Is time continuous or discrete?

[Dimebag]

I have been pondering this question lately after considering how we perceive time, and how the smaller you divide time into the less you can fit into it.

This lead me to wonder if time actually is divided into discrete moments, similar to a planck length but for time, or if it is indivisible and continuous, and you could slow time down as much as you wanted and couldn't see the "frames".

After considering it for a short time I thought that there probably isn't discrete moments, because if there were, there would probably be some kind of universal minimum speed limit for all matter. If a particle is moving at say, 1 planck length per "planck moment" this would restrict it to such a minimum speed, which seems slightly absurd. This is my reasoning for rejecting the possibility of the discreteness of time.

I would be interested in other peoples opinions on this topic,

Thanks
Dimebag.

[thalarch]

I have been pondering this question lately after considering how we perceive time, and how the smaller you divide time into the less you can fit into it.

This lead me to wonder if time actually is divided into discrete moments, similar to a planck length but for time, or if it is indivisible and continuous, and you could slow time down as much as you wanted and couldn't see the "frames".

After considering it for a short time I thought that there probably isn't discrete moments, because if there were, there would probably be some kind of universal minimum speed limit for all matter. If a particle is moving at say, 1 planck length per "planck moment" this would restrict it to such a minimum speed, which seems slightly absurd. This is my reasoning for rejecting the possibility of the discreteness of time.

There is a Planck-time that is indeed the interval it takes a photon to cross the distance of a unit of Planck length. Smaller divisions of time than that would lack meaning within the current framework of physics. Wondering whether or not such scientific measurements also imply something "non-artificially real" or have an existential validity independent of human practices may be a waste of time. Though some of them surely resist being classified as social constructs slightly better than the obviousness of their everyday counterparts.

[Dimebag]

I have been pondering this question lately after considering how we perceive time, and how the smaller you divide time into the less you can fit into it.

This lead me to wonder if time actually is divided into discrete moments, similar to a planck length but for time, or if it is indivisible and continuous, and you could slow time down as much as you wanted and couldn't see the "frames".

After considering it for a short time I thought that there probably isn't discrete moments, because if there were, there would probably be some kind of universal minimum speed limit for all matter. If a particle is moving at say, 1 planck length per "planck moment" this would restrict it to such a minimum speed, which seems slightly absurd. This is my reasoning for rejecting the possibility of the discreteness of time.

There is a Planck-time that is indeed the interval it takes a photon to cross the distance of a unit of Planck length. Smaller divisions of time than that would lack meaning within the current framework of physics. Wondering whether or not such scientific measurements also imply something "non-artificially real" or have an existential validity independent of human practices may be a waste of time. Though some of them surely resist being classified as social constructs slightly better than the obviousness of their everyday counterparts.

Ah thanks. So really the Planck time, and therefore the speed of light is the minimum speed limit of a photon? In that sense, 'time' is quite meaningless.

[Mike Strand]

Interesting thought, Dimebag, and you might ask the same about distance between two points. Is it "in reality" either zero or at least one unit of Planck length? This is speculating that time and distance are quantized along with energy states.

I don't know the answer, but it's interesting to compare this to mathematical theory. In calculus, "instantaneous" velocity exists and is defined as a limit - the change in distance divided the corresponding change in time, as the change in time approaches zero. That is, velocity is the derivative of distance with respect to time, which can be defined for any given continuous distance versus time curve. A Planck length, either in time or in distance, is mathematically a finite interval containing an infinite number of real numbers, and in taking the limit, the change in time gets closer and closer to zero, eventually closer than even a Planck unit of time.

Of course, in practice, we can approximate instantaneous velocity as closely as we want by taking a sufficiently small but positive change in time, and dividing it into the corresponding change in distance, to get an "average" velocity over that small time change. You could argue that Planck units of time are sufficiently small.

This has an interesting implication: If we define the Planck unit of time as the time it takes light to travel one unit of Planck distance, then the velocity of light is 1 pd per pt, or 1 Planck distance per planck time. Since everything else travels more slowly than light, their velocities should all be less than 1 pd per pt.

Now if you add the stipulation that distance is also quantized, and the smallest distance is one unit of Planck distance, then everything else but light has no defined (zero?) velocity over a unit of Planck distance! In effect, velocity is also quantized -- for example, an object we imagine as traveling at 1/100 the speed of light (0.01 pd per pt, still very fast) really wouldn't have a velocity until it had traveled for 100 units of Planck time, the time it would take it to travel one unit of Planck distance.

