If there is no end to the space

[michel123456]

(..)

The unification of space and time is exemplified by the common practice of selecting a metric (the measure that specifies the interval between two events in spacetime)

such that all four dimensions are measured in terms of units of distance

: representing an event as (x0,x1,x2,x3) = (ct,x,y,z) (in the Lorentz metric) or (x1,x2,x3,x4) = (x,y,z,ict) (in the original Minkowski metric)[k] where c is the speed of light. The metrical descriptions of Minkowski Space and spacelike, lightlike, and timelike intervals given below follow this convention, as do the conventional formulations of the Lorentz transformation.

 

http://en.wikipedia.org/wiki/Spacetime

 

The speed of light converts between units of time and units of distance.

 

 

So what is the space-time interval between 2 events on Earth and the Sun, in units of distance?

 

You mentioned in your previous post:

8.3 minutes

zero

10 minutes

five and one half Light-minutes

5.5 minutes

 

You see, I am dumb. I need just one number. In units of distance, since your last reply has reduced the choices.

 

5.

Edited February 25, 2011 by michel123456

[Sisyphus]

So what is the space-time interval between 2 events on Earth and the Sun, in units of distance?

 

You mentioned in your previous post:

8.3 minutes

zero

10 minutes

five and one half Light-minutes

5.5 minutes

 

You see, I am dumb. I need just one number. In units of distance, since your last reply has reduced the choices.

 

5.

 

Since it seems that Iggy is not here at the moment:

 

The spacetime interval between an event now on Earth and an event on the Sun 8.3 minutes in the past or future as measured in our rest frame is zero.

 

The spacetime interval between an event now on Earth and an event on the Sun 10 minutes in the past or future as measured in our rest frame is 5.5 light-minutes, or 5.5 minutes, depending on how you want to look at it, those being equivalent measures of spacetime. An observer traveling at a constant velocity such that they are present for both events will experience 5.5 minutes of time in between them.

[michel123456]

Zero what? Zero seconds or zero metres?

 

You wrote:

 

"The spacetime interval between an event now on Earth and an event on the Sun 10 minutes in the past or future (...) is 5.5 light-minutes, or 5.5 minutes depending on how you want to look at it (...)"

 

 

I feel realy stupid now. 10 minutes are....5,5 minutes. I miss something. But i don't want answer in units of time any more. Now I need distance.

 

You are answering in units I am not very familiar with.

 

5.5 minutes is time,

5.5 light-minutes is distance. How much?

 

4.

Edited February 25, 2011 by michel123456

[Iggy]

Thank you, Sisyphus.

 

You see, I am dumb. I need just one number.

 

I don't believe you are dumb.

 

There many conceivable events on the earth and sun. I gave two examples rather than one just to be thorough. I should also give a space-like interval... The space-time interval between an event on earth now and another on the sun 6.6 minutes from now (as measured in our frame) is roughly 5 and a half light-minutes. Physically, this means that a ruler stretched between the earth and sun will measure 5.5 light-minutes between events if that ruler is in a reference frame where the two events are simultaneous.

 

I've given three examples. The space time interval in each case is the distance between events in spacetime that all frames of reference agree on. If you insist on having just one number then just pick any of the three examples.

 

I feel realy stupid now. 10 minutes are....5,5 minutes.

 

That is correct. Between the events in our frame of reference there are 10 minutes. In the frame of reference where a clock intersects both events (the clock moves between the earth and sun) it measures 5.5 minutes. It is roughly 5.5. I did it without a calculator.

 

5.5 light-minutes is distance. How much?

 

http://www.google.com/search?q=light+minute

[Sisyphus]

Zero what? Zero seconds or zero metres?

 

Zero spacetime interval, of which seconds and meters are both measures. For simplicity, let's just say zero light minutes.

 

I feel realy stupid now. 10 minutes are....5,5 minutes. I miss something.

 

Yes. In our rest frame, it is an event 10 minutes in the future in time and 8.3 light minutes distant in space. In other frames of reference, those values will be different. The spacetime interval between them is about 5.5 light minutes - this value is independent of reference frame.

