From the November 2012 issue

DIY gravitational lensing

Mimic the effects of massive galaxies and stars from the comfort of your own home.
By and | Published: November 26, 2012 | Last updated on May 18, 2023
The power of gravity can warp a distant galaxy’s light (the blue rings) all the way around a nearer galaxy (the reddish blobs), as in these examples from the Hubble Space Telescope. // Credit: NASA/ESA/SLACS Survey team
In his January story, Ray Villard delved into the physics and uses behind “How gravity’s grand illusion reveals the universe.” Thanks to the space-time-warping properties of mass, a big enough object like a galaxy or even just a star can alter the path of light traveling near it. As Villard explains, this isn’t just a fun quirk of the universe — it’s a valuable tool that allows astronomers to see farther than they otherwise could and map what otherwise would be completely invisible.

To better understand this amazing phenomenon, it’s possible to re-create some of its effects using household items. All you’ll need is a pinpoint light source, such as a halogen desk lamp, and a wine glass. Simply look through the base of the glass toward the lamp from a few yards away, and observe as the base’s rim arcs, smears, and perhaps even multiplies the light. Here, the curved glass acts as an analog to the gravitationally warped space (so the star, or nearer galaxy, in terms of Villard’s examples), with the lamp acting as the distant light source. If you align the wine glass perfectly, the lamp’s light will form a ring around the glass base, forming the equivalent of an Einstein ring.
Naturally, distorting a lamp’s light in a wine glass is fundamentally different from distorting a galaxy’s light around a massive object, but the effects are largely the same. For an idea as complicated and powerful as gravitational lensing, it’s nice to be able to get a “grasp” on a similar idea; and whenever the cosmos proves too overwhelming to comprehend, perhaps the contents of a wine glass might prove similarly useful.