In effect, "instantaneous" velocity and zero distance and zero time duration would have a new meaning.

Edit: Thanks to thalarch for telling us about the unit of Planck time.

Also thanks to vancerfan for a different take on the whole thing -- to treasure the moments, no matter whether time is quantized or not!

[Mike Strand]

To follow up on the idea of time and distance being quantized: Acceleration would be quantized, as could be shown in a manner similar to the demonstration for velocity above, since acceleration is the derivative of velocity with respect to time.

Another idea regarding acceleration -- since it is a change in velocity, consider light. Can it accelerate? Yes, obviously in direction, since it bends in a gravitational field. It also bounces off of mirrors and bends going from water into air (refraction). Hmmm... but the speed in water is different from the speed in air, which is different from c, the speed in open space. So in going from water to air, it changes speed and direction. Is this acceleration infinite, meaning the velocity changes instantaneously? At least the acceleration is very large in magnitude. But if it occurs within a Planck unit of time, it isn't defined under the quantization of time and distance (and hence velocity).

So the quantization of time and distance implies a quantization of velocity and acceleration. Could this be a clue to quantizing gravity, which in GRT is equivalent to acceleration? Also, gravity is a feature of space and time, which might be quantizable as we've been speculating here.

[JohniJones]

I have been pondering this question lately after considering how we perceive time, and how the smaller you divide time into the less you can fit into it.

This lead me to wonder if time actually is divided into discrete moments, similar to a planck length but for time, or if it is indivisible and continuous, and you could slow time down as much as you wanted and couldn't see the "frames".

After considering it for a short time I thought that there probably isn't discrete moments, because if there were, there would probably be some kind of universal minimum speed limit for all matter. If a particle is moving at say, 1 planck length per "planck moment" this would restrict it to such a minimum speed, which seems slightly absurd. This is my reasoning for rejecting the possibility of the discreteness of time.

I would be interested in other peoples opinions on this topic,

Thanks
Dimebag.

Your original premise that you can fit less things into a shorter length of time was wrong.

The amount doesn't matter either way. Time is conceptual. Before and after are only the names of objects that we have designated as clocks.

[chaz wyman]

I have been pondering this question lately after considering how we perceive time, and how the smaller you divide time into the less you can fit into it.

This lead me to wonder if time actually is divided into discrete moments, similar to a planck length but for time, or if it is indivisible and continuous, and you could slow time down as much as you wanted and couldn't see the "frames".

After considering it for a short time I thought that there probably isn't discrete moments, because if there were, there would probably be some kind of universal minimum speed limit for all matter. If a particle is moving at say, 1 planck length per "planck moment" this would restrict it to such a minimum speed, which seems slightly absurd. This is my reasoning for rejecting the possibility of the discreteness of time.

I would be interested in other peoples opinions on this topic,

Thanks
Dimebag.

Do you mean by discrete; atomistic, and continuous as analogue.
I think the trouble with conceiving time is that we are faced with using spatial metaphors to describe it.
If you reject the metaphors then your questions disappear.

[chaz wyman]

I have been pondering this question lately after considering how we perceive time, and how the smaller you divide time into the less you can fit into it.

This lead me to wonder if time actually is divided into discrete moments, similar to a planck length but for time, or if it is indivisible and continuous, and you could slow time down as much as you wanted and couldn't see the "frames".

After considering it for a short time I thought that there probably isn't discrete moments, because if there were, there would probably be some kind of universal minimum speed limit for all matter. If a particle is moving at say, 1 planck length per "planck moment" this would restrict it to such a minimum speed, which seems slightly absurd. This is my reasoning for rejecting the possibility of the discreteness of time.

There is a Planck-time that is indeed the interval it takes a photon to cross the distance of a unit of Planck length. Smaller divisions of time than that would lack meaning within the current framework of physics. Wondering whether or not such scientific measurements also imply something "non-artificially real" or have an existential validity independent of human practices may be a waste of time. Though some of them surely resist being classified as social constructs slightly better than the obviousness of their everyday counterparts.

