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-   -   Gymnastics on the Moon (http://boards.straightdope.com/sdmb/showthread.php?t=801038)

Leo Bloom 08-11-2016 09:16 AM

Gymnastics on the Moon
 
Olympics prompted. Gymnastics on the Moon would be awesome, and all sorts of new maneuvers, eg "the 1/2 Bloom," which is too difficult too describe here. But to begin, my original thought/query. There are any number of maneuvers--I don't know the real word--often named after their creator, which are analyzed as, eg ["two flips with planked body"] followed by ["two spins around body axis"], etc. I'm using brackets because the technical description is very precise and I don't know the words anyway.

Basic physics question: can you extrapolate using elementary dynamics how a maneuver on Earth would play out in a different gravity, all other things being equal?

I.e., would a "triple Bloom" on earth be a "36-Bloom" on the moon?


ETA: Mods, if you can, leave this in this GQ forum. It should be the physics and physiology of a hypothetical, not a Fantasy Sport.

TriPolar 08-11-2016 09:30 AM

Sticking the landing will be a lot easier on the legs.

watchwolf49 08-11-2016 09:54 AM

I've fallen and can't get back up ... YouTube video of astronaut on Moon.

markn+ 08-11-2016 09:55 AM

Less stressful on the legs perhaps, but harder to achieve. You'd tend to bounce more, I'd think.

--Mark

muttrox 08-11-2016 10:19 AM

All else being equal, I believe gravity is roughly 1/6 - the same muscle power gets you proportionally more height and time in the air to do stuff.

Marvin the Martian 08-11-2016 12:13 PM

Quote:

Originally Posted by TriPolar (Post 19545884)
Sticking the landing will be a lot easier on the legs.

If you apply the same upward force when you jump as you would on Earth, you will still need to apply the same amount of force to stop your body when you land. You'll just jump higher.

muttrox 08-11-2016 12:17 PM

But impact may be spread over more time. Your muscles have more time to absorb the equivalent change in force. Er... actually I think the work is equal, so you need to apply less force over more time. If I remember my physics correctly.

scr4 08-11-2016 12:20 PM

Quote:

Originally Posted by muttrox (Post 19546422)
But impact may be spread over more time. Your muscles have more time to absorb the equivalent change in force.

No, if you take off with the same amount of force, then you leave the ground at the same speed, regardless of gravity. It's just a function of force and mass. Gravity only affects how quickly you decelerate after leaving the ground, which affects how high you get, and how soon you come back down. When you do come down, you hit the ground at the same speed.

Bryan Ekers 08-11-2016 12:29 PM

Well, if you jump like a figure skater with your arms and legs held far out and then pull your limbs in quickly to convert angular momentum to rotational, I guess the extra "hang time" might allow for a septuple+ axel.

Probably the bigger problem is how to maintain athletic conditioning in a low-gee environment. Even if you start out as an Olympian, the longer you stay on the moon, the "softer" you'll get. Would it be possible to stay in Olympic shape even with extended hours of daily resistance training? The cooler impossible-on-Earth gymnastic moves might only be doable for a few months.

muttrox 08-11-2016 12:40 PM

Thanks scr4. Wasn't thinking right.

Bryan Ekers 08-11-2016 12:49 PM

Quote:

Originally Posted by muttrox (Post 19546491)
Thanks scr4. Wasn't thinking right.

Well, there's the minor wrinkle of terminal velocity. As pointed out in this long-ago thread, the moon doesn't have terminal velocity as such since it has no atmosphere, but if we're staging a Moonlympics in a stadium-sized dome with Earth-level air pressure so the athletes won't have to wear bulky spacesuits...

Well, probably there's no appreciable effect anyway. I just picture a pole-vaulter able to land without a mat by flapping his arms after he clears the bar.

TriPolar 08-11-2016 01:03 PM

Quote:

Originally Posted by scr4 (Post 19546431)
No, if you take off with the same amount of force, then you leave the ground at the same speed, regardless of gravity. It's just a function of force and mass. Gravity only affects how quickly you decelerate after leaving the ground, which affects how high you get, and how soon you come back down. When you do come down, you hit the ground at the same speed.

