In 1970 Hawking suggested that dark matter, the invisible substance that makes up most of the matter in the universe, might be made up of black holes that formed during the early days of the Big Bang. Now astronomers have developed a theory that explains not only the existence of dark matter but also the appearance of the largest black hole in the universe.
"What I personally find really interesting about this idea is how it elegantly brings together two very challenging problems that I'm working on, namely investigating the nature of dark matter and the formation and growth of black holes and solving them in one fell swoop," said an astrophysicist at the University. Yale.
What's more, several new instruments including the recently launched James Webb Space Telescope could produce the data needed to finally assess Hawking's famous ideas.
There was a black hole from the start
Dark matter makes up more than 80 percent of all matter in the universe but does not interact directly with light in any way. It just floats to a large extent affecting the gravity in the galaxy. It is likely that black holes are responsible for everything that happens in the universe. Unfortunately, in the modern universe black holes form only after massive stars die and then collapse under the weight of their own gravity. So making a black hole would have to take a lot of stars to make normal matter. Scientists know how much normal matter was in the universe from calculations of the early universe, where hydrogen and helium first formed. There is not enough normal matter to make up all the dark matter astronomers have observed. That's where Hawking comes in. In 1971 he revealed that the so-called primordial black hole or primordial black hole was formed after the Big Bang. There, pockets of matter can spontaneously reach the density needed to create a black hole, flooding the cosmos with them long before the first stars twinkled. Hawking suggested that these primordial black holes may be responsible for all dark matter.
Research Results Based on Hawking's Theory
In the new study, astronomers Natarajan and Nico Cappelluti at the University of Miami and Günther Hasinger at the European Space Agency delve into the theory of primordial black holes, exploring how they explain dark matter and perhaps solving other cosmological challenges. To pass the test, a primordial black hole must be within a certain mass range. In the new work, astronomers assume that the primordial black hole had a mass about 1.4 times the mass of the Sun. They built a model of the universe that replaced all dark matter with these fairly bright black holes and then they looked for observational clues that could validate the model. Astronomers discovered that primordial black holes could play a major role in the universe by seeding the first stars, the first galaxies, and the first supermassive black holes (SMBHs). Observations showing that stars, galaxies, and SMBHs emerged so rapidly in cosmological history may be too fast to be explained by the formation and growth processes we observe in the universe today.
"Primordial black holes if they did exist could be the seeds from which all supermassive black holes were formed including those at the center of the Milky Way." Natarajan said.
The theory is simple and does not require a new collection of particles to explain dark matter.
"Our study shows that without introducing new particles or new physics, we can solve the mysteries of modern cosmology from the nature of dark matter itself to the origins of supermassive black holes," Cappelluti said.
So far the idea is just a model but it can be tested. Meanwhile, the James Webb Space Telescope, launched on Christmas Day after years of delay, will answer questions about the origin of stars and galaxies. The next generation of gravitational wave detectors especially the Laser Interferometer Space Antenna (LISA) is poised to reveal more about black holes including primordial black holes if they exist.
Stephen Hawking's Bizarre Theory That Is Proven True and Still a Question Mark
Starting with his doctoral thesis in 1966 his groundbreaking work continued relentlessly until his final paper in 2018 was completed just days before his death at the age of 76. His theories often seemed odd at the time he formulated them. But slowly it was accepted scientifically with new supporting evidence emerging later. From his astonishing views on black holes to his explanation of the humble beginning of the universe, here are some of his theories that have been proven correct and some that remain unanswered.
1. The Big Bang Theory
Hawking got off to a great start with his doctoral thesis on two competing cosmological theories: the Big Bang and the Steady State. Both of these theories accept that the universe is expanding but the former expands from an ultra-compact or super-dense state at a finite time in the past, while the latter assumes the universe has been expanding forever with new matter constantly being created to maintain the same density. constant. In his thesis, Hawking showed that the Steady State theory is mathematically self-contradictory. Instead, he argues that the universe began as a very small, dense point called a singularity. Today, Hawking's description is almost universally accepted among scientists.
2. Black hole
Hawking's name is associated with a black hole that forms when a star collapses under its own gravity. It emerged from Einstein's general theory of relativity that was debated for decades when Hawking turned his attention in the early 1970s. Ingeniously he combined Einstein's equations with those of quantum mechanics, turning what was previously a theoretical abstraction into something that seems to actually exist in the universe. . The evidence turned out to be true when in 2019, the Event Horizon Telescope obtained live images of the supermassive black hole lurking at the center of the giant galaxy Messier 87.
3. Hawking radiation
Black holes are said to have gravity so strong that photons or light particles should not be able to escape from them. But in his early work on the subject, Hawking argued that there was more to this truth. Applying quantum theory in particular to the idea that pairs of "virtual photons" could be spontaneously created from nothing, he realized that some of these photons would appear to radiate from black holes. This theory is now referred to as Hawking radiation and was recently confirmed in laboratory experiments at the Technion-Israel Institute of Technology. In place of the black hole the researchers used the acoustic analogue of a "sonic black hole" where sound waves are trapped and cannot escape. They detected Hawking radiation which was exactly what physicists predicted.
4. The area theorem of black holes
The recent discovery of gravitational waves emitted by the merging of black hole pairs suggests that Hawking was right again. Hawking said the observed nature of the system is consistent with predictions about black holes in 1970, that the area of the last black hole is greater than the total area of the original black hole." More recent observations have provided further confirmation of Hawking's "area theorem".
Apart from the proven theory, there are still several theories that have not been proven, such as the following:
1. The information paradox
The basic properties of materials that make black holes appear lost forever. Hawking's own opinion of the mystery is that it is not actually lost but is stored in a cloud of zero energy particles surrounding the black hole which he dubs "soft hair." But Hawking's hairy black hole theorem is only one of several hypotheses that have been put forward and to date no one knows the real answer.
2. An ancient black hole
Black holes are created by the gravitational collapse of pre-existing matter such as stars. But it's also possible that some were created spontaneously in the very early universe after the Big Bang. Hawking was the first to explore the theory behind these primordial black holes in depth. It turns out that they can have any mass from the very light to the very heavy although the very small will "evaporate" into nothing due to Hawking radiation. One interesting possibility that Hawking considered is that primordial black holes may be the mysterious dark matter that astronomers believe permeates the universe. But the observational evidence to date suggests that this is not possible.
3. Multiverse
One of the topics Hawking tinkered with towards the end of his life was multiverse theory, namely the idea that our universe with its beginnings in the Big Bang was just one of an infinite number of coexisting bubble universes. In his last paper in 2018, Hawking attempted to "try to tame the multiverse." He proposed a new mathematical framework which, while not eliminating the multiuniverse altogether, made it finite. But as with speculation about parallel universes we don't know if the idea is correct. And it seems unlikely that scientists will be able to test the idea any time soon.
4. Time Traveler
Einstein's theory of general relativity includes a "closed time-like curve" that effectively allows you to travel back in time on your own. Hawking feels that traveling back in time creates a logical paradox that shouldn't be possible. Until now we do not know whether time travel can actually happen or not.
5. Doomsday predictions
In the last years of his life Hawking made a series of predictions about the future of mankind. This draws on suggestions that the elusive Higgs boson that mentions triggers a vacuum bubble that will devour the universe to alien invasions and the takeover of artificial intelligence (AI). While Stephen Hawking is right about many things we expect him to be wrong about this.
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