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March 27

Blueshifted meteors?

Perseids

I'm thinking about the adding of this to blueshift (as I suspect the blue ones are closer to the Earth than the rest), but not 100% sure. Is it really as I think? (btw, the article redshift begins the history from the 19th century, but isn't a sunset a simple example of redshift?) Brandmeister^talk 13:41, 27 March 2012 (UTC)[reply]

No. Redshift and blueshift refer specifically to variations in the frequencies of detected light owing to relativsitic effects at high velocities - compare the related doppler effect. Sunsets and sunrises, meteor showers, and other phenomena local to Earth, are not redshifted in any detectable way. You could test this by using a prism to split the light from these phenomena into spectra. You would find the absorption and emission lines of prominent elements in exactly the same places as you would if (as I understand it) you simply heated the relevant elements until they were incandescent. If you take the spectrum of a redshifted object, not only is it generally more red than you would expect, but the individual lines in the spectrum are not in their expected places; they are shifted towards the red (and infrared) end of the spectrum. AlexTiefling (talk) 13:55, 27 March 2012 (UTC)[reply]

(Edit Conflict) This space.com article states:

The Perseid meteor shower is an annual event that occurs in mid-August when Earth passes close to the orbit of the Comet Swift-Tuttle. Material left behind by the comet rams into the Earth's atmosphere during the pass at about 37 miles per second (60 km/second), creating a regular show of "shooting stars" that has become known as the Perseid meteor shower.

60 km/s is fast, but not relativistic, yielding a redshift z of about (-60 km/s)/(3x10^5 km/s) = -2x10^-4, which is still pretty small. The visible spectrum ranges from about 390 to 750 nm, so a light near the middle of this range would only be shifted by about -2x10^-4 * 570 nm ≈ -0.1 nm. Our Color vision article states that "the just noticeable difference in wavelength varies from about 1 nm in the blue-green and yellow wavelengths, to 10 nm and more in the red and blue." So no, that photograph is not a illustration of the relativistic phenomenon that is blueshift. -- ToE 14:18, 27 March 2012 (UTC)[reply]

Thanks, but what explains the different coloration of the meteors here? Rayleigh scattering? Brandmeister^talk 14:21, 27 March 2012 (UTC)[reply]

The blue and white dashed lines are not meteors. They are stars. This image is a digital composite of four fairly long exposure photographs. One meteor may be visible in the lower left corner, but I wouldn't bet money on it, without more information from the image's creator. The large blue streaking star may appear this way because it is Deneb (or a similar bright blue star), which is actually that color; or it may be due to a digital photography artifact. Nimur (talk) 15:35, 27 March 2012 (UTC)[reply]

Ah, so! It appears that four separate time-lapse exposures were taken on the one image, with the camera bumped very slightly between two of them. Unfortunately, this photo doesn't offer much for the Perseids article either. Better luck in your subsequent hunting, Brandmeister; this one ain't a keeper. -- ToE 15:49, 27 March 2012 (UTC)[reply]

LOL, the original caption confused me. Will throw it into deletion abyss. Brandmeister^talk 20:25, 27 March 2012 (UTC)[reply]

Teenage Mutant Ninja Gull

I was at a fish quay on the English coast when I was surprised to see a huge gull trying to swallow a fishhead. Common gulls I see all the time, but I don't remember seeing one like this before. It was considerably larger than the (well-fed) common gulls which were also in attendance, but had speckly-grey plumage rather than the uniform dark-grey body and white head/throat of common gulls. I had a look but I can't seem to find the one I'm looking for, a lot of the info I've found suggest this kind of colouring is found on younger birds. If this was a juvenile then I wouldn't want to meet the daddy while carrying a portion of chips. Any ideas what this was? Someone another 15:36, 27 March 2012 (UTC)[reply]

Sounds like a juvenile European Herring Gull. They are big and greedy.--Shantavira|^{feed me} 15:51, 27 March 2012 (UTC)[reply]

The largest gull in the world is the Great Black-backed Gull, which can be found on the English coast. Our article has an image for juvenile plumage, but juvenile plumage can be more variable than adult, because it depends more on age, etc. Note that it takes up to four years for this bird to get adult plumage, but an individual may reach its max weight before then. SemanticMantis (talk) 15:55, 27 March 2012 (UTC)[reply]

It could have been either a Herring Gull or the Great Black-back, I can't remember the bill colour, just the plumage. It was big and I was glad to be eating in the car is what I most remember. It was like looking out of the kitchen window and seeing a blackbird the size of a wild dove. Thanks for your responses, next time I'm in the area I'll take a closer look at their beaks. Someone another 16:16, 27 March 2012 (UTC)[reply]

You have to run this question by our resident gull expert, User:Kurt Shaped Box. StuRat (talk) 20:54, 27 March 2012 (UTC)[reply]

Hi! :) I'd agree with what was written above. A European Herring Gull is about the size (but not weight) of a domestic chicken. A Great Black-backed Gull is a couple of inches taller and much wider. I actually saw one stood near a Canada Goose yesterday - the GBBG was half-asleep and fluffed up to the max and actually appeared to be the same size. This is always a good picture to show people when discussing Great Black-backs. :) --Kurt Shaped Box (talk) 21:40, 27 March 2012 (UTC)[reply]

