In general relativity, the presence of matter can curve spacetime, and the path of a light ray will be deflected as a result. This process is called gravitational lensing, analogous to the deflection of light by (e.g. glass) lenses in optics.In rare and extreme cases, light can take different paths to the observer and more than one image of the source will appear.Strong gravitational lensing is lensing that is strong enough to produce these multiple images, arcs, or even Einstein rings. Many useful results for cosmology have come out of using this phenomena.
Dr. Simon Birrer, Stanford, will shed more light on how astronomers are utilizing strong gravitational lensing to probe the nature of dark matter and dark energy, the dominant but yet unknown components of our Universe.
We have made the difficult decision to postpone the lecture scheduled for March 18th due to the current status of the COVID-19 virus. Our speaker chair, Linda Mahan, will be working to schedule the speaker at a later date. We will keep you posted on when that will be.
See more details here.