Re: [Phys-l] expand your mind

["John Clement" <clement@hal-pc.org>]

Yes, they are boiled after the yeast has caused them to rise.  Then they are
baked.  Looking at the few bagels I have left at home, they are generally
smooth on the outside, but a few have flat spots where they were pressing
against another bagel.  The inside definitely shows signs of folding and has
crevasses.

They rise on a greased sheet so friction is probably fairly low.
http://www.dianaskitchen.com/page/recipes04/a40226l.htm

John M. Clement
Houston, TX

> Maybe I'm missing something, but aren't bagels boiled? That's pretty low
> friction!
>
> Bob at PC
>
>
> Anthony Lapinski wrote:
> > ... So a student today asked why actual bagels behave differently.
> > When the yeast is settling,
>
> Settling?  That means rising, right?
>
> > the bagel hole gets SMALLER. As a class we
> > reasoned that the gas in the yeast releases pressure which expands the
> > bagel. But why is this behavior different from heating a metal ring?
>
> I hypothesize it's partly -- perhaps entirely -- because the bagel is
> constrained by friction against whatever it's sitting on while it rises.
>
> This leads to an obvious prediction:  A bagel rising in zero gravity
> would _not_ exhibit hole-shrinkage.
>
> And a slightly dodgier prediction:  A bagel supported on an ultra-low
> friction surface would exhibit markedly less hole-shrinkage than
> normal, possibly none at all.
>
> Here's an off-the-cuff idea for an experimental setup:  suspend a
> not-yet-risen bagel from a bunch of long threads poking through
> it.  Use enough threads so that it doesn't sag too much between threads.
> Use a button or something on the end of each thread if needed to keep
> the thread from pulling out.  If the threads are long enough, the bagel
> as it rises can do whatever it wants horizontally, due to near-infinite
> mechanical advantage.  Take measurements and pictures before & after
> rising.
>
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