Activity: Warped Space-Time Model

Students will -

1. make observations of a teacher demonstration that modes a space-time continuum warping caused by gravity.

A 15-minute demonstration

High school

Einstein simplified the treatment of gravity by treating it as if it simply changed the shape of space. Within this warped space, all objects continue to move according to Newton's First Law of Motion and any apparent change in direction is simply because of changes in the curvature of space.

• 5 x 5 square of black spandex
• 2 - 5 x 1/4 dowel rods
• 2 - 1 x 2 boards
• Embroidery hoop
• Steel marble
• Safety pins
• String
• Miscellaneous masses with hooks

Frame and Space-Time Continuum

1. Fold over a 3 flap along each edge of the spandex and sew to produce a sleeve along each side of the fabric.

2. Drill one 1/4" hole halfway through each end of both 1 x 2 boards. Place each hole as near to the end of the boards as possible. The 1/4" dowels will stretch between the two boards at each end to produce a square frame.

3. Slip the 1/4" dowels through sleeves on opposite sides of the square fabric. Do the same with the 1 x 2 boards with the remaining two sleeves. Fit each dowel into the drilled 1/4" holes of the 1 x 2 boards.

4. Set the frame across and between two tables so that only two opposing edges are resting on the tables. Cut a circular hole in very center of the spandex that is 1 inch smaller in diameter than the embroidery hoop.

5. Pull the edge of the spandex around the cut-out circle into the embroidery hoop. Close the hoop to form a frame that pulls the spandex down. This represents a black hole. (If the hole is not deep enough, attach masses along the edge to pull the fabric down, making the hole deeper.)

6. Use safety pins and string to attach masses in various places around the bottom side of the fabric. These represent other medium mass objects like planets and stars.

Procedure

1. Align two tables so the frame can lie between them. Have students gather around.

2. Roll the marble across a corner that remains relatively flat and explain that in the absence of gravity, space is planar and objects in motion move in straight lines.

3. Explain that objects with mass warp space-time so the course of traveling objects is altered. Roll the marble across or/and around a few of the medium mass objects.

4. Explain that if an object's speed is slow enough and/or the warping of space by the objects is great enough, objects can get trapped and crash into the planet or star, or the object can get sucked into the black hole, never to return.

5. Explain that many objects are neither sucked into the massive objects to be destroyed nor able to completely escape its influence. Instead they may move into any number of elliptical-like orbits. Explain that the planets in our system tend to orbit in nearly circular orbits. Demonstrate a circular orbit with the marble. Other objects, like comets, however, take on long elliptical orbits, when they are near the orbited object they speed up and when farther away, they slow. Again, demonstrate with the marble.