View Full Version : Gravitational Lensing

2008-Aug-30, 02:14 AM
Does gravitational lensing effect photons or light as a wave?

Second question. Does gravity effect all electomagnetic energy equally?

2008-Aug-30, 02:35 AM
Does gravitational lensing effect photons or light as a wave?
I'm... not quite sure what you are asking with this question.

Light will exhibit wave-like behavior enough to consider it a 'wave.' So the answer to "Would Light still behave as a wave in those circumstances?" should be "yes."

Second question. Does gravity effect all electomagnetic energy equally?

The warping of space caused by gravity will effect all that moves across that curved space.
Electromagnetic energy will behave the same, essentially, so I would still answer this with "yes."

Ken G
2008-Aug-30, 03:06 AM
Does gravitational lensing effect photons or light as a wave?
It affects light, period. That means it has to affect any successful theory of light also. The theories of photons, and the theory of light as a wave, and the connections between those theories, are all successful in the context of gravitational lensing.

Second question. Does gravity effect all electomagnetic energy equally?Observationally, it does appear to, and all the successful theories of light that you have heard about reflect that property faithfully in the context of the theory of general relativity. There are more complicated theories that might predict differences, for all I know, but so far there is no observational data to favor such an approach, so the simplest approach, which indeed holds that all frequencies are affected the same, is currently viewed as the best.

2008-Aug-30, 03:14 AM
Thanks alot. Great forum.

2008-Aug-31, 12:51 PM
Are gravitational waves affected by gravitational lensing?.
It may be a good idea to search for gravitational waves at the orbital frequency of an
optical binary when there is a star almost between us and the binary.Any magnification of the G wave would be a help.

2009-Feb-18, 03:15 PM
Does anyone here know how we detect GL (gravitational Lensing)? Is it done by eye? People looking at pictures? Are computers involved? Is it both?

Like the bullet cluster. How is the amount of GL determined? Thanks.

2009-Feb-18, 03:33 PM
Albert Einstein predicted that massive objects, such as stars, could bend light rays passing nearby. This prediction was verified by the observation of such bending of starlight near the Sun in 1919 during a total eclipse

In the 30's, Einstein said that, if a brightly-emitting object were exactly behind a massive body capable of making a gravitational lens, the result would be an image of a ring around the massive lensing object. H
Optical observers discovered the first gravitational lens. Strong gravitational lensing can be seen visually, weak gravitational lensing needs computers.

2009-Feb-18, 03:54 PM
So it is both, visual and computer? Anyone know where to find literature about this?

Jeff Root
2009-Feb-18, 04:24 PM

I only read about the Bullet cluster briefly when it was in the news, so I
may not understand correctly, but I believe the phenomenon there is quite
different from gravitational lensing. With probably hundreds of examples
of gravitational lensing to choose from, you picked an example of something
that is not gravitational lensing.

As far as I know, instances of lensing are recognized by eye, along with
spectral data to determine the similarity of the various light splotches to
help determine if they are likely to be multiple images of one object.

Computer modelling must be important to determine what we should
expect to see in cases of gravitational lensing, as well as determining
what we are actually looking at. That is, we see an arc of light of a
certain size at a certain location in a image, and computer modelling
can show how massive the lenser must be to produce such an arc.

-- Jeff, in Minneapolis

2009-Feb-18, 07:17 PM
The Bullet cluster was studied in three ways:

a) look at the location of its own galaxies
in visible light

b) look at the location of very hot gas
in X-rays

c) look at the location of BACKGROUND galaxies
in visible light

The positions and shapes of the BACKGROUND galaxies
are distorted, due to gravitational lensing by the Bullet
Cluster's mass as the light from the background galaxies
passes through the Bullet Cluster on its way to us.

In a more general sense, gravitational lensing is most
commonly observed using optical telescopes. We look
at one set of galaxies (background galaxies) through
a set of foreground galaxies. The shapes of the background
galaxies are distorted into long, thin arcs. The distortion
of many, many different background galaxies allows us
to determine to some degree the mass distribution of
the foreground cluster of galaxies.