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The Physicist Who Uncovered "Negative" Time

Curt Jaimungal

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This conversation belongs in a category I wish were larger on this channel: the experimentalist who also thinks (deeply) about foundations. Professor Aephraim Steinberg, winner of Physics World’s Breakthrough of the Year in 2011, is that species! For basically 30 years, he’s been measuring aspects of physics that others wouldn’t touch: Bohmian trajectories, Heisenberg’s disturbance bound (he showed it was wrong), even where the photon is inside the double slit (which most textbooks will tell you is impossible). His lab measured negative time — and it keeps reappearing across completely different experiments, stubbornly suggesting it means something.

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TIMESTAMPS:
00:00:00 - Defining Negative Time
00:06:50 - Quantum Trajectory Theory
00:12:44 - The Holland Tunnel Analogy
00:18:40 - Resonant Atomic Interactions
00:26:05 - Superluminal Energy Propagation
00:32:00 - Eight Velocities of Light
00:38:00 - Causality and Retrocausality
00:44:00 - Dwell Time vs. Delay
00:50:24 - Time: Operator or Parameter?
00:58:21 - Bell’s Theorem and Realism
01:04:55 - Heisenberg’s Measurement Disturbance
01:11:26 - Weak Measurement Formalism
01:17:37 - Time Symmetry and Entropy
01:27:07 - Bohmian Trajectories Observed
01:35:56 - Spin-Statistics and Indistinguishability
01:42:14 - Quantum Computational Advantage
01:48:15 - Many Worlds vs. Complexity
01:54:51 - Psi-Ontic vs. Psi-Epistemic
02:01:37 - Collapsing Tunneling Particles
02:08:48 - Larmor vs. Atto Clocks
02:15:24 - Locality and Information

LINKS MENTIONED:
Aephraim's Website: https://www.physics.utoronto.ca/~aeph...
Aephraim's Papers: https://scholar.google.com/citations?...
Photon Negative Time in Atom Cloud [Paper]: https://arxiv.org/pdf/2409.03680
How Much Time Does a Photon Spend as Atomic Excitation? [Paper]: https://arxiv.org/abs/2310.00432
Measuring Time Atoms Spend in Excited State [Paper]: https://journals.aps.org/prxquantum/a...
Tunneling Atom Time in Barrier [Paper]: https://arxiv.org/abs/1907.13523
Single-Photon Tunneling Time [Paper]: https://journals.aps.org/prl/abstract...
Traversal Time for Tunneling [Paper]: https://journals.aps.org/prl/abstract...
Propagation of a Gaussian Light Pulse [Paper]: https://journals.aps.org/pra/abstract...
Linear Pulse Propagation in Absorbing Medium [Paper]: https://journals.aps.org/prl/abstract...
Eighth Velocity of Light [Paper]: https://pubs.aip.org/aapt/ajp/article...
Attosecond Ionization [Paper]: https://www.science.org/doi/10.1126/s...
Tunneling Optical Pulses Photonic Band Gaps [Paper]: https://attoworld.de/fileadmin/user_u...
Evidence of Negative Time [Article]: https://www.scientificamerican.com/ar...
Light Speed Reduction [Article]: https://www.nature.com/articles/17561
On the Theory of Light and Colors [Paper]: https://www.jstor.org/stable/pdf/1071...
Wave Propagation and Group Velocity [Book]: https://amazon.com/dp/1483253937?tag=...
EPR Paper [Paper]: https://journals.aps.org/pr/abstract/...
Uncertainty Principle: https://en.wikipedia.org/wiki/Uncerta...
QBism [Paper]: https://arxiv.org/abs/1003.5209
More links at https://curtjaimungal.substack.com

Guests do not pay to appear. #science

20 Comments

@TheoriesofEverything Creator 5 months ago Pinned

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@Seehart 5 months ago

Yes, negative times are real. We are living in negative times.

@charlesrackoff9696 5 months ago

At 1:48:58, "Charlie Rackoff" is mentioned in the audio, but "Scott Aaronson" appears in the closed-captioning. (This also happens one time a bit later.) Since I am one of those two people, I felt like mentioning this.

