# Models for making sense of relativity - physical space vs physical spacetime

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What part about those calcs on those hyperlinks equate to Lorentz ether. Which is a 4d model not a 3d model Don't you understand?

I repeat you compared Galilean relativity to SR.

Not Lorentz ether to SR in that link.

What is the transformation equation for absolute time Tim.?

$\acute{t}-t=0$

Edited by Mordred

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For completeness: I use the one way speed of light definition as in http://fourmilab.ch/etexts/einstein/specrel/www/

Thus the speed of light along x' of S' is c-v with respect to S' according to S.

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still doesn't change the detail you have 4 independant variables. 4 independant variables literally means 4 dimensions.

t,x,y,z

Edited by Mordred
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What part about those calcs on those hyperlinks equate to Lorentz ether. Which is a 4d model not a 3d model Don't you understand?

I repeat you compared Galilean relativity to SR.

Not Lorentz ether to SR in that link.

[..]

I definitely explained Lorentz ether; you know very well that SR uses the math of Lorentz ether, and I explained in great detail how.

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you keep calling it 3d when it is not 3d. I don't care if you prefer Lorentz ether over SR. At least call it a 4d model as it is properly called

It has 4 coordinates that are independant.

by any definition it is a 4d model

Edited by Mordred
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Your way of describing things risks to confuse people. Please understand that Newton's model also used x,y,z,t.

Moreover Lorentz ether is an interpretation of SR, and block universe is another interpretation of SR. Regretfully it remained a bit unclear what exactly the block universe interpretation means, but that's because we could not find a true "block" believer to explain it to us.

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t in Newtons law is not independant

Recall the transformations between Galilean relativity and Lorentz T is not needed to transform under Galiliean relativity. Thats why its 3d.

Galilean Relativity

$t=\acute{t}, x=v\acute{x}, y=\acute{y}, z=\acute{z}$

Time is variable between frames. This is the identical transformation SR uses.

Lorentz ether

$t=\gamma\acute{t}, x=\gamma\acute{x}, y=\acute{y}, z=\acute{z}$

Your way of calling Lorentz ether 3d is flat out false.

Edited by Mordred
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In other words, you would call clocks and animals "4 dimensional objects"?? To me that's highly uncommon use of language.

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Thats a useless argument. Any math definition states the number of independant variables is the number of dimensions. Thats basic math.

The number of independant variables =number of graph axis.

In Lorentz Ether you have 4 axis to graph

Not 3 hence spacetime diagrams. 3 dimensions of space with orthogonal axis+1 of time. Orthogonal simply means at 90 degrees to each other.

Edited by Mordred
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In other words, you would call clocks and animals "4 dimensional objects"?? To me that's highly uncommon use of language.

Yes, Einstein and relativity is 'uncommon use of language' for laymen ;-)

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In other words, you would call clocks and animals "4 dimensional objects"?? To me that's highly uncommon use of language.

You are correct.

Conceptually, a 4 dimensional object cannot "exist" because to "exist" need time.

1D, 2D 3D objects can exist. Meaning by that that they can be embedded in the 4th dimension

For a 4D object to "exist" would need the existence of a 5th dimension in which it could be embedded and "exist".

IOW the objects must have a dimension less than the universe in which they exist.

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Conceptually, a 4 dimensional object cannot "exist" because to "exist" need time.

1D, 2D 3D objects can exist. Meaning by that that they can be embedded in the 4th dimension

For a 4D object to "exist" would need the existence of a 5th dimension in which it could be embedded and "exist".

IOW the objects must have a dimension less than the universe in which they exist.

Hello Michel.

Where did you get these ideas from?

You seem rather mixed up about dimensions and embedding.

You embed an n dimensional object in a space that has at least n+1 dimensions.

An n dimensional object is part of an n dimensional spce, it is not embedded.

A n dimensional object will not fit into a space of less than n dimensions.

However it is possible to map an n dimensional object into a space of lower dimension. This is called a projection, which is the subject of projective geometry.

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Hello Michel.

Where did you get these ideas from?

You seem rather mixed up about dimensions and embedding.

You embed an n dimensional object in a space that has at least n+1 dimensions.

An n dimensional object is part of an n dimensional spce, it is not embedded.

A n dimensional object will not fit into a space of less than n dimensions.

However it is possible to map an n dimensional object into a space of lower dimension. This is called a projection, which is the subject of projective geometry.

Yes You embed an n dimensional object in a space that has at least n+1 dimensions.

In this case we do not have Space but Spacetime. Thus you embed a 3D object in a 4D Spacetime.

-------------

In the case you would have 4D objects, they could not be embedded in a 4D spacetime, you would need a n+1 dimensional "spacetime+"

Edited by michel123456
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Thats a useless argument. Any math definition states the number of independant variables is the number of dimensions. Thats basic math.

