# The Naked Scientists Forum

### Author Topic: How many Dimensions are there? (..and is Time one too?)  (Read 2537 times)

#### senga14

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##### How many Dimensions are there? (..and is Time one too?)
« on: 06/04/2013 21:49:45 »
Hello,

I watched several documentations about the Stringtheorie, Albert Einsteins and Newtons views of the universe, dark matter etc. but some things I still dont get. But my main question is: Is it proved that time is a dimension ? And are there more dimensions or are they even infinite ? And also: Are there differences between spatial dimensions (because I saw some kind of 4-D Cubes[Of course they are not really 4D but atleast we can imagine them like 2D people could imagine 3D stuff]) and dimensions like time ?

Hopefully you can answer my questions !

Please phrase all Topics as a question - moderator
« Last Edit: 07/04/2013 08:20:15 by evan_au »

#### Ethos_

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##### Re: Dimensions
« Reply #1 on: 06/04/2013 22:19:07 »
Hello,

Is it proved that time is a dimension ?
All but the most radical scientific views consider time to be one of the dimensions.

Quote from: senga14
And are there more dimensions or are they even infinite ?
String theory proposes more than the 4 we're talking about here. And the only difference between the three spatial dimensions and time is the method by which they are measured.

#### senga14

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##### Re: Dimensions
« Reply #2 on: 06/04/2013 22:32:04 »
I know its considered as a dimension and I know that time is in realtion with space but can it be proven that it is its own dimension ?
« Last Edit: 06/04/2013 22:35:43 by senga14 »

#### Ethos_

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##### Re: Dimensions
« Reply #3 on: 06/04/2013 22:40:41 »
I know its considered as a dimension and I know that time is in realtion with space but can it be proven that it is its own dimension ?
Ask yourself this question: How do we prove that height, width, and length are dimensions? We measure them. Same with time, we measure it.

#### senga14

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##### Re: Dimensions
« Reply #4 on: 06/04/2013 22:44:49 »
Thats an intresting point of view. But it would mean that everything that can be measured would be its own dimension, would'nt it ? That would mean that temperature is an dimension too right ?

#### Ethos_

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##### Re: Dimensions
« Reply #5 on: 06/04/2013 22:53:42 »
Thats an intresting point of view. But it would mean that everything that can be measured would be its own dimension, would'nt it ? That would mean that temperature is an dimension too right ?
You're confusing dimensions here my friend. All measures consist of dimensions, but the area of space we live in consist of only 4 unless you subscribe to string theory. But even in String Theory, the dimensions that are considered are related to the space we live in.

#### senga14

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##### Re: Dimensions
« Reply #6 on: 06/04/2013 23:00:38 »
Though I get your point and after all the research I've done we are still at the point where we dont really know if time is a dimension, right ?. Stephen Hawking says yes but doesnt mean its true though hes extremly intelligent. So there is still no 100% proof for it.

#### senga14

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##### Re: Dimensions
« Reply #7 on: 06/04/2013 23:02:53 »
I only see "its determinated", "it is estimated"

#### Ethos_

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##### Re: Dimensions
« Reply #8 on: 06/04/2013 23:11:16 »
Though I get your point and after all the research I've done we are still at the point where we dont really know if time is a dimension, right ?. Stephen Hawking says yes but doesnt mean its true though hes extremly intelligent. So there is still no 100% proof for it.
If you have a new theory, you'll need to post it in the New Theories section of the forum. This section is devoted to what is considered The Standard Model.

#### senga14

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##### Re: Dimensions
« Reply #9 on: 06/04/2013 23:16:08 »
I dont have a new theorie  ;D

I just trying to understand what a dimension is and how a dimension is defined. And if there would be prouf why time is a dimension it would maybe help me.

But thank you for the constructive comments, they helped me a lot !

#### yor_on

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##### Re: Dimensions
« Reply #10 on: 06/04/2013 23:40:14 »
Senga, forget dimensions and think of it as degrees of freedom instead. A degree of freedom can be described with a arrow on a paper. If you draw a cube on it you get three arrows, length width and height. The fourth arrow is, well, it's what we call 'the arrow of time'. That arrow has one direction only, at least as far as I know. From ones birth to ones death, but it definitely exist, even though you can't hold it in your hand.

