A half a century old theory predicting the existence of bodies labeled Generic Objects of Dark Energy (GEODEs) is getting a second look due to a proposed correction in the assumptions made to model the way our Universe expands. If this new form of a classic cosmological model is right, some black holes may perhaps hide cores of pure dark energy, pushing our Universe apart at the seams.
University of Hawai’i astrophysicist Kevin Croker and mathematician Joel Weiner joined hands to challenge the broadly accepted view that when it comes to the Universe’s growing circumference, its contents are largely irrelevant.
Croker said, “For 80 years, we’ve generally operated under the assumption that the Universe, in broad strokes, was not affected by the particular details of any small region. It is now clear that general relativity can observably connect collapsed stars – regions the size of Honolulu – to the behaviour of the Universe as a whole, over a thousand billion billion times larger.”
This alternative interpretation of fundamental physics could potentially change how we understand the Universe’s expansion, but we also might need to consider how such growth might affect compact objects such as the cores of collapsing stars. The fact that space has been steadily covering more area for the past 13.8 billion years is by now a widely accepted feature of our Universe.
The set of equations commonly used to describe this expansion was first proposed on paper almost a century ago by the Russian physicist Alexander Friedmann. These offered a solution to Einstein’s theory of general relativity that now fortifies our big-picture model of cosmology.
Although Friedmann’s equations have proved to be very useful, they’re built on the assumption that any matter floating around inside this expanding space is more or less composed of the same kind of stuff that is spread out fairly evenly. This implies that we tend to ignore the swirls of stars and galaxies similar to how we might not include ducks in the hydrodynamics of a lake.
But Croker and Weiner wondered what might happen to space and its constituent objects if some reasonable changes were made to the assumptions that give rise to these equations. The consequences aren’t inconsequential. Their adjusted model shows that the averaged contributions of our metaphorical ducks might affect the lake’s water considerably.
Moreover, the lake’s expansion would also affect how the ducks swim, instigating them to lose or gain energy depending on their species. Hypothetically, this interpretation would infer that we need to take the Universe’s growth into account whenever we describe certain phenomena like the death of a star.
In 1966, a Russian physicist named Erast Gliner pondered how some densities of space close to the Big Bang might appear in terms of relativity just like a vacuum that could counter the effects of gravity.
His solution would be similar to a black hole from the outside. But inside, it would be like a bubble of energy shoving against the surrounding Universe. Half a century later, astrophysicists are on the lookout for a similar pushing power that might be responsible for the Universe’s expansion picking up speed over time. Now, we refer to this undescribed force as dark energy, but now the question arises that are Gliner’s pockets of relativistic nothingness the source of our Universe’s accelerating expansion?
According to Croker and Weiner’s work, if just a limited number of ancient stars collapsed into Gliner’s GEODEs instead of the more characteristic puckered space of a singularity, their average effect on expanding space would resemble dark energy. The pair pursued further, applying their corrected model to the first measured observation of gravitational waves from a black hole collision by LIGO.
To make the math appropriate, it’s supposed that the stars that shaped the merging black holes originated in a low-metallicity environment, making them somewhat rare. Technically, the energy of a GEODE should progress as the Universe grows, effectively compacting as a cosmological equivalent of a ‘blueshift’. According to the researchers, if the merging black holes were GEODEs, it will no longer be necessary to assume that black holes were born in an unusual patch of space.
The researchers whose work was published in The Astrophysical Journal, said, “What we have shown is that if GEODEs do exist, then they can easily give rise to observed phenomena that presently lack convincing explanations. We anticipate numerous other observational consequences of a GEODE scenario, including many ways to exclude it. We’ve barely begun to scratch the surface.”
Testing assumptions such as these are a vital part of physics. A lot more is needed to enroll GEODEs in any official astrophysical zoo of weird objects, but it’s now a possibility that these could be the dark hearts of the Universe we’ve been looking for.