Are We Listening for Aliens at the Wrong Time?
- A Meeting Place Nobody Has Booked
- Why SETI Scientists Think About Where and When to Listen
- Forty-Two Dishes at Hat Creek
- The First Run Meets Earth's Radio Noise
- The Larger Survey Leaves Ten Places to Revisit
- Sofia Sheikh Explains the Hunt for Radio Technosignatures
- Choosing Stars and Choosing a Moment
- One Appointment Among Many
Imagine arranging a meeting with someone you have never contacted. You cannot call, leave a note, or agree on a place. Even if you both choose the same landmark, arriving a day apart means you miss each other. Searching for an alien signal has a version of that problem.
Scientists use radio telescopes to look for signs of technology beyond Earth. People use radio waves to carry information, and those waves can travel through space. If another civilization exists, it might use radio too. By collecting radio waves from space, researchers can look for signals that could have come from its technology.
The difficulty is choosing where and when to listen. This search tests whether Earth's yearly trip around the Sun could give researchers and a possible sender the same clue.
A Meeting Place Nobody Has Booked
Picture a line from the Sun through Earth, continuing out into space. An observer along that line could see Earth cross the Sun's face. This crossing, called a transit, could help that observer notice our planet.
Both sides could use the crossing to choose a time for contact. From Earth, looking toward that observer means looking away from the Sun. The new strategy follows this anti-solar direction as it changes during Earth's orbit.
The plan assumes a sender would allow for the time radio waves take to reach Earth.
SETI Institute scientist Sofia Sheikh discussed the where-and-when puzzle with Seth Shostak in the earlier interview Second Guessing E.T.
Why SETI Scientists Think About Where and When to Listen
Forty-Two Dishes at Hat Creek
The search uses the Allen Telescope Array at Hat Creek in northern California. The facility has 42 radio dishes. For each observation, the dishes in use collect radio waves. Computers combine their measurements to focus on chosen patches of sky.
The array supports SETI, the search for intelligent life beyond Earth, as well as other radio astronomy. Researchers must choose where to aim the telescope. A timing strategy gives the team a reason to study one patch of sky, then move with the changing alignment.
- Explore the scientific search for signals from other civilizations
- Follow SETI’s equipment, history, and unanswered questions
- Read an astronomer’s account of the hunt for extraterrestrial intelligence
The First Run Meets Earth's Radio Noise
Tuning a radio to a station means selecting a frequency. A signal within a very small range of frequencies can be a clue to technology. Researchers look for these narrow signals, but human equipment makes them too.
In summer 2023, the team tested the approach with 20 dishes for about 17 hours across three nights. Computers flagged roughly 1.9 million possible signals. After checking them, researchers found that human radio interference explained the detections. The pilot had not found evidence of an alien signal.
The SETI Institute's explanation of candidate signals calls for further observations and checks at another telescope. Researchers need to find out whether a signal comes from the target in space or radio activity here on Earth.
The Larger Survey Leaves Ten Places to Revisit
A separate, larger search followed in 2024–2026. An October 2026 conference paper by Isabel Gerrard and Sofia Sheikh reports its progress.
The team had completed 126 telescope observing sessions and analyzed data from about two-thirds of them. Researchers inspected more than 11,000 plots—charts showing the recorded radio signals over time.
Twenty-five plots showed narrow signals that changed frequency and were stronger in the target direction than in a nearby direction checked at the same time. Those plots came from ten points in the sky marked for another look.
The 25 plots and ten directions are leads to investigate. The paper does not establish who or what produced the signals.
Looking again helps test whether the signal really comes from that part of space. Even confirming an alien signal would leave another job: finding out whether it carries a message and what that message means.
Sofia Sheikh Explains the Hunt for Radio Technosignatures
Carl Sagan's Contact turns a radio detection into a first-contact story. It is fiction; the real search is still working through its candidates.
- Follow a first-contact story written by astronomer Carl Sagan
- Explore how an extraordinary discovery could challenge science, belief, and politics
- Enjoy a longer fictional journey after reading about the search for alien intelligence
Choosing Stars and Choosing a Moment
A related search had already asked which stars might offer a useful view of Earth. In a 2020 study, Sheikh and collaborators used the Green Bank Telescope to observe 20 nearby stars. From those stars, someone could see Earth pass across the Sun and might notice our planet.
The study found no evidence of a radio signal from alien technology. A signal seen in the direction of one star, HIP 109656, was consistent with human interference. That result covers the targets and types of signals checked; it does not show that those systems contain no life.
Choosing those stars answers where to look. Following the anti-solar direction adds a timing test: whether a signal might arrive during the alignment.
One Appointment Among Many
The wider SETI effort also includes searches for laser pulses. A radio search covers only one possible way for another civilization to send a signal.
For the ten directions flagged in the October report, the next step is another observation. That could help the team decide which signals deserve more attention and which came from human activity.
