Only Spacetime

[Pugdaddy]

When I mentioned that I thought the theory of particles moving through spacetime didn't intuitively sound right. Strange asked me post something in speculations with math. Unfortunately I don't have the math background to do that. But I did find a book by John A Macken that was saying basically the same thing I was think of. That particles are really just pieces of spacetime and not particles in spacetime. Has anyone reviewed this? Does the theory make sense? Does the math back up the theory?

Thanks.

http://onlyspacetime.com/Chapter_5.pdf

[swansont]

There isn't much math in that, and what little there is doesn't explain very much.

[Pugdaddy]

Ok. Thanks. Is this about the same thing with more math?

https://arxiv.org/pdf/1606.07210.pdf

[MigL]

If space-time can be considered a field, then quantizing it will lead to quantum particles as 'excitations' of the field according to QFT.

 

These particles would not be pieces of the field , or pieces of space-time as you say, but are a manifestation of the field.

[madmac]

Pugdaddy.

Particles being pieces of spacetime sounds like aether to me.

Particles in spacetime aint aether.

 

I had a quick look at the article. I like much of the theory of particles & waves. Some of it smells like aether theory.

It mentions dipole waves in spacetime.

It says that the spacetime field is the stiffest possible medium.

It calls gravity a force at least once.

[Pugdaddy]

Pieces was in hind sight a poor representation. Manifestations are a much better representation. Doesn't particle theory characterize a particle as entities separate from spacetime that travels through It? If particles are an excitation of the spacetime field, could not these excitations of the spacetime field disturb the spacetime field in the vicinity of the excitation changing the geometry of the surrounding spacetime field? Could this geometric change in the surrounding spacetime field affect how other excitations in the spacetime field move in the spacetime field? Could this be what is observed as gravity?

[madmac]

Pugdaddy.

So, gravity might be (1) an excitation of the space-time field that (2) disturbs the space-time field, which (3) then changes the geometry of the space-time field, which (4) then affects other how other types of excitation in the space-time field move.

 

I think that (1)(2)(3)(4) are indeed in effect mainstream Einsteinian gravity.

Except that i think that (4) should not refer to other types of excitation, it should refer back to the original (1) excitation.

 

But if the meaning of (4) is not other types, but the same type but other occurrences, then i wonder why if it affects other occurrences does it not affect the originating occurrence.

[Pugdaddy]

I was watch the Ligo video and the energy to form the gravitational wave they detected was about 3 solar masses and that caused spacetime to stretch and relax a thousandth of the size of the proton. If there is a spacetime field as is being theorized, that is a pretty stiff medium.

[imatfaal]

I was watch the Ligo video and the energy to form the gravitational wave they detected was about 3 solar masses and that caused spacetime to stretch and relax a thousandth of the size of the proton. If there is a spacetime field as is being theorized, that is a pretty stiff medium.

 

I haven't even done a back-of-the-envelope calculation but I would just say that whilst that is a supreme amount of energy for a very small change - it is over a sphere of unimaginable size. That black-hole interaction was 1.6 billion light years away - and we felt it! Admittedly we only felt it with the most sophiticated tool every built - but all the same.

 

The maths behind the quadrapole gravitational radiation is nasty - I know that the signal is not uniform around the sphere but I have a feeling that the energy radiated is uniform. That stretch/squeeze that we felt was one part of the ringdown - with a maximum amplitude as you have said. So that three solar masses worth of converted energy did not just deform one bit of spacetime less than a thousandth of the width of a proton - it distorted vast unimaginable swathes of spacetime many many times . So maybe it is stiff maybe not so much - but you need to do more sums to say for sure

[Pugdaddy]

I found this. It looks like the stiffness of spacetime can be "??? inferred" from the Stress Energy Momentum Tensor in Einsteins field equation. And from that "??? inference" the speaker suggests that spacetime is " ridged and stiffer than any substance that we think of in our 3D world".

2.07 x 10 to the -43 seconds squared per kilogram meter.

 

[imatfaal]

Not sure if that is entirely kosher - it is basically saying that the stiffness of spacetime is the coefficient between the Einstein Tensor G and the Stress-Energy Tensor T. Now that makes quite a lot of sense in heuristic terms G describes the curvature of spacetime, and T describes the stuff that is making it curve; it makes sense that the multiplier is related to the stiffness. The speed of light to the fourth power on the bottom means that is gonna be a small small number.

 

But I think of stiffness as being measured in Newtons per metre - not seconds squared per kilogram metre. I also think of stiffness being a number which the higher it is the harder it is for a certain amount of oompf to distort something (being deliberately vague); ie you need more Newtons to produce a displacement in the SI measure of stiffness

 

The 8 pi G over c^4 is in the wrong position for that - the higher that coefficient the easier it is to produce distortion. I think that number would be better called flexibilty (the inverse of stiffness - think of resistance and conductivity) - but I am quite prepared to believe that space time is very stiff, but not entirely convinced yet.

 

---

 

Thinking a bit further - if you think of it as 1/stiffness that would be metres / Newton

 

metres / Newton = metres / (kilogram . metres per second^2)

= seconds^2 per kilogram

 

Which is very similar to the dimension you gave from your video, but not exact which is disturbing. It is not the same as the inverse of pressure either which I think would make a lot of sense (Youngs Modulus has same units as pressure)

[Pugdaddy]

Young's modulus relates stress, which is in this case is the energy put into spacetime, to the strain, which is the distortion or curvature of spacetime. Just speculating here, but isn't strain considered dimensionless which is why the units are units of pressure. If we consider the strain to be the curvature and has dimensions, does that change anything?

Just as an aside, my real name is Thomas Young. But I bear no resemblance physical or intellectual to the 19 century British physicist I share the name with.

Edited March 6, 2017 by Pugdaddy

[imatfaal]

Young's modulus relates stress, which is in this case is the energy put into spacetime, to the strain, which is the distortion or curvature of spacetime. Just speculating here, but isn't strain considered dimensionless which is why the units are units of pressure. If we consider the strain to be the curvature and has dimensions, does that change anything?

Just as an aside, my real name is Thomas Young. But I bear no resemblance physical or intellectual to the 19 century British physicist I share the name with.

 

Yes it would change things - I would have to think what the resultant dimensions would be.

 

And Thomas Young is a pretty cool scientist to share a name with

[Pugdaddy]

Consider the spacetime field as an energy density field. We have a candidate in dark energy. Dark energy is smooth on a large scale as we do not see any local effects. It is persistent as it does not go away as the Universe expands. In a lecture I saw by Sean Carroll he suggested that dark energy was a constant. 10^-8 ergs/c^3. Could dark energy be the spacetime field?