Astronomer's Toolbox

Black Holes

Try this!

Do not use any commas in your answers! To make the Earth into a black hole, it would have to be squeezed down to a radius of 0.86 centimeters, about one-half the size of a golf ball.

1. Using the following equation, confirm the radius of the black hole for the mass of the Earth.

   R = 2MG/c²

   where M_e = 5.8 x 10²⁷g, G = 6.67 x 10^-8cm³/g/sec², and c = 3 x 10¹⁰cm/sec.

2. If you could weigh a thimbleful (about 1 cm³) of the black hole/Earth, how much would it weigh?

   x 10g

3. What would be the black hole radius of the Sun, given its mass of 2 x 10³³ gm?

   cm

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This activity was developed by Jacqueline Slay, Largo High School, Largo, MD