#### evan_au

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##### Re: How many Dimensions are there? (..and is Time one too?)
« Reply #11 on: 07/04/2013 08:50:01 »
One of the important aspects that allows something to fully qualify as a new "Dimension" is whether it is independent of the other things that you would like to call a Dimension.

You can measure the position of something in X (left/right), Y (up/down) and Z (front/back) coordinates.

You could imagine inventing a "W" dimension, which is measured at 45 degrees in the horizontal plane, and this might be a really useful thing to do if you were cutting mitred joints in wood for a window frame. However, you cannot really call it a complete new dimension, because you can calculate W just by knowing X, Y & Z; if you move in the X direction, you will also move in the "W" direction, so they are not truly independent. You have not discovered a new dimension.

To some extent, dimensions are arbitrary - you can also measure the position of something in "Polar" coordinates, eg Latitude, Longitude & Altitude, and for some applications like navigation, this is the convention. But you will notice that these are all independent, and there are still 3 of them. So we say that our familiar environment can be described as 3 dimensions of space.

Another arbitrary aspect of dimensions is where you start measuring from. But it is possible to convert from one set of 3 dimensions to another set of 3 dimensions using formulas.

Now, you cannot describe the position of a motor car as just these 3 dimensions, because its position keeps changing. To properly describe a motor car, you must describe it in X, Y, Z and T (time). You cannot calculate T by just knowing X, Y & Z. If you park it in one place, the X,Y & Z dimensions don't change, but it appears at different points in time, ie they are independent dimensions. (Einstein showed that you cannot change the X, Y and Z dimensions without changing time, as no physical object can exceed the speed of light, so they are not entirely independent, but they are different enough to make it worthwhile.)

String theory suggests that there may be additional dimensions of space (eg a total of 10 or 11) that were only accessible in the very high energies present in the Big Bang, and that most of them have subsequently shrunk until they are unnoticeable to us today, leaving just the familiar 3 dimensions of space. Some experiments in the Large Hadron Collider are hoping to recreate these energy levels, and are searching for signs of extra dimensions, but no clear indications yet.

You can have dimensions which are different from dimensions of time and space:
• If you are studying the operation of an internal combustion engine, you may want to graph the operation in terms of the temperature and volume of the gas as dimensions.
• I once saw a facial recognition system which measured 22 aspects of a person's face, and looked for nearest neighbours in this "22 dimensional space". Although the units were length, this was measuring the shape of an irregular object, not its position in space. Some of these dimensions would not have been truly independent, because the distance between your eyes is not entirely independent of the distance between your ears, for example (although Picasso certainly tried making them independent) ...
« Last Edit: 07/04/2013 20:41:45 by evan_au »

#### Pmb

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##### Re: How many Dimensions are there? (..and is Time one too?)
« Reply #12 on: 07/04/2013 09:17:21 »
Hello,

I watched several documentations about the Stringtheorie, Albert Einsteins and Newtons views of the universe, dark matter etc. but some things I still dont get. But my main question is: Is it proved that time is a dimension ? And are there more dimensions or are they even infinite ? And also: Are there differences between spatial dimensions (because I saw some kind of 4-D Cubes[Of course they are not really 4D but atleast we can imagine them like 2D people could imagine 3D stuff]) and dimensions like time ?

Hopefully you can answer my questions !

Please phrase all Topics as a question - moderator
There are three dimensions in space and there is one dimension in time making spacetime four dimensional. That means it takes four numbers to locate a unique event (defined as a place nd time) in spacetime.

#### yor_on

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##### Re: How many Dimensions are there? (..and is Time one too?)
« Reply #13 on: 07/04/2013 13:27:25 »
You are right Evan, we do have three room dimensions. But they are not separated, which is why we find 'SpaceTime' able to shrink and adapt, as I think. And they lock us up in a way of looking at things as we go out from splitting them into new 'dimensions'.

#### Bill S

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##### Re: How many Dimensions are there? (..and is Time one too?)
« Reply #14 on: 07/04/2013 20:44:17 »
Some time ago I was asked about dimensions by a friend's son.  The following is an extract from the very non-scientific response I gave him.  Perhaps it might be a help.

