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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Avi Loeb | 1/4 | https://en.wikipedia.org/wiki/Avi_Loeb | reference | science, encyclopedia | 2026-05-05T13:17:07.760062+00:00 | kb-cron |
Abraham "Avi" Loeb (Hebrew: אברהם (אבי) לייב; born February 26, 1962) is an Israeli-American theoretical physicist who works on astrophysics and cosmology. Loeb is the Frank B. Baird Jr. Professor of Science at Harvard University. He chaired the Department of Astronomy from 2011 to 2020, and founded the Black Hole Initiative in 2016. Loeb is a fellow of the American Academy of Arts and Sciences, the American Physical Society, and the International Academy of Astronautics. In 2015, he was appointed as the science theory director for the Breakthrough Initiatives of the Breakthrough Prize Foundation. Loeb has published popular science books including Extraterrestrial: The First Sign of Intelligent Life Beyond Earth (2021) and Interstellar: The Search for Extraterrestrial Life and Our Future in the Stars (2023). Since 2017, Loeb has made a series of claims that alien space craft may be in the Solar System. He has argued that ʻOumuamua and other interstellar objects, including the reputedly interstellar meteor CNEOS 2014-01-08, are potential examples of such craft. These claims have been widely rejected by the scientific community. In 2023, he claimed to have recovered spherules formed by the impact of CNEOS 2014-01-08 that he alleged could be evidence of an alien starship, but the location in the ocean where he recovered the spherules was based on mistaking a seismic signal from a truck for the impact of the meteor. During an appearance on Joe Rogan's podcast, he also claimed that whether an ancient "sophisticated civilization" existed on Earth before humanity is a credible question to ask. Loeb tends to publicize his results before undergoing peer review, contributing to a climate of sensationalism around his claims.
== Life and career == Loeb was born in Beit Hanan, Israel, in 1962. He took part in the Talpiot research program while serving in the Israeli Defense Forces at age 18. While in Talpiot, he obtained a BSc degree in physics and mathematics in 1983, an MSc degree in physics in 1985, and a PhD in plasma physics in 1986, all from the Hebrew University of Jerusalem (HUJI). During his doctoral studies, Loeb conducted research at the Soreq Nuclear Research Center in Yavne. His PhD thesis focused on the modeling of plasma acceleration of charged particles. From 1983 to 1988, he was invited by the U.S. Strategic Defense Initiative to work on a new propulsion method for high-speed projectiles. Between 1988 and 1993, Loeb was a long-term member at the Institute for Advanced Study at Princeton, where he started to work in theoretical astrophysics under the supervision of John Bahcall. In 1993, he moved to Harvard University as an assistant professor in the department of astronomy, and was tenured three years later. Since 2007, he has been Director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics. Since 2012, Loeb became the Frank B. Baird Jr. Professor of Science at Harvard. Loeb has written eight books, including the textbooks How Did the First Stars and Galaxies Form? and The First Galaxies in the Universe. He has co-authored many papers on topics in astrophysics and cosmology, including the first stars, the epoch of reionization, the formation and evolution of massive black holes, the search for extraterrestrial life, gravitational lensing by planets, gamma-ray bursts at high redshifts, the use of the Lyman-alpha forest to measure the acceleration/deceleration of the universe in real time, the future collision between the Milky Way and Andromeda galaxies, the future state of extragalactic astronomy, astrophysical implications of black hole recoil in galaxy mergers, tidal disruption of stars, and imaging black hole silhouettes. Together with his postdoc James Guillochon, Loeb predicted the existence of a new population of stars moving near the speed of light throughout the universe. Together with his postdoc John Forbes and Howard Chen of Northwestern University, Loeb made another prediction that sub-Neptune-sized exoplanets have been transformed into rocky super-Earths by the activity of the black hole Sagittarius A*. Together with Paolo Pani, Loeb showed in 2013 that primordial black holes in the range between the masses of the Moon and the Sun cannot make up dark matter. In 2025, Loeb, in collaboration with Oem Trivedi, proposed that dark matter could consist of remnants of Planck Stars formed after the evaporation of primordial black holes. Loeb led a team that reported tentative evidence for the birth of a black hole in the young nearby supernova SN 1979C. In collaboration with Dan Maoz, Loeb demonstrated in 2013 that biomarkers, such as molecular oxygen (O2), can be detected by the James Webb Space Telescope (JWST) in the atmosphere of Earth-mass planets in the habitable zone of white dwarfs. In 2018, he served a term as chair of the board on Physics and Astronomy (BPA) of the National Academies of Sciences, Engineering, and Medicine (NASEM).
=== Life in the universe === In 2013, Loeb wrote about the "Habitable Epoch of the Early Universe", noting that the Cosmic Microwave Background would temporarily have been at temperatures compatible with liquid water around 15 million years after the Big Bang. In April 2021, he presented an updated summary of his ideas of life in the early universe. In 2020, Loeb published a paper about the possibility that life can propagate from one planet to another, followed by the opinion piece "Noah's Spaceship" about directed panspermia.
=== Claims about alien life === Loeb's claims about alien life have attracted sustained criticism from other scientists. Steve Desch, an astrophysicist at Arizona State University referred to Loeb's claims as "ridiculous sensationalism" which represent "a real breakdown of the peer review process and the scientific method". Some of Loeb's claims have been described as conspiracy theories, with USA Today referring to Loeb's speculation about 3I/ATLAS as an "outlandish conspiracy theor[y]." Other scientists have described Loeb's theories as "nonsense", comparable to the idea that "the moon is made of cheese." In 2024, Loeb delivered a speech in which he declared his view that the Messiah will be an alien who arrives from outer space.
==== ʻOumuamua ====