# Why is it so hard to explain time? (What is time?)

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5 hours ago, chron44 said:

Yeah, right.. hmm..

Just google'd and chat bot'ed.. The electromagnetic field include time as an independent parameter, depending which theory one uses. -And the photon, which naturally include time, obviously are quanta of this field.

…and ?

a dynamic field changes in time. What’s the connection?

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5 hours ago, chron44 said:

Yeah, right.. hmm..

Just google'd and chat bot'ed.. The electromagnetic field include time as an independent parameter, depending which theory one uses. -And the photon, which naturally include time, obviously are quanta of this field.

I can't immediately see what this reply of yours has to do with the question you asked or the answer I gave you. But let me see if I can help dispel any misunderstandings.

Light, or other EM radiation, is not energy. EM radiation has energy. Not is, has. Energy is one of the properties of EM radiation. It also has other properties, such as velocity, amplitude, wavelength, frequency, direction, and (somewhat counterintuitively) angular momentum or "spin".  Energy is merely one of these properties.

The time dimension is obviously important to describing any wave. This is not specially profound, I think.

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11 minutes ago, swansont said:
5 hours ago, chron44 said:

Yeah, right.. hmm..

Just google'd and chat bot'ed.. The electromagnetic field include time as an independent parameter, depending which theory one uses. -And the photon, which naturally include time, obviously are quanta of this field.

…and ?

a dynamic field changes in time. What’s the connection?

Energy maybe..??. And you informed that energy is just a property in physics. So energy cannot be a connection in it self. Though electromagnetic fields got direction and a time property... Where the photon, for example, got linear momentum (direction and time [m/s]), spin and energy. Yes, energy via the photon is the connection.

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1 hour ago, swansont said:
7 hours ago, chron44 said:

Yeah, right.. hmm..

Just google'd and chat bot'ed.. The electromagnetic field include time as an independent parameter, depending which theory one uses. -And the photon, which naturally include time, obviously are quanta of this field.

…and ?

a dynamic field changes in time. What’s the connection?

Though I cannot clearly see what you are asking for.

Or, just, the photon is the connection between the changes in the dynamic electromagnetic field. Since the photon, not is energy, but has. And the photon takes time, at c speed, to mediate, change, the (which?) dynamic field.

Still, I wonder what you ask for? Connection to what? The electromagnetic field consist of both an electric field an magnetic field. A changing electric field induces a magnetic field, and a changing magnetic field induces an electric field. This reciprocal relationship allows for the propagation of electromagnetic waves through space, with oscillating electric and magnetic fields perpendicular to each other. And this propagation occurs at c speed.

And there are several different theories about electromagnetic fields, also...

Photons play a crucial role in mediating electromagnetic interactions. In the framework of quantum electrodynamics (QED), which is the quantum field theory describing electromagnetic interactions, photons are the force carriers of the electromagnetic force. They mediate the exchange of energy and momentum between charged particles, transmitting the electromagnetic interaction.

Force normally got a specific direction and a time component. And, generally, energy, if separated from the force concept, has no direction nor a time property.

You have to be a bit more precise in your quest, I think...

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1 hour ago, chron44 said:

Still, I wonder what you ask for? Connection to what? The electromagnetic field consist of both an electric field an magnetic field. A changing electric field induces a magnetic field, and a changing magnetic field induces an electric field. This reciprocal relationship allows for the propagation of electromagnetic waves through space, with oscillating electric and magnetic fields perpendicular to each other. And this propagation occurs at c speed.

How does this reveal anything about time?

1 hour ago, chron44 said:

Force normally got a specific direction and a time component.

You can have static forces

1 hour ago, chron44 said:

And, generally, energy, if separated from the force concept, has no direction nor a time property.

If you are doing work on an object (which requires exerting a force) the energy can increase or decrease in time

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1 hour ago, chron44 said:

…and ?

a dynamic field changes in time. What’s the connection?

3 minutes ago, swansont said:

How does this reveal anything about time?

