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Jacques

Is space-time something ?

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Is space-time something or is it simply a background used to mesure thing ?

At first, I was thinking that it was just a mathematical construct used as a background to mesure thing, but now I am not so sure. Spacetime has some property permetivity and permeability. Also it can be bent, it can be draged by spninning body and may have other property that I am not aware off. That make me think that it is something, that it's not only a mathematical construct. Then the universe is composed of matter, energy and spacetime. If it is correct to think about spacetime as something then what is the difference with the old theorie of aether ?

Thanks in advance for your answers.:)

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No answer yet....

Just want to bring to your attention that if spacetime is something, then everything in the universe is connected, everything is in contact with everything. Does it make some sense ?

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I would say that it is something. Without it everything happens at once and in the same place.

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No answer yet....

Just want to bring to your attention that if spacetime is something, then everything in the universe is connected, everything is in contact with everything. Does it make some sense ?

 

Somewhat. Similarly all events would be connected, regardless of when or where they took place.

 

However they cannot all be causally connected as per relativity.

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The spacetime IS something. It has properties and etc, as you said. The mathematical construct was never pretend to be a spacetime, the mathematical construct is a mind MODEL of spacetime.

 

There are no principal differences between modern spacetime and old aether. The differences are particular, i.e. the specific properties of the thing named spacetime and the properties of the thing, named aether, are different.

 

Old aether was a gas, or liquid, allowing one to describe every physic law via the laws of hydro- or aero- dynamics. These attempts were failed. Modern spacetime has no (or nearly no) liguid or gas properties.

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I agree.

 

The main difference between modern spacetime and old aether is that latter is 3-dimensional, while first is 4-dimensional.

 

If you mathematically constrcut a 4-dimensional medium of any kind, you will see, that it differs from normal medium. The main reason of this is that one get to another areas of this object with time. Maybe you can't MOVE across this medium because it can have invariant, i.e. independant of moving, properties.

 

This difference is big, but I treat it as not principal, because it is simply adding one dimension.

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Is space-time something or is it simply a background used to mesure thing?

 

I guess the question is something like, "Are space and time real?" Well, one way of answering it would be with other questions like, is smell real? Is sound real? Sound is an experience associated with the sensory inputs that our ears receive. It is a congnitive representation of those inputs. There is nothing real about the subjective experience of sound; only the sensory inputs can be thought of as real. Similarly, space is (by and large) a representation of the light inputs to our eyes. Is it real? You be the judge! :)

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Is space-time something or is it simply a background used to mesure thing ?

At first, I was thinking that it was just a mathematical construct used as a background to mesure thing, but now I am not so sure.

 

One of the issues that many people realize when it comes to attempts at quantum gravity is that the concept of some background spacetime really doesn't make much sense. In a limited sense, and mathematically, it could be technically treated as such, but there doesn't seem to be a way to from first principles distinguish any particular choice of background.

 

What would be logical basis be for choosing a specific background?

 

if spacetime is something, then everything in the universe is connected, everything is in contact with everything. Does it make some sense ?

 

I think it makes sense. Spacetime can be identified with the connections or relations themselves. Spacetime IS the abstraction of relations. If the relations are unclear of chaotic, so is spacetime. Relations themselves can be thought of as correlations.

 

In that sence, they way I see it, the one sensible choice of reference that comes to mind is chaos, or zero information. Because this can IMO be philosophically quite well motivated, without need to rely on ad hoc stuff. This way spaces can intuitively be understood to emerge out of chaos as relations between whatver patterns and objects we start to distinguish become more and more confident.

 

/Fredrik

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In the everyday world, and in the classical physics domain these relations that sort of define spacetime are so confident that it appards almost rigid and "classical". In such case, the treatment of the spacetime as a kind of background is sufficently accurate. I think this humans live in this domain, the human "common sense" sometimes have hard to even imagine that the frames of references that we thought to be rigid are in fact not so.

 

If we go down in the confidence scale, at some point the uncertainy in our references are so massive that the sense of som of them them start to break down. And at some point we simply throw them away.

 

What is the use for a meter stick that only gives close to random readings anyway. You might as well throw it away and say that the concept of distance is really uselss, or close to useless.

