A Fragment of Muonionalusta

meteorite 5

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?
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BAMF2014: A Cocktail Glass for Zero Gravity

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Part of our continuing coverage of highlights from the 2014 Bay Area Maker Faire.

The Zero Gravity Cocktail Project from the Cosmic Lifestyle Corporation aims to make a cocktail glass suitable for drinking fluids in zero-G:

The Zero Gravity Cocktail Project is an attempt to bridge the gap between the space tourism vision and mainstream reality. By creating a fun object that appeals to many people, we hope to show that space tourism is not an abstract concept but a stepping stone for improving the way people live, work, and play beyond planet Earth.

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Fluids don’t behave the same in outer space, so a glass would have to have quite a different design, relying on capillary action not gravity to move them from point A to B. Channels guide the fluid from stem to rim.

These are 3D printed prototypes of white plastic. Future versions might be 3D printed from clear biocompatible plastic, or made of glass or stainless steel.

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The glass has bulbous bottom with a hollow stem, for balance and fluid delivery.  A rubber one-way valve can be inserted into the bottom to allow the glass to be refilled as you drink. They have also made an earthbound variant of this glass that has a more traditional base, allowing it to be set down, when gravity permits.

We’re secretly hoping that the next version includes a way to suspend your olive in the middle of the conical section, no toothpick required.

From the Mailbag: Understanding the Homopolar Motor

Wes wrote in to say:

I am an Electrical Engineer (graduated May ’72, Texas Tech U), but I never saw or even heard of a homopolar motor until last week, when I saw an electric motor made from four parts on National Geographic’s program, “None of the Above“. When I first saw it, I figured it must be a hoax. A DC motor had to have a commutator and two magnets.

Only when I was browsing around in Wikipedia did I find an article on the motor. I happened to have everything I needed, so I built one, not really expecting it to work. To my great surprise, it spun up to a few thousand RPMs in seconds. I read Wikipedia’s theory of operation, but it didn’t make sense. Today, I came across your wonderfully clear and simple explanation, and now I understand the motor perfectly.

I simply cannot thank you enough for your drawing and explanation.

Thanks for writing in— we’re glad to hear you enjoyed learning something new! The instructions for making the motor and the discussion of how it works are in our articles:

Open Source Beehives

The Open Source Beehives project is currently running a crowdfunding campaign with the goal of gathering information from sensor equipped hives throughout the world to help solve bee population problems like colony collapse syndrome. The sensors can also be used by individual beekeepers to monitor the health of their hive.

Even without the sensors and the citizen science, their hive designs are beautiful.

Citizen Science: How Big is a Bird Egg?

emu egg in ostrich eggbot

While talking about egg sizes in the context of the Eggbot project, we realized that while we have access to a few samples, we do not have a good understanding of the normal variation in the sizes of various bird eggs.

The sizes of chicken eggs are well understood and well regulated, but for other types of bird eggs (like the emu egg above) the sizes are not necessarily so standard. If you have access to other types of eggs or eggshells, we’d like your help in gathering data about the size and variation in these other types of eggs.

We’ve set up a survey form to collect egg size data and we plan to post about our results once we have collected enough data.

Thank you!