[michel123456]

1 light minute = 17 987 547.5 kilometers

 

5,5 light minute = 98931511,25 kilometers. Which is a spacetime interval between events 10 minutes in the future in time and 8.3 light minutes distant in space (translation 149296644,25 km)

 

Owl gave the value:

 

"The average distance* between the sun and the earth is 149 million kilometers"

 

which is the distance* measured from our frame of reference, here on Earth.

 

Do you say that 98931511,25 kilometers is the "invariant" value of the spacetime interval on which all FOR will agree on?

 

*distance, not spacetime interval.

 

3

[Iggy]

1 light minute = 17 987 547.5 kilometers

 

5,5 light minute = 98931511,25 kilometers. Which is a spacetime interval between events 10 minutes in the future in time and 8.3 light minutes distant in space (translation 149296644,25 km)

 

Owl gave the value:

 

"The average distance* between the sun and the earth is 149 million kilometers"

 

which is the distance* measured from our frame of reference, here on Earth.

 

Do you say that 98931511,25 kilometers is the "invariant" value of the spacetime interval on which all FOR will agree on?

 

*distance, not spacetime interval.

 

3

 

Yes. If two events are separated by 149 million kilometers and 10 minutes in our reference frame then the space time interval will be 5.5 light-minutes or 98931511 kilometers. All other frames of reference will find the same interval for those two events. They will measure different values of space between the events and different values of time between the events, but all those other frames of reference will find the same value for the invariant space-time interval.

 

The distance between those events in space time is invariant.

[michel123456]

And

 

"The spacetime interval between an event now on Earth and an event on the Sun 8.3 minutes in the past or future as measured in our rest frame is zero" light minutes or zero kilometer, and all FOR will find the same spacetime interval for those two events.

 

Is that your answer?

 

 

2

[Iggy]

And

 

"The spacetime interval between an event now on Earth and an event on the Sun 8.3 minutes in the past or future as measured in our rest frame is zero" light minutes or zero kilometer, and all FOR will find the same spacetime interval for those two events.

 

Is that your answer?

 

 

2

 

Yes, that was my exact answer in post #121.

[michel123456]

I take that for an answer.

 

1.

 

That was fun.

 

What do you think, Owl?

 

 

 

In the meanwhile, I found this:

 

"

 

"Only its length L is intrinsic to the rod (shown in black); coordinate differences between its endpoints (such as Δx, Δy or Δξ, Δη) depend on their frame of reference (depicted in blue and red, respectively)." from wiki' universe

emphasis mine.

 

That is exactly what I said, what I understand Owl said, and what you denied.

Edited February 25, 2011 by michel123456

[Sisyphus]

I take that for an answer.

 

1.

 

That was fun.

 

What do you think, Owl?

 

 

 

In the meanwhile, I found this:

 

"

 

"Only its length L is intrinsic to the rod (shown in black); coordinate differences between its endpoints (such as Δx, Δy or Δξ, Δη) depend on their frame of reference (depicted in blue and red, respectively)." from wiki' universe

emphasis mine.

 

That is exactly what I said, what I understand Owl said, and what you denied.

 

Did you read what you linked to, michel? Don't just pick out key words. It's a description of an analogy. In this analogy, L is the spacetime interval. Length and duration are the x and y coordinates. Read the rest of that section, please.

 

0.

[Iggy]

That was fun.

 

Yes, It was Let's do it again.

 

In some random frame of reference the spatial distance between two events is 5 light-minutes and the time between them is 4 minutes. What is the distance between the events in spacetime that all frames of reference will agree on?

 

Are you up for working through the answer?

 

That is exactly what I said, what I understand Owl said, and what you denied.

 

Did you read that section of the wikipedia page?

 

http://en.wikipedia.org/wiki/Universe#Special_relativity_and_space-time

Edited February 25, 2011 by Iggy

[zapatos]

And those of us in the cheap seats enjoyed it too!!

[owl]

I have unfinished business with Iggy from a continuing Q&A (both ways) on the previous page... But... Michel asked what I think about this more recent interchange. Maybe my answer will also address some of the previous exchange.

 

In the first place, I am an old fart who has followed relativity since the transition from Euclidean to non-Euclidean geometry (yes, a bit after the fact!) and, as is well known here, I and others I've cited (some from the Interrnational Society for the Advanced Study of Spacetime) do not accept "space", "time" and "spacetime" for the "given-and-established" entities now central to relativity theory. It's all, "Well you clearly don't understand relativity. (No legitimate disagreement allowed!)