Yes, but isn't there less impact on the legs? That's what I was talking about, fewer injuries.

scr4 08-11-2016 02:36 PM

Quote:

Originally Posted by TriPolar (Post 19546552)
Yes, but isn't there less impact on the legs? That's what I was talking about, fewer injuries.

If you jump up from the floor with the same amount of effort, then you come back down just as fast on the Moon as on the Earth. So the stress on your legs from landing should be the same.

Or to put it another way - on the Moon, you can jump 6 times higher, so you're falling from a height 6 times higher.

TriPolar 08-11-2016 02:45 PM

Quote:

Originally Posted by scr4 (Post 19546870)
If you jump up from the floor with the same amount of effort, then you come back down just as fast on the Moon as on the Earth. So the stress on your legs from landing should be the same.

Or to put it another way - on the Moon, you can jump 6 times higher, so you're falling from a height 6 times higher.

Ok, but you don't have to jump as high to start with on the moon. On earth it's hard to stick a landing for the minimal moves. On the moon you can do much more without coming down so hard. So yeah, if you take advantage of maximum height for the most complex moves then I guess you'll hit just as hard.

Blue Blistering Barnacle 08-11-2016 03:24 PM

Quote:

Originally Posted by TriPolar (Post 19546907)
Ok, but you don't have to jump as high to start with on the moon. On earth it's hard to stick a landing for the minimal moves. On the moon you can do much more without coming down so hard. So yeah, if you take advantage of maximum height for the most complex moves then I guess you'll hit just as hard.

If you play it conservatively like that, you may stick more landings, but you'll lose out overall in points to my YUGE aerial stunts.

Well maybe not; there may be a point where the landings become impossible to stick (due to bounce) and where landing failures lose more points than extra turns gain.

scr4 08-11-2016 03:32 PM

Quote:

Originally Posted by TriPolar (Post 19546907)
Ok, but you don't have to jump as high to start with on the moon.

True. My implicit assumption was an athlete jumping up as hard as he/she could in either environment. But gymnastics is not a jump height competition.

eburacum45 08-11-2016 04:08 PM

One problem I can foresee with the Moon Olympics (inside a pressurised arena, of course) is that for the same effort you jump higher and longer, but still land with the same force. During this long ballistic curve you will have plenty of time to do somersaults, tumble, and do impressive manoeuvres of that kind; in fact they would be unavoidable. Mis-time your tumble and you could land on your head, or your neck.

Long jump and high jump would share many characteristics with competitive gymnastics, and you'd get extra points for landing gracefully without breaking your ankle or neck. Remember that your inertia remains the same on the moon, despite weighing much less.

Some Call Me... Tim 08-11-2016 05:11 PM

It's true that inertia is the same and you'd land with the same force, if anything perhaps slightly slower as there'd be more distance for air friction to slow you down. Presumably the dangers of a botched landing would be roughly equivalent to the Earthly dangers, though again if anything it'd be slightly safer as you'd have more time to react during flight time to minimize those risks that might arise from a botched start.

So, if anything the odds of breaking your head or neck would be somewhat less than when doing the equivalent sport on Earth... and here such things are quite rare in sport.

Bryan Ekers 08-11-2016 05:18 PM

Quote:

Originally Posted by eburacum45 (Post 19547171)
One problem I can foresee with the Moon Olympics (inside a pressurised arena, of course)

I think the javelin throw might have to be foregone.

joema 08-11-2016 05:45 PM

It's not on the moon, but in this video Apollo astronaut Alan Bean does gymnastics in zero-g on Skylab. From about 1:05 to 1:13 he is twisting pretty fast. He was a gymnast in college:

https://www.youtube.com/watch?v=dmnmuTv4pGE

This cannot be done on the International Space Station since it doesn't have a large unobstructed habitable volume. The total habitable volume on Skylab was 12,500 cubic feet, whereas ISS is 13,696 cubic feet (both excluding spacecraft), but ISS is divided into many small compartments.

