A Menorah of Stars Over Our Heads

Avi Loeb
5 min readDec 14, 2023


My morning jog happened before sunrise, because my day was packed with a hectic schedule, including an online lecture in Poland, followed by an hour-long podcast interview with Chris Cuomo, a TV interview in Australia, a radio interview in South Africa, an online meeting with the White House, and an evening concert at the American Academy of Arts & Sciences.

Instead of the familiar red horizon at sunrise, I witnessed a totally dark sky with an ocean of stars overhead. The Milky way looked like a giant Menorah featuring numerous stars lit by nuclear fusion in place of the traditional eight (plus one) candle-lights for Hanukkah. I wondered if beings on exoplanets near these lights look at the Sun while jogging in their early morning hours.

The Voyager spacecraft will venture to interstellar space at a speed of 15 kilometers per second relative to the Sun. In less than two billion years, it would reach stars on the other side of the Milky-Way disk. In case it would be captured by aliens, they could study the images, music and sounds imprinted on its Golden Record. However, given that Voyager is about to lose its utilities and become space trash on a random trajectory, the chances for that to happen are daunting.

During a random journey to the other side of the Milky Way, Voyager’s closest distance to an Earth-sized exoplanet would be a thousand times the Earth-Sun separation, requiring detection systems that are far better than we possess.

Conversely, if any interstellar object within the orbit of the Earth around the Sun is found to be a non-functional spacecraft from an alien civilization, there must be a quadrillion of them within the Solar system, out to a hundred-thousand times the Earth-Sun separation. Such circumstances would offer many opportunities to search for alien Golden Records.

What about electromagnetic transmissions? Recently, communication signals from the Voyager 1 spacecraft suffered from a computer glitch. The information took nearly a day to reach Earth at the speed of light. For comparison, the light from stars on the other side of the Milky-Way disk was emitted fifty thousand years ago. Any two-way conversation with an alien civilization has to be restricted to the distance that light can travel during a human lifetime. There are only hundreds of Sun-like stars within that distance.

The first wireless radio transmission from Earth by Guglielmo Marconi was exactly 122 years ago. Given current trends, it is reasonable to imagine that our civilization is in the middle of its technological lifespan before it will die from self-inflicted wounds in nuclear, biological or AI-triggered catastrophes. If 244 years is the characteristic lifetime of transmitting civilizations, we need to search through tens of millions of stars before we will be able to respond to the transmitted signal from a civilization like ours. But the distance at which we can find so many stars provides no opportunity for us to respond before our conversation partner ghosts us.

The remaining opportunity is for us to correspond with functional devices that were sent from afar billions of years ago, an improved version of Voyager that can repair itself and potentially self-replicate, as envisioned by John von Neumann 74 years ago. The required number of such probes is much smaller than space trash because they may target the habitable region around stars where they can consume liquid water and use electrolysis to break water molecules to hydrogen and oxygen as fuel. In that case we might need to infer the qualities of the senders from the probes that visit us, similarly to the challenge of the prisoners who can only watch shadows of objects behind them in Plato’s Allegory of the Cave.

Next week, a new policy bill might be signed into law within the fiscal 2024 National Defense Authorization Act, that would mandate the establishment of an “Unidentified Anomalous Phenomena (UAP) Records Collection” in the National Archives. The newly released House-Senate conference report for the legislation states: “Not later than 60 days after the date of the enactment of this Act, the Archivist shall commence establishment of a collection of UAP… The Collection shall consist of record copies of all Government, Government-provided, or Government-funded records relating to UAP, technologies of unknown origin, and non-human intelligence (or equivalent subjects by any other name with the specific and sole exclusion of temporarily non-attributed objects), which shall be transmitted to the National Archives… No UAP record shall be destroyed, altered, or mutilated in any way… The Archivist shall establish requirements for periodic review of postponed UAP records that shall serve to downgrade and declassify information… Each unidentified anomalous phenomena record shall be publicly disclosed in full, and available in the Collection, not later than the date that is 25 years after the date of the first creation of the record by the originating body, unless the President certifies that continued postponement is made necessary by an identifiable harm to the military defense, intelligence operations, law enforcement, or conduct of foreign relations; and the identifiable harm is of such gravity that it outweighs the public interest in disclosure.”

As I completed my morning jog, I looked up at the numerous stars overhead with the hope that we might learn more about our neighbors outside the solar system during my lifetime. Ad Astra!


Image credit: Chris Michel (October 2023)

Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, was published in August 2023.



Avi Loeb

Avi Loeb is the Baird Professor of Science and Institute director at Harvard University and the bestselling author of “Extraterrestrial” and "Interstellar".