A Fraction Of A Millisecond

Many of us followed the real-time drama of five rich people trapped underwater, some of us with more excitement than the fate of fifty Polish coal-mines earning their daily bread underground.

Over the five-day drama my mind rocked back-and-forth trying to second-guess the experts, a difficult task when so little data was available.

Then ...

This BBC News article appeared

“ When a submarine hull collapses, it moves inward at about 1,500 mph (2,414km/h) - ... The time required for complete collapse is about one millisecond, or one thousandth of a second. A human brain responds instinctually to a stimulus at about 25 milliseconds, Mr. Corley says. Human rational response - from sensing to acting - is believed to be at best 150 milliseconds.

I fired up my trusty old spreadsheet processor and produced these calculations:

So I came up with 1.8 milliseconds, which is the same order of magnitude as “about one millisecond”, so I was content with the report.

The next day my physics teacher Mr. Puzey came to attention in my mind. The formulas for motion. Velocity is Time multiplied by Acceleration. In essence, it takes a certain amount of time for material to reach 1,500 mph from zero mph.

How much time? Assuming linear acceleration, it’s a straight-line graph, with zero at one end and 1,500 at the other end.

I think that means that I must double the time interval, arriving at 3.6 milliseconds.

Although a consent rate of acceleration is a shaky assumption. Perhaps the rate of acceleration increases as parts of the material break apart. It takes me a long tome to bend an iron bar, especially to make the first part of a bend, but once the metal is weakened I can compete the transformation to U-shaped rather easily.

That said I am inclined to agree with the cliché “They never knew what hit them”. Even for a brain as fast as mine, 150 milliseconds isn’t a lot of time to worry about my future.

Search