Astronomical observations suggest that a significant part of the universe is made up of dark matter which interacts with the rest of the universe only through the gravitational pull.
- Many large lab experiments have tried to detect elementary particles that could be candidates for dark matter. However, such dark matter particles have not been detected until now.
- The researchers use the non-observation of the lensing signatures to assess what fraction of the dark matter could be made of black holes. Gravitational lensing is useful to cosmologists because it is directly sensitive to the amount and distribution of dark matter.
- Gravitational lensing is an effect of Einstein’s theory of general relativity – simply put, mass bends light.
- The gravitational field of a massive object will extend far into space, and cause light rays passing close to that object (and thus through its gravitational field) to be bent and refocused somewhere else.
- The more massive the object, the stronger its gravitational field and hence the greater the bending of light rays – just like using denser materials to make optical lenses results in a greater amount of refraction.
- Dark Energy is a hypothetical form of energy that exerts a negative, repulsive pressure, behaving like the opposite of gravity.
- It is causing the rate of expansion of our universe to accelerate over time, rather than to slow down.