A Monster for Every Season: Summer 2
You can get A Monster for Every Season: Summer 2 now at Gumroad
Results 1 to 10 of 10
  1. - Top - End - #1
    Troll in the Playground
     
    Griffon

    Join Date
    Jun 2013
    Location
    Bristol, UK

    Default Does gravity bend differet frequecies of light differently?

    If it doesn't, is the bending it does refraction or something else?

    If it does, does that mean that the radius of a black hole's photon sphere varies depending on the frequency of the light?
    The end of what Son? The story? There is no end. There's just the point where the storytellers stop talking.

  2. - Top - End - #2
    Ogre in the Playground
     
    gomipile's Avatar

    Join Date
    Jul 2010

    Default Re: Does gravity bend differet frequecies of light differently?

    Gravitational lensing is achromatic.

    Within the context of the relevant model - General Relativity - it is not refraction. Within GR, it's an effect of the light passing through space that has a non-flat geometry.

    Let's look at the "marching soldiers" analogy of ray tracing used to provide intuition for refraction. With refraction, a higher index material is analogized as a region of rougher terrain, like sand or a muddy farm field. An analogy for gravitational lensing would have the same easy to walk on terrain everywhere, but with curvature of the surface causing the soldiers' paths to change.
    Quote Originally Posted by Harnel View Post
    where is the atropal? and does it have a listed LA?

  3. - Top - End - #3
    Bugbear in the Playground
    Join Date
    Jul 2017

    Default Re: Does gravity bend differet frequecies of light differently?

    A quick wikipedia look at "photon sphere" shows that there are two photon spheres for rotating black holes. One with the direction of rotation, the other against. If such a thing is mentioned for rotation but not for frequency of light, that's a strike against the idea.

    Radio astronomy, visible light astronomy and gravitational wave astronomy all point us at the same events in the same patch of sky. That's another strong sign that all straight paths through curved spacetime are the same, just like theory predicts.

    Incidentally, refraction requires two materials with different refractive indexes, and a discontinuous jump between them. (The surface of a body of water being the archetypal example.) I don't know if there's any theoretical basis for the idea of a discontinuous gravitational field strength, and I'm pretty sure if one existed it would allow for some pretty nasty violation of conservation of energy.

  4. - Top - End - #4
    Halfling in the Playground
     
    Lizardfolk

    Join Date
    Aug 2022
    Location
    the other Pacific coast
    Gender
    Male

    Default Re: Does gravity bend differet frequecies of light differently?

    gravity affects mass.
    afaik, all photons have the same mass, regardless of the energy (frequency) their wave transmits
    also, afaik, photons don't clump together to create a "centre of mass" like planets do, so I'd assume gravity affects all of them individually

  5. - Top - End - #5
    Troll in the Playground
     
    Imp

    Join Date
    Jul 2008
    Location
    Sweden
    Gender
    Male

    Default Re: Does gravity bend differet frequecies of light differently?

    https://www.mpg.de/19028990/0727-ext...vlens-155031-x

    This article contains a picture of gravitationally lensed galaxies, taken by the James Webb Telescope. No rainbow effect
    Black text is for sarcasm, also sincerity. You'll just have to read between the lines and infer from context like an animal

  6. - Top - End - #6
    Troll in the Playground
    Join Date
    Jan 2007

    Default Re: Does gravity bend differet frequecies of light differently?

    Quote Originally Posted by Anymage View Post
    A quick wikipedia look at "photon sphere" shows that there are two photon spheres for rotating black holes. One with the direction of rotation, the other against. If such a thing is mentioned for rotation but not for frequency of light, that's a strike against the idea.

    Radio astronomy, visible light astronomy and gravitational wave astronomy all point us at the same events in the same patch of sky. That's another strong sign that all straight paths through curved spacetime are the same, just like theory predicts.

    Incidentally, refraction requires two materials with different refractive indexes, and a discontinuous jump between them. (The surface of a body of water being the archetypal example.) I don't know if there's any theoretical basis for the idea of a discontinuous gravitational field strength, and I'm pretty sure if one existed it would allow for some pretty nasty violation of conservation of energy.
    There does not need to be a discontinuity. Gradually changing refractive index will also result in bending of light.
    In a war it doesn't matter who's right, only who's left.

  7. - Top - End - #7
    Troll in the Playground
     
    Griffon

    Join Date
    Jun 2013
    Location
    Bristol, UK

    Default Re: Does gravity bend differet frequecies of light differently?

    Quote Originally Posted by gomipile View Post
    Gravitational lensing is achromatic.
    Ah, okay, thanks. Either answer was going to be weird in some way.
    The end of what Son? The story? There is no end. There's just the point where the storytellers stop talking.

  8. - Top - End - #8
    Titan in the Playground
     
    Yora's Avatar

    Join Date
    Apr 2009
    Location
    Germany

    Default Re: Does gravity bend differet frequecies of light differently?

    Quote Originally Posted by MetroAlien View Post
    gravity affects mass.
    afaik, all photons have the same mass, regardless of the energy (frequency) their wave transmits
    also, afaik, photons don't clump together to create a "centre of mass" like planets do, so I'd assume gravity affects all of them individually
    Photons don't have any mass.

    What really happens with gravity is that it bends spacetime. A massless photon travelling in a straight line through curved spacetime moves in a curve. The same goes for every particle with mass as well.

    (And while you can be stationary in regards to another object in space, nothing can be stationary in time. So even when you don't move, gravity still pulls you to other masses because you are still moving through the time-part of curved space-time.)
    We are not standing on the shoulders of giants, but on very tall tower of other dwarves.

    Iridium Moons Retro-futuristic Space Opera
    Spriggan's Den Heroic Fantasy Roleplaying

  9. - Top - End - #9
    Titan in the Playground
    Join Date
    May 2007
    Location
    The Land of Cleves
    Gender
    Male

    Default Re: Does gravity bend differet frequecies of light differently?

    Quoth Anymage:

    Radio astronomy, visible light astronomy and gravitational wave astronomy all point us at the same events in the same patch of sky. That's another strong sign that all straight paths through curved spacetime are the same, just like theory predicts.
    It's true that gravitational waves are lensed in exactly the same way as light (of any frequency), but your point isn't a strong illustration of that, since most paths through space experience very little gravitational lensing. In fact, I don't think we've ever directly detected gravitational lensing of gravitational waves (though the theory, which is otherwise very well-tested, says that they should).

    Neutrinos aren't quite massless, but at typical energies they're found at, it's an excellent approximation to say that they are, and hence, to an excellent approximation, they'll also be lensed the same.
    Time travels in divers paces with divers persons.
    As You Like It, III:ii:328

    Chronos's Unalliterative Skillmonkey Guide
    Current Homebrew: 5th edition psionics

  10. - Top - End - #10
    Troll in the Playground
    Join Date
    Jan 2007

    Default Re: Does gravity bend differet frequecies of light differently?

    Quote Originally Posted by Chronos View Post
    It's true that gravitational waves are lensed in exactly the same way as light (of any frequency), but your point isn't a strong illustration of that, since most paths through space experience very little gravitational lensing. In fact, I don't think we've ever directly detected gravitational lensing of gravitational waves (though the theory, which is otherwise very well-tested, says that they should).

    Neutrinos aren't quite massless, but at typical energies they're found at, it's an excellent approximation to say that they are, and hence, to an excellent approximation, they'll also be lensed the same.
    Considering that we barely started detecting gravitational waves at all, it will take quite some time to observe lensing effects. I am not sure how good is the directionality of current detectors if that is a feature at all.
    In a war it doesn't matter who's right, only who's left.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •