Why the Flow of Time Is an Illusion

http://nautil.us/issue/71/flow/why-the-flow-of-time-is-an-illusion

by dnetesn • 7 years ago

147 191 7 years ago

rc_mob• 7 years ago

Time is just a measurement that we haven’t quite nailed down the definition of yet.

GuB-42• 7 years ago

We have a very precise definition of time: a second is "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom". It is used in a lot of physical equations which are very accurate at describing the universe as we observe it.

There are some philosophical questions regarding time. Questions about the arrow of time, entropy, causality, etc... For instance we may have trouble relating time and entropy, but it doesn't mean both of these concept are not well defined by themselves.

lm284692• 7 years ago

We have a very precise definition of time
a second is

Well that's a very precise definition of a second (unit of time), but not of time itself.

Nasrudith• 7 years ago

Of course relativity also complicates things with time as well. Whose second? Even if you have two different caesium-133 atoms monitored, one on earth and one on a satellite they won't rise at the same rate although both are defined the same.

I guess the real "illusion" would be that if there is truly nothing to be a frame of reference there is nothing for time to "flow" relative to.

neom• 7 years ago

The World Science Festival has a slew of episodes on the flow and illusion of time: https://www.youtube.com/user/worldsciencefestival/search?que...

One of the thoughts I've been having recently about "human time" is the effect that the observance of changing seasons and the circle of life over an evolutionary period has had on how humans think about things like time and permanence. Unfortunately I don't have anything particularly insightful to say other than I've been wondering about it. ¯\_(ツ)_/¯

737373737311• 7 years ago

The word 'illusion' should be removed from every dictionary. It's one completely unspecific, indeterminate and misleading word and most subjects or patterns of discourse in which it appears have the same properties.

The title of this post also reminds me of https://en.wikipedia.org/wiki/E-Prime

Just searching for "* is an illusion" returns

- consciousness - choice - spacetime - the world - physical reality - certainty - memories

It makes me feel disgusted.

RugnirViking• 7 years ago

The word is used to describe large and unknowable concepts as well as optical tricks?

Its possible for a word to have more than one meaning.

fouronnes3• 7 years ago

illusion - noun, an instance of a wrong or misinterpreted perception of a sensory experience.

737373737311• 7 years ago

A misinterpretation always requires a context, or direction. Its use implies the existence of a 'true interpretation'. The word illusion doesn't give either, it just signifies that there is one. But then I have to ask, how can a subjective experience be something truly or falsely interpreted?

n4r9• 7 years ago

The title of this post also reminds me of https://en.wikipedia.org/wiki/E-Prime

I don't understand what the title has to do with avoiding forms of "to be"? It contains the word "is".

737373737311• 7 years ago

"Is" is (heh) one of the forms of "to be" and can signify many different things: https://en.wikipedia.org/wiki/E-Prime#Different_functions_of...

lisper2• 7 years ago

"Illusion" is perfectly well defined: it is a perception that does not correspond to any objective reality outside your brain.

simonh2• 7 years ago

The problem is, that just punts the issue down to what is considered objective reality. If that's in contention, as in this specific case, then referring to things as illusory can be ambiguous. I happen to disagree with the comment you are responding to, but I do accept that the term illusion is often used ambiguously, especially in relation to notions of objective and subjective reality.

Falling33• 7 years ago

No, that's the definition of a hallucination. Illusions are misinterpretation's of objective reality by the brain (and I agree that's not a well-defined thing).

simonh2• 7 years ago

On it's own in a sentence perhaps yes, but in the context of an in-depth interview in which the author explains exactly what they mean by it I think it's ok. We just need to be aware that many of the words we use can have a variety of meanings, but once that meaning is clear it's useful to be able to continue using the words on their own.

empath753• 7 years ago

An illusion is simply a state where the model of the world created by the mind differs from the world as it exists.

In a pedantic sense, it’s all an illusion, but there are particular illusions where the difference is readily demonstrable — when the magician shows what was hidden in his sleeves, as it were.

