As light flies through the Universe, we might suppose that it will travel along a straight line. This turns out not to be the case: light rays can be bent by the effects of gravity in the Universe. Wherever there is a clump of matter, there is a slight gravitational distortion of space and time; the light that passes near such a clump will therefore be deflected. We call this bending of light “Gravitational Lensing”.
This leads to striking images of distant galaxies, where their appearance has been stretched and magnified by gravitational lensing. In the most extreme cases multiple images of a single background source are observed. These ‘strong’ gravitationally lenses are very rare, requiring alignments to within 1/3600th of a degree. ‘Weak’ lensing is common: every distant source is distorted slightly as it travels through our inhomogeneous Universe.
ICG researchers are using both strong and weak lensing to study the objects causing the gravitational lensing, the expansion of the Universe, and the behaviour of gravity itself.
ICG staff working in this field include: