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A 4th Dimension

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#1 howard929

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Posted 16 July 2014 - 12:00 PM

Reading an article in the current SA about a 4th spacial dimension got me wondering. I can only see or just as valid feel, three. I've read about time and the arrow of time and was left with the impression that it's always in one direction. So what happens if that's not exactly accurate? Might there be a reality where there are 2 times? Don't we in a round about way, experience and notice evidence of that when we ponder that light doesn't age?? The convoluted 11 or so spacial dimensions predicted by String Theory to satisfy problems in quantum theory never seemed to make any sense. How would objects FEEL in such a reality? OTOH, time isn't seen or can it be touched. Three spacial dimensions looks and feels right as a limit. I'm bad with math but could more then 1 time smooth out the same problems with quantum theory as does more then 3 spacial dimensions?

#2 Pess

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Posted 16 July 2014 - 02:27 PM

Reading an article in the current SA about a 4th spacial dimension got me wondering. I can only see or just as valid feel, three. I've read about time and the arrow of time and was left with the impression that it's always in one direction. So what happens if that's not exactly accurate? Might there be a reality where there are 2 times? Don't we in a round about way, experience and notice evidence of that when we ponder that light doesn't age?? The convoluted 11 or so spacial dimensions predicted by String Theory to satisfy problems in quantum theory never seemed to make any sense. How would objects FEEL in such a reality? OTOH, time isn't seen or can it be touched. Three spacial dimensions looks and feels right as a limit. I'm bad with math but could more then 1 time smooth out the same problems with quantum theory as does more then 3 spacial dimensions?



I've always felt that the dimension of 'Time' can be thought of in terms of 'enduring'.


You have a measurement of length. You have one of width and one of height. You also have one of duration.

"The shoebox is 14 inches long. It is 6 Inches wide and 8 inches in height and has existed for a duration of 2 years."

So it takes reporting on all 4 dimensions in order to correctly define the shoebox in the Universe. For example, if the shoebox only existed from 2012-2014' and a time traveler went looking for it in 2011' he won't find it.

All objects, in order to be said to exist, must extend into all 4 dimensions.

Pesse (Unless they extend into the Fifth Dimension in which case they sing music) Mist

#3 Qwickdraw

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Posted 16 July 2014 - 03:27 PM

You bring up some interesting thoughts.
Retrocausality although not necessarily related to another dimension may also be an engaging topic related to your post.

And then there is the notion that physical processes may work perfectly well regardless of which direction the arrow of time is facing in the quantum world but on the macroscopic level, not so much.

#4 Andy Taylor

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Posted 16 July 2014 - 04:05 PM

Google "imaginary time" and "CPT symmetry"...

Then have a stiff drink. :grin:

#5 howard929

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Posted 16 July 2014 - 04:54 PM

I've read but don't have the ability to grasp any of the math involved where Kazula/Kline postulated that extra physical dimensions would solve certain quantum issues. I've always had a problem wrapping my head around those extra physical dimensions. Then there's the brane and the bulk as well as string theory with all of their dimensions just seems too much like sci-fi then science to me. If time has multiple descriptions OTOH, and I don't know if it actually does, then could that do anything to help tame quantum theory? It seems easier for me to grasp extra dimensions if they're time. Odd isn't it that quantum teleportation is instantaneous? That's a physical result involving messengers particles that do what? Heck I don't know. Is it travel through an unseen dimension or is time a tricky guy for certain particles? I'm thinking time might be a very tricky guy because I can grasp that.

#6 howard929

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Posted 16 July 2014 - 05:01 PM

Google "imaginary time" and "CPT symmetry"...

Then have a stiff drink. :grin:


OK. My teeth hurt but it's too early for a stiff one.

#7 GJJim

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Posted 16 July 2014 - 06:18 PM


"The shoebox is 14 inches long. It is 6 Inches wide and 8 inches in height and has existed for a duration of 2 years."

So it takes reporting on all 4 dimensions in order to correctly define the shoebox in the Universe. For example, if the shoebox only existed from 2012-2014' and a time traveler went looking for it in 2011' he won't find it.

All objects, in order to be said to exist, must extend into all 4 dimensions.

Pesse (Unless they extend into the Fifth Dimension in which case they sing music) Mist


That's the narcissistic, Earth-centric way of looking at the shoebox. What if its existence/endurance depends on literally everything else in the universe? Its presence in our reality might be explained by a different and unified way of looking at space and time. Taking a page from the Hitchhiker's Guide novel, Twistor theory alludes that your shoebox existed because that was the least improbable configuration for the Reimann sphere known as your closet. :grin:

#8 darknesss

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Posted 17 July 2014 - 02:52 AM

Having a 4th dimension (time) makes sense to me only if an "arrow of time" can go faster or slower, like a vector that can change magnitude, but not its direction. Otherwise if the vector is always constant then the 4th dimension is redundant.

If the vector can change direction (time travel, etc) then the universe might have to store position*time for every minimum unit of time (unless there is no minimum and Planck time is meaningless) and then reproduce physical processes all over again, faster than they happen.

