Gravitational Lenses
Gravitational Lenses in Cosmology
Using the geometry of the gravitational lens and assuming a
quasar (source) is intrinsically variable (e.g. 0957+561) the
time delay between the two images seen by the observer can be
estimated. From the time delay the Hubble constant can be determined.
Determining the Hubble Constant Using Gravitational Lenses
Angular Separation Between Light Rays
Gravitational Lensing By Cosmic Strings
The metric around a straight string is conical which implies the
existence of two paths on either side of an intervening string
from a source to an observer, who will see two images. A straight
string does not magnify or distort the images. If the source
is resolvable and lies partially inside the wedge beyond the string
that is lensed the observer will see only part of it, with a
sharp cutoff by the string. Cosmic strings could be searched
for by looking for these truncated images. If the image is not
resolved there will be a difference in magnitude and possibly
colour, if for example, just the arms of a spiral lie in the wedge.
Cosmology Page