On Sat, 22 Dec 2007 07:05:07 -0800 (PST), JJ Sinclair
wrote:

When circling near a steep mountain some pilots get a strong sensation
that they are diving each time the circle faces the steep terrain. Why
is this? Our mind tries to make the side of the mountain, the horizon.
Let's do a little test; Point your left hand up about 30 degrees to
simulate the side of a steep mountain. Next, make believe your right
hand is banked up in a 45 degree left turn, thermalling into the
mountain. Now, rotate both hands down to make the mountain side
parallel to the earth. What attitude does your right hand show? A
diving left turn!

Most experienced mountain flyers know about this false sensation and
simply look over their shoulder to pick up a bit of real horizon each
time they face the mountain as they thermal their way up the side. I
get this false sensation every time I thermal close to Mt. Shasta
which rises up to 12000 feet above the valley floor at about a 30
degree angle. When flying with other pilots in a 2-place ship, they
have occasionally shouted out; "We're diving" when facing the
mountain. Plug this tid-bit away in your bag of tricks and don't let
this false monster get you some day.
Have a Happy, Happy (politically correct for the forthcoming season).
JJ

More generally, our minds try to make the surrounding terrain level.
If you ride the cog railway to the top of Pikes Peak, you go up quite
a steep slope, and about a third of the way up you pass a house
sticking out of the slope with a deck suspended on stilts. The
passengers typically show some level of disbelief when the conductor
announces "That house is on the level."

Next to the old US 6/40, pre-Interstate, west of Denver there used to
be a pond perhaps a hundred feet across. As you drove down from the
mountains, you could swear that pond was substantially tilted; my wife
named it "the slanted lake".

rj