Monday, August 25, 2014

A curious traffic accident

Sunday, a day of playing e.g. with my 5-year-old nephew and niece, was probably more likely a day than Monday for such an injury. But I classified an event in which I was injured an hour ago to be a traffic accident.

A curious one, indeed. Some people who drive cars or bikes hit other cars. In 1999, a friend of mine from Prague and Rutgers, mathematician Petr Čížek, was killed by a truck that they had crashed into while his lively Russian female friend was driving on a seemingly empty road in Minnesota (I didn't go to that expedition, mostly due to the qualifying exams).

The underpass going to the soccer stadium after a fan association named Ultraside gave a permission to itself to paint it. ;-) It used to be prettier than at random moments – the city hall should have hired them to paint the underpass regularly.

People may collide with other people of different occupations and races. The individual I hit an hour ago was a boxer. And it's a race, not an occupation. ;-) Well, I know that the native speakers actually call it a "breed", not a "race", but I will use the word "race" because it's the same concept as the human races, isn't it (well, except that the separation to breeds was mostly bred i.e. man-made), and I am Czech who has never attended any dog races so there is no room for confusions.

I was just leaving an underpass for the pedestrians and bikes near the stadium of FC Viktoria Pilsen, our recently famous but no longer shining soccer club, which you may see on the picture at the top (I was moving to the right side on that picture; the decoration of the underpass is frequently changing). More or less all of Czechia is accessible via Street View on Google Maps (unlike Germans and many other nations, we're in no way oversensitive concerning the privacy on the web), so you may have a look at the exact situation:
Look at the yellow tunnel (Google Maps)
Google has made the Street View really helpful in this case. I think that the screenshot above contains a biker located pretty much at the exact position where I experienced the collision. ;-) My bike was leaving the underpass at a relaxing speed, not much above 10 miles per hour.

Suddenly, a dog jumped at me from the right side (and perhaps from the "top"). Along with its owners (or business partners), it was previously playing with a tennis-ball-sized colorful ball that just bounced off a nearby trash can, I was told, which is why the dog's world line became so chaotic. The mammal could have landed on my handlebars for a little while. It's hard to remember every split second in the moment of such a shock but I believe that I hit my brakes within 0.1 seconds.

At any rate, I was flying over my handlebars and landed on the sidewalk. It had to look rather scary. An hour later, it looks like two mild abrasions on the left knee and one more abrasion near the right foot are the only visible negative consequences. Nothing else but my breath was knocked off for a while, much like the bike chain. The owners of the dog were kind enough to offer me some help and return the chain to its prescribed place. I verified that the left knee was just painful but not broken in any measurable way and so on. Even the cell phone seems to work. When my moped collapsed on ice just 150 meters from this place 5 years ago, my digital camera got damaged and its LCD display stopped working in a few days.

A horny cruel monster and a relative of my collision partner

The bastard's weight was 33 kilograms, I was told. (The dog was an alpha male; the correct weight of adult males should be 30-32 kg.) This brown villain apparently wasn't injured at all, despite its hitting an object that is 2-3 times heavier than the dog and fortified with some metallic components. Because kids' speed is much lower, much like their resiliency, I find it plausible that a kid that would jump on a bike in similar states of motion (but with the kid-like speed) could be fine, too.

They seem to be godless killing machines. ;-) Your humble correspondent has just checked that the boxers may achieve the maximum speed up to 35 miles per hour, 2-3 times faster than my bike at that moment. So the total momentum was actually close to zero – the center-of-mass frame may have coincided with the laboratory i.e. sidewalk frame.

I don't know how many boxers – canine or human ones – may be reading this physics blog. But those who are reading this sentence right now are encouraged to slow down whenever you are approaching a corner, e.g. the corner of an underpass. A corner is an L-shaped boundary of matter. You are too dangerous!


Three hours ago, the idea of a traffic accident involving a dog looked bizarre to me. But I turned on TV now and the first thing they showed the viewers was this today's video of an event that took place 3 days ago:

Dogs are apparently organizing Global Days of Traffic Accidents these days. Ms Andie Valerio is said to have saved the life of the dog on the L.A. highway. But my experience today suggests that instead, she has saved the lives of dozens of the drivers while she has preserved the godless killing machine.


