say he’s racing Superman around the world - what is keeping him on the ground? superpowers, magic or plain physics? just wondering.
Aura-of-all-trades, probably.
Gravity. Same as you.
I don’t think it’s been addressed. The issues of heat shielding and metabolism have been addressed but I don’t recall ‘staying on the ground’ ever having been an issue. I think the answer is 1) It’s a comic book 2) There’s more involved in his speed than simply being able to apply a larger force to his movement, there’s the ‘speed force’ which I would guess makes him fast without special strength or leaping power 3) Even were his speed due to great forces, presumably he could keep lateral by running at an angle closer to the ground or just adjusting his running style in terms of how hit feet hit the ground to keep the vertical component of his force to the minimum. Cars can go very very fast without leaving the ground at all.
Chuck Norris.
Nope; if that was true, the moment he hit a slight rise he’d go shooting off into the air like he was launched from a cannon. Nor would he be able to stop very fast or turn corners well; like most speedsters, he acts like he has selectively sticky feet when he is running.
He creates his own quantum gravity through hyper-ion speed.
Current Flash taps an energy existing in the DC universe called the, well, the Speed Force. Yeah, like gravity or electromagnetism, but for speed. I know.
And of course it has its own properties, mostly whatever the writer using the concept at the moment decides they are.
One could theorize something like that he’s not moving fast, time is simply travelling different for him.
Gecko boots.
Actually, though I’m not a huge Flash authority, it seems a bit more like his powers enable him to accelerate in whatever direction he chooses to, without needing to cause an equal and opposite reaction - if he wants to go back to the ground, he just speeds that way.
it’s very simple, he just – oh Look! A squirrel!
Of course, when you combine Superman and The Flash, they can’t help but go flying off into space. Have a look at the cover of Action Comics #314 (July 1964) “The Day Superman Became the Flash”
http://www.wonderland-site.com/html/comix/comics04-01.htm
http://www.dialbforblog.com/archives/306/
I’m not a physics expert, but I don’t think that would make a difference. In fact, relativity would suggest time* is *different for him - he really is experiencing less of it than we are. But he’d still fly off the earth when cresting a hill.
What I’ve always wondered is why it’s never occurred to him to try flying - not like Superman, who just jumps and then is magically propulsed - but like a swimmer. I’d think doing an underwater stroke motion should allow him to ‘swim’ up into the air when desired.
No. Falling is a problem for the Flash. If he could accelerate in any direction he chose, he would be able to fly.
The Flash’s speed force connection / aura does cause him to interact with the world around him in unexpected ways. He can vibrate through solid objects, he can run at several times the speed of sound without disrupting the area around him, et cetera. However, there seems to be an ability to shut off some of that when he wants to - normally he doesn’t cause air disruptions when moving, but when he so chooses, he can.
The second Reverse Flash’s powers were specifically different from the Flash’s - instead of running fast with a speed force connection, he actually had a distorted relationship with time. His supersonic running DID cause disruptions.
He saved 15% on them, in just 15 minutes. 
He has done that at various times, though it’s more of a treading water-style stroke (or else he uses his hands to create a whirlwindy thing that pushes him up off the ground).
Is it ever actually established just how fast he is? In current continuity, I mean, not Golden Age where everything went up to 11. Because if he can circle the world in less than an hour and a half, then gravity wouldn’t keep him on the ground.
I believe that in current continuity, he can closely approach light speed, but rarely does so. (He doesn’t want to pull a Barry.) He also refrains from using some of his other abilities most of the time, because they’re too destructive. That was definitely the case in the Justice League Unlimited series, at least–I’m not up on the comic books.
Barry, Wally, and (theoretically) Bart are all capable of light speed, at which point they risk being absorbed into the Speed Force and often start careening through time.
Jay and Max are slower, due to age primarily, though Jay’s never demonstrated an ability to approach light speed to my knowledge. Jesse Quick supposedly tops out at about one half of light speed.
so… that means at that speed, there’s no way he would be able to stay on the ground, unless it was some magical property of the Speed Force. or, to put it another way, there’s no way Superman could have kept up with the Flash unless he cheats. (by flying towards the earth, keeping himself from taking off)
does that make sense?