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Plant Sciences, Zoology & Evolution / How does fur know when to stop growing?

« on: 31/08/2012 17:22:02 »

One of my cats recently had to some of his fur shaved off in order to have blood drawn accurately. As the patch grew back, I began to wonder... How does cat fur "know" when it is long enough to stop growing? And how does it "know" when to detach from the cat?

Genes, hormones, etc., I'm sure, but more detail would be wonderful.  Thanks!

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Plant Sciences, Zoology & Evolution / Smelly Cat, Smellier Dog?

« on: 13/05/2012 01:53:58 »

While eating dinner with a friend last weekend, her 75lb mastiff began to have some rather noticeable flatulence issues.  My friend claims that this is normal, as despite the fact that her dogs (the other is a chihuahua) are well-fed, exercise regularly, etc., it is just something dogs do.  I've never noticed my cats contributing similar smells to my surroundings.  Why do dogs pass gas more noticeably than cats? 

...It can't be all down to size, as both of my cats are larger than her smaller dog, and her little one is definitely not flatulence-free.
...If it makes a difference, all four of our pets are on grain-free diets.  My cats eat wet and dry food, while her dogs eat only dry food.  My cats are indoor-only and her dogs never go outside unsupervised and are usually on their leashes.

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General Science / Why does old tea change colour?

« on: 17/11/2011 14:23:53 »

Hate to beat a dead horse here, especially since you have done such a wonderful job of explaining this, but... yesterday's tea didn't change by this morning.  It occurred to me that I hadn't purposely tested each of the teas I have on hand, and that there was one in particular I might have forgotten.  If you follow the links, you'll head to Teavana's page for each tea.  They include ingredient lists as well as pictures of what the tea looks like when brewed.  (They don't have pictures of how dark the teas turn if you leave them out, but why would they?) I know I can't rule out all the variables, as Geezer pointed out, but this is water from the same source, made in the same way using the same equipment, etc., involved in the initial incident, aside from the different tea.  It wouldn't hold up to rigorous scientific standards, but I did what I could with what I had.  Oh, and the tea made from second or third steepings of the same leaves does darken over time, too, but I haven't tried to compare how much relative to the first steeping.  Any theories?

LINKS TO COMMERCIAL TEA WEBSITE REMOVED - MOD.

(I haven't left them out separately yet, as they were a pre-blended gift.)

I'm eager to read your input, and thanks again for your insights!

(By the way, if you like straight up white tea, Silver Needle is great, and while the Pearls are better, I stick to the relatively economical version when purchasing for myself.)

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General Science / Why does old tea change colour?

« on: 07/11/2011 12:01:05 »

Thanks; that helps quite a bit!  If I understand you correctly, the oxygen dissipates more quickly at the higher altitude.  This may sound like a silly question, but how/why does oxidisation cause the colour change?

Also, could this have anything to do with evaporation?

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General Science / Why does old tea change colour?

« on: 05/11/2011 14:52:10 »

Thanks, but here's where I admit that chemistry is not my forte.  How does the process work in this context, and why does it cause darkening?  And why didn't it seem to happen, at least not as noticeably, at the lower elevation?

Bonus points if you can explain it using a diagram or other (semi-)abstract visual, albeit one that might be hard to convey on a radio podcast.  My math focus is pedagogy at the elementary (primary) level, and since I've already tried the concrete phase on accident, a connection to the abstract terminology would be quite helpful.  I often find that explaining a process as one would for a child--not patronizingly, rather by bridging concrete to abstract and/or physical to visual to symbolic models--helps both student and teacher better understand the process.

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General Science / Why does old tea change colour?

« on: 02/11/2011 15:01:07 »

Stephen Tucker  asked the Naked Scientists:
   
Dear Chris & Co.,

As a relatively new listener to the podcast, I must first thank you for your excellent programme.  As a doctoral student in the field of mathematics education and leadership, I love to learn, particularly about things I know very little, which leaves a plethora of choices.

Every morning I drink a mug of loose-leaf tea.  (We Americans can't handle small amounts of things... it is 16oz instead of 8oz... we can't even use the metric system, though I did impress it upon my students when I taught primary school.)  I vary my pre-dawn pick-me-up between several (Teavana) flavors, but they are usually white, herbal, or rooibos teas.  Some have fruit or floral bits, others herbs or spices, a few are just the tea leaves.  The brew's color usually ranges from nearly clear to yellowy or greenish, or even pink, but never brown except the rooibos, which is reddish-brown.  (No black
 teas; I don't need the caffeine.)  One morning I left my tea unfinished and did not make it back to my desk until the next morning.  The leftover tea was dark brown.  The next week, with a different type of tea (and a different mug), the same thing happened; the tea started pale green but turned brown by the next morning.  I have done this several times, starting with a clean glass mug and usually leaving just a few ounces of tea to see what happens, and I always return to a brown liquid, even when I haven't had rooibos tea.  I don't recall this ever happening before.  If it makes a difference, I now drink my tea in Logan, Utah (elevation 4,534 ft or 1,382 m) instead of Charlotte, NC (elevation 751 ft or 229 m). Given that I pour the steeped tea through a strainer so few if any bits ever make it into the mug, why does my tea turn brown?  And no, I have not yet tried to drink the results.

I  know that rambled for quite a bit, but I wanted to make sure I included all the details I could.  Thanks, and keep up the good work!

Stephen Tucker
Utah State University

What do you think?