Your ears must have been burning. I saw that you hadn't edited Wikipedia for 10 days, then I mention your name in you're here in under 45 minutes. StuRat (talk) 21:53, 27 March 2012 (UTC) [reply]

Yeh, I haven't been on my computer much recently. Just checked my watchlist for the first time today and saw a gull-related question staring at me... :) --Kurt Shaped Box (talk) 21:56, 27 March 2012 (UTC) [reply]

Sudden appearance of gulls ? Sounds fishy. :-) StuRat (talk) 22:08, 27 March 2012 (UTC) [reply]

They do though, don't they? One minute there's none around, but as soon as you start eating something outside at the seaside, there's tens of them stood around you with expectant looks on their faces... --Kurt Shaped Box (talk) 00:20, 28 March 2012 (UTC)[reply]

More possibles could be the Lesser Black-backed Gull (common, similar size to EHG, perhaps slightly smaller) or Glaucous Gull (uncommon in England, a very big bird, sometimes nearly as large as GBBG). There are a great number of gull species that look very similar when young, with only subtle plumage differences which may not always be there, may not be there in all seasonal variations, or may have been worn away/altered by the elements, or ripped out when gull was fighting. Hell, that can be true of the adults too. Many species that outwardly seem little more than subtle palette swaps of each other. --Kurt Shaped Box (talk) 00:20, 28 March 2012 (UTC)[reply]

Do we trust the OP enough to rule out terns or skuas or things like that? Looie496 (talk) 02:36, 28 March 2012 (UTC)[reply]

Everything about it said gull, the shape of its beak, head, its eyes, its call, it was just the juvenile plumage and size which separated it from the common gulls. I'm not what you'd call a twitcher but there was a couple of these things and they were squabbling and calling only feet from the car for several minutes. This was some months ago so my memory of exactly how big they were isn't fresh - I'm not sure that they were quite big enough to be Great Black-backs. That said they were very well built and a lot bolder than the other gulls, so I'm not sure if that points to them being more mature GBBs as opposed to Herring Gulls. Someone another 14:08, 28 March 2012 (UTC)[reply]

This might be a useful video to watch and see if it jogs your memory. A few young Great Black-backs and an adult picking bits and pieces from a fishing net alongside several smaller gulls. --Kurt Shaped Box (talk) 17:08, 28 March 2012 (UTC)[reply]

Looking at the video and comparing it to the photo of the juvenile Herring Gull in the article here I think it was probably the Herring Gull. The dark feathers on the Greater Black-backs don't ring a bell, from what I can remember the gull I saw had a white head and neck with small brown flecks like the Herring Gull has, but they weren't as tightly-packed - it was far more white than fleck. I don't remember anything about the body/wing colour, I think that's probably because it would have been white/pale grey (which again matches the Herring Gull, but not as coloured as the juvenile in the photo). Does that sound right? Someone another 20:05, 28 March 2012 (UTC)[reply]

Most large gulls take 4 years to reach adulthood (GBBG can be longer). In that time, they go through several plumage changes, becoming less speckled/brown each time they moult. By the third year, they have a lot of the adult colour showing through. The wings would be starting to look the same colour as an adult by then too (i.e. EHG would have grey, GBBG would have black). Take a look at commons:Category:Larus argentatus (immature) for more examples of this than you probably care to see. --Kurt Shaped Box (talk) 11:34, 29 March 2012 (UTC)[reply]

This one is the closest resemblance - mostly white neck with some light coloured flecks, pretty sure that's the one. That's that mystery solved, thanks to you Kurt and everyone else who took the time. Someone another 11:57, 29 March 2012 (UTC)[reply]

Resolved

FACTORS AFFECTING EMISSION OF EXHAUST GASES FROM A PETROL ENGINE

what is the effect of engine speed of petrol engine on exhaust gases? Can i get any article or any webpage that describes the factors(SPEED,LOAD,RATE OF FLOW OF COOLANT) affecting emission of flue gases like CO₂, CO ,SO₂, NO_x Effect of engine/vehicle speed on carbon dioxide &carbon mono-oxide emission. Effect of load/number of passengers on carbon dioxide &carbon mono-oxide emission. Effect of rate of flow of coolant on carbon dioxide &carbon mono-oxide emission.

Effect of engine/vehicle speed on SO₂, NO_x emission. Effect of load/number of passengers on SO₂, NO_x emission. Effect of rate of flow of coolant on SO₂, NO_x emission. Any information regarding any of above mentioned topics will be helpful. — Preceding unsigned comment added by Akash AD Sharma (talk • contribs) 15:59, 27 March 2012 (UTC)[reply]

One comment: The total amount of exhaust gases will, of course, tend to increase when an engine is doing more. However, I think the relevant comparison is the ratio of work done to exhaust gases produced. In that case, a typical engine will have a "cruising speed" where it operates at optimal efficiency. If you increase or decrease the speed from that point, you will lower that ratio. StuRat (talk) 20:46, 27 March 2012 (UTC)[reply]

Another comment: The fuel/air mix is also critical. For example, too much fuel and/or too little air will result in more unburned fuel and possibly carbon monoxide. StuRat (talk) 20:49, 27 March 2012 (UTC)[reply]

Lens pap ?

