Question on Gravitational lensing.

roosh

I know that GR is a very well "proven" theory, with oodles of evidence to support it. I was just wondering however - - how it has been shown that the effects attributed to Gravitational Lensing is the result of Gravity, and not simply a case of the diffraction of light according to Huygen's principle and/or Snell's law?

With regard to the gravitational lensig effect, of light bending around galaxies, could it not simply be attributable to light diffraction as

the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the superposition, or interference, of different parts of a wave that traveled to the observer by different paths

Diffraction - wiki

Or would Snell's Law not apply, where the temperature in the near-vacuum of space would be different the closer the proximity to such things as galaxies, planets, stars, etc. and therefore the density of the near-vacuum would change.
That is, does the density of the near-vacuum change the closer it is to planets, stars, etc. and therefore "invoke" Snell's Law?

Gurgle

Snells law requires a boundary between two materials, e.g air/glass air/water. This doesn't exist at the edges of a galaxy, the light travels through a vacuum all the way.

ZorbaTehZ

Snell's Law describes refraction which is a distinct phenomenon from diffraction - regardless, yes diffraction/refraction should occur around a planet, but the effects would be much too insignificant to account for what is observed (i.e. the lensing effect).

roosh

Gurgle wrote: »

Snells law requires a boundary between two materials, e.g air/glass air/water. This doesn't exist at the edges of a galaxy, the light travels through a vacuum all the way.

on Snell's law, does it not apply where the density of a substance changes e.g. light moving from cooler air through warmer air, and vice versa?

roosh

ZorbaTehZ wrote: »

Snell's Law describes refraction which is a distinct phenomenon from diffraction - regardless, yes diffraction/refraction should occur around a planet, but the effects would be much too insignificant to account for what is observed (i.e. the lensing effect).

cheers.

Gurgle

mangaroosh wrote: »

on Snell's law, does it not apply where the density of a substance changes e.g. light moving from cooler air through warmer air, and vice versa?

Yes.
You can look at this as a 'gradual' boundary or a series of gradiated boundaries. But you don't have this boundary condition between intergalactic vacuum and interplanatery vacuum within a galaxy.

roosh

Gurgle wrote: »

Yes.
You can look at this as a 'gradual' boundary or a series of gradiated boundaries. But you don't have this boundary condition between intergalactic vacuum and interplanatery vacuum within a galaxy.

with space being a near-vacuum, would the density of this near-vacuum not change with proximity to the sun, or planets no?

also, would light leaving a star, be subject, at all, to Snell's law, as it leaves the heat of the star and moves into the colder intergalactic near-vacuum. Would there be a change of density there, that would affect it?

jonathanmatt

mangaroosh wrote: »

with space being a near-vacuum, would the density of this near-vacuum not change with proximity to the sun, or planets no?

also, would light leaving a star, be subject, at all, to Snell's law, as it leaves the heat of the star and moves into the colder intergalactic near-vacuum. Would there be a change of density there, that would affect it?

I would say that the densities encountered in space would be negligible with respect to photons, and could be factored out

Normally the term density is used when referring to a mass made of particles which are interacting e.g. solids, liquids.

In space, densities would be so low that the particles are interacting (impacting, sharing vibrational energy etc) only extrememely rarely

Jonathan

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roosh

jonathanmatt wrote: »

I would say that the densities encountered in space would be negligible with respect to photons, and could be factored out

Normally the term density is used when referring to a mass made of particles which are interacting e.g. solids, liquids.

In space, densities would be so low that the particles are interacting (impacting, sharing vibrational energy etc) only extrememely rarely

Jonathan

__________________________

http://ie.linkedin.com/in/jonathanwmatthews/

cheers!