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In the fundamental physics of the world, there is neither space nor time (nautil.us)
164 points by dnetesn 6 months ago | hide | past | web | favorite | 79 comments

I just finished reading Rovelli's book "The Order of Time." The article is the last chapter, where the author summarizes the results of the "journey" of the book.

I recommend the book, it was an enjoyable read. The author is able to explain clearly concepts that I had struggled to understand before.

Throughout the book there are a many references to philosophical ideas and to the history of science, in some cases quite emotional. This being the last chapter, is quite heavy on them. However, I found them quite useful and interesting as a tool to break from preconceived notions of time.

> we have imagined the existence of "eternity," a strange world outside of time that we would like to be inhabited by gods, by a God, or by immortal souls

If fundamentally there is no time, then fundamentally there is only eternity.

In my view, whatever we learn at a fundamental level, we know there is time. Thinking of an analogy, we know that a smooth piece of metal is smooth, and smoothness is "real," even if the metal is made of atoms, and the atoms are made of quarks and leptons. Similarly, I've seen pictures where they magnify somebody's nose a thousand times, and it looks gross, but the person has a perfectly nice nose.

We experience periodic phenomena, such as the cycles of days and years, the moon, our heartbeats, and our pace when walking. Even if some of these are not utterly uniform, the general observation that there are so many days in a year, etc., are objective in the sense that they are experienced by everybody. A concept of time could be formed by associating events with days, and noticing that some of the timelines formed in this way always point in the same direction. For instance, birth is to the left of death on this timeline, never the other way around. Now you've got a clock -- the sun -- and an arrow of time -- birth to death.

I describe a "theory of time" to myself in this way because I imagine that primitive people could form such a view, and find it useful enough to keep. For instance, knowing when it's time to plant, or when certain kinds of fish are likely to be found in a particular river, would improve the survival of a primitive group. At least, it would improve my survival in such a situation.

So I think, even if time and space break down on cosmic or microscopic scales, they are satisfactorily real.

Yes, I suspect (without further proof ATM) that this is the main reason for this quest for timelessness which Sean Carrol (cited in another comment) finds so perplexing [0]. Eternity has traditionally and in various ways been associated with (especially) monotheism. Same with infinity (of which eternity is a sort of subset).

A much simpler but perhaps more tedious way out of this apparent rational loophole for religions would be accept it. Religion may keep this final straw of rationality: we don't and can't know everything given a (probably) infinite universe. Religion is not best understood as a theory of physics anyway, but rather as a study of history, society and mind.

[0] http://www.preposterousuniverse.com/blog/2009/06/17/timeless...

The universe IS completely unknown, and forever will be. It is like a sandbox.

As Alan Watts put it with his mischievous sense of humor:

"Science is the art of prediction"

Talking about religion, Christianity used to refer to this, then it lost its way. See eg.


> Talking about religion, Christianity used to refer to this, then it lost its way.

This is still true, to an extent, in the Christian Orthodox world, Pseudo-Dionysius the Areopagite is still reguarded as one of the main “intellectual stars” (so to speak) of the Christian Orthodox thought. As for the “lost way” that you mention, I think that that change started in the West once the Reformartion took off and people wanted to “be sure” that they’ll get to live the eternal life. Here in Eastern Europe people do not think in absolute terms about life after death, as in nobody actually believes you can “earn” your way into Heaven, it all resides in God’s Will which is not possible for us to know. There’s also that New Testament parable of a guy asking Jesus at some point with whom of his wives will he be married in Heaven (the guy had been previously married to a different woman) and Jesus basically answered that that is a stupid question as nobody knows anything about Heaven.

Just a nitpick, but the example the man gives is of a hypothetical woman who over time had seven husbands --- just one at a time of course, but one husband would die and then she would get married again. The question was, which one will be her eternal husband?

> Jesus basically answered that that is a stupid question as nobody knows anything about Heaven.

Jesus said it was an ignorant question, yes, "You are in error because you do not know the Scriptures or the power of God." But he didn't say nobody knows. He said that she won't be married: "At the resurrection people will neither marry nor be given in marriage; they will be like the angels in heaven" (Matthew 22:29).