I just finished a crossword puzzle with one annoying weirdness. Where I thought the answer was "lens cap" (for clue "a camera accessory"), it didn't work with the other clue "to start something", which I answered as "incept":

        L
        E
        N 
        S
I N C E P T
        A
        P

Obviously "incect" is nothing, so it can't be "lenscap". All the other letters match the words going the other ways. So, is there something called a "lenspap" or "lens pap" (maybe it's short for "lens paper") ? Or did they just screw up in making this puzzle ? StuRat (talk) 21:48, 27 March 2012 (UTC)[reply]

Is this puzzle online somewhere? If not, could you post the other words crossing with these words, if any? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:23, 28 March 2012 (UTC)[reply]

Not online. It's a pretty solid grid of letters with very few blank spots, and everything else fits perfectly. Let's wait a couple days, and if still needed, I will post more of the puzzle. StuRat (talk) 02:02, 28 March 2012 (UTC)[reply]

Which letters in "incept" cross other words? --Tango (talk) 00:37, 28 March 2012 (UTC)[reply]

All of them. StuRat (talk) 01:54, 28 March 2012 (UTC)[reply]

s/incept/effect. Nimur (talk) 01:17, 28 March 2012 (UTC)[reply]

I'm not sure what you're trying to say, Nimur. StuRat (talk) 02:00, 28 March 2012 (UTC)[reply]

The "s/" is "hacker slang" for telling you to replace one thing with another. He's suggesting that you replace "incept" for "effect" which means "To make or bring about; to implement". That screws up any crossing words, of course. But seems likely based on what you told us. APL (talk) 02:09, 28 March 2012 (UTC)[reply]

I hate to leave people hanging - to be specific, the "slang" is syntax for a Perl regex (see the latter article for examples). Wnt (talk) 19:30, 28 March 2012 (UTC)[reply]

Technically, the "s/something/somethingelse/" syntax comes from ed, mostly by way of sed: "sed and AWK are often cited as the progenitors and inspiration for Perl. The s / / / syntax shown below is part of Perl's syntax and originated with ed, the precursor to sed." -- 140.142.20.101 (talk) 01:15, 29 March 2012 (UTC)[reply]

Searching for "lens pap" on Google comes up nil, but I did come across "lens pen" and maybe that will help. --Modocc (talk) 01:52, 28 March 2012 (UTC)[reply]

What about "incite" for "to start something" and we look for some other kind of camera accessory... --Jayron32 01:55, 28 March 2012 (UTC)[reply]

I'm not sure why this is on the science desk but as evidenced by the other answers I think we're going to need more of the puzzle possibly the whole thing because it's possible other words need to be fixed. Nil Einne (talk) 03:19, 28 March 2012 (UTC)[reply]

I put it here since I thought of photography/optics as a science and was hoping somebody would recognize the term. StuRat (talk) 03:31, 28 March 2012 (UTC)[reply]

It sounds to me more like something someone highly involved with photography would be familiar with (and they may not necessarily consider the science much beyond what they need) Nil Einne (talk) 07:18, 28 March 2012 (UTC)[reply]

Induce might be another possibility for the crossing word. Red Act (talk) 04:04, 28 March 2012 (UTC)[reply]

Or insect if the word that crosses at the third letter has an alternate spelling with an s.Sjö (talk) 21:23, 28 March 2012 (UTC)[reply]

But how does "insect" mean "to start something"? I suppose you could start a fight by bugging someone. :-) StuRat (talk) 21:40, 28 March 2012 (UTC)[reply]

Sorry, I didn't read the OP carefully.Sjö (talk) 10:45, 29 March 2012 (UTC)[reply]

Follow-up: Some of you asked for the surrounding letters and clues, so here they are:

    T
    R
    A
    F   L
O A F   E    -> Klutz.
A S I A N    -> Syrian or Singaporean.
S O C K S    -> Darned things.
I N C E P T  -> Introduce, as something new (this was slightly different than I recalled).
S E A L A B  -> Naval underwater habitat.
    M A P S  -> Things stored in a GPS.
^ ^ ^ ^ ^ ^
 \ \ \ \ \ \
  \ \ \ \ \  -> Basic cable station.
   \ \ \ \  --> Camera attachment.
    \ \ \  ---> Cub scout leader.
     \ \  ----> Helicopter report, perhaps.
      \  -----> In unison.
        ------> Pleasant change.

So, does this help anyone to see a solution ? StuRat (talk) 03:14, 30 March 2012 (UTC)[reply]

How about if the helicopter report is TRAFFIC JAM and introduce is INJECT? – b_jonas 09:23, 30 March 2012 (UTC)[reply]

I think you solved it, thanks ! StuRat (talk) 15:33, 30 March 2012 (UTC)[reply]