What proof do we have that TIME exists?

[Homesick345]

When we "measure" time, we are obeserving movement, really. Or aren't we? Is there a physics theory where time existence is questionned? why do we need time? & what would be the alternative? What woudl be a universe without time?

 

[Octavianus]

If you and a friend agree to move your bodies to the same place, meet each other, and then move your bodies back to your respective homes is it enough to agree on the place of the meeting?

 

[petm1]

Time is the measure of existence as viewed by an observer.

 

[zhermes]

'Time' is the name for an observed property of the universe. 'Time' wasn't proposed as a theory that could be falsified, its a pure observation---around which extensive theoretical work has been formed.

Time is a fourth dimension of change/freedom ('movement' as you accurately put it), that behaves fundamentally different from the standard 3D people think of. Why time is different is quite a question in theoretical physics that---to my knowledge---people are only really starting to look at, for instance Sean Carroll at CalTech is very interested in the nature of time.

All I know is from popular articles which suggest that in some/many string theories time needn't have been so different, or have exhibited the characteristics it does.

 

[Chalnoth]

Time is a model which has proven very useful in understanding how our universe behaves.

 

[alexg]

Time is what keeps everything from happening at once. And space is what keeps it all from happening to me. - John Wheeler

 

[steve watson]

When we "measure" time, we are obeserving movement, really. Or aren't we? Is there a physics theory where time existence is questionned? why do we need time? & what would be the alternative? What woudl be a universe without time?

"Time" is not a "thing", like a planet, or dog, or grain of sand, or atom, are "things". "Time", like an "inch", "yard", "meter", "fathom", etc., etc., etc., is a measurement. "Time" is what we call this measurement. (We could have called it anything, and we do in different languages). Like an "inch", "yard", etc., etc., etc., "time" it is a man-made construct rooted in reality devised to measure change, i.e., season to season, day to day, minute to minute, heartbeat to hearbeat, etc., etc., etc.

The notion of "time" is valid and rooted in reality, e.g., the Earth's full revolution around the sun is both observable and predictable; we call this full revolution a "year"-our measurement of how long this takes, a man-made construct firmly rooted in reality. Whether we call it a "year" or not, is irrelevant to these celestial observations. Just like "time", all other valid measurements must be rooted in reality.

 

[petm1]

The Earth is about 5 billion years old, My dog died at 13 years, that grain of sand has a duration, as do all things. Time is a mosaic however I view it, with each four dimensional object adding but its own part to this dilating image I see as my present.

 

[Homesick345]

Thanks all for the diverse and superb answers. I am humbled by the level of this forum.

 

[chill_factor]

throw a drinking glass on the ground. it breaks. that's forward time. it will never self assemble, dive up from the ground and put itself back into your hand.

 

[petm1]

What do you think the probability would be of the glass forming itself without the help of the co-moving frame of consciousness in humans?

 

[Chalnoth]

What do you think the probability would be of the glass forming itself without the help of the co-moving frame of consciousness in humans?

Consciousness has zero effect on the behavior of reality (except the obvious bits like building houses, computers, etc.).

 

[sahmgeek]

I'm not convinced you can actually measure time (or space). I suspect we are only able to measure the finite things that exist within spacetime. asking what a universe would be like without time is like asking what a universe would be like without space. it's nonsensical to us (finite beings). time plays a real part, albeit the most elusive one, imo. this is also what makes it the most interesting (imo)

 

[sahmgeek]

why do we need time? & what would be the alternative?

i think we need both space and time to provide reference points. the alternative would be something that we could not really put into words b/c we wouldn't be able to make any sense out of it. unless the alternative (no time) was what we were used to, then we could discuss it. does that make sense

 

[sahmgeek]

and if you REALLY think about it, time and space might actually BE the same "thing" (for lack of a better word). stick that into your equation!

actually, has anyone?

 

[petm1]

Consciousness has zero effect on the behavior of reality (except the obvious bits like building houses, computers, etc.).

Consciousness is required for us to see the behavior of reality, and the co-moving frame of my consciousness is the one second part of time that I am always within, what do you think makes up our present.

 

[alt]

I've always thought that when thinking about what time is, or whether it exists, one has to look at the immediate, first hand experience of it - the present.

And when trying to work out what the present is, I get even more perplexed. Is it a certain amount of time ? It must be, for if it was a point instant, it would be static, and no movement would be possible.