Thanks for the correction, I had last read that almost 20 years ago :)

Actually, he was addressing the unbelief in a resurrection by the sect of the Sadducees, as well as the simplistic idea underlying their question that life after death will be a direct translation of life before. The Sadducees were basically trying to make a clever intellectual trap.

That, too, but I think that the point that there’s futile for us to want to know the “details” of the after-life is also a valid one in reguards of this parable.

What loophole are you talking about? As much as I try, I cannot see any connection whatsoever between religion and concepts of infinity and eternity in physics.

Is the idea that anything that science currently cannot explain must be connected to religion? That would be a fallacy.

This is summed up in Wittgenstein's Tractatus as: "If we take eternity to mean not infinite temporal duration but timelessness, then eternal life belongs to those who live in the present."

If there is no time, then nobody (or everyone) lives in the present.

The thing is, the observer is the one determining what is fundamental.

If the God, sitting on his throne in eternity, determines the fundamental to be eternity, then from that framed perspective, there is only eternity.

If the man, sitting on his porcelain throne in the bathroom, determines the fundamental to be a here-and-now framed by a past and future, then from that perspective, that is the truth.

It is all illusion, including eternity. There are only frames we may peer at infinity through.

It might not be clear from the last chapter, but the book doesn't claim that time doesn't exist.

To paraphrase (but use the same example because it is funny): time doesn't appear at the fundamental concepts in physics. Cats also don't appear at the fundamental level of physics. But cats exist. Time (and our perception of it) must appear somewhere as a emergent feature.

Time does appear in fundamental concepts in physics?

In relativity it is particularly important. Timelike dimensions are treated differently in the metric, with a +1 or -1 depending on taste, ie

ds^2 = c dt^2 - dx_1^2 - dx_2^2 - dx_3^2,

so I don't think its quite fair to say that it doesn't "appear". In quantum physics unitary evolution is invertible. Decoherence is not reversible (I mean interaction - loss of entanglement).

Maybe these theories have been biased by our perception, but they are good (but incomplete) models.

Time in relativity bears almost no resemblance to the common definition of time.

1) There is no such thing as simultaneous. There is no universal now. 2) Time does not proceed at a constant rate 3) Time proceeds at different speeds for different observers.

So time as relativity defines it is certainly true. But time as people conceive it is fundamentally different. At best, common sense time is a profoundly special case that can't imagine the general case. And at worst, a nonsensical concept evolution gave us. Perhaps so erroneous it might be valid to say it does not exist.

Humans never travel at significant fractions of the speed of light with regards to other nearby things, so relativistic effects are rather hard to observe in person.

It's the same how Newtonian Mechanics is a really good approximation (and still widely used, too), and because everything around us happens to obey it very closely, it is more intuitive. The difference between what Newton's equations and Einstein's equations predict for most planetary orbits is very slight.

If time is a dimension not constraining to fundamental physics, there could be higher dimensions where more fundamental things manifest, as a way to explain it, as does string theory. If there are higher dimensions, what's to say we can't actually experience more fundamental realities through consciousness traveling. If time passes slow by in an emergency or a profoundly concentrated moment, humans if definable as the human consciousness could be traveling at relativistic speeds and not knowing. Elegantly, it's not matter doing that since matter wouldn't survive the trip.

> Time does appear in fundamental concepts in physics?

Sure, in that it is a component of a spacetime, and events happen at different points in spacetime.

How you slice up spacetime into space and time is essentially up to you. That is what Rovelli is talking about: it's not that there is no time, but rather that slicing up a spacetime in any fashion will still not produce a global "now".

Setting down a system of constant pseudo-Cartesian coordinates:

> ds^2 = c dt^2 - dx_1^2 - dx_2^2 - dx_3^2

(nit: c^2)

versus some other set of coordinates on the shame spacetime doesn't change a pair of infinitesimally close field-values on field filling that spacetime, nor their relative positions -- it just changes how one describes the latter.

We can still chose a now and describe the difference between now-1, now, now+1 as operations within the "now" spacelike hypersurface. However, does this justify a view that now+1 is undetermined at now-1? What operations happen where in the same volume of spacetime for an observer using a different slicing?

The exact metric is less interesting here than that the spacetime is Lorentzian; that feature is what constrains slicing choices within a causal cone, or alternatively provides the diffeomorphism invariance under arbitrary time parametrisation.

