Measuring Distances in Astronomy with Geometry

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Beam of fast-moving Uranium atoms

Suitably placed Geiger counter

Nuclear fission of Uranium atoms

Slide 19

General Theory of Relativity (GTR)

Principle of Equivalence

All objects experience the same motion in a given

gravitational field, irrespective of their mass

[Galileo's experiment at the leaning tower of Pisa]

Gravitational field <===> Accelerated reference frame

Gravity can be thought of as a distortion of space-time

Slide 20

Slide 21

Observable Consequences of GTR

Perihelion precession of Mercury

Light bending:

Solar eclipse experiment

Slide 22

Gravitational lensing:

Multiple images,

image distortion

Gravitational Redshift

[Extreme case: light is

“trapped” in a black hole]

Slide 23

General relativistic effects are important in a STRONG GRAVITATIONAL FIELD