All Questions
Tagged with optics general-relativity
28
questions
43
votes
5
answers
15k
views
How does gravitational lensing account for Einstein's Cross?
Einstein's Cross has been attributed to gravitational lensing. However, most examples of gravitational lensing are crescents known as Einstein's rings. I can easily understand the rings and crescents, ...
- 6,044
11
votes
3
answers
2k
views
Liouville's theorem and gravitationally deflected lightpaths
It is customary in gravitational lensing problems, to project both the background source and the deflecting mass (e.g. a background quasar, and a foreground galaxy acting as a lens) in a plane.
Then, ...
- 3,755
9
votes
1
answer
311
views
does the beam of a laser have 'throw'?
I was thinking about Einstein's train and platform experiment and was wondering if a beam of light experiences throw? Let me explain, if I take a water hose and point it straight out and then swing ...
- 93
8
votes
2
answers
336
views
Why a gravitational lense makes multiple distinct pictures of a distant object rather than making a symmetric ring?
I cannot imagine how a group of galaxies may produce pictures of a distant object on a ring-like region that is not symmetric. Why there are empty parts of that ring where there are no pictures of the ...
- 1,815
8
votes
1
answer
344
views
Book on optics in curved space-time
As evidenced from my earlier questions on vision and curved space, I am struggling a little bit with visual perception in curved space-time.
I would like a book recommendation on optics and vision in ...
7
votes
2
answers
2k
views
How do we know that bending of light around stars is due to bending of space-time and not diffraction?
One question that popped up during the studies of special and general relativity (which I am forced to take unfortunately) is the following:
How do we know that this is due to the bending of space-...
- 649
4
votes
2
answers
421
views
Seeing one's back on the event horizon
If we would hypothetically be exactly on the event horizon, we should see our own back, because of the circular motion of photons on the event horizon, right?
But what would be the image size, or $-$ ...
- 991
3
votes
2
answers
77
views
When gravity bends light, does the light still propagate orthogonally to its $\vec E$ and $\vec B$ fields?
An ordinary photon travels perpendicularly to the direction of its oscillating E & B vector fields (i.e. $\vec{v} \propto \vec{E} \times \vec{B}$). Let's say $\vec{E}$ is oscillating "in-out" of ...
- 945
3
votes
2
answers
2k
views
Why do we know that light must follow a geodesic?
THE CONTEXT:
Some context to my question: Einstein once posed the thought experiment of a man falling inside a closed box. Just before the box was dropped, a photon was fired horizontally moving from ...
- 1,087
3
votes
2
answers
312
views
Gravitational distortion of an object's diameter, at a distance,
Does the curvature of space-time cause objects to look smaller than they really are? What is the relationship between the optical distortion and the mass of the objects?
- 31
3
votes
1
answer
212
views
Does the index of refraction of the sun's corona and solar wind contribute to the bending of light
It's not hard to imagine that the sun's corona and surrounding solar winds have an optical density that can affect the index of refraction near the surface of the sun and bend light in these regions. ...
- 2,270
3
votes
0
answers
80
views
Critical angle in General Relativity
Analogies between optical propagation in different refractive media and the effect of gravity in light geodesics are well established. But in optics one can have total internal reflection if certain ...
- 14.5k
2
votes
2
answers
563
views
Does gravitational lensing violate Fermat's Principle that light must travel in straight lines?
Does bending of light due to warping of space violate Fermat's Principle or is it that in the principle light goes in a straight line with respect to space (taking space as the reference) and in ...
- 3,905
2
votes
1
answer
282
views
Do gravitational lenses act as prisms?
Light creates gravity, and the greater the light's frequency, the greater this gravitational effect is. It stands to reason then that light of different colors would react slightly differently to ...
- 804
2
votes
2
answers
75
views
If a weak light source is attached to a string, and someone swing this light source in circle. It seems that this light source is brighter. Yes or no
It may be truly a question of life and death.
You know those glow sticks.
As a sailor it is a good idea to carry one on our lifevest.
Falling into the sea, those glow stick make a light source that ...
