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Name: Carla
Status: student
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Question:
I have always heard that black holes, are, well, holes...but lately on science channels they are depicted as black spheres -- like black stars. So are they convex like a sphere, or concave like a hole?



Replies:
Hi Carla,

The more correct answer of the two is that the shape of black holes is basically spherical (although technically, they deviate from perfect spheres). The shape changes depending on if the black hole is charged or spinning, and where and how much matter is flowing in to it.

The "hole" shape you are describing sounds like a diagram of a gravity well, which is a diagram of the gravitational force (actually the gravitational vector) around a black hole. This diagram describes the strength of the gravitational field, but is not a depiction of the shape of a black hole. You may want to read about "gravitational wells"; there are many articles (and pictures) available on-line.

Hope this helps,

Burr Zimmerman


The illustrations are representing different things. The event horizon of the black hole is represented as a semi conical hole with sloping sides. The actual body is represented as a sphere.

Of course, since we cannot look into a black hole and recover information, neither representation is anything more than a way to draw an illustration.

R. W. "Bob" Avakian
Instructor
B.S. Earth Sciences; M.S. Geophysics
Oklahoma State Univ. Inst. of Technology


Carla,

A black hole, caused by the gravitational pull of an extremely dense piece of matter at its center, is essentially spherical. A standard hole needs to have an open side. A black hole looks the same from all sides. Some descriptions show what a black hole might look like in a two-dimensional model of a three-dimensional universe. This is a way to show how a black hole might affect things, but it does not show the shape of a black hole.

A block hole looks like a hole because no light comes from it. Your eyes cannot see it and cannot see through it. This makes it look like a piece of space is missing, but really there is material within the spherical border of the dark zone.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College



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