Where on that page does the writer make that distinction? He only uses the word infinite once and in a different context.
emphasis added.
That still doesn’t lead to any difference between an infinite universe and a finite one that’s much larger than our Hubble radius. And the evidence seems to suggest that the Universe is much larger than the Hubble radius, anyway.
I suppose, but for all intents and purposes . . .
We can see quite a lot of objects outside of the Hubble radius (as the Hubble radius is only about 1/3 of the radius of the observable Universe). It would be pretty clear if the Universe was smaller than the Hubble radius as we would see multiple images of the same objects
OK, the full quote is “if we were sampling a tiny piece of a sinusoidal fluctuation with a wavelength many times the size of our current Hubble radius.” Is that better?
Many times finite is finite. Any times finite is finite. I can’t understand how you are getting to infinite, a difference in kind not size.
Please refer to post 24
What the hell does that even mean? Large and infinite are entirely separate concepts. You cannot have something that is for “all intents and purposes” infinite. That’s gibberish.
OK, it’s gibberish. Just like the infinitesimal calculus is gibberish.
The light from when the Universe went clear is at the edge of the Universe. It was at the edge over 13 billion years ago when the lights came on and it’s at the edge now. All the protons and electrons that combined to let the light run free was also at the edge of the Universe. All that primordial matter is still at the edge of the Universe. And just a tiny bit of it is us. Some of those charged partials that became atoms on that fateful day when the Universe was only a few hundred thousand years old. Went on to eventually become us. The light from when the lights came on was with us then and is with us today. It was with us fifty years ago when Bell Labs first isolated it. And it is with us right here at the edge of the Universe today. Just as it has all along, right here, right now, on the edge.
To add some graphics to what’s been said above…
Here’s what the CMB temperature map looks like raw: no subtraction, no zero-suppression.
It’s extremely uniform at around 2.725 Kelvin.
If you zoom in on the color scale such that the entire color range reaches only +/-0.15% from this average value, you get this image: centered on average value.
The overall dipole effect (red in upper right, blue in lower left) from the Earth’s velocity is the dominant feature.
Subtracting the dipole gets you this image: dipole-subtracted.
The fluctuations of interest are visible in most of the image. The band across the middle comes from microwave sources in our galaxy.
Finally, subtracting out the foreground sources gets you the image you included in the OP.
How do they do this and still get clean data? Looking at the final product there’s no noticeable lack of resolution or anything in the area of that band.
The foreground sources aren’t 2.7-K blackbody emitters but rather have their own characteristic spectral shapes. Templates for the handful of possible spectral signatures are fitted out for each pixel. You can use externally determined templates for the foreground sources’ spectra or you can use statistical methods to build up spectral templates from the CMB map itself, and you get consistent results either way (which is nice).
Thanks. That makes sense. ETA: but wouldn’t each pixel have multiple stars or other sources in it? Wouldn’t the spectrum in each pixel then be a sum of multiple spectrum shapes? It seems you’d have to subtract out every visible star. ETA2: I guess that data would be available for a lot of stars, but for all of them, and the galaxy itself?
Also, can you explain the fourth figure here, “with hot and cold anomalies highlighted”.
I know the small circle is showing the CMB dark spot, but the white line doesn’t make sense. It doesn’t form a continuous line across the edges of the image, like I’d expect. It looks like they’re trying to emphasize an asymmetry on either side of the line, but it looks like it was just photoshopped.
Sort of. The relevant sources are diffuse and somewhat simple systems(*), but, yes, the fit must allow for the unknown amount of each type of source and for any potential differences in them from place to place.
(*) Synchrotron radiation from electrons, bremsstrahlung radiation from electron-ion collisions, and thermal emissions from dust.
It’s another circle, just one that hits the edge of the image and loops back around to the other side. (That is, it is sliced open by the choice of sphere-to-plane projection.) It is dividing the image into two hemispheres, with the bottom half being anomalously warmer than the top by a bit. The dividing line happens to be very close to the ecliptic plane, which in the fullness of time will either prove to be interesting or a red herring.
Stars aren’t significant contributors directly?
Either the white line is incorrectly drawn, or the way the edges of the CMB image join are bizarre. Looking at this resolution comparison, the left end of the white line terminates in the South Pacific, and the right edge terminates in the North Pacific. There’s no way they join.
Not in the relevant frequency bands, no.
Ah, yes. I agree. I couldn’t find that image directly in any scientific source, only from ESA public relations documents, which isn’t a good sign.
It’s only been barely a few days. We’ll be coming back to this discussion in a couple of months.
I was looking at the Overview PDF, and in it they say (page 23):
If I’m reading that right, 3% of that image (an area equivalent to a 3.4 degree wide band in the galactic plane) is [del]fiction[/del] an artist’s depiction. I guess there’s just too much contamination/obscurred data there.
(I’m not complaining, since it certainly looks better than a blank band would look.)