In some sense, most of science is exposing the method of various tricks our own consciousness plays on us. We want to know, for example, why metal appears to be shiny— when the phenomenon we’re studying ‘shininess’ only exists in our own minds. There’s no innate ‘shiny’ property in nature.

Time is one of those things where there is a persistent feeling that it must be illusory (which is to say, something created by our minds), but we’re not quite sure exactly in what way or how to prove it.

vinceguidry7• 7 years ago

Illusion can be tricky to understand, but not impossible. It means that the referent is not the same as the representation. When something isn't an illusion, it means the referent is the same as the representation. We have different words for different kinds of illusion. I can show you an actual, physical chair, or a picture of a chair. The first is not an illusion, while the second is.

You watch a real television show on a real television. The television is designed to create visual illusions of real things. But the television is itself real. The show is a dramatic rendering, an illusion, of real-life situations.

So there's three elements needed to make illusion. A referent, a representation, and a type.

Consciousness is real, but its contents are illusory, thought represents things that are not those things.

davebryand• 7 years ago

An enlightened yogi, Hindi, or Buddhist would say that the physical chair is also an illusion.

latexr• 7 years ago

I can show you an actual, physical chair, or a picture of a chair. The first is not an illusion, while the second is.

If the picture of the chair is so good that one mistakes it for a real chair, yes, otherwise I wouldn’t classify it as an illusion.

On a tangential note, people enjoying this discussion might enjoy the beginning of chapter two[1] (or even the whole book) of Scott McCloud’s “Understanding Comics”[2].

[1] https://rhetoricsuperhero.files.wordpress.com/2013/09/mcclou...

[2] https://en.wikipedia.org/wiki/Understanding_Comics

barking• 7 years ago

What would magicians do without illusions, mere tricks, that's what. Shame on you.

737373737311• 7 years ago

The association of the word with mystery in particular doesn't help to bring clarity in discussions with a scientific context. If I said "semiconductors are an illusion", "programming is an illusion" etc. it doesn't contribute any information. It just confuses.

EGreg3• 7 years ago

The map is not the territory.

To say something is an illusion means that something is a map that doesn’t match the territory.

But it assumes there IS a territory to map! While often simultaneously denying its existence. That’s the contradiction.

criddell• 7 years ago

Words aren't used because they are in the dictionary, they are in the dictionary because they are used.

hunta20973• 7 years ago

I live by a couple of (vaguely related) principles:

a) Consciousness is just your brain trying to anticipate the future.

b) Your brain compresses (normalises?) repetition in memories. So even if day to day events happen at normal speed, the years seem to fly by when you reflect on them. If your life seems to be flying-by then maybe you need more novelty.

zikzak• 7 years ago

This is true. You also need to take into account how each day is a smaller and smaller percentage of your life which might be why kids think summer vacation lasts forever but it flys by for parents.

Falling33• 7 years ago

This explanation comes up frequently in these discussions. It makes a certain amount of sense on its face, but is there any evidence that this actually affects our perception of time?

egjerlow22• 7 years ago

Why would your brain need consciousness to anticipate the future? A computer, which has no consciousness, would be able to do the same.

TeMPOraL11• 7 years ago

Consciousness is how the algorithm feels from inside.

kaffeemitsahne• 7 years ago

A computer, which has no consciousness

[citation needed]

Falling33• 7 years ago

Who said our brains _needed_ consciousness to anticipate the future? The only claim I've seen is that it's (part of?) the particular mechanism our brains happen to use. This is akin to asking why birds need to flap their wings to fly when we have airplanes that can fly with fixed wings.

dqpb4• 7 years ago

I would argue that consciousnes is just the feedback loop of the brain sensing itself

737373737311• 7 years ago

Because consciousness is unitary (see https://en.wikipedia.org/wiki/Integrated_information_theory), it would be intuitive if all consciously accessible information converged at a single physical location. In this theory, simple feed-forward networks aren't conscious.