But how long IS your experienced present ? A second ? Half that ? Douple that ? One hundredth that ? In any case, it would still have (unless it was a point instant), a component of past, and possibly future in it. Weird !

 

[Homesick345]

I've always thought that when thinking about what time is, or whether it exists, ... In any case, it would still have (unless it was a point instant), a component of past, and possibly future in it. Weird !

Super weird indeed. Moreover, if time exists, & it passes linearly, it should have an infinite speed, since it passes continuously..Time is weirder than existence itself

 

[Chalnoth]

Super weird indeed. Moreover, if time exists, & it passes linearly, it should have an infinite speed, since it passes continuously..Time is weirder than existence itself

Why would you think this?

And anyway, time "passing" is just a colloquial description that doesn't have any relation to reality, as near as I can tell.

 

[Alephu5]

I think there is unanimous agreement that as humans, we all experience something which can be called "time" in English, which describes a one-directional increase in entropy of the universe at a constant rate. In this sense it is perfectly reasonable to assume that it exists. The real challenge is trying to abstract beyond the individual's perspective and learn about the nature of time itself.

We know that time does not actually move at a constant rate, and that an individual will never notice a difference despite the relative rate of time compared to that of those moving more slowly, or in places with less gravity. My own speculative opinion is that time appears to us the way it does because of the makeup of our bodies. All that we feel, say and do is a result of physical and chemical interactions and therefore the same rules of entropy that govern forms of matter in the universe determine our experience of life and "time". If there exists a somewhat biological being in a macro-verse that contains our universe, they may be able to see our universe as a static entity with 4 "spatial" dimensions.

 

[Chalnoth]

Talk of colloquial experience is describing us, not time.

 

[sahmgeek]

Consciousness is required for us to see the behavior of reality, and the co-moving frame of my consciousness is the one second part of time that I am always within, what do you think makes up our present.

this gets tricky, distinguishing between consciousness as "experience" and reality as "that which is experienced". two separate things, i think, but clearly deeply connected (some would argue inseparable).

 

[Homesick345]

Why would you think this?

And anyway, time "passing" is just a colloquial description that doesn't have any relation to reality, as near as I can tell.

Well, (I'm sure I will sound crazy - & I'm not a physicist or scientist of any kind), but since time passes & covers every second & milli-second, it covers an infinity of moments...the billionth milli-second of milli second etc...the flow of time, if there is such a thing as a "flow" of time, must go at a vertiginous spead. Because of the infinity of each single present "situation", therefore time is relentless & infinitely speeding..

 

[sahmgeek]

I've always thought that when thinking about what time is, or whether it exists, one has to look at the immediate, first hand experience of it - the present.

And when trying to work out what the present is, I get even more perplexed. Is it a certain amount of time ? It must be, for if it was a point instant, it would be static, and no movement would be possible.

But how long IS your experienced present ? A second ? Half that ? Douple that ? One hundredth that ? In any case, it would still have (unless it was a point instant), a component of past, and possibly future in it. Weird !

yes, so if you discuss time as something that is "experienced" you have to have an agent to experience it; you have to have it be consciousness dependent. and this is how we think of time. we "experience" time as one-directional, however I suspect the TRUE nature of time is just space somehow filtered through a relative lens. does that make sense?

 

[sahmgeek]

I think there is unanimous agreement that as humans, we all experience something which can be called "time" in English, which describes a one-directional increase in entropy of the universe at a constant rate. In this sense it is perfectly reasonable to assume that it exists. The real challenge is trying to abstract beyond the individual's perspective and learn about the nature of time itself.

We know that time does not actually move at a constant rate, and that an individual will never notice a difference despite the relative rate of time compared to that of those moving more slowly, or in places with less gravity. My own speculative opinion is that time appears to us the way it does because of the makeup of our bodies. All that we feel, say and do is a result of physical and chemical interactions and therefore the same rules of entropy that govern forms of matter in the universe determine our experience of life and "time". If there exists a somewhat biological being in a macro-verse that contains our universe, they may be able to see our universe as a static entity with 4 "spatial" dimensions.

