Reinventing Barsoom: 1 planetology and geography

[whswhs]

Originally Posted by dcarson

OK. Horizon is sqrt [ 2 x radius of planet x height above surface + height above surface ^2]

So using 3390 km for radius and 7 km for height of the walls the horizon is 218 km. The canyon is 200 km wide so you can see all the way across. That is using max depth. If parts of the canyon are only 3 km deep you can't see either wall from the middle. If it is less than 6 km you can't see both. Which may be what I'm misremembering.

Putting your formula into Excel, I agree with your 218-km horizon for walls 7 km high. But at 5 km the horizon is 184 km, which means you'd have to be within 16 km of one wall to be unable to see the other. If by "the middle" you in fact mean "halfway between the walls," each wall is 100 km away, and even 2-km walls give you a horizon of 116 km. The effect seems much less extreme than you're describing, unless I'm doing something wrong.

Too bad; it was a pretty image.

Bill Stoddard

[dcarson]

Probably me misremembering. Not being able to see the far wall is still interesting though.

[Johnny1A.2]

Originally Posted by whswhs

Putting your formula into Excel, I agree with your 218-km horizon for walls 7 km high. But at 5 km the horizon is 184 km, which means you'd have to be within 16 km of one wall to be unable to see the other. If by "the middle" you in fact mean "halfway between the walls," each wall is 100 km away, and even 2-km walls give you a horizon of 116 km. The effect seems much less extreme than you're describing, unless I'm doing something wrong.

Too bad; it was a pretty image.

Bill Stoddard

It's salvageable. There are many 'side' canyons associated with the Valles Marineris, it's not unlikely that one of them would be suitable to produce the visual effect desired.

[Agemegos]

Originally Posted by Johnny1A.2

It's salvageable. There are many 'side' canyons associated with the Valles Marineris, it's not unlikely that one of them would be suitable to produce the visual effect desired.

I think the problem is that Valles Marineris is too narrow. Side canyons would have to be very shallow to get the effect desired.

[whswhs]

Originally Posted by Brett

I think the problem is that Valles Marineris is too narrow. Side canyons would have to be very shallow to get the effect desired.

That's what the equations imply, so yes.

(One of my vignettes in Social Engineering is set in Valles Marineris; it involves competition between two taverns, Bottle City and The Labyrinth.)

Bill Stoddard