Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Curious Cat on 01/10/2021 15:50:54

Title: What is TIME?
Post by: Curious Cat on 01/10/2021 15:50:54
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Title: Re: What is TIME?
Post by: Zer0 on 01/10/2021 17:28:23
There isn't Time...
There isn't Space..
Only SpaceTime.

Ps - let's just quietly Agree, to politely Disagree.
✌️
Title: Re: What is TIME?
Post by: chiralSPO on 01/10/2021 19:10:21
Time cannot be motion. That's just common sense  8)

The question of what time is, is a good one, and again, probably one you won't get a satisfying answer for.

The best one-line quip definition of time I've heard is:
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time is what keeps everything from happening at once.

Title: Re: What is TIME?
Post by: Origin on 01/10/2021 19:54:53
TIME is just The Internal Motion of Everything.
Nope, that's motion.
Title: Re: What is TIME?
Post by: Colin2B on 02/10/2021 09:26:17
The best one-line quip definition of time I've heard is:
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time is what keeps everything from happening at once.
And distance is what stops things being in the same place at once.

I am not talking about its internal physical co/motion but
something internal to the sub/atomic particles, themselves.
Like radioactive decay, is.
Radioactive decay is a process.
Intrinsic just means it’s not dependant on how much of a material you have or on external influences.

They say that the QS/AM is not caused by the particle actually spinning, around its axis,
for a number of reasons. They say it's an intrinsic property.
Well why I can't say the same, about time?
You wouldn’t call distance an intrinsic property. It’s just a measurement of the space between things. Similarly with time as @chiralSPO said.
Title: Re: What is TIME?
Post by: Just thinking on 02/10/2021 09:50:05
What is TIME?
Time is the passage of before now and later it is a reminder of our existence and the ager of everything.
Title: Re: What is TIME?
Post by: alancalverd on 03/10/2021 09:17:19
Chiral's "quip" is pretty close to a more formal and useful definition.

Time is what separates sequential events.

Some events are dependent and thus necessarily sequential: B cannot happen unless A has happened. These can be used to set a basis for measuring time, and our measurements get more consistent and useful as we find sequences governed by ever more constant conditions. Other events are independent or subject to less constant conditions but their sequence can be located on a time line established on the basis of constant-dependent events.
Title: Re: What is TIME?
Post by: Just thinking on 03/10/2021 09:40:25
Ye's, but/t, in my universe/model if there's no time or time stops, then nothing happens.
We have extra time now in Australia as daylight savings has just started.
Title: Re: What is TIME?
Post by: Colin2B on 03/10/2021 11:53:36
Ye's, but/t, in my universe/model if there's no time or it stops, then nothing happens.
That isn’t a unique feature of a model which includes time. It’s hard to think of a model where that isn’t true, although halc probably knows one.
Title: Re: What is TIME?
Post by: geordief on 03/10/2021 12:43:35
Is there a definition  or description of time as it applies to the time that is an integral part of spacetime?

What does the space part refer to and what does the time part refer to?

I think there is a well known quotation (by Minkowski?)  where he says that henceforth both time and space in the then accepted sense would be replaced by a kind of union between the two.

Can anyone flesh  that out at all?

Is the time in that quotation simply a reference to what clocks measure in moving frames of reference or was he driving at something else? Some physicality to the concept?
Title: Re: What is TIME?
Post by: Halc on 03/10/2021 12:56:48
Ye's, but/t, in my universe/model if there's no time or it stops, then nothing happens.
That isn’t a unique feature of a model which includes time. It’s hard to think of a model where that isn’t true, although halc probably knows one.
A block model has time, and yet time isn't something that 'goes', and events are not things that 'happen'. So the definition above begs not only a preferred reference frame, but also a preferred moment in time.
Title: Re: What is TIME?
Post by: alancalverd on 03/10/2021 13:05:33
Ye's, but/t, in my universe/model if there's no time or it stops, then nothing happens.
The you need a better model, because stuff happens, therefore time continues.
Title: Re: What is TIME?
Post by: Halc on 03/10/2021 13:17:17
Is there a definition  or description of time as it applies to the time that is an integral part of spacetime?
The definition Alan quoted above works quite nice for time as an integral part of spacetime, and it works for other interpretations as well. So it is a far better definition.

Quote
What does the space part refer to and what does the time part refer to?
There's the formula for interval in Minkowskian spacetime which defines the interval as t˛ - x˛ - y˛ - z˛.  Time is the positive components of that, and space is the negative components. You can rotate the four axes around in any orientation you like, even to the point of interchanging any one for any other and you'll still get one positive and four negative. For instance, in the interior of a black hole, the axes rotate enough that our t dimension becomes negative and one of the space dimensions (the radial dimension) becomes positive. That description cannot be done with a definition of time where things 'happen' and thus a model with flowing time is forced to deny the existence of black holes.

