That space that we know so well

[michel123456]

Daniel posted this:

I move through space on a daily basis, I work with 3 Dimensional representations of space via computer programming on a near daily basis. So no, I have no problems with space. Why do you ask?

It is a fact that space is a familiar entity, in contrast with time which is so mysterious.

but do we really know what we think we know so well?
Here below some considerations and question marks.

_it has been established that there is a relation between space and time: any distance corresponds to a certain duration. We cannot get information from any distance in zero time because nothing can go faster than Speed Of Light. IOW in order to observe real simultaneity, information (EM radiation or any kind of other signal) should transfer at infinite velocity and this is not the case.

 

In short, everything that we observe in the space dimensions is in the past.

 

But not ALL the past.

 

An observer can only observe a slice of the past: the farthest the object the more in the past. There is a standard relation beween the distance to the observer and the past.

 

Putting aside for a while the cosmological expansion of space, the relation between distance and time is ruled by SOL. An object at 2 Light-Years distance is also (observed as it was) 2 years in the past.

 

that being established, here is the first question about this well-known space:

 

Q1_where is that object that lies at 2 LY distance and 3 years in the past? How come that we cannot observe such an object ?

Edited December 22, 2012 by michel123456

[elfmotat]

We observed it last year.

[michel123456]

 

We observed it last year.

 

No.

Could we last year observe an object that we cannot observe today?

Did it dissapeared from observation just because time passes by ?

Edited December 22, 2012 by michel123456

[swansont]

 

No.

Could we last year observe an object that we cannot observe today?

Did it dissapeared from observation just because time passes by ?

 

If it was moving, then it is at a different location. If it's stationary, then we can still observe it, with a signal that was generated 2 LY ago.

[michel123456]

 

If it was moving, then it is at a different location.

If it's stationary, then we can still observe it, with a signal that was generated 2 LY ago.

 

We can observe an object A that is 2 LY away. This object is observed today in a situation as it was 2 years ago.

 

Last year, the same object A that was 2 LY away was observed in the situation as it was 2 years before.

 

And so on in the past, and in the future we will see this object A that is 2 LY away. The object A will not dissapear from sight just because time passes by. That happens because time passes by for us and for the object A as well.

 

BUT we cannot TODAY observe an object B that is 2 LY away in the situation as it was 3 years ago. That cannot happen today, and that could not happened yesterday, nor last year, nor in the future.

 

The delay must match the distance in order for an object to be observable.

 

 

 

 

 

[swansont]

 

We can observe an object A that is 2 LY away. This object is observed today in a situation as it was 2 years ago.

 

Last year, the same object A that was 2 LY away was observed in the situation as it was 2 years before.

 

And so on in the past, and in the future we will see this object A that is 2 LY away. The object A will not dissapear from sight just because time passes by. That happens because time passes by for us and for the object A as well.

 

BUT we cannot TODAY observe an object B that is 2 LY away in the situation as it was 3 years ago. That cannot happen today, and that could not happened yesterday, nor last year, nor in the future.

 

The delay must match the distance in order for an object to be observable.

 

 

Yes. Unless you take a picture. It didn't disappear, though, it's just that d = ct

[elfmotat]

 

No.

Could we last year observe an object that we cannot observe today?

Did it dissapeared from observation just because time passes by ?

What are you talking about? It did't "disappear," it's just older now. You asked how we can observe three year-old objects located two light-years away from us. Of course the light from the object that reached us a year ago fits the bill. Signals made of something other than light would do the trick as well. If you had a signal made of massive particles that traveled at 2/3 light speed, it would reach us in three years from a location two light-years away.

 

Your question is rather strange by the way. It's similar to asking, "I know that when I look at my friend I'm seeing him slightly in the past. How come I can't see him even further in the past."

Edited December 22, 2012 by elfmotat

[michel123456]

What are you talking about? It did't "disappear," it's just older now. You asked how we can observe three year-old objects located two light-years away from us. Of course the light from the object that reached us a year ago fits the bill. Signals made of something other than light would do the trick as well. If you had a signal made of massive particles that traveled at 2/3 light speed, it would reach us in three years from a location two light-years away.

 

Your question is rather strange by the way. It's similar to asking, "I know that when I look at my friend I'm seeing him slightly in the past. How come I can't see him even further in the past."

(bolded mine)

Yes, exactly. And how come I can't see him in the present, and why I can't see him as he was 10 years ago, and why I can't see myself as I was yesterday. All that kind of silly questions.

 

Because if I had a friend here next to me but 10 years ago, I wouldn't be capable of observing him. Time acts as a distance. And ONLY when the time-distance (the duration, the delay) corresponds to the spatial distance, then and only then the object is (directly) observable.

 

And yes you are correct, if you had a signal made of massive particles that traveled at 2/3 light speed, it would reach us in three years from a location two light-years away.

 

Do you have any example of such signal in mind ?

 

 

 

 

Edited December 22, 2012 by michel123456

[elfmotat]

(bolded mine)

Yes, exactly. And how come I can't see him in the present, and why I can't see him as he was 10 years ago, and why I can't see myself as I was yesterday. All that kind of silly questions.

