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From: ran@ho95e.UUCP (RANeinast)
Newsgroups: net.physics
Subject: Re: Re: Electric Brae
Message-ID: <483@ho95e.UUCP>
Date: Wed, 12-Feb-86 08:31:57 EST
Article-I.D.: ho95e.483
Posted: Wed Feb 12 08:31:57 1986
Date-Received: Fri, 14-Feb-86 01:11:05 EST
References: <736@brl-smoke.ARPA> <933@nmtvax.UUCP>
Distribution: net
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 26

>>    "My cousins took me to see this neat thing called the 'Electric Brae'.
>>     Have you ever heard of it?  A brae is a hill, and this one has a 
>>     peculiar property: it defies gravity!  We got over the crest of the
>>     hill, and cousin Tom put the car in neutral; now, it should have 
>>     rolled down the hill, right?  But no--the car coasted to a stop and
>>     then started backing up the hill!...

> Driving on long rolling interstates, I have also seen an illusion
> that might explain "Electric Braes".  If you drive up a long upgrade,
> and it changes to a slight upgrade, it looks as if you have breasted
> a hill and are now going down.

A human-factors friend of mine says that visual clues can be off by
as much as 15 degrees before the inner ear can detect it, so your
eyes can really fool you.

Another place with a good illusion like the interstate one is one
of the Arlington entrances to the Washington, DC Metro.  This tunnnel
descends at 45 degrees for more than 500 feet (I think).  About halfway
down, my eyes suddenly decided that the tunnel was horizontal.
I had the strangest feeling as my eyes and inner ear wrestled it out.
-- 

". . . and shun the frumious Bandersnatch."
Robert Neinast (ihnp4!ho95c!ran)
AT&T-Bell Labs