From what I've read about ego-death, it doesn't seem necessary to consciously sense the self-concept, which would be self-awareness.

Dirlewanger2• 7 years ago

Other animals are alive and conscious, but I'm pretty sure they don't have a sense of self.

EGreg3• 7 years ago

Wow. This comment may change my life

jbattle• 7 years ago

Thinking of your brain as a story-fitting machine also explains a lot. Everything we perceive our brain tries to fit into a narrative structure

david-cako3• 7 years ago

Very Jungian/Jordan Peterson-esque thought that I think makes a lot of sense in understanding ourselves. Also reminds me of the book The Righteous Mind.

We exist to measure ourselves in an ocean of complexity, with infinite recursion in self-awareness.

ZeroFries3• 7 years ago

Sorry to be blunt, but that's not a very good response to the Hard Problem of Consciousness. Unfeeling matter becomes feeling when its changes are related to the future? How does that work?

737373737311• 7 years ago

From the Integrated Information Theory link below:

Intrinsic existence: To account for the intrinsic existence of experience, a system constituted of elements in a state must exist intrinsically (be actual): specifically, in order to exist, it must have cause-effect power, as there is no point in assuming that something exists if nothing can make a difference to it, or if it cannot make a difference to anything. Moreover, to exist from its own intrinsic perspective, independent of external observers, a system of elements in a state must have cause-effect power upon itself, independent of extrinsic factors. Cause-effect power can be established by considering a cause-effect space with an axis for every possible state of the system in the past (causes) and future (effects).

specialist• 7 years ago

"your brain trying to anticipate the future"

I got this worldview from Hawkins & Blakeslee's book On Intelligence. https://en.wikipedia.org/wiki/On_Intelligence

One side effect is it changed my strategy (coping mechanisms) for reality, truth, beliefs from Popperian to who has the best prediction engines. This has allowed me to disengage from contemporary rhetoric (culture wars) about science (eg creationism), allowing me to better relate to certain friends and family.

david-cako3• 7 years ago

I also often consider that each day I wake up as an observer to a linked list of time, that exists independently of me yet to me "only" in my mind. As our eyes and ears are sensitive to fine vibration around us, so it seems that consciousness is sensitive to time.

lm284692• 7 years ago

If you zoom out far enough everything is just your brain tripping balls trying to process electric signals from faulty/limited sensors.

egjerlow22• 7 years ago

What exactly is 'tripping balls' if it is not comprised of electrical signals? Saying consciousness is 'just' this thing or another is, in my mind, making trivial the most profound riddle in all of existence.

bookofjoe• 7 years ago

"Time doesn't flow, we flow."—Michael Crichton

jatsign2• 7 years ago

Even a skeptic philosopher, who would say most things can't be proven beyond the self, would probably agree that one of the things we have direct experience of is change.

JdeBP3• 7 years ago

"How can I tell that the past isn't a fiction designed to account for the discrepancy between my immediate physical sensations and my state of mind?" -- The Man In The Shack, The Hitch-Hiker's Guide To The Galaxy

jatsign2• 7 years ago

True, but that's why I said "probably agree". You can be a solipsist and disagree with the existence of time, but that doesn't seem to be a very useful philosophy.

slackfan• 7 years ago

Considering that the first post isn't "Lunchtime is doubly so" consider your geek cards revoked.

stronglikedan• 7 years ago

is?

Circuits• 7 years ago

As a coworker of mine would say: "A watched pothead never toils." I have always found it amusing when people talk about time's existence. It has always seemed like a ruler or a measuring stick; t = d/v, to me. Some people disagree as to it's existence but I think perhaps the problem isn't with our concept of time but with our definitions of existence.

jasim• 7 years ago

When his great Italian friend Michele Besso died, Einstein wrote a moving letter to Michele’s sister: ‘Michele has left this strange world a little before me. This means nothing. People like us, who believe in physics, know that the distinction made between past, present and future is nothing more than a persistent, stubborn illusion.’

