There are small animals that can run across the surface of liquid water. I have heard people say that if we ran at some insanely high speed(I’ve heard both 70 and 200 mph) , we could do it too. Is there s hypothetical speed where this would happen? No, it doesn’t count if the water is frozen.
Yes, theoretically, if humans were capable of running fast enough, they could run across the surface of water.
There are videos you can find showing people running across the surface of a pool filled with water and cornstarch. If they simply try to walk across, they sink and it behaves as a liquid.
Humans have a much higher weight than small animals, and it has to do with the ratio of surface area touching the water to the amount of weight pushing down.
[QUOTE=Popular Mechanics]
Jamaican runner Usain Bolt, the current world record holder for the 100-meter sprint, ran 10.4 meters per second. But J.W. Glasheen and T.A. McMahon, two Harvard biologists who studied how the basilisk runs on water, found that in order to mimic the lizard, a human would need to run at almost 30 meters per second, “a velocity beyond human ability.” A man would also need “an average power output almost 15 times greater than the maximum sustained power output for humans.”
[/QUOTE]
More info in the complete article here:
Some Italian researchers calculated that a 145 pound person would have to run 67 miles per hour to be able to run across water—that’s 15 times the force human legs are capable of producing.
(long boring complicated article here: Humans Running in Place on Water at Simulated Reduced Gravity )
In this video, skilled athletes with special shoes are actually able to run across the surface of water over a short distance (kind of).
edit: that video was later admitted to be a hoax
It was also the subject of a Mythbusters episode. They concluded that there was a solid platform just under the surface of the water.
If I’m not mistaken, humans are simply too heavy, and their feet surface area too small. The basilisk lizard is light and has big feet.
This has nothing to do with the water and everything to do with the cornstarch.
This is a fluid that changes its viscosity when the forces on it change. Smack it, and it gets hard.
…
Sorry, that sounded dirty.
I think that only means that humans can’t do it at the same speed or energy expenditure as the basilisk lizard - the only question is whether ramping up the speed (i.e. a theoretical superhuman) would mean that some other limiting factor comes into play.
I don’t know, a lizard weights a few ounces, them big paddle feet need only generate a few ounces of lift. Humans with stubs on the end of their legs need to produce well over a hundred pounds of lift. There would be a little lift, very little.
So, let’s look at the OP from the other direction. If we had no lift from the footfalls, then a human would have to be traveling at around 17,000 mph to run across the water. However, with a little lift then the human could travel a little slower, say 16,975 mph. That’s as close to a ballistic trajectory as to make no difference.
Where are you getting those numbers from?
It’s possible to waterski barefoot at survivable velocities. I realise waterskiing is a different thing from running on water, but waterskiing is about lift generated from the interaction of human feet and the surface of the water - and is possible at speeds that are several orders of magnitude smaller than you’re talking about.
If you have to be moving really fast to travel across the top of the water are you actually running on the water? Or are you just being propelled by your previous momentum?
You’ve seen the lizard run on the water, right? It really does run on the water.
Fairly recent thread on topic: http://boards.straightdope.com/sdmb/showthread.php?t=784722
That’s the orbital speed … a tongue-in-cheek joke meaning humans can’t run on water pre se.
We’re using the foot as a hydrofoil to generate the lift … no doubt … but that’s not “footfalls” as I had specified. This is all original research I did at the lake yesterday afternoon, at no time or under any circumstance was I able to put my foot down on water and then lift it back out without touching bottom or totally crashing into the water.
Then them brat kids started throwing big sticks out into the lake and experiment quickly ended … [sigh]
It becomes a confusing joke when others have already presented calculations for an actual (if physiologically impossible) speed at which something with the outer dimensions of a human body would run on water. Which was what the OP asked about.
Jesus and Peter walked on water, well the latter only till he got scared.
Are we talking flat, quiet water or active water like in the oceans with the big waves?
With the waves one would need to step on each one which would be a trip hazard.
The only calculations I see are for conditions of 20% gravity … is that what the OP asked?
Fine, the actual calculations aren’t available in the two links and Zach29 fails to notice the Italians are only referencing other work and are answering a totally different question. That totally invalidates post 3 and 4 quoting the 30 m/s estimate of Glasheen and McMahon.