It’s not precisely an artist’s depiction, since it’s derived by calculations from surrounding regions. It’s not like they had some guy with a paintbrush fill in the missing spots by hand.
Yeah, SMICA isn’t one of the subtract-known-sources methods but instead is one of the figure-out-the-sources-from-the-map methods. In some regions, it’s too underconstrained to do the independent component analysis. The in-fill is, of course, not useful for science, but it’s also not as random as it might sound, as it is performed in frequency space and is heavily constrained by the CMB power spectrum measured elsewhere on the sky. It’s more of an “interpolation-with-benefits”.
I’m not sure what you mean with regard to the white line in the ESA press release image.
I mean the anomalies it represents aren’t nearly as insignificant as you’ve portrayed them. But I’m happy to wait to see what the research community does or doesn’t have to say about it.
Ah, you’re talking about a different thread I believe. I haven’t said anything about the significance of the anomalies in this thread, which has a narrower topic.
Please everyone, let’s move along to the appropriate thread.
OK, now I’m going to have to find a way to use this phrase myself.
Reminds me of how Marie Tharp drew the first detailed and accurate maps of the ocean floors, around 1956, by interpolating-with-benefits from ship soundings. (Thus the rift valleys of mid-ocean spreading centers were discovered, and a big part of then-controversial plate tectonics was confirmed.)
I was linking to the other thread so that folks could see the discussion to which you were referring. Your post might be unclear without that context.
Resurrecting this zombie because I just thought of another related question.
Given that the CBR image is of radiation from when the universe became transparent, will this same image exist at every point at every point in the far far distant future?
No. The image will be different at every location, and at every time. All of the images at the same time will look qualitatively the same, but the details will be different. Images at different times would have different frequencies, with later ones more redshifted.
My favourite factoid about the Cosmic Microwave Background is that it was emitted from a sphere only 40-something million light years in radius. The universe was a* lot *denser then.
I know this is old, but since it is quoted above, I think it could be stated more clearly. The CMBR was emitted from every point in space, including where I’m sitting now. But it was all emitted in the far distant past. If an alien is now standing at the point of origin of the CMBR photons that are now reaching my eyes, CMBR photons that were emitted from where I’m standing are likewise just now reaching that alien.
The “sphere” that everyone is talking about is not in any sense the only place that CMBR was emitted from. It was emitted everywhere. The sphere just corresponds to the points of origin of all the CMBR that we can see standing at our particular place in the universe at this particular time, i.e. the (probable) limit of our practically visible universe. As Chronos says, an alien standing somewhere else in the universe will see a different sphere.
I’m wondering how quickly the anisotropy of the visible sphere changes for a given location as time passes. As time passes, you are always seeing the same point in time, so you are seeing a different (more distant) place. I guess to some extent the answer is “it depends how sensitive your instruments are”. But the scale of the fluctuations we can detect now is huge.
EDIT, poorly word sentence, should read:
If an alien is now standing at the point of origin of some of the CMBR photons that are now reaching my eyes, some of the CMBR photons that were emitted in the distant past from where I’m standing are likewise just now reaching that alien.
This has already been addressed, but there’s a common misconception that wasn’t explicitly identified. It’s seen here in the phrase “outer edges of the … universe-sphere.”
Spheres don’t have edges. Balls have edges, or rather boundaries. The boundary of a 3D ball is a 2D sphere. The universe is considered to be a 3D sphere.
I’ll let one of the mathematicians explain the distinction between a 3D ball and a 3D sphere. I considered linking to the Wikipedia article “3-sphere” but was revulsed by it. It defines 3-sphere strictly in terms of 4D Euclidean space. :smack: That’s one way to describe it or imagine it, but no 4th spatial dimension is necessary to a 3-sphere.
I think it is misleading to describe “the universe” (without qualification) as a sphere at all, because it maintains the persistent misconception that the universe is something expanding in pre-existing space with an “edge”, and that the Big Bang happened at some point in that pre-existing space. All of that is wrong.
It must be constantly emphasized that when we talk about the diameter of the universe, or about any kind of “sphere”, we are simply talking about the boundary of the visible universe. This “sphere” is not anything concrete, it is not really a physical edge or boundary, it’s simply the furthest we can see in any direction. We cannot (by definition) know anything about what’s beyond the boundary of the visible universe, but unless you believe that the universe was built specifically for humans, the reasonable assumption is that the universe continues just the same beyond this sphere that demarcates the furthest we are able to see from our position. An alien on a different planet has a different sphere, centered on her position.
The Big Bang happened everywhere. If you don’t grasp that, you are misunderstanding how space works. The only thing that was a point, and that was subsequently demarcated by an expanding sphere, was the particular part of the Big Bang and the subsequent evolving universe that is centered on our position - the visible universe.
I can’t decide whether you’re agreeing with my post, or exemplifying the misidentification!
A 3-sphere is quite distinct from the ordinary sphere (2-sphere) mentioned frequently in-thread. It’s a technical term which IIUC does describe the presumed topology of the universe.
ETA: I think the best analogy is to think of the 1-dimensional model, the ants on an infinitely stretchable elastic band. The ants stand stationary on the band (or may wander around a bit locally), but the band itself stretches, moving them farther apart in their 1-d space.
Now, if you imagine that the “visible universe” for each ant is (say) 1 meter in either direction at the current amount of stretching. The limits of the what a given ant can see are two points 1 meter away either side, that’s his visible universe. But there’s nothing special about those points, except to the ant at the center. Each ant along the band has his own different visible universe. In a 3-d universe, that visible limit for an observer is a sphere, rather than the two points in the 1-d analogy. That’s the only sense in which there is a sphere.
Now, as the elastic band stretches, the ants move apart, and the points that represent the limit of their visible universe stretch apart to, i.e. their visible universe expands.
Imagine that the elastic band is infinitely long, since the universe may be infinite. This is a bit weird, and we don’t have good intuition about what it really means, but I think it helps to avoid misconceptions about what the expansion of space (and the Big Bang) means. As expansion occurs, stationary points (ants) on the elastic band get further apart. The elastic band is stretching, but remember it was always infinite. So this expansion doesn’t mean that the ends are moving further apart, because it doesn’t have ends. So it’s not stretching “into” something preexisting, it’s just stretching.
Similarly, if you go backwards in time, the elastic band contracts, and everything gets closer together. But it’s still infinitely long, it’s always infinitely long, however much it stretches or contracts. If you keep going back in time toward the Big Bang, everything is getting closer and closer together - but it’s still infinitely long - and every point along the band is behaving the same way, it looks the same to any ant. Now, the “singularity” is the limit of this – when this infinitely long band contracts so much that the distance between any two point is zero. So now we have an infinitely long rubber band where the distance between any two points is zero, and that’s what it means to say that the singularity is simply undefined, it’s infinity-times-zero.
But all of this maybe gives a better feel to understanding that the Big Bang happened everywhere, i.e. any point on the infinite elastic band looks the same as this shrinking is happening.
I think the distinction between “the universe” and “the visible universe” is the more basic distinction that is glossed over and leads to fundamental misconceptions. The visible universe is a regular sphere.
ETA: Sorry, I can see that was a bit misleading on re-reading it. I wasn’t so much replying to your comment about the 3-sphere, more giving an alternate response to what Sengoid had asked about in the comment that you quoted.
I think you mean the visible universe is a 3-D ball. The distinction between balls and spheres was the essential Nitpick I was pursuing.