one-way mirror?

February 2, 2007 at 3:50 pm | | crazy figure contest, stupid technology, wild web

The Japanese National Institute of Advanced Industrial Science and Technology (AIST) has developed a reversible mirror (source), which consists of two pieces of glass with a small spacing in between containing a thin film of magnesium-titanium alloy. Allegedly, the film turns transparent when hydrogen is pumped into the spacing; reflective when air/oxygen pumped in. The idea is to use the glass as windows for building and reduce cooling costs (by turning the windows reflective on sunny days). Interesting idea. (But….)


This story was picked up by several blogs/websites (PhysOrg, SciFiTech, Geekologie, UberGizmo), but I was disappointed that no one pointed out an obvious flaw in the above figure: in the “transparent” frame, they’ve added substantial backlighting. Of course the mirror is more transparent when you supply backlighting! The direction of illumination is different between the two frames and thus they aren’t comparable. This is way worse than changing the bin size.

OK, I’m sure the mirror effect is reversible in this system, and that the effect is dramatic. Just too bad that they had to fake the figure!

And BTW, do we really want hydrogen and oxygen pumped thoughout high-rise buildings, contained in fragile glass? It’ll give “raging inferno” a new name!


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  1. Good observation, I’m ashamed I didn’t catch that. I strive to be more observant!

    Comment by Chemistry Show — February 2, 2007 #

  2. What am I missing here? Why don’t they just use those windows/mirrors you see in interrogation rooms?

    Comment by jordan — February 2, 2007 #

  3. because then you couldn’t shut it off in the winter, when you want to save on heating…

    Comment by sam — February 2, 2007 #

  4. Genius!

    Comment by jordan — February 3, 2007 #

  5. 1% H2 is below the LFL.

    Comment by kendall — February 3, 2007 #

  6. what is LFL? this?

    Comment by sam — February 3, 2007 #

  7. Lower flammability limit. Although by encouraging lust free living in males, you’re 28% less likely to be smote in a freak buildling window fire.

    Comment by kendall — February 3, 2007 #

  8. It would be better to do this with polarised film and an LCD layer. Even better with curtains.

    Comment by John — June 13, 2014 #

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