Oh.., first, a dynamic electromagnetic field gets dynamic from several sources. Normally a AC current through conductors or radio antennas do. At the case with the AC current we get 60 or 50 Hz depending on country. The dynamic field's fluctuation therefore is dependent on the source's frequency.. hmm.. How this reveals the concept of "time".. yes..

We obviously have to get back to the clock describing. A clock is a fixed pace tech... So, we're back to the initial quest, "what is time? And time very distinct by everybody here was expressed with: Time is what a clock, preferably a atomic cesium 133 construction, presents. Time explanation seems going in circles. And time obviously does not easily reveal its true nature.

For me it looks like time being an imaginary physical reference unit. Though a most used, and therefore a most important, such.

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Excerpt:

"Note that while time is a fundamental concept in our understanding of the physical world, its nature is complex and interconnected with other aspects of physics, such as gravity, relativity, and quantum mechanics. The understanding of time has evolved with advancements in physics and continues to be an area of exploration and investigation."

-- End of excerpt. -- ChatGPT 3.5 updated January 2022

~~~~~~~~~~~~~~~~~~

And I'm just only trying to explore the concept of time especially with physics in mind.

Sigh..

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2 hours ago, chron44 said:

Excerpt:

"Note that while time is a fundamental concept in our understanding of the physical world, its nature is complex and interconnected with other aspects of physics, such as gravity, relativity, and quantum mechanics. The understanding of time has evolved with advancements in physics and continues to be an area of exploration and investigation."

-- End of excerpt. -- ChatGPT 3.5 updated January 2022

~~~~~~~~~~~~~~~~~~

And I'm just only trying to explore the concept of time especially with physics in mind.

Sigh..

Ask yourself: What is so special about time that we must agonize over it when every other measurement parameter never gets a second look?

Edited by StringJunky
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Okay.

1. What is unsatisfactory about time being defined as the 4th dimension?
2. What is unsatisfactory about time being defined as measurable duration between actions or processes?
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7 hours ago, AIkonoklazt said:

Okay.

1. What is unsatisfactory about time being defined as the 4th dimension?
2. What is unsatisfactory about time being defined as measurable duration between actions or processes?

About #1: The 4th dimension? Nothing, I believe. If being "unsatisfactory", it's because of the mixing with different "dimensions".

We have to be clear about that time in GR, for example, is treated both - like - it was the 4th spatial dimension, and a separate time dimension. This is especially noticed in the spacetime interval concept involved in the GR formulas:

ds^2=−c^2dt^2+dx^2+dy^2+dz^2

Here, ds is the spacetime interval. That obviously incorporates both time (s) and spatial dimensions (m) into a crucial ds parameter included in the formulas. Observe that in this GR fundamental concept time is treated as time, and space is treated as space, though the, further used, "output" of ds is a mix of both.

Concerning #2: Nothing is unsatisfactory with time seen or defined being the duration between separable events. Probably the influence of GR and similar formulas, with such mixing described in #1, may have contributed to a "unsatisfactory" impression of time defined in this manner.

Edited by chron44
clarifying
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42 minutes ago, chron44 said:

This is especially noticed in the spacetime interval concept involved in the GR formulas:

ds^2=−c^2dt^2+dx^2+dy^2+dz^2

The formula above is correct only for a flat spacetime in Minkowski coordinates. The general GR formula is, $$ds^2=g_{\mu \nu} dx^{\mu} dx^{\nu}$$ (the summation convention implied.)

42 minutes ago, chron44 said:

crucial ds parameter included in the formulas

In GR, this "crucial parameter" does not appear in any important formulas.

42 minutes ago, chron44 said:

separable events

There is no such thing. It is either one event or separate events.

42 minutes ago, chron44 said:

time in GR, for example, is treated both - like - it was the 4th spatial dimension

Nowhere in GR time is treated as the 4th spatial dimension.

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11 hours ago, chron44 said:

We obviously have to get back to the clock describing. A clock is a fixed pace tech... So, we're back to the initial quest, "what is time? And time very distinct by everybody here was expressed with: Time is what a clock, preferably a atomic cesium 133 construction, presents. Time explanation seems going in circles. And time obviously does not easily reveal its true nature.

