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Light and father Christmas

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Here are some seasonal factoids and a couple of lightbulb jokes to round off the year with a smile - or a groan and eye-rolling like my very expressive god-daughter). 

We all know that vision gets worse with age - it turns out that colour vision does too. But this paper explains that sensitivity to medium-long 

wavelengths (red-green) is more affected than the blue-yellow axis - so perhaps he should be wearing blue, not red and green!  (*)

His little helpers are working shifts right now, which  will be playing havoc with their biological clock. Perhaps one day they will be chosen based on their chronotype rather than their ability to wrap awkward shapes  - this paper explains why.  

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Rudoph’s nose does actually 'glow' red thanks to a bioluminescent layer of cells with a red phosphorescent overlay (*)  That  red nose is particularly useful in foggy conditions because long wavelength red light is scattered least by fog - something called Rayleigh Scattering - here's the formula...

Rudolph’s eyes are also useful - a reflective layer of cells just behind the pupil changes colour to adjust to the extreme differences in light levels between summer and winter in the arctic. In winter, they are deep blue which reflects back less light than their summer golden yellow tone - (*)

Rudolph’s visual system can also ‘see’ with UV light - incredibly useful in snowy landscape that can reflect up to 90% of the UV - and when the sun is low on the horizon, light is scattered such that the majority of light that reaches objects is blue or UV (*) and (*). 

 

And 20 jokes for a lighting geek's Christmas crackers - 

1.  How many psychiatrists does it take to change a lightbulb? 

Only one, but the bulb has got to really want to change.

2.  How many actors does it take to change a lightbulb?
Only one. They don’t like to share the spotlight.

3.  How many board meetings does it take to get a lightbulb changed?
This topic was resumed from last week’s discussion but is incomplete pending resolution of some action items. It will be continued next week. Meanwhile…

4.  How many programmers does it take to screw in a lightbulb?
None. That’s a hardware problem.

5.  How many hipsters does it take to change a lightbulb?
It’s a very obscure number, you probably won’t have heard of it.

6.  What do you get when you cross a thought with a lightbulb?
A bright idea!

7.  How many managers does it take to change a lightbulb?
One to get the bulb and two to get the phone number to dial one of their subordinates to actually change it.

8.  How many fatalists does it take to screw in a light bulb?
What does it matter? We’re all gonna die anyway.

9. How many lawyers does it take to change a lightbulb?
How many can you afford?

10. How many graduate students does it take to change a lightbulb?
Only one, but it takes nine years.

11. How many Mac users does it take to change a lightbulb?
You have to replace the whole motherboard.

12. How many magicians does it take to change a lightbulb?
Depends on what you want to change it into.

13. How many nihilists does it take to change a lightbulb?
There is nothing to change.

14. How many jugglers does it take to change a lightbulb?
One, but it takes at least three lightbulbs.

15. How many politicians does it take to change a lightbulb?
One to change it, and another one to change it back again.

16. How many boring people does it take to change a lightbulb?
One.

17. How many economists does it take to change a lightbulb?
If the lightbulb needed changing, the market would have already done it.

18. How many sociologists does it take to change a lightbulb?
The lightbulb is fine — the system has to change.

19. How many lawyers does it take to change a lightbulb?
One to do it and two to sue him for malpractice.

20. How did the hipster burn his hand? 

He changed the lightbulb before it was cool.