# The Naked Scientists Forum

### Author Topic: Does gravity influence all frequencies of light equally?  (Read 2615 times)

#### chiralSPO

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##### Does gravity influence all frequencies of light equally?
« on: 19/04/2014 04:08:13 »
Is there any sort of aberration caused by gravitational bending of light at different frequencies by different amounts?

As photons are all massless and all traveling at the same speed I could imagine that they are all equally affected. However they have different momenta, depending on the frequency (p=hν/c). Does this mean they have different "inertia" as well?

What is observed? What is the reasoning?

Thank you.

#### RD

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##### Re: Does gravity influence all frequencies of light equally?
« Reply #1 on: 19/04/2014 05:50:49 »
Is there any sort of aberration caused by gravitational bending of light at different frequencies by different amounts? ... What is observed? ...

No chromatic-aberration with a gravitational lens ...

https://en.wikipedia.org/wiki/Einstein_ring

https://en.wikipedia.org/wiki/Gravitational_lens
« Last Edit: 19/04/2014 05:54:31 by RD »

#### yor_on

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##### Re: Does gravity influence all frequencies of light equally?
« Reply #2 on: 19/04/2014 15:43:08 »
That one seems a minefield Chiral. And a very clever question :) You would probably have to restrict yourself to monochromatic light though, I guess? Propagating in a vacuum. Using sunlight for it you need to split it into frequencies first. And doing so you will notice that there is a point from where they all co-exist, being that optical prism you might use to split that light.

If we take it one step further, then the fact that you can split polychromatic sunlight light into other frequencies actually argues against it, or else you need a theory of how white light, from far suns, act? As if it being a 'composite' of frequencies held together, giving you a 'instantly available point of focus in a prism, allowing you a immediate 'split' of frequencies, or?

All in all, one of the best questions I've seen actually.
« Last Edit: 19/04/2014 16:07:52 by yor_on »

#### yor_on

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##### Re: Does gravity influence all frequencies of light equally?
« Reply #3 on: 19/04/2014 15:56:49 »
You could possibly think of it as a result of interaction. If we ignore how 'it comes to be (exist), propagating or not' in your experiment, then it's the interaction that defines your observation. (And what a sweet view that is to me:)
=

For a photons point of view, if it now had one, this shouldn't present a problem. I would expect photons of different energies/momentum to find different geodesics in a vacuum (depending on gravity), propagating. A photon is the smallest 'packet' of energy I know of, if I on the other hand want to argue that photons are some sort of 'wave packets' containing different frequencies I suspect I will get a headache.
==

What your question adds up to, for me, is the implausibility of lights 'propagation'. Light is not a object in the usual term, and there is no way to study it propagating. You can measure it, using matter, and we find it to have sources and sinks. But? You can only annihilate it. When that flashlight is on, and you see it on, that's exactly what you're doing. Annihilating light. No way I know of observing light getting 'created'. The closest we get to it, is a recoil in the matter involved in 'creating' light.

==

And there is one added thing to it, conservation of energy. When you observe a photon you transform it, into electrochemical energy, and ultimately heat, as I see it described. And we use old definitions( https://en.wikipedia.org/wiki/Conservation_of_mass) from we, as a logical chain of arguments and mathematics, can reach Noether's definitions of conversation laws, and then further still. Now, I don't know what energy is, and I'm pretty sure nobody else knows it either. So when we define how something transform, and how nothing is lost, I'm still left wondering how we know? Because if energy just is what amounts to a exchange, then you can reach any possibility, assuming something more than what we measure.

And I find it extremely irritating to assume that 'energy', on one hand, is of one same 'property'. On the other, able to be split into 'useful energy', and 'non useful', without nothing ever getting lost in the transformation from one to the other. Something is lost to me, although I don't know what it is.
« Last Edit: 19/04/2014 16:45:58 by yor_on »

#### chiralSPO

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##### Re: Does gravity influence all frequencies of light equally?
« Reply #4 on: 19/04/2014 20:43:54 »

Is this to say that the momentum of a photon is only relevant during interaction of that photon with matter? (ie when the photon is created or destroyed)

What about a photon orbiting a black hole? Does it have angular momentum? And is that related to the frequency of the light?

#### yor_on

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##### Re: Does gravity influence all frequencies of light equally?
« Reply #5 on: 20/04/2014 13:49:24 »
Does it propagate? Is there a 'commonly same for all universe'? What importance will you lay into those questions Chiral? Einsteins descriptions is for the universe we all find us to exist in, also why he says the moon still will be there, even when he's not looking. But he also liked to think of it as 'fields', possibly even as a singular 'field'? And modern QM, and the Higgs, also want to look at it as a field. So is it a field? A field with observer dependencies become a sort of 'ideal container model', no matter how you define its limits. A field without observer dependencies definitely falls inside my thoughts of what makes up a 'container model'.

It doesn't matter how I treat 'dimensions', as long as I also presume this 'commonly same model' of existence, to become my ultimate realization of a universe. And we do so, every time we look up on the stars, and agree on them.

From locality you can take a opposite stand. There such things as one 'frame of reference' matters. And the scale matters. From there Einsteins clock and ruler becomes macroscopic definitions we use to measure on microscopic events. We're macroscopic beings, from simplicity, which you then can read as the particles making us up for example, puzzled together into macroscopic definitions, each one of us consisting of a innumerable amount of local frames of reference. Those I then would say create a new complex pattern giving each one of us a ideal clock and ruler, defining a universe. The repeatable experiments we define use this local clock and ruler, and those experiments prove our local definitions to be equivalent, that's a primary logic we use. And from that you will find (actually *must find* assuming logic to be what defines a universe) locally definable constants, existing locally for us all, as 'c', that I then define equivalent to ones local arrow. Those are the stepping stones for the 'commonly agreeable on universe' we jump to from that.

It's more or less philosophy this one, but it is important to decide how you want to treat this universe. A lot of our preconceptions stem from our growing up. There gravity will be a force, the universe exist, with you and me are a integral part of it. But you can question it, motion, and propagation, depending on from where you look at it. Doesn't mean that one description is more true. If you think of us as something treating, and connecting, synthesizing information into logics, then we all do the best we can from where we are. And so we find a container model.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relmom.html
(if you look at this link, take a look at the 'Planck relationship' too.)
« Last Edit: 20/04/2014 15:04:13 by yor_on »

#### The Naked Scientists Forum

##### Re: Does gravity influence all frequencies of light equally?
« Reply #5 on: 20/04/2014 13:49:24 »