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Gravitational lensing demonstration

You will need:

  • 1 wine glass
  • A surface with a speckled black background that simulates the night sky (we used a kitchen countertop)


    Wine glass on speckled black kitchen counter
    Wine glass on a speckled black kitchen counter


  1. This science demonstration is so simple! Place the wine glass upright on a background that simulates the night sky. We used a kitchen counter top but you could also use a photo or poster of the night sky or even make an artwork with galaxies, nebulae and stars.

    Base of a wine glass on a kitchen counter top
  2. While you watch the base of the wine glass stem, slowly move the glass around on the pretend night sky backdrop. Notice how the glass distorts the images of the patterns below the glass?

  3. This distortion is not that much different from what occurs to starlight when a very heavy celestial object passes across the front of a distant star!
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Science behind the experiment

The heavier the object, the more gravity it has. Very heavy objects such as black holes or clusters of objects such as galaxies can have a lot of gravity. When these heavy objects pass in front of a distant star, galaxy or nebulae, the light from those distant objects can be bent by the heavy object passing in front.

Why? Well, it turns out that gravity seems to be a consequence of space being warped by an object. The heavier object, the more the space surrounding the object gets warped. As light travels towards us from a distant object it can follow the bent space around the heavy object and as such the heavy object can act like a lens! 

This effect means that astronomers can actually look around massive objects like galaxy clusters for the focal point of light coming from even further distant objects. Once that focal point is found you have effectively used the galaxy clusters itself as part of a giant cosmic telescope.

NB: more correctly; space & time are linked together so technically both space & time can get warped by heavy objects (called spacetime).

Gravitational lensing diagram by NASA 495578main herschelB20101104  Image credit: NASA/JPL-Caltech
Gravitational lensing diagram by NASA. Image credit: NASA/JPL-Caltech

More information about gravitational lensing by NASA and


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