... ...

Many times in the past we have realized that it is our immediate intuitions that are imprecise: if we had kept to these we would still believe that the Earth is flat and that it is orbited by the sun.

Our intuitions have developed on the basis of our limited experience. When we look a little further ahead we discover that the world is not as it appears to us: the Earth is round, and in Cape Town their feet are up and their heads are down.

To trust immediate intuitions rather than collective examination that is rational, careful and intelligent is not wisdom: it is the presumption of an old man who refuses to believe that the great world outside his village is any different from the one which he has always known.

-- Seven Brief Lessons on Physics, Carlo Rovelli

state_less• 7 years ago

"Dr. Manhattan: There is no future. There is no past. Do you see? Time is simultaneous, an intricately structured jewel that humans insist on viewing one edge at a time, when the whole design is visible in every facet." -Alan Moore, Watchmen

To me, this idea looks like we have a set of measurements of things (X, Y, Z, T) and a function F that maps from the set of measurements to a future set of measurements. You can generate the future from the past. You could take the view that all these measurements exist, and we just can't see them (well) because we are only able to jump from Tnow to F(Tnow). In other words, we exist in one place and one time at a time.

wwarner• 7 years ago

It's interesting, because usually people/physicists that space is the emergent thing, and time is the fundamental dimension. I'm also glad that people are trying to reduce the number of dimensions rather than adding to them.

KingFelix• 7 years ago

I mentioned this in a previous discussion, some really interesting fringe research going in. Retrocausation

https://experiment.com/projects/are-we-catching-photons-trav...

JdeBP3• 7 years ago

For an interesting book on the subject of time in the philosophy of physics, see Huw Price's Time's Arrow and Archimedes' Point. It does a fairly good job of laying out what the problems are.

* http://prce.hu/w/TAAP.html

cobbzilla5• 7 years ago

I find this quote fascinating:

"What I think that means is there is no holy era of time. It emerged. If, in the distant future, we find ourselves in a universe where all the stars have burned out, and all the black holes have evaporated, and all the radiation has been diluted by the dark energy that expanded our universe, and all we have is some very cold bath of photons here and there—basically thermal equilibrium; de Sitter space, as we call it—there will be no sense of time anymore. There will nothing you can do to determine whether time is going one way or the other. Time will then have un-emerged again. It will be like the poem, This is the way the world ends / Not with a bang but a whimper."

I am not a cosmologist, but if all of space reached thermal equilibrium, if space does have any mass (perhaps a tiny amount from the dark energy it contains?), and the entire universe is essentially one uniform mass, wouldn't that mass then collapse upon itself, in a kind of big bounce?

If that is true, then time never really ends, it just "slows down" a lot (not much can happen, and not terribly quickly) until the next sparkup, whereupon time speeds up dramatically (inflationary theory).

negamax• 7 years ago

Read The Last Question if you haven't

737373737311• 7 years ago

And watch this: Timelapse of the future - A Journey to the End of Time: https://www.youtube.com/watch?v=uD4izuDMUQA

cobbzilla5• 7 years ago

I love that story, alas it doesn't give me any additional insight on these questions.

Plus, the state of the art has progressed much since then. I'm curious what the latest science says about when the universe is only empty space in thermal equilibrium, would the space itself have any mass, and would that mass be self-attractive? Would there be an even distribution of particles that don't decay (proton?), or if all particles decay, then an even distribution of energy, which also has mass?

ljcn• 7 years ago

I am not a cosmologist, but if all of space reached thermal equilibrium, if space does have any mass (perhaps a tiny amount from the dark energy it contains?), and the entire universe is essentially one uniform mass, wouldn't that mass then collapse upon itself, in a kind of big bounce?

Nor am I, but as long as the universe keeps expanding and everything keeps flying apart the average density will probably continue to decrease and gravity will be too weak to cause a collapse.

