Discuss: Naked Science Q&A and the Edinburgh Science Festival

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Offline thedoc

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Can cold water cause weight loss, is my mother-in-law turning into a reptile and why doesn't a mobile phone interfere with itself are all answered in this week's Naked Science Question and Answer Extravaganza. We also find out about a new way to keep track of your favourite online bands and musicians, and hear how the whole world harmonises - turning news into music in just three hours! Plus, in Kitchen Science, Dave pulverises an egg to explain the basis of air pressure, and for Question of the Week Diana finds out whether alcohol can rehydrate a lost traveller in the desert.
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Offline turnipsock

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I wish I had known about this, I would have come along. I could have had a good discussion about string theory and how it affects Edinburghs one way system.
Beeswax: Natures petrol tank sealant.

When things are in 3D, is it always the same three dimensions?



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Hi Naked Team

Regarding Dave's answer on bouncing light between mirrors:

Trapping light between highly reflecting mirrors is in fact extremely useful.  It's one of the tricks used to produce extremely stable optical atomic clocks.  If you put near perfect mirrors (eg with power losses of less than parts in 10 thousand or more) at the end of a near perfectly rigid spacer you can make an extremely frequency-stable laser.  There is a means of making the the length of a rigid body with mirrors on each dictate the frequency of laser light.  John Hall, a recent Physics Nobel Prize winner, was largely responsible for creating and  implementing this technique.  

Once the laser frequency is stabilized to what is commonly referred to as an optical cavity, the light can then be used to probe (scan across) very narrow atomic transitions (in the visible part of the spectrum).  

Some transitions are ideal for accurate frequency standards, i.e. clocks.  Possibly some day in the future the second (the SI second) will be defined in terms of a number of cycles/waves of optical light, which will be a number approximately 100 thousand times greater than the present 9 192 631 770 cycles governed by a transition in the caesium atom (all in the aid of improving accuracy).  

Look at what GPS does for us now with microwave clocks; goodness knows what the future holds for us with optical clocks.

Wiki touches on it here:  http://en.wikipedia.org/wiki/Optical_cavity
Here's another: http://www.rp-photonics.com/reference_cavities.html


Postdoctoral Research Associate
Frequency Standards and Metrology, Optical Division
School of Physics, Fairway Entrance #2
University of Western Australia, Nedlands, Perth, WA  6009