Suppose that I am looking in my telescope to a distant star

[Strange]

I do note your earlier comment on the size of the cat (30 cm). Position (and physical extent) is measured in 3 dimensions, so the cat (an assembly of atoms, and what they're made of) has extent in height, width and depth. But time has a single dimension, so there's no equivalent "time extent" for the cat.

 

I'm not sure I would agree with that. The cat has an extent in time as well (from when it is created to when it ceases to exist).

[MigL]

The one and only theory we have which deals with time ( superficially I might add ) is GR.

GR tells us all space-time events are fixed in the manifold.

If a cat is at co-ordinate (x,y,z,t), then an observer in the local 'now' of this co-ordinate will see the cat.

If the observer is not in the local 'now' of the co-ordinate, he may not see the cat, because it may have moved, or it may not have been born yet, etc.

 

The only way 'your extended in time' makes sense is time has a 'granularity', such that there's a smallest unit of time and time proceeds in 'steps'.

Then the local 'now' would extend across that smallest time unit.

This begins to sound like a quantisation of space-time or a quantum gravity theory.

Unfortunately we don't have that yet

 

What we do have is 'classical' GR which says world lines and no extension in time for events.

Who knows maybe 'quantised' GR will provide a better understanding of time and that you were right all along.

 

Look me up when that happens and I'll gladly buy you dinner and drinks.

Edited November 23, 2014 by MigL

[swansont]

How does time behave then?

 

As I said, it's described by relativity.

 

Are there multiple cats along the time line?

Or is there only one single cat traveling through time and space?

I thought we were talking about time. You are talking about cats.

 

I don't understand why it is so difficult to answer this question. When it comes to space only, everyone agrees on what motion is: it is a change of coordinates.

But when it comes to time, then everything changes and people are ready to believe that objects do not change coordinates in time, instead they believe that objects remain on their coordinates.

I don't understand what you mean by "remain on their coordinates".

 

I find that absolutely grotesque.

 

And why should that matter?

[Mordred]

Correct

[Sensei]

Strange's answer is: he is looking (he was looking) at the Earth as it was 2 million years ago.

I am questionning Strange's answer. I say: how can we check that?

 

When we're sending command to distant satellite like Voyager, it's arriving after some time [math]t=\frac{d}{c}[/math] (d - distance).

And satellite is returning result after yet another time t, giving total delay between sending and receiving answer 2*t.

 

Astronauts that landed on the Moon had delay 2*1.21=2.42 to 2*1.35=2.7 seconds. When speaker talked with them, their answers were arriving with such delay.

[Mike Smith Cosmos]

...--- Yes! but . .... where am I , ..... And when am I .......-----?.?

 

---------------------------//-----------------/-----------------//----------------//----//---------------////////----

And who am I, for that matter ? And who are all you lot out there ? You are not cats !

 

Mike

Edited November 24, 2014 by Mike Smith Cosmos

[michel123456]

I do note your earlier comment on the size of the cat (30 cm). Position (and physical extent) is measured in 3 dimensions, so the cat (an assembly of atoms, and what they're made of) has extent in height, width and depth. But time has a single dimension, so there's no equivalent "time extent" for the cat. It's somewhere at some time. A nanosecond later, that one cat may be in the "same" place (depending on what measured against) or it might have moved. Its space and time coordinates can have changed. But it's still one cat.

But time has a single dimension, you are correct.

Your comment bothered me.

 

I was thinking:

1D is represented by a line.

When there is no space represented, an object can be drawn as a point on the time line.

If (if) the object had extent in time, it should be represented as a segment upon the line. In this case, When the segment travels upon the line, there is superposition and I am correct.

 

When one dimension of space is added then to the diagram becomes a space-time diagram.

If the object has extent in time, then it should be represented as a segment diagonal to the time line. When the segment travels along the time line, there is no superposition and I am wrong.(I mean even in the case the first "if" s correct.

 

When the second dimension of space is added then the diagram becomes complicated.

If the object has extent in time, then it should be represented as a surface (the surface of a cone). When the surface travels along the time line there is no superposition and I am wrong again.

