There’s no Such Thing as Gravity:
The World Just Sucks!

A slightly different approach to general relativity
for high school physics students

By Mark Sowers

Chapter 7:
Gravity and Light

Remember from chapter 1: a mirage appears when light is bent due to one part of the light-wave moving more slowly than another part. Light bends towards the region of slower propagation. In the case of the hot road, light is bent upwards, towards the more-dense air, where light propagates more slowly.

Time-gradients affect light in exactly the same way. When light passes through a time-gradient, part of the light-wave moves more slowly than another part. The path of the light is bent.

Light bends around massive objects like stars and galaxies because time slows down in their vicinity. As a result objects behind a star or a galaxy don’t appear where they should. They appear as a mirage.

This special type of mirage is called “gravitational lensing”. Scientists use the term “lens” because when talking about stars and galaxies the time-gradient spreads out around them in a sphere. Light passing to the left of a massive object is bent towards the right, while light passing to the right of a massive object is bent to the left. The time-gradient focuses and even magnifies light, just as a lens would.

Scientists use this effect of gravitational lensing to do some remarkable research. If light from a distant quasar flows around a massive object, like a galaxy, the light is magnified. This allows scientists to study objects that are much farther away than those that we can directly see.

Gravitational lensing is also important in the research into something called dark matter. When looking at a galaxy, astronomers can measure how much mass they can see. From that they can predict how much that galaxy should bend light. However it turns out that every galaxy bends light much more than it should. This is one piece of evidence that leads scientists to the conclusion that there must be something else in the galaxy that we can’t see. There must be some kind of dark matter that is making the galaxy more massive than it appears.