I prefer Rb-87, but that’s a personal bias. Some former colleagues like calcium and strontium

11 hours ago, chron44 said:

For me it looks like time being an imaginary physical reference unit. Though a most used, and therefore a most important, such.

How does this differ from length?

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26 minutes ago, swansont said:
11 hours ago, chron44 said:

For me it looks like time being an imaginary physical reference unit. Though a most used, and therefore a most important, such.

How does this differ from length?

How does one say? This is a good question.

Yes, it is...

For the moment I've collected enough minus reactions.

So, I'll rest my case here, for the moment.

😉

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• 2 months later...
Posted (edited)
It cannot be an unknown x but it's a known variable. It's particular

Edited by harlock
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On 1/10/2024 at 5:31 AM, chron44 said:

About #1: The 4th dimension? Nothing, I believe. If being "unsatisfactory", it's because of the mixing with different "dimensions".

We have to be clear about that time in GR, for example, is treated both - like - it was the 4th spatial dimension, and a separate time dimension. This is especially noticed in the spacetime interval concept involved in the GR formulas:

ds^2=−c^2dt^2+dx^2+dy^2+dz^2

Here, ds is the spacetime interval. That obviously incorporates both time (s) and spatial dimensions (m) into a crucial ds parameter included in the formulas. Observe that in this GR fundamental concept time is treated as time, and space is treated as space, though the, further used, "output" of ds is a mix of both.

Concerning #2: Nothing is unsatisfactory with time seen or defined being the duration between separable events. Probably the influence of GR and similar formulas, with such mixing described in #1, may have contributed to a "unsatisfactory" impression of time defined in this manner.

Ds is the separation distance interval is designated by (ct) though that's usually  shortened to simply t. The interval allows time to have the same dimensionality of length via the interval

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Posted (edited)

I can think of at least three kinds of time, and the distinctions are important.

On 1/7/2024 at 3:39 PM, swansont said:

One definition is that time is what is measured by a clock.

What clocks measure is proper time, which, in GR terminology, is the spacetime interval along the time-like worldline followed by the clock, completely analogous to proper distance being measured by tape measure following a space-like worldline.

Proper time is an invariant (it is not frame dependent). It is physical and very real.

On 1/7/2024 at 1:31 PM, chron44 said:

I assume the halved "time" concept, for example, in the well established spacetime (GR/ SR) concept, is a physics issue.

If we only discuss "time" used in science: What is time in physics?

.. If persisting in my view of time being a physical issue, and not only a metaphysical subject.

Getting beyond strictly physical, there is also coordinate time. Coordinate time is the time coordinate assigned to events by a particular abstract coordinate system. It is purely abstract (a mental thing, not a physical one). It is very frame dependent, but still physics, not metaphysics.

If we get truly down to metaphysics/philosophy, we get to the third kind of time, which is the progression of the present moment. It is 'that which flows'. When somebody asks if time is real, they're probably talking about this kind. It probably has an official name but I don't know it.  I call it teapot time since like the teapot purported to be in orbit around the sun somewhere beyond Jupiter, there is zero empirical evidence for it, but its existence also cannot be disproven.

So to give an example of the three kinds, we decide to throw Bob (and his watch) into a black hole.  In some coordinate systems (say that of a distant observer), Bob takes forever to reach the event horizon. In a different coordinate system such as Kruskal–Szekeres coordinates, he falls right in in some finite time X. That's all coordinate time.

Proper time is easy: Bob's watch reads time P upon reaching the event horizon. That value is the same regardless of choice of frame.

As for proponents of teapot time, the only theory I know that includes it is forced to deny the existence of black holes at all since events within cannot exist, so any talk about falling into one is unsupported. This of course provides a semi-empirical test for presentism. If you jump into a large (at least say 15000 solar masses) black hole and find yourself inside, you've disproved presentism, but of course you cannot publish your findings in a science journal any more than you can publish your discovery of an afterlife. One has to die to test it, and the guy inside the black hole is, while not yet dead, certainly doomed.

Edited by Halc

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