"Timelessness" doesn't get rid of that sort of ordering: a relativistic field's field-values at different points in spacetime depend on it, however one wants to formalize that dependency, e.g. they must transform under representations of the Poincaré group, Poincaré invariance must be implemented unitarily on the state space, or the action must be Poincaré-invariant.

What timelessness does challenge is some notions about operations within any spacelike hypersurface.

> not produce a global "now"

I thought that was just already accepted as part of relativity that there is no global now (I feel like you are saying there is no global interial reference frame?).

I really mean that there is this more general concept of time which looks like what humans perceive as "time" locally. The ordinary human perception of time is obviously not quite the whole picture. Our lives are just slow enough that we don't notice relativistic effects. We are just fooled into thinking its ordered linearly, but there is a more general picture.

But saying that there is no "time" because it doesn't quite match our intuitions is wrong. Its just that we have to expand our thinking.

Further, I think relativity still has an "arrow of time". Thermodynamic quantities can transform under reps of Poincare group - "Relativistic Thermodynamics" is certainly a thing. Landau and Lifshitz has a few chapters on it I believe. So the idea of time "passing" (entropy increasing at least carries over.

> Further, I think relativity still has an "arrow of time". Thermodynamic quantities can transform under reps of Poincare group - "Relativistic Thermodynamics" is certainly a thing. Landau and Lifshitz has a few chapters on it I believe. So the idea of time "passing" (entropy increasing at least carries over.

I'd be grateful if you could show me where in §27 (PDF pages 94-96) of http://people.physics.tamu.edu/kcolletti1/classes/fall15/sta... you get any of that from.

> "Relativistic Thermodynamics" is certainly a thing

Is it a thing which really deals with an arrow of time, or is it a thing which lets one study the temperature of a moving object, the temperature of an object in a gravitational field [Tolman], or the temperature of an object in which individual velocities (of fluid elements or particles) are large [Israel & Stewart]?

Actually, yes that book doesn't mention that entropy is Lorentz invariant, but I think there are papers on it [0].

However it doesn't actually look like they reach a decisive conclusion - it is still for debate.

[0] http://iopscience.iop.org/article/10.1088/0305-4470/38/13/00... [1] https://arxiv.org/pdf/1802.07650.pdf

This seems to be going off into the weeds.

I think what you might be trying to argue is that in vacuum spacetime with a horizon there is a Gibbons-Hawking temperature T_{GH}. A Eulerian observer with a purely timelike worldline could measure T_{GH} at various points along its worldline. In de Sitter space the temperature is proportional to the Hubble parameter H.

Unfortunately, there is afaik no consistent or complete microphysical description of the Gibbons-Hawking effect. Additionally, it's so small that the presence of a relic matter field (like the cosmic microwave background) completely swamps it by many orders of magnitude (for H_0 it's 30 orders). So T_{GH}, purely general-relativistic, does not seem like a useful arrow of time in our universe until the latest of epochs maybe.

Look instead to the Boltzmann entropy of the matter; we can simply set a low-entropy boundary condition somewhere in spacetime, and then we do not even need to have an expanding universe to have higher entropy in spacetime at increasing distance from that boundary. Alternatively, we could go through some hoops to try to remove the boundary, as Hartle & Hawking among others.

Carroll has a list of relevant slides at https://www.slideshare.net/seanmcarroll/what-we-dont-know-ab...

None of this has much if any contact with relativistic thermodynamics. In cosmology we are almost always deliberately considering a family of privileged observers and ignoring the others (even though they exist). Our defined cosmological observers see matter (incl. radiation and any horizon radiation) as homogeneous and isotropic. Any expansion or contraction of space is an adiabatic process. \Lambda is nearly zero, but still sufficient to generate enormous spacetime curvature (the purely timelike worldlines of our observers are not parallel).

Finally, calculating in the cosmological frame is a convenience, nothing more.

That all depends on how fundamental you want to be. Atomic physics used to be considered fundamental, and then we discovered something more fundamental.

