Sunday, April 16, 2006

How to boil an Easter egg

Life can be confusing, but only a physicist can make the simple complex. The smart people at Newton offer the mathematic formula for boiling an egg.

A Formula for Soft-Boiling Eggs
The Derivation
"To obtain a simple formula the problem must be idealised somewhat, so the egg will be treated as a spherical homogeneous object of mass M and initial temperature Tegg. If the egg is placed straight into a pan of boiling water at Twater, it will be ready when the temperature at the boundary of the yolk has risen to Tyolk~63°C. With these assumptions, the cooking time t can be deduced by solving a heat diffusion equation.

The Result
"The full derivation (PDF, 19kB), which can be viewed with the free Adobe Acrobat Reader, is quite complicated but the final result is relatively simple:

tcooked = [M2/3 cp1/3 /Kpiesq(4pie/3) 2/3] loge[0.76x (T egg - T water) / (T yolk - T water)]

where ρ is density, c the specific heat capacity, and K thermal conductivity of 'egg'. According to this formula, a medium egg (M~57 g) straight from the fridge (Tegg=4°C) takes four and a half minutes to cook, but the same egg would take three and a half minutes if it had been stored at room temperature (Tegg=21°C). If all the eggs are stored in the fridge, then a small (size 6, 47 g) egg will require four minutes to cook, and a large egg (size 2, 67 g) will take five minutes."

What can I add to that, except to wish you and your family a Blessed and Happy Easter. As with Christmas, Jesus is the reason for the season!

No comments: