Wikipedia:Reference desk/Archives/Science/2015 July 4

Science desk
< July 3	<< Jun | July | Aug >>	July 5 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 4

Is the CMB a baby picture of only the observable universe?

Is the Cosmic Microwave Background a "baby picture" of the entire universe or just the observable universe? If the observable universe is all we're able to see then isn't the CMB picture incomplete? Or can we extrapolate from the CMB how the entire universe appears beyond just what is observable? 184.65.230.52 (talk) 01:59, 4 July 2015 (UTC)

The observable universe. Dragons flight (talk) 02:17, 4 July 2015 (UTC)

The CMB light that's just now reaching us has all traveled about the same distance, so its points of origin form a sphere centered on us. That sphere is the boundary of the observable universe. CMB maps like the one to the right are Mollweide projections of the sphere. So not only does the map not directly tell us about the universe outside the boundary, it also doesn't directly tell us about the universe inside the boundary. It does contain information about the interior because the light interacted with matter in the interior on its way to us, and it contains information about the exterior because the state of the plasma that emitted the light (about 380,000 years ABB) depended on the earlier state of the universe in all directions, including the directions that are farther from us than the source of the light. -- BenRG (talk) 03:25, 4 July 2015 (UTC)

The source of the microwave background is in the observable universe because we're observing it. That said, the concept of the observable universe is full of tricks. The distance back to the Big Bang in years/light years is real, but the later part of it is measured at a time when the universe is very small. Changes in the rate of expansion affect what is observable - to give a simple example, if the expansion slows down enough, then eventually everything becomes observable, even though it isn't now. On the other hand in a Big Rip eventually nothing is observable to anything else anymore. Wnt (talk) 03:32, 4 July 2015 (UTC)

Hmmm, on second thought, I suppose that a trace of extremely redshifted radiation always exists (the sky before the Big Rip), much like the popularized image that things fallen into a black hole always remain technically visible. The light of the distant stars that has reached within a proton's radius of a nucleus never totally falls away (though a photon almost certainly will not arrive, you would never know it won't, I think) Which makes me wonder now... no matter what cosmic inflation occurred, if the universe was ever entirely observable to itself, I suppose it always remains so, technically? Wnt (talk) 00:57, 6 July 2015 (UTC)

How interchangeable are injection molding molds?

Plastic injection molding company usually follow the following protocol: give us your design and X dollars and we will design the mold and produce Y parts within Z weeks, at the end of which we will send you the mold. My question is, how interchangeable is the said mold? If I take the mold to a different company will they be able to use it? Will the mold produced for one brand of injection molding machine work with a different brand? Are there industry standards for mold sizes and interfaces, and if so, do they differ across different countries? I'm chiefly interested in making ABS parts. My other car is a cadr (talk) 04:00, 4 July 2015 (UTC)

For example, Toshiba America publishes a catalog for Injection Molding Machines that specifies clamp and platen dimensions. You can compare to other manufacturers, and check with each vendor to determine what equipment they use, and whether they permit you to supply your own mold.

Nimur (talk) 13:20, 4 July 2015 (UTC)

Biology: What bird is this? (mp3)

I have heard this Mystery Bird in the media a few times, from the Dark Castle computer game to this recording, taken from the film The Last of Sheila. I thought maybe Whip-poor-will or Loon, but I can't find a match. Thanks! Reflectionsinglass (talk) 18:00, 4 July 2015 (UTC)

It's an owl hooting. The first bit is caught mid-call, but my guess is that it is a barred owl. Our description of the vocalization is accurate and you can hear the last few syllables fairly clearly at the beginning of the file. Matt Deres (talk) 21:36, 4 July 2015 (UTC)

I'm afraid I have to disagree, that's definitely not the call. This call is used in multiple media forms and I've heard it since the 90s and it's never sounded like an edited version of a bird call. I appreciate the suggestion though. I went to the Cornithology site and listened to all the samples and it's not the Barred owl. However, it may very well be an owl of some kind! I'll keep my ears out. Reflectionsinglass (talk) 19:01, 5 July 2015 (UTC)

The "oooooo-d-d-d-d-d" call is most commonly a barred owl. They make many calls, this one being a mating call. When I was young, I'd hear it. Then, the response would be a rising "oo-oo-oo-d-oooooo-d-d-d-d". When I listen to the recording you linked, I don't hear anything that sounds at all different than the barred owls I heard growing up. It just has a bit of echo added to it to make it sound a bit creepy. 209.149.114.69 (talk) 15:00, 6 July 2015 (UTC)

To me, it sounds just like a male Tawny owl response to a broadcast song by the female. I hear this just about nightly where I live.DrChrissy ^(talk) 15:08, 6 July 2015 (UTC)

Just as a follow up, I think that the barred owl and the tawny owl have mutually exclusive distributions. If the location of the recording is known, this could rule out one of the owl candidates.DrChrissy ^(talk) 19:45, 6 July 2015 (UTC)