We've already reached the point at which reductionism breaks down in physics: you can smoothly transform between electrons and magnetic monopoles by varying the fine structure parameter, so which one is made of which? The answer is "Whichever is more convenient at the moment." [0]

There are already nascent theories attempting to simplify quantum field theory, that could be considered fundamental, which are based entirely on geometric and combinatoric concepts where time isn't implicit in the definition of the theory (because it's just manipulations of polytopes) but where time emerges as a feature instead of being an assumption. [1][2]

[0]: https://www.youtube.com/watch?v=NZ-ElsvYKyo&index=2&list=PL3...

[1]: https://www.youtube.com/watch?v=q4Dj8fq30sk

[2]: https://www.youtube.com/watch?v=l87oICmHT2E

The EFThedron looks interesting, I have to check that out.

>but the book doesn't claim that time doesn't exist.

Why are people so hung up on the question whether 'x' exist or not without actually having a proper idea of what it mean for something to "exist"?

It's surpisingly hard to define what it means for something to "exist".

Nice post!

Put it this way: clearly time appears to exist, at first glance. Even the timelessness crowd somehow manages to submit their essay competition entries by the deadline, and finish their Bloggingheads dialogues within an hour.

Thanks for that link. I also think he has a point.

I'm starting to think that there's a point where physics becomes almost as much a study of our own mind as it is of the external world.

Much of the ancient esoteric wisdom taught that we were all of one, a mind, a singularity if you will.

I think this bit of truth was purposely hidden, as Einstein himself alluded to, by a dark cabal, and has coincidentally been rediscovered albeit as a secular institution primarily through a diefication of the scientific process.

Some of our still very early study of Quantum Mechanics points right to this matrix reality we experience.

However uncomfortable that may be.

That has been said about mathematics, many times. But our minds are merely a reflection (often distorted, for that matter) of what's outside.

It's rare to read from such a sober-minded yet deeply philosophical world view. He basically outlines to most essential things in the universe - gravity and uncertainty. Everything else is a means to quantify the world to make it more understandable to us. At least quantum mechanics show that uncertainty is quantifiable to an extent with the means we already have. I'm not even sure whether gravity is as un-quantifiable as it seems to be. That's what scientific minds ought to figure out.

> Perhaps, ultimately, the emotional dimension of time is not the film of mist that prevents us from apprehending the nature of time objectively.

Perhaps the emotion of time is precisely what time is for us.

The application of sufficient Time and Space can solve almost any problem. If 2 groups are in conflict, putting 10 light years and 100 million calendar years between them often removes the ability to conflict.

We do have an easy way of doubting space/time real existence in form of dreams. In dream we feel sensation, experience space and time and it feels so real till the dream last. You can experience long hours or someone can experience years [0] within few seconds/minutes of a dream.

Hence to take a next big leap in understanding the cosmos we as a society will eventually need to be bold enough and open for other ideas regarding the truth of objective reality we experience in waking state. Could it be just like a dream, though a grand one, being projected by some cosmic consciousness of which we are inseparable part? Not some divine form I'm proposing here, but a formless pure consciousness awareness that each of us possess and experience it in silence. Eastern mystical traditions have long been investigating these alternative ideas and countless individuals have testified experiencing such super conscious state confirming the idea.

Maybe so, but he also says ...

> To this blurring is added quantum indeterminacy. The ignorance that follows from this determines the existence of a particular variable—thermal time—and of an entropy that quantifies our uncertainty.

... and ...

> The variable “time” is one of many variables that describe the world. It is one of the variables of the gravitational field: At our scale, we do not register quantum fluctuations, hence it is possible to think of spacetime as determined. Hence we can think of spacetime as being as rigid as a table. This table has dimensions: the one that we call space, and the one along which entropy grows, called time. In our everyday life we move at low speeds in relation to the speed of light and so we do not perceive the discrepancies between the different proper times of different clocks, and the differences in speed at which time passes at different distances from a mass are too small for us to distinguish.

But whatever, I am moved to read his book :)

I'm not sure about entropy arguments for explaining the direction of time. On Earth, the entropy doesn't change much over time, thanks to a constant stream of low-entropy in the form of radiation from the Sun. Overall, the system is increasing in entropy. But why do we, on Earth, need to care what happens in the Sun? We could just as well go backwards in time as forwards, but influencing the past seems to be extremely difficult (just try kicking a football backwards in time).

