The world observed through this magical eye resembles an image in the kaleidoscope, but it is not an image of colourful beads reflected from mirrors, like it was there, but the view outside the window multiplied and divided 20 times.

The magic eye resembles a plane-convex lens , but its convex surface is not spherical, and has a shape of a 'rosette' from gothic temple - an array of radiating polished plates with a little circular centre, as if it were a bunch of glass prisms. Each of those prisms deflects the light beams in the direction of the observer's pupil. We see a whole rosette of virtual images, set in a circle around the 'real' image.

The magic eye is similar to an insect eye. The eye of a fly is like a rosette; tens of little eyes on the surface of a spherical cap. Do you think a fly sees tenfold?

The multiplied images of a single source effect can also be observed in the sky. The light from distant galaxies, travelling through space which is full of massive objects, is bent in gravitational fields and reaches us in its multiplied form, as predicted in general relativity theory.

Recently, two scientists have found evidence that each galaxy is surrounded by a halo consisting of hundreds of invisible, dwarf galaxies. This discovery, published in 'The Astrophysical Journal', supports strongly the theory claiming that most of matter in the Universe has the form of undetectable particles, called cold dark matter, which travel slowly in Space. An astrophysicist Neal Dalal from the University of California and Christopher Kochanek from Harvard-Smithsonian Center for Astrophysics in Cambridge have based their conclusions on the analysis of gravitational lensing. According to Einstein's theory of gravitation, massive objects, for example galaxies, curve space-time continuum and bend light passing them around. Due to that phenomenon light can be focused as if in a lens.

The diagram shows, how multiplied images of one object are created (two in our case) between the source object and the observer as a result of bending.

The picture is a classic example of gravitational lensing. Multiplied images of one distant quasar have been created as result of space-time continuum curving by a galaxy which is closer to the Earth.