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For an activity this Astronomy Day I am looking at making postcards from
the planets. To complete the picture, It would be great if the postcards
could actually be stamped with "Pluto - Via Fusil" or some such.
Is there a way to do this without having rubber stamps custom-made? Keep
in mind that this has to be fairly small, with neat text.
Marc Taylor
Coordinator, Andrus Planetarium
Hudson River Museum
511 Warburton Avenue
Yonkers, NY 10701
(914) 963-4550 x223
Fax: 963-8558
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-----Original Message-----
From: Informal Science Education Network
[mailto:[log in to unmask]]On Behalf Of [log in to unmask]
Sent: Monday, February 02, 2004 2:12 PM
To: [log in to unmask]
Subject: Re: What To Do With A Big Vacuum Pump? An Exhibit?
ISEN-ASTC-L is a service of the Association of Science-Technology
Centers
Incorporated, a worldwide network of science museums and related
institutions.
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A large vacuum pump which uses a 25 horsepower (about 20 kiloWatt)
motor?!! I hope that anyone designing an exhibit using such a powerful
vacuum pump to evacuate a sizable chamber is cognizant of the hazards in
dealing with evacuating large volumes. Most school demonstration
systems use glass bell jars which have a rather small volume (a few
liters or less) and strong, thick-walled glass bell jars whose shape as
well as thickness enable them to withstand large inward force. But when
the air inside is evacuated the atmospheric pressure pushing inward on
the glass walls is close to one ton per square foot (or about 10 metric
tonnes per square meter), arrived at by multiplying the familiar 14.7
pounds per square inch by 144 square inches in 1 square foot. As a
familiar example consider a television picture tube, which has a
near-perfect vacuum inside, and the size of the face is typically two or
three square feet. The inward force exerted by atmospheric pressure on
the face of the tube is therefore two or three tons, and the glass must
be thick enough to have the strength to withstand this much inward push.
Should the glass break, this much force acting on the fragments will
accelerate them to great speeds, and could cause disastrous damage to
anything, living or inanimate, which happens to be nearby.
When I was an undergraduate my physics professor told about an episode
he experienced when he was working in a commercial research laboratory
in which a vacuum system included a large glass bottle, probably about
five or ten gallon. The bottle failed (fortunately at night when the
laboratory was unoccupied) and peppered the concrete block walls with
shards of glass which imbedded themselves into the concrete. One can
imagine the injuries or worse which would be inflicted on any person who
happened to be in the lab when the bottle imploded.
Albert J. Read, Director, Science Discovery Center of Oneonta (NY)
-----Original Message-----
From: Informal Science Education Network on behalf of Mike Levad
Sent: Mon 2/2/2004 9:46 AM
To: [log in to unmask]
Cc:
Subject: Re: What To Do With A Big Vacuum Pump? An Exhibit?
ISEN-ASTC-L is a service of the Association of Science-Technology
Centers
Incorporated, a worldwide network of science museums and related
institutions.
************************************************************************
*****
I would set up a chamber with a miniature kite inside. You can could
attach the kitestring to the end of an arm that is spun by a motor.
When you remove the air no matter how fast you turn the arm the kite
will fall below the arm. As soon as you let the air back in the kite
will fly inside the chamber above the arm. The kite itself can be as
small as 1". If you need more kite information let me know.
Mike
--
Mike Levad
Exhibit/Program Developer
The Franklin Institute Science Museum
222 N. 20th St. Philadelphia, PA 19103
Voice:215.448.1309
Fax:215.448.1188
E-mail: [log in to unmask]
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More information about the Informal Science Education Network and the
Association of Science-Technology Centers may be found at
http://www.astc.org.
To remove your e-mail address from the ISEN-ASTC-L list, send the
message SIGNOFF ISEN-ASTC-L in the BODY of a message to
[log in to unmask]
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More information about the Informal Science Education Network and the
Association of Science-Technology Centers may be found at http://www.astc.org.
To remove your e-mail address from the ISEN-ASTC-L list, send the
message SIGNOFF ISEN-ASTC-L in the BODY of a message to
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