Harvard astrophysicist Avi Loeb warns that 3I/ATLAS’s unnatural acceleration, blue-tinged brightness spike, and perfectly controlled trajectory suggest it may be engineered rather than a comet, leaving scientists both alarmed and shaken as they confront the unsettling possibility that the object could be observing us.

Harvard astrophysicist Avi Loeb, one of the most outspoken and controversial voices in modern astronomy, has stepped into the global debate surrounding 3I/ATLAS — and his latest remarks are already sending shockwaves through scientific institutions around the world.

In a private seminar at the Harvard–Smithsonian Center for Astrophysics on November 12, 2025, later leaked through attendees, Loeb delivered what some are now calling the most provocative assessment of an interstellar object since he labeled ’Oumuamua a potential “light sail” eight years ago.

According to Loeb, newly released NASA telemetry shows that 3I/ATLAS’s precise, stable trajectory, its non-gravitational acceleration, and its six-minute sequence of unexplained brightness spikes are all wildly inconsistent with natural cometary behavior.

He pointed to the object’s unusually blue spectral signature, which suggests a reflective surface that doesn’t match typical dust, ice, or organic-rich materials found in long-period comets.

“Look at the numbers,” Loeb said, pacing before the room of graduate researchers.

“No outgassing.

No jets.

No rotational tumble.

No thermal vents.

Yet it moves.

Objects don’t just accelerate without a force acting on them.

Something is driving it — or something inside is responding to external stimulus.”

Multiple attendees later recalled a moment when Loeb paused for nearly a full minute before adding: “If we continue to call this a comet, then we are ignoring the very data we claim to cherish as scientists.”

3I/ATLAS, first detected in April 2025, has remained under near-continuous observation ever since NASA quietly flagged its incoming hyperbolic trajectory.

But while the agency maintains that its current classification as a comet is simply the “most conservative” interpretation of available data, Loeb argues that the conservative approach may, in fact, be the least scientific.

In his analysis, the object’s path through the solar system resembles a technically optimized flyby trajectory — one that minimizes solar heating, maintains a constant orientation relative to the Sun, and produces no visible debris.

This combination, Loeb says, mirrors the behavior of an intact, engineered structure rather than a fragile, icy body shedding mass as it nears the inner system.

He also emphasized the now-famous anomaly first reported by NASA’s Jet Propulsion Laboratory on October 28: a rapid fourfold increase in brightness over six minutes, with no thermal emissions, no particulates, and no plume.

The phenomenon coincided with a direct radar sweep from the Goldstone Solar System Radar and has since been confirmed by both the Subaru Telescope in Japan and the European Space Agency’s Gaia mission.

“That timing is not just strange,” Loeb told the audience.

“It is meaningful.

You don’t get synchronized behavior in nature unless a process links them.

The question is: what process?”

When one student asked whether he was suggesting hostile intent, Loeb reportedly responded carefully:
“I’m not saying it’s hostile.

I’m saying it might be designed.

When technology passes near a civilization, we should consider the possibility that our instruments aren’t the only ones doing the observing.”

This remark — the one now making headlines across social media — wasn’t meant to be theatrical.

Those present said Loeb delivered it quietly, matter-of-factly, as if stating a simple astrophysical possibility.

NASA, meanwhile, has declined to comment directly on Loeb’s statements.

But one senior agency scientist, speaking anonymously, admitted that “the object is not behaving like anything in our catalog” and that internal debates about its nature are growing increasingly tense.

As 3I/ATLAS approaches its December perihelion, observatories around the world are preparing for a new round of high-resolution imaging.

Some hope the data will settle the debate; others fear it may open entirely new questions.

For Loeb, the stakes go far beyond astronomy.“When an interstellar object from an unknown origin demonstrates behavior inconsistent with natural physics,” he said, “we owe it to ourselves — and to future generations — to consider every possibility, not just the comfortable ones.”

Whether 3I/ATLAS is a comet, an artifact, a probe, or simply an unprecedented natural anomaly, its passage through the solar system is becoming one of the most closely watched events in modern science.

And if Loeb is right — if this object is not just passing through, but learning about us as we attempt to learn about it — then humanity may be at the beginning of a scientific confrontation unlike anything in its history.

For now, astronomers wait, instruments ready, eyes fixed on the silent interstellar visitor that refuses to behave like a rock.