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Gravitational lensing

  1. May 13, 2007 #1
    I read that when a galaxy comes in the path of light coming from a quasar, its path bends slightly resulting in the formation of a giant luminous arc (called einstein ring). The phenomenon is called gravitational lensing. Can someone tell me something more about gravitational lensing ? Please use as simple language as possible.
  2. jcsd
  3. May 13, 2007 #2
    What do you want to know?

    How 'bout an analogy? You've seen normal glass lenses, that are thicker in the middle ("convex"), and make the object behind them appear bigger. This focusing or light waves occurs because the light travels slower through glass than air. It turns out that light also travels slower near large masses (actually, because time itself flows slower), compared to far away in emptier space, so the focussing of light gravitationally (say, by a galaxy) works very similarly to a glass lens. The first observation of gravitational lensing was during a solar eclipse, since by blocking out the sunlight you can observe that whatever constellation is almost-behind the sun looks distorted (stretched).
  4. May 19, 2007 #3
  5. May 20, 2007 #4
    You might also want to read about gravitational microlensing, which is currently being explored as a method of extrasolar planet detection.
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