# How to Build a Model of a Black Hole

Black holes, contrary to popular myth, are not like vacuum cleaners essentially sucking in everything around them, nor are they portals allowing travel through time or to other dimensions. According to NASA, a black hole can be considered the "end point of massive stars" and should be thought of as a "singularity" following a large star's implosion. The gravitational pull surrounding this singularity holds onto things so greatly that even light cannot escape its grasp, thus forming the "black hole." The surface of the black hole is often referred to as the "event horizon" and for something to be pulled into a black hole it must pass the radius of this event horizon, known as "Shwarzschild radius."

### Things You'll Need

• Sports bandage or other very stretchy fabric
• Small marble
• Heavy ball
• Scissors
• Several helpers

## Instructions

• 1

Cut the bandage into a large square, as large as possible. Ideally, the square should be about 12 to 15 inches to provide the best representation of a black hole.

• 2

Hold the fabric square by the corners and sides and pull the fabric, with the help of others, making a smooth, taut surface. This is a representation of space in a basic two-dimensions. Space isn't flat, but consider it a slice of space for demonstration purposes, which may help younger children comprehend the example.

• 3

Roll the small marble across the surface of the fabric or bandage. This shows how an object moves in regular space, generally keeping a straight path provided it is not interrupted by contact with another object or the gravitational pull of a celestial body (planet, moon) or black hole.

• 4

Place the heavy ball in the center of the fabric, instructing everyone to hold on tightly so as not to let the fabric slip. Even while holding and pulling on the fabric, the center of the square will pull downward with the weight of the heavy ball, curving the fabric around it as it forms a "hole" (though not a complete hole, since the fabric is still supporting the ball from underneath). In essence, this is similar to space being curved by the presence of a black hole.

• 5

Roll the marble across the fabric again, trying to produce the same path as before. With the weight of the heavy ball on the fabric, the marble cannot accomplish the same path across the fabric, but instead is pulled in toward the heavy ball which is curving the fabric (space) toward itself.

The larger the ball used to represent the black hole, the greater the curve to the fabric (space) which is also representative of the effect of black hole sizes. Once the marble gets close to the "black hole" it is pulled into the area and cannot simply roll out of its own accord.

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