The interesting thing about distance runners is that they appear to be engaged in somewhat of a fast jog or slow run, whereas in actuality they're going a lot faster than that. So the natural tendency for TV viewers is to observe these amazing athletes loping along and then figure, "OK, I can do that. No problem."

There's the disconnect between what these athletes appear to be doing versus what they're actually doing. They appear to be jogging, but are actually running somewhere between 11-12 mph, which is no jog. How is this possible? It's a remarkable optical illusion.

To illustrate how fast 12 mph really is, all one has to do is get on a treadmill and dial in the number. Lots of people might be able to hang in there for a little bit, but it's very apparent to nearly all that this speed feels more like a sprint. For others, there's the horrifying realization that they'll get thrown off the back of the machine unless they quickly back down to something manageable. Either way, everyone marvels at how this pace can be maintained for an entire marathon by elite runners.

In a "60 Minutes" segment that aired a couple of Sundays ago, Anderson Cooper (age 46) wondered if he could beat distance runner Shalane Flanagan in a quarter mile race, under the stipulation that Flanagan limit herself to the pace that she'd normally run in a marathon. Cooper leapt out front at the start, but Flanagan soon pulled even with him, and when they were side-by-side their technique differences were very apparent and the illusion of the marathon runner clarified.

There she was leaping along like a gazelle, long and graceful with a relatively low frequency of strides, while Cooper appeared to be sprinting like a hamster on a wheel, puffing away with a lot of short strides and getting nowhere. Needless to say, he got clobbered; as would the rest of us, captured by the illusion these great runners manage to create.

Never a really devoted runner, I nonetheless jogged a fair amount back in the day and somewhere in my early twenties asked my grandfather to time me on a mile route. The first half mile was a medium fast pace and on the last half I gave it about all I had. Time: 5 minutes and 5 seconds. Not bad - for one mile - but I was spent. Even if I were to run at that pace for 26.22 miles (the length of a marathon), it would still have been about 10 minutes slower than the world record time for men.

***

I meant to include a detail in last week's column on Hearst Castle, and that would be the loud noise of the sound barrier being broken. No big deal, but when I looked up in the clear blue sky there was nothing there - no airplane, no vapor trail, no nada. And yet the sound lingered a little longer than a typical sound barrier shock wave and had more of a shattering quality to it.

It was only later that we learned of small earthquakes in the area. We felt nothing and could only imagine what larger quakes must sound like relative to the minor activity taking place around us. Imagining is good - particularly when it comes to earthquakes.

We later drove through the Silicon Valley and tried to soak up some of the latest in technology. Before arriving in San Francisco, we had gotten the word about a new gadget out there called a Nomad which is a small (key ring or credit card-sized) device designed to take the place of USB cords. The Nomad home office, located at the foot of Chinatown as it spills onto Broadway, seemed to be in a perfect location, until we saw signs out for Larry Flynt's Hustler Club, the Garden of Eden, Sweet Dick's, and so forth.

Not to worry, we went inside a door labeled "539" and found a small and happily staffed office comprised of 10-12 young people who were thrilled to have people from as far away as South Carolina checking out their product - so much so that the owner, a young man named Noah, comped us a couple of freebies.

So thanks, Noah, and good luck!

Edward M. Gilbreth is a Charleston physician. Reach him at edwardgilbreth@

comcast.net.