Priscilla Oppenheimer wrote:
>
> At 01:03 AM 10/8/00, Jeff Kell wrote:
> >Priscilla Oppenheimer wrote:
> >
> > > Does this help at all? Speed of light in twisted-pair cable is 177,000
> > > km/sec. So a bit occupies 177,000 divided by 10 million bits per second, or
> > > 17.7 meters, in 10 Mbps Ethernet.
> > >
> > > 177,000 divided by 100 million bits per second is 1.77 meters for 100 Mbps
> > > Ethernet. (I'm sure you figured that one out already.)
> >
> >Some people questioned "the math" above, I'm guessing because it seems
> >to read that a bit travels 17.7 meters/sec in 10 Mb Ethernet. But
> >we missed the "physics" issues to keep things equivalent.
>
> No fuzzy math or physics is needed. We are dividing meters per second by
> bits per second, which is the same thing as meters/sec x sec/bit. Cancel
> out the seconds and you have meters per bit, in other words how much space
> on a cable a bit occupies.
>
You bring back some fond memories -- I was privileged to hear retired
Rear Admiral Grace Hopper speak on two occasions, during her later years
when DEC was so savvy as to hire her as a consultant. One of her talents
was the ability to make computing and communications seem real to others.
During her days as a DEC spokesperson, she was known to hand out physical
"bits". In the first talk I attended, she handed each of us short pieces
of wire which she explained were "nanoseconds". In the next talk, she
gave us plastic-wrapped packets of what appeared to be salt and pepper
-- picoseconds, she exclaimed.
Somewhere in my physical archives I still have both of these, and do
treasure them, to the puzzlement of others...
http://www.cs.yale.edu/homes/tap/Files/hopper-story.html
> I was just sitting out on my deck on the last sunny day we will probably
> have for months in Oregon and realized that folks may be missing the basic
> arithmetic involved, though they understand the more complicated aspects.
> That's weird!
>
Ahh, in a few months, we'll all be jealous of the great snow conditions.
Then we can calculate the length of a bit on the cable of a chair lift! :-)
Marty Adkins Email: [EMAIL PROTECTED]
Mentor Technologies Phone: 410-280-8840 x3006
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