dark matter

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Sam Wormley

Posted: Tue Mar 20, 2007 9:57 pm

Guest

gubbenimanen wrote:

Quote:

If photons had mass I would expect the image from a distant edge on
galaxy to bend towards a galaxy cluster center. This photo
http://apod.nasa.gov/apod/ap011007.html shows that the image bends
away from the cluster center.

Roger Persson

The light *does* bend inward (like a convex lens) by the gravitation
of the cluster. Photons are following the geodesic of the local space-
time curvature.

"Explanation: Gravity can bend light, allowing huge clusters of galaxies
to act as telescopes. Almost all of the bright objects in this released
Hubble Space Telescope image are galaxies in the cluster known as Abell
2218. The cluster is so massive and so compact that its gravity bends
and focuses the light from galaxies that lie behind it".

Geodesic
http://scienceworld.wolfram.com/physics/Geodesic.html
http://mathworld.wolfram.com/Geodesic.html

Gravitational Lensing
http://scienceworld.wolfram.com/physics/GravitationalLensing.html

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