Or are you saying dark energy (intrinsic to space itself) would eventually dominate and concentrate?

cobbzilla5• 7 years ago

Dark energy would simply accelerate the asymptotic approach to equilibrium by spreading everything out. When everything is evenly spread out and in thermal equilibrium, the aggregate effect of gravity could take over, if the mass/energy of the universe was truly uniformly distributed. Or this is my armchair/idiot idea anyway.

mannykannot• 7 years ago

That quote also shows how difficult it is to even discuss the idea without invoking the notion of a flow from a past to a future.

Science provides both a way of calculating what is going on, and also, apparently, explanations (up to the limits of our knowledge) for what happens. To eliminate the notion of time's flow from discussions of physics, would we have to abandon the concept of causality from our explanations?

hopler• 7 years ago

Yes, causality is one of the ways of defining Time.

https://en.m.wikipedia.org/wiki/Arrow_of_time

klank3• 7 years ago

if ... the entire universe is essentially one uniform mass, wouldn't that mass then collapse upon itself, in a kind of big bounce?

de Sitter space is a vacuum solution for Einstein's field equations.

What this means is that the stress-energy tensor is basically "canceled out" everywhere by the uniform energy distribution. That means no point in spacetime experiences any field influence. That means no gravity, that means no collapse, just stasis.

adamisom• 7 years ago

So the universe would be "de Sitting"

cobbzilla5• 7 years ago

Is it not the case that energy has mass? Why wouldn’t this be equivalent to a uniform mass distribution?

raattgift2• 7 years ago

de Sitter space is a vacuum solution for Einstein's field equations.

Yes, an exact solution.

What this means is that the stress-energy tensor is basically canceled out" everywhere by the uniform energy distribution

No, it means that the stress-energy tensor is zero at every point in the whole spacetime. There is no matter to source any curvature; the curvature is specified by the theoretician writing down the vacuum solution.

In Lorentzian 4-dimensional vacuum de Sitter spacetime ("dS" below) there is no useful concept of energy anywhere. The parameter \Lambda is incorporated directly into the Einstein curvature tensor and so is interpreted geometrically. One would have to perturb the dS vacuum in order to have a useful interpretation of \Lambda as a source of gravitational energy.

Vacuum solutions can be useful in understanding physical systems in which gravitation is important. For example, one can add non-zero stress-energy by hand and use perturbation theory to study the consequences rigorously. Alternatively, one can "cut out" parts of a vacuum solution and work with the rest which closely resembles a physical system (such as deep space far from the matter in and around galaxies). As the expansion of the universe dilutes away the matter contributing to a non-zero stress-energy tensor, our universe will resemble the sparser parts of a de Sitter spacetime. However, from our perspective (i.e. with data in our sky) there are much better approximations at various scales than de Sitter spacetime perturbed by matter fields: there is a lot of obviously non-zero stress-energy under our feet, lighting up our sky day and night, and causing heat to flow from one place to another.

That means no gravity

There can be extremely strong spacetime curvature in de Sitter space!

In general we can time-orient dS: in one direction objects which only interact gravitationally and do not generate significant stress-energy will always converge, in the other they will always diverge, depending on the value of the \Lambda parameter, which is always positive for dS. If \Lambda is large, all such objects leave the others' causal cones much more quickly than they could, even in principle, in flat spacetime.

If we perturb dS with a dense ball of nonrelativistic (i.e., slowly-moving) dust that feels only the gravitational interaction, the dust will tend to collapse if \Lambda is sufficiently small, and will locally approximate a Lemaître-Tolman-Bondi (LTB) collapsing dust metric, which in turn resembles a perturbation of vacuum Schwarzschild or Kerr (which are eternal black hole models; there is no matter to collapse).