There might not even be 3 dimensions, instead of width [1] x length [2] x height [3] it could be:
distance [1] from one point (the point is always the same so it doesn't count, it could even be the location of the big bang haha) and two angles [2] compressed into one ... if the universe supports infinite numbers :D
There could even be only 1 dimension w=x*y*z, where the space is a continuous line of Planck length units or something. Instead of moving from point A (1,1,1) to B (10,10,10) you move from 1 to 1000 without factoring 1000 into 10,10,10.

#9 PeterR280

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Posted 17 July 2014 - 09:55 AM

There is the concept of orthogonality when describing dimensions. Things happening along one dimension have no impact on other dimensions if the axes are orthogonal. For example, if you are moving or accelerating along the x-axis only, there is no motion in the y or z axes.

Einstein was the first to describe spacetime as a true 4-dimensional structure. It is in the form of Minkowski space, which is Euclidian, for Special Relativity and Riemannian monifolds for General Relativity, which are non-Euclidian. A 4 vector in Minkowski space has time as dimension. Transformations are made that are essentially rotations in the 4 dimensional space. Time and space get longer and shorter based on the rotations. It is exactly like the x-axis getting shorter while the y-axis gets longer as you rotate constant length around the origin in flat plane. It gets much more complicated fir General Relativity where tensors replace 4-dimensional vectors. A length in Minkowski space is described as s^2=-c^2*t^2+x^2+y^2+z^2, where s^2 in the square of the length. If you notice, time squared takes on a negative value to make the math work. If you took the square root, it would take on an imaginary value.

#10 EJN

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Posted 17 July 2014 - 11:09 AM

A length in Minkowski space is described as s^2=-c^2*t^2+x^2+y^2+z^2, where s^2 in the square of the length. If you notice, time squared takes on a negative value to make the math work. If you took the square root, it would take on an imaginary value.


sqrt(-c^2*t^2) = ict

This sign usage is denoted -+++ and is called the "spacelike" convention.

Many modern physicists use +--- which is known as the "timelike" convention,
so the equation takes the form s^2 = (ct)^2 - x^2 - y^2 - z^2

In the book Gravitation by Thorne, Misner, & Wheeler, they have a table
of sign conventions used by various physicists over the years, and a section
called "A Farewell to ict."

#11 Qwickdraw

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Posted 17 July 2014 - 11:43 AM

For example, if you are moving or accelerating along the x-axis only, there is no motion in the y or z axes.


Maybe but one objects X axis may be another observers Y or Z axis depending on their perspective. So who is really to say?

#12 PeterR280

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Posted 17 July 2014 - 12:11 PM

in the timelike convention, spacial dimensions take on imaginary values.

#13 darknesss

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Posted 17 July 2014 - 01:24 PM

There is the concept of orthogonality when describing dimensions. Things happening along one dimension have no impact on other dimensions if the axes are orthogonal. For example, if you are moving or accelerating along the x-axis only, there is no motion in the y or z axes.

Einstein was the first to describe spacetime as a true 4-dimensional structure. It is in the form of Minkowski space, which is Euclidian, for Special Relativity and Riemannian monifolds for General Relativity, which are non-Euclidian. A 4 vector in Minkowski space has time as dimension. Transformations are made that are essentially rotations in the 4 dimensional space. Time and space get longer and shorter based on the rotations. It is exactly like the x-axis getting shorter while the y-axis gets longer as you rotate constant length around the origin in flat plane. It gets much more complicated fir General Relativity where tensors replace 4-dimensional vectors. A length in Minkowski space is described as s^2=-c^2*t^2+x^2+y^2+z^2, where s^2 in the square of the length. If you notice, time squared takes on a negative value to make the math work. If you took the square root, it would take on an imaginary value.

If you have to go to great lengths to "make the math work", perhaps that means the equation is invalid?

#14 Pess

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Posted 21 July 2014 - 12:48 PM

Having a 4th dimension (time) makes sense to me only if an "arrow of time" can go faster or slower, like a vector that can change magnitude, but not its direction. Otherwise if the vector is always constant then the 4th dimension is redundant.

If the vector can change direction (time travel, etc) then the universe might have to store position*time for every minimum unit of time (unless there is no minimum and Planck time is meaningless) and then reproduce physical processes all over again, faster than they happen.

There might not even be 3 dimensions, instead of width [1] x length [2] x height [3] it could be:
distance [1] from one point (the point is always the same so it doesn't count, it could even be the location of the big bang haha) and two angles [2] compressed into one ... if the universe supports infinite numbers :D
There could even be only 1 dimension w=x*y*z, where the space is a continuous line of Planck length units or something. Instead of moving from point A (1,1,1) to B (10,10,10) you move from 1 to 1000 without factoring 1000 into 10,10,10.


How do you know the Universe doesn't experience time as individual quantized 'instants' strung together?

Sort of like how we make cartoons today: Draw a bunch of 'instants' and then flip through the stack and, viola', we have a video pulled from distinct quanta of 'instants'.

