Rubber Sheet Analogy Fails To Explain Gravity

Since spacetime warping can be a difficult concept to understand and visualise an analogy is often used in physics education.

Rubber sheet analogy fails to explain gravity.

Explanation this comic refers to a common analogy used to explain how mass distorts space time a bowling ball resting on a sheet of rubber distorts the sheet due to its weight. The rubber sheet or trampoline analogy for gravity is flawed because it is not fully three dimensional as a real star and planets would be. Let me try the ant analogy in a bit more detail. On a flat rubber sheet a trained ant has no trouble walking in a straight line.

The rubber sheet analogy only works even for the orbits if you assume that the orbiting object tends to want to roll down hill in the dip made by the bowling ball. Spacetime can be thought as a thin rubber sheet. The analogy presented therein is somewhat similar to the rubber sheet one but does away with the weight in the center. It s often misused to show that mass warps spacetime 895.

The right hand side of this pair of drawings is closer to real life but still not accurate. Imagine a 2d spherical shell embedded in 3d space. They both begin walking parallel to each other northward toward the one of the poles. Two people are located side by side on the equator of this sphere.

The system has some qualitative features in common with gravity. Indeed physicists have known for ten years that a rubber sheet deformed by a central mass can never take on a shape that reproduces the gravitational effects of spacetime. Is there no gravity. In space it will follow a straight line and go over any hole on the surface.

All analogies are flawed that s why they are analogies and not scientific theories. The dented rubber sheet done in earth s gravity is a not too bad analogy for newtonian gravity. Figure 24 8 three dimensional analogy for spacetime. But a ball rolls on a surface because gravity is pulling it down.

The way masses warp the rubber sheet and affect other smaller masses can help students develop an intuitive understanding of how gravity works under gr. When a massive object creates a big depression in the sheet the ant which must walk where the sheet takes it finds its path changed warped dramatically. The ants walk forward. Just placing an object somewhere in that dip will result in it rolling down the slope towards the bowling ball.