Ah thanks. So really the Planck time, and therefore the speed of light is the minimum speed limit of a photon? In that sense, 'time' is quite meaningless.

Pace Xeno's paradox. Planck is only another metaphor.

[edgarsv]

Light does not accelerate while passing from one medium to another, at least as we generally think of it. The wave changes speed but each photon always travels at C. Here's a quote from The Physics Classroom site:

"An electromagnetic wave (i.e., a light wave) is produced by a vibrating electric charge. As the wave moves through the vacuum of empty space, it travels at a speed of c (3 x 108 m/s). This value is the speed of light in a vacuum. When the wave impinges upon a particle of matter, the energy is absorbed and sets electrons within the atoms into vibrational motion. If the frequency of the electromagnetic wave does not match the resonant frequency of vibration of the electron, then the energy is reemitted in the form of an electromagnetic wave. This new electromagnetic wave has the same frequency as the original wave and it too will travel at a speed of c through the empty space between atoms. The newly emitted light wave continues to move through the interatomic space until it impinges upon a neighboring particle. The energy is absorbed by this new particle and sets the electrons of its atoms into vibration motion. And once more, if there is no match between the frequency of the electromagnetic wave and the resonant frequency of the electron, the energy is reemitted in the form of a new electromagnetic wave. The cycle of absorption and reemission continues as the energy is transported from particle to particle through the bulk of a medium. Every photon (bundle of electromagnetic energy) travels between the interatomic void at a speed of c; yet time delay involved in the process of being absorbed and reemitted by the atoms of the material lowers the net speed of transport from one end of the medium to the other. Subsequently, the net speed of an electromagnetic wave in any medium is somewhat less than its speed in a vacuum - c (3 x 108 m/s)."

[bran]

Thanks, edgarsv, for that quoted explanation of light speed through the process of absorption and re-emission. That was very informative and clear.

Bran

[SpheresOfBalance]

Time is not a thing, it's a concept! It's not a constant, It's units are arbitrary, dependent upon movement (change) around a particular point in the universe, which is relative to any given thing in the universe, such that if nothing existed at all, there would be no relative points of reference at all. It's a label attached to change with movement which is relative. if all molecular motion ceased, the concept of time would be impossible. If nothing existed at all, there would be no time, because nothing would change. So the fanciful concept of time travel is just so much the imagination of an extremely immature life-form, when compared to the "amount of human change (evolution)" required to fathom the cosmos. The fact is that, everything/concept is always and can only be relative to another thing/concept! If there in none, or only one, there is no time (change). If there was only one, how fast would it be going and how old would it be? The answer is from 0 to infinity, all at the same "time!"

[chaz wyman]

Time is not a thing, it's a concept!

So is truth.

It's not a constant,


So is truth.

... which is relative to any given thing in the universe,

So is truth.


such that if nothing existed at all, there would be no relative points of reference at all.

And if there were no one to articulate truth there would be none.
It is relative.

[SpheresOfBalance]

Time is not a thing, it's a concept!

So is truth.

It's not a constant,


So is truth.

... which is relative to any given thing in the universe,

So is truth.


such that if nothing existed at all, there would be no relative points of reference at all.

And if there were no one to articulate truth there would be none.
It is relative.


Wrong, wrong, wrong and wrong!

Obviously you fear acknowledging my definition of truth. You and I both know that your snip in the truth thread conveniently came at a point after which you feared to tread.

P.S. it's considered rude to hijack a thread. So please, in the name of Netiquette, continue in the proper thread.

[chaz wyman]

Time is not a thing, it's a concept!

So is truth.

It's not a constant,


So is truth.

... which is relative to any given thing in the universe,

So is truth.


such that if nothing existed at all, there would be no relative points of reference at all.

And if there were no one to articulate truth there would be none.
It is relative.


Wrong, wrong, wrong and wrong!

Obviously you fear acknowledging my definition of truth. You and I both know that your snip in the truth thread conveniently came at a point after which you feared to tread.

P.S. it's considered rude to hijack a thread. So please, in the name of Netiquette, continue in the proper thread.

I had not noticed you define truth. I had noticed you made false claims about it. What is your definition?
And what is your epistemological basis for that definition.

[SpheresOfBalance]

Chaz Wyman, it's considered rude to hijack a thread. So please, in the name of Netiquette, continue in the proper thread.