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Question of the Week: Is it really ET?

Every week, conditions permitting, we answer a question from our February 16, 2023 launch event Q&A session or from a Zooniverse participant. This week’s question comes from Manuel Soberanes Cobo: What would be considered clear indications that a radio signal is coming from an alien civilization?

This fundamental question has a two-pronged answer. We are looking for signals that are emitted beyond humanity’s reach and that natural systems cannot emit. 

The first criterion rules out terrestrial technology. Our most distant ambassador, the Voyager 1 spacecraft, is currently 159 astronomical units away from Earth (24 billion km or 15 million miles). If we detect a non-natural signal emitted from a source located light-years away, we will know with certainty that it is coming from an alien civilization. To test for a distant source, we first confirm that the signal is detected in one, and only one, direction on the sky. A signal that is detected in multiple directions on the sky is automatically ruled out as anthropogenic interference. Signals from global positioning satellites, for instance, are often detected through the antenna beam sidelobes in many different orientations of the primary beam.

The second criterion rules out natural systems. Signals with certain unusual patterns in the time or frequency domain, such as the sequence of prime numbers seen in the movie Contact, cannot be produced by natural systems. Likewise, natural processes cannot emit powerful signals where the power is highly concentrated in the frequency domain. For instance, generating a signal at a frequency of 1 billion cycles per seconds (1 gigahertz or 1 GHz) with most of the power confined to a 10 hertz-wide window requires engineering. We can be confident about this statement because multiple particles must be involved in the production of a powerful signal. In nature, these particles experience random motions, which broadens the signal in the frequency domain because of the Doppler effect. Let us consider the conditions necessary to confine the bandwidth of a 1 GHz signal to 10 Hz: the relative velocities of the particles participating in the emission would have to remain below 2 meters per second, and this uniformity in velocity would have to be maintained over the entire extent of the emission site. Fluid astrophysical settings cannot produce these conditions because the random velocities of particles due to thermal motions are much larger than 2 m/s, even in the coldest environments. There are some natural systems with remarkable emission properties, such as astrophysical masers. However, the narrowest reported maser emission line width is 550 Hz, more than 50 times larger than the narrowband signals that we are seeking.

To summarize, UCLA SETI is currently searching for narrowband radio signals from distant sources. Of course, any signal that appears to simultaneously satisfy both ET criteria would undergo extensive follow-up observations and confirmation. We would reprocess the data with independent software, reobserve with the Green Bank Telescope, reobserve with different telescopes, and share our data for independent evaluation by other experts in the field. 

Electromagnetically yours,

UCLA SETI

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Question of the Week: Is humanity detectable by aliens?

Every week, we answer a question from our February 16, 2023 launch event Q&A session or from a Zooniverse participant.  This week’s questions comes from Alejo Weyh: How much background noise is Earth sending out there? Do they have a better chance of finding our radio signals or do we have a better chance of finding them?

This week, we address an important question: do other civilizations know that we are here? It is not unusual to hear astronomers answer this question in the affirmative. However, apart from rather improbable conditions, the answer is almost certainly “No.” We have transmitted radio signals over distances approaching an Earth radius for approximately 120 years, and radio waves propagate at the speed of light. Our radio transmissions have reached a distance of 120 light years, illuminating a spherical bubble with a volume of 7.2 million cubic light years. Although this number may sound large, it represents only 1 millionth (0.0001%) of the volume of the Galaxy. The probability that another civilization resides in this tiny bubble is extraordinarily small, unless there are millions of civilizations in the Milky Way, which seems unlikely. Could another civilization have traveled to our local bubble and detected our transmissions? Perhaps, but even in that improbable situation, news of our existence would be confined to our bubble. Could another civilization further away have detected biosignatures in our atmosphere? Perhaps, but in that case they would not know whether terrestrial lifeforms are technological or even intelligent. The laws of physics lead us to conclude that no one knows about the existence of a technological civilization on Earth except for the improbable civilizations that would reside in our tiny, local bubble.

We answer this week’s second question unequivocally: we have a much better chance at detecting other technological civilizations than the other way around, a fact that motivates UCLA SETI searches. It is reasonable to assume that other civilizations have been technological much longer than we have been (see our webinar), perhaps preceding us by thousands or millions of years. Their detectability bubbles are therefore considerably greater than ours.

Electromagnetically yours,

UCLA SETI  

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Question of the Week: What would a technosignature look like?

Every week, we answer a question from our February 16, 2023 launch event Q&A session or from a Zooniverse participant.  This week’s questions come from David Michels: If you were ET, what would you transmit to phone home? What might the technosignature look like?