This does not mean that I debate, for instance the Lorentz equations but rather their interpretation. Differences in measurement do not mean that there are actual differences in lengths of rods or distances between bodies as objects in a cosmos existing independently from the anomalies of measurement (from different FOR perspective), as I've said many times here.

Enter "Philosophy of Science, Relativity Section." If space is 3-D volume, basically that "emptiness" in which all things and forces exist and operate... with no "end in sight," or even conceptually possible... Remember, before it became "something" which contracts, expands, has shape... curves, etc.),...

and "time" is not "something" either... just duration between any two *chosen* instants, Then...

 

The only factor in the actual 'dance' between earth and sun which makes the distance between them vary (as objects in an objective, not relative-to-measurement-and-lightspeed cosmos) is the elliptical orbit in which the distance varies from 91 to 94.5 (? or so) million miles. All the mind games of relativity do not make them move closer or further away from each other as objects in and of themselves (translation: "independent of FOR variations in measurement.")

 

NOW... Now on earth is the same "now" on the sun and everywhere. Now does not depend on lightspeed, though getting information from one place to another obviously does. If Now there is a solar flare of note, we will be able to see it 8.3 minutes from Now. This is because, in terms of distance, sun is 8.3 light minutes from earth... obviously! That changes only as above with position in orbit. Now is the ongoing present everywhere, having nothing to do with the signal delay and lightspeed constancy at the heart of relativity.

 

Philosophical/rhetorical question: Are we so human/measurement centered that we no longer credit the cosmos with an existence independent of observational perspective?

 

This is longer than enough for a single post, but maybe enough for y'all to "get my drift" maybe better than before.

Back later... still a lot more "bone to pick" with Iggy's condescending, Ultimate Truth, Relativity post(s).

[Sisyphus]

 

This does not mean that I debate, for instance the Lorentz equations but rather their interpretation.

 

 

NOW... Now on earth is the same "now" on the sun and everywhere.

 

These statements are contradictory. Events which are simultaneous in one reference frame are not simultaneous in any other reference frame. You are not just disputing an interpretation. Whether you realize it or not, you are disputing the demonstrable fact that relativity makes correct predictions.

 

Are we so human/measurement centered that we no longer credit the cosmos with an existence independent of observational perspective?

 

Nobody in this thread is making any such claim.

[Iggy]

still a lot more "bone to pick" with Iggy's condescending, Ultimate Truth, Relativity post(s).

 

I honestly apologize if you are offended by the condescending and patronizing nature of my posts to you. I think you need someone to be brutally honest. Without even a basic cliff-notes understanding of relativity, the way you disparage the theory can't be well founded.

[DrRocket]

 

Enter "Philosophy of Science, Relativity Section." If space is 3-D volume, basically that "emptiness" in which all things and forces exist and operate... with no "end in sight," or even conceptually possible... Remember, before it became "something" which contracts, expands, has shape... curves, etc.),...

and "time" is not "something" either... just duration between any two *chosen* instants, Then...

 

In general relativity, space is NOT a 3-D volume and time is NOT duration between two chosen events.

 

In fact, in general relativity, there is no such thing as space and no such thing as time. What there is is a 4-dimensional Lorentzian manifold, spacetime. The usual concepts of "time" and "space" the concepts that you clearly consider as absolute, are not absolute, but in fact are quantities that are applicable to the tangent space at a point, and not to the spacetime manifold itself.

 

The study of special relativity alone gives rise to confusion because a global decomposition, though not a unique such decomposition, into "space" and "time' is possible and is central to the presentation of special relativity in introductory textbooks.

 

The perspective of general relativity is needed to understand the real nature of spacetime.

 

This has nothing to do with any ridiculous philosophical pigeon-holing of thought (e.g. subjective realism), but rather with a theory the validity of which is based on real measurements -- and a great many such measurements.

 

The problem is quite clearly that, despite your protests to the contrary, you do not understand relativity. You don't begin to understand it. That is a condition that is relatively easily remedied.

 

What is not so easily remedied is that you don't understand that you don't understand.

[Spyman]

What is not so easily remedied is that you don't understand that you don't understand.

