Space is terrifyingly empty. But inside that emptiness, there are things so dense they shouldn't even exist. Most of us just call them black holes. It’s a catchy name. It’s iconic. But if you’re hanging out with an astrophysicist or digging through a 1950s physics journal, you’re going to hear a lot of other labels. Honestly, "black hole" is a bit of a newcomer to the linguistic scene.
For a long time, we didn't have a name for them because we weren't sure they were real. They were just math problems that refused to behave.
Karl Schwarzschild was the guy who first crunched the numbers back in 1916, right in the middle of a world war. He wasn't thinking about sci-fi names. He was thinking about "singularities." He was looking at Einstein’s equations for General Relativity and realized that if you cram enough mass into a small enough space, the math literally breaks. It goes to infinity.
So, what is another name for black hole? Depending on who you ask and what era they’re from, you might hear "frozen star," "collapsar," or the rather intimidating "gravitational singularity." Each of these names tells a different story about how we tried to wrap our tiny human brains around something that swallows light for breakfast.
The era of the Frozen Star
Before the 1960s, the term "black hole" didn't really exist in the public lexicon. Back then, researchers in the Soviet Union—specifically giants like Yakov Zel'dovich and Igor Novikov—preferred to call these objects frozen stars.
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It sounds poetic, right? But the logic was purely based on time dilation.
According to Einstein, gravity warps time. The closer you get to a massive object, the slower time ticks for you compared to someone far away. If you were to watch a star collapse into a black hole from a safe distance, you’d never actually see it finish the job. Because gravity becomes so intense at the edge—the event horizon—light shifts into the red spectrum and time appears to stop. To an outside observer, the star seems to "freeze" just as it vanishes. It becomes a ghost. A frozen relic of a dying sun.
Western scientists weren't super into that name. They found it a bit misleading. The star isn't actually frozen; it's still collapsing, it just looks that way because of how light behaves. This is a classic example of how scientific naming conventions often depend on where you live and which university is funding your telescope.
Why "Collapsar" almost won the naming war
In the mid-20th century, another name for black hole that gained some serious traction was collapsar.
Short for "collapsed star," it’s probably the most accurate description of what these things are. Most black holes are born when a massive star runs out of fuel. Without the outward pressure of nuclear fusion to hold it up, the star’s own gravity wins the tug-of-war. It implodes.
The term collapsar is still used today, but it’s shifted in meaning. Astronomers now usually reserve "collapsar" for a very specific event: the collapse of a massive, rapidly rotating star that leads to a long-duration gamma-ray burst. If you hear a scientist at NASA talking about a collapsar, they’re usually talking about the violent, high-energy birth of a black hole, not just the black hole itself.
It’s kind of like the difference between saying "a car" and "a car crash." One is the object; the other is the event.
The Singularity: Where physics quits
If you want to sound like a real expert, you call it a gravitational singularity.
This is the term you’ll find in heavy-duty academic papers. A singularity is basically a point in space where the density is infinite. Think about that for a second. It's not just "very dense." It is infinitely dense. The volume is zero.
At this point, our current understanding of physics—the stuff we teach in high school and even most grad schools—just stops working. General Relativity and Quantum Mechanics get into a fistfight at the singularity and nobody wins.
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- Point Mass: Sometimes used in simpler physics models to describe a black hole's center.
- Spacetime Puncture: A more metaphorical way some theorists describe the way a singularity "rips" the fabric of reality.
- The Central Fire: An old, almost alchemical way some early theorists thought about the intense energy, though this has mostly fallen out of fashion.
How we actually got the name "Black Hole"
There's a bit of a myth that John Wheeler invented the term "black hole" in 1967. He definitely popularized it, but he didn't invent it.
The name actually started appearing in print a few years earlier. A journalist named Ann Ewing used it in a 1964 article for Science News Letter to describe a meeting of the American Association for the Advancement of Science. Before that, it was reportedly used by engineers and physicists as a sort of "shorthand" for the "gravitationally completely collapsed stars."
Wheeler liked it because it was punchy. It was better than saying "Schwarzschild's singularity" or "hypothetically collapsed gravitational object" every five minutes. It stuck. People loved the mystery of it. It sounded dangerous.
Dark Stars and the 18th Century
Long before Einstein was even born, a clergyman named John Michell wrote a letter to the Royal Society in 1783. He had this crazy idea. He wondered if a star could be so massive that its escape velocity was faster than the speed of light.
He called them dark stars.
He figured that if light couldn't escape, the star would be invisible to us. He was 100% right, though he was using Newtonian physics, which we now know doesn't quite work for light. Still, the concept of a "dark star" is basically the OG another name for black hole. Pierre-Simon Laplace came up with a similar idea independently a few years later. For over a hundred years, the idea of dark stars was treated as a mathematical curiosity—a "what if" that nobody really expected to find in the real world.
Why the names matter
You might think this is just semantics, but the name we choose changes how we visualize the universe.
When we say "black hole," we visualize a void. A hole in a sheet. A drain.
When we say "frozen star," we visualize time and light.
When we say "collapsar," we visualize the violent process of gravity.
In the last decade, we've even started categorizing them by their "weight." You’ll hear terms like SMBH—Supermassive Black Hole. These are the monsters that live in the center of galaxies, like Sagittarius A* in our own Milky Way. They have the mass of millions or billions of suns. Then there are IMBHs (Intermediate-mass) and Stellar-mass black holes.
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We’ve even theorized about Primordial Black Holes. These would be tiny black holes, some as small as an atom but with the mass of a mountain, formed in the chaotic seconds right after the Big Bang. We haven't found one yet, but the search is a huge part of modern dark matter research.
Common misconceptions about the "Hole"
Honestly, the biggest problem with the name "black hole" is that it isn't a hole. It’s the opposite of a hole. A hole is empty space. A black hole is the most "stuff" you can possibly pack into a single area.
If you were to fall into one (which, please don't), you wouldn't fall "through" a tunnel to another dimension—at least, probably not. You’d just be crushed into the singularity. You become part of the mass. You’re adding to its weight.
Some people use the term Gravastar as a theoretical alternative. A Gravastar is a hypothetical object that looks like a black hole from the outside but doesn't have a singularity inside. Instead, it has a core of "exotic energy" that prevents the collapse from going to infinity. Most scientists are skeptical, but it's a valid mathematical model that tries to fix the "infinite density" problem that makes physicists so uncomfortable.
Next Steps for the Curious
If you want to dig deeper into the actual science behind these names, stop looking at "pop science" articles and start looking at the actual data.
- Check out the Event Horizon Telescope (EHT) website. They are the team that took the first-ever photo of a black hole (M87*). They explain the difference between the "shadow" and the "photon ring."
- Look up "Kerr Metrics." This is the math for rotating black holes. It's much more complex than the standard Schwarzschild model because, in the real world, almost everything in space is spinning.
- Search for "Hawking Radiation." This is the process by which black holes actually leak energy and eventually evaporate over trillions of years. It’s the bridge between thermodynamics and gravity.
Knowing the right terminology helps you navigate the actual research. Whether you call it a frozen star, a collapsar, or a singularity, you're talking about the most extreme environments in the known universe. The names are just our way of trying to make the impossible feel a little more familiar.