I believe the same reasoning applies here on Earth. Imagine a pile of ash (high entropy) assembling into a copy of Shakespeare (low entropy), compared with the reverse.

You can get isolated pockets of low entropy that appear (e.g. the human brain), but I think I've heard it described that there has to be thermodynamic pathways leading to such states. We understand parts of these pathways, but there are important aspects still left to figure out.

And of course, as you mentioned, the system as a whole is still increasing in entropy the entire time.

Imagine a mountain where height inversely correlates with entropy. The summit represents the very low entropy state of the big bang, and the second law of thermodynamics is an enormous steam-roller that is currently in the process of flattening the entire mountain. Then, us humans are simply pebbles that have been shaken loose and are dancing in the foothills. In a few billion or trillion or quadrillion years, all the dancing pebbles will have been crushed into a fine dust and spread across a perfectly flat, unchanging plane.

But they will have danced beautifully in the many years before.

> Imagine a pile of ash (high entropy) assembling into a copy of Shakespeare (low entropy), compared with the reverse.

Imagine the soil 50 years before Shakespeare forming the food he ate and the trees which became the paper he wrote on. It seems a lot like ash (soil) did organize itself to a lower entropy collection (with a lot of help from an external energy pool).

True! However, the seed that became the tree is very low entropy. One of my favorite marvels about life is how it is an unbroken chain that goes back 4 billion years (with countless branching, truncated ends, of course).

Also, many seeds didn't make it, so there is a bit of survivor bias looking at the one seed that did become a tree.

> very low entropy state of the big bang

This always confuses me a bit, why do we consider the first instants of the universe maximally ordered? A near homogeneous sea of per-subatomic particles seems less ordered than the later universe of galaxies and stars and hydrogen atoms with cold areas in between.

I tried to understand Roger Penrose's arguments about this in his book "Cycles of Time". I admit that I really struggled! But the idea seems to be that the initial state of the universe is very unusual compared with the rest of eternity and is essentially 1 vs nothing - and then differentiation instantaneously occurs through some physical process and immediately the universe can only be described in a complex way. The universe moved from undifferentiated high energy to and extremely complex high energy and then falls down from there back to flat.

One point that seems not to feature in these debates is that this is all (physics) fundamentally subject to the constraints of language (maths) and cognition (human), we choose to describe things in a way that appears useful to us, but these judgements and perceptions are filtered by how we understand things. We are squashy and small and it is quite silly to imagine we really are thinking about these processes in an objectively meaningful way.

"This always confuses me a bit, why do we consider the first instants of the universe maximally ordered?"

Note what happens as the universe proceeds from that time period to its heat death; hydrogen is burned into higher elements until everything is cold iron floating in space. In this case, it might be best just to look at the available energy as a proxy for entropy; a universe full of hydrogen is a low-entropy universe that still has a lot of useful energy that can be extracted, whereas in the heat death of the universe, there's nothing left. No fusion can be done. No fission can be done. No chemical energy floating around that you can use. Just balls of iron in maximally thermalized environments, all maxed out in entropy.

As I've occasionally said in other contexts, right now the universe is young and awash in energy in many forms; our energy problem is a difficulty in figuring out the right way to metaphorically cup our hands and capture it all in the ways we want to use it. We're literally billions of years away from an actual lack of energy, because the universe started out with a lot of it.

> why do we consider the first instants of the universe maximally ordered

Much higher ordering is straightforward and is essentially just statmech:

1. Run the expansion history of the universe backwards: there are fewer degrees of freedom as the universe collapses into the big bang.

2. Run the expansion history of the universe forwards: vacuum is very high entropy (you can swap a bit of vacuum from here with a bit of vacuum from there and not tell the difference), and there is much more of it at late epochs. Assuming no-hair, black holes are also very high entropy, and there are more of them at later epochs.

Maximal ordering makes some assumptions about quantum gravity with respect to (1):

> A near homogeneous sea of per-subatomic particles

... would expand in such a way that the universe would remain (nearly) perfectly smooth at all epochs.