 

Because if I had a friend here next to me but 10 years ago, I wouldn't be capable of observing him. Time acts as a distance. And ONLY when the time-distance (the duration, the delay) corresponds to the spatial distance, then and only then the object is (directly) observable.

 

You've pretty much answered your own question then, haven't you?

 

 

 

 

And yes you are correct, if you had a signal made of massive particles that traveled at 2/3 light speed, it would reach us in three years from a location two light-years away.

 

Do you have any example of such signal in mind ?

 

You could use anything. You could launch electrons at 2c/3 for example.

[swansont]

(bolded mine)

Time acts as a distance. And ONLY when the time-distance (the duration, the delay) corresponds to the spatial distance, then and only then the object is (directly) observable.

 

IOW, spacetime is four-dimensional.

[michel123456]

_{the question remains unanswered:}

 

_{Q1_where is that object that lies at 2 LY distance and 3 years in the past?}

 

_{it is somewhere out there but}

_{_We know that it is not (directly) observable today.}

 

_{_It was not (directly) observable last year because objects do not disappear from one year to another. IOW we could not take picture of it.}

 

_{Where is it?}

Edited December 23, 2012 by michel123456

[swansont]

It' a nonsensical question. d = ct

You are specifying two different distances in spacetime. You can only occupy one.

[michel123456]

It' a nonsensical question. d = ct You are specifying two different distances in spacetime. You can only occupy one.

I don't understand your argument.

Spacetime is full of objects & events. An object situated at 2 LY from us and 3 yearsis an example of a random object in the past that can rxist (or could have existed). We cannot directly observe such an object. So, where is it ? Or, if you prefer, where are all those random objects that do not lie at the exactly corresponding distance and time that make them observable by us,

Edited December 23, 2012 by michel123456

[swansont]

You are asking why we don't see an object in two places at once. Why would we?

[ACG52]

An object situated at 2 LY from us and 3 yearsis an example of a random object in the past that can rxist (or could have existed). We cannot directly observe such an object.

 

But we already did observe it one year ago. We observed it, so it exists.

[michel123456]

You are asking why we don't see an object in two places at once. Why would we?

 

i am asking where is that object that lies 2 LY from us and 3 years in the past. That is only 1set of coordinates of a single object.

 

 

 

 

 

 

 

But we already did observe it one year ago. We observed it, so it exists.

 

 

 

If we observed it last year (we took a picture of it) and we cannot observe it today it must have disappeared in the meanwhile, isn't it? Where is it?

Edited December 23, 2012 by michel123456

[ACG52]

It's still there, but now it's one year in our past, and we can't observe our own past from the present. That's because the temporal dimension appear to have only one degree of freedom, forward in time.

[michel123456]

It's still there, but now it's one year in our past, and we can't observe our own past from the present. That's because the temporal dimension appear to have only one degree of freedom, forward in time.

But this object is in space.

Out there, around us.

Inobservable.

 

Hidden in time..

[ACG52]

Hidden in time..

 

 

 

Do you think that the object at 2 lys and 3 years ago is a seperate and distinct object from the one at 2 lys and 2 years ago?

[swansont]

i am asking where is that object that lies 2 LY from us and 3 years in the past. That is only 1set of coordinates of a single object.

 

But d = ct, so you have specified an object that is both 2 LY and 3 LY away. d and t are dependent on each other, meaning you don't have two variables, you have one, so there is only one solution.

 

 

If we observed it last year (we took a picture of it) and we cannot observe it today it must have disappeared in the meanwhile, isn't it? Where is it?

 

We do observe it today.

[michel123456]

 

But d = ct, so you have specified an object that is both 2 LY and 3 LY away. d and t are dependent on each other, meaning you don't have two variables, you have one, so there is only one solution.

 

 

 

We do observe it today.

What we observe today is an object 2LY away and 2 years in the past.

 

are you saying that an object 2 LY away and 3 years in the past does not exist (has never existed) ?

Edited December 24, 2012 by michel123456

[elfmotat]

Did you read what he said? He said that when considering light signals, picking a value for d or t immediately specifies the other. They aren't independent variables.

[michel123456]

d=ct is a condition in order to be observable (directly).

 

One can pick Earth's own past that corresponds to an object (an event) that is zero LY away and 3 years in the past. It is (was) something very real that doesn't correspond to d=ct. Earth's own past is not directly observable (I mean you cannot focus on earth's past when looking in your telescope).. The same goes for an object that is 2LY away and 3 years ago.

 

What's the problem?

Edited December 24, 2012 by michel123456

[swansont]

What we observe today is an object 2LY away and 2 years in the past.

 

are you saying that an object 2 LY away and 3 years in the past does not exist (has never existed) ?

No. Exist and observe are not the same thing.

 

d=ct is a condition in order to be observable (directly).

 

One can pick Earth's own past that corresponds to an object (an event) that is zero LY away and 3 years in the past. It is (was) something very real that doesn't correspond to d=ct. Earth's own past is not directly observable (I mean you cannot focus on earth's past when looking in your telescope).. The same goes for an object that is 2LY away and 3 years ago.

 

What's the problem?

And you cannot observe an object on the earth a year in the past.

[michel123456]

And you cannot observe an object on the earth a year in the past.

Right.

Because the object is inside the past light cone.

Edited December 24, 2012 by michel123456