  1. Glad to hear you got away without major injuries. Last year I had a huge dog jumping at me at full speed (both of us), I basically flew into the forest, where I luckily landed softly, though with plenty of scratches and bruises. Funny in that the dog seemed to be excited but not aggressive, maybe they're just misestimating their impact factor ;)

  2. Lubos - Glad to read that you're OK. .1 seconds seems damn quick.

  3. Good to share this experience! I would have preferred a forest over the asphalt, too! ;-)

    These animals must be immune towards similar collisions which are probably mundane events for them. I would guess that fast animals must in general be able to withstand collisions at speeds k*v where v is their maximum speed and k is a rather universal coefficient. The faster animals one considers, the more innocent a fixed-speed collision is for them.

    I still don't plan to be scared of dogs on the sidewalk, like some... unnamed relatives with lots of muscles who are terrified even by the smallest breeds. ;-)

  4. What are all those colored flecks on the ground in the picture? Do your devotees run ahead of you when you're biking and spread flower petals in your path?

  5. Thanks a lot, RAF.

    Sometimes 8 years ago or so, we were biking with my friend VB in the forests in the forests near the Western Bohemian spas. His brakes didn't work well - he wanted to save a few bucks on the brakes.

    So he was biking about 60 km/h down the hill, the centrifugal force forced him to go on the left part of the road, and suddenly a Toyota Corolla in the opposite direction.

    The Toyota driver stopped almost immediately. But VB couldn't because the brakes were almost dysfunctional, so he jumped to the Corolla's front window, destroyed it, made the 3-year-old girl scream as if she met some scary heroes from fairy-tales, and he had to pay $1,000 to the Toyota Corolla's owner for the shattered window. ;-)

    VB spent an afternoon in the hospital, having broken one of the bones in the face... how it's called in English. Lícní kost.

  6. LOL, RAF, funny. You're not the first one who asked this question. Who do you think was before you? ;-)

    For some questions and answers on that, see e.g.

    I am still uncertain whether the high voltage plays any role.

  7. Inertia - gods little joke on gravitation.

  8. GrandfatherclockAug 25, 2014, 7:27:00 PM

    If you are a real scientist, you should give the boxer a chance to tell his side of the story !!!111!

  9. Of course that I have invited the boxer to write a guest blog. But I did so because I am respectful towards murderous animals, not because it would be a scientific attitude.

    Trying to always remain ambiguous with having two equally likely sides is exactly what science is *not*. Science is a process of discrimination - learning which side of the story is right and which side of the story is wrong. And frankly speaking, science doesn't really treat animals as colleagues. Dogs are objects much like trucks, diamonds, or quasars. They can be studied but they are not really able to scientifically study Nature by themselves.

  10. Dogs are not objects and the animal’s owner is just as responsible for any damages caused by it as the truck driver is responsible for damages due to the truck.
    Don’t you have leash laws in Czechia? Dogs here must be on leash except in closed and controlled areas. These leash laws are frequently ignored but the owner’s responsibility is not.

    Our Katie, a golden retriever, is the best friend I will ever have.
    You should consider getting a dog, Lubos. He or she will love you unconditionally. People who never have a dog are missing one of life’s more worthwhile experiences.

  11. Poor dog, over here the SPCA would charge you with cruelty to animals, ha ha Boxers are playful breed and unfortunately for loving owners are known not to have a very long life span.

  12. I'm glad to hear you're still in one piece, Luboš. :)

    Dogs are great fun. They're very easy to wind up. The younger ones anyway.

    It's uncanny the way they often seem to sense what you're going to do before you're fully conscious of it yourself. Such as when you're about to kick them.

