Yesterday I wrote about a rare earth material called gadolinium that loses its attraction to magnets when it reaches room temperature. And I wondered if you could use this strange phenomenon as the basis for a generator. I thought it was obvious that a device depending on outside heat was not a perpetual motion machine any more than a wind mill is, but but many of you left comments to clarify that point. Apparently my writing was sloppy because the earlier paragraphs were about perpetual motion and I didn't call out the transition to non-perpetual motion and the gadolinium generator. In the interest of clarity, the rest of this post is NOT about perpetual motion in the strictest sense.

Someone pointed out that gadolinium doesn't lose its attraction to magnets; it just becomes less of a magnet itself, but would still be attracted to magnets like metal. There appears to be some conflicting information on the Internet on that point. The stuff I read indicates that a warmed piece of gadolinium wouldn't be attracted to a magnet in any fashion. Your unreliable strangers might be more reliable than my unreliable strangers.

But here's the interesting part. When you expose gadolinium to a magnet, it heats up. That property has been used to create refrigeration, although I don't see any recent articles about it. http://www.eurekalert.org/features/doe/2001-11/dl-mrs062802.php

So if what I read on the Internet is correct (which seems hugely unlikely) you could build a (nearly) perpetual motion device using a natural magnet and gadolinium as long as you could control the room temperature without any extra energy. Here's how it would work: Imagine a natural magnet suspended over a piece of gadolinium in a room that is just below room temperature. The gadolinium is attracted to the magnet and jumps from its resting point to attach to the magnet. Now the gadolinium is experiencing a stonger magnetic force, and according to its natural and unique properties, it heats up. That extra heat puts it above room temperature and it becomes suddenly unattracted to the magnet, falls off, and begins to cool. And repeat, forever, or until someone opens a window.

I suppose you'd use more energy keeping the room at the right temperature than you'd create by the process. But still, if it worked outdoors for half an hour every day, as the world went from cool to warm, in certain climates on certain days, it would still be nifty.

Clearly this won't work, or you'd have a toy like this on your desk as a novelty item that only operates when the room temperature is in a particular range. So I assume I am misinterpreting the qualities of gadolinium. But that doesn't make it any less fun to think about.
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+1 Rank Up Rank Down
May 22, 2008
Very very cool. I guess the reason why it hasn't been done large-scale is because gadolinium is quite rare.
0 Rank Up Rank Down
May 22, 2008
i wonder why you went down to 38 comments a day from approx 150?
+3 Rank Up Rank Down
May 22, 2008
Seems overly complex for something that is effectively like a Stirling engine. http://en.wikipedia.org/wiki/Stirling_engine
May 22, 2008
Well, I'm normally pretty quick to poo-poo on your eciting new technologies, but the whole magnetocaloric effect is exciting beyond words. I've talked to a couple of my coworkers about it, today, and they were blown away, too. I've dug up a few other articles on the subject, and the more I read it, the better it gets. This is awesome materials science, and for whatever reason, I had no exposure to it at all! Thanks for sharing it with us!

On an unrelated topic. I have decided that I like the new site -- I like the color comics, I like the animations, I like the mashups, I like blog integration. But...

I've been timing the page load times. I am not exaggerating when I say this: Every day, I have two or three page-loads that take 1 minute and 30 seconds or worse. The animation page always takes a long time to load the first time (today, it was 2 minutes, 5 seconds), while subsequent loads are much more reasonable -- in the 10 - 30 second range. The homepage always takes forever to load the first time (today it was 1 minute, 55 seconds), and the blog always takes forever to load the first time (I was talking to someone and forgot to note my start time, but it was over a minute). Mashups are similarly slow, but since I can't read the text at the "thumbnail" resolution and I have a painful wait between every single click I make, I just quit reading them. About one in 5 is pretty good (although the obvious joke is always repeated a dozen times), and it's taking up to a minute per page-load... If you do the math, that's like 8 !$%*!$ mashups and 2 decent ones in 10 minutes.... Seriously, who reads those?!

