In <
[email protected]>,
[email protected] opined:
> I notice that no one has yet reported seeing an elliptical oil ring on the road, which confirms my
> notion that bicyclists do not see what they are looking at, as with getting flats.
It's true that no one has reported seeing an elliptical oil ring, but people do report seeing many
other more interesting things of similar scale on the road, so I don't think this example confirms
your notion very well. It could still be a true notion, but you can't prove it this way.
Oil droplets of various descriptions are found by the tens of thousands per block in cities, yet all
of them fall into a general category of non-hazardous and inconsequential road features, and even if
they're noticed there's no reason to remember any particular shape or pattern.
And I'm not sure how you mean "as with getting flats" -- they don't notice that they HAVE flats,
they don't notice things that MIGHT cause flats, or they don't notice what DID cause a particular
flat? Or something else?
> How about looking for them on 20-30mph mountain roads the next time you go for a ride.
I couldn't wait until I could go to the mountains so I (man, I have SO GOT TO FIND A JOB!) went
outside to look at my 20-30 mph city street in Washington DC. This is different from what was
suggested, so maybe my observations aren't significant in this context, but until I understand
better I'll assume that what I saw is essentially similar to what I would find on a mountain road.
The street I looked at had an additional advantage in that it's a one-way street that hasn't been
molested by a street sweeper for many years. It also has a 5 ft. wide bike lane on one side.
http://www.mindspring.com/~darsal/droplets/overview.jpg (61kb JPEG)
At first I noticed a lot of oil drops, ranging in size from a few mm up to a couple hundred mm. I
saw a lot of different shapes too, from very circular to long and roughly elliptical, and even a few
linear and irregular ones. As expected, there appeared to be more drops in the center of the road
and fewer at the edges.
A common and unexpected shape is one I'd describe as a half-ellipse, with an elongated part pointing
to where the traffic approaches and a more rounded part where the traffic goes. I suppose that when
a drop first contacts the pavement it is moving fast enough to elongate, but once a lot of the drop
has landed there are other factors that make the rest of it less elongated.
http://www.mindspring.com/~darsal/droplets/half-ellipse.jpg (61kb JPG)
Anyway...
I walked a block before I found a single clearly visible elliptical ring. Only one ring in a heavily
travelled block, so I was ready to dismiss the whole phenomenon as a rarity and use that to explain
why nobody reports seeing them. But I wasn't really satisfied that I had looked well enough, as this
particular block has a stop light so a lot of the traffic isn't moving normally.
So I walked another half block in the other direction. By the time I got to where I took the
overview picture above I had lost count of the elliptical rings I spotted, but the number was over a
couple dozen. In fact, there's one near the exact middle of the overview picture. Here's a purely
optical telephoto version from the same perspective:
http://www.mindspring.com/~darsal/droplets/ell1-med.jpg (39kb JPEG)
And here's a closeup, including my toes to provide a rough scale, from a much closer position. I was
standing perpendicular to the roadway, and traffic approaches from the left in this shot:
http://www.mindspring.com/~darsal/droplets/ell1-close.jpg (63kb JPEG)
Notice that the ring is ragged and somewhat obscured by other droplets. It wasn't very obvious while
I was walking and looking for it the first time, and even once I knew it was there I had to look
closely to find it a second time - thank goodness it held its pose for my picture.
Here's a family shot of at least four elliptical rings, to show a range of appearances. These are of
similar scale as the one above.
!! This is a LARGE FILE !!:
http://www.mindspring.com/~darsal/droplets/family.jpg (692 kb JPEG)
I don't know if these would register to my brain unless I was actively looking for them. I'll keep
my eyes open on my rides this afternoon both for these known ones and for others I don't expect, and
I bet I'll see more now than I ever did before, but I'll still miss more of them than I see.
But most significantly (to the discussion of how observant most cyclists are at least) the rings I
found were smack dab in the middle of the road. This is a place I don't casually go. If I am riding
there, I am certain to pay more attention to traffic than to inconsequential things like the shapes
of common oil spots on the road. Heck, even if they were rings of bright green paint I'm not sure
I'd notice their shapes and live to tell about it...
And how did these get there in the first place? I'm still a bit stumped. I remember that an ellipse
is a 2D representation of a 4D sphere, but that doesn't account for the ellipse being a ring -- it
would be filled, with the inner border of the ring perhaps being a bit fuzzy. I'm now leaning toward
a spherical water droplet coated in oil but with the water rupturing through the bottom at impact?
--
Dave Salovesh
[email protected]
