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Orange as the color of hot

Heymatt:

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I noticed that the cherry on my cigarette, the coals in my BBQ, and the element in my fish-tank heater all glow the same shade of orange. I believe this isn’t a coincidence. Could you please explain why this is so?

— Chris, via email

It’s no coincidence, it’s incandescence! The same principle that makes lightbulbs shine is at work in the smoldering cherry of a cigarette. It’s an effect of black body radiation, which involves no small amount of physics, but I am pretty sure I can explain it easily. When materials are heated uniformly, they emit radiation at predictable wavelengths based on how hot they are. A portion of that radiation is visible light, which is why the coals in the fire glow, but most of it is infrared radiation and heat, which is why they’ll barbecue your burgers and brats so well. The dull, orange color of cigarette cherries and coals is at the very bottom of the spectrum — just above the infrared — that corresponds to temperatures around 700–1200C. As temperatures rise, the corresponding colors brighten all the way to a brilliant blue that’s nearly ultraviolet. You’ll never see that shade in a coal, however, since that would be twice the temperature of the sun’s surface and possibly kill you if it was in your barbecue pit.

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Heymatt:

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I noticed that the cherry on my cigarette, the coals in my BBQ, and the element in my fish-tank heater all glow the same shade of orange. I believe this isn’t a coincidence. Could you please explain why this is so?

— Chris, via email

It’s no coincidence, it’s incandescence! The same principle that makes lightbulbs shine is at work in the smoldering cherry of a cigarette. It’s an effect of black body radiation, which involves no small amount of physics, but I am pretty sure I can explain it easily. When materials are heated uniformly, they emit radiation at predictable wavelengths based on how hot they are. A portion of that radiation is visible light, which is why the coals in the fire glow, but most of it is infrared radiation and heat, which is why they’ll barbecue your burgers and brats so well. The dull, orange color of cigarette cherries and coals is at the very bottom of the spectrum — just above the infrared — that corresponds to temperatures around 700–1200C. As temperatures rise, the corresponding colors brighten all the way to a brilliant blue that’s nearly ultraviolet. You’ll never see that shade in a coal, however, since that would be twice the temperature of the sun’s surface and possibly kill you if it was in your barbecue pit.

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4S Ranch Allied Gardens Alpine Baja Balboa Park Bankers Hill Barrio Logan Bay Ho Bay Park Black Mountain Ranch Blossom Valley Bonita Bonsall Borrego Springs Boulevard Campo Cardiff-by-the-Sea Carlsbad Carmel Mountain Carmel Valley Chollas View Chula Vista City College City Heights Clairemont College Area Coronado CSU San Marcos Cuyamaca College Del Cerro Del Mar Descanso Downtown San Diego Eastlake East Village El Cajon Emerald Hills Encanto Encinitas Escondido Fallbrook Fletcher Hills Golden Hill Grant Hill Grantville Grossmont College Guatay Harbor Island Hillcrest Imperial Beach Imperial Valley Jacumba Jamacha-Lomita Jamul Julian Kearny Mesa Kensington La Jolla Lakeside La Mesa Lemon Grove Leucadia Liberty Station Lincoln Acres Lincoln Park Linda Vista Little Italy Logan Heights Mesa College Midway District MiraCosta College Miramar Miramar College Mira Mesa Mission Beach Mission Hills Mission Valley Mountain View Mount Hope Mount Laguna National City Nestor Normal Heights North Park Oak Park Ocean Beach Oceanside Old Town Otay Mesa Pacific Beach Pala Palomar College Palomar Mountain Paradise Hills Pauma Valley Pine Valley Point Loma Point Loma Nazarene Potrero Poway Rainbow Ramona Rancho Bernardo Rancho Penasquitos Rancho San Diego Rancho Santa Fe Rolando San Carlos San Marcos San Onofre Santa Ysabel Santee San Ysidro Scripps Ranch SDSU Serra Mesa Shelltown Shelter Island Sherman Heights Skyline Solana Beach Sorrento Valley Southcrest South Park Southwestern College Spring Valley Stockton Talmadge Temecula Tierrasanta Tijuana UCSD University City University Heights USD Valencia Park Valley Center Vista Warner Springs
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