The above video is probably the only low-g or zero-g gymnastics anyone will see until a large habitat is built in space or on the moon.

Chronos 08-11-2016 05:46 PM

Picture an athlete six times stronger than a normal human. Train them in gymnastics, and have them do their best in an Earthly gymnasium. Then slow down the film by a factor of sqrt(6). That's exactly what a normal gymnast would look like on the Moon.

EDIT: Whoa, the two space stations are that close in volume? I'd have expected that the ISS would be several times larger than Skylab, not just a hair more.

engineer_comp_geek 08-11-2016 06:07 PM

One thing the astronauts discovered on the moon was that while things like jumping up were pretty straightforward (you just end up jumping about 6 times as high, as was already mentioned), other things weren't so straightforward. Walking, running, and other motions rely on a certain amount of friction between you and the surface you are on, and the moon's reduced gravity reduces the friction as well. So if you try to run, all you end up doing is slipping your feet. As a result, the astronauts found that the easiest way to move across the lunar surface was to bunny hop.

If they tried to do a normal 100 yard dash on the moon, it would end up as a rather comical event of athletes cartoonishly running with their feet slipping on the surface while barely moving forward. A lot of other typical earth-based sports would be similarly affected.

Dr. Strangelove 08-11-2016 06:10 PM

The outer diameter of SkyLab was 6.6 m, as compared to ~4.5 m for most ISS modules, but it's pretty clear that a huge fraction of the ISS volume is taken by non-habitable space, whereas much of SkyLab (in particular, the ring shown above) gets almost the full diameter. Wouldn't surprise me if the effective diameters were something like 2 m vs. 6 m. That factor of 9 makes up for a lot of missing length.

Hail Ants 08-11-2016 06:58 PM

Quote:

Originally Posted by engineer_comp_geek (Post 19547484)
One thing the astronauts discovered on the moon was that while things like jumping up were pretty straightforward (you just end up jumping about 6 times as high, as was already mentioned), other things weren't so straightforward. Walking, running, and other motions rely on a certain amount of friction between you and the surface you are on, and the moon's reduced gravity reduces the friction as well. So if you try to run, all you end up doing is slipping your feet. As a result, the astronauts found that the easiest way to move across the lunar surface was to bunny hop.

Along with allowing zero-G simulation the 'vomit comet' could alter its parabolic course and instead simulate the 1/6 gravity of the Moon as well. I can't find the footage of it but I've seen film of the Apollo astronauts wearing their lunar surface suits and practicing walking and moving around inside the plane (on a simulated lunar surface) in just this manner.

Blue Blistering Barnacle 08-11-2016 07:47 PM

Quote:

Originally Posted by Hail Ants (Post 19547601)
Along with allowing zero-G simulation the 'vomit comet' could alter its parabolic course and instead simulate the 1/6 gravity of the Moon as well. I can't find the footage of it but I've seen film of the Apollo astronauts wearing their lunar surface suits and practicing walking and moving around inside the plane (on a simulated lunar surface) in just this manner.

They did that on MythBusters, too.

markn+ 08-16-2016 05:52 PM

Randall Munroe did an article on lunar swimming, in which he concludes, among other awesome results, that Michael Phelps could probably jump out of a pool on the Moon 2 to 3 meters into the air, and a champion finswimmer could reach 4 to 5 meters.

--Mark

Melbourne 08-17-2016 06:20 AM

Quote:

Originally Posted by engineer_comp_geek (Post 19547484)
If they tried to do a normal 100 yard dash on the moon, it would end up as a rather comical event of athletes cartoonishly running with their feet slipping on the surface while barely moving forward. A lot of other typical earth-based sports would be similarly affected.

Boxing. Either they'd adjust to the lack of friction by letting their feet slide, or they'd change their action to get an equal-and-oposite effect (backwards kick? Running roundhouse?). Also, they could lean in and out a lot farther! It would be a whole new discipline.

(Ok, actually they'd probably just put on sticky shoes or roughen the ring floor)


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