A scattering of such collapsing dust-balls with significant gaps between them has been studied by a number of relativists as a family of "swiss-cheese" cosmologies very similar to the one developed by Einstein & Strauss in 1945, who represented the balls of dust as already-collapsed vacuum Schwarzschild solutions, calling them "holes" in the "cheese" of the surrounding expanding spacetime. The Einstein-Strauss-de Sitter model approximated some features of our universe at intermediate ranges, but has since been superseded by the the Friedmann-Lemaître-Robertson-Walker (FLRW) model of the modern standard model of cosmology that among other things has representations of nonzero stress-energy that the vacuum Einstein & Strauss model did not, and which better matches observables in our sky than models that added more realistic matter fields to Einstein & Strauss vacuum.

One feature of Einstein-Strauss-de Sitter style expanding swiss-cheese models is that a small "test" amount of sparse low-mass nonrelativistic dust scattered in the LTB "holes" will stay confined within the hole while the hole separates from everything else. However, an identical test dust scattered in the "cheese" part well outside of holes will never find its way into a hole. Ultimately the former test dust will converge while the latter will diverge.

We can get highly similar results by perturbing the FLRW model. (The observable universe is well approximated by an almost FLRW model in which there are primordial density fluctuations: over-dense areas collapse gravitationally, comparably to the matter in the "holes" of a non-vacuum Einstein-Strauss-de Sitter universe.)

Locally in all these cases, what we have are the tensor fields contributing to the Einstein Field Equations, and general covariance. We can talk about the values of these tensors at any given point (and its neighbourhood), but General Relativity does not lend itself to universal definitions of energy or even energy-density. We can reduce the tensors by using gauge fixing and other techniques, and "demote" the cosmological constant in FLRW or in dS into an energy. (That's really all Dark Energy is in the standard cosmology). In such a gauge we can talk about the work matter interactions (e.g. the electromagnetic interaction) does "against" dark energy. However, the real physics are in the tensors, and applying coordinates and selecting particular observers, while often able to make things much easier to calculate, can be highly misleading too.

The idea that the cosmological constant is "cancelled" out by matter-matter gravitational interactions (and electromagnetic and nuclear interactions) is a statement that the geometrical nature of the cosmological constant is "demoted" into an extremely weak force field, and leads to all sorts of statements that work in that "demotion" context but not generally. Typical statements are that the solar system is expanding, or the galaxy or cluster is expanding, because of the tiny local force on matter by dark energy.

It is better to retreat to "swiss-cheese" and say that the geometry of our solar system is not well-approximated by expanding metrics like dS or expanding Robertson-Walker, and that consequently it is a better fit to observations that in our "hole" (which the matter of our solar system, galaxy and cluster sources) the cosmological constant simply vanishes.

Better still would be to advance to inhomogeneous metrics, but those are a subject of research beyond the scope of this comment.

Finally, your last paragraph can also be read as a request to be directed to the concept of the Jeans Instability in the Expanding Universe. If in the very early universe there was truly uniform and dense distribution of stress-energy, the slightest perturbations would magnify, leading to structure formation. As I wrote above primordial fluctuations of an otherwise FLRW model approximates modern cosmological observations very well. (One could alternatively introduce dissipation, quantum uncertainties, and so forth, as a source of gravitational Jeans Instability causing the collapse or fragmentation of a uniform distribution of stress-energy).

barberousse• 7 years ago

This is strangely approaching Nietzsche's notion of Eternal Return of the Same with the caveat that he additionally speculated that if particles and their configurations are finite, then moments in lived experience necessarily repeat themselves "at some point". This to him was the most gargantuan challenge to the Christian moral tradition since this eliminates any notion of Providence as well as the more general moral notion of "You could've done otherwise" since there's no value to considering timelines, not even from a "Best Possible World of All Worlds" sense.

lurquer• 7 years ago

that if particles and their configurations are finite, then moments in lived experience necessarily repeat themselves

I don't know much about Nietzsche, but this statement does not seem correct. One can have infinite configurations of a finite number of particles. The only way a finite number of particles would imply finite configurations would be (a) space is finite, and (b) space is not continuous. That is, if you imagine the universe as composed of discrete slots in which particles must exist, and the number of slots is finite, then his idea makes sense. But, is there a reason to think this?

obastani3• 7 years ago

I'm not an expert, but I don't think that quote is quite right. There is still a notion of time, there is just no notion of a direction of time. For example, if you go deep into empty space, then one patch of space looks just like the next one. That doesn't mean there is no longer a physical concept of space. Similarly, just because one point in time doesn't look very different from the next, doesn't mean that there isn't a notion of time.