 

When the third dimension of space is added then the diagram becomes impossible to be drawn on a sheet of paper. Anyway:

If the object has extent in time, then it should be represented as a volume. That is not a surprise. When the volume travels along the time line there is finally a superposition and I am right.

 

So the question is whether objects that take a certain volume have also a certain extent in time. Objects like cats, planets and galaxies.

Edited November 24, 2014 by michel123456

[swansont]

When the segment travels upon the line, there is superposition and I am correct.

 

Why would there be a superposition? That would occur only if a particular (x, t) represented two different points on the line segment.

[michel123456]

 

Why would there be a superposition? That would occur only if a particular (x, t) represented two different points on the line segment.

 

This is what I mean. In the following there is no space, only Time. The object is supposed to have extents in time, IOW it is not a point on the time line.

 

[imatfaal]

 

This is what I mean. In the following there is no space, only Time. The object is supposed to have extents in time, IOW it is not a point on the time line.

 

objects-extended-in-t.JPG

 

 

T₀ and T₁ are points on the time line - the object's manifestation is the collection of all these points between (and including) T₀ and T₁. The points are not blurred over time just as x and y coordinates in a cartesian system are not blurred over space; and similarly to a line existing between (x₁,y₁) and (x₂,y₂) an object can exist between time coordinates T₀ and T_1.

[swansont]

 

This is what I mean. In the following there is no space, only Time. The object is supposed to have extents in time, IOW it is not a point on the time line.

 

objects-extended-in-t.JPG

 

An extended object can be described as a set of points. None of the points overlap with each other — each has a unique (x,y,z,t) representation. No overlap. There's no issue with the object being at a spatial location at t₀ and t₁, because t₀ and t₁ are distinct. That's true for all times in between as well.

[michel123456]

 

 

T₀ and T₁ are points on the time line - the object's manifestation is the collection of all these points between (and including) T₀ and T₁. The points are not blurred over time just as x and y coordinates in a cartesian system are not blurred over space; and similarly to a line existing between (x₁,y₁) and (x₂,y₂) an object can exist between time coordinates T₀ and T_1.

I don't speak about the life of the object.

In the diagram, the object, at any instant, has an extent in time just as all objects have an extent in space.

For example, at T=0, say my head is at T=0 and my feet are at T=minus1.

[swansont]

I don't speak about the life of the object.

In the diagram, the object, at any instant, has an extent in time just as all objects have an extent in space.

For example, at T=0, say my head is at T=0 and my feet are at T=minus1.

 

In a system where special relativity works, those times are the same. In GR, you can map the times to each other. I'm not seeing how this causes any difficulties. Your head and your feet are at different spacetime coordinates. I'm not seeing what is "grotesque" about any of this.

[michel123456]

 

In a system where special relativity works, those times are the same. In GR, you can map the times to each other. I'm not seeing how this causes any difficulties. Your head and your feet are at different spacetime coordinates. I'm not seeing what is "grotesque" about any of this.

Yes I understand that.

You are correct, in real world there is no superposition.The diagram has been made to explain an impossible situation.

The grotesque arises when one consider that instead of sliding in time, the objects somehow "continues to exist" in the past. Some even consider that the object already exists in the future. My diagram show this situation, which provoques a superposition that we do not observe.

 

So the diagram is wrong, there is no superposition.

Which means that the object moves through time exactly as it moves through space. An object leaves a set of coordinates and go to another set of coordinates.

That is my point.

[Strange]

In the diagram, the object, at any instant, has an extent in time just as all objects have an extent in space.

For example, at T=0, say my head is at T=0 and my feet are at T=minus1.

 

At any instant the object is at a single point in time. I'm not sure how your head can be at a different time than your feet.

 

 

The grotesque arises when one consider that instead of sliding in time, the objects somehow "continues to exist" in the past. Some even consider that the object already exists in the future.

 

Ignoring the metaphysical question of whether the past and future object "exists", you are correct that the object has to be shown occupying every point along the time line (for the period it exists) because that is the only way you can show its location at that time (or, equivalently, at what time it was at each physical coordinate).