The number of independant variables =number of graph axis.

In Lorentz Ether you have 4 axis to graph

Not 3 hence spacetime diagrams. 3 dimensions of space with orthogonal axis+1 of time. Orthogonal simply means at 90 degrees to each other.

You continue to confound mathematics with physics.

Yes, Einstein and relativity is 'uncommon use of language' for laymen ;-)

You are mistaken: Einstein's relativity is characterized by the usage of common language. His writings are easy to understand, in my opinion (as I'm not a layman, I could of course overlook some parts that I think to be easy to understand for laymen while they are not!).

You are correct.

Conceptually, a 4 dimensional object cannot "exist" because to "exist" need time.

[..]

Well seen!

However, my point was merely that just because animals are living, that doesn't make them "4D objects". That's a misuse of language, a bit resembling of "Newspeak" - you know what I mean if you have read "1984".

In fact, space-time is 4D because space is 3D; and if we add force, then objects would be 5D in a space-time-force sense!

Instead of such Newspeak, I stick to normal language; and in normal language space is 3D - see also Einstein 1916.

Philosophically everyone has a right to have his own opinion, but it's not acceptable that jargon resulting from weird ideas of a minority should be imposed on the majority.

I won't further discuss such nonsense about nonstandard terminology here.

Edited by Tim88
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mathematics is the lanquage of physics. Both the Lorentz transformations and SR are modelled according to geometrical relations. Under modern treatment the Lorentz transformation tensor has 4 effective degrees of freedom. Due to having 4 coordinates.

Enough said.

You continue to confound mathematics with physics.....

I won't further discuss such nonsense about nonstandard terminology here.

You can't argue because mathematically you know I'm right. Which means according to physics I'm also right to follow the definitions not just willy nilly personal belief and incorrect terminology.

In fact, space-time is 4D because space is 3D; and if we add force, then objects would be 5D in a space-time-force sense!

Precisely what I have been telling you Thanks for agreeing. That is precisely correct.

So why aren't you following the same dimension rules for Lorentz ether? When you know it mathematically indistinguishable from SR? Though force is accounted for by use of the vectors to geometrically model spacetime under the 4 momentum.

Quite frankly though it can be argued that there is no 3d objects. You place a box on a table with two atomic clocks. With enough sampling time. You will measure time dilation within that object. Regardless of how small the box is.

Which brings up a further argument opposing 3d (Rigid objects) in that under GR there are no 3d rigid objects.

Just as in the case of taking same said object, with Earths rotation move the box left and to the right along the equator. You measure a difference in time.

So in all honesty is there any such thing as a 3d object? Quite frankly we describe that object as 3d as people are accustomed to Galiliean/Newtonian views.

Lol though a particle physicist could argue that the box has 11 dimensions.

3 spatial

1 time

1 electromagnetic (charge is reducible to a vector under a change in sign)

3 strong force Quarks etc

3 weak force.

Oops did I just describe the basis of string theory?

Technically these degrees of freedom are present in that box. Understanding this might help numerous posters understand what scientists mean by the extra dimensions beyond 4d.

Regardless it's only related to this thread as it shows a key issue on how one defines "Real"

Edited by Mordred
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Dimension Theory

Hurewicz and Wallman

Princeton University Press / Oxford University Press

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Case in point on Real. If there is no way to measure the Lorentz ether or distinquish it. Why would one consider the Lorentz ether as Real?

Isn't that being reliant on a mathematical theory that one can never measure?

In essence based upon faith of that particular math model ?

I always find that amusing.

Edited by Mordred
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No I don't, for, once more, that question was elaborate in the mother thread: http://www.scienceforums.net/topic/97105-is-space-time-a-physical-entity-or-a-mathematical-model/

Why would one consider the Lorentz ether as Real?

Tim is stuck in the idea that one NEEDS an ether to motivate light propagation.

And even if he needs one, that still doesn't give us an answer what 'real' means.

Edited by VandD
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Unfortunately a lot of people are hung up on the medium for light propagation. I've never really had a problem with that hurdle. Never really understood the hangup. Common reasoning seems to be sound requires a medium.

Yet one can simply ask. If I throw a ball do I require a medium for the ball to get from a to b ?

My physics instructor in grade 6 asked that to the class. Might have been what prevented me from getting caught on the same hangup.

Though that still doesn't define real

Edited by Mordred
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I think (a large) part of the problem with 'real' is that people seem to want it have only one meaning, rather than a range of meanings.

The English language is much better equipped than scientific people often realise.

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Unfortunately a lot of people are hung up on the medium for light propagation. I've never really had a problem with that hurdle. Never really understood the hangup. Common reasoning seems to be sound requires a medium.

Yet one can simply ask. If I throw a ball do I require a medium for the ball to get from a to b ?

My physics instructor in grade 6 asked that to the class. Might have been what prevented me from getting caught on the same hangup.

