Though both hot and cold light derive from excited electrons for this question we're focusing on cold light. Energy in molecules cause electrons to get excited, moving up a level in their atomic orbit. When the electrons settles down, they release a photon, or a light particle.
Bioluminescence is defined as the process by which organisms convert energy into light (hence, why they glow as a result). Although, bioluminescence produces “cold light” because the process generates about 20% thermal radiation into light, clearly the bug in this situation isn’t a very effective bioluminescent bug as most of its energy is being emitted as heat. Even so, it can be surmised that the bug doesn’t experience combustion because it’s not releasing enough heat to reach the temperature required for the chemical reaction to occur. Combustion is an exothermic reaction, meaning it releases heat, and is the process by which something burns. To give you an example of just how high the required temperature for a combustion reaction must be, the minimum temperature required to ignite a gas or vapor in air without even sparking a flame starts at 175 degrees Celsius and ranges all the way up to 463 degrees Celsius. Actually flammable substances are much higher than that. In essence, it would be very hard for the bug to reach such high temperatures through bioluminescence since it is a process whose entire purpose is to convert all the energy into “cold light.” Combustion is also dependent of on ratio of air to fuel. Since our atmosphere is primarily comprised of Nitrogen this would also inhibit combustion.
Bibliography:
"HowStuffWorks "How Bioluminescence Works"" HowStuffWorks "Science" Web. 22 Oct. 2011. http://science.howstuffworks.com/environmental/life/zoology/all-about-animals/bioluminescence.htm.
"Gases - Explosive and Flammability Concentration Limits." Engineering ToolBox. Web. 22 Oct. 2011. http://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html.
"HowStuffWorks "How Bioluminescence Works"" HowStuffWorks "Science" Web. 22 Oct. 2011. http://science.howstuffworks.com/environmental/life/zoology/all-about-animals/bioluminescence.htm.
"Gases - Explosive and Flammability Concentration Limits." Engineering ToolBox. Web. 22 Oct. 2011. http://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html.
3 comments:
Emma, your response to the question is very well written and informative but i would disagree you with when you said "Although, bioluminescence produces “cold light” because the process generates about 20% thermal radiation into light, clearly the bug in this situation isn’t a very effective bioluminescent bug as most of its energy is being emitted as heat." The reason that the bug can burn you is because it releases toxins and poisons that can cause skin inflammation immediately upon contact, making the appearance of a burn. It is simply a defense mechanism for the bug.
I like that you mentioned that even flammable substances had to reach a much higher temperature then the bug was at to actually combust. We emit enough heat to actually be able to feel a change in our skin temperatures, but that doesn't mean we're all going to explode.
I think that this blog post was very
well written and the light and fun, yet informative tone of the post made it very fun to read. Concerning your information, I mostly agree with what you said. I enjoyed your theoretical and practical examples of the temperature it takes to "burn", though substances such as sodium metal burns when the temperature is above its freezing point; it burns even in water.
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