 

/Fredrik

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Spacetime has an existence of its own. It is the invariant part of the inseparable union between space and time. Spacetime is therefore a real entity. It reveals its existence, in no uncertain term, when we deal with relativistic situations. This is a consequence of our acceptance of the absolute status of the velocity of light.

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It really depends on what you mean by 'something'. Is a mathematical equation 'something'? Is the colour green 'something'?

 

Space-time is intimately linked to the notion of events, and is in some sense a property of these events. The metric (space-time if you like) tells us how to define a 'distance' between two events (in both space and time). And this distance is important for physical law. As such, the metric is a property of the events itself, so it doesn't really exist on its own (or rather, its independent existence would be meaningless).

 

Warping space-time is in effect, warping the rule by which we measure distance. So if you regard a rule as 'something' then spacetime is 'something'.

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Space-Time is abstract. It is like the imaginary lines in a globe we call latitudes and longitudes. It is difficult to perceive it physically but I conceived it this way - Space-time is that invisible canvass where the observable Universe is painted, except a painting is a "still picture' while the Universe is not. Space-time sometimes distorts our senses of sight and time.

Gravity and Space-Time:Related to Each Other

Edited by Sirjon

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I guess the question is something like, "Are space and time real?" Well, one way of answering it would be with other questions like, is smell real? Is sound real? Sound is an experience associated with the sensory inputs that our ears receive. It is a congnitive representation of those inputs. There is nothing real about the subjective experience of sound; only the sensory inputs can be thought of as real. Similarly, space is (by and large) a representation of the light inputs to our eyes. Is it real? You be the judge! :)

 

 

Smell is real and is the sensory perception of particles.

 

Sound is real, it is the sensory perception of the vibration of air. Sound is a form of energy. Air is made of particles, atoms and such.

 

The experience of sound is objective, something happens in the physical universe and our senses detect this occurence. Our senses are at the effect point of what occurs in the physical universe.

 

All of our senses are adapted to percieve the world around us, either through the motion of particles or waves. All of our senses percieve those motions caused by real physical things that are some form of energy.

 

 

Be specific in your answer. Do you think space and time are real physical things that are some form of energy or not?

 

I say both space and time are concepts of man. Neither are real things that exist as an enity in the physical universe.

 

Why don't you come out and take a stand. What is your understanding of space and time?


Merged post follows:

Consecutive posts merged
Space-Time is abstract. It is like the imaginary lines in a globe we call latitudes and longitudes. It is difficult to perceive it physically but I conceived it this way - Space-time is that invisible canvass where the observable Universe is painted, except a painting is a "still picture' while the Universe is not. Space-time sometimes distorts our senses of sight and time.Gravity and Space-Time:Related to Each Other

 

 

This sounds like you think that space-time is a physical thing.

 

How would someone percieve physically this thing called space-time? Through our eyes as light reflects off it?

 

Touch?

 

Percieve how?

 

Are you being literal when you say that space-time is an invisible canvas?

 

An actual canvas that does not reflect light? Instead of giving a concept of space-time why not just give the scientific definition of space-time.

 

What does science say space-time is?

 

 

If you think that space-time distorts our sight that would mean that this thing has the ability to redirect light, that means that it is made of something either particles or E/M waves. Science does not say space-time is a physical thing.

 

You are not using science. Please stick to science.

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Sight and sound are the same dimension. The little bit of dark matter that exsists within our atmosphere(probably in the nitrogen molecule) allows for sound to have such a consistant property . everything we see is made up of sound . The universe was created with words ....blah blah blah

that tree in the forest doesn't make a sound if no one is around to see it.

sound cannot exsist in a vacuum. The sound of the sun's energy is felt and heard in wave form...

 

>:D

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Sight and sound are the same dimension. The little bit of dark matter that exsists within our atmosphere(probably in the nitrogen molecule) allows for sound to have such a consistant property . everything we see is made up of sound . The universe was created with words ....blah blah blah

that tree in the forest doesn't make a sound if no one is around to see it.

sound cannot exsist in a vacuum. The sound of the sun's energy is felt and heard in wave form...

 

>:D

 

o.O

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