[..]

You seem to think that neither Einstein or I ever thought about that. And again you bring it up in the wrong thread, as the error in your reasoning was already clarified in the mother thread (but even more elaborated in this thread, on p.12). Just one last question here to you: do you really pretend that the cause of the speed of the ball is the same as the cause of the speed of light?

Edited by Tim88
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better question

What prevents the ball from going c?

Mass/Spacetime curvature. Not much distinction on geodesics. Just mass vs massless. What causes the ball or photon to have sufficient kinetic energy can be numerous.

PS what you call error is your opinion. I know no Lorentz ether is required to account for the geodesic relations of GR.

Quite frankly a good study of field theory quage groups under GR is more than enough to describe the above

Edited by Mordred
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You seem to think that neither Einstein or I ever thought about that.

What is your point ? we were discussing Lorentz ether not being needed. A perfectly valid argument in a thread that has discussed ether.

However as Einstein felt the ether was superfluos and not needed. Yet you seem to feel it is. Then you and Einstein disagree.

Quite frankly though I'll stick to Einsteins opinion over yours any day

Edited by Mordred
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better question

What prevents the ball from going c?

Mass/Spacetime curvature. Not much distinction on geodesics. Just mass vs massless. What causes the ball or photon to have sufficient kinetic energy can be numerous.

PS what you call error is your opinion. I know no Lorentz ether is required to account for the geodesic relations of GR.

Quite frankly a good study of field theory quage groups under GR is more than enough to describe the above

Yes, that question is much better. However, spacetime curvature concerns the mathematics; and accounting is again math. I can think of two possibilities:

1. you either deny or can't understand the need for the existence of a physical cause for the math

2. you believe in a physical Spacetime (a 4D metaphysical entity), but you dislike the term "ether" as a label for such a causal entity.

Which is it?

What is your point ? we were discussing Lorentz ether not being needed. [..]

However as Einstein felt the ether was superfluos and not needed. Yet you seem to feel it is. Then you and Einstein disagree.

Quite frankly though I'll stick to Einsteins opinion over yours any day

No, and again no! Once more, this thread is a continuation in part of the thread http://www.scienceforums.net/topic/97105-is-space-time-a-physical-entity-or-a-mathematical-model. In that thread I explained why Einstein argued that "According to the general theory of relativity space without ether is unthinkable; for in such space there [...] would be no propagation of light".

This thread discussed two variant ether interpretations:

1) a "Lorentz" ether to which Einstein at that time adhered, and

2) a "Minkowski" "4D ether" to which he later tended, as it implies a form of immortality. Note however that it's not sure if that was really what Mnkowski had in mind.

By now interpretation 1) has been sufficiently clarified, but interpretation 2) remained, regretfully, a bit obscure. And strangely, my question about one aspect of interpretation 2 (posts #234 and #238) was repeatedly hijacked for more discussion of interpretation 1 as well as for discussion of the topic "is space-time a physical entity or a mathematical model" - which is not the topic of this continuation-in-part.

Once more: the speed of light is independent of the action of the source; in this thread we follow up on the insights of Einstein and consider that it's either a function of the properties of Space (interpretation 1) or of Spacetime (interpretation 2). If there is some constructive input about Spacetime as a physical entity and how it can be understood as governing the propagation of light, I will be interested. I'm not interested in more hijacking and I won't comment on such.

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Tim descibe a particle. What is our reality. It certainly isn't our perspective. Here is a reality check for you. Every particle is a field excitation. There is no solid but simply field interactions of attraction and repulsive interactions and interferance.

A massless field excitation (photons etc) have no binding field interactions.

Massive particles do.

Every interaction/interferance contribute to spacetime curvature fundamentally we are modelling the collection of all fields under the spacetime geometry via the stress/momentum tensor.

Mass being resistance to inertia is simply a Newtonian descriptive but the rest mass is simply one contributor. The full blown contributor being the stress tensor as it tells spacetime how to curve.

This is the shift many need to take. Particles are not solid little billiard balls but excitations that exhibit both wave-like and point-like characteristics. Field excitations.

Photons travel at c simply because they don't have binding interactions in a vacuum. There is your cause.

Every field excitation will take the path of least action (potential field and particles kinetic motion)

We model this under freefall geodesics.

Quite frankly Lorentz ether is utterly useless it doesn't interact, cannot be measured. 100 percent useless. Its very properties make it useless.

A medium is simply fields, Lorentz ether is nothing more than a matter field. How can it supply momentum to keep a photon constant? It doesn't, a static field doesn't supply momentum. It causes resistance to inertia. So it doesn't cause a photon to travel at c.

Quite frankly current science has gone far beyond Einstein, Lorentz , Minkowskii, etc. We have a far better understanding of the standard model than they did.

This includes the symmetry group metrics.

Edited by Mordred

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