Stretch And Squash

(A Processing application to show how a gravitational wave distorts space)

Daniel Brown

October 2009

A new edition of this app is now available at the Laser Labs pages!

Gravitational waves come in two distinct polarisations, called `plus' and `cross'. Similarly to light fields these polarisations describe the direction of the wave's oscillation perpendicular to the direction of propagation. `Plus' and `cross' polarisations can also be combined to create more complicated patterns such as elliptical or circular polarisations. The application below illustrates the different effects that gravitational waves in different polarisations would have on space. (The gravitational waves are passing straight through your computer screen!) - If you want to know more about the polarisation and the wave nature of gravitational waves you can find more information online, for example on Wikipedia or at Einstein Online.

The youtube video below shows a short screencast of the program in action.

This program is provided as a stand-alone application (not as an applet that runs in a browser). To run this application please download the appropriate file, unzip it and start the executable in the StretchAndSquash folder. You must have Java installed for the application to work. The version for Mac OS can use a web camera input in addition to the provided images, if a suitable camera is found by the program.

You can use the following key commands:

  • <ESC>: end application
  • <SPACE>: pause application
  • p: switch between `plus', `cross' and `circular' polarisation
  • v: switch between different images and web camera (if available)
  • i: switch between two different types of image smoothing (one mode is faster, the other looks better)

The application has been built with Processing. It was programmed for the 2nd ET general meeting October 2009, during a part-time research project at the University of Birmingham, UK. See also our other Processing examples.