If we can't see it, then we can't find out anything about 'em?

Psssh! It may be black, but it's not completely hidden! We can tell the size of the event horizon (the black hole's "mass"), whether it's charged or not, and whether it's spinning and at what rate. Remember that a star can collapse to form a black hole? All information about what the star is made of is lost. The star could have been made of antimatter or matter, and it wouldn't make a difference in the resulting black hole. We can't peer past the event horizon to see the singularity...even if we could, the singularity is a damn strange place. If the collapsing star were not quite spherical, those deviations were burned off during the collapse, so all black holes have the same general shape. What differs from hole to hole is the mass, charge, and angular velocity.

Three types of black holes

Static (a Schwarzschild black hole) Green Circle: for black hole beginners Covering such diverse topics as ... Why is it called a static black hole? Photon sphere Event horizon Why is it called the event horizon? What happens when you cross the event horizon?      While braking      While in freefall Beyond and to the singularity!

Charged (a Reissner-Nordstrøm black hole) Blue Square: for intermediate black hole fans Running the gamut of curiosities such as... Photon Sphere Event horizons Practicality intrudes with a catch Standard singularity

Rotating (a Kerr black hole) Black Diamond: for black hole experts Introducing eclectic ideas such as... What's a rotating black hole? Two photon spheres? What's between the photon spheres? Ergosphere Familiar horizons Ring around the singularity

What's with the green circle, blue square, black diamond stuff?

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