Understanding Relativity: The Sophomore's Question and Einstein's Answer

[outandbeyond2004]

CRB = Cosmic Radiation Background.

Nice graphic in this webpage showing the dipole:
http://csep10.phys.utk.edu/astr162/lect/cosmology/cbr.html

 

[OneEye]

outandbeyond2004: Fascinating!

So, then, given that the CBR is anisotropic, it might be taken to provide a sort of "grid" to the entire universe against which any other velocity or position might be measured - the dreaded K₀ and v₀?

Need to grind on that for a while!

 

[turin]

outandbeyond,
Do you know of any evidence of objects in the universe tending to slow down under the anisotropy of the impingent momentum of this radiation? Do you know of any direct physical effects attributed to bombardment by this radiation, specific to its wavelength? Do you have a link to an explanation (of can you give one yourself) of "galactic coordinates?"

 

[outandbeyond2004]

Well, a photon colliding with an electron, say, often would give the electron pause <smile>. Compton scattering and Thomson scattering. Rayleigh scattering is proportional to the 4th power of the frequency. Other kinds of scattering possible. Come to think of it, you want Thomson scattering; Compton scattering is for high-energy photons.

http://farside.ph.utexas.edu/teaching/jk1/lectures/node85.html

Let me know if this is too technical.

 

[OneEye]

outandbeyond,
Do you know of any evidence of objects in the universe tending to slow down under the anisotropy of the impingent momentum of this radiation? Do you know of any direct physical effects attributed to bombardment by this radiation, specific to its wavelength? Do you have a link to an explanation (of can you give one yourself) of "galactic coordinates?"

Of course, the fact that we can measure the CBR indicates a rather ordinary interaction with, say, earthbound observers.

The fact that we can map the CBR implicates it as a reference frame.

 

[outandbeyond2004]

Turin wrote this: "slow down under the anisotropy of the impingent momentum of this radiation."

Not sure what that means. One could say that most collisions are asymmetric, so might as well as ask "slow down after colliding with CRB photons," I think.

As for galactic coordinates, they are merely part of a conventional system astronomers use to locate points in spacetime in a way that is convenient for some problems. Nothing more fancy than the longitude and latitude system that we use on Earth. The galactic coordinates really don't have anything to do with the CRB.

It occurs to me that it is not really easy to use the CRB as a rf. It would be preferable to use the pulsars to set up a rf. Perhaps someday a future Turin will ask a future oney about "pulsar coordinates."

 

[turin]

outandbeyond,
I had never heard of this anisotropy until you posted it, so I am having to make quite a mental extension. I am not trying to discount the existence of the anisotropy; on the contrary, I would be quite shocked to find that that there is none. But I have never seriously considered any of its effects, being overwhelmed with the chore of learning different physical disciplines. I have somewhat of an understanding in physics, but I admit that I don't know much about cosmology or this CRB of which you speak. The intent of my questions was towards the empirical effects, not indirect theoretical predictions.

1) Assuming that the distribution shown in the ovular picture in some way indicate a spatial anisotropy in the frequency of the CBR (which seems to be the point of your post?), then one side of a physical object would be suscepted to a higher impulse than the other, and so, this would cause the object to accelerate towards the "redder" direction of this radiation until it finally (assymptotically) achieved a state is isotropy. Any anisotropy seems like it should induce an embalance in force. Of course, this is nowhere near conclusive, since the absolute intensity could vary independently of the frequency, not to mention that the object may in fact have a nontrivial response to the spectrum. I was wondering if anyone (NASA, USA, Stanford, ...) has experimentally targetted this question and observed, let's say, a tendency for, let's say, very light-weight objects to accelerate in the lab frame towards the "redder" CBR and away from the "bluer" CBR.

2) This question is to address the sub-issue brought up in my mind by the previous question. Perhaps aggregate objects are more proned to respond to the radiation slightly on the red side of 3 K than they would be to radiation slightly on the blue side. Of course, crustals with the appropriate lattice constant would meet this condition, but they are not perfectly isotropic, I'm thinking specifically about amorphous/vitreous isotropic compounds.

3) I didn't suspect galactic coordinates to be anything terribly complicated, or anything but analogous to lat. and lon. But the analogy does not explain them satisfactorially to me. Are they exactly the angular coordinates on the celestial sphere? How do these coordinates map the oval on the site that you have linked? The site mentions that the picture is "in galactic coordinates," yet I see no reference to coordinate surfaces or labeled points on the picture. And furthermore, if I have no reference, then this pictures serves as nothing more than a mathematical abstraction. I do not deny the physical significance of the picture, but I feel just a little gypped that neither the site, nor yourself, have given me a means to physically appreciate it. I suppose I could do my own search for the definition/physical significance, but I figured that, since you brought it up, you could do me the courtesy.

 

[OneEye]

It occurs to me that it is not really easy to use the CRB as a rf. It would be preferable to use the pulsars to set up a rf.

Well, I wasn't really trying to invent a technology - only to observe that the CBR could be used as a universal reference frame.

But, now that you mention it, perhaps something along the lines of an inertial navigation system could be constructed using the CBR as a reference system.

Not that we would really find this more useful - or accurate - than, say, GPS.

But anyway...