How is time an illusion?

shavera · 3 months

So let's start with space-like dimensions, since they're more intuitive. What are they? Well they're measurements one can make with a ruler, right? I can point in a direction and say the tv is 3 meters over there, and point in another direction and say the light is 2 meters up there, and so forth. It turns out that all of this pointing and measuring can be simplified to 3 measurements, a measurement up/down, a measurement left/right, and a measurement front/back. 3 rulers, mutually perpendicular will tell me the location of every object in the universe.

But, they only tell us the location relative to our starting position, where the zeros of the rulers are, our "origin" of the coordinate system. And they depend on our choice of what is up and down and left and right and forward and backward in that region. There are some rules about how to define these things of course, they must always be perpendicular, and once you've defined two axes, the third is fixed (ie defining up and right fixes forward). So what happens when we change our coordinate system, by say, rotating it?

Well we start with noting that the distance from the origin is d=sqrt(x² +y² +z² ). Now I rotate my axes in some way, and I get new measures of x and y and z. The rotation takes some of the measurement in x and turns it into some distance in y and z, and y into x and z, and z into x and y. But of course if I calculate d again I will get the exact same answer. Because my rotation didn't change the distance from the origin.

So now let's consider time. Time has some special properties, in that it has a(n apparent?) unidirectional 'flow'. The exact nature of this is the matter of much philosophical debate over the ages, but let's talk physics not philosophy. Physically we notice one important fact about our universe. All observers measure light to travel at c regardless of their relative velocity. And more specifically as observers move relative to each other the way in which they measure distances and times change, they disagree on length along direction of travel, and they disagree with the rates their clocks tick, and they disagree about what events are simultaneous or not. But for this discussion what is most important is that they disagree in a very specific way.

Let's combine measurements on a clock and measurements on a ruler and discuss "events", things that happen at one place at one time. I can denote the location of an event by saying it's at (ct, x, y, z). You can, in all reality, think of c as just a "conversion factor" to get space and time in the same units. Many physicists just work in the convention that c=1 and choose how they measure distance and time appropriately; eg, one could measure time in years, and distances in light-years.

Now let's look at what happens when we measure events between relative observers. Alice is stationary and Bob flies by at some fraction of the speed of light, usually called beta (beta=v/c), but I'll just use b (since I don't feel like looking up how to type a beta right now). We find that there's an important factor called the Lorentz gamma factor and it's defined to be (1-b² )^-1/2 and I'll just call it g for now. Let's further fix Alice's coordinate system such that Bob flies by in the +x direction. Well if we represent an event Alice measures as (ct, x, y, z) we will find Bob measures the event to be (g*ct-g*b*x, g*x-g*b*ct, y, z). This is called the Lorentz transformation. Essentially, you can look at it as a little bit of space acting like some time, and some time acting like some space. You see, the Lorentz transformation is much like a rotation, by taking some space measurement and turning it into a time measurement and time into space, just like a regular rotation turns some position in x into some position in y and z.

But if the Lorentz transformation is a rotation, what distance does it preserve? This is the really true beauty of relativity: s=sqrt(-(ct)² +x² +y² +z² ). You can choose your sign convention to be the other way if you'd like, but what's important to see is the difference in sign between space and time. You can represent all the physics of special relativity by the above convention and saying that total space-time length is preserved between different observers.

So, what's a time-like dimension? It's the thing with the opposite sign from the space-like dimensions when you calculate length in space-time. We live in a universe with 3 space-like dimensions and 1 time-like dimension. To be more specific we call these "extended dimensions" as in they extend to very long distances. There are some ideas of "compact" dimensions within our extended ones such that the total distance you can move along any one of those dimensions is some very very tiny amount (10^-34 m or so).

from here

shavera · 3 months

Science Fiction books, and science-mysticism are not valid sources.

