Asking AI, "Do Black Holes Have Mass"?
Introduction
Ever since ChatGPT told me that House Atreides made its money from training Sardaukar troops, I’ve been cautious about what I ask AI—and how I ask it. I’ve learned to be very specific in my prompts and to verify AI responses when it comes to factual information.
But what happens when the topic I’m asking about is far outside my area of expertise? How can I know whether the answer I’m getting is accurate?
To explore this, I asked three different AI sources the same question: “Do black holes have what is commonly referred to as ‘mass’?”
Don’t laugh. I saw a reference to “intermediate mass black holes” in my Bluesky feed this morning, and it got me wondering—how can we even measure mass in a black hole, given their spacetime distortions? Here’s how three sources answered the same question.
ChatGPT
Yes, black holes do have what is commonly referred to as "mass."
In fact, mass is one of the most fundamental and measurable properties of a black hole, along with spin (angular momentum) and electric charge (if any). According to the no-hair theorem in general relativity, these three quantities fully describe a black hole from the outside — its mass being the most commonly discussed.
What does "mass" mean in the context of a black hole?
A black hole’s gravitational effects on surrounding matter and light (such as the orbits of stars around it or the bending of light near it) directly indicate its mass.
The mass of a black hole is concentrated at a single point (the singularity) according to classical general relativity, although quantum theories suggest a more nuanced picture.
From a distance, the black hole’s mass behaves just like any other object's mass in terms of its gravitational pull.
How do we measure it?
For stellar-mass black holes, we observe how they affect nearby stars in binary systems.
For supermassive black holes, we observe the motion of stars and gas clouds around galactic centers (e.g., the star orbits near Sagittarius A* in the Milky Way).
So, while a black hole is not made of ordinary matter anymore, it absolutely possesses mass in the same sense as any other object with gravitational influence.
Claude
Yes, black holes definitely have mass. In fact, mass is one of the fundamental properties that defines a black hole.
Black holes form when massive stars collapse under their own gravity, and they retain the mass of their progenitor star (minus any material that may have been ejected during the collapse). The mass of a black hole determines several of its key characteristics:
Event horizon size: The radius of the event horizon (called the Schwarzschild radius) is directly proportional to the black hole's mass
Gravitational influence: The black hole's gravitational field extends outward and affects nearby matter and spacetime according to its mass
Tidal forces: More massive black holes create stronger tidal effects on objects approaching them
We can measure black hole masses through various methods, such as observing the orbital motion of companion stars in binary systems or tracking the movement of stars near supermassive black holes at galactic centers. Black hole masses range from a few times our Sun's mass (stellar-mass black holes) up to billions of solar masses (supermassive black holes found at galaxy centers).
So while black holes are regions where matter has collapsed to extreme density, they absolutely retain and are characterized by their mass, which continues to warp spacetime and exert gravitational influence on their surroundings.
Perplexity
Black holes do have what is commonly referred to as mass. In fact, mass is one of the primary properties that defines a black hole and determines its gravitational influence on other objects in the universe.[1][2][3]
A black hole is not a literal "hole" but rather a region of space where an enormous amount of mass is packed into a very small volume, creating gravity so strong that not even light can escape. The mass of a black hole comes from the matter and energy that originally formed it (such as a collapsing star), plus anything that subsequently falls in. This mass is concentrated in an extremely small region, typically called a singularity, and is surrounded by a boundary called the event horizon.[1][4][5][6][3]
There is a continuous range of black hole masses, from a few times the mass of the Sun (stellar-mass black holes) to millions or billions of solar masses (supermassive black holes). The gravitational effects a black hole produces — both on its immediate environment and on objects far away — can be explained as if all its mass were concentrated at a single point at the center.[7][2][8][5][3]
Although the interior of a black hole (including the singularity) is not fully understood, especially at the quantum level, its total mass behaves according to the same gravitational rules as any other massive object. Thus, black holes can be weighed by their influence on other stars, gas, and light around them.[9][2]
Important caveat: While black holes “have mass,” the nature of that mass and how it is distributed inside remains an open question in fundamental physics, with classical and quantum theories offering different models for what happens at the core.[9][4]
Why Does a Black Hole Have a Finite Mass? – Physics Stack Exchange
ELI5: How Can a Black Hole Have Mass If There Is No Matter? – Reddit
Conclusion
OK, it sure looks like black holes *do* have mass.
All three answers agree on that basic fact. Perplexity provides the most direct links for follow-up, which makes it especially useful when you're diving into unfamiliar territory. That said, I know from experience that ChatGPT (via my paid subscription) can also provide links upon request, so that’s not a major differentiator.
I particularly appreciate ChatGPT’s nuanced line:
“The mass of a black hole is concentrated at a single point (the singularity) according to classical general relativity, although quantum theories suggest a more nuanced picture.” I also like Perplexity’s “Important caveat: “While black holes “have mass,” the nature of that mass and how it is distributed inside remains an open question in fundamental physics, with classical and quantum theories offering different models for what happens at the core.“
Ultimately, I’d be satisfied with any of these responses. Not bad for a topic I have no formal training in—just a long-standing curiosity, nurtured by a few astronomy related books.
Copyright © 2025 by Dennis D. McDonald
