[Chi Ho Cheung (Eric)]

Chi Ho Cheung (Eric)  asked the Naked Scientists:
   
Hello Dr. Chris and naked staff,

    My name is Eric, in Seattle, Washington, USA. I'm a big fan of the show. (I bought a Zune [ipod, but from microsoft] just so I can listen to all the naked shows).

For the same gradient/slope, why does it feel so much less comfortable / less stable / more scary when I'm facing downhill instead of uphill?

I wonder if there is something mechanical about our legs. The same goes when I'm flying, the plane can pitch up 15 degrees or more and I feel perfectly fine, but when the plane pitches down to -5 to -10 degrees, I feel like I'm about to be thrown out of the plane through the front windows.

Maybe this time is the way we sit in chairs.

Thank you very much! Happy summer!

Regards,
Eric Cheung
University of Washington

What do you think?

[tangoblue]

Maybe it is because when you are looking uphill your brain knows there is no real danger, as in if you fall you will not fall far. wheras if you are looking downhill your brain may relise that if you fall you have quite a way to go. just a guess though.

[palau]

Maybe it is because when you are looking uphill your brain knows there is no real danger, as in if you fall you will not fall far. wheras if you are looking downhill your brain may relise that if you fall you have quite a way to go. just a guess though.

That is the correct answer.

[tangoblue]

wow! i actually guessed something right []

[ccheric]

Hi I am the one who asked this question.

Thank you for Tangoblue's response, and it gets me thinking,

FOR:
From the visual sense, looking down, you do see all that miles of hill you will roll down, which is scary. I think this is quite consistent for when I am flying, we use the horizon as a metric to determine if we are flying up or crashing down. Only a few degrees of pitch down, will effectively fill your field-of-view with the ground, as in the ground which you will crash into. This can even work when there is no real change in the pitch of the body. When you are sitting in an airplane, and the airplane banks for a turn, the ground will fill the window, which always feels more threatening than the other side of the airplane.

AGAINST:
If you are standing on a hill looking up, you can fall backwards; if you are looking down, you can fall forward. In fact, statistically, we always fall into the hill regardless of which way we are facing. Conservatism. So in this case, does vision matter?

[tangoblue]

i know what you are saying about falling backwards, but i do think vision is very important because if you can't see the length you will fall when you are faceing forward (even if are aware of the distance) it wont seem as scary as when you are actually looking downhill.