If you have not had an education in relativity kindly refrain from providing erroneous answers to this question.

escheriv · 3 months

Saying "time is an illusion" as a quick throwaway statement is just metaphysical wanking. That's fine if it's in a philosophy course, mind you.

If you're looking for a more science-based explanation though, and considering the subreddit I hope you are, time isn't an illusion. You can quibble about the details when it comes to human perception of time, but time itself is part of spacetime. Time exists, and it's not helpful to write it off as an illusion.

shavera · 3 months

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Neuropinephrine · 3 months

Time is an illusion because it's just a measure of how things change locally. That is relative to your position in the universe, since things in different places change at different rates.

reddit_hack · 3 months

"When forced to summarize the general theory of relativity in one sentence: Time and space and gravitation have no separate existence from matter." - Albert Einstein

bhtitalforces · 3 months

Did your professor elaborate at all? Just saying "time is an illusion" by itself is really meaningless.

hapsham · 3 months

No mention of the theory of "Timeless Physics"? It isn't really a useful theory because it isn't falsifiable, but it is interesting mathematically. Here's a good explanation of the theory:

http://lesswrong.com/lw/qp/timeless_physics/

TL;DR: Consider a universal wavefunction ψ(r, t), where r is the position of everything in the universe and t is time.

Well since r never repeats itself we can eliminate the parameter t, and just have ψ(r). The wavefunction of the universe is a function of the positions of everything in it.

udcstb · 3 months

The "flow" of time may be thought of as an illusion. But as mentioned there are certainly differences between past and future, which can be related to entropy. But you still need time, as a coordinate (preventing that all things happen at once). Also you can measure time intervals, many things are periodic (the sun goes around the sun in 365 times the time the earth needs for a rotation), thus it is certainly a useful concept.

An expert on the field is cosmologist Sean Carroll, he wrote a very good pop science book on the topic ("From Eternity To Here").

Also, his blog: http://blogs.discovermagazine.com/cosmicvariance/

Uberhatkat · 3 months

Time is a real thing which we both experience and which can be measured and studied. You either need to expand on what your professor said or begin to discount what he said. There are neuro-cognitive reasons why our perception of time might change to produce illusion-like effects with regard to time. There are analytical tools and models in relativity which put time in geometric terms to resolve paradoxes, and because we aren't used to thinking of time in geometric terms we (and by we, I mean me) can't really grok it.

None of these really add up to support for the general statement "time is an illusion."

tinkdances · 3 months

People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff.

3 months

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[deleted] · 3 months

I believe you professor is speaking of Time dilation.

If you were standing close to an object that had unimaginable mass and other people were standing far away from that object, you would perceive the people far away as moving in fast motion while they would perceive you as moving in slow motion. However, both you and the people far away would not feel any effects of being in slow or fast motion.

nomdeanon · 3 months

My favorite explanation is, paraphrased as follows: Everything we experience at a given moment is the simultaneous arrival of information from various times in the past. Light from a tree and light from a distant star arrive at our eyes simultaneously, but they contain information about the state of those objects in the past. The tree, nanoseconds ago; the star, millions of years ago. All of our present experiences are the echoes of past events.

This is an interesting and relevant read.

Firesinis · 3 months

Only your professor can tell you exactly what he did mean by that statement, but there are some useful interpretations of this sentence.

One of them comes from the distinction we make on time versus space. The way we intuitively perceive this duality is akin to the classical interpretation, i.e., time and space possess different natures (you measure one with a ruler and the other with a clock). Space is relative, i.e., if you're driving from San Francisco to Sacramento you'll tell me that Vallejo comes before Vacaville, but for someone taking the opposite trip Vacaville comes first. Time, on the other hand, seems to be absolute, i.e., if I see an event A and then later see and event B, there's no way someone else could have seen event B before event A. Except that this perception is false.

