[time-nuts] ***SPAM*** Exploratorium, timekeeping, pendulums, mirror

[Randy D. Hunt]

On 4/20/2013 1:59 AM, Hal Murray wrote:
> For those of you who aren't familiar with it, the Exploratorium is the great
> grandaddy of the hands-on science museums.  It was started by Frank
> Oppenheimer way back in 1969.
>
> Anybody nutty enough to be on the time-nuts list would have a great time
> there.  They welcome big kids as well as little kids and everything inbetween.
>    http://en.wikipedia.org/wiki/Exploratorium
>    http://exploratorium.edu/  (time sink warning)
> (The best exhibits are fascinating to both toddlers and PhD physicists, but
> maybe not for the same reason.)
>
> I highly recommend it to anybody in the San Francisco area, either as a local
> or as a visitor.  (Locals might want to wait until the "new" rush calms down,
> but that might take a while.)
>
> They recently moved to a new location at Pier 15 on San Francisco's
> Embarcadero.  Last Wed was their official grand opening for the general
> public.  They had many preview events in the previous week or two: donors,
> press, members, ...
>
> http://blog.makezine.com/2013/04/15/san-franciscos-new-exploratorium-unveiled/
>
> A good friend of mine works there.  He got me in last Sunday for the
> employees and friends (and teachers) preview.
>
> They have a good collection of pendulum exhibits, obvious bait for time-nuts.
>
> Google for >Pendulum Exploratorium< will get lots of hits.
>
> ----------
>
> One is a set of pendulums with decreasing lengths.  You start them all in
> sync.  The lengths are carefully adjusted to an integer number of cycles in
> 30 seconds.  After 30 seconds, they all come back in sync again.
>    http://exs.exploratorium.edu/exhibits/pendulum-snake/
>    http://www.youtube.com/watch?v=Q3KRWJ7ScB0
>
> ----------
>
> You can make a pendulum of length X run slower by putting a counterbalance
> weight on the other side.
>
> Is there a similar trick with crystals?
>
> ----------
>
> >From the old place:
>    http://jackaperkins.wordpress.com/2010/12/23/the-exploratoriums-harmonic-pen
> dulum/
>    http://exs.exploratorium.edu/exhibits/resonant-pendulum/
>
> I didn't see it last Sunday, but I could easily have missed it.
>
> ----------
>
> One neat exhibit is poor by the Exploratorium standards because there is
> nothing to do or touch, but it's so neat they have it out on the floor
> anyway, and it's clearly time-nuts bait.
>
> It's a movie, taken from above, projected onto a 5ft dia screen.  The field
> of view is roughly 30 feet across.  It shows the hands of a clock.  They are
> made out of trash.  2 guys with brooms are continually adjusting it, moving
> the hands to keep time.
>
> Here is a 5 minute video.
> Sweepers clock
>    http://www.youtube.com/watch?v=SXNT4T56EmM
>
> Anybody want to estimate the adev?  :)
>
> -----------
>
> They have several coupled pendulum exhibits.  Are coupled pendulums (or
> oscillators?) useful for timekeeping?  They sure are weird face to face.
>
> The best one is out front as an art exhibit.  It's a T with swivel arms on
> each end of the T.
>   http://exs.exploratorium.edu/exhibits/chaotic-pendulum/
> Total chaos, but fascinating.
>
> I've seen small plastic versions.  This one is big, serious, made out of
> steel.  It's enclosed in a plastic box so the flailing arms won't break any
> human arms, fingers or skulls.  It's amazingly seductive especially if you
> approach when it is idle (rare), all you have to do is give the obvious knob
> a gentle twist and it goes berserk.
>
> I gather it's very good at "testing" the bearings. (Fortunately, the
> Exploratorium staff is very good at fixing things.  It's part of their
> culture.)
>
> -----------
>
> They had two honest to goodness clocks.
>
> One was a classic tower clock driven by weights.  There were motors to
> automagically rewind the weights.  It was packaged inside a glass box so you
> could walk around and look at everything.  (It was nice to look at, but there
> was nothing to do/touch so it was low on the Exploratorium goodness scale (my
> opinion).)
>
> The other was a new art exhibit.  Once, I saw it doing it's dance, but mostly
> it just sat there so I wasn't very interested.  It was big so you couldn't
> see the details.
>
> Tinkerer's Clock
> http://www.exploratorium.edu/visit/south-gallery/tinkerers-clock
> http://blog.makezine.com/2013/04/15/san-franciscos-new-exploratorium-unveiled/
>
> It didn't have anything to do or poke that I noticed.
>
> -----------
>
> I think the coolest new exhibit is a giant mirror.
>    http://www.exploratorium.edu/visit/central-gallery/giant-mirror
> I can't think of any way to link it to time, so the rest of this is OT.  :)
>
> The place closed at 5.  We weren't going to make the 5:15 train, so we sat
> down and relaxed for a while before heading for the 6:15 train.  On the way
> out, we stopped by the mirror.
>
> The mirror is 12 ft wide and 8 ft tall, facing you.  The focal distance is
> about 6 feet.  If you are outside the focal distance, everything behind you
> is inverted.  Your brain adapts quickly.  As you step inside that line, your
> giant head turns right side up.  The background stuff is still upside down.
> Your brain locks on to you and flips to normal mode.  For me, the place was
> closed so nothing in the background was moving and my brain ignored the
> background.  Then somebody walked by in the way way back.  My brain parsed
> that as walking on the ceiling.  It took a long fraction of a second to
> remember all the upside down possibilities and figure out what was going on.
>
> Things like that are the reason I go to the Exploratorium.
>
>
Been there - done that.  Yes, it is a great place (as I remember it) but 
the last time I was there was 40 years ago. . .

Randy, KI6WAS