Perhaps the simplest way to think about the dimensions of any given space is to think in terms of the number of co-ordinates that would have to be given in order to specify one particular point.  First let us consider a straight line drawn on a sheet of paper; if this line is 10cm long, with 0 at the left and 10 at the right, then the single co-ordinate 0.9cm will designate a unique point just short of the 1cm mark.  Nothing further is needed, so we can say that the line has one dimension.  In the case of a surface area the situation is only a little more complex.  We already have a straight line, marked off in 1cm intervals from the left.  Raise a vertical (i.e. towards the top of the paper) line from the 0 point of the first line and mark it in 1cm intervals from the bottom.  If it helps you to do so, complete the square and fill in the grid of 1cm squares.  Call the left side of this square A and the bottom edge B.  Clearly, a unique point on this surface can be designated by using two co-ordinates, as for example, A7 - B4, or to be more specific about the location, A7.5 - B3.2.  Two co-ordinates are needed to specify a unique point on our surface, so it is deemed to have two dimensions.  Let us now imagine we have a very large number of small blocks, each measuring 1cm by 1cm by 1cm.  One hundred of these little cubes can be placed on the surface of our square.  If we place another nine layers, each of 100 cubes, on top of the first, we will have a larger cube made up of 1,000 small cubes.  In order to specify any one particular small cube within the larger one we will have to use the two co-ordinates from our earlier surface, and also raise a vertical (this time perpendicular to the surface of the paper) line on which to mark a third set of co-ordinates, similar to the other two.   If we call this new line C, any small cube can be identified by giving three co-ordinates, as for example, A9 - B3 - C5.  If we wanted to pinpoint the small cube in the bottom, left hand, front corner, its co-ordinates would be A0 - B0 - C0.  Notice that in the case of the verbal description and the co-ordinates, the designation of the position requires three elements.  The cubes are therefore said to have three dimensions.

Whilst the definition of dimensions set out above is perfectly valid in terms of theoretical calculations, there are serious problems when trying to apply these definitions on a practical basis.  Let us start with the concept of a two dimensional surface.  No one would deny that a surface has only two dimensions.  Any point on the surface can be designated by two co-ordinates, as we have seen.  However, it also has to be accepted that in order to be a surface, in the real world, it must be the surface of something.  Remove the something and you remove the surface.  Furthermore, any activity undertaken on that surface requires a third dimension.  Any mark made on that surface, for example, must either rest on the surface, in which case it is in a third dimension, or it must soak into the fabric underlying the surface, which also requires a third dimension.  The something of which the surface is the surface.

Draw a straight line on a sheet of paper.  We considered a straight line as having only one dimension, but in fact it has width as well as length.  Imagine reducing the width of that line; how far do you have to reduce it in order to claim that it has no dimension of width?  The reality is that the dimension of width does not vanish until the whole of the line has gone.  Logic tells us that the same applies to the third dimension; the only way to remove the depth of the line is to remove the entire line.

This is probably where the concept of infinity will creep into the discussion.  Valuable as reduction to infinity might be to the theoretician, it could have serious consequences in the real world.

Then there was Einstein!!!  Einstein had this disconcerting habit of pointing out that nothing was as simple as Newton would have had us believe.  Three dimensions were no longer enough, suddenly we needed a forth.  We established earlier that three co-ordinates were needed in order to specify a particular point in three dimensions.  Let us now apply that to a particular example.  At the junction of High Street and Church Street there is a multi-story car park.  You arrange to meet a friend on the third floor of that car park.  The three dimensional reference gives all you need for the meeting to take place, or does it?  Suppose your friend arrived at 10am and you did not turn up until 5pm.  Either you would have the most patient friend in the world, or the meeting would not take place.  A forth co-ordinate is needed for the success of the arrangement.  Before Einstein, no-one would have suggested that there was any significant connection between time and space, other than that time was the measure by which we could keep track of the changes that took place in space.   Einstein, however, maintained that not only were matter and energy interchangeable (E =mc² took its bow on the scientific stage), but so were time and space.  Time had to be considered as a dimension, and this 4D "thing" became spacetime.

BTW, Senga14, if you are looking for 100% proof of anything, science is probably not the place to look. :)

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##### Re: How many Dimensions are there? (..and is Time one too?)
« Reply #14 on: 07/04/2013 20:44:17 »