When Poincaré and Lorentz tried to make sense of the Michelson-Morley experiment, they came to the conclusion that when an object is in motion, it actually becomes a bit shorter in length in the direction of the motion than when you measure it standing still. Furthermore, the measurement of time as taken by you and another person in motion in relation to you aren't exactly the same. Because of that, Einstein realized it didn't make sense to measure lengths with a ruler, as the length may change depending on speed, neither time with a clock, as the measurements may be off. Since Maxwell's theory and the Michelson-Morley experiment seemed to indicate that this was the case, he went by the assumption that the velocity of light is the same for any observer free from the action of external forces, no matter their speed in relation to one another.

Thus he proposed to measure both lengths and time intervals using a method of boucing light rays off things, as this wouldn't deliver skewed results depending on the speed of the observer, and formulated a new theory of mechanics based on that. Space and time became less different, as both are now measured by the same method (in relativity you can even measure space in seconds or time in meters in terms of the speed of light). As a consequence of this theory, we discover that it is indeed possible that one observer watches a sequence of events A then B happening and a different observer watches the event B happen before event A. In truth, like space, and contrary to our intuition, time is relative. You can take this fact as a possible interpretation that time, as we see it intuitively, is an illusion.

ilovetpb · 3 months

Time exists, just not the way we imagine it to. We think of time as universal; it is not. It is localized to every point in the Universe. What we see is our present and the past of all other points. On grand scales, that is obvious - when we look at the edge of the Universe, we are looking at it as it was billions of years ago, because it look light that long to get to us. So we are seeing its past, while it's true present is forever hidden from us by distance. The same thing holds true no matter how small of a scale you go to. Light takes time to travel, so the light of anything outside of you took some amount of time to get to you. So when you look at a person a few feet away, you are technically seeing them as they were an imperceptibly short time ago in the past.

[Edit] Grammar

raethe · 3 months

I think what he meant is that time, in a positivist or empirical sense, does not exist.

That is, we perceive times at different rates (due to general relativity), and perceive time only relative to the rate at which we experience our sun. Therefore, our concept of time is still loosely based on physical reality, although it is nonetheless subjective experience (as with everything).

Er, well that's my understanding.

iamthejamesmay · 3 months

Illusion, huh? Time makes for some fun reading, and gives an interesting perspective on our world-view.
Quantum mechanics suggests an interesting treatment of time. For example, it's not always possible to answer "whether an event has occurred" and "when did this event occur" simultaneously. From a relativity point of view, you could also say that gravitational time dilation shows that the measured passing of time for an observer close to a gravitational mass is slower relative to a more distant observer. Also, relative velocity time dilation shows that the local time rate measurement (your perspective) will be faster relative to that of an observable measurement (ie moving clock) with constant motion with respect to your reference frame.

If you'd like some interesting reading, may I recommend "The Fabric of the Cosmos: Space, Time, and the Texture of Reality" by Brian Greene? If you have time to spare for reading...

Edit: Rephrased for clarity.

joeatwork86 · 3 months

Related question (and possibly stupid);

How do the base functions of programmed cell death operate when one begins to experience time dialation. Does it still occur at what one perceives to be the normal rate, even to an outside observer? Surely, regardless of speed of travel a function that just happens as time passes at no particular rate is affected, right?

s_racer2003 · 3 months

Here's the way I think of it. Time is a dimension, just like length, width, and height. The whole of it exists all at once just like your whole body exists at once. However, as three dimensional creatures, our brain is only capable of perceiving three dimensions at a time and so we merely experience three dimensional cross sections of the fourth dimension.

Now step down a dimension and pretend you're a two dimensional creature, only capable of perceiving length and width, height is now what you perceive as time, as you pass through 2d cross sections of a 3d object. For a visual of this, watch this video: http://www.youtube.com/watch?v=o-8zS-qyDOM

So... As a two dimensional creature, you're seeing these weird shapes that fluctuate and pop into and out of existence as time passes, pretty weird, right? But in reality, everything you're seeing as "time" passes isn't popping into and out of existence or even changing shape, the whole body is, and always was there, being a 2d creature you just can't perceive it as a whole.