IMHO you just hit the head on the nail.

[owl]

The answer is "those facts are correct and true in earth's reference frame".

 

"Perspective" is inaccurate. Length varies with velocity.

 

I agree, and would add that even as purely philosophical views, they cannot be correct. Owl's views are not consistent with themselves making their validity impossible.

 

Owl, it is really very simple. If your view of space and time are correct then you solved this problem correctly:

 

But, the "correct" answer that you got conflicts with another view you have concerning the speed of light. The two views that you have are mutually exclusive. It is, therefore, impossible for your view of the world to be correct.

 

 

Until you can explain reality in a coherent way, you don't get to criticize others for their successful explanation. Space-time is an objective reality independent of various perspectives and frames of reference. Your philosophical objection is therefore wrong. Your view of the world is also shown to be illogical and wrong. All you have is handwaving and I don't think the cult members are going to pay attention to that for long.

Time to get back to old, unfinished business. The above post will do. I'll just refer to statements/paragraphs by order of appearence above.

 

1:Obviously. I contend also that they are "objectively correct," i.e., describing the space/distance between earth and sun as they are without the qualification, "for observer A, the distance between earth and sun is no longer... (take your pick of units/numbers on fact sheet previously quoted.)

 

2:Aside from compacting or stretching a rod physically, the statement, "length varies with velocity" though central to relativity theory, is no more cleary true (without any argument, or evidence, as stated above, than the statement, " a rod maintains an objective, as it is length regardless of velocity. (Your argument requires specifics, not just treatment as a given truth or axiom of relativity. We are back to basics here. Saying I am wrong does not make me wrong.)

 

3:Again, as above. Show me the argument.

 

4&5 can go together. They refer to my "solution" to Iggy's "test," as follows:

 

(Even I can do elementary math, but of course this another SR trick question since nothing can travel faster that lightspeed, which is 671 million miles an hour. So if I add the 540 million mph of the guy going away to my left onto the 540 million mph of the guy going away to my right... I get a billion and 80million mph.... which somewhat exeeds the universal speed limit.... so.... what is your point given that I know what SR means?)

 

You never specified your point. We both know SR sticks to the speed limit "C".

 

Just because one guy is going 540 million mph one way and another is going the same speed in the opposite direction does not mean that the speeds must be added together to give a speed exceeding "C."

If I fire a laser from my left and another in the opposite direction to my right, each travels, obviously, at lighgtspeed and each in opposite directions. There is no need or reason to combine speeds. They are independent and going in opposite directions.

 

But... big "but"... If I'm on a ship traveling at near lightspeed and fire the laser straight ahead, it can only gain the difference between the ship's speed and lightspeed. This is SR, and that is why I said that it is clear to me that light can not be "pushed" any faster than "c", truly a universal constant. I shared my speculations as to why that is previously. I also asked two questions, as yet unanswered in that regard (the nature of light.) Why does a laser recoil when fired, and why does the famous box of mirrors gain inertia when light is introduced to bounce around? If we are talking about the nature of light, as above, why not address these questions in the process, maybe to actually consider why light can not be pushed faster by a laser on a speeding ship.

(Whew! Long answer.)

 

6th and finally: I am presenting as coherently as I can, but your misunderstanding of what I say does not, as above, necessarily make me wrong. I requires specific debunking, to which I remain open, but "specific" does not mean repeating the primary "axiom" of relativity (may I call it that?)...

" Space-time is an objective reality independent of various perspectives and frames of reference."

Tell that to the esteemed members of the International Society for the Advanced Study of Spacetime. They have been working on it for years and have had several conferences on spacetime ontology, and they have not yet arrived at a consensus on its status as "an objective reality."

Such an asssertion, regardless of your unfounded certainty, does not mean you are correct in saying, "Your philosophical objection is therefore wrong."

That's six, which will do for now.

[michel123456]

Did you read what you linked to, michel? Don't just pick out key words. It's a description of an analogy. In this analogy, L is the spacetime interval. Length and duration are the x and y coordinates. Read the rest of that section, please.

 

0.

 

Wikipedia sucks.

