Is spacetime real?

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Offline mxplxxx

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Is spacetime real?
« on: 23/09/2016 06:24:53 »
Given we can't seem to go forwards or backwards in Spacetime, how likely is it that Spacetime is real?

It can be strongly argued that the past is just memories and the future is determined by the current state of the present. It seems likely that reality is a type of finite-state machine (as is a computer). A finite-state machine does not need the concept of time to perform. Things happen one after another. So why not reality?

It seems that the present changes state at the speed of light. But for anything that achieves light speed, the concept of time vanishes. So what does this mean for Spacetime?

Finally, if time is relative as Einstein suggests, it would seem that Spacetime is different for each object in the universe. This seems to indicate it is a mathematical concept only.
« Last Edit: 23/09/2016 09:14:10 by chris »

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Offline geordief

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Re: Is spacetime real?
« Reply #1 on: 23/09/2016 12:46:15 »
As I understand  this , spacetime is a mathematical model that allows us to make predictions concerning motion in space.

It is also the only theory to date  (apart perhaps from quantum mechanics) that allows us to make to same measurements of events anywhere at all  from any place ,time or circumstance  (barring singularities apparently which is where the theory falls off a cliff)

Whether "space time  is real " seems  to be a philosophical point of view from what I have gathered rather than a subject for physics at present.

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Offline mxplxxx

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Re: Is spacetime real?
« Reply #2 on: 24/09/2016 00:43:54 »
Thx for that interesting reply.

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Offline PmbPhy

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Re: Is spacetime real?
« Reply #3 on: 24/09/2016 01:31:02 »
Quote from: mxplxxx
Given we can't seem to go forwards or backwards in Spacetime, how likely is it that Spacetime is real?
Where did you ever get the idea that we can't go forward in time? That's most certainly not true. And the notion of real has no place in science. As Einstein wrote
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"The physical world is real." This is supposed to be the basic hypothesis. What does "hypothesis" mean here? For me, a hypothesis is a statement whose truth is temporarily assumed, whose meaning, however, is beyond all doubt. The above statement seems intrinsically senseless though, like someone saying "The physical world is a cock-a-doodle-do." It appears to me that "real" is an empty, meaningless category (draw) whose immense importance lies only in that I place certain things inside it and not certain others. It is true that this classification is not a random one ....... now I see you grinning and expecting me to fall into pragmatism so that you can bury me alive. However, I prefer to do as Mark Twain, by suggesting that you end the horror story yourself.
     Real and unreal seem to me like right and left. I admit that science deals with the "real" and am nonetheless a "realist." - Letter from Albert Einstein to Eduard Study (Sept. 25, 1918)
Spacetime is quite real. I'm very busy right now so I'll get back to this later as to why that is my contention. I'll address the rest of your post at that time.

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Offline mxplxxx

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Re: Is spacetime real?
« Reply #4 on: 24/09/2016 07:44:20 »
Great Scott, as the Doc in Back to the Future movies is wont to say, time-travel may disrupt the Spacetime continuum. We seem to be stuck in the present and can go neither forwards nor backwards in time.

There are lots of hints in our current knowledge of physics that says Spacetime isn't real. The major hint  is the speed of light which is a constant in Spacetime irrespective of the frame of reference it is measured in. Bosons, which move at the speed of light in a vacuum, do so apparently without any acceleration being involved. Impossible? Seemingly but physics has always ignored this fact which makes our current theories of reality pretty shaky.

It may be that the only thing that moves at the speed of light is the present. A boson in this scheme of things is just a fixed point in a space that is full of events approaching it at the speed of light. Spacetime may be much better understood as the state history of fixed points in space. 

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Offline PmbPhy

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Re: Is spacetime real?
« Reply #5 on: 24/09/2016 09:03:38 »
Quote from: mxplxxx
There are lots of hints in our current knowledge of physics that says Spacetime isn't real.
Where on Earth did you ever get the idea that any current knowledge says that spacetime isn't "real"? I know as a fact that no relativist would ever make such an assertion. I know that I wouldn't, that's for certain.

Quote from: mxplxxx
The major hint  is the speed of light which is a constant in Spacetime irrespective of the frame of reference it is measured in.
Huh?? What led you to believe such a thing, i.e. that the invariance of the speed of light implies that spacetime isn't "real"?