Similarly, we as humans exist in a 4th dimension, the whole of which exists at any given "time" and we, as three dimensional creatures, are just passing through.

Njugguh · 3 months

I think he meant that the way we "notice" time is an illusion.

Take the classic "Its been an hour already?" from a child that has been playing to the "ITS ONLY BEEN AN HOUR?" of the man watching paint dry. Some people in high danged scenarios have felt like time slowed down to a drawl, making a minute feel like an hour or something of the sort.

Time itself is not an illusion, the way we notice it is, such is the nature of a illusion. " The condition of being deceived by a false perception or belief." Note the false perception, this is the nature of a Illusion.

TeCuervo · 3 months

What kind of professor is he? The statement could be valid depending on the class.

CrabbyMonday · 3 months

PBS just had a documentary on this http://video.pbs.org/video/2164065493/

[deleted] · 3 months

One of the ancient philosophers had an argument where he said something along the lines of 'just because your arm is in a new position, dosent mean it moved'.

I think he meant that the universe could be said to be a state machine. Particle A is at a position X. Particle A is now at position X+1. What exactly happened there? No 'movement' is going on at either frame of reference, yet this particle is in another position.

Its like an onion, Shrek. At the top we have collections of properties (an object). Underneath this is a layer of 'functions'. These functions could be called illusions, because they dont really exist, they just operate on stuff. Movement() is one of these functions. This function called Movement() gives rise to yet another layer : because we have movement, we have time. And thats why time is an illusion, albeit a very persistent one.

Infuriated · 3 months

There is no actual "time", only space and states. Time is our attempt to measure aspects of space and states.

PlutoniumLeak · 3 months

Something that bothers me: can you consider time as infinitely existing? Since time is part of space-time, and the universe will continue changing forever (expanding), can you assume that time will have a meaning until +infinity? And if we go back to -infinity, did time exist for infinity before the big bang?

3 months

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[deleted] · 3 months

Time is a dimension in which you are constantly moving.

[deleted] · 3 months

The best section on time that I've ever read and what you're probably looking for is in the book "Fabric of the Cosmos" by Brian Greene. It's a section called "Does time flow? The Frozen River."

Here, you can read the entire chapter here:

The Frozen River

Specifically, pay attention to these sections:

'The Persistent Illusion of Past, Present, and Future' and 'Experience and the Flow of Time.'

Here is a small subsection:

"In this way of thinking, events, regardless of when they happen from any particular perspective, just are. They all exist. They eternally occupy their particular point in spacetime. There is no flow. If you were having a great time at the stroke of midnight on New Year's Eve, 1999, you still are, since that is just one immutable location in spacetime. It is tough to accept this description, since our worldview so forcefully distinguishes between past, present, and future. But if we stare intently at this familiar temporal scheme and confront it with the cold hard facts of modern physics, its only place of refuge seems to lie within the human mind."

Also, if you like Richard Feynman, he has a really good piece that you can read here:

The Distinction of Past and Future

AzyWyler · 3 months

Time is an illusion because we have memory and recognize that as the past and can think ahead and recognize that as the future, but there isn't rewind or fast forward because there's no line we follow, it's just moment to moment, (essentially one continuous moment). We picked out our time based on our perception of how things revolve around us in the universe, but really everything is just floating around space, which has it's own skewed perspective.

TheWarpedOne · 3 months

Time is the byproduct of perception and memory.

Honztastic · 3 months

"Time is an illusion" is one of those bullshit shock-phrases that get thrown around in physics and science to try and make you forget some misheard fact.

Time is not an illusion. It's being used in this sense in that humans perceive time in a very fixed way. Even the fastest and most distant from Earth any human has or can be at the moment only changed our perception of the flow of time by microseconds. Imperceptible.

The truth is time is relative. It reacts differently based on speed, location and the relative differences between two points. Time isn't an illusion at all. We just only see it in a very narrow scope. To perceptibly change it requires technology we don't really have.