Pesse (..and, according to quantum physics, each 'instant' can break off into all possible follow-up quanta) Mist

#15 darknesss

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Posted 21 July 2014 - 01:38 PM

How do you know the Universe doesn't experience time as individual quantized 'instants' strung together?

Sort of like how we make cartoons today: Draw a bunch of 'instants' and then flip through the stack and, viola', we have a video pulled from distinct quanta of 'instants'.

Pesse (..and, according to quantum physics, each 'instant' can break off into all possible follow-up quanta) Mist

I really don't know. But then wouldn't we live in a pre-determined (with 1 stack) or redundant (choosing a frame from many stacks which also require more storage) universe? I call the 2nd possibility redundant because events could just happen in-place, on the fly, without needing time.

#16 GregLee1

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Posted 21 July 2014 - 01:50 PM

I'm bad with math but could more then 1 time smooth out the same problems with quantum theory as does more then 3 spacial dimensions?

That's an interesting idea, but I guess there'd have to be as many extra time dimensions as there are extra velocities (or maybe I should say "speeds").

#17 Elric82

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Posted 21 July 2014 - 04:15 PM

All this talk about time reminds me of a thought I had a long time ago. Time (as we know it) is only relative to us here on earth. Dictated by the sun and rotation of the earth, correct? We may say the speed of light is 186,286 mps, but that's just our perspective on it. I would venture to say that the speed of light isn't even constant. Are not all these theories based off of values that we have determined based on our own perspectives?

#18 frolinmod

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Posted 21 July 2014 - 09:34 PM

I thought the speed of light in a vacuum is a constant with the value 1.

#19 Jarad

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Posted 22 July 2014 - 07:56 AM

Time (as we know it) is only relative to us here on earth. Dictated by the sun and rotation of the earth, correct? We may say the speed of light is 186,286 mps, but that's just our perspective on it.



Actually, one of the central facets of relativity is that the speed of light © is constant. It is always measured as exactly 186,282.4 mps, or 299,792,458 meters per second, no matter what reference frame you measure it from. Different reference frames will measure time differently, and they will measure distance differently, but time and distance vary in a manner that maintains C as a constant.

Jarad

#20 Elric82

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Posted 22 July 2014 - 09:27 AM

I was half expecting a reply like this. So c is constant even near a black hole? Won't a black hole "warp" light and time in general? If so, than there must be something I'm missing here. Thanks for the reply I was expecting though :foreheadslap:

#21 GregLee1

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Posted 22 July 2014 - 10:27 AM

Time (as we know it) is only relative to us here on earth. Dictated by the sun and rotation of the earth, correct? We may say the speed of light is 186,286 mps, but that's just our perspective on it.



Actually, one of the central facets of relativity is that the speed of light © is constant. It is always measured as exactly 186,282.4 mps, or 299,792,458 meters per second, no matter what reference frame you measure it from.

As I interpreted the question, it's about why we should use earthly parochial measures like miles, meters, seconds. If one uses different units of measure, different figures for c result.

#22 llanitedave

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Posted 22 July 2014 - 11:10 AM

They're different numbers, but they all mean the same velocity. If you want to use a universal cosmic reference frame, then c = 1.

#23 ColoHank

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Posted 22 July 2014 - 01:50 PM

The speed of light may be a constant, and blindingly fast from the perspective of folks like us who frame distances in terms of miles or kilometers and time in terms of a day and its subdivisons. I'd imagine, however, that the perception of light-speed might differ considerably depending on the frames of reference (size, distance, elapsed time, etc.) peculiar to observers from other worlds, should there indeed be other populated worlds. A thinking ant, for example, might perceive our world to be ever so much larger than we do, because, unlike ants, we have developed technologies to shrink it. And a creature accustomed to a much different diurnal cycle and the ability to travel faster than we can possibly imagine might perceive our goings-on as proceeding at a strange pace -- just as we marvel at the busy and seemingly restrictive lives of ants.

Everything, as they say, is relative.

#24 Elric82

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Posted 22 July 2014 - 01:59 PM

If c= 1, then what value or basis is c relative to?
I only ask because I'm curious. This (in my mind) doesn't explain how c changes near a black hole (singularity?). If c is supposed to be constant, "unchangeable" , and a lot of theory revolves around this, then why are these theories made from uncertainties? But taken as gospel? I must be confused. I understand that c is supposed to be a fixed value, but clearly it isn't. It can't be. C maybe a fixed value, but from who's view point? It's not the same, (near a black hole, for instance) as it is relative to you're position in space.

#25 Elric82

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Posted 22 July 2014 - 02:17 PM

I like the way you think. But what if we're the ants(as I'm sure we prolly are). I hope this doesn't turn the direction I think it will, cause this is an awesome thread. I'm still wading through quantum mechanics myself; but some times I feel like either I'm in over my head, or maybe I've thought of things that I can't come to turns with via my current understanding. I guess that's why we have such a great place like CN :jump:






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