Quote from: mxplxxx
Bosons, which move at the speed of light in a vacuum, ...
Not necessarily. That some bosons, such as photons, move at the speed of light, it's not a defining property of bosons. For example: The W and Z bosons have mass. See: https://en.wikipedia.org/wiki/W_and_Z_bosons

The mass of the W boson is 80.3850.015 GeV/c2. The mass of the Z boson is 91.18760.0021 GeV/c2.

Quote from: mxplxxx
Bosons, which move at the speed of light in a vacuum,so apparently without any acceleration being involved. Impossible? Seemingly but physics has always ignored this fact which makes our current theories of reality pretty shaky.
Physics has never ignored such a problem because such problems don't exist. If you apply your argument to photons, which do move at the speed of light, there still isn't a problem because no acceleration is involved because photons are created already moving at the speed of light.

I'm sorry my friend but your understanding of physics is off and that's the reason for what you see as unsolved problems in physics.

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Offline mxplxxx

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Re: Is spacetime real?
« Reply #6 on: 25/09/2016 04:39:43 »
Has the speed of W and Z Bosons ever been measured?

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Offline evan_au

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Re: Is spacetime real?
« Reply #7 on: 25/09/2016 10:12:20 »
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Has the speed of W and Z Bosons ever been measured?
Their mass is known to be around W: 80 GeV/c2, and Z: 91 GeV/c2, so their speed is < c.

Their actual speed depends on how much momentum they were created with.

Their lifetime is about 3x10-25s, so even if they were created traveling at relativistic speeds, they would only travel an average of t x v < t x c = 3x10-25s x 3x108m/s = 9x10-17 meters, or about 1% of the diameter of a proton. (They are unlikely to travel more than the width of a hydrogen atom, even if the time dilation were extreme.)

In other words, they are so unstable that they decay before they can exit the proton beam to reach a detector that would measure their speed.

So in practice, the energy of the W or Z boson (and their speed) is estimated by adding up the energy of the decay products that do make it to a detector (and accounting for the loss of energy due to neutrinos, which are almost undetectable).

See: https://en.wikipedia.org/wiki/W_and_Z_bosons
« Last Edit: 25/09/2016 22:49:51 by evan_au »

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Offline mxplxxx

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Re: Is spacetime real?
« Reply #8 on: 25/09/2016 11:25:51 »
So, the answer is "no their speed has never been measured". So it could be c. Many physicist, it would seem, believe that photons also have mass. Physics is far less a cut and dried science than you would have us believe. Many of the old theories are being questioned in light of their inability to incorporate newly discovered phenomena (think dark matter) - not to mention their inability to describe gravity. Spacetime may just be one of many mathematical theories that can predict the future. Fixed, stateful points in space may just be another way of looking at Statetime. But it does have the advantage of treating space as a fluid which allows for propagation of particles in waves and allows quantum theory to be reformulated as a theory of fluid dynamics (https://www.wired.com/2014/06/the-new-quantum-reality/) . 

Actually, the idea of Spacetime as a continuum appeals. This introduces the possibility that Spacetime is eternal in nature with digital simulations of it being possible at smaller and smaller and larger and larger scales. Is quantum theory just a digital representation of Spacetime? Is a galaxy from the universes point of view a particle. Doe a photon have a TOE that includes particles smaller than itself.

.... but I am rambling!!!
« Last Edit: 25/09/2016 12:00:27 by mxplxxx »

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Offline puppypower

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Re: Is spacetime real?
« Reply #9 on: 25/09/2016 12:24:27 »
Space-time integrates the concepts of time and space, as though together they act as one thing. Propagation forward in time, is reference dependent, which implies time depends on position in space. At a given position in space, there is a certain configuration of matter and energy, which defines how time will propagate.

Theoretically, space and time can also act as independent things. For example, acceleration has the units of d/t/t, which is one part distance and two parts time. Acceleration has the units of space-time plus time. Space-time is more concerned with velocity; d/t. In Special relativity, the operating variable, for defining time and distance, is velocity; d/t. Say something quantum steps in distance, in zero time; electron transition, in this case, this can be modeled as extra distance potential in space-time.

The idea of separate time and distance is my own theory. It is based on an observation that has been around since before the birth of Albert Einstein and the other fathers of modern physics. This observation is from photography and is called motion blur.