I agree

 

[sahmgeek]

however I suspect the TRUE nature of time is just space somehow filtered through a relative lens. does that make sense?

and taking that thought one step further is the idea that NOTHING has a TRUE nature independently. instead, it is all relative...micro to macro

 

[Alephu5]

and taking that thought one step further is the idea that NOTHING has a TRUE nature independently. instead, it is all relative...micro to macro

This is similar to a philosophical perspective called "Model-dependant realism" put forward in a book called "The Grand Design" by Stephen Hawking and Leonard Mlodinow. It does not talk about hierarchies of subsystems within supersystems, but rather that there is a common scientific misconception, that models describe the underlying reality of a situation. It refers to the fact that two intuitively different concepts can describe the exact same thing, and that as humans, all we can do is build models and use them until they no longer describe observations. Basically, reality is a concept that exists within the mind of creatures such as ourselves. In the mind of a religious person this may not necessarily comply with reality for a scientist, who has empirically found models that reliably describe observations. Even so, the idea of things having a true nature is an illusion.

A quote from the book:

"According to the idea of model-dependent realism ..., our brains interpret the input from our sensory organs by making a model of the outside world. We form mental concepts of our home, trees, other people, the electricity that flows from wall sockets, atoms, molecules, and other universes. These mental concepts are the only reality we can know. There is no model-independent test of reality. It follows that a well-constructed model creates a reality of its own."

 

[sahmgeek]

This is similar to a philosophical perspective called "Model-dependant realism" put forward in a book called "The Grand Design" by Stephen Hawking and Leonard Mlodinow. It does not talk about hierarchies of subsystems within supersystems, but rather that there is a common scientific misconception, that models describe the underlying reality of a situation. It refers to the fact that two intuitively different concepts can describe the exact same thing, and that as humans, all we can do is build models and use them until they no longer describe observations. Basically, reality is a concept that exists within the mind of creatures such as ourselves. In the mind of a religious person this may not necessarily comply with reality for a scientist, who has empirically found models that reliably describe observations. Even so, the idea of things having a true nature is an illusion.

A quote from the book:

interesting. i'll check it out. thanks.

another thought i had today, not fully related but somewhat relevant is that we get easily tripped up by language and logic. we use logic, well, b/c nature shows us that that is how the world works (patterns, cause & effect, etc). but "nature" knows something that we don't (it could be something along the lines of this type of Model-dependant realism theory) and we encounter paradox. until we can incorporate that missing piece (if we ever can) we'll never fully understand.

 

[Chalnoth]

Well, (I'm sure I will sound crazy - & I'm not a physicist or scientist of any kind), but since time passes & covers every second & milli-second, it covers an infinity of moments...the billionth milli-second of milli second etc...the flow of time, if there is such a thing as a "flow" of time, must go at a vertiginous spead. Because of the infinity of each single present "situation", therefore time is relentless & infinitely speeding..

You're making a number of assumptions here that are unwarranted.

First, that there are an infinite number of instances of time. There are certainly an extremely large number, but our limited knowledge of quantum gravity suggests that a finite number of instances is possible.

Second, that somehow it makes sense to talk in speed versus a number of instantaneous moments.

Third, that there is a flow of time at all, that it isn't just a perceptual illusion. Relativity strongly suggests that there is no such flow, period.

 

[sahmgeek]

Third, that there is a flow of time at all, that it isn't just a perceptual illusion. Relativity strongly suggests that there is no such flow, period.

without a doubt, all humans (except maybe those with neurological "abnormalities") can agree that we experience time as having a "flow". This is indisputable, is it not? Things occur in a certain "order". If not, we wouldn't even be able to have this conversation.

 

[sahmgeek]

also, i think we should replace (altogether) the word "illusion" with "relative in nature".

 

[Chalnoth]

without a doubt, all humans (except maybe those with neurological "abnormalities") can agree that we experience time as having a "flow". This is indisputable, is it not?

As I said, this speaks more about us than it does about the reality of time. We don't experience the real world raw and unfiltered. We experience the world through the lens of our senses and the processing that goes on in our brains.

 

[Mark M]

Well, (I'm sure I will sound crazy - & I'm not a physicist or scientist of any kind), but since time passes & covers every second & milli-second, it covers an infinity of moments...the billionth milli-second of milli second etc...the flow of time, if there is such a thing as a "flow" of time, must go at a vertiginous spead. Because of the infinity of each single present "situation", therefore time is relentless & infinitely speeding..

