A recent study compared astrophysical observations with predictions based on the notion of fluid spacetime, and found the idea only works if spacetime is incredibly smooth and freely flowing — in other words, a superfluid.
Spacetime properties as emergent:
If that were the case, spacetime’s properties would “emerge" from the underlying physics of its constituents, just as water’s properties emerge from the particles that comprise it.
Photons traveling through superfluid spacetime:
This dampening effect would also happen to photons traveling through spacetime, the researchers found. Although the effect is small, high-energy photons traveling very long distances should lose a noticeable amount of energy, the researchers say.
What is tired light?
From this paper here]
From the abstract:
The position of the various tired light theories is reviewed briefly and it is noted that one of the biggest objections to them concerns the mechanism by which light might lose energy as it travels through space. Here some new work relating to the constancy of the speed of light is highlighted as providing a possible solution to this conundrum, thus making more feasible explanation of phenomena via theories involving the notion of tired light.
Tired Light Theories:
As early as 1912, Nernst had proposed the notion of the Universe being in a steady state. By 1937 he had developed the idea further and had suggested an explanation for the cosmological redshift in terms of tired light; that is, Nernst was suggesting that the æther absorbed radiation, thus causing a decrease in the energy and, therefore, the frequency of galactic light.
The concept of spacetime as a superfluid could provide the medium and the mechanism whereby light can lose energy traveling vast distances thereby producing redshifts and the possibility that the universe is static and not expanding at all.
If the universe is static, the absurd notions of the expansion of space and dark energy would be irrelevant.
The blind man who had only experienced an elephant by touching its trunk, was pretty sure that an elephant is very much like a snake. I’m pretty sure he was wrong. So I’m all for new perspectives. Can you come up with an experiment to test for the existence of spacetime as a superfluid?
The blind man who had only experienced an elephant by touching its trunk, was pretty sure that an elephant is very much like a snake. I'm pretty sure he was wrong. So I'm all for new perspectives. Can you come up with an experiment to test for the existence of spacetime as a superfluid?
We are like the blind man wrt our experience and concept of spacetime. :cheese:
There are the predictions and observational consequences, if spacetime is a superfluid.
From the wiki on superfluid vacuum theory (SVT)]
The microscopic structure of this physical vacuum is currently unknown and is a subject of intensive studies in SVT. An ultimate goal of this approach is to develop scientific models that unify quantum mechanics (describing three of the four known fundamental interactions) with gravity, making SVT a candidate for the theory of quantum gravity and describing all known interactions in the Universe, at both microscopic and astronomic scales, as different manifestations of the same entity, superfluid vacuum.
Curved spacetime, according to SVT:
According to SVT, the curved space-time arises as the small-amplitude collective excitation mode of the non-relativistic background condensate. The mathematical description of this is similar to fluid-gravity analogy which is being used also in the analog gravity models.
Cosmological constant:
Thus, in SVT this constant does not have any fundamental physical meaning and the related problems, such as the vacuum catastrophe, simply do not occur in first place.
Mass generation and the Higgs boson:
While SVT does not explicitly forbid the existence of the electroweak Higgs particle, it has its own idea of the fundamental mass generation mechanism - elementary particles acquire mass due to the interaction with the vacuum condensate, similarly to the gap generation mechanism in superconductors or superfluids.
As for the Higgs boson:
Thus, the Higgs boson, even if it exists, would be a by-product of the fundamental mass generation phenomenon rather than its cause.
Observation consequences of Logarithmic BEC vacuum theory:
The proposed theory has many observational consequences. They are based on the fact that at high energies and momenta the behavior of the particle-like modes eventually becomes distinct from the relativistic one - they can reach the speed of light limit at finite energy. Among other predicted effects is the superluminal propagation and vacuum Cherenkov radiation.
Bold added by me.
Refer to my recent post on 10,000 times faster than the speed of light here]
Photon with a tiny mass:
For instance, the photon propagating in the average interstellar vacuum acquires a tiny mass which is estimated to be about 10^−35 electronvolt. One can also derive an effective potential for the Higgs sector which is different from the one used in the Glashow–Weinberg–Salam model, yet it yields the mass generation and it is free of the imaginary-mass problem appearing in the conventional Higgs potential.
There is also the observed cosmological redshift which can be explained with SVT and "tired light" without the necessity of proposing the ludicrous unjustified notions of the expansion of space, dark energy and the expanding universe.
Disclaimer: I am a real Dummy when it comes to these kind of topics.
But it seems to me, that if SVT can more concisely explain things, and if there are observations that can be predicted and observed in accordance with it, then yeah, let’s try that perspective out. Especially if it gets rid of a need for a hypothetical construct of incredible amounts of (“dark”) energy, in the universe, that there is no way to detect. (No way to detect. How convenient.)
Disclaimer: I am a real Dummy when it comes to these kind of topics. But it seems to me, that if SVT can more concisely explain things, and if there are observations that can be predicted and observed in accordance with it, then yeah, let's try that perspective out. Especially if it gets rid of a need for a hypothetical construct of incredible amounts of ("dark") energy, in the universe, that there is no way to detect. (No way to detect. How convenient.)
From the introduction of the paper cited in my first post here]
As Disney said not too long ago [1]:
‘Cosmology rests on a very small database: it suffers from many fundamental difficulties as a science (if it is a science at all) whilst observations of distant phenomena are difficult to make and harder to interpret. It is suggested that cosmological inferences should be tentatively made and sceptically received.’
It is prudent to take cosmology "with a pinch of salt".
Wrt to dark energy, from the wiki here]
In physical cosmology and astronomy, dark energy is a hypothetical form of energy which permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate.
The hypothesis of dark energy (DE) was proposed to explain why the universe was expanding at an accelerating rate based on the observed cosmological redshifts.
However, do redshifts really indicate an expanding universe at all?
OTOH, what if redshifts are due to "tired light" and the universe is not expanding at all?
From this paper here]
The Dichotomous Cosmology with a Static Material World and Expanding Luminous World
From the abstract:
The dichotomous cosmology is an alternative to the expanding Universe theory, and consists of a static matter Universe, where cosmological redshifts are explained by a tired-light model with an expanding luminous world. In this model the Hubble constant is also the photon energy decay rate, and the luminous world is expanding at a constant rate as in de Sitter cosmology for an empty Universe. The present model explains both the luminosity distance versus redshift relationship of supernovae Ia, and ageing of spectra observed with the stretching of supernovae light curves. Furthermore, it is consistent with a radiation energy density factor (1 + z)4 inferred from the Cosmic Microwave Background Radiation.
The matter universe is static. It is only the luminous world which expands.
:cheese: