This past week, my family went on vacation to Washington DC. While there, we visited the National Museum of American history.

We entered through the mall side of the building. At first, I didn't notice the change. Then it hit me. The Foucault Pendulum is gone! The holes in the second and third floors are filled, and the tiles of the lowest-level floor have been replaced with a map of the USA.

Since a Foucault Pendulum demonstrates the rotation of the Earth, perhaps TPTB don't want us to see how the Earth is moving.

Edited to point-out that I don't think that anything nefarious is really going on. [-(

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They removed it in 1998.

http://www.si.edu/resource/faq/nmah/pendulum.htm

Tom

Short list of operating ones:

http://www.calacademy.org/products/pend3.html

Boston
Savannah, GA
Alburquerque, NM
Nashville, TN
Billings, MT
Cocoa, FL
Berea, KY
Oklahoma City
Las Vegas
Louisville, NC
Orlando, FL
Des Moines, IA
Richmond, VA
Winston-Salem, NC
Spokane, WA
Seatle, WA
Tampa, FL

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There is also one in Salt Lake City, UT at the Clark Planetarium (formerly the Hansen Planetarium), among some other pretty neat things if you're ever around these parts. :P

There's also one in Boulder Colorado that runs through the center of the 11-storey Gamow Physics tower. Go Buffs

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There's also one at the Franklin Institute in Philadelphia.

There's a description of the Institute's pendulum on their Web site:
http://www.fi.edu/time/journey/Pendu..._pendulum.html

And a page about the principle of the pendulum:
http://www.fi.edu/time/journey/Pendu..._pendulum.html

which includes links to a translation of Foucault's original paper.

There's also this:
http://www.fi.edu/time/journey/Pendu...dulum_why.html

Which explains why the pendulum doesn't return to exactly the same path after 24 hours.

IT'S BECAUSE OF PLANET X! THE EARTH IS SLOWING DOWN! OR SPEEDING UP! OR CHANGING LANES! OR MAKING A LEFT AT ALBUQUERQUE! OR SOMETHING! AIIIEEEE!
:wink:

is there one in the uk?

I think theres one in the physics department at Manchester University. Seem to remember seeing it on an open day.

There's also a small one in the physics building at Colorado State in Fort Collins.

As a CSU alum I cannot agree with this statement. [-( [-( [-(

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Last year I wanted to watch the "original" in the Pantheon, Paris, but it was temporarily removed for a large installation, some artwork. Later I saw the original weight of the first big pendulum by Foucoult in the Musée des arts et métiers in Paris, which also has a smaller, working pendulum. That museum is highly recommendable if you're interested in historic scientif instruments and such stuff.

Harald

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There's one at the Kensington Science Museum in London.

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There's one in the entrance stairwell of Sherman Hall (aka The Science Center) here at The Major Midwestern Metropolitan College Of Higher Knowledge (aka the University of Dayton). Part of the building maintenance consists of stopping the pendulum occasionally and giving it a shine (fourth article down). No pegs, but it's still kinda cool -- it's in a big glassed-in area in the entrance stairwell, and you can see it from outside as you walk by.
The building was built in the late 50's , and I can remember seeing that big brass ball swinging as I shortcut across campus coming home from grade school as a young'un...

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I do believe there is one at COSI in Columbus, Ohio.

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We have a very nice on at the Houston Museum of Natural Science in a three story atrium between the old and new buildings. It has pegs that topple every 8 minutes (I think). The text in the computer display that explains why the pendulum turns has been corrected to remove the association between the Coriolis Effect and bath tub drains after many complaints, including mine.

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thanks, that is do-able and summer is coming (1.5 days before we break up for the summer =D> ) so I think that I may just take a look. Have read the book, so would like to see a pendulum.

There was one in an office building across I-35 from the University of Texas in Austin. The cylindrical housing is still there, but I don't know if the pendulum is still in it.

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There is one at the Albuquerque Academy (private H.S.) in the sciences building -- hanging from the inside of the 3-story ceiling.

I wonder how many secondary/high schools to have a F.P.?

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Blasphemy! No mention of the one at FermiLab in Chicago? IIRC, there's also one in Portland's Convention Center.

There is also one at the The Buhl Planetarium and Institute of Popular Science in Pittsburgh, PA. The Foucault Pendulum was always the first thing I went to when we visited on school field trips. I didn't quite grasp it's significance at the time, but it was always fascinating. The rhythmic swing of the pendulum was a bit hypnotic.

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It's been many years since I took the tour, but isn't there one at the U.N., as well?

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I heard it on the news just the other day
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Haven't been there in a while but according to their website there's still one in the Museum of Science and Industry in Chicago.

There's also one here in Houston, at the Museum of Natural Science.

[edit] And Earth seems to be rotating just fine. Does anyone know how much energy it would take to stop Earth from rotating, and how a mysterious Planet X could stop it?

The Earth's rotational kinetic energy is given by the formula:

K = 1/2Iw^2, where I is the Earth's moment of inertia and w is the Earth's angular speed in radians/sec.

The moment of inertia is given by the formula:

I=2/5MR^2 where, M is the mass of the Earth in kilograms and R is the Earth's radius in meters. For our purposes we assume the Earth is a solid, uniform sphere.

Given:
M = 5.97E24 kg
R = 6.378E6 m

Then:
I = (2/5) * (5.97E24 kg) * (6.378E6 m)^2 = 9.7E37 kg m^2

The Earth has an angular speed of 2 * PI radians/day or (2 * PI) / (24 * 3600) = 7.3E-5 radians/sec.

Plug these numbers into the rotational kinetic energy formula:

K = (1/2) * (9.7E37 kg m^2) * (7.5E-5 radians/sec)^2 = 2.6E29 J

You would need to apply this much energy to the Earth in the opposite direction of its rotation to stop it.

For some perspective, consider this:

A 1 megaton explosion yields about 4.2E15 J, so the Earth's rotational energy is equivalent to 6.2E13 1 megaton explosions.

According to the Bulletin of the Atomic Scientists, the estimated total megatonnage for the world's nuclear arsenal is around 5000 MT. You would need 1.2E10 or 12 billion world nuclear arsenals to match the Earth's rotational energy.


Edited to fix a mistyped number.

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Hello,

Hamlet, you rock.

'Nuff said,

Jonathan
-It doesn't matter yadda yadda-