PuffingTom · 3 months

Simple answer: watch the Through the Wormhole episode that's about time.

ar92 · 3 months

I have a feeling he was referring to the "motion" of time. People assume that things, in three dimensions, "move" through time like a river. However, the reality is that space things have time properties, and vice-versa. The particulars of this scientific concept are enumerated in some detail on this thread.

There are also philosophical and religious arguments for time being an illusion. My favorite is from the Compass of Zen:

http://www.buddhasvillage.com/teachings/time.htm

"Everyone thinks that this is extremely difficult teaching, something beyond their reach or experience. How can things appear and disappear, and yet there is, originally, even in this constantly moving world, no appearing and disappearing? A student once asked me, 'The Mahaparinirvana-sutra seems very confusing. Everything is always moving. And yet everything is not moving? I don't understand this Buddhism . . .' But there is a very easy way to understand this: Sometime you go to a movie. You see an action movie about a good man and a bad man--lots of fighting, cars moving very fast, and explosions all over the place. Everything is always moving very quickly. Our daily lives have this quality: everything is constantly moving, coming and going, nonstop. It seems like there is no stillness-place. But this movie is really only a very long strip of film. In one second, there are something like fourteen frames. Each frame is a separate piece of action. But in each frame, nothing is moving. Everything is completely still. Each frame, one by one, is a complete picture. In each frame, nothing ever comes or goes, or appears or disappears. Each frame is complete stillness. The film projector moves the frames very quickly, and all of these frames run past the lens very fast, so the action on-screen seems to happen nonstop. There is no break in the movement of things. But actually when you take this strip of film and hold it up to the light with your hands, there is nothing moving at all. Each frame is complete. Each moment is completely not-moving action.

"Our minds and the whole universe are like that. This world is impermanent. Everything is always changing, changing, changing, moving, moving, moving, nonstop. Even one second of our lives seems full of so much movement and change in this world that we see. But your mind--right now--is like a lens whose shutter speed is one divided by infinite time. We call that moment-mind. If you attain that mind, then this whole world's movement stops. From moment to moment you can see this world completely stop. Stop. Stop. Stop. Stop. Stop. Like the film, you perceive every frame--this moment--which is infinitely still and complete. In the frame, nothing is moving. There is no time, and nothing appears or disappears in that box. But this movie projector--your thinking mind--is always moving, around and around and around, so you experience this world as constantly moving and you constantly experience change, which is impermanence. You lose moment-mind by following your conceptual thinking, believing that it is real."

Another way of looking at it is that the mind invents the linear progression of time, at least in the way that we perceive it, from its use of memory and prediction. Imagine what time would feel like if you had neither long term nor short term memory, so that after you perceive something, you had no memory of it. Would you perceive yourself moving through time?

micman52 · 3 months

I've always pictured the passing of time as a ball, representing a planet, on top of a ruler, measuring time, and as the ball turns it moves the ruler underneath it creating the illusion of time. Things are in constant motion and always changing. We witness this change and interpret it as time passing. Alternately if your a theists you can imagine God pulling on the ruler making the ball turn above it.

madrigar · 3 months

You're not off. Your professor is full of shit.

TenebrousLuck · 3 months

The easiest way to answer this is as such:

Time, length and motion are relative quantities.

fireball_73 · 3 months

In the words of Douglas Adams: "Time is an illusion; lunchtime doubly so"

ramalang · 3 months

Time is an artifact of the way our mind creates a linear reality out of observed experience. Processes exist, but they always take place irrevocably in this very moment. Time is a construct our minds invent to keep track.

reddittidder · 3 months

Time, as we know it, is a biological construct used by biological entities to keep track of processes. Other than that, time and entropy are the same thing. At instant 1, you have universe in state 1, at instant i, you have universe in state i.

Science Fiction books, and science-mysticism are not valid sources.

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