ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************

Bob,

I was the one who raised the 90-second time element, but NOT
recommending designing for 90 seconds.  

The idea is that it is desirable from the visitor frustration point of 
view, to have every experience come available every 90 seconds.  
Therefore, if the experience will take 3 minutes, it is desirable to 
duplicate the unit;  for 4.5 minutes, to have three units.

Of course, it's not entirely that simple;  there are ways of mitigating
the impact of the wait, e.g. by:
*  having many appealing exhibits in the vicinity
*  designing so that people can watch others - vicarious participation
*  other suggestions already made in this thread.

But we should always remember that most visitors to most centers 
come at crowded to overcrowded times, and that most centers see 
10 % of their attendance in the top 15 days of the year, so access
to exhibit experiences is a crucial factor in good planning.

All best,  Peter Anderson

***********************************************************************
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]