[IvyMike]

I've always been curious: in an enclosed stadium on the moon, would humans run the 100 yard dash faster or slower?

I think the first reaction people have is "faster, since you weigh less". But I think the answer is slower, because you would actually be near-floating and contact the ground less.

I got into a fight with people on ask.metafilter when I asked this same question, so I had to let it go. But still I hope someday the Olympics are held on the moon so I can get my answer.

[jcrites]

You would certainly accelerate much more slowly, since the upper limit of acceleration is bounded by your friction with the ground, which is bounded by your weight, i.e., your mass times gravity.

What's not clear is whether you could reach a faster peak speed. I think it would be tough to reach a fast speed since your joints would need to oscillate rapidly in order to push off ground moving as fast. And each time you push off the ground you'd achieve less force, due to the friction thing. To summarize, I think I agree with you that humans will run more slowly in a low-gravity environment.

An interesting parallel question is: under 1.3, 1.5, or 2x gravity, how much more quickly could you run? And what's the optimal gravity for running if it's not 1.0 Earth?

[thaumasiotes]

> what's the optimal gravity for running if it's not 1.0 Earth?

Is "optimal running gravity" the gravity under which you'll run the fastest, or the gravity under which you'll have suffered the least amount of physical damage after running for a fixed distance/time?

[omegant]

Would a 2x gravity be similar to running with a 100 pounds backpack? Then I guess it's going to be substantially slower than 1G running.

[recursive]

No. The runner still has the same mass, so accelerating takes the same amount of energy as 1x gravity. It's like shifting to a higher gear on your bike.

[crystaln]

Not exactly. Horizontal acceleration takes the same amount of energy. The mass of the body must also be supported upon landing, which obviously takes more energy with more gravity.

[jcrites]

Interesting. So it will feel like your normal weight in the horizontal dimension, but it will feel like wearing a 100-pound backpack in the vertical dimension.

Your ultimate running speed then depends on how strong you are. That 100 pound "backpack" will push you into the ground and give you far more acceleration than your normal weight would allow: it will feel like you have ultra-traction. But when you push to the side and accelerate your body, you're only accelerating your normal body weight.

Marathon times will likely suffer, but perhaps some short sprints will be faster in gravity over 1g.

[crystaln]

Exactly, although inertia might be more correct, particularly for the horizontal dimension.

More gravity, to a point, will increase running speed. Would be interesting for someone to calculate the optimal gravity for running.

[ForHackernews]

Who cares about sprinting, I can't wait for the lunar pole vault.

[jimmcslim]

Olympics on the Moon? Maybe in 2020 according to one futurist of the past...

http://usbornepublishing.tumblr.com/post/60362087283/it-is-t...

(Scroll to the end specifically for the Olympics.)

[agumonkey]

In my amateur runner mind, that's where I spend the most time on technique. Balancing the effort waves ensuring everything goes forward and not up nor down. Faster means inertia, means lighter if not done appropriately, which require to tweak your approach.

[furyg3]

is the solution stairs?

It would be interesting if you could achieve a faster speed on the moon running up a flight of stairs than running on a level lunar surface.

Alternatively you could 'angle' the stairs on a level surface (think saw-tooth pattern) and translate that upward energy into forward energy.