Does a dimension have dimensions?

Main Question or Discussion Point

new to physics and my first question

first,i am a nearly newbie high school student in physics, please i would like to learn physics from the internet enough to let me think ?........also i have a question in dimensions and please anyone explain how can you measure the 4d of matter although (i think) that every dimension is variable i mean where is the origin if it is also has 4d so every dimension has 4d so please anyone explains that to me.
 

Answers and Replies

536
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first,i am a nearly newbie high school student in physics, please i would like to learn physics from the internet enough to let me think ?........also i have a question in dimensions and please anyone explain how can you measure the 4d of matter although (i think) that every dimension is variable i mean where is the origin if it is also has 4d so every dimension has 4d so please anyone explains that to me.
Erm... could you please rephrase that question of yours? No offense but it's hardly comprehensible.
 
Mentz114
Gold Member
5,424
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Ahmed,
you're getting ahead of yourself. Your question does not make sense. I suspect you've picked up somewhere that we model space-time as a 4-D space and you have not understood what it means.

In special relativity, an 'event' is defined as a 4-vector (t, x, y, z ). The choice of origin has no bearing on actual physical quantities.
 
OK i am not violating but i just think that the dimensions of the universe are so complicated , i think that every dimension i.e x dimension has its dimensions to be determined , i have less knowledge but i just can't understand that .you see in 3ds max the 3d are defined as the three dimensions are constant reference but what if in our problem time has dimensions???????? I hope i can get you to the picture although i can't really define my idea......all in all i mean does the dimension depend on other dimensions????
 
i just think that the dimensions of the universe are so complicated , i think that every dimension i.e x dimension has its dimensions to be determined , i have less knowledge but i just can't understand that .you see in 3ds max the 3d are defined as the three dimensions are constant reference but what if in our problem time has dimensions???????? I hope i can get you to the picture although i can't really define my idea......all in all i mean does the dimension depend on other dimensions????
 
cristo
Staff Emeritus
Science Advisor
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It seems you're using two different definitions of the word "dimension" in the same sentence. What do you mean by the word dimension?
 
please don't violate me i am still a newbie i just want to learn.... as an example you are running from a starting point and i said you took 10 sec for running 100 m how you could believe that although the starting point itself is not a constant reference then how do you know that time itself has no dimensions or it can depend on another dimension or how can you know that time is 1,2,3,..... only can't it be that the defining of time depends on something else (the same for x,y,z) ? I can't really clarify my idea but i just need help.
 
JesseM
Science Advisor
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please don't violate me i am still a newbie i just want to learn.... as an example you are running from a starting point and i said you took 10 sec for running 100 m how you could believe that although the starting point itself is not a constant reference then how do you know that time itself has no dimensions or it can depend on another dimension or how can you know that time is 1,2,3,..... only can't it be that the defining of time depends on something else (the same for x,y,z) ? I can't really clarify my idea but i just need help.
You can define the runner's position using rulers which measure distance from the origin along your three axes (which you could call forwards-backwards, left-right, and up-down). You could define the time that he passes various landmarks (say, the starting line and the finish line) by placing synchronized clocks at those landmarks, and noting the time on the clocks as he passed them. Why would you need additional dimensions to do these things? And if you think there are additional spatial or time dimensions, what physical method would you suggest to measure an object's coordinates in these dimensions?
 
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first,i am a nearly newbie high school student in physics, please i would like to learn physics from the internet enough to let me think ?........also i have a question in dimensions and please anyone explain how can you measure the 4d of matter although (i think) that every dimension is variable i mean where is the origin if it is also has 4d so every dimension has 4d so please anyone explains that to me.
My guess is that you are getting two different but related ideas mixed up. The term "dimension" characterizes the space. It is the number of orthogonal basis vectors required to span the space. So, for example, in order to span the 2D space of a sheet of paper you need a vector going left-right and a vector going up-down. If you add a third vector on the paper it will not be orthogonal to the other vectors, and if you remove one vector you will only be able to span one line on the paper and not the whole paper.

A related, but different, concept is the idea of a coordinate system (also called a reference frame). A coordinate system is a method of uniquely labeling the points in a space. Each point is identified by some linear combination of the basis vectors.

What I believe you are asking about is the fact that the basis vectors are not intrinsic to the space, but are essentially specified arbitrarily. So, going back to the 2D space above, we could have our vectors go left-right and up-down from the bottom left hand corner of the paper, or we could have our vectors at 45º and -45º from the middle of the paper. In both cases you have two orthogonal basis vectors since the space is 2D, but in each case every point will have a different label than in the other system. It is completely arbitrary which basis vectors you choose, as long as they are orthogonal and span the space.
 
ok i nearly understood and thanks in advance to you all .Do you think that time may have dimensions? here is the question if so it has dimensions which i don't know so the universe will be so complicated and you will get yourself to find the dimensions of the time dimensions i.e say that the magnetic field changes in the universe is one of the factors affecting time so that it's format is not stable except in some conditions (format here is not hours or seconds but the whole time i don't know exactly how ) so time will not be a refrence dimension unless you formulate it with magnetic field and make the magnetic field a dimension of time......I think that the mirrors are 2d but the images in it appear to be 3d and your position relative to the mirror will change the 3rd dimension ,you will not observe that unless you change your position reatiive to the 3rd dimension to the mirror...I hope you can get my idea i don't tell it is right but i think that
there is no idea that doesn't contain any pros that you can benefit from although i have small amount of knowledge and i need to learn for years to tell a word......
 
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yuo don't even need an orthogonal basis... it enough the linear indipendence

ciao
 
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Are there dimensions within dimensions? These are my thoughts.

The answer to this depends on how you define a dimension. Depending on your point of view and the terminology you use, you could say that there are dimensions within dimensions. Different models in physics do not necessarily use the same dimensional model. Strictly speaking, you could define an infinite number of physical dimensions.

In physics, scientists are constantly defining new ways of looking at the universe -- new dimensions to look at the universe through.

You could say that the dimension of the physical Earth is a dimension within the entire physical dimension. Why not.

Do you think that time may have dimensions? here is the question if so it has dimensions which i don't know so the universe will be so complicated and you will get yourself to find the dimensions of the time dimensions i.e say that the magnetic field changes in the universe is one of the factors affecting time
I believe that you are asking if there are dimensions higher than the dimension of time whose objects may effect the behaviour of time-objects which are in the dimension of time? There are theories out there that do say such higher dimensions exist.

so time will not be a refrence dimension unless you formulate it with magnetic field and make the magnetic field a dimension of time.
Even if there really are higher dimensions that effect the behaviour of time-objects, physicists have been able to accurately predict the behaviour of certain aspects of the universe using time as a reference dimension, even though they do not necessarily understand the higher dimensions which may be influencing the dimension of time.

Some related links:

http://www.1729.com/peerreviews/examples/TimeMayHave13Dimensions.html [Broken]
http://www.damtp.cam.ac.uk/user/gr/public/qg_ss.html
http://www.sciencedaily.com/releases/2007/02/070203103355.htm

Scott
 
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thanks very much scott you got my idea....
 
xristy
Gold Member
116
2
Determining dimension

... explain how can you measure the 4d of matter
You might find the discussion on how to determine dimension on page 9 of http://www.arxiv.org/abs/gr-qc/9610066" [Broken] informative.

X.
 
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