# What is time ?

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My point of view about time

The human observer invented the concept of time and clock because it was difficult for him to measure change and speed of change (rapidity of change or slowness of change) which along with: space, matter, energy, forces, fields, .... are fundamental constituents and properties of the universe.
Time is nothing but the relationship between change and the speed of change. Time only makes sense for what is changing at a certain speed, so it is a function of these two.
Time is relative depending on the nature of the change: life time, half-life for radioactive substances, reaction time, astronomical time ....

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Is there a testable hypothesis here? A model, or evidence?

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2 hours ago, Time Traveler said:

Time is nothing but the relationship between change and the speed of change.

That is trivially true:

$\frac{\triangle Q}{\triangle Q/\triangle t}=\triangle t$

$$\triangle$$ meaning "change" and $$Q$$ being any physical quantity.

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4 hours ago, Time Traveler said:

My point of view about time

The human observer invented the concept of time and clock because it was difficult for him to measure change and speed of change (rapidity of change or slowness of change) which along with: space, matter, energy, forces, fields, .... are fundamental constituents and properties of the universe.
Time is nothing but the relationship between change and the speed of change. Time only makes sense for what is changing at a certain speed, so it is a function of these two.
Time is relative depending on the nature of the change: life time, half-life for radioactive substances, reaction time, astronomical time ....

Time is real...space is real....spacetime is real...the universe "is" spacetime. It is nothing more the the three spatial coordinates, along with time. It can be bent, warped, twisted etc, in the presence of mass/energy. Time is relative dependent on one's frame of reference, and is interchangeable with space. There is no universal now. Something need not be "physical" to be real.

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4 hours ago, Time Traveler said:

Time is nothing but the relationship between change and the speed of change.  ....

I mean time is a relation between two fundamental properties of the Universe:

Change and Speed of change

A process of changing or causing something to change from one form/position to another well known is displasement in space.  Another one is  a chimical reaction.....reactants changing in products

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1 minute ago, Time Traveler said:

Change and Speed of change

And what is speed? And what is change? Isn't time already implied there?

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3 minutes ago, Time Traveler said:

I mean time is a relation between two fundamental properties of the Universe:

More accurately, time is the interval between sequential events, whose measurement depends on one's frame of reference, and is interchangeable with space.

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In the distant past Changes and the speed of change were observed but could not be measured .... Observations such as periodic changes: the movement of revolution (astronomical year) and rotation of the earth (day) around the sun at almost constant speeds, the drain of a quantity of sand in an hourglass at almost constant speed are several examples from the observations of the thinking man. Man could observe the changes and although they unfold at a certain speed but could not measure them. At first the hourglass then the clock helped him measure time, this function, this ratio Change / Speed of change ... an important step forward for human activities ... especially for changing position (movement) at a certain speed .... t = d / v. The change in position could be measured approximately by standards such as pitch, length of a stick, then with another standard, the meter a much more accurate measurement. Speed was much harder to measure but could be calculated v = d / t using two measures obtained with the help of the hourglass (clock) and the meter.

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56 minutes ago, Time Traveler said:

Change and Speed of change

Do you think lack of change is unimportant?

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18 minutes ago, michel123456 said:

No.

If you look at someone at a certain distance from you, you will see him as he was a few milliseconds in the past. Even if no change occurs. In the distance, time is there.

Human observer perceives the surrounding world usually through photons that have the maximum speed known to us .... which is not necessarily the maximum speed in the Universe.
Due to the perception of the environment through the photons we have this impediment to not observe in "'direct" but in "' resumption"

Changes are continuousos.....the speed of change can tend to 0

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16 minutes ago, Time Traveler said:

Human observer perceives the surrounding world usually through photons that have the maximum speed known to us .... which is not necessarily the maximum speed in the Universe.

It is as far as Einstein's theories are concerned, and as yet we have no reason at all to doubt them.

18 minutes ago, Time Traveler said:

Due to the perception of the environment through the photons we have this impediment to not observe in "'direct" but in "' resumption"

Changes are continuousos.....the speed of change can tend to 0

We observe simply at a rate/time it takes photons to reach our eyes.

Changes or passages of time simply depend on one's frame of reference. These are indisputable facts, as evidenced many times.

Instead of your continuing statements of certainty, do you have any evidence? or perhaps a new hypothesis?

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The OP's opinion is easily falsified.
His question gets asked time and time again, but the answer never changes.
So it would seem, time is independent of change.

( sorry if I'm being snarky, had to put my cat to 'sleep' today )

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Sorry about your friend having to pass, mate. I’ll tip a glass your way later this evening.

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59 minutes ago, MigL said:

The OP's opinion is easily falsified.
His question gets asked time and time again, but the answer never changes.
So it would seem, time is independent of change.

( sorry if I'm being snarky, had to put my cat to 'sleep' today )

My condolences, @MigL. I know how hard it is to say goodbye to a friend.

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I think people are conflating time and time measurement, and I will reiterate: Is there a testable hypothesis here? A model, or evidence?

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1 hour ago, MigL said:

The OP's opinion is easily falsified.
His question gets asked time and time again, but the answer never changes.
So it would seem, time is independent of change.

( sorry if I'm being snarky, had to put my cat to 'sleep' today )

My condolences also for the passing of your friend.

I can't help but notice that positioning an event (such as a tearful goodbye appointment at a vet's office) in spacetime seems independent of change. Your latitude, longitude, altitude, and the time it took place aren't subject to change, are they? Yet it makes perfect sense to use time in this way.

