thought it was time to finally start looking.
One of the big questions was how do you look for something that you don’t know exists, and if it does, you don’t know where it is?
Learn more about SETI, the Search for Extraterrestrial Intelligence, on this episode of Everything Everywhere Daily.
The idea that there might be other intelligent life forms in the universe is actually a pretty old one. We have writings from philosophers going back at least 2000 years who have pondered the idea.
The Greek thinker Democritus in the late 5th century BC pondered the idea of a plurality of worlds.
Saint Augustine referenced Epicurious and his idea that there may be many worlds “throughout the boundless immensity of space”.
The Islamic scholar Muhammad al-Baqir wrote in the early 8th century, “Maybe you see that God created only this single world and that God did not create humans besides you. Well, I swear by God that God created thousands and thousands of worlds and thousands and thousands of humankind.”
When the telescope was invented, it allowed astronomers to see some of the worlds beyond our own, and it only added credibility to the idea that there might be someone else out there.
Many notable intellectuals considered, if not advocated, the idea of worlds beyond our own, including Johannes Kepler, Benjamin Franklin, John Locke, and William Herschel.
In the 19th century, French astronomer Camille Flammarion wrote a popular book titled the Plurality of Habitable Worlds. It was an extremely popular book that went through 33 editions in 20 years.
Flammarion was probably the first person to propose that aliens would be very different from life forms found on Earth.
All of these ideas were just that. Ideas.
They couldn’t really be proven or disproven. It is like pondering if we are living in a simulation or someone else’s dream.
Things began to change at the very end of the 19th century and the beginning of the 20th century.
The discovery which changed people’s thinking was radio waves.
Nikolai Tesla proposed that his wireless electrical transmission system could be used to communicate with people on Mars.
Tesla got something right and something wrong.
It was possible to communicate with Mars using electromagnetic waves. However, there were no Martians.
Tesla was far from alone in thinking that there might be life on Mars. Around the same time, the astronomer Percival Lowell announced that he had discovered canals on the surface of Mars.
Lowell spent a great deal of time observing Mars and created sketches based on his observations which showed lines on the surface. He interpreted these lines to be a vast system of canals on the planet that were created by an intelligent civilization.
He wrote several popular books on the subject and was largely responsible for the idea that there were intelligent Martians.
However, as telescopes improved, no one else could find his canals. His ideas were never taken seriously in scientific circles, even if they circulated for years in popular culture.
They were taken seriously enough that in August 1924, when Mars passed closer to the Earth than it would be for another 80 years, the United States conducted a “National Radio Silence Day” where radios would be quiet for five minutes every hour.
Several groups, including the US Naval Observatory, turned their antennas towards Mars to try and hear a signal.
Needless to say, they heard nothing.
Throughout the 20th century, our understanding of the cosmos improved, and we learned more about the size of our universe and the composition of our solar system.
Telescopes improved drastically, and we began sending probes to other planets.
The first real attempt to think about the issue seriously came from the astronomer Frank Drake at Cornell University in 1961.
Drake came up with what is known as the Drake Equation. I have previously done an entire episode on the Drake Equation, but just to summarize, it is an equation that lists all of the variables necessary to determine the odds of intelligent life in our galaxy.
These include the rate of star formation, the percentage of stars with planets, the percentage of planets which can support life, the percentage of planets which actually develop life, the percentage which develop intelligent life, the percentage which broadcast their existence to the universe, and the length of time a civilization exists.
Most of these variables were a mystery when the equation was proposed, and all they had were estimates, which were really just best guesses.
Other than the percentage of stars with planets, which appears to be close to 100%, we haven’t improved our estimates of most variables.
Drake also took the first step beyond just philosophizing about life on other worlds. He conducted the first actual search for intelligent life.
In 1960 he pointed the 26-meter radio telescope at the Green Bank Observatory in West Virginia at the stars Tau Ceti and Epsilon Eridani.
In particular, he looked in the 1.42 gigahertz part of the spectrum, which is called the “water hole” because it is near the hydrogen spectrum lines and is unusually quiet. Hydrogen, being the most common element in the universe, would be a natural place where other civilizations might broadcast if they are looking for attention.
He found nothing.
This was only a start. The galaxy is extremely big; this was only a brief peek through one pinhole.
What was needed was a long-term, continuous observation of the sky if there was to be any chance of finding something.