I read

Consider the two endpoints of a rod of length L. The length can be determined from the differences in the three coordinates Δx, Δy and Δz of the two endpoints in a given reference frame

 

L2 = Δx2 + Δy2 + Δz2

using the Pythagorean theorem. In a rotated reference frame, the coordinate differences differ, but they give the same length

 

L2 = Δξ2 + Δη2 + Δζ2.

Thus, the coordinates differences (Δx, Δy, Δz) and (Δξ, Δη, Δζ) are not intrinsic to the rod, but merely reflect the reference frame used to describe it; by contrast, the length L is an intrinsic property of the rod. The coordinate differences can be changed without affecting the rod, by rotating one's reference frame.

from the link in wiki

 

On which anyone must agree. This is not an analogy, this is truth in Euclidian geometry.

 

And then

 

The analogy in spacetime is called the interval between two events

 

From this I understand that the analogy is the interval. Or I have to study grammar again.

 

I am sure that you read the sentence otherwise. It is ment that the rod is the analogy, I suppose. But then, how is it that you use an analogy stating that Length is "intrinsic" in order to explain that it is not, but that you must replace it with another supreme intrinsic value which is called the interval. You don't use a truth that anyone accept to destroy it in the next step.

 

Anyway.

 

--------------------------------------------

[Iggy]

1:Obviously. I contend also that they are "objectively correct," i.e., describing the space/distance between earth and sun as they are without the qualification, "for observer A, the distance between earth and sun is no longer... (take your pick of units/numbers on fact sheet previously quoted.)

 

 

4&5 can go together. They refer to my "solution" to Iggy's "test," as follows:

 

(Even I can do elementary math, but of course this another SR trick question since nothing can travel faster that lightspeed, which is 671 million miles an hour. So if I add the 540 million mph of the guy going away to my left onto the 540 million mph of the guy going away to my right... I get a billion and 80million mph.... which somewhat exeeds the universal speed limit.... so.... what is your point given that I know what SR means?)

 

Just because one guy is going 540 million mph one way and another is going the same speed in the opposite direction does not mean that the speeds must be added together to give a speed exceeding "C."

 

The statements contradict each other and you are not seeing why.

 

Get two metal rods that are each 540 million miles long. Lay one to your left, pointing to your left, and another to your right, pointing right. Send someone down the length of each rod at 540 million mph. After one hour each person will be at the end of each rod. Yes? Everyone will agree on this, yes?

Edited February 26, 2011 by Iggy

[michel123456]

Yes. If two events are separated by 149 million kilometers and 10 minutes in our reference frame then the space time interval will be 5.5 light-minutes or 98931511 kilometers. All other frames of reference will find the same interval for those two events. They will measure different values of space between the events and different values of time between the events, but all those other frames of reference will find the same value for the invariant space-time interval.

 

The distance between those events in space time is invariant.

 

@ Iggy.

 

Can you define any FOR that will give for any chosen events on Earth and Sun, a spacetime interval larger than 149 million kilometers? Lets say 200 billions kilometers?

 

 

Get two metal rods that are each 540 million miles long. (...)

 

Inconsciously, you agree with us.

Edited February 26, 2011 by michel123456

[Iggy]

@ Iggy.

 

Can you define any FOR that will give far any chosen events on Earth and Sun, a spacetime interval larger than 149 million kilometers? Lets say 200 billions kilometers?

 

Sure. In our reference frame (here on earth) the interval between an event on earth right now and another on the sun almost 8 days from now will be 200 billion kilometers.

 

Inconsciously, you agree with us.

 

Blimey! I didn't realize. It must be very unconscious.

Edited February 26, 2011 by Iggy

[michel123456]

Sure. In our reference frame (here on earth) the interval between an event on earth right now and another on the sun almost 8 days from now will be 200 billion kilometers.

 

Positive or negative?

[Iggy]

Positive or negative?

 

The quick answer is that it's arbitrary. It is a sign convention.

 

Did you consider my question?

 

Yes, It was Let's do it again.

 

In some random frame of reference the spatial distance between two events is 5 light-minutes and the time between them is 4 minutes. What is the distance between the events in spacetime that all frames of reference will agree on?

 

Are you up for working through the answer?

 

Knowing how to calculate the interval it would significantly cut down the questions regarding what the value is... or should I start a countdown

 

I explained very quickly how to find the interval in post 115 and I ME explained more in depth in #112.