Motion blur, occurs in photography, when the shutter speed of the camera is slower than the action speed. Since a still photo will stop time, the difference in speed; delta (d/(t=0)) is expressed as uncertainty in distance; motion blur. Motion blur creates the impression of motion, even with time stopped, because  time (delta speed) is conserved, and expressed as uncertainty in distance. Time and space are interchangeable at some level, allowing extra time or distance potential to be expressed as special cases in space-time.


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Offline Atkhenaken

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Re: Is spacetime real?
« Reply #10 on: 25/09/2016 15:27:20 »
Time is just an intellectual device which we have created to measure spin rotations. You can assign numbers to represent time in a mathematical sense though. The problems begin when you forget that the numbers which represent time are not spacial in nature. Its when you mistake time numbers for distance numbers that you really get into a fuddle. This is what a lot of physicists have done in the past. Thus, they come up with intellectual ideas such as space/time which is a logical impossibility.

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Offline geordief

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Re: Is spacetime real?
« Reply #11 on: 25/09/2016 16:06:07 »
Time is just an intellectual device which we have created to measure spin rotations. You can assign numbers to represent time in a mathematical sense though. The problems begin when you forget that the numbers which represent time are not spacial in nature. Its when you mistake time numbers for distance numbers that you really get into a fuddle. This is what a lot of physicists have done in the past. Thus, they come up with intellectual ideas such as space/time which is a logical impossibility.
what is a spin rotation?

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Offline Atkhenaken

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Re: Is spacetime real?
« Reply #12 on: 26/09/2016 01:44:39 »


what is a spin rotation?

A rotation of a planet or a clock. The clock being a device which mimics the rotation of a planet.

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Offline geordief

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Re: Is spacetime real?
« Reply #13 on: 26/09/2016 08:13:32 »
I understand that time  will also measure processes that do not involve such movements  . The rate of decay of subatomic particles is an example. Nothing moves  and yet the process is regular and that is how we time the movements of other things.

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Offline evan_au

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Re: Is spacetime real?
« Reply #14 on: 26/09/2016 11:09:06 »
Quote from: Atkhenaken
The clock being a device which mimics the rotation of a planet.
The reference clock used for scientific purposes is an atomic clock, which does not involve rotation, and is not directly related to the rotation of a particular planet.

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Offline PmbPhy

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Re: Is spacetime real?
« Reply #15 on: 26/09/2016 12:42:54 »
Has the speed of W and Z Bosons ever been measured?
I'm sure that it has, even if indirectly.

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Offline PmbPhy

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Re: Is spacetime real?
« Reply #16 on: 26/09/2016 12:47:40 »
Quote from: mxplxxx
So, the answer is "no their speed has never been measured". So it could be c.
That's hardly a logical conclusion. One doesn't assume something can be true merely because it hasn't been observed. E.g. I'm 100% certain that my cat cannot travel at the speed of light even though I've never tried an experiment to deduce it.

Quote from: mxplxxx
Many physicist, it would seem, believe that photons also have mass.
That is quite incorrect. If a physicist said that a photon has mass then they're not talking about its proper mass (aka rest mass), they're talking about its relativistic mass.

Quote from: mxplxxx
Physics is far less a cut and dried science than you would have us believe.
That's quite incorrect. What are you basing the claim on?

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Offline geordief

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Re: Is spacetime real?
« Reply #17 on: 26/09/2016 13:23:38 »


All sub-atomic particles spin at the speed of light. How can something decay if it is not spinning? Impossible!

Have you a reference for that.? I have heard of the term "spin" when applied to sub atomic particles but I think it is said to be different from what we normally think of as "spin".

I am not sure it means these particles are in motion  but I cannot say as I have not studied this area.

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Offline geordief

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Re: Is spacetime real?
« Reply #18 on: 26/09/2016 13:49:56 »


They must be spinning. Otherwise how can they decay if they are not spinning? Its just a matter of logical certainty.

I prefer to rely on interpretations based on observations rather than anyone's  conclusions based on "logical certainty".

You haven't provided me with any reference to particles "spinning at the speed of light" as I requested  . Did you make that up ,then?

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Offline geordief

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Re: Is spacetime real?
« Reply #19 on: 26/09/2016 16:34:15 »
Apologies . I thought spin  was one of those made up names like "charm"  and "strange".

I had been told elsewhere  that no motion was involved in radioactive decay. I have no idea if spin is involved in that  process and what properties  related to motion  there is in spin -or indeed what "spin" is when it is at home .