Ohio State University conducted the first real attempt at a long-term observation of extraterrestrial radio signals. In 1963 the university opened a radio observatory called The Big Ear, and from 1973 to 1995, the telescope was dedicated to listening for radio signals from outside our solar system.
In 1977, the Big Ear received a signal which became one of the most famous SETI signals ever recorded. It was dubbed the WOW Signal due to the comment written on the printout of the signal by one of the researchers.
It was a 72-second long burst emanating somewhere in the constellation Sagittarius. It was 30 standard deviations more powerful than the average signals recorded, and to this date, it remains one of the best candidates for an artificial signal ever found.
….however, no one has ever seen the signal since.
In 1971, NASA funded a SETI study called “Project Cyclops.” It was to be a massive radio telescope array covering the Earth with 1500 dishes. It was never built, but it became the basis for future SETI projects.
By the 1980s, more ambitious ideas were hatched.
The SETI Institute was founded in 1984 which would serve as a hub for various SETI projects.
One of the problems which was tackled in the 80s was the issue of spectrum analysis.
Searching for intelligence isn’t just a matter of the number of radio telescopes or the size of the radio telescopes, although that is a factor. You also had to scan an enormous number of frequencies. Literally millions of frequencies.
In 1985, Project META was launched, which stood for “Megachannel Extra-Terrestrial Assay.” It could analyze, via computer, 8.4 million frequencies down to .05 hertz.
This was replaced in 1995 with Project BETA, which could analyze 250 million channels.
In 1999, SETI @home was launched, which used the power of distributed computing. Participants could install software on their home computers that would check radio signals during their downtime. The program had hundreds of thousands of participants over the 20 years it was in operation. The project was put on hiatus in 2020.
SETI projects are usually low on the totem pole regarding priority for radio telescopes. They often get some time, but it is seldom a high priority.
There was a need to have a permanent array of radio telescopes working full-time on SETI observations.
The Allen Telescope Array, named after Microsoft co-founder Paul Allen, was supposed to be an array of 350 rather small 6.1-meter dishes which would act like a single 100-meter dish. Unfortunately, only 42 dishes were ever constructed, and it has limited operation due to funding shortfalls.
Here, I want to stress the difficulty of the entire SETI initiative. You are looking for something that you don’t know if it even exists. If it does exist, you don’t know where it is. You don’t know what technology they might be using to communicate, and even if you know what, you wouldn’t know how they are trying to communicate.
Then there is the slight problem of physics. The inverse square law says that the signal’s power is only a fourth as strong when you double the distance from something. The power is one-ninth as strong when it is three times the distance.
Over the vast distances of intergalactic space, radio waves become really weak.
There is also the small problem of the speed of light. If there was some distant civilization is listening for our signals with super sensitive technology, only civilizations about 100 light years away could hear because that is about how long we have been broadcasting radio waves.
Assuming they heard our broadcasts and they were 100 light-years away, it would take another 100 years for their signal to reach us.
That is just from our end of things.
If some extraterrestrial civilization wanted to send a signal out to some other civilization, it would require a tremendous amount of energy. You could somewhat overcome the inverse square law by broadcasting a highly focused beam of energy like a laser, but if you do that, you’d need to know exactly where to point it.
Even then, energy will still dissipate over extremely long distances. Some estimates suggest that if we wanted to communicate with another civilization tens of lightyears away, we’d need to broadcast with a radio signal that uses all of the energy produced on Earth.
It also might be that we are completely barking up the wrong tree. It could be that there is some advanced technology like StarTrek subspace communications that all the cool civilizations are using, and we just haven’t discovered it yet.
Advances in astronomy might make it easier to narrow down where in the sky we should look. Telescopes like the James Webb might be able to discover planets with a high probability of life. If we can find such planets, we could focus our efforts there. It would certainly be easier than trying to observe everything everywhere all at once.
Currently, the Search for Extraterrestrial Intelligence is mostly a side project in the world of astronomy. There is currently no government funding for any SETI projects, and there is unlikely to be any in the near future.
All current efforts are privately funded or rely on the spare time on telescopes.
The Search for Extraterrestrial Intelligence is one of the greatest unknowns there can be. The search’s who, what, where, and how are all mysteries.
SETI is sort of like the scientific equivalent of playing the lottery. The odds aren’t good, but if you should hit the jackpot it changes everything.