Spacetime is doomed?

[The Photon]

Any ideas from physicists that will replace spacetime? Will spacetime be replaced by some underlying material aether medium that light waves propagate on and visible matter as disturbances in the medium? There's superfluid vacuum theory but I don't know what the photons and matter is in the theory, and the speed of sound in the superfluid may exceed the speed of light. String theorists like Gross and Witten also predict the emergence of spacetime from something more fundamental.

What evidence to date leads physicists to replace spacetime with something else?

[beecee]

1 hour ago, The Photon said:

What evidence to date leads physicists to replace spacetime with something else?

Nothing.

[The Photon]

Really? So spacetime is then here to stay? I am hoping so, because replacing spacetime with something else just makes the rabbit hole go deeper.

[beecee]

5 hours ago, The Photon said:

Really? So spacetime is then here to stay? I am hoping so, because replacing spacetime with something else just makes the rabbit hole go deeper.

What Rabbit hole is that? We are able to give a real logical evidenced based description, of the evolution of spacetime from t+10-43 seconds, up until today, including the creation of our first fundamental particles, atomic nuclei, the lightest elements, gravitational collapse and stars, planets as well, the heavier elements, more stars and planets, abiogenisis and the evolution of life. What more would you like?  With regards to spacetime, so far we are able to determine and locate events with this framework, with three spatial coordinates and the time coordinate quite successfully. The concept of this framework devised due to the observation that "ç" is constant and remaining constant independent of the motion or speed of the emmitter or the receiver.  Spacetime gives us  a description of reality that is common for all observers in the universe/space/time irrespective  of their relative motions. Your space and time varies from my space and time. And of course when this framework we call spacetime is twisted, warped, curved, we see an effect exhibited that we know as gravity, which along with the BB,  describes the overwhelmingly supported GR.

If you are inferring a verifiable QGT, and as a professional Astronomer once told me, such a QGT will more then likely entail and encompass the BB and GR, so heavily supported be these models,  while extending beyond their zones of applicability. Much as GR extended and described far more precisely, the large scale effects of gravity the likes of the precession of the perihelion of Mercury. Worth noting at this time that [as far as I know] Newtonian mechanics has been sufficiently accurate enough for all space exploratory endeavours.

 

 

Edited March 24, 2019 by beecee

[swansont]

12 hours ago, The Photon said:

Any ideas from physicists that will replace spacetime? Will spacetime be replaced by some underlying material aether medium that light waves propagate on and visible matter as disturbances in the medium?  

The notion of a material aether was discarded a long time ago.

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What evidence to date leads physicists to replace spacetime with something else?

I’m not aware of any. Relativity is a fantastically successful theory.

[StringJunky]

14 hours ago, The Photon said:

Any ideas from physicists that will replace spacetime? Will spacetime be replaced by some underlying material aether medium that light waves propagate on and visible matter as disturbances in the medium? There's superfluid vacuum theory but I don't know what the photons and matter is in the theory, and the speed of sound in the superfluid may exceed the speed of light. String theorists like Gross and Witten also predict the emergence of spacetime from something more fundamental.

What evidence to date leads physicists to replace spacetime with something else?

I think spacetime is a feature of the leading new theories, so it isn't going away.

[The Photon]

@beecee The rabbit hole of what underlies something understood as fundamental. If spacetime is emergent then it is emergent from something more fundamental, which would need a whole new set of theories for whatever spacetime emerges from.

3 hours ago, swansont said:

The notion of a material aether was discarded a long time ago.

I’m not aware of any. Relativity is a fantastically successful theory.

True, the speed of light as a constant still holds to this day with no need for a physical medium. Yes, General Relativity is very successful, but the problem is with linking Quantum Mechanics and General Relativity, and gravity. Gravity is not treated with the SM of Particle Physics as there is no QFT for gravity. What little I know of LQG, space and time are quantized, probably also emergent from something more fundamental. In string theory, spacetime is likely to be emergent also.

1 hour ago, StringJunky said:

I think spacetime is a feature of the leading new theories, so it isn't going away.

It is, but string theorists, LQG theorists and other physicists have the idea that space and time is emergent from something more fundamental than space and time. Nima Arkani-Hamed is vocal about it for example.

[beecee]

1 hour ago, The Photon said:

@beecee The rabbit hole of what underlies something understood as fundamental. If spacetime is emergent then it is emergent from something more fundamental, which would need a whole new set of theories for whatever spacetime emerges from.

We have no validated theory of anything before 10-43 seconds, from where space and time [as we know them] evolved from the quantum foam or if you like the spacetime foam. https://en.wikipedia.org/wiki/Quantum_foam  The large fluctuations characteristic of a spacetime foam would be expected to occur on a length scale on the order of the Planck length.[10]A foamy spacetime would have limits on the accuracy with which distances can be measured because the size of the many quantum bubbles through which light travels will fluctuate. Depending on the spacetime model used, the spacetime uncertainties accumulate at different rates as light travels through the vast distances" 

 

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It is, but string theorists, LQG theorists and other physicists have the idea that space and time is emergent from something more fundamental than space and time. Nima Arkani-Hamed is vocal about it for example.

Many ideas and speculative scenarios abound, but as yet no observational or experimental evidence to support or validate such concepts.

Edited March 24, 2019 by beecee

[Phi for All]

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[Spaceman Spiff]

On 3/23/2019 at 9:56 PM, The Photon said:

Really? So spacetime is then here to stay? I am hoping so, because replacing spacetime with something else just makes the rabbit hole go deeper.

If I understand Photon's analogy correctly, then "rabbit holes" are good, and It can/will go plenty deep for (x,y,z,t) spacetime - [and I have some ideas about that].  I believe your rabbit hole is just another name for the thread of knowledge.  If I use the rabbit hole for Matter as an example, it would have started with things being "made" of some combination of fire, air, water & earth.  Later we figured out molecules, then atoms, then atomic particles.  Now I believe that that particular rabbit hole currently stops at quarks, but who's to tell that in in the not too distant future, quarks will no longer be considered the "fundamental/elementary" constituent of matter?