We can start with the idea that there is an inherent uncertainty to the energy of empty-of-particles space. At later epochs, this uncertainty is small; but in the very early universe it is large. With slow expansion, the uncertainties average out over short distances. However, during cosmic inflation, the uncertainties are stretched and only average out on much larger length scales. The "new" vacuum produced as inflation continues has prorgressively less energy uncertainty, but are "within" the streched uncertainties from earlier. By the time inflation ends, random regions of all sizes contain subregions of overdense and underdense vacuum energy.

Cosmic inflation precedes the hot big bang: it is the chaotic arrangement of vacuum energy at different densities that decays into matter (in the most general sense of matter) proportional to the vacuum energy density. More matter arises in the overdense regions than in the underdense regions. As expansion progresses, gravitation takes over: light finds it easier to leave underdense regions than overdense regions, and that (the gravitational redshift, and the spectrum being highly similar to blackbody radiation) means underdense regions look slightly hotter than average regions, and overdense regions look slightly colder. Gravitation also works on the rest of matter too, not just light: matter flows from underdense regions to denser regions; matter flows to overdense regions from sparser regions. Finally, overly-overdense regions will heat up and emit light and kick hot particles out. The balances between the vacuum energy fluctuations before the hot big bang and the gravitation-vs-radiation flow of matter afterwards are encoded in the cosmic microwave background.

> less ordered than the universe of galaxies and stars and hydrogen atoms with cold areas in between

The mostly-empty areas in between have much higher entropy, and those areas are even bigger (and emptier) at later times. The galaxies and stars and hydrogen atoms are not more numerous at later times: matter dilutes away with expansion.

Nevertheless, time is supposed to be a local phenomenon. If we have a region of space where entropy is decreasing (balanced by a larger increase elsewhere), would you not then expect "time" to flow in the opposite direction in this local space? Would it be possible to set up such an experiment?

Our physical world is space and time, but in the maths of physics we lose track of it. ;-)

Some books about QM include big warning about "Mathematics is not Physics!" at very beginning, but nobody reads it.

Chapter 2

The Formulation of Quantum Mechanics


Basic Theoretical Concepts

Every physical theory involves some basic physical concepts, a mathemati- cal formalism, and set of correspondence rules which map the physical concepts onto the mathematical objects that represent them. The correspondence rules are first used to express a physical problem in mathematical terms. Once the mathematical version of the problem is formulated, it may be solved by purely mathematical techniques that need not have any physical interpretation. The formal solution is then translated back into the physical world by means of the correspondence rules.

Sometimes this mapping between physical and mathematical objects is so obvious that we need not think about it. In classical mechanics the position of a particle (physical concept) is mapped onto a real number or a set of real numbers (mathematical concept). Although the notion of a real number in pure mathematics is not trivial, this correspondence rule can be grasped intuitively by most people, without any risk of confusion. The mathematical formalism of quantum mechanics is much more abstract and less intuitive than that of classical mechanics. The world does not appear to be made up of Hermi- tian operators and infinite-dimensional state vectors, and we must give careful and explicit attention to the correspondence rules that relate the abstract mathematical formalism to observable reality.

Certainly makes sense if the holographic principle is correct, and our universe of experience is encoded in the entropic 2D planar surface of a blackhole.

What I don't understand about this idea: What is with all the other black holes? Are the holographic universes of each black hole the same? Do they encode the other black holes in their surface?

The idea is that we are inside (or on the surface of, same thing) a black hole whose event horizon encompasses the entire universe (observed and unobserved). The black holes we can see in our universe would then be children black holes (or great-great-grandchildren, who knows how far down the holographic rabbit hole we are).

There was a time when it seemed that science worked within the constraints of epistemology, but now it seems to be radically reshaping that domain.

Makes sense. Everything can be encoded in a bitstring, which is a single number, and a single number has no sense of space and time.

One of the most beautiful and simultaneously terroristic traits of our existence is that of binary computational equivalence.

Of course, binary as a notion is simply a set of relative measurements of the peaks and troughs of a wave at a specific time and scale, therefore we may deduce the ultimate excitation of all, what appears as this large number, is an analog, encompasses everything, and our reality a carefully crafted series of reductions from this source.

Wonderful and awe inspiringly scary that we may even consider such a thing of brilliance.

Many things can be approximately represented by a bitstring.

Perhaps the difference between an approximation and a complete encoding should be emphasised more forcefully on CS courses.