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Offline chiralSPO

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Re: Is spacetime real?
« Reply #20 on: 26/09/2016 18:10:59 »
geordief, your skepticism of Atkhenaken's claims are well-warranted. I would recommend being highly skeptical of those who make such extreme claims (look up some of their other posts, and you might see a pattern develop) Atkhenaken does not believe that viruses exist, or that medicine is anything other than a scam...

To those who are interested in this thread, I would also recommend paying attention to PmbPhy. He is very knowledgeable regarding physics, especially relativity (we have our disagreements too, but on this particular subject, he is an expert!) evan_au is also a knowledgeable and well-intentioned member of this forum.

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Offline jeffreyH

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Re: Is spacetime real?
« Reply #21 on: 26/09/2016 18:31:22 »
Spacetime can be expressed as ds/dt on a 2 dimensional plane. Where a change in position (s) occurs over a time period (t). The value s can be further decomposed into x and y coordinates. Ultimately you can use functions to define a metric (line element) to show how objects move through space time. This then leads onto the principal of least action. However we can never prove if any of this describes an underlying reality since physics is not about that.
Fixation on the Einstein papers is a good definition of OCD.

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Offline geordief

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Re: Is spacetime real?
« Reply #22 on: 26/09/2016 19:00:15 »
geordief, your skepticism of Atkhenaken's claims are well-warranted. I would recommend being highly skeptical of those who make such extreme claims (look up some of their other posts, and you might see a pattern develop) Atkhenaken does not believe that viruses exist, or that medicine is anything other than a scam...

To those who are interested in this thread, I would also recommend paying attention to PmbPhy. He is very knowledgeable regarding physics, especially relativity (we have our disagreements too, but on this particular subject, he is an expert!) evan_au is also a knowledgeable and well-intentioned member of this forum.

Thanks ,yes of course . I look forward to PmbPhy's contributions down the line hopefully.

The phrase "logical certainly " certainly rings alarm bells  as the stand up performer  Tim Vine  might put it

https    ://www.youtube.com/watch?v=HcFd5j1cios

Perhaps I don't have enough posts to post a link on this site yet?
« Last Edit: 26/09/2016 19:03:16 by geordief »

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Offline Bill S

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Re: Is spacetime real?
« Reply #23 on: 26/09/2016 20:16:36 »
Having drifted into talking about particle spin, this might be worth looking at.  Im not always happy with the answers here, but this seems not bad.

http://www.askamathematician.com/2011/10/q-what-is-spin-in-particle-physics-why-is-it-different-from-just-ordinary-rotation/
There never was nothing.

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Offline chiralSPO

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Re: Is spacetime real?
« Reply #24 on: 26/09/2016 22:07:20 »
geordief, your skepticism of Atkhenaken's claims are well-warranted. I would recommend being highly skeptical of those who make such extreme claims (look up some of their other posts, and you might see a pattern develop) Atkhenaken does not believe that viruses exist, or that medicine is anything other than a scam...

To those who are interested in this thread, I would also recommend paying attention to PmbPhy. He is very knowledgeable regarding physics, especially relativity (we have our disagreements too, but on this particular subject, he is an expert!) evan_au is also a knowledgeable and well-intentioned member of this forum.

Thanks ,yes of course . I look forward to PmbPhy's contributions down the line hopefully.

The phrase "logical certainly " certainly rings alarm bells  as the stand up performer  Tim Vine  might put it

https    ://www.youtube.com/watch?v=HcFd5j1cios

Perhaps I don't have enough posts to post a link on this site yet?

Yeah, I don't remember what the required number of posts is before you can link urls directly, but I think you are close. Maybe 20?

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Offline PmbPhy

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Re: Is spacetime real?
« Reply #25 on: 27/09/2016 02:21:36 »
Quote from: mxplxxx
Given we can't seem to go forwards or backwards in Spacetime, how likely is it that Spacetime is real?
I'll try to explain this in another way, i.e. the way that I should have explained it from the very start. First of all it's apparent to me that the problem that you have understanding this is that you don't appear to really know what spacetime is. To resolve that misunderstanding please see how I explained spacetime in the webpage that I created for this purpose.
See: http://www.newenglandphysics.org/physics_world/sr/spacetime.htm

So basically spacetime itself is a mathematical object which was created/defined in order to describe nature. Basically it's a manifold, which is a fancy way of saying that its a set. Its just a set with certain properties. The set is in a one-to-one correspondence  with the world. Each element of the spacetime manifold is defined as an event which, simply put, is a place and time. E.g. A particular point in Boston at 11:31pm. That's an event. So to claim that spacetime isn't real one first has to define the term "real" and then determine of the things that we use to describe nature, such as numbers, are "real." Is the number one "real"? I say yes. Is the complex number i =sqrt(-1) "real"? I say yes here as well.

