When physicists propose an antigravity experiment, the UAP world listens

Sabine Hossenfelder has spent several years teaching her viewers one specific test. She calls it the press-release coat. A paper says it has done something spectacular. The actual paper, read carefully, has done something much smaller. The press release has dressed the smaller thing up. She takes the coat off. Her audience watches her do it.

On July 17, 2026, she put up a video with the title "Scientists Have Figured Out How to Make Antigravity." The video was not about antigravity in any device sense. It was about a four-page paper that, if its tabletop experiment works, will prove gravity is a quantum field. The antigravity is a side-effect, conditional on the experimentalist throwing away roughly half the data.

What makes the video worth pausing on is not the physics. It is the audience that shows up when the word antigravity gets used in a headline — and what that audience has been doing with the word, on its own, since the late 2000s.

The paper, in the physicist's own words

The paper is "Repulsive Gravitational Force as a Witness of the Quantum Nature of Gravity," posted to the arXiv preprint server on February 12, 2026. Authors: Pablo L. Saldanha of the Federal University of Minas Gerais, in Brazil; Chiara Marletto and Vlatko Vedral, both at the University of Oxford. Four pages, two figures. It is a direct follow-up to the original Bose-Marletto-Vedral proposal for witnessing quantum gravity through gravity-mediated entanglement, an idea physicists have been refining and arguing over since 2017.

Vedral laid out the argument himself for Popular Mechanics and on his own Substack in June 2026, using a beach-ball analogy. Take a small mass and put it in a quantum superposition — a state in which it is, in some well-defined sense, in two places at once. Put a probe mass nearby. Wait. Measure the first mass in a different basis, and post-select: only keep the runs that give you a particular outcome. On the runs you keep, the probe mass gets a momentum kick in the opposite direction from what gravity should produce.

"It looks, for an instant, like gravity pushed it away," Vedral writes.

Then he does something most authors in this part of the literature do not. He names the result for what it is not. The effect is not that gravity has become repulsive. It is that quantum interference, between the two possible positions of the source, has produced an effective repulsion that only shows up in the half of the data you decide to keep. The other half of the data still says gravity is attractive. So does the average.

Vedral does not pretend the experiment is around the corner. He puts a realistic target date for a clean, conclusive result in the early 2030s. The team working on it, he says, is at INRIM, the Italian national metrology institute: Marco Genovese, Fabrizio Piacentini, Ettore Bernardi. None of them are American. None of them are part of any U.S. UAP research program.

He closes the Popular Mechanics essay by quoting himself. The line is worth keeping in full: "We are on the cusp of solving one of the biggest mysteries of physics, and, as a bonus, might be able to develop technology that even renowned science-fiction writer Arthur C. Clarke couldn't have imagined."

That is the press-release coat, and Vedral is wearing it. Hossenfelder's point, in the video, is that the paper under the coat is real, serious, and is not about antigravity machines.

It is also not the consensus view that the experiment is technically close. Independent analyses of the BMV family of proposals have argued that gravity-mediated entanglement alone does not automatically prove gravity's quantum nature without additional assumptions about locality, and that turning the thought experiment into a working laboratory measurement remains a metrology problem several orders of magnitude beyond current techniques. The 2030s target is Vedrals; the harder problems around it are not his to solve alone.

What the word has meant in the U.S., since the late 2000s

The phrase "novel propulsion" has had a second life in the United States since the late 2000s. It is the term used inside a small, persistent network of physicists and intelligence-adjacent researchers who have treated speculative propulsion as a funded research program, not as a science-fiction idea.

The clearest starting point is not Puthoff's private institute. It is a specific government contract.

In 2007, Senators Harry Reid of Nevada, Daniel Inouye of Hawaii, and Ted Stevens of Alaska — known on Capitol Hill as the "Inouye-Stevens-Reid" trio for their earmark work — secured a $22 million sole-source Defense Intelligence Agency award for the Advanced Aerospace Weapon System Applications Program, AAWSAP. The contract went to Bigelow Aerospace Advanced Space Studies, BAASS, a subsidiary Robert Bigelow had incorporated for exactly this purpose. Bigelow, a Las Vegas hotelier with a long public interest in UAP, had by then already been funding NIDS, the National Institute for Discovery Science, at Skinwalker Ranch. The AAWSAP money was the moment the speculative-propulsion conversation went from private funding to a government line item.

Between 2008 and 2012, AAWSAP and its more narrowly focused successor, AATIP, produced 38 Defense Intelligence Reference Documents — DIRDs — on topics ranging from warp drives and traversable wormholes to vacuum energy and antigravity. Hal Puthoff and physicist Eric Davis, both already established in the U.S. frontier-physics community, authored several of them. A DIA information memorandum from October 2009 lists the funded research areas as "lift, propulsion, control, power generation, spatial/temporal translation, materials, structural configuration, signature reduction, human interface, human effects, and armament," and lists "Antigravity for Aerospace Applications" explicitly among the reviewed research topics.

On June 24, 2009, Reid separately wrote to Deputy Secretary of Defense William Lynn III, asking that the DIA assess "far-term foreign advanced aerospace threats" over a forty-year horizon, with a technical scope running across "advanced lift, propulsion, the use of unconventional materials and controls, signature reduction, weaponry, human interface and human effects."

A separate AATIP memo, drafted in 2017 by the program's then-director Luis Elizondo for Deputy Secretary of Defense Patrick Shanahan, never officially issued, but released through a FOIA fight won by The Black Vault, restates the same list in a more compressed form: "beyond next generation technologies in the areas of lift, propulsion, cloaking, and human effects." The program was collecting reports on "unexplained or unknown aerial systems" from across DoD.

