Perturbations

• Perturbations are detected through the examination of large maps that show the distribution of matter at various times and scales.
• The best evidence for dark matter comes from attempts to understand perturbations in cosmic background radiation.
• Photon trajectories are deflected when they travel around a mass, e.g. deflection of light by the sun during an eclipse.
• Lensing distorts anisotropies in light and can be recovered statistically; future measurements can allow for the determination of the mass of neutrinos.