But seriously. Who cares if it falls under the category of the things we choose to label as "real"?  Not most physicists, that's something I'm sure of. So do yourself a favor and stop worrying about things that don't matter such as how to categorize things. Your time is better spent learning relativity from start to finish. Do that and you'll learn the answers to all of your questions.

Unfortunately there's a very unhelpful trend in this forum which consists of worrying and questioning thjngs like special relativity by people who haven't even read a good textbook on the subject from cover to cover. I find that to be a very sad state of affairs. :(

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Offline mxplxxx

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Re: Is spacetime real?
« Reply #26 on: 27/09/2016 14:42:56 »
It would be interesting to compare the workings of Spacetime to those of an analogue computer and quantum theory to that of a digital computer. There seem to be lots of similarities. This thought also has possible relevance for wave-particle duality. In a funny way, time does not exist in Spacetime seeing as all possible states of the universe exist in Spacetime (not sure of this) and moving from one state to another gives the impression of time. On the other hand time seems to be basic to quantum theory as in particle frequency, radioactive decay etc.. 

Can Spacetime described a galaxy as an abstraction of smaller structure like solar systems?  Pretty sure quantum theory can (e.g. a molecule is an abstraction of elementary particles).

Finally, the possible reason bosons move at the speed of light is that their purpose doesn't need state. They are force carriers.  At the speed of light time, and therefore state, doesn't exist. State implies time and this is likely why fermions exist in time. Fermions handle complex events that happen over time.
« Last Edit: 27/09/2016 23:57:41 by mxplxxx »

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Offline jeffreyH

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Re: Is spacetime real?
« Reply #27 on: 28/09/2016 08:51:28 »
Just to clear up any misunderstanding. Spatial dimensions are a subset of the set of dimensions. An array, or matrix, can have any number of dimensions labelled by indexes. If this is not understood then misconceptions arise.
Fixation on the Einstein papers is a good definition of OCD.

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Offline puppypower

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Re: Is spacetime real?
« Reply #28 on: 28/09/2016 11:50:38 »
One way to address space-time, is to stop time, so time is not longer a variable in our observation. With time stopped we can still observe mass, charge, distance and position. We can also observe motion bur, which gives the impression of motion, with time stopped.

Motion blur is the only affect, of the above, that shows an interconnection between time and distance; time stopped. Motion blur is where two references are the not the same; shutter speed and motion speed.

The Heisenberg Uncertainty Principle could be correlated to motion blur, since an electron; action speed, is in a different reference than the lab; shutter speed, due to relativistic speed of the electron and the non-relativistic lab. Space-time appears in motion blur, blurring the distinction between  momentum (mass, distance and time) and position. This is also what motion blue does.

In the motion blur image below, we can tell the position of the running back in the center, but not his momentum. On the other hand, we can tell there is momentum in the defenders in the foreground, but there is uncertainty in their position. However, we can't determine both position and momentum of everyone.

 

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Offline geordief

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Re: Is spacetime real?
« Reply #29 on: 28/09/2016 12:04:24 »
Just to clear up any misunderstanding. Spatial dimensions are a subset of the set of dimensions. An array, or matrix, can have any number of dimensions labelled by indexes. If this is not understood then misconceptions arise.
I have noted that  the  s^2 =x^2 +y" +z^2 -ct^2 is the only definition of an "interval" in the real world  which is the same when calculated from any  frame of reference.

Can it be  shown(mathematically proven)  that there cannot be others? (I am not talking of polar co-ordinates which  presumably boil down to the  same thing ) 

If one uses more dimensions  as I understand  is done (String Theory?)  does this interval still hold up to this invariant scrutiny?

Is it possible  hypothetically to replace the {+,+,+,-] functions with any other kind of relationship so long as this  interval is maintained (I have nothing in mind ;)   )

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Offline chiralSPO

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Re: Is spacetime real?
« Reply #30 on: 28/09/2016 12:48:03 »
I have cleaned this thread up, and moved the clutter regarding whether or not time is a dimension to a new thread in the subforum "That CAN'T be true" members may feel free to carry on that discussion there, or continue to discuss the original question here.