By The Running Muse, Nov 29 2014 01:28PM
'I believe that every human has a finite number of heartbeats. I don't intend to waste any of mine running around doing exercise', said the man whose pulse rate more than doubled when taking one small step - Apollo 11 commander Neil Armstrong. He may have been the first to walk on the moon, but he clearly had no intention of being the first to run there.
That honour would fall to one of the two astronauts exploring the moon's surface during the next mission, Apollo 12's Pete Conrad and Alan Bean, both of whom found running to be a more efficient way to 'walk' in one-sixth gravity. Neither remembers which one ran first, however, and hardly any video footage of their lunar excursions exists, because Mr. Bean had apparently pointed the colour TV camera at the sun and damaged its sensor.
Since they were running extraterrestrially across one of the biggest craters in the solar system, an actual image would've made all those stunning Rave Run pictures in Runner's World look rather.....well, pedestrian. Fortunately, fascinating footage does exist of lunar running from the last time humans wandered there, as we'll see.
Bean also managed to leave several rolls of photographic film behind on the moon surface, which may be why he took to representing this and other missions in paint on his return. Below is his 'Fast Times on the Ocean of Storms', a self-portrait in acrylic and Moon dust. Yep, real Moon dust. Note that both feet are off the ground.
Walking is essentially controlled falling. As the body moves forwards and its centre of gravity vaults over the stiff front leg, the back ankle pushes off towards the front and the fall is arrested. Crucially, this involves a certain amount of bobbing up and down - in energy terms, potential energy converts to kinetic energy and back again, with energy being added by the muscles at push-off.
Running involves timing this so that the back leg leaves the ground before the forwards one has landed, i.e., both feet are off the ground at some point. This criterion is used to distinguish walking from running in competitive sport as well as in the dictionary. As the speed of walking increases, it becomes more economical to run in terms of the energy required, and thus in terms of oxygen consumption, the 'locomotive breath', so to speak.
Things feel a bit different when gravity is reduced and there is no atmosphere, though. To illustrate this, we'll take a topical case where the force of gravity is several hundred thousand times weaker than on earth. Here's how one commentator on today's astonishing Rosetta landing on Comet 67P explained what walking on its surface would be like: 'Step (carefully). Hurl through space. Flail. Slowly arc towards comet. Land. Bounce. Skid. (Repeat).'
Bean's lunar running experience also felt unfamiliar, albeit to a lesser degree: 'I was light on my feet, much as I expected. When I pushed off with one foot, there was a long pause before I landed on the other foot, like running in slow motion. I could feel my muscles completely relax as I glided along to the next stop. I seemed to float just above the surface.......I felt I must look like a gazelle, leaping long distances with each bound. I looked over at my partner........he was space-borne for a long time, but, to my surprise, he wasn't rising very high or leaping very far at all. Then I realised that in the moon's light gravity we did not have the traction to push hard backwards with our boots. I wasn't leaping like a gazelle - it only felt that way.'
The frictional forces that give traction are proportional to weight and would thus be reduced, especially on a dusty surface. Although our weight is less on the moon, our mass, inertia and momentum are the same as on earth - add the 'long pause' waiting for the leg to land, which takes six times as long, as well as the cumbersome, pressurised spacesuits which have water sloshing around their inner layers for cooling, and you can imagine how the actions we are used to taking on earth could lead to problems maintaining stability, stopping, turning, going downhill, etc..
Apollo 17 astronauts Gene Cernan and Harrison Schmitt were not only running on the moon, but were actually comparing two different running styles - loping (as in the above clip) and bunny-hopping (see below). 'Loping's the only way to go', says Schmitt, the cameraman.
Now I'm no fan of the treadmill, but in this next fascinating clip, astronaut Karen Nyberg shows us how she runs in zero gravity on the International Space Station, where the astronauts have to exercise daily because of the effects that the absence of gravity has on muscle mass and bone density. The treadmill has to be set on a vibration isolation system, otherwise unwanted loads are imparted to the whole space station.
I'm reminded of one of Mr. Christie's tortuous applied maths questions at school, which asked us to consider the forces acting on someone standing on a board on a ball of ice in a lift suspended by a spring in a moving capsule in earth orbit, and then calculate the overall resultant force - 'if any', as he put it.
That isn't quite as fanciful as it sounds: research experiments published in 2007 in Acta Astronautica investigated the optimum gait for moonwalking in one-sixth gravity by suspending spacesuit-clad walkers from a spring. Their results showed that bending your knee was indeed harder in a pressurised suit, but because its springiness tended to straighten it again, much of the energy put in to each step was recovered.
This finding led to a counterintuitive conclusion that confirmed the empirical reports of the Apollo astronauts: if your oxygen supply is low while strolling around in a spacesuit, you should run back to your base, not walk, because the extra springiness of running means a higher percentage of the energy used per unit distance is recovered.
Anyway, here's Karen of the vertical hair: note her strange running form, leaning back. In weightless conditions, she does not need to manage her centre of gravity into the usual earth position - her form is determined by the harness that keeps her perpendicular to the treadmill.
A dozen men have walked on the moon, and some even went backwards, using a kind of reverse shuffle, but most of them were running at some point. Within a few years, Police were singing 'feet, they hardly touch the ground, walking on the moon', and Michael Jackson was moonwalking backwards himself, rather more elegantly than Neil Armstrong was in first stepping on to the moon.
But here's a thought for those of you who may be taking part in the MoonWalk night marathons now happening annually in London and Edinburgh: you'd be doing well if you can move faster than those 12 men, relative to the earth - they were travelling at one kilometre per second.
Those first lunar footprints are still there, preserved by the stillness. Back on earth, a quarter of a million miles away and four million years before, some of the first footprints of our bipedal ancestors were made in volcanic ash, and they too are preserved on a Tanzanian sandbar at Laetoli. Next week we will be looking at the first human runners, but for now I'll leave you to meditate on these pictures......