I'm afraid we won't. Ignoring the fact that our bones and muscles cannot support such an action, we're missing a few key issues. Firstly, birds and aircraft use airfoils. This is where the shape of the wing creates a vacuum which lifts the wing. In addition to this, flapping actually doesn't use friction, it relies on a similar notion as pushing yourself off a the ground in a push-up. While obviously there is fiction in every action, friction is not the cause of lift.

I love me some double jumping. UT2k4's got it, and all that fancy dodging adds a great deal to the game. Feels a lot tighter than, say, Halo, where you get the one jump, and if you're lucky a grenade will go off underneath you as you do it. Also, it's great for navigating 2d area. Smash Bros. benefits enormously from the jump controls.

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Original post by Kest You're missing the fact that friction, as in your equation, is relative to the number of times we can apply force against it before gravity does its thing. If we could move fast enough, we could swim through air by just taking advantage of simple aerodynamics.

Air is neither boyant enough (to support/provide upthrust to us as water does) nor viscous enough (to allow us to provide upthrust from 'kicking' - resistance to motion.)

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Original post by Moomin Quote: Original post by Kest You're missing the fact that friction, as in your equation, is relative to the number of times we can apply force against it before gravity does its thing. If we could move fast enough, we could swim through air by just taking advantage of simple aerodynamics. Air is neither boyant enough (to support/provide upthrust to us as water does) nor viscous enough (to allow us to provide upthrust from 'kicking' - resistance to motion.)

It's extremely simple. Gravity is applied over time. If there is any type of motion that can provide any amount of lift, then given enough speed, flight is possible.

I'm not saying flight is naturally feasible for humans. I'm saying it's physically possible to achieve flight with amplified physical abilities.

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Original post by Dasubermechen why is this mechanic in so many games and why does it, of all unrealistic elements, get past questioning?

People don't care about breaking realism if it's more fun that way!

Team Fortress 2's Scout has a double-jump, and there's no legitimate explanation. He can even alter his direction instantaneously in mid-air. I don't care if it's impossible; it's still fun.

Looking at it as purely a gameplay mechanic and nothing more, the double jump is typically preferred over a massive jump because it allows for more precision. A player can jump a great distance, and then on the second jump, refine their position to be sure they land. And, in cases of games similar to Metroid, the double jump itself can become an item to be collected, adding a sense of growth and empowerment.

As for whether or not it's physically possible, I think that's kind of a moot point. In the games it is used in, reality is hardly the basis for what is happening. And the need for character growth and the gameplay benefits associated with the double jump far outweigh the "but this is impossible" reaction.

Easier error correction = more fun. If you miss by some sort of margin, you're second jump can fix that. Also makes mobility alot better; imagine fighting like DMC, you jump and an enemy ends up below you with his stupid vine thing wavy around, you don't want to land on it and need to get out of the way, a double jump will enable that, whereas a long/higher jump wouldn't.

Not to mention, its proven to be well accepted.

I am thrilled by many of your responses, great points and good speculation.

At no point however was my intention to get people to debate whether or not its achievable in real life.

I sort of agree with Kest on this one. The difference in real life is that if we could somehow bend the physics involved to our will (air dense enough, body sparse enough, bones/muscles strong enough) then we'd be swimming in the air, rather than jumping off of it, because we can simply put ourselves at whatever altitude we want and stay there, like we can in water. If it were a jump, we'd have to return to the ground eventually.

Rationalizations aside, the purpose of the double jump is to allow the player to change his/her vertical velocity (and sometimes horizontal velocity if the game gives you little air control) in mid-air. This lets you cross underneath obstacles that float above the void, or like pothb said, to correct a mistake like landing in a bad place or falling into the void.

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Original post by Dasubermechen At no point however was my intention to get people to debate whether or not its achievable in real life.

It wasn't my intention to start one either, so I apologize.

Still, any concept worth debating as being possible is less likely to make players question it, so it is related to the question at hand [smile]