The best energy display in a science museum in North America

[NNadir]

has to be the one on the third floor of the Liberty Science Museum in New Jersey.

It has models of every single kind of energy system you can imagine, including in many cases working models. In fact their working windmill outside generates about 10 kilowatts.

It is a fabulous display. My person favorite, the real Geiger Counter by the nuclear reactor mock up with real Uranium ore, real Radium, and real pottery with Uranium orange glaze.

There was one type of system with which I had zero familiarity, a thermal gradient system that is usable in tropical climates only.

The museum is just off exit 14b on the Turnpike and from many places in it, you can get spectacular views of Manhattan.

A lot of science museums have given way to flash and computer screens, but this museum retains real hands on science.

If you're near there, go there.

The food is lousy though, so eat before you go.

[BlueEyedSon]

1. thx, will check it out!

[Chico Man]

2. I do like the Van de Graaff Generator at the MOS, Boston

And of course the Tesla Coils too

[Squeech]

4. Just the other night

the MOS hosted a musical performance, a piece called ZAP, scored for about a dozen live musicians plus "robots" (mechanical noisemakers) and carefully-timed sparks from the various coils and generators.

As music I didn't think it was terribly good-- very minimalist, like early Terry Riley before he got his tape echo systems working, not very rigorous or substantial. Pleasant enough.

As theatre, however, it was big fun. The musicians wore Sun Ra-like space outfits (a friend of mine playing Lyricon had on a blazer made of tinfoil, and a metal coil with a spherical ornament on his head). On the other hand, the young woman running the generators wore an evening gown. There were video screens on the sides, showing images of the players distorted by various electronic means. And of course there were the sparks spurting around. (And the ambient light level was kept low enough that, in order to be seen, the conductor had to use a light stick for a baton.)

[Massacure]

3. Sounds cool.

Too bad I live 1000 miles away.

[Township75]

5. The one in Oak Ridge, TN isn't that great.

I can't even recall if it is soley dedicated to energy though. I went there in 2003, and it was OK, but nothing that great.

[Kolesar]

6. Does the pot glow in the dark?

I don't know when I will again be in Jersey. Sounds like my kind of stuff. Have you ever seen the steam exhibit at the Smithsonian? They have a low pressure steam piston from a 19th century electric generating plant. The cylinder is huge and the crankarm goes up to the next floor of the museum.

[NNadir]

7. The things that don't glow in the dark are hot, that which does isn't.

Of course the whole matter of "glowing in the dark," is one of the memes of radioactivity that helps to mystify - as in increase ignorance about - the whole subject.

Even so, I suppose that the meme has sunk in even with me - and I am someone who has made a great effort to understand radioactivity. I was thus surprised to see that, at least as detected by the Liberty Science Museum's Geiger counter, the most radioactive object in the display was not the Radium painted clock face - which does glow - but was in fact the Fiestaware glazed bowl which doesn't glow. The bowl in fact, appeared to be much hotter than even the Uranite ore or the Americium containing smoke detector. For the record, a picture of a bowl very, very much like the one in the Liberty Science Museum is shown here:

http://www.theodoregray.com/PeriodicTableDisplay/Elements/092/index.s9.html.

The color is in fact, identical.

I have a lot of experience with Geiger Counters, since I used to use one regularly to monitor my own thyroid (and radioactive clothing) when I was involved in using radioiodine (I-125) to label proteins and other bioactive molecules, something at which I worked for over three years. (Everyone should have a chance to play with a Geiger Counter as I did; it's enlightening.) I don't think there's just one factor accounting for the hot bowl and the not-so-hot clock, but here's what I suspect is going on in this interesting experiment, which is available to anyone in the New York/New Jersey area who visits the museum.

1) First off, one cannot pull the detector (the ionization chamber) equally close to all of the samples. The clock, for instance is at a larger distance than the bowl. This allows the air to attenuate some of the activity. In all cases, the primary radiation source are (primarily) alpha emitters, and alpha radiation is not very penetrating. People often claim that it can be stopped by a sheet of paper, and to some extent, this is true. Air is quite an effective attenuator of alpha radiation, even over relatively short distances.

