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#1
08-11-2016, 09:16 AM
 Leo Bloom Member Join Date: Jun 2009 Location: Here Posts: 11,814
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.

Last edited by Leo Bloom; 08-11-2016 at 09:19 AM.
#2
08-11-2016, 09:30 AM
 TriPolar Guest Join Date: Oct 2007 Location: rhode island Posts: 38,138
Sticking the landing will be a lot easier on the legs.
#3
08-11-2016, 09:55 AM
 markn+ Guest Join Date: Feb 2015 Location: unknown; Speed: exactly 0 Posts: 1,240
Less stressful on the legs perhaps, but harder to achieve. You'd tend to bounce more, I'd think.

--Mark
#4
08-11-2016, 12:13 PM
 Marvin the Martian Member Join Date: Jun 2015 Location: Phoenix, AZ, USA Posts: 747
Quote:
 Originally Posted by TriPolar 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.
#5
08-11-2016, 09:54 AM
 watchwolf49 Guest Join Date: Dec 2009 Location: State of Jefferson Posts: 8,071
I've fallen and can't get back up ... YouTube video of astronaut on Moon.
#6
08-11-2016, 10:19 AM
 muttrox Member Join Date: Dec 2000 Posts: 2,107
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.
#7
08-11-2016, 12:17 PM
 muttrox Member Join Date: Dec 2000 Posts: 2,107
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.
#8
08-11-2016, 12:20 PM
 scr4 Member Join Date: Aug 1999 Location: Alabama Posts: 14,232
Quote:
 Originally Posted by muttrox 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.

Last edited by scr4; 08-11-2016 at 12:20 PM.
#9
08-11-2016, 01:03 PM
 TriPolar Guest Join Date: Oct 2007 Location: rhode island Posts: 38,138
Quote:
 Originally Posted by scr4 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.
#10
08-11-2016, 02:36 PM
 scr4 Member Join Date: Aug 1999 Location: Alabama Posts: 14,232
Quote:
 Originally Posted by TriPolar 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.

Last edited by scr4; 08-11-2016 at 02:40 PM.
#11
08-11-2016, 02:45 PM
 TriPolar Guest Join Date: Oct 2007 Location: rhode island Posts: 38,138
Quote:
 Originally Posted by scr4 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.
#12
08-11-2016, 12:29 PM
 Bryan Ekers Guest Join Date: Nov 2000 Location: Montreal, QC Posts: 56,667
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.
#13
08-11-2016, 12:40 PM
 muttrox Member Join Date: Dec 2000 Posts: 2,107
Thanks scr4. Wasn't thinking right.
#14
08-11-2016, 12:49 PM
 Bryan Ekers Guest Join Date: Nov 2000 Location: Montreal, QC Posts: 56,667
Quote:
 Originally Posted by muttrox 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.
#15
08-11-2016, 05:46 PM
 Chronos Charter Member Moderator Join Date: Jan 2000 Location: The Land of Cleves Posts: 75,217
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.

Last edited by Chronos; 08-11-2016 at 05:47 PM.
#16
08-11-2016, 06:07 PM
 engineer_comp_geek Robot Mod in Beta Testing Moderator Join Date: Mar 2001 Location: Pennsylvania Posts: 20,603
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.
#17
08-11-2016, 06:58 PM
 Hail Ants BANNED Join Date: Jan 2000 Location: NY USA Posts: 7,635
Quote:
 Originally Posted by engineer_comp_geek 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.
#18
08-11-2016, 07:47 PM
 Blue Blistering Barnacle Guest Join Date: Dec 2011 Posts: 5,350
Quote:
 Originally Posted by Hail Ants 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.
#19
08-16-2016, 05:52 PM
 markn+ Guest Join Date: Feb 2015 Location: unknown; Speed: exactly 0 Posts: 1,240
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
#20
08-17-2016, 06:20 AM
 Melbourne Guest Join Date: Nov 2009 Posts: 3,463
Quote:
 Originally Posted by engineer_comp_geek 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)
#21
08-11-2016, 06:10 PM
 Dr. Strangelove Guest Join Date: Dec 2010 Posts: 6,389
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.

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