It is fun to speculate about how a technosignature might look. Our answer will focus on radio technosignatures. Although we could in principle detect radio signals that were not intended for detection by humanity, such as those produced by the radar or interstellar communication systems of other civilizations, SETI is far more likely to succeed if a civilization advertises its presence with radio beacons. We do not know if advanced civilizations operate radio beacons, but it is a reasonable hypothesis that can be tested with instruments such as the Green Bank Telescope. How would a civilization go about signaling its presence to an unknown civilization at another stage of development? It would seem sensible to broadcast a signal that is both likely to be detected and easily distinguishable from natural signals.

The first desirable trait – detectability – led Cocconi and Morrison (1959) to suggest searching near the 1420 MHz hydrogen emission line (see our previous post), on the assumption that all civilizations exhibit curiosity and know about the special role of hydrogen in our universe. This part of the electromagnetic spectrum may resemble meeting point areas at commercial hubs where you might go to find family and friends.

The second desirable trait – distinctiveness – has led to many ideas about characteristics that would rule out a natural origin for radio signals, such as unusual sequences of pulses or unusual spacings in the frequency domain, perhaps organized around prime numbers or other noteworthy mathematical constants. Perhaps the simplest way to transmit an unmistakably artificial signal is to concentrate a signals’s energy in a narrow range of frequencies, because natural systems are unable to do that. This consideration is driving the search for narrowband signals at UCLA SETI.

This week, our collaborators got us excited by noticing a signal that is clearly artificial and designed to grab someone’s attention. Regrettably, our verification process indicated that the signal is the product of human technology. The search continues!

This narrowband pulse generated much discussion on the Talk boards this week.

Electromagnetically yours,

UCLA SETI 

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Question of the Week: Do advanced civilizations use radio?

Every week, we answer a question from our February 16, 2023 launch event Q&A session or from a Zooniverse participant.  This week’s question comes from Clark Ramsey: Is it reasonable to believe that radio communication would be employed by more advanced civilizations?

This excellent question originates from the logical supposition that other civilizations are more advanced than we are (see our webinar). Therefore, it is reasonable to wonder whether “they” have abandoned radio technology and instead communicate by other means. Here is our take on this question. Even if most communications of advanced civilizations no longer rely on radio technology, it is possible that some of their communications still use radio signals. After all, radio waves are inexpensive to generate and propagate at the speed of light through habitable planetary atmospheres and the interstellar medium with little attenuation. Advanced civilizations are still bound by the laws of physics, and it is entirely conceivable that radio communications provide the best technological solution for some applications. The first part of our answer is a qualified yes. Our reasoning so far, however, is incomplete because it considers primarily signals that are not designed to be recognizable by other civilizations. 

What if a civilization decided to intentionally announce its existence? What would be the most effective broadcast strategy, bearing in mind that other civilizations, like ours, might be in the early stages of development? In this scenario, radio technology becomes a compelling contender in the arsenal of communication technologies, not only because of the propagation advantages of radio waves, but also because the most abundant element in the universe – hydrogen – relentlessly emits a distinctive radio signal. This reasoning was first articulated in a 1959 Nature paper by Giuseppe Cocconi and Philip Morrison, who described “a unique, objective standard of frequency, which must be known to every observer in the universe: the outstanding radio emission line at 1,420 Mc./s. (λ=21 cm) of neutral hydrogen”. In other words, one of the best ways to announce one’s existence to other civilizations is to broadcast a powerful, attention-grabbing radio signal near 1420 MHz. The second part of our answer, in the context of intentional interstellar greetings, is a more decisive yes. 

SETI is most likely to be successful if other civilizations operate powerful beacons. We cannot know a priori if other civilizations or radio beacons exist. Their existence is a scientific hypothesis that is testable with radio telescopes like the Green Bank Telescope (GBT). At UCLA SETI, we scrutinize the 1100–1900 MHz region of the spectrum, which includes the 1420 MHz hydrogen line, with the GBT. The probability of a detection may be low, but it is not zero, and the potential reward justifies the search.

We have been uploading our most interesting signals to http://arewealone.earth and have been enjoying the discussions of unusual signals on the Talk boards. We hope you will join us.

Electromagnetically yours,

UCLA SETI 

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First batch complete!

Hello!

Participants defied all expectations by retiring our first batch of data in less than six days! Based on Zooniverse guidance, we had sized our first batch of data to last approximately six weeks. We were ecstatic to receive an amazing 112,813 classifications of 7269 signals by 6275 classifiers (2012 registered and 4263 unregistered) in less than a week!  

Initial analysis of more than 5000 signals revealed that some of our previous RFI classes were hardly ever detected, whereas other pervasive RFI signals were not captured by any of the available RFI classes available on the platform. We made the decision to replace these four under-utilized classes with four new classes, which have already been detected many times. Our updated workflow was activated at the same time as the second batch of 8543 signals, and we are happy to report that the transition proceeded smoothly.  

