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 Philosophy of Physics Philosophy of Physics Forum - Philosophical questions about our universe

 May 13th 2017, 05:46 PM #11 Senior Member   Join Date: Aug 2010 Posts: 418 You can call "energy", or anything else, whatever you like as long as you don't care about anyone else understanding you.
 May 14th 2017, 01:40 PM #12 Banned   Join Date: Nov 2016 Posts: 63 I attempted to explain it, in several different ways, throughout this thread. Which one didn't you like? How about Energy is matter that is in a superposition state.
 Jul 9th 2017, 05:20 PM #13 Senior Member   Join Date: Aug 2010 Posts: 418 What we didn't like has already been explained to you. Please either take a basic physics course, or read a good basic text book on physics, not just "popular" books or web sites. You are using words, whose definitions you don't understand, in ways that do not make sense. As for your last post, "energy" is NOT "matter". That is NOT what "e= mc^2" means! topsquark likes this.
Jul 16th 2017, 09:02 PM   #14
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 Originally Posted by pittsburghjoe Energy is a dimension just as much as Time.
The term dimension is a mathematical one. Its a property of certain kinds of mathematical objects. Its defined as the minimum number required to uniquely determine an element of the object.

The precise definition is given here: Dimension -- from Wolfram MathWorld

The most common example is three dimensional space (3-space). It takes 3 numbers to locate a point in 3-space. Another example is a 4-vector which takes 4 numbers to define it. Spacetime is an another example of a mathematical object which requires 4 numbers to define a point in spacetime. Such a point is called an event.

The 4-vector known as 4-momentum. P is properly defined as

P = (mc, p)

where

m = relativistic mass
p = 3-momentum.

m is the time component of 4-momentum.

What is the object of which you assert that E is a component of?

I can't address the rest of your post until you are able to clearly state or defined the object is that you claim that energy is a component of.

Jul 16th 2017, 09:16 PM   #15
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 Originally Posted by Woody Hi PittsburghJoe, I'm not sure that I understand your post, however you might like to consider the vector. Note how mass appears in the space-wise components and Energy in the time-wise component.
In general the energy of an object is the time component of the 4-form associated with the 4-momentum of the object, not the time component of the 4-momentum. I.e. in general

E = P_0, not P^0

There's a sign that I'm leaving out since it depends on the signature of the metric.

You can read the proof of this statement at
Conserved Quantities

You can also read an argument for this definition in Max Jammer's book

Concepts of Mass in Contemporary Physics and Philosphy

The derivation is on pages 48-50.

Jul 16th 2017, 09:33 PM   #16
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 Originally Posted by Woody In physics the term "dimension" is generally reserved for the four components of the vectors defining relative positions in spacetime.
I'm a bit confused as to what you mean by "generally." Can you explain, please?

The reason I ask is because depending on which dictionary one uses the term generally is defined in two ways. Its why I hate it when I use the term. Lol!!

E.g. do a search on "generally definition" using Google and these definitions will pop up
 1. in most cases; usually. 2. in general terms; without regard to particulars or exceptions.
Confusing, isn't it?

So do you mean that in all cases In physics the term "dimension" is reserved for the four components of the vectors defining relative positions in spacetime. or in most cases?

If its all cases then I disagree. E.g. spinors are used in quantum mechanics and spinor, the components of which are not components of spacetime. In fact the spinor which represents spin only has two components, i.e. a spinor is a two-element column vector.

My point being that there are other objects in physics which have dimensions, not just in string theory (which I'm ignorant of).

Jul 16th 2017, 09:36 PM   #17
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 Originally Posted by HallsofIvy What we didn't like has already been explained to you. Please either take a basic physics course, or read a good basic text book on physics, not just "popular" books or web sites. You are using words, whose definitions you don't understand, in ways that do not make sense. As for your last post, "energy" is NOT "matter". That is NOT what "e= mc^2" means!
Many members don't know math and wouldn't be able to follow along in a course at the level I think you have in mind. He'd be better off learning math first, after which he wouldn't need to learn the physics you're referring to because he'd learn that he's using the term "dimension" incorrectly.

 Jul 17th 2017, 05:02 AM #18 Senior Member     Join Date: Jun 2016 Location: England Posts: 932 In reply to PMB Yes, by generally I mean in most cases, or usually, (in general terms; without regard to particulars or exceptions). in particular I was trying to separate the term dimension as applied to vectors from the term as it might sometimes be applied to scalar quantities. __________________ ~\o/~
 Jul 17th 2017, 06:01 AM #19 Physics Team   Join Date: Apr 2009 Location: Boston's North Shore Posts: 1,576 I see. Thanks for clearing that up. pittsburghjoe - Please take notice of the fact that while spacetime and a 4-vector are both 4-dimensional objects. Spacetime is what is known as a manifold, which is a fancy name for a set of points with certain properties. I'd also like to note that nothing that you said is correct. There is another use of the term "dimension" in physics ii as it pertains to physical dimensions, i.e. to refer to the units in which something is measured. For example: the IS dimensions of area is the square meters, force is the Newton, charge the Coulomb. See: https://en.wikipedia.org/wiki/Dimensional_analysis In any branch of science there are well-defined terms, mass, energy and time being some of them. It serves no useful purpose to anybody to define them differently. Only confusion can result from that. It can be useful to discuss whether a term should be defined in a given way. Those conversations even appear in the American Journal of Physics. But that's different than what you're doing here. And I can promise you that nothing you posted here would be good in any physics textbook so no, it's not time to rewrite any textbook. I don't wish to be rude, that's not my intent. I'm merely trying to help you understand what you're doing wrong. This is a physics help forum. Its not a New Theories forum. The purpose of this forum is to help people learn and understand mainstream physics. To the rest - It just occurred to me that there is a sense in which one can say that energy is a dimension just like time and that's as I spoke of it above, i.e. energy is a dimension of a 4form, namely the energy-momentum 4-form just like time is said to be dimension of spacetime. Although that's a sloppy use of the term dimension its in common use. Sigh!! Lol! go to any forum or physicist
 Jul 18th 2017, 12:26 PM #20 Banned   Join Date: Nov 2016 Posts: 63 Would you guys please stop getting hung up on the word "Dimension". I'm much more interested in you seeing what I'm envisioning not semantics.

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