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The gravitational lens effect is applied to a supernova lying far behind and close to the line of sight through a distant galaxy. The light from the supernova may follow two different paths to the observer, and the difference Δ t in the time of light travel for these two paths can amount to a couple of months or more, and may be measurable. It is shown that Hubble's parameter and the mass of the galaxy can be expressed by Δ t , the red-shifts of the supernova and the galaxy, the luminosities of the supernova “images” and the angle between them. The possibility of observing the phenomenon is discussed.
S. Refsdal (Tue,) studied this question.