Scientific Explanation for Dog's "Sixth Sense"

Over the years, I have read and heard many stories of dogs seemingly supernatural ability to sense when their master is coming home, or when the mail truck is on its way, etc. I believe there is some tendency among humans to treat this as a magical "sixth sense". Or to over-credit the sense of hearing: "dogs can differentiate the sound of their owner's car/school bus from 5 miles away"--I'm definitely calling bs on that one.

But as so often is the case, there is a known or posited scientific explanation. This article focuses on the time-decay of smell, in combination with other cues, as the explanation. E.g., the family children, in this case, arrive home from school on a school bus. The departure and arrival times of school buses are pretty predictable, I bet +- 5 minutes 95% of the time. The rate at which the children's scent decays is the main clue. This signals to the dog that arrival is imminent, prompting it to lurk in anticipation near the door.

The final part of the magic trick is delivered by the acute--but not magically powerful--sense of hearing. The dog lurks near the door, and they do hear the vehicle far sooner than any human would. They react in anticipation, completing the illusion that they have a magical superpower.

Encountering scientific explanations is ultimately much more rewarding than crediting far-fetched or magical explanations of phenomena.

What Causes Friction?

As an engineering undergrad, I've always wondered, in the back of my mind--what actually causes friction? Curiously, unless my memory is utterly failing me, this topic was not covered, even cursorily, in any of my classes. Friction is introduced as a given, like gravity. Anyway, for some reason--which may have to do with greater free time, as my brood enters Young Adulthood--I finally bothered to research the topic.

It is surprisingly esoteric and unsettled.

What seems like the most obvious idea--microscopic surface irregularities--seems to have been largely discarded (except that surface irregularities seem to be cited as contributing to the adhesion theory). Some of the different theories I came across:

• Molecular adhesions (van der Waals' forces). But then why is it not proportional to area?
• Collisions and entanglements--seems like an atomic level version of roughness.
• "Gunk in the middle"
• Sound waves
• Then there is grand tour, which I frankly don't have the energy, nor, quite likely, the knowledge and brainpower, to digest.

Someday, maybe in the long winter of American Siberia, I will muster the energy and ambition for a Part 2 on this.

Static Electricity and Gas Pumps

I used to think the posted prohibition on re-entering your vehicle while fueling it was intended to make sure the customer keeps an eye on the pump, just in the very unlikely case it should jam somehow, and not auto-shutoff. But I have since learned the real peril is static electricity, (although the article touches on the auto-shutoff issue as well).

"You should never re-enter a vehicle when you're fueling," Mr. Wormser said.

That's because a person who re-enters a vehicle and slides across the seat can acquire a static charge of thousands of volts, caused by friction between two electrically dissimilar materials, such as clothing and seat upholstery, said Dr. Robert E. Nabours, an electrical engineer. If the charge is not harmlessly discharged through the person's shoes or by the person touching metal, such as part of a grounded car, an electrical arc can jump from a hand to the nozzle, igniting gas vapors and starting a fire.