Half a croissant, on a plate, with a sign in front of it saying '50c'
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Eggtimer

The Gravity Defying Sands of Time
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The 'sands' in the egg timer are made of tiny iron filings. Each end of the timer contains a small electro-magnet. These are switched on/off via some kind of tilt switch thing, so whichever magnet is at the top is switched on. The result - an egg timer that appears to flow upwards.

The only problem I foresee is 'clumping' around the thin middle section.

UberDonkey, Jul 21 2008

(?) Upside-down hourglass swag http://www.justadve...tTchotchkes_10.shtm
Using buoyancy, not magnetism. [jutta, Jul 21 2008]

(?) Upside-down hourglass (with fish) http://www.officepl.../sandtimerfish.html
[jutta, Jul 22 2008]

[link]






       This is a cool idea, but I don't think it will work. Magnetism isn't like gravity. It's going to "travel" along the iron filings and bind them together all through the timer.
MisterQED, Jul 21 2008
  

       What you want is a relatively constant magnetic field throughout the cylinder - like gravity is. Best done in either of two ways. a) strong magnet, but placed at some distance, say at roof level. The magnetic field will drop off following inverse square rules, but if the length of the timer is much shorter than the distance to the magnet, field strength will be essentially constant. Other method would be to use a coil around the timer to produce the magnetic field. GOing to have to come up with something transperent, however. Any transparent conductors handy?   

       Lastly, why not use metallic particles coated in something that won't conduct the field, such as an enamel, or plastic. If done on a fine enough scale, this could work still.   

       I really like the idea. [+]
Custardguts, Jul 21 2008
  

       (plastic-coated magnets will still stick togerther)
hippo, Jul 21 2008
  

       I think the magnet could be used as a collector of all iron particles that had already moved to the top half, but the movement from bottom to top is controlled by one of those ultrasonic smoke generators that sit under a small pool of water.
Ling, Jul 21 2008
  

       What about using a sucky thing instead of a magnet?
phundug, Jul 21 2008
  

       I like the concept.   

       The simplest implementation I can think of would be to fill it with liquid and use buoyant particles. It would lose some of the effect since the particles wouldn't "fall up" as fast as the sand in a normal timer falls down.   

       A solution more like your original would be to use a magnetic field on the bottom and diamagnetic particles. Those shouldn’t have the clumping problems, but you would need an even larger magnetic field than you would with a magnetic material to make it work well.   

       If you combine the two concepts and use neutrally buoyant diamagnetic particles (perhaps tiny hollow bismuth sphere’s), you don’t need as strong of a magnet. You don't gain much over a buoyant solution except that gravity is completely removed from the equation so you can make it work in any orientation or in zero gravity.
scad mientist, Jul 21 2008
  

       An implementation that uses boyancy exists; I've seen at least one company use it as party favors. Let me go find a link.
jutta, Jul 21 2008
  
      
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