Antigravity is not, in any of those documents, the headline. It is one item among 38 reports and a longer list of research areas. But the list is real, the $22 million was real, and the U.S. national-security state did, on paper, ask whether someone could build a craft that lifts without conventional propulsion — with money behind the asking.

The Defense Intelligence Agency also kept, in its classified archive, a longer survey called Antigravity for Aerospace Applications, released through the DIA's electronic FOIA reading room. The document is a literature review, not a result. It walks through the published theoretical work on quantum-vacuum propulsion, negative-energy density, and the Casimir effect, and cites an experimental proposal by the Italian physicist Enrico Calloni and colleagues, who suggested building a stacked-cavity Casimir device and looking for a very small upward force. The report treats the idea as feasible in principle but never attempted at the scale Calloni described.

That is the older "antigravity" line. The Oxford paper is a different line entirely. The two share a word. They do not share a mechanism. The DIA-era research bet on giving an object negative effective mass through vacuum engineering. The Oxford group bets on making gravity look repulsive for a single, post-selected measurement outcome, by exploiting quantum interference. If the Oxford experiment holds up, gravity is quantum — and the U.S. program that spent four years and $22 million funding zero-point-energy and vacuum-engineering approaches was, at minimum, answering a different question.

Who is not at the table

The Oxford experiment is being pursued by an Italian metrology institute, with a Brazilian theorist as the lead author, housed at a British university, with no announced U.S. partner. The AAWSAP/AATIP funding lane closed by 2012. Nothing of comparable scale replaced it. The U.S. UAP research network that grew up around Puthoff, Davis, Bigelow, Elizondo, and To The Stars has not, on the public record, signed on to the Oxford program. Nor has any U.S. group claimed to be running an equivalent.

The DIA's antigravity survey is publicly available. The Casimir-stack experiment it describes has not been built by any U.S. laboratory. The Oxford group's experiment is at INRIM. The decade-and-a-half-long U.S. conversation about "novel propulsion" is not, today, a conversation that includes an active experimental program on any of the ideas it named.

That is the line the UAP community has rarely been willing to draw in public. Antigravity, in that community, is usually described as a hypothesis about what a recovered craft might use — not as a research program the United States funded at modest scale for four years, let lapse, and has not revisited in any visible form since. The Oxford paper sits, awkwardly, between those two readings. It is too early to claim it as vindication. It is too real to keep treating as a footnote.

What the two communities still disagree about

The two readings of the word antigravity cannot both be right.

If the Vedral/Marletto/Saldanha experiment works, gravity is a quantum field, and the only honest way to produce a repulsive gravitational effect is through quantum interference. The zero-point-energy and vacuum-engineering program the DIRDs summarized would, in that case, be a side road that has been carefully mapped and is, by the Oxford group's lights, the wrong map.

If the zero-point-energy program turns out to be the more productive path, the Oxford experiment is an important measurement of a different question, unconnected to how anyone might actually build a propulsion device.

Either way, the people who have long claimed the U.S. government was sitting on a working antigravity program are not vindicated by the Oxford paper. They are, in their quiet way, contradicted by it — by simply watching a more careful and more international piece of physics arrive under the same name.

That is the uncomfortable point Hossenfelder's video, in fifteen minutes, walks the viewer past. It is also the point no UAP researcher has yet been willing to put in writing. The community that has used the word antigravity as a long-running hypothesis about recovered technology is watching, in real time, a much better-funded and much more public piece of physics show up under the same name, and the two have almost nothing to say to each other.

Who is in the room in the early 2030s

Vedral puts a clean result in the early 2030s. INRIM is the lab. Saldanha is the theorist. British, Brazilian, and Italian funding agencies are the backers. The U.S. UAP research community is reading along from outside, working with a vocabulary — lift, propulsion, cloaking, human effects — that a $22 million contract helped popularize but no longer funds.

There is a version of the next several years in which the experiment works, gravity is shown to be quantum, the post-selection result holds, and the Oxford-Bristol-Brasilia-Italian collaboration publishes one of the cleanest measurements in the history of fundamental physics. There is another in which the experiment stalls, and antigravity stays on the speculative shelf it has occupied since the 1990s. There is a third, unwritten version in which a U.S. lab, with the kind of stable funding AAWSAP and AATIP never quite had, runs an equivalent program and gets there first.

None of those three versions is more likely than the others, today, but only one of them has any U.S. physicists at the table. The other two leave the U.S. UAP research community where it has been for a decade and a half: reading other people's papers, building other people's vocabulary, and waiting for someone else to do the experiment.

Sources

• Saldanha, Marletto, Vedral, "Repulsive Gravitational Force as a Witness of the Quantum Nature of Gravity," arXiv:2602.12266, submitted 12 February 2026
• Vlatko Vedral, "We Can Make an Antigravity Machine — And Unlock a 'Mind-Blowing' Future, Oxford Physicist Says," Popular Mechanics, 19 June 2026
• The Quantum Insider, "Gravity Still Sucks — But Researchers Say Quantum Interference Could Make It Push," 20 February 2026
• Sabine Hossenfelder, "Scientists Have Figured Out How to Make Antigravity," YouTube, 17 July 2026
• Defense Intelligence Agency, "Antigravity for Aerospace Applications," FOIA Electronic Reading Room, File ID 170027
• The Black Vault, AATIP memo drafted by Luis Elizondo (2017), intended for Deputy Secretary of Defense Patrick Shanahan, FOIA release 21-F-1154
• Senator Harry Reid to Deputy Secretary of Defense William Lynn III, 24 June 2009, DIA FOIA Reading Room, File ID 170016
• Defense Intelligence Agency Information Memo, 30 October 2009, DIA FOIA Reading Room, File ID 170060
• UAP Logbook, "Hal Puthoff's UFO paper trail runs from SRI to To The Stars," published 18 June 2026