Swarms of ‘primordial’ black holes might fill our universe

The universe might be full of tiny, ancient black holes. And researchers might be able to prove it.



a star filled sky with Great Blue Hole in the background: a black hole


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a black hole

These mini black holes from the beginning of time, or primordial black holes (PBHs), were first dreamed up decades ago. Researchers proposed them as an explanation for dark matter, an unseen substance that exerts a gravitational pull throughout space. Most explanations for dark matter involve hypothetical particles with special properties that help them evade detection. But some researchers think swarms of little black holes moving like clouds through space offer a cleaner explanation. Now, a new study explains where these PBHs might have come from, and how astronomers could detect the aftershocks of their birth.

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Where did the little black holes come from?

A black hole is a singularity, an infinitely dense point in space packed with matter. It forms when that matter gets so tightly packed that the force of gravity overwhelms everything else, and the matter collapses. It warps space-time and surrounds itself with an “event horizon,” a spherical boundary region beyond which no light can escape.

The laws of general relativity allow black holes to exist at any scale; crush an ant hard enough and it will collapse into a black hole just like a star; it’ll just be incredibly tiny.

Most PBH theories assume these objects have masses like small planets, with event horizons as small as grapefruits. It’s an outlandish idea, still on the fringe of black hole and dark matter physics, said Joey Neilsen, a physicist at Villanova University who was not involved in the new study. But recently, as other dark matter theories have turned up empty, some researchers have given the PBH notion a second look.

If PBHs are out there though, they have to be very old. In the modern universe, there are only two known methods for creating new black holes from normal matter: stars much heavier than the sun colliding or exploding. So every known black hole weighs more than the entire solar system (sometimes much more).

Related: Is our solar system’s mysterious ‘Planet 9’ really a grapefruit-size black hole?

Making small black holes requires a whole other set of mechanisms and ingredients.

Those ingredients would be “the stuff of the Big Bang, the same stuff that makes the stars and galaxies,” Neilsen told Live Science.

Right after the Big Bang, the newly expanding universe was full of hot, dense largely-undifferentiated matter expanding in all directions. There were small pockets of turbulence in this morass — still visible as fluctuations in the Cosmic Microwave Background (CMB), the afterglow of the Big Bang — and those fluctuations gave the universe structure.

“If it’s a little more dense at point A, then stuff is gravitationally attracted to point A,” Neilsen said. “And over the history of the universe, that attraction causes gas and dust to fall inwards, coalesce, collapse and form stars, galaxies, and all the structures in the universe that we know of.”

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College coaches still scrambling to fill hoops schedules

College coaches endured a tense time waiting for the NCAA to green light the 2020-21 basketball season.

They knew there was a window the NCAA was looking at to start, likely sometime in late November or early December. They just didn’t have a date. So they did the best they could to prepare for the big moment, yet still found themselves in a scramble once it actually happened.

Even now, six weeks before tipoff, teams are struggling to fill out schedules as the clock keeps ticking.

“We were trading a lot of phone calls, trying to come up with the best solutions,” said Anthony Ruta, director of basketball operations under Arkansas coach Eric Musselman. “You need time because you’re trying to juggle a bunch of different things. You’re trying to check a lot of boxes along the way without compromising yourself in other areas.”

College football ended up with a scattershot plan for starting its season, leaving it up to the various conferences. As a result, some conferences are already playing while others, like the Pac-12 and Big Ten, are still waiting for their seasons to kick off.

The NCAA took a more unified approach to the basketball season, saying it would set a start date for all teams in all conferences.

Word came down in mid-September, when the NCAA said the season will begin on Nov. 25.

Then the scramble began.

Coaches kept in touch with opponents on their original schedules to make sure they were both on the same page. A multitude of factors had to be sifted through.

Because the season was originally slated to begin in early November, the later start date meant several games on the schedule would have to be pushed to another day or eliminated. Many teams don’t want to travel long distances during a pandemic, so finding regional opponents became a priority.

Teams also had to sort through contracts with previously scheduled opponents and work around uncertainties as leagues across the country try to work out conference schedules.

“The problem is we already had the schedule,” West Virginia coach Bob Huggins said. “(Director of basketball operations Josh Eilert) had done a great job, had us a great nonconference schedule, and then we had to just about totally blow it up and start all over again. It’s been as tough as I can remember in 43 years.”

The NCAA reduced the maximum number of regular-season games from 31 to 27 if a team plays in a multi-team event. The max is 25 without a multi-team event.

One of those, the Maui Invitational, was moved to Asheville, North Carolina. The Battle 4 Atlantis in the Bahamas was canceled and several teams slated to play there are headed to South Dakota instead. The Cancun Challenge was moved from Mexico to Florida and the Empire Classic from Madison Square Garden to the Mohegan Sun in Connecticut.

Many teams are opting to play in smaller events, like the four-team Little Apple Classic at Kansas State and the

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