One of the interesting aircraft on display.
Some of the many electric cars.
Space-rated carpet treads on a mini-lunar rover to help it get traction in loose dust.
You can check out the full set of pictures on flickr.
This little chunk of crystalline metal is a tiny slice of a meteorite — a rock that fell from the sky. When one says that, the next natural question is, “how do you know it’s a meteorite?” (We will get to that.) But what is really staggering is not just that we know, but how much we know about it and its history. And what a long history it is.
This specimen is a 68 gram sample cut from a fragment of the Muonionalusta meteorite. According to our best current understanding, the parent body that Muonionalusta came from was one of the earliest bodies to take shape during the formation of our solar system. It began as a protoplanet (or planetisimal) that accreted within the protoplanetary disk that would eventually become our solar system. It accreted over the course of roughly the first million years after the beginning or our solar system. (That is to say, during the first million years after the very first solids condensed from the protoplanetary disk.) The parent body had an iron-nickel “planetary” core, 50–110 km in radius, that was eventually exposed by collisions that stripped away most of its insulating mantle. It cooled very slowly over the next 1-2 million years. It is estimated (with startling precision) by Pb-Pb dating that the body crossed below a temperature of ~300 °C at 4565.3 ± 0.1 million years ago, just 2-3 million years after the solar system began to form. For the next four billion years, it led a largely unremarkable existence as an asteroid (minor planet) until it broke apart (possibly due to a major collision) about 400 million years ago. Then, one fine day roughly one million years ago, a large fragment entered the earth’s atmosphere, breaking into hundreds (perhaps, thousands) of smaller fragments that rained down in a shower of fire upon what is now northern Sweden and Finland. Four ice ages transported the surviving meteorite fragments across the Swedish tundra, until their first discovery (and naming after the nearby Muonio river) in 1906.
But, how do we know all of that?
It’s the hunger for learning rather than raw intellect that distinguishes Extreme Learners from the gifted. Intensely motivated and harboring a breadth of interests, they also consider ignorance a temporary and reparable condition.
Eric wrote in to say:
It was fun. It was fun to build the Larson Scanner. It was fun because I successfully put it together and it worked as designed. It was so fun I’ll do this again!
In the mid 70′s I attempted to construct a Radio Shack short wave radio kit with a soldering gun. That’s right, I used a soldering gun. Believe it or not, it worked … as a battery heater upper.
Thank you for the helpful instructions and well designed kit. It’s nice to know that 40 years after my last kit, I can drop the battery killer nickname.
Last fall, we built an oversized Digi-Comp II for MIT, which we’ll be posting about in the near future. Today, MIT computer science professor Scott Aaronson published a short “paperlet” about the computational capabilities of the Digi-Comp II on his blog, Shtetl-Optimized:
…it’s amazing that such a simple contraption of balls and toggles could already take us over the threshold of universality. Universality would immediately explain why the Digi-Comp is capable of multiplication, division, sorting, and so on. If, on the other hand, we don’t have universality, that too is extremely interesting—for we’d then face the challenge of explaining how the Digi-Comp can do so many things without being universal.
Jenslabs has published a thoughtful and thorough evaluation of a number of currently available rollerball and gel pens. He tested them using his Circlon machine.
One thing that anyone who as ever built a drawing machine realizes, is that to get quality results you need a quality pen. There are millions of pens out there, but after a little trial and error I realized that rollerball pens or pens with gel ink are the best pen types for my machine. Both rollerball and gel ink pens use a water based ink that is less viscous then the oil based ink used in ballpoint pens. The Circlon machine sometimes move very fast, so the pen has to be able to release enough ink to make solid lines even at high speed.