See stars and the Sun in your kitchen.

Cooking temperature. Wavelengths. Electromagnetic spectrum. And what the colors of space tell us.


electromagnetic spectrum in the kitchen and in the skies

1-Minute NomNom

Look at the stars and the Sun. Do you see a kitchen? No, I am not joking. Let me tell you why.

First look into a toaster when it is cold. What is the color of the heating element? Or look at the heating coils of an electric stove? What is the color? Chances are they are all black.

Four electric elements on a stove with one turned on

Color differences between a cold and hot electric coil

Once you switch them on and heat them up, they turn fiery reddish-yellow-orange. They look like the colors of fire, but if they run on electricity, there is no fire to begin with.

It has to do with the relationship between color, temperature and wavelength. When the heating elements or coils are first heated, the electrons in them vibrate at a certain frequency, emitting infra-red radiation of a certain wavelength. These wavelengths, however, are not in the visible range of the electromagnetic spectrum. So we cannot see them.

electromagnetic spectrum

As the heating element heats up, the electrons vibrate more vigorously. Their frequencies go up, which also means the wavelengths start to get shorter (frequency and wavelengths are inversely related — as one goes up, the other goes down). Eventually the wavelengths are as short as those of red visible light in the electromagnetic spectrum. That is when we see the red of the heating coils. According to the Modernist Cuisine, that is how we got the term “red hot”.

Heat them to higher temperatures, and the vibration frequencies increase further. The wavelengths become even shorter, and the color we see moves into the orange, and then the yellow ranges. At even higher temperatures, they can even turn blue, and then “invisible” as it moves its way across the electromagnetic spectrum into ultra-violet radiation (which cannot be seen with the naked eye).

properties of color and temperature in the electromagnetic spectrum can help determine the temperature of the stars and sun

These amazing properties found in the kitchen are also how astronomers determined the temperature of the stars and the Sun. The NASA Hubble website explains that:

Stars hotter than the Sun (over 6,000 degrees C) put out most of their light in the blue and ultraviolet regions of the spectrum. Stars cooler than the Sun (below 5,000 degrees C) put out most of their light in the red and infrared regions of the spectrum. Solid objects heated to 1,000 degrees C appear red but are putting out far more (invisible) infrared light than red light.

I bet you will never look an electric heating coil or element in the same way again. Or maybe when you now look at the stars and the Sun, you will see an entire astronomical kitchen! Which is strangely beautiful, methinks.

electric coils and electromagnetic spectrum


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