 

The fact you find this grotesque is not really relevant.

Edited November 25, 2014 by Strange

[swansont]

Yes I understand that.

You are correct, in real world there is no superposition.The diagram has been made to explain an impossible situation.

The grotesque arises when one consider that instead of sliding in time, the objects somehow "continues to exist" in the past. Some even consider that the object already exists in the future.

 

But how is that an issue of astronomy or cosmology, rather than one of metaphysics?

[Mike Smith Cosmos]

I am not grotesque , in fact I am quite cute !

 

I think I look the same on timeline , in the past , as I do now , and hopefully into the near future .

Not yet sure ?

 

Perhaps , that's not quite true . More like :- ....past time.......... .......... ........... Present

 

Then :- ..present ........... ......... ........ ......... ...... Future

Mike

Edited November 26, 2014 by Mike Smith Cosmos

[Ophiolite]

Mike, fewer catty comments, please.

[MigL]

"At any instant the object is at a single point in time"

Very profound Strange !

 

But at another instant, it is at another point in time ( +space )

If you were at location A one hour ago, the fact that you are at position B now does not mean you were no longer at position A one hour ago. Points ( events ) in space-time are fixed. GR being classical, past and future are just as 'real' as present. They just can't be accessed like spatial co-ordinates can.

 

Is it just me, or is English ( or any other language ) unsuited for describing the 'workings' of time ?

[Mordred]

In truth any lanquage other than the mathematics in unsuitable to dealing with the complexities than can crop up with a 4d coordinate system such as time. 3d causes its own complexities however adding a dimension that is difficult to visualize in terms of a length,width depth style tends to make imaginations run wild. The time dimension being a ckassic case. All too often the new learners wish to apply concepts and fundamentals far more off track than time being simply an observer mathematical measure of rate of change or duration of no change of one state of a system to another state of a system.

 

System is self explanatory. A good example is thermodynamic entropy changes. Even professional physicists try to utilize entropy as a form of clock ie arrow if time. However one key concept always applies time is and always will be dependant on the observer.

 

To a local observer time moves at a set rate.

To another outside observer looking at the first system time can flow different. This is the basis of GR. Fundamentally though it breaks down to a mathematical adjustment on measurements

Another good example on mathematical adjustments on measurements that is observer dependant (including measuring equipment) is redshift.

 

Time is easily imagined as having greater substance in much the same way as the term spacetime. If you look at the true meaning of spacetime. It is simply any geometric model that includes the time component. In other words nothing more than 1d 2d or 3d space with a measure of change or duration "time"

[Mike Smith Cosmos]

In truth ......

 

Time is easily imagined as having .... greater substance .... ..in much the same way as the term spacetime. If you look at the true meaning of spacetime. It is simply any geometric model that includes the time component. In other words nothing more than 1d 2d or 3d space with a measure of change or duration "time"

.

.

. Does this then invoke the Schreoniger cat in a box model .. Applied to my six cat , possibilities .. Namely we can only really " know " If we " observe " by opening the box " by observation " ?

 

Eeek ! Maybe we kill the cat by observation ! Maybe we do not !

 

Mike

Edited November 26, 2014 by Mike Smith Cosmos

[Mordred]

In a sense how we we review relativity and redshift relies upon our interpretation of the data. Dang Schrodinger

[Ophiolite]

Is it just me, or is English ( or any other language ) unsuited for describing the 'workings' of time ?

At the moment, yes.

[Strange]

"At any instant the object is at a single point in time"

Very profound Strange !

 

But at another instant, it is at another point in time ( +space )

 

Thank you, thank you.

 

But I think we can all agree that at any instant it is not extended in time.

[Mike Smith Cosmos]

 

Thank you, thank you.

 

But I think we can all agree that at any instant it is not extended in time.

 

I think my non lingual , Pictorial illustration of the Cats shows this well. The ONLY CATS that look like a cat are in the present. .Future cats are hoped for, and past cats are ,mere traces , or memories. The Present , for the cat is now. One Point . The Present .

 

Mike