There are infinite recursive processes which can't be encoded in a bitstring. You can only put the results you got so far into one. To get more digits you will have to evaluate the function.

Not everything, but perhaps a description of most things.

If reality is finite and discrete, then it is everything.

On the other hand, if there are non computable processes at work in reality, then not everything.

Strangely, Julian Barbour is never mentioned.

In which case it's obviously broken from the get go.

Article: Spacetime is an illusion! Time isn't real! Reality: The details of time diverge a bit from common understanding. The author has an emotional reaction to this.

Who else dislikes this sort of pop-science writing? It seems to care more about evoking some mystical and philosophical idea of the universe than effectively communicating the science.

I have a strong distaste for science popularizations that misrepresent results to make things seem more fun or exciting or whatever—but this isn't that. This is more a presentation of a physicist's worldview, giving some background on the physics which made it that way.

> Reality: The details of time diverge a bit from common understanding.

I think you may be underestimating the divergence a bit. The author is hardly alone in finding general relativity's implications on time to be of profound philosophical importance, for instance.

>Who else dislikes this sort of pop-science writing?

I love pop science writing. The thing is that this easy imagination helps a lot of people access hitherto unknowable principles of science. If you are science oriented or enquiry minded but do not have a background in the extreme detail required to access the specific subject/topic, you would have very likely never learnt anything about it given the arcane approach road to it. Popular science writing makes those spaces accessible, marks the roads, explains the possibilities and allows one to think through those abstractions. Then if you are sufficiently interested, you actually get into the hairy details of the actual science. But for most of us who are actually just traveling and understanding, this sort of writing gives us a grip of the "lay of the land."

I look at such writing as maps of knowledge, not the actual thing, but sufficiently detailed and made interesting to give people a sense of where they are. It's a jungle gym for the thinking mind.

I'm sure for someone who has devoted his career to understanding spacetime, Rovelli's enthusiasm for the subject at least borders mysticism. The science of quantum gravity is wide open.

I devoted decades of my life to it and I never associated it with the borderline mysticism present in this article. It's all vectors, tensors, fields and operators, and the data which support certain models or provide avenues to yet more questions by exposing deficiencies and gaps. There's nothing deeper about it than that, except what we choose to apply for our own emotional satisfaction (which isn't unimportant, but certainly shouldn't be mistaken for truth in the world of physics).

>It seems to care more about evoking some mystical and philosophical idea of the universe

What is wrong about mystical, philosophical idea of the universe? I like mystical, philosophical idea of the universe.

Nothing wrong about it per se. Just don't try to mask it as or "soften" the principles of science.

> "soften" the principles of science.

How can it soften the principles of science, if it does not masquerade as science. Can you point me in the article where it tries to pass some mysticism or philosophy as science?

"Carlo Rovelli is a theoretical physicist and writer"

Nothing wrong, just not science.

Everything was "not science" before it became "science". So what is your point?

...if a thing is not a science, it is not necessarily bad. For example, love is not a science. So, if something is said not to be a science, it does not mean that there is something wrong with it; it just means that it is not a science.

--R. Feynman

Did quoting R.Feynman was part of your plan? Because I don't see no other point for your original comment other than to eventually quote R.Feynman.

A: I like x

B: I don't like x

A: Why?

B: Because it is not science

A: Why is that bad?

B: It is not. Because R.Feynman said blah blah blah...

A: ??

You may find this a little more to your liking:


I despise it, and it seems to have become all that Aeon is capable of. If I wanted to hear what a stoned Physics 101 student thought, I’d ask them. Good science isn’t necessarily sexy, it may not make for profitable clickbait, but it’s very rewarding.

@Westoncb: Philosophy of science is about as useful to scientists as ornithology is to birds.

Hmm... It's not from Aeon, and the author is a practicing theoretical physicist who also does work in history and philosophy of science—so about as well-suited to the topic at hand as you could get.

> The difference between past and future does not exist in the elementary equations that govern events in the world.

Such bullshit. QM does not govern events. The probability function encodes everything about how it's governed. QM does not speak to that at all. Unitarity assumes the probability function remains correct. That doesn't mean the probability function does not have any inputs which can be influenced by change. Dumb article

Lol downvoters don't even know the Copenhagen interpretation is deeply flawed and never learned to use their words

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