“There are two sides to gravity: In part, gravity is an observer artefact: it can be made to vanish by going into free fall. Most of the gravity that we experience here on earth when we see objects falling to the ground is of this type, which we might call "relative gravity". The remainder of gravity, "intrinsic gravity", if you will, manifests itself in tidal forces, and is associated with a specific property of geometry: The curvature of spacetime.” From Einstein Online http://www.einstein-online.info/elementary/generalRT
Assumed Preparation: It is recommended but not essential that
the students be introduced to the equivalence principle before this lesson.
Subversive Physics: This part of general relativity
is harder to fit into a physics course than the equivalence principle. However
it could be used in a math class as enrichment for the geometry unit. It also
would help in an astronomy or Earth-space science course. In a pure physics
course it fits in best as an illustration of how science progresses, to round
off a unit on gravity or just for fun.
The Activities: The students work in small groups
with a guided inquiry sheet and a variety of physical models to explore the
effects of curved spacetime. You will need the curved
spacetime worksheet.
a) Balloons are used in an open actvity that lets students explore how the rules
of geometry on a curved space are very different.
b) A simple paper diagram helps illustrate the precession of Mercury, the first
confirmation of Einstein's theory.
c) A bowl and masking tape are used to see how a curved space will bend light
and form gravitational lenses.
d) Stretchy fabric and balls are used to create a gravity well and cause orbitting.
This is used to explain how gravity waves are formed.
If your students enjoyed this, why not do the next lesson 4) General Relativity: Gravity Causes Black Holes.
Further Information:
Dr. Quantum visits Flatland is a 5-minute film that explores how hard it is
too imagine extra dimensions. It is loosely based on the classic book Flatland
by Abbott Abbott http://www.youtube.com/watch?v=BWyTxCsIXE4