Japanese scientists have put together a new model that explains some of the biggest mysteries of the universe: the absence of black holes and the possible existence of dark matter.
The results of this study were published in a peer-reviewed academic journal Physical inspection letters.
If true, the results of this research will help paint a more thorough picture of the early universe and the structure of the cosmos itself.
Cosmic Puzzles: Black Holes, Dark Matter, and the Birth of the Universe
This study deals with some very complicated and still not fully understood concepts in astrophysics, so let’s break it down one by one.
First, let’s start with the simplest: the universe itself.
The age of the universe is estimated to be approximately 13.8 billion years. While it started incredibly small, it has since exploded into the almost infinite space we all know today. Since the Big Bang, the universe has gone from this small singularity to a paradoxically busy but empty space, populated by stars, galaxies, and other structures, while also having a vast amount of emptiness.
But the cosmic microwave background (CMB) is also present in space. These are essentially remnants of the Big Bang itself and can be found everywhere.
Now let’s talk about dark matter.
Simply put, we don’t know what dark matter is. We think of dark matter as an invisible mass that exists throughout the universe, making the collective mass of everything in the universe much heavier than it appears.
Dark matter is a theoretically invisible substance that does not emit any light and makes up more than 85% of the matter in the observable universe. The Standard Model of cosmology also states that it is vital to the continued evolution of the universe.
We know it exists—allegedly, as some researchers still debate its existence—because of gravity. Gravity as we know it is explained by Albert Einstein’s general theory of relativity. Anything that cannot be explained by this is usually considered to be due to the influence of dark matter.
However, some researchers have proposed another possible explanation for dark matter, and that’s our next topic: black holes.
Black holes are massive concentrations of gravity so strong that nothing, not even light, can escape, making them invisible. Like dark matter, the only way scientists were able to tell they existed was through gravity, and like dark matter, they play a key role in the function of the universe.
Unlike dark matter, which is so mysterious that some scientists doubt it even exists, black holes are a very well-established scientific fact. Most of them are formed when a large star dies, which plays a major role in the life cycles of stars and galaxies.
But the research also suggested that black holes may not only form when stars die. Rather, they may have existed since the beginning of the universe.
These hypothetical black holes from the dawn of the universe are known as primordial black holes (PBHs) and would predate the birth of stars.
But in addition to solving many other mysteries, such as the discoveries of massive galaxies in the early universe that were not supposed to be able to form at the time with the James Webb Space Telescope, scientists also think they could solve another mystery: dark matter.
Black holes are incredibly dense and heavy, so in theory they could help explain the extra mass in the universe attributed to dark matter. Plus, they could help explain other mysteries. But it all depends on one thing: There must be enough of them in the universe. And so far, scientists have not been able to find them.
“Since the recent innovation of gravitational wave astronomy, there have been discoveries of binary black hole mergers, which can be explained by the fact that PBHs exist in large numbers,” said graduate student Jason Kristiano. “But despite these strong reasons for their expected abundance, we haven’t seen any directly, and now we have a model that should explain why this is so.”
Research into the formation of primordial black holes has problems with the researchers behind the study. For example, the CMB does not seem to support the leading proponents of how these black holes would form.
So when researchers encountered a model that seemed to contradict the established CMB data, they did the only thing they could: They corrected the model to ensure it was consistent with the data.
“In the beginning, the universe was incredibly small, much smaller than the size of a single atom. Cosmic inflation quickly expanded this by 25 orders of magnitude. At that time, waves traveling through this small space could have relatively large amplitudes, but very We found that these small but powerful waves may translate into the otherwise unexplained amplification of much longer waves we see in the present CMB,” said Prof. Jun’ichi Yokoyama, director of the Research Center for the Early Universe (RESCEU) and Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI) at the University of Tokyo.
“We believe it’s because of occasional instances of coherence between these early short waves that can be explained using quantum field theory, the most robust theory we have to describe everyday phenomena like photons or electrons. Whereas individual short waves would be relatively powerless.” , coherent groups would have the power to reshape waves much larger than themselves. This is a rare case where a theory of something at one extreme scale seems to explain something at the opposite end of the scale.
So we are dealing with wavelengths and fluctuations. The idea is quite complex, but to put it simply, small fluctuations in the early universe actually affect larger fluctuations in the CMB. That’s a big deal, but it matters because it gives new implications for anything that depends on these kinds of wavelengths.
And it is precisely these short but powerful wavelengths that are thought to create primordial black holes.
Overall, primordial black holes should still exist. But based on this new model, there might not be as many as previously believed.
But this is all theoretical for now. What is needed is some real research to back this up. Fortunately, a joint observing mission between the US, Italy and Japan is doing just that: studying what are likely to be primordial black holes.
The results of this study will determine how accurate this model is.