Yep, same guy.

Before Cuckoo's Egg, I was better known as a planetary scientist. My PhD dissertation relied on polarization data taken by Pioneer 10 & 11 to understand the scattering characteristics of Jupiter's upper atmosphere.

Cheers,
-Cliff

Pioneer 10 and 11, of course (not 11 and 12)

The Pioneer 10 & 11 spacecraft both flew by Jupiter, and Pioneer 11 went on to Saturn encounter.

I remember it well - while a grad student at the Lunar & Plantetary Labs, I helped with the Imaging Photopolarimeter during Saturn Encounter.

The spacecraft, designed in the early 1970's, had essentially no onboard memory, so instructions had to be uploaded in real time. The several hour-long communications delay made for real excitement at encounter (Did the spacecraft survive the ring crossing? Did the instruction arrive? Did the sensor point in the correct direction? Is it returning images?)

We'd spent months in advance, preparing alternative sequences for the encounter. Each sequence was on punched papertape. Then, at encounter in September 1979, we'd pick the tape, mount it on a teletype, and send the data out over the NASA deep space network, then anxiously wait to see if the instructions worked on Pioneer 11.

A prime number can represent information which is forbidden to possess.
See http://en.wikipedia.org/wiki/Illegal_prime

This goes back about a decade to the AACS encryption key controversy.

Want your kids to learn physics? Throw away the computer simulations. Build things with them. Run experiments. Observe and think about the results.

    To teach physics, start with things like C-clamps, string, rubber bands, wire, springs, low-friction carts, compasses, magnets, thermometers, balloons, weights, scales, and pulleys.

    More advanced stuff: a voltmeter/ammeter (analog stuff), an old oscilloscope, an air table (a kids' hockey table), vacuum pump & bell jar, countdown timer/photogate, etc. Many of these things show up on craigslist for cheap (I picked up two free oscilloscopes and have given them to my sharp high school students).

    Computer simulations? Naw. Have your kids do real physics:

    A pendulum made of a bowling ball and rope. Time the pendulum swings and then ask: which will change the period - changing the lenghth of the swings, changing the weight, or changing the length of the rope?

    Fool around with a signal generator, an oscilloscope, and a microphone. What's a sound wave look like? How is frequency related to period?

    Play with thermometers, ice, water, and fire. What's the temperature of ice and water? Can you get water colder than this? How hot is water from the kettle? Can you get water hotter than this?

    Get a voltmeter, wire, and some magnets. Can you really induce a voltage by moving a magnet nearby?

    Don't sidetrack your kids with simulations & computer graphics. Real physics starts by fooling around with reality.

    Obs Feynman quote: "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."

In the early 1980's, a group of Santa Cruz physics grad students built a set of computers into their cowboy boots. These timed the spinning of roulette wheels and applied Newtonian physics.

Thomas Bass wrote this up in the 1985 book, The Eudaemonic Pie, and caused the Nevada Gaming Commission to ban the use of these devices.

See http://en.wikipedia.org/wiki/The_Eudaemonic_Pie

When a satellite fails, often it cannot be de-orbited. Several failure modes will cause this - the most common is the malfunction of the controller, communications unit, or onboard power system. When any of these fail, there's no way to command the retro-rocket to fire.

Then, too, you need the satellite to be pointed in the correct direction (meaning that its stationkeeping rockets are working), and for it to have enough hydrazine (or whatever) to be deorbited. Near the end of a spacecraft's life, consumables are limited.

And, of course, it takes a lot of energy to de-orbit many satellites. A geostationary comsat needs one heck of a kick motor to get it down. Usually they are not brought down to burnup in the atmosphere. Instead, they are moved a few dozen (hundred?) kilometers inwards from their geostationary slot. This puts 'em well away from the main circle of geostationary satellites.

It's like consumer goods ... manufacturers work to make them last long enough to complete their mission; few think about how to get rid of 'em once their purpose has expired.