Hi guys. Been lurking for a while. Collected all my nerve to ask three questions. I'm not very well educated in this field, so please don't hurt me.

First. Saw a documentary that claimed that CBR was "light that had travelled so far, for such a long time that it's wavelength had stretched into the radio-wave spectrum.If we were to travel in the direction of the CBR, it would recede, because we would from our new vantage point, observe light that would have done less so".

Is this true?

Second. I've been following the discussion on CREIL with much interest. Now i've read somewhere (on the www) that collisions between galaxies have been observed.

Does this point toward CREIL, since it's hard to imagine colliding galaxies if space itself expands?

Third. As i understand, the phenomenon of "Frame Dragging" has been detected. Is it feasable that in the interaction between mass, and time and space, a certain "viscosity" exists?

Thanks for your patience.

AE35

1. The CMB is thought to be the light from the surface of last scattering, i.e. it's light was emitted during the last moments of the primordial ion soup that would have filled the universe when the average temperature was too high for neutral atoms to exist. Photons simply ricocheted off of the ions, but the atoms were transparent to the photons at most wavelenghts.

The surface of last scattering is moving away from us at an astounding rate. In fact, it's moving away from everywhere at an astounding rate. It's not a place in space, but rather in time. It should be observable from anywhere in the universe, and it should be observed to be cooling from anywhere in the universe.

I'm not sure what that comment actually means, though. Moving toward the CMB (i.e. moving in any direction) would cause a relative blueshift to be observed in the CMB in the direction of travel, but a corresponding redshift would be observed in the opposite direction. But once you stopped moving, the surface of last scattering would not be any closer to you in any direction.


2. Observing galaxies in collision no more refutes the expansion of space than observing motor vehicles in collision. If two galaxies approach each other at a rate greater than that of the expansion of space, they'll collide.

3. Frame dragging is a general relativity thing. To the best of my memory, deals with spinning black holes or neutron stars where space gets sorta twisted. I'm sure Grapes'll come along and straighten that bit out.

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1. I too am puzzled about what it means to move towards the CMB, as it is coming from us in every direction. from billions of light years away and billions of years in the past. I guess it means relative to the CMB frame (i.e. the frame in which the CMB is isotropic).

2. No of course not colliding galaxies is due to the actual motion of the galaxies, recession is not.

3. Frame dragging is basicallythe fact taht a spinning graviatational source is different from one that is not spinning, all else being equal. In Netwnian gravity a spinning spherically symmetric graviational source is graviationally the same as a static spherically symmmetric source, in GR this is not the case.

Just to add that the Gravity Probe B is involved in the measurement of the frame dragging around our humble not-so-massive Earth--a very delicate measurement.

Per cubic foot there are something like 400 million million photons that comprise the CMB. It's not that it's far away, it's right here, in any given cubic foot of space. A percentage of the snow on a poorly tuned TV is the CMB.
The surface of last scattering, the point where the universe cooled enough for photons to travel un-impeded, is thought to have happened something like 100,000 to 300,000 years after the bang (ATB). It isn't the flash from the bang, more like an echo...

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>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Welcome AE35. By the way, HAL says you need to be replaced :wink: (I hope that's what your name refers to 8-[ )

When I saw something about three questions, all I could think of was:
1) What is your name?
2) What is your quest?
3) What is your favorite color?

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One Earth, One Sky - IYA 2009
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I thought it was, "What is the airspeed velocity of an unladen swallow?" 8)

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The CBR isn't "moving" away from us in the sense that its traveling through space. The entire universe has been cooling at a fairly constant rate over the last 13.7 billion years since the BB. Since we perceive the universe as being younger the further out we look because of relativistic delay, what is seen as the retraction of the CBR is actually the light of the Last Scattering dissipating and revealing more of the universe to us. The reality (and you'll hear a lot of screeching about relativistic frames after I post this) is the CBR fully dissipated from the universe billions of years ago and those points which we see as being obscured by the Scattering light are pretty much the same as the local space around us right now, but we're just now seeing it dissipate at the furthest point we can detect because the light of 13.7 billion years ago is just now reaching us. In a sense, the growth of the universe is as much a function of there being more of it visible with each passing moment, as it is of actual growth from spatial expansion.

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The reality is the CBR fully dissipated from the universe billions of years ago and those points which we see as being obscured by the Scattering light are pretty much the same as the local space around us right now, but we're just now seeing it dissipate at the furthest point we can detect because the light of 13.7 billion years ago is just now reaching us. In a sense, the growth of the universe is as much a function of there being more of it visible with each passing moment, as it is of actual growth from spatial expansion.

Yes DOODLE, this is exactly what i was getting at! I should have been clearer in my description of what i was thinking about, but you got my train of thought.

Question: Am i correct to understand from your reply that there is more mass behind the observable "horizon" as posed by the CBR?

If yes, how will this influence calculations on the shape of the universe (flat, open, closed).

Thanks.

AE35

2. Galaxies can collide and have even been photographed in the act. Our own galaxy will collide with the Andromeda galaxy in a few billion years. The collisions occur between galaxies that are gravitationally bound together in groups. These groups are swept along in the cosmic expansion.

3. Frame dragging has been observed cosmologically (around black holes) and locally (precise measurement of certain satellite orbital data). The Gravity Probe B satellite was originally proposed to be the first measurement of frame dragging, but in its 40 year history from concept till launch it got "scooped." Its measurements will be to a very high degree of precision, though.

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right next to the mashed potatoes

African or European?

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Some try to tell me, thoughts they cannot defend,... - Moody Blues.

The author feels that this technique of deliberately lying will actually make it easier for you to learn the ideas. - Donald Knuth

And you did it in a way that even i can understand.

Much obliged

AE35

No, the "horizon", as you've termed it, does not mark a place in space, but in time. It is not a shell that surrounds us in space, and so there is nothing "behind" it. It simply marks a point in history at which the universe became transparent. Before that, light couldn't travel any significant distance before hitting something and being pushed around. Think about throwing a tennis ball straight through a large group of people. A person on the other side of the crowd will never catch that ball. However, if the people were gone you'd be able to throw the ball straight at the receiver. The point at which those people disappeared would be your surface of last scattering (in time).

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"I'm making wheatloaf. It's like meatloaf, only with wheat"
"Isn't that just...bread?"

What? I dont know thaaaaaAAAAAHHHH!!