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This episode is about what physics says is there when nobody is looking, including time itself. Jim Al-Khalili, theoretical physicist and Distinguished Professor Emeritus at the University of Surrey, joins to argue that the arrow of time is fundamental. Entropy increases because the arrow already points that way, and... show more
11,958 görüntüleme • 21 gün önce •via X (Twitter)
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Models aren’t reality, and all models are wrong. We should stop pretending otherwise by claiming that this or that “is fundamental”. We can certainly make such assumptions and explore adaptive implications but there is strictly no way of validating anything outside of ourselves and our own phenomenological experience.

What is “time itself”? I submit that it is precisely “flow.” Our conjunction of this flow with fields, and particles, is what physicists are referring to, by “time.”

Don’t see how the arrow of time can be fundamental rather than derived from a low entropy past. Thermodynamics playing a role in finding quantum gravity would suggest that spacetime is not fundamental at all, it emerges from a deeper structure.

The arrow of time is the one that gets me. Almost every law of physics works the same running forwards or backwards, and yet we only ever remember the past. Looking forward to this one.

I’m not sure “increasing disorder” gets us to the bottom of the arrow of time, because disordered already contains a choice of description. Shuffle a deck and we call it disordered because suits and ranks mean something to us, but it has simply moved from one exact configuration to another. Entropy is a precise quantity, “disorder” is an interpretation of what that quantity means. Maybe the deeper asymmetry is not disorder at all, but inheritance. Once something becomes real, it becomes history and gains the authority to constrain what can become real next. The unrealized alternatives do not.

He is right but incomplete. The arrow of time is the direction of causality and correlates with increasing entropy only under the closed-system assumption. Entropy increase is not fundamental but an analytical and experimental artifact of that assumption.

time arrow isn't about time in causality

Mentions Bohm? I am in!! lol will listen at work today

Hooray for Bohmian and mechanics

Nah. Nonsense.

“Arrow of time”? Time = Length Full Stop. ;) Happy hunting!

Curt Jaimungal, please interview physicist, writer and broadcaster, and professor at Arizona State University, Paul Davies. He wrote an iconic book in 2001 titled "How to Build a Time Machine" That would be a fantastic podcast

Even science is part of the dream.

nonsense ... the arrow of time is left open/incomplete .. and this incompleteness is an invite ... an invite for each to compose with time!! and when one does compose with time... there is no entropy.. there is no decay ...

The answer is still 42

These attempts, being still rather immature, are already outdated. Have a look at the pinned post in my profile for the full text of "Universe Topology".

Arrow of time, entropy, Emergent Compressed Vacuum, and a theoretical model culminating in 41 physical quantities with only two eigenvalues and an interlocked overconstrained. Zero Operator Theory. Thank you for the more than 6k downloads in 200 days.

@jimalkhalili If the Universe is unitary, it can be run forwards/backwards, but not changed, like a movie, preventing the Grandfather Paradox, b/c you would grow younger & become unborn. Conversely, irreversible measurements are the equivalent of an "arrow of time" & the 2nd law.

I brake for blocktime.

Imho time being a compact dimension is the only thing that can account for observations. The relationship of charge and chirality geometrically CRIES Klein spinor topology. Time is the (minimum) distance from minima to maxima. But take a lazy path if you like. 1/137 speed

The claim that the arrow of time is fundamental identifies a real weakness in the usual entropy-based explanation, but it risks stopping the explanation one step too early. Saying entropy increases because time already has a preferred direction simply replaces one unexplained asymmetry with another. The deeper question is what physical structure makes processes genuinely directional in the first place. A more complete account would distinguish between an unresolved physical possibility, its lawful realization, and the persistent record produced by that realization. Those stages are not trivially interchangeable: a completed event contains dependencies and records that were not present beforehand. On this view, the thermodynamic arrow is not the cause of irreversibility, but neither does it need to be imposed as a primitive direction of time. It may instead emerge from a more fundamental asymmetry in how physical events become realized and recorded. The Past Hypothesis therefore does appear incomplete if it merely inserts a special low-entropy boundary condition. But declaring the arrow of time fundamental has a similar weakness unless the theory explains what generates that directionality. The real target should be the underlying mechanism from which temporal order, record formation and entropy increase all follow together.

Rate of travel from minima to maxima is our action space.

Time is emergent not fundamental. Same as "space" and consciousness. All ontologically one "stuff" working in unison ONLY configured to the agent....or the agent only configured to the emergence to give a whole. No boundaries. Waves upon waves upon waves.. a mist of a dream.

Well… Beyond any misexplanation or not, you do not merely need the *sub-stance* ,to be present and experience the material essence. You need the *out* of it! Fundamental…? No grounds!

Humans trying to not be humans to see the world. A human is always a human - there's no not-human place to stand. Our science is human science as the science of a hypothetical alien x would be alien x science, as it would impose the structure of cognition. There's no THE science

Correct. My model has said this from the beginning, and now I am interested in what Jim has to say. Also, the gravity in my model upon revision is thermodynamic. Your post came to my feed at exactly the right time. Thank you.

Strongly agree that thermodynamics belongs in the foundations, not as an afterthought. Al-Khalili’s insistence that the arrow of time is fundamental (and that entropy increases because the arrow already points that way) feels right. Thermodynamics is also the more useful comparison with AI systems rather than with consciousness. Consciousness remains the harder and more contested question. Using thermodynamics gives us clearer questions, and more useful answers.

