On Sun, 21 Dec 2003 22:17:31 GMT, Ian Stirling
wrote:

Christopher wrote:
On Mon, 15 Dec 2003 19:26:48 GMT, Ian Stirling
wrote:

Christopher wrote:
In several experiments conducted by NASA and by the Russians plants
were grown indoors using an artificial light. What type of light was
used that produces light on the same wave lengths as the suns does?

Standard lights used for lighting homes/offices/stadia work just fine.
The basic problem is that they emit relatively little light.

Sunlight is around a kilowatt a square meter (in most latitudes).
One 12W compact fluorescent light generates as much light as a window
around 5-6cm square.
I'm currently growing some water plants under 2*12W CF lights, probably
producing around 2000 lumens.
Over maybe .1 square meter, for around a sixth of sunlights intensity.

However, plants generally don't exploit all sunlight.
From my (sparse) knowledge of biology, photosynthesis tops out at some
fraction of the brightest sunlight.

Right, thanks for that, I only asked as there is a longish thread in
sci.space.policy regarding this type of space activity.


A very, very handy lighting FAQ I found is:

Radiometry and photometry in astronomy
http://home.tiscali.se/pausch/comp/radfaq.html

This has basic numbers for everything from the brightness of the whole sky
when the sun is 20 degrees below the horizon, to what a lumen is.

Thanks, I've book marked it.



Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill