Huh? Every morning I go out to work whilst my cat lies flat-out on the sofa/kitchen-table/garden-wall/expensive-and-fragile-plants, with his eyes closed and a big grin on his face. There's no doubt about who's the slave.

What they mean is that they have tested the symmetry of the electron and found it to be equivalent in all directions, like a sphere. The hair's-width thing is just an analogy to describe the degree to which that symmetry has been tested; the electron does not have an intrinsic size or shape. If there were any detectable asymmetry, that would imply that the electron and positron are not perfect opposites, and may explain why there is so little antimatter in the universe.

I'm afraid this is pretty much true, although the hobbyist in me doesn't like to admit it.

The amount of radioactivity you're looking for is small compared to natural background, and small even compared to the normal variations in background. To identify any un-natural contamination you'll need a detector capable of distinguishing different isotopes, in a low-background environment, and it'll need to be regularly calibrated with standard sources. That entails a lot more gear than a Geiger-Muller tube, all of which is very very expensive, not to say tricky to operate.

With a GM counter about the best you can do is to try to measure the radioactive decay of a sample, although most relevant isotopes have very long lifetimes which will be too hard to measure. 131-iodine is easy to detect and has a measurable half-life at 8 days, but I expect the authorities would find it before you do, and anyway most of it has gone by now.

Alternatively you might befriend a physicist at your nearest nuclear research institute. Even then he or she will need to be quite a good friend, because the time and effort involved is significant, and this kind of expensive gear tends to be permanently in-use.

Beta detectors can be both very small and very sensitive, but I agree they are generally less useful than gamma detectors. There is a use in health-physics for detectors which can distinguish gamma and neutron radiation. But they exist already, and have done for years and years.

My old school had a sign-in system based on face-recognition. Nobody ever found a way to circumvent it. This was 25 years ago, but I believe others were using a similar system even earlier.

If there was a type of radar for detecting and quantifying incompetence, distraction and tiredness, the world would be a better place.

"I'm sorry sir, you're over the state incompetence limit. You'll have to come with me."

And road congestion would be a thing of the past.

Coming soon: how to mill new floorboards out of titanium, after the old floor was shattered by a falling calculator.

Evolution has played out countless thousands of battles to the death, and only the very best survivors are left. So we will inevitably continue the tooth-and-nail fight to survive and pass on our genes, because that is how nature has made us.

I think the very concept of "stealing" time is arse-backwards. I don't care or count how many hours my team puts in. I judge them by what they do: how many tasks or projects they complete, and how much help they needed. If anybody seems easily able to deal with their workload, I give them more challenging tasks. And if they complete those too, I use that to justify a raise at the end of the year (theirs, not mine).

If an above-average guy only does an average amount of work and spends half his time web-surfing, that's no reason to fire him. But he'll only get an average review.

That's my system, and I think it's fair.

There is a simple joy in building something without coworkers to perform design reviews. :)

Arrrgh! SPICE is work. There is a simple joy in building something physical, that works and which you can show to people.

It looks like these books are hard to find new, but can be found second-hand online.

Many of the suggestions above are good for somebody who already has a grounding in basic electronics. Horowitz and Hill is a great text book, but it lacks the practicalities a beginner needs to translate a circuit diagram into a flashing light on the table. Tom Duncan provides the walk-through you asked for, as well as the explanations.

For the absolute beginner (which is about the level of GCSE physics), I recommend the books I started with. Look for Tom Duncan's "Adventures with Electronics". As well as circuit diagrams there are clear illustrations so that you can start building working circuits right away. The workings of each project is clearly explained, and followed by suggestions for expanding or altering the circuit to do something different. It's very rewarding: you don't need to understand the circuit before you start, but you certainly will after experimenting with it.

After the first book, there's "Adventures with Micro Electronics" and "Adventures with Digital Electronics" which introduce ICs and binary logic. Once you've got through these three books, you'll be sufficiently well grounded to pick up standard electronics texts to progress further.

Each book comes with a list of components which you can easily order from Maplin or RadioSpares. It's cheaper than buying a ready made kit, and the components are better quality than many of the kits (which will save you many frustrated hours). Any anyway you'll soon be buying more components to make larger circuits and your own ideas.

"That's an interesting rock, let's look a bit more closely... woah, no time for that, we're off again."
"It sure is windy today. I feel a little seasick."
"Was that a pair of eyes we just went past?"
[sometime later after a change in the weather]
"The forecast is calm for the next month. Has anybody got any great ideas for studying this patch of sand we're stuck on?"

The very fact that Spirit has worked so tremendously well up to now means that it is still an extremely valuable device. It's worth spending every effort to save the rover now, precisely because it has shown itself able to surpass its original goals by so much. In other words, age has increased rather than decreased its worth.