Quote
I think there is a well known quotation (by Minkowski?)  where he says that henceforth both time and space in the then accepted sence would be replaced by a kind of union between the two.
Yes. He showed that they're the same stuff. For instance, ontologically, if either exists, then the other does. Time, light space, became part of the universe instead of the universe existing in both (after a time, the big bang 'happened', and at a point in otherwise empty space into which it has since been expanding).

Quote
Is the time in that quotation simply a reference to what clocks measure in moving frames of reference or was he driving at something else?
This is another place where where F-C's definition falls apart. If there is an objective frame and some rate that a preferred moment advances from one moment to the next, then clocks don't measure it, as evidenced by a pair of clocks not reading the same value in the twins scenario. There is no possible device one can construct to measure the rate of advancement of the present, as F-C has acknowledged, and thus zero evidence that any such flow exists at all.

Such findings are largely why the theory of relativity laid serious doubt on the presentist model.
Title: Re: What is TIME?
Post by: Colin2B on 03/10/2021 17:57:17
A block model has time, and yet time isn't something that 'goes', and events are not things that 'happen'. So the definition above begs not only a preferred reference frame, but also a preferred moment in time.
Yes, that had slipped my mind, not that my mind has given it much deep think. I tend to envisage a 4D tube map with a 'you are here' pointer 😄
Title: Re: What is TIME?
Post by: geordief on 03/10/2021 19:40:20
The definition Alan quoted above works quite nice for time as an integral part of spacetime, and it works for other interpretations as well. So it is a far better definition
Thanks,I missed that.
Other events are independent or subject to less constant conditions but their sequence can be located on a time line established on the basis of constant-dependent events

Could I ask if you have any examples?

I had been  wondering whether all pairs of events are connected,either from A to B or from B to A depending on circumstance(eg I cannot influence my mother's early life but she could (and did?) mine-as a specific example of what I was assuming would be the general case)

To clarify the specific case above, if she took ,say 5 minutes extra to do the shopping on a day before I was born ,I am saying that that extra 5 minutes would have changed the course of the universe and my  life (and all others ) would be included in that changed universe.

So her shopping and my , say fit of coughing would be connected events  but only in the direction of her to me .

So to my mind all events in the universe are connected but sometimes only  in one direction.
Title: Re: What is TIME?
Post by: alancalverd on 04/10/2021 00:15:47
Quote from: alancalverd on Yesterday at 09:17:19
Other events are independent or subject to less constant conditions but their sequence can be located on a time line established on the basis of constant-dependent events

Could I ask if you have any examples?
The simplest "constant cause" sequence is a pendulum, which gives us a handy time base of, say, one second. A less-constant cause sequence is A: eating breakfast and B: wanting lunch: it's a biological function of all sorts of variables but we can plot both events on a time line measured by a pendulum clock or the bearing of the sun. The sequence of Conservative government - national catastrophe has been observed and recorded on a historical timeline but the events are allegedly independent.
Title: Re: What is TIME?
Post by: TommyJ on 09/10/2021 09:27:23
Isaac Newton presented a point in space and time separately. Meeting someone needs: address (3 - dimensional coordinates) and time - the fourth dimension.
After 200 years Albert Einstein merged spacetime as a 3-dimensional model. Without time as a 4th dimension.
And after 20 years more we’ve got the concept of ‘arrow of time’ by Arthur Eddington.

Arrow of time depending on the stuff in the universe, the microscopic matter and the configurations. Entropy started to grow and will continue to grow for the future.
Arrow of time gives us an impression that time passes, flows, and we progress through different moments.
Past is not more real than the future, the past is that we know more about (any book, memory, fossil, that we can look at) that we believe gives us reliable knowledge of the past. There are no history books written about the future.
We have different access to the past and the future.

A movement in time as in space would presuppose the possibility of moving backwards in time and remaining still in it.
But you cannot remain absolutely still in time (only in relation to some reference systems), and you cannot go back in time (until proven otherwise).

There is no ‘earlier’, ‘now’ and ‘later’. Clock is just doing the same thing over and over again. We might have lived in a universe with the existence of things that are doing the same thing over and over again in a predictable way, which is not taken for granted. Clocks are something that can measure a passage of time. And there are many clocks in the universe, showing different time to a distant observer.

There should not be a confusion of terms and concepts, while going through theories.
Title: Re: What is TIME?
Post by: Black hole on 15/10/2021 18:54:41
There isn't Time...
There isn't Space..
Only SpaceTime.

Ps - let's just quietly Agree, to politely Disagree.
✌️

Let's not ! Space-time is a measurement reference frame

Space exists independent of matter

Matter has a duration of existence , better known as time !