@stanleysokolow 5 months ago

A limerick:
There was a young lady named Bright,
who could travel much faster than light.
She set out one day,
in a relative way,
and returned on the previous night.
--Author unknown

@williamstoertz 1 month ago

At 50:50, I think the important thing to realize is that, what we're actually looking at, in terms of a quantum system, is a subliminal mathematical computing and reckoning system that is not consigned to operate at the "speed of light", but rather instantaneously, in order to balance the overall outcome so that, within the specified unified field domain, it is constrained to produce the outcome that corresponds to defined physical parameters and principles. Thus, we cannot speak of the photon or electron or wave itself during the brief interim period between the input and the outcome; all we can know is what is the overall result, and that this will correspond to specified physical principles.

@AlbaAdventures 5 months ago

On thing I can say about you Curt, you seem to get so many incredible scientists on your show. Very impressive.

@moofymoo 7 days ago

good communicator, i understood more than i thought i will understand.

@danthem2278 5 months ago

Just was at a lecture today from Yakir Ahronov where he derived this exact theory on the blackboard at age 93. What a legend!

@tofo2 5 months ago

One of the few interviews where the explanatory world is not in a Hilbert space.

A person who can yet again imagine.

@ChuckJones-i3p 5 months ago

Have they ever considered either of the following:
1. The substrate itself is capable of handling FTL signals.
2. The device itself is tuned to produce these resonant photons, so the field itself is already in the state desired to produce these resonant photons and that excitation is not remaining confined to the device. It is being transmitted, via waves of course, relatively long before the first "photon" is even fired. Something along these lines is likely leading to the negative time results.

@cameronjack1095 5 months ago

I love listening to Aephraim. He's just so careful and clear in how he describes concepts and how meaningful (or real) they actually might be. Thank you so much Curt. This episode was a cool glass of water to listen to.

@grbradsk 5 months ago

There's a certain pleasure in intellectual talk that is akin to fine wine for those who have such tastes.

@majorshocker2097 5 months ago

Thank you so much for taking the time to record this. This helped my thinking, significantly.

@MusicLover-bp2cc 5 months ago

French astrophysicist (and part-time ufologist) Jean-Pierre Petit talked about negative time many years ago, in fact he talked about it in the 80s based on a conversation he had with a friend that told him an alien told him black holes don't exist, they are openings to a parralel universe where time runs backward...).

Here's some of his more recent published works:
Cancellation of the central singularity of the Schwarzschild solution with natural mass inversion process (2021)
Alternatives to Black Holes: Gravastars and Plugstars (2025)
Mathematical and Geometrical Inconsistency of the Black Hole Model (Part I) (2026)

@videos_not_found 5 months ago (edited)

The poisedness, the balance and the profound knowledge stemming from direct experience is more than impressive, would not be surprisedif he gets a Noble price once we understand negative time better.

@jonlitchfield8888 4 weeks ago

Phenomenal communicator. Thank you.

@architrino 4 months ago

This was a strong example of how foundational physics gets clearer when we separate the measured quantity from the story we attach to it. The “negative time” result does not need to mean time running backward. It can be read as a signed, post-selected clock response: a real experimental number from a carefully defined measurement interaction. The deeper issue is that classically equivalent questions, like delay time and dwell time, can split apart in quantum systems, then sometimes unexpectedly agree again. A good deeper theory should preserve causal front velocity and no-signaling, treat time as the ordering parameter, and derive these signed clock readings from the actual interaction between system, probe, and final record.

@vivianoosthuizen8990 1 month ago

His example of saying he catches the ball before it’s thrown is perfect for explaining how I understand this. It’s necessary to understand that yes the catcher must have a split second of so-called make the thrower throw the ball

@Bob_R0ss_2026 5 months ago

Hey Kurt. Love the way you engage the interviewe in describing the parameters of the subject rather than expecting a viewer to already know the operators. Keep up the outstanding work my friend

@williamstoertz 1 month ago

At 56:40, though we would professionally state that we are not making a claim to know "what's out there", nevertheless, we would have to at least conjecture that there must be some system in the transcendental realm that ensures that the physical laws and constants, including the relationship of cycles and processes in "time", are defined and maintained.