The main point of thermodynamic time is to describe the idea that time appears to be moving forward. According to fundamental physics, as far as we can tell, time is symmetric (with a few caveats). So going forward in time should look similar to going backwards in time, just like going to the left in deep space is the same as going to the right. But the fact that we are in a pocket of high entropy means that time has an apparent direction.

supergarfield3• 7 years ago

Speaking of this, does anyone know of an explanation for why the direction in spacetime in which entropy decreases is parallel to the time dimension (the one with a different sign in the relativistic metric) of spacetime?

Maybe I'm missing something, but I've never seen a link made between the two.

aassddffasdf• 7 years ago

We are in a pocket of high order/ low entropy (not high entropy).

xondono• 7 years ago

I think it’s quite the stretch.

By the same token, if I let my coffee thermo reach thermal equilibrium and don’t touch it, can I claim I’ve built a machine that stops time?

noselasd• 7 years ago

No, the rest of the universe could still effect that coffee externally. A universe at thermal equilibrium would encompass everything (which naturally also means there could not be anyone or anything around to measure anything either)

ASalazarMX• 7 years ago

That same quote confuses me. If there are no events to measure time, why does that mean that time stopped? Can't it keep flowing just as space keeps expanding regardless of measurement? More so, photon decay is not completely ruled out yet, so events could keep happening in that cold photon bath.

frenchy2• 7 years ago

It has to do with what time means. A coloiquial understanding of time has almost everything to with the way our mind and our memories work.

Our mind and memories won't be of much use at the end of the universe, so we have to depend on a more scientific definition. The best scientific way of describing and measuring time outside of our minds basically comes down to measuring systems as they increase entropy. As the universe ages, and these systems approach maximum entropy, the ability to measure time, and the ability to describe in any concrete way what time means, becomes increasingly difficult.

DiffEq• 7 years ago

Here is the crux. Time IS motion. We measure this motion of objects relative to one another by comparing their motion to a standard set of things in motion called a clock. There is nothing else to time except that; but it is real, as real as anything, it is not an illusion.

klank3• 7 years ago

[time] is real, as real as anything, it is not an illusion.

Now the arrow of time on the other hand...

empath753• 7 years ago

No clocks, no time, right?

sridca2• 7 years ago

Yes, it is the sense of time moving that is an illusion; Time itself is a fact, and can be measured.

monkeydreams• 7 years ago

Time IS motion.

Relatively speaking, yes.

There is nothing else to time except that; but it is real, as real as anything, it is not an illusion.

The article isn't claiming time is an illusion, only our perception of it flowing.

ppod• 7 years ago

Imagine a ball rolling down a huge basin. Very deep, ball gets a terminal velocity, rolls down at constant speed. Then the basin shallows, and finally the ball reaches the bottom. From the ball's point of view, "downnwardness", an ineluctable constant, has ceased to exist.

sridca2• 7 years ago

there will be no sense of time anymore [...] This is the way the world ends

If there is no sense of time why does the world "end"?

If that is true, then time never really ends, it just "slows down" a lot (not much can happen, and not terribly quickly) until the next sparkup, whereupon time speeds up dramatically (inflationary theory).