It seems more and more likely that time is discrete - that is, divided into moments. The length of such a moment would the Planck Time, which is the amount of time that is takes light to travel one Planck length. The Planck Length is for all purposes the smallest you can get, as it corresponds to Planck's Constant, a figure which represents the size of the smallest unit of energy, a quantum.

without a doubt, all humans (except maybe those with neurological "abnormalities") can agree that we experience time as having a "flow". This is indisputable, is it not? Things occur in a certain "order". If not, we wouldn't even be able to have this conversation.

Events occur in a particular order because of the second law of thermodynamics - that is, entropy will always increase. Like Chalnoth said, time doesn't flow, as relativity treats it as a fourth dimension that we move through, not it flowing by us.

 

[sahmgeek]

As I said, this speaks more about us than it does about the reality of time. We don't experience the real world raw and unfiltered. We experience the world through the lens of our senses and the processing that goes on in our brains.

true, but the implications of this raise a huge question concerning whether we will ever be able to understand raw, unfiltered reality (if there is such a thing...i think there is).

 

[Drakkith]

true, but the implications of this raise a huge question concerning whether we will ever be able to understand raw, unfiltered reality (if there is such a thing...i think there is).

Define "raw, unfiltered reality".

 

[sahmgeek]

Define "raw, unfiltered reality".

exactly. Ask Chalnoth; he/she proposed it.

 

[sahmgeek]

Events occur in a particular order because of the second law of thermodynamics - that is, entropy will always increase. Like Chalnoth said, time doesn't flow, as relativity treats it as a fourth dimension that we move through, not it flowing by us.

I did not suggest that time, itself, flows. I think i said that we experience time as flowing (i.e. arrow of time). HUGE difference. so, on this point, we agree.

 

[Drakkith]

exactly. Ask Chalnoth; he/she proposed it.

Ah, I see now. The way we experience the universe is dependant on our senses.

 

[petm1]

It seems more and more likely that time is discrete - that is, divided into moments. The length of such a moment would the Planck Time, which is the amount of time that is takes light to travel one Planck length. The Planck Length is for all purposes the smallest you can get, as it corresponds to Planck's Constant, a figure which represents the size of the smallest unit of energy, a quantum.

Think of Planck's time, we use a photon to measure it but is time the photon? Is time the length of the photons motion in one dimension? I liken time to the duration of the photon's motion not as one dimensional like the photon but as a dilating three dimensional sphere with the photon used as the radius, making time the dilating area that gives the photon's its direction in space.

It seems more and more likely that time is discrete - that is, divided into moments. The length of such a moment would the Planck Time, which is the amount of time that is takes light to travel one Planck length. The Planck Length is for all purposes the smallest you can get, as it corresponds to Planck's Constant, a figure which represents the size of the smallest unit of energy, a quantum.

Matter is discrete and if you think of time as a three sphere then to me matter appears as one moment of time filled with energy a four dimensional object that we can use as a clock. Billions of clocks all started at the same relative time, from the same Planck length, and still relative to each of us today.

 

[Drakkith]

Think of Planck's time, we use a photon to measure it but is time the photon? Is time the length of the photons motion in one dimension? I liken time to the duration of the photon's motion not as one dimensional like the photon but as a dilating three dimensional sphere with the photon used as the radius, making time the dilating area that gives the photon's its direction in space.

What? The distance the photon travels is used to measure the time, the photon is not time itself. I can't follow the rest of your post as it doesn't make any sense to me. My personal view is simply that time is a measurement just like distance is.

 

[Chalnoth]

true, but the implications of this raise a huge question concerning whether we will ever be able to understand raw, unfiltered reality (if there is such a thing...i think there is).

Understanding the true nature of reality is what science is for.

 

[Chalnoth]

Ah, I see now. The way we experience the universe is dependant on our senses.

Yes, precisely. And more than that the way our brains behave. This is why science is so important: it allows us to move past the biases imposed by our limited senses and cognitive biases.

 

[sahmgeek]

Yes, precisely. And more than that the way our brains behave. This is why science is so important: it allows us to move past the biases imposed by our limited senses and cognitive biases.

how is that at all possible? how are we getting beyond the limits of our senses? science is LIMITED TO our senses, is it not?

 

[Chalnoth]

how is that at all possible? how are we getting beyond the limits of our senses? science is LIMITED TO our senses, is it not?