Thank you for your amazing work!

UCLA SETI

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Launch!

Hello!

On Tuesday, we launched “Are we alone in the universe?”, a citizen science collaboration where anyone can contribute to the search for extraterrestrial civilizations. We are thrilled and grateful that more than 2000 volunteers have contributed over 100,000 classifications in just a few days. Our first batch of data with ~7500 images is almost exhausted, and we will upload a second batch soon. The discussions on the Zooniverse Talk boards have also been fascinating and rewarding, with an offer by a participant (@fnogal) to translate the project into Portuguese, identifications of unusual signals and potentially missing classes, and a description of audio analogs of the radio signals by two participants (@Drmike8888 and @satsig).

On Thursday, we hosted a Zoom webinar to describe details of the UCLA SETI search and the Zooniverse collaboration. The event was moderated by Fritz Demopoulos (UCLA SETI donor and Board of Advisors of UCLA Earth, Planetary, and Space Sciences). The speakers were Jean-Luc Margot (Professor, UCLA Earth, Planetary, and Space Sciences and UCLA Physics and Astronomy) and Megan Li (Graduate Student, UCLA Earth, Planetary, and Space Sciences Department). Attendees asked many interesting questions. We did not have time to answer all the questions and we will try to answer them in future blog posts or Zoom events.

Los Angeles Times writer Corinne Purtill wrote a thoughtful and engaging feature about our collaboration. To our surprise and delight, the article, “UCLA is asking for the public’s help in finding signs of extraterrestrial intelligence,” made the front page of the print edition (If you hit a paywall, you may try an alternate link). Jacob Margolis of LAist.com also wrote a fun segment that aired in Los Angeles. And Sarah Al-Ahmed of The Planetary Society produced a wonderful podcast about the project. We are grateful to all of them for promoting our collaboration, and to all of you who are inviting your social and professional networks to join us. We are on Facebook, Instagram, and Twitter. 

We are excited to see what the future of the collaboration holds.

With thanks and appreciation,

UCLA SETI

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Introducing the Science and Communications Team

Hello!

We are thrilled by the response to our project “Are we alone in the universe?” since our launch on February 14, 2023. Today, we would like to introduce the Science and Communications Team that we assembled to operate the project. A few of our goals include writing code, analyzing unusual signals, responding to questions posted to the Talk discussion boards, making the space welcoming and inclusive, and producing social media content.

UCLA SETI team
The Science and Communications Team prior to the launch of “Are we alone in the universe?” From left to right: Ella, Jay, Megan, Jeremy, Priscella, Jean-Luc.  Not pictured: Liam.

The Science and Communications Team includes:

Ella, a third-year astrophysics student at UCLA, who hails from Southern California and enjoys hiking and baking.

Jay, a third-year astrophysics student at UCLA, who hails from Michigan and enjoys observing the night sky and playing chess.

Jeremy, a first-year astrophysics student at UCLA, who hails from Massachusetts and enjoys origami and stargazing.

Liam, a second-year astrophysics student at UCLA, who hails from California and enjoys running, soccer, and rock-climbing.

Priscella, a second-year cognitive science student at UCLA, who hails from Texas and enjoys painting and making jewelry.

Megan, a first-year graduate student in planetary science at UCLA, who is a Los Angeles native who owns two large, poorly behaved cats.

Jean-Luc, a Belgian-born planetary astronomer who teaches at UCLA and was fortunate to meet SETI pioneers Carl Sagan, Frank Drake, Jill Tarter, and Paul Horowitz.     

We stand ready to answer your questions and look forward to engaging with many of you on http://arewealone.earth soon!

Sincerely,

UCLA SETI

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Launch preparations

Hello!

Today, we launched our citizen science collaboration “Are we alone in the universe?”. To prepare for our launch, we have assembled a small team of UCLA students to aid in operating the project.

In preparation for our launch, the science and communications team reviewed citizen science best practices. We have discussed how to respond to questions on the ‘talk’ forums. Our goal is to make this space welcoming, supportive, and inclusive. We are discussing many ideas to promote engagement with a variety of rewards. Additionally, we have been brainstorming content for our social media channels (Facebook, Instagram, and Twitter) and blog. The initial process of promoting the launch included everything from designing logos and launch graphics to creating content for the Zooniverse newsletter, Twitter feed, and this blog post. 

To kick off our launch, we will also host a launch event on Zoom on February 16, 2023 at 6:00 pm PST (register here). We are thrilled to share the excitement of our search for life in the universe with the general public and look forward to engaging with many of you on Zooniverse soon.

Warm Regards,

UCLA SETI