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1 hour ago, MigL said:

The OP's opinion is easily falsified.
His question gets asked time and time again, but the answer never changes.
So it would seem, time is independent of change.

( sorry if I'm being snarky, had to put my cat to 'sleep' today )

My condolences also on the passing of your mate. In recent times, I had to get my 13.5 year old Rottweiler put down...great age, but still a hard distressing decision to make.

Back on track, I pinched these wise words [or words to that effect] from yourself in another "Time [again] " thread....Whether time is real or not,  it is more a philosophical question and physicists are not that concerned, other then the need to use the concept in our models etc.

I certainly accept it is real though for the reasons given.

Edited by beecee
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Condolences @MigL

Hi Time Traveller, hope you are well.

I think several people have already mentioned what time is assumed to be for most models in Science.  Time is another co-ordinate we need (in addition to the usual spatial co-ordinates) to specify where events happen in spacetime.  Any other property or nature of time is usualy less important than you would think,  or else the model you are working with will tend to specify what time needs to be and what properties it is assumed to have.

You (we) only need to have a passing knowledge of relativity to realise that a scientist's ideas of time have undergone a lot of changes in the years from Newton to Einstein.

None-the-less, time does seem important, very special and uniquely different to spatial co-ordinates for human beings.  There are scientists investigating the nature of time directly and many more in diverse fields that uncover a bit more information that seems to connect with our understanding of time.  There are some models that utilise geometry only, without any explicit time parameter and then an emergent property is exhibited which seems to behave like time.  These mesh fairly well with the ideas you mentioned in the OP.  In particular, in those geometric models you don't really need a thing called time because there are many other parameters you can use to form derivatives or calculate rates of change with respect to instead.

I have a suspicion this thread will echo many other discussions about time.  To make a slight change, I've got an interest in what we (human beings) use as an internal clock.  I wondered if we can get a Biologist to make a comment or post a link to explain the current best theory for how we are aware of time?  I assume it's some chemical reaction occuring in some group of cells and that it may proceed at a different rate according to factors like temperature.  Does time seem to pass at a different rate when you are hypothermic?         @CharonY Do you know a biologist who might post a link for this?  (or shall I take my chances with a search engine).

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1 hour ago, Col Not Colin said:

Does time seem to pass at a different rate when you are hypothermic?

Quote

In almost all cases, rate of subjective time increased when body temperature increased above normal, and decreased when body temperature was lowered below normal

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thanks iNow.  +1.

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2 hours ago, Col Not Colin said:

I have a suspicion this thread will echo many other discussions about time.  To make a slight change, I've got an interest in what we (human beings) use as an internal clock.  I wondered if we can get a Biologist to make a comment or post a link to explain the current best theory for how we are aware of time?  I assume it's some chemical reaction occuring in some group of cells and that it may proceed at a different rate according to factors like temperature.  Does time seem to pass at a different rate when you are hypothermic?         @CharonY Do you know a biologist who might post a link for this?  (or shall I take my chances with a search engine).

What you are looking for is called circadian rhythms. The controls are complex, it is not that temperature directly accelerates or changes the rhythm, though. It would wreak havoc with our metabolism. Rather it is thermoregulation within our body that affects circadian rhythms on the cellular level.

The archetypical master regulator is light, which sends signal via the brain but it also sends signals affecting thermoregulation (i.e. core temp increases with awakeness). Changes in core temperature the results in affects in the rest of your body, basically synching it up so that your whole body is within a given cycle of the rhythm.

Edit: as iNow noted, there is a temperature sensitive element to it, however it is synched up in a mostly unknown way (at least AFAIK, it is not my area of expertise) to the mostly temp insensitive core body temp rhythms. I.e. the overall cycle remains constant, at different temperatures, but the timing can be shifted.

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12 hours ago, Col Not Colin said:

I have a suspicion this thread will echo many other discussions about time.  To make a slight change, I've got an interest in what we (human beings) use as an internal clock.  I wondered if we can get a Biologist to make a comment or post a link to explain the current best theory for how we are aware of time?  I assume it's some chemical reaction occuring in some group of cells and that it may proceed at a different rate according to factors like temperature.  Does time seem to pass at a different rate when you are hypothermic?         @CharonY Do you know a biologist who might post a link for this?  (or shall I take my chances with a search engine).

!

Moderator Note

You should start a new thread to ask this question, rather than hijack this one.

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20 hours ago, Time Traveler said:

Human observer perceives the surrounding world usually through photons that have the maximum speed known to us .... which is not necessarily the maximum speed in the Universe.
Due to the perception of the environment through the photons we have this impediment to not observe in "'direct" but in "' resumption"

Changes are continuousos.....the speed of change can tend to 0

You may like my concept of how Time works

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28 minutes ago, michel123456 said:

You may like my concept of how Time works

!

Moderator Note

2. You have a thread for discussion of time, and you were told “This thread is now the only place where michel123456 may discuss topics related to time and relativity”

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6 hours ago, swansont said:

You should start a new thread to ask this question, rather than hijack this one.

Understood and apologies to the OP.  A new thread is not required, enough info on that side-line has already been supplied.  Thanks.

Returning to the original post:  It is interesting and highlights a natural human curosity about the nature of time.  The replies already illustrate the difficulty in finding an explanation that seems satisfactory and frequently involve abandoning one's original view of what time is supposed to be.  Hence, trying to understand what makes a human being aware of time passing seemed relevant for the purpose of finding a more satisfactory resolution  BUT this is not required and there is no need to take the discussion down that road.

---- End of side-line discussion, waiting for further input and direction ----

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