# Photon's frame of reference

Special relativity says that photons do not have a reference frame. When constructing a reference frame for an object in relativity you start by choosing a basis vector for the time coordinate which us the unit vector (whose 'length' of |1|) that is tangent to it's worldine. However for a photon (or an object travelling at c) all vectors tangent to it's worldlien are null vectors (whose 'length' is 0) so you cannot construct a reference frame.

This is not a flaw in theory it is a feature of the theory as in SR there is no reason that a photon should have a reference frame.
Yes ! Thank you jcsd. It irks me that people are seriously discussing the 'photons point of view'. Might as well talk about square circles.

Special relativity says that photons do not have a reference frame. When constructing a reference frame for an object in relativity you start by choosing a basis vector for the time coorindate which us the unit vector (whose 'length' of |1|) that is tangent to it's worldine. However for a photon (or an object travelling at c) all vectors tangent to it's worldlien are null vectors (whose 'length' is 0) so you cannot construct a reference frame.

This is not a flaw in theory it is a feature of the theory as in SR there is no reason that a photon shoudl have a reference frame.
I guess I could leave it at that and just accept that as what SR happens to say about photons. But I don't think that's what my mind is going to do.

When a photon gets emitted and absorbed, the energy constituting it goes into a special "mode", where it isn't subject to the same rules of space and time anymore. And the theory itself doesn't seem to reflect these "mode" changes. So it seems to me that SR doesn't really elegantly address this "mode", and I haven't heard anything so far that keeps me from being confident that future research is going to step into this open end. I don't think the work is done yet.

ColorSpace,
So it seems to me that SR doesn't really elegantly address this "mode", and I haven't heard anything so far that keeps me from being confident that future research is going to step into this open end. I don't think the work is done yet.
I think this problem is outside the scope of SR, which is a kinematical principle, not a theory of energy flow. What happens exactly when light is absorbed or emitted is not understood at present. It's not clear how we can ever probe this event.

I guess I could leave it at that and just accept that as what SR happens to say about photons. But I don't think that's what my mind is going to do.

When a photon gets emitted and absorbed, the energy constituting it goes into a special "mode", where it isn't subject to the same rules of space and time anymore. And the theory itself doesn't seem to reflect these "mode" changes. So it seems to me that SR doesn't really elegantly address this "mode", and I haven't heard anything so far that keeps me from being confident that future research is going to step into this open end. I don't think the work is done yet.
Does Roger Penrose' twistor space play a role in this discussion? Here is what Lee Smolin says about twistor space in his book The Trouble with Physics, pg 244: "More specifically, you can make a new space, consisting of all the light rays in spacetime. You can then translate all of physics into this space of light rays. The result is an incredibly beautiful construction, which Penrose calls twistor space." He goes on to write, "In surprisingly beautiful ways, many of the basic equations of physics could be rewritten in terms of twistor space. It really did seem as if you could see the light rays as the most fundamental thing, with space and time just an aspect of relations among them....The events of our spacetime turn out to be certain surfaces suspended in the twistor space. The geometry of our spacetime also emerges from structures in twistor space." He does go on to describe the problems with twistor space (which are associated with the fact that twistor space "is only understood in the absence of quantum theory"). We can't overlook such a blatant flaw, but isn't it interesting that Penrose seems to simply give the element of light a reference frame? I hadn't thought about this until I read the last comments of colorSpace. Though I may be going out on a limb to say that Penrose gives light a frame of reference. That's just how my little brain interpretes what I read about it.

Wallin:
but isn't it interesting that Penrose seems to simply give the element of light a reference frame?
No he does not. You're talking balderdash because you don't understand what is being said. Have you heard of general relativity ? One could equally argue the a GR space-time is nothing but all the trajectories ( geodesics) of light and matter. There is no implication that a frame of reference exists for light in this or in Penrose's ramblings.

Why don't you leave off ? You've been told by people a lot more qualified than me that the notion is meaningless in physical terms.

There was a time when people a lot more qualified than me said the earth was the only valid frame of reference. So the age of geocentricity was born. It started with Ptolemy (a most qualified and eminent scientist of the 2nd century A.D) and lasted for over 1500 years because everyone believed Ptolemy without question. It scares me when people are so sure of themselves and the status quo that they cannot afford to explore the places where conflictiing theories (GR and QM, for instance) might merge. Thank heaven Copernicus came along and dared to ask a question, to reach a little bit outside the box. Now I know I'm no Copernicus. In fact I would go so far as to say that I'm an idiot--a fool if you like. But I am wise enough to know that GR, SR and QM are missing something. Einstein, the author of GR knew that as well and I think he would object to your unquestioning, and wonder-crushing self assuredness. He would encourage me to keep asking questions and to keep up the search for the truth. I don't pretend to think I will be the one to find missing truth. But I'll certainly continue to have fun looking.

pervect
Staff Emeritus