Lest my internet connection be blamed... I can literally type in the Dilbert url and wait... and then pull up youtube, and then watch a video, and then flip back to the web browser that's struggling to bring up Dilbert and continue waiting... before I get to see a 3-panel comic strip.

Logging in is quick, but the "remember me" checkbox doesn't seem to do anything.
May 22, 2008
The properties of gadolinium remind me of my old girlfriend. She was nice and attracted to me when things were going well; dinner dates, going to the movies, giving flowers, walking in the park and buying her nice gifts. But when any of these niceties dropped off to any degree on my part she became less attractive to me. So keeping her at “room temperature” was somewhat costly and took effort. Is true love like perpetual motion?

+3 Rank Up Rank Down
May 22, 2008
Blimey - according to Wikipedia, this stuff gets used in quite a few applications, including nuclear reactor control (I love the idea of a CANDU reactor, very positive spin), MRI scanning, PET scanning, neutrol X-ray scanning (seems to be a scanner material) and compounds of it it used to get called "Earth" in older literature.

It's also about $130 a kilo but apparently the price is very stable. So if you manage to use this stuff to make desk doohickeys you now have some kind of raw material price point.

You'll be robbing the medical community of its' capability to make contrast media for scans though... naughty naughty!
-3 Rank Up Rank Down
May 22, 2008
Magnetism is an energy. I suspect your magnet will lose a bit of magnetism with repeated and long-term use - I think that is where the energy is coming from to refute a 'perpetual motion' description. Also, your 'room temperature' room is going to be absorbing or giving off energy through the walls, ceiling, and floor. Unless perfectly insulated, your gadolinium spring may not be able to keep up.

I would think the energy available would be similar to current nuclear energy sources - quite effective in industrial applications.

But maybe there is hope here for a battery-powered snowmobile using a gadolinium-magnet-steam generator.
May 22, 2008
malicient: normally room temperature is considered to be around 67F for quick calculations.
May 22, 2008
The first thing I do when I read about something that sounds made up, like gandolinium, is I look for reliable information... it is attracted to magnents until it reaches room temperature? What is room temperature? Is that a scientific term, because I've always understood room temperature to mean the temperature of the room... some rooms are colder than others.
+4 Rank Up Rank Down
May 22, 2008
How about this? A conveyor bet that is half inside a dank musty cave and half out in the sunshine. A few pounds of gadolinium are placed every three feet on the belt and magnets are placed at the appropriate end. The moving conveyor belt drives a series of cranks and shafts which eventually spin one of those little plastic windmill flowers. Due to the butterfly effect, the breeze that is created by the flower leads to a strom on the other side of the Pacific. There, lightning rods are used to capture enough gigwatts to power all the 1985 Deloreans still on the road thus solving any future plutonium shortages as well.
May 22, 2008
we don't have to worry about solving global warming because the LHC is going to turn the entire planet into a strange star, remember?

I just hope the Europeans follow proper protocol and remember to yell "HEY, Y'ALL - WATCH THIS!!!" before powering the thing up... :D
+2 Rank Up Rank Down
May 22, 2008
Hi Scott,

No matter how many caveats you put in your post, people will still point out all the flaws with whatever you are not actually talking about. Gadolinium does sound like fun. I'll bet you could come up with some type of executive desk toy based on gadolinium's magnetic traits. It may not be a perpetual motion machine, but you could probably make some money selling it in Sky Mall. It will be at least as useful as the PHB's who buy it.

May 22, 2008
The floor in my basement is tile. I live in Wisconsin so at least 9 months out of the year anything in contact with this floor becomes chilly even if the rest of the house is at a reasonable temperature. The 'at rest' state of the gadolinium could be in contact with the floor where it would quickly cool to sub-room temperature and regain its attractiveness. I don't think a cold floor would have helped Slap D Monkey's situation though.
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