2) Secondly, while both the clock and the bowl are old objects dating from the middle of the twentieth century, the chemical matrices in which they exist are quite different. The bowl is a glaze, and the Uranium has been fused in (melted into) silicates, much like the proposed radioactive waste forms that have been proposed for Yucca Mountain. Therefore the bowl is highly stabilized and there is little opportunity for leaching of any kind. The clock on the other hand contains radium in a think layer of paint. I very much doubt that the manufacturer of the clock had did any kind of long term stability work. Moreover, the radioactivity to which the paint has been exposed for over one half a century has damaged the paint's molecular structure. Thus it is possible that some of the radium has fallen off the clock face and out of the clock, or at least behind metal parts that provide some shielding. This would tend to reduce the apparent radioactivity of the clock.

3) The glaze is probably at radioactive equilibrium with its daughter nuclei and the clock is probably not. One doubts that very elaborate chemical separations of any type were done to make the uranium glaze. Probably the concentration of the Uranium for the purpose of making glaze was largely a mechanical process, grinding, flotation, etc. Thus many of the elements of the ordinary Uranium decay chain remained in the glaze. These elements included not only Radium, but also other highly radioactive species like Thorium-230 and Lead-210.

The radium however was highly purified. Literally tons of pitchblende (Uranium ore) were processed to obtain gram quantities of Radium. This required some very, very elaborate and precise chemistry, chemistry for which Madame Curie was awarded the Nobel Prize. Most of the other elements in the decay series were thus removed from the radium in this process. The longest lived element in the radium-226 decay chain is the same lead-210 that is in the uranium-238 decay chain. (Radium itself is a member of the U-238 decay chain, accounting for its existence on earth.)

The time required for two members of a decay chain to come into radioactive equilibrium, at which the amount of the daughter nucleus decaying will be exactly matched by the amount of the parent nuclide decaying into it, is given by the relation t = (ln(k1/k2))/(k1-k2), where the the k's are the decay constants, ln(2)/(half-life). Using the half-lives of radium-226, 1590 years, and lead-210, 22.3 years, we see that this time is about 140 years for the radium-226/lead-210 pair. If the clock were made in 1950, it still has not reached radioactive equilibrium, at which time its radioactivity would be the highest.

Actually the clock will probably never reach this equilibrium. One member of the decay series is radon-222 which is a gas. Since the radium is contained in a thin strip of paint, this gas probably has plenty of opportunity to diffuse out of the clock and end up elsewhere in the room or even elsewhere on the planet. Probably the greatest (albeit very small) risk to the purchasers and users of such clocks was connected with this fact; the inert radon gas leaked out of the clocks. In unvented rooms, one managed to get the radioactivity directly in one's flesh through the lungs. Thus the equilbrium lead-210 (a daughter of radon-222) often ended up somewhere else, preventing the equilibrium condition in the clock itself.

It happens that most of the deaths on the planet associated with radioactivity are related to naturally occurring radon, especially in areas with well sealed insulated houses situated on soils with high uranium content, like those in New Jersey, where I live.

(I had a radium painted clock in my room as a child and also my first watch had a radium painted face. I loved both of them but at some point my parents threw them away. I wish I still had them to show MY kids. They were extremely cool.)

4) The uranium in the glaze is not what people now call "depleted." It contains the other isotope, U-235. This isotope is not only more radioactive than "depleted uranium" (U-238), but many of the daughters in the decay chain are very highly radioactive elements like actinium-227 and francium-223. These are very unstable and decay rapidly, causing high daughter activity. Moreover, these nuclei are not merely alpha emitters but they are also potent gamma emitters. Unlike alpha radiation which is not very penetrating, gamma radiation goes right through just about everything, including the air and the Geiger counter detector. This allows the Geiger counter to disproportionately pick-up this radiation.

5) The americium-241 in the smoke detector is probably shielded, at least mildly so. Everybody would cry if it weren't at least in a little tiny lead shield to make them feel better about having something radioactive in their homes..

6) The bowl is bigger than either the clock or the smoke detector. There's just more stuff, more atoms, and therefore more decays.

Anyway, it's a very interesting display. If you're in the neighborhood, check it out. It's fun and it's a little bit surprising, even if you basically understand what's going on.