Time slowing down or speeding up is still a "sense of time". Moreover time slowing down or speeding up is a human perception, and not a fact of the universe.

pontifier• 7 years ago

There is a fascinating video that I saw a couple of years ago about conformal cyclic cosmology.

https://youtu.be/sM47acQ7pEQ

I heard something about this theory as a whole falling out of favor, but many of the ideas presented are terribly interesting.

nikolasavic• 7 years ago

The Order of Time by Carlo Rovelli (https://www.amazon.com/Order-Time-Carlo-Rovelli/dp/073521610...) is an amazing and eye opening book on the topic of time. Carlo, a theoretical physicist who specializes in quantum gravity, slowly peels back the layers of the conceptual onion to get to some pretty strange fundamental truths about time.

As a side note, the Audible book is read by Benedict Cumberbach and is a delightful listen.

jiveturkey• 7 years ago

This book is a MUST READ imho. I heard him pitching the book on KQED Forum, he seems quite a pleasant, amiable fellow.

Books like this deserve a re-read at least once. Now I know to do the audible for round 2 in a few years.

loblollyboy• 7 years ago

Whatever time is, our favorite way to 'pass' it is by generate entropy. Chemistry explains inorganic things, those inorganic things become increasingly complex, eventually able to reproduce somehow, so you look to biology for explanation. You get evolutionary biology which might kind of explain how we came to be (super-self aware beings, capable of perceiving things, like time for example, or creating the internet to share ideas, or cars to commute). Then social/behavioral sciences attempt to explain us specifically. But even more fundamental than that first step (chemistry) is physics and math. And physics and math tell us that we are moving to a state of more entropy. Sometimes it feels like this is the best explanation for why we behave the way we do (driving to jobs we hate to do nothing important, making nuclear bombs, etc.).

End result is we're fked!

everdev• 7 years ago

I was really impressed by this 4d toys video: https://youtu.be/0t4aKJuKP0Q

Now what if time is an illusion and similar to the video objects in life simply appear to be bouncing in and out of our 3d realm? That would look a lot like time.

But if we could see in 4d, we'd see that they're not really coming or going and could see all of their possible states at once.

It might be like being able to see an entire movie all at once rather than frame by frame.

z2• 7 years ago

"All time is all time. It does not change. It does not lend itself to warnings or explanations. It simply is. Take it moment by moment, and you will find that we are all, as I've said before, bugs in amber." -Kurt Vonnegut, Slaughterhouse-Five

gtirloni• 7 years ago

I love these discussions, they make my brain hurt in a good way. However, I've trouble applying them to daily life. Is there something we should change in ourselves because of these new insights?

hjanssen• 7 years ago

I don't think you really have to apply these things to your daily life. It is merely a question of _why_ is it that you feel time in your daily life like you do. It's as much of a question of philsophy as it is a question of physics.

Dirlewanger2• 7 years ago

I treat it as very base: be glad that we are who we are, that we can ponder these types of questions, and that it's OK that we may never get any hints, let alone answers, to these questions. Feynman has a good answer to something similar to this in one of those interviews from the 80s; he was perfectly okay with not understanding everything about the universe.

jelliclesfarm• 7 years ago

(Not-a-Physics person)Question: If time isn’t linear, can we have perpetual motion machines?

o_nate• 7 years ago

I liked the example of water spilling onto the floor. I was trying to explain this point to my 7-year old the other day. As crazy as it sounds, the laws of physics don't say that the water couldn't jump off the floor and back into the bottle. The laws of physics are equations and equations are equally true if you reverse the left and right sides. In terms of the equations, that water in the bottle equals the water on the floor (along with the increase in heat energy and other effects), so there's no fundamental physical reason you can't go from one to the other. The reason why you don't ever see it is because it is astronomically less probable to happen in reverse.

cairo_x• 7 years ago

How easy is it for physicists to mistake their models for reality? Equations are ways of representing reality. They are not reality. They are literally abstractions. Yes, it's another way of seeing and thinking about a thing, but it is not the thing... at all. Like a description of 4d space. Isn't a thing in reality, it is an abstraction. The only things that are not abstractions WRT time are movement and matter. Period. When ever you start freezeframing and creating integrations (4d view of time), then you've crossed into the world of the abstract and the non-existent.

Why the Flow of Time Is an Illusion

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