Re: A 'Massless' question?
- From: Tom Roberts <tjroberts@xxxxxxxxxx>
- Date: Wed, 31 May 2006 15:03:08 GMT
varun wrote:
it is a well known fact that light bends due to the force of
gravity(e.g. at the time of solar eclipse...we are able to see the
stars which are behind the Sun,beside the Sun)
according to g=G.m1.m2/r^2 >for gravity to affect ...there should be
some mass but photons do not have any mass(i mean to say rest mass)
then why does gravity affect it.
GR is not Newtonian mechanics. In GR, gravity is modeled as the geometry of the spacetime manifold; light rays are constrained by their structure to follow null geodesics, and such geodesics are determined by the geometry of the manifold. This geometry is such that light rays are deflected by the sun as observed.
WHY DOES LIGHT BEND WHEN IT HAS NO MASS?
Because the geometry of spacetime compels it to "bend". The sun influences that geometry; this is the very same geometry that compels the planets to orbit the sun.
Note that a massive object approaching the sun with a large enough velocity would not orbit the sun, but would be deflected from a straight path; light is behaving similarly, and is the upper limit on the speed of such trajectories.
Tom Roberts
.
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