Not at all!

To take a trivial example, we can only see electromagnetic radiation within a narrow range of wavelengths, from about 390nm to 750nm. But with the right instruments we can detect any form of electromagnetic radiation, from radiation with wavelengths of many meters (or more) to radiation with wavelengths as small as a proton (sometimes even smaller).

 

[sahmgeek]

Not at all!

To take a trivial example, we can only see electromagnetic radiation within a narrow range of wavelengths, from about 390nm to 750nm. But with the right instruments we can detect any form of electromagnetic radiation, from radiation with wavelengths of many meters (or more) to radiation with wavelengths as small as a proton (sometimes even smaller).

Instruments are an extension of our senses. Our senses magnified.

 

[Chalnoth]

Instruments are an extension of our senses. Our senses magnified.

Which is one way which science allows us to push past our limitations.

The other major way is cognitive: by requiring independent verification of results, and by using explicit models of the universe which provide precisely predictions, we can move past our cognitive biases.

Any attempt to access the fundamental behavior of reality which only relies on personal experience is doomed to fail because our cognitive biases are basically guaranteed to muck things up. So we need to correct for them. And that is what science is good at.

 

[alt]

Super weird indeed. Moreover, if time exists, & it passes linearly, it should have an infinite speed, since it passes continuously..Time is weirder than existence itself

The above and your further comments in a later post about time having infinite speed.

I'm not sure what you're getting at. I just walked past my desk - it has an infinite number of points on it, yet I walked past them in about one second - not t infinite speed.

 

[alt]

Which is one way which science allows us to push past our limitations.

The other major way is cognitive: by requiring independent verification of results, and by using explicit models of the universe which provide precisely predictions, we can move past our cognitive biases.

Any attempt to access the fundamental behavior of reality which only relies on personal experience is doomed to fail because our cognitive biases are basically guaranteed to muck things up. So we need to correct for them. And that is what science is good at.

I certainly respect what you're saying here. Nevertheless, it s still a matter of personal experience on the part of scientists.

Chalnoth, I want to ask you - what is your personal experience of the present moment. What time (or any other) value do you place on it ?

 

[Homesick345]

The above and your further comments in a later post about time having infinite speed.

I'm not sure what you're getting at. I just walked past my desk - it has an infinite number of points on it, yet I walked past them in about one second - not t infinite speed.

I'm not sure what I'm getting at neither. I always felt that time goes through a "contimuum", a flow, while matter is discrete. Since early childhood, I felt time goes at vertiginous speeds (of course what is that speed & what I'm getting at; may well be nonsense - sorry!)

 

[Chalnoth]

I certainly respect what you're saying here. Nevertheless, it s still a matter of personal experience on the part of scientists.

Not at all!

The main point here is that we don't trust our perceptions, or even our thought process. We check them against others. Others are unlikely to fall for the same errors in the same way, and even when they are due to various cognitive biases, there are generally many different ways to test a given scientific model, and those different ways of testing the same model are highly unlikely to be susceptible to our cognitive biases in the same way.

To say it another way, science is a way of answering the question, "How can we learn what's true without being able to trust ourselves?" Independent verification provides that.

Chalnoth, I want to ask you - what is your personal experience of the present moment. What time (or any other) value do you place on it ?

I don't go by personal experience. I go by evidence.

The evidence to date is that the best description we currently have for the description of time lies in General Relativity. And GR has a number of interesting features which upset our typical colloquial notions of time. One of the most critical is that there is no such thing as a global "now" in General Relativity. That is to say, different observers will generally disagree as to which far-away events occur simultaneously.

While it may seem weird or trivial, this is a truly profound insight. The lack of a global now means, necessarily, that the past and future have the exact same existence as the present. And that is profoundly strange, given our colloquial notions. We are not a set of beings traveling in time, for example: we exist at all times. If we were able to somehow step outside of our space-time and observe the whole of our space-time from the outside, we would see both our past and future selves.

The only thing that gives the illusion of the flow of time is our cognitive processes. Specifically, our brains process information about our surroundings in a time-ordered fashion, and store memories in a time-ordered fashion. So that when we perceive the world, everything appears strongly time-ordered, when in reality this ordering is simply a feature of our cognitive processes, which in turn have a strict time ordering due to the nature of entropy (which tends to increase with time).