A Cold-light Sphere is a 5cm transparent sphere which glows with a soft light.
The sphere is filled with a collection of bacteria in a balanced sealed ecosystem, one of which produces a bioluminescence cold-light. The sphere needs to be exposed to daylight to re-charge it. The sphere glows for 4 to 8 hours after an 8 to 12 hour exposure to sunlight.
The sphere may be stored in a dark space, the bacteria going dormant, for up to a year and still have the light production be normal. Exposure to extremes of heat or cold will also kill the bacteria and render the globe useless. The sphere is otherwise sealed and does not require external power nor is it sensitive to external pressures (vacuum to 100 atmospheres).