  13. You guessed that the Pope was going to retire ! :D

    (No date guessed, but the retreat of Pope's something very unusual historically)

  14. My parents used to have a boxer.
    Like someone already said, boxers belong to the most playful and friendly dog races despite their dangerous "look".
    Actually my mother tried to train her (it was a she) to be able to attack under human control.
    It was not really a success because a boxer tends to consider even a threatening big human male with a knife as a potential friend first and it takes much persuasion to make him change his mind.
    There was also a study showing that boxers belonged to races most tolerant to small children - people often ignore that but a small child (under 3) is a real nuisance for a dog because they tend to squeeze its ears, put their fingers in its eyes and more generally unintentionally hurt it.
    A cat reacts on "cuddling" by small children by seeking an advantage of altitude while a dog may react by biting (this is what millions years of evolution dictate him anyway).
    That is why there are proportionally more accidents with children than with adults.
    I always wondered why our boxer patiently supported a child that creatively tried to extend, crush and rotate various parts of her body.
    So Lubos be very sure that the boxer you met didn't mean any harm to you and if it considered you as an equivalently relevant part of the landscape as the ball, it would have avoided the collision.
    However I am afraid that its brain would always put the ball's importance several orders of magnitude above yours
    I find interesting you k.v theory. I never thought about it but it is true that a dog doesn't hesitate to impact something probably knowing that this something will take the frontal impact with much more difficulty.
    The cats are exactly opposite because they are excellent at avoiding impacts.
    Did you notice how a cat when it is hunting a ball uses a very different strategy ? Instead of the frontal impact, it hides where it considers to be "behind" the ball and makes a lightning speed rush on the ball only after the ball stopped moving.

  15. Glad you are okay from this, Lubos. Not to sound like a mother hen, but I hope you wear a helmet with your bike?

  16. Thanks for your care! I own a bike helmet but don't use it 99% of the time. I didn't have it yesterday, and it wouldn't have helped me. I should have had some bands around knees, however. ;-)

  17. Just remember that what is inside your cranium is rare and of extreme value. So take good care of it!

  18. I’m with Ann, Lubos, your neurons will be happier inside a helmet.

  19. You should always use your helmet while biking, always. Why wouldn't you?

  20. Thanks to all of you for your care. But don't you think that I got another piece of evidence that it's a useless superstition yesterday?

  21. No, you were just lucky :-) I have been unlucky, but luckily I did wear my helmet (so no harm done).

  22. Superstition? Well, I could prattle on about my many bike crashes and how lucky I was, but this dude missed a great career in pro sports while on a skip and jump to the tennis courts.

  23. thejollygreenmanAug 26, 2014, 5:35:00 PM

    If ever you want a dog, do get a boxer. They are the most wonderful animals to have around. No other dog breed needs the company of humans as much as they do. They are wonderful around children, but, given your love for outdoor sport, what a lovely animal to go with you when you go cycling, jogging, walking. To this day I still mourn my beloved boxer Casandra. They are not as trainable and clever like for instance German Shepherds or Border Collies, but they do so much enjoy life!

  24. Fert137, you should finish your peanuts and banana in your cage and refrain from communicating with anyone.

  25. At what is this? Are you sick and today is your the nervous breakdown?

    I waste no more words with you, retarded.

  26. The word “object” has several, context-dependent, meanings but the way you are using it is insulting to our furry friends. Dogs exhibit a wide range of emotions and remarkably intelligent behavior. I think you should apologize. :-)

  27. Did the boxer’s owner act responsibly? Throwing a ball for a dog to fetch in the direction of small children, elderly folks, bicyclists or vehicular traffic is not responsible behavior.
    It seems that the number of dogs in my neighborhood exceeds the number of dwellings and any serious attempt to enforce leash laws would be met with open rebellion. Fortunately, the vast majority of dog owners are considerate of others act responsibly.

  28. Apologies, I surely didn't want to indicate that they have no heart or emotions or playfulness.

    These interpretations of the languages are puzzling to me. When we say that a woman is a sexual object, does it mean that women have no emotions? That would be pretty bold. ;-)

  29. I wrote exactly where he fetched it, didn't I? He didn't throw it in the direction of the people. He tossed it to an empty place of a park where the ball got reflected from a garbage bin and went, along with the dog, behind the corner inside the underpass.

  30. I've collided badly. read my fb msg