The "stress of grief" in cosmology recently raises questions about the standard cosmological model
One of the biggest mysteries in cosmology is the rate at which the universe is expanding. It can be predicted using the standard model of cosmology, called cold dark matter (ΛCDM). This model is based on detailed observations of the light left over from the Big Bang - the so-called cosmic background radiation (CMB).
The expansion of the universe causes galaxies to move away from each other. The farther they are from us, the faster they move. The relationship between the speed and distance of a galaxy is determined by the "Hubble constant", which is approximately 70 km per second per megafarsec (a unit of measurement in astronomy). This means that a galaxy adds about 80,000 km/h for every million light years of distance from us.
But unfortunately for the standard model, recently there has been controversy about this value, which has caused what scientists call "the grieving stress". When we measure the expansion rate using nearby galaxies and supernovae, it is 10% greater than the CMB-based prediction.
In the new article a possible explanation is presented: we live in a huge void in space (a space with below average density). The authors show that this can inflate local measurements through inflows of material from the void. Such flows will appear when denser regions surrounding a void tear it apart - they exert a greater gravitational pull than the less dense material within the void.
In this scenario, we would have to be close to the center of a void with a radius of about a billion light years and a density about 20% below the average of the universe as a whole - so not completely empty.
Such a large and deep emptiness is not predicted in the standard model - and therefore different in the department. The CMB gives a snapshot of the structure of the infant universe, from which it emerges that the matter today should be fairly uniformly distributed. But a direct count of the number of galaxies in different regions does show that we are locally empty.
The researchers wanted to further explore this idea by fitting many different cosmological observations with the assumption that we live in a great void that evolved from a small density fluctuation in the early days.
To do this, their model did not include ΛCDM but an alternative theory called modified Newtonian dynamics (MOND).
MOND was originally proposed to explain anomalies in the rotation speed of galaxies, and this led to the idea of an invisible substance called "dark matter". MOND suggests instead that the anomalies can be explained by Newton's law of gravity breaking down when the gravitational pull is very weak - as happens in the outer regions of galaxies.
The overall history of the expansion of the universe in MOND will be similar to the Standard Model, but structure (such as galaxy clusters) will evolve faster in MOND. The new model captures what the local universe might look like in the MOND universe, and is found to allow for a fluctuation of local measurements of the expansion rate today that depends on our location.
Recent observations of galaxies have allowed a new critical examination of the proposed model based on the velocity it predicts at different locations. This can be done by measuring something called volumetric flow, which is the average speed of matter in a given sphere, dense or not. It varies with the radius of the sphere, and recent observations show that it continues up to a billion light years.
Interestingly, the volumetric flow of galaxies of this size is four times the speed predicted by the standard model. It also seems to increase with the size of the examined area - contrary to what the standard model predicts. The probability of fitting the standard model is less than one in a million.
This prompted the researchers to check what their study predicts about the volumetric flow, and a fairly good match with the observations was found. This requires that we are fairly close to the center of the void, and that the void is the emptiest in the center.
These results come at a time when popular stress solutions are in trouble. Some believe we simply need more accurate measurements. Others think the matter can be resolved if we assume that the high rate of spread we measure locally is actually the correct rate. But this requires a slight adjustment of the expansion history of the early universe so that the CMB still looks fine.
More of the topic in Hayadan:
Comments
to me. Porat:
Not really. There are two studies here, one based on a different level of sampling. It is the broad sample, which is the most convincing, that seems to support MOND.
MOND seems to be in big trouble lately. See for example: https://www.youtube.com/watch?v=i4lu9AxRtqA
Nervous silence, enough to disturb
The standard model of cosmology is imaginary, and has nothing to do with physical reality.
There is a new model described in the Asbar Bidyan archive, and it is described in dozens of innovative articles.
In the new model there is an infinite geometric volume, full and not empty.
The infinite volume is full of passive time and energy.
Combining amounts of passive time and energy, creates a physical form.
Adding quantities of a closed length containing an amount of area creates a geometric shape.
The elements gold, carbon, hydrogen, are a form of physics
Star matter is formed from physical forms,
The stars move in an infinite geometric volume full of passive time and energy, and this fullness does not hinder their movement.
Search the Asbar archive, and you will come to a new physics, which does not have gravity, and to a new geometry of circles.
In this physics there is a new universe containing a finite collection of stars, and this universe moves forever in a straight line, at a speed of C12
The stars of the universe move naturally, in helical orbits, and this form of orbit groups them all into one dynamic division.
A. Asbar