Al Stahler: Light is strong medicine
The opera singer with the deep bass voice is showing off, singing a low note, then a lower note still, just to show … how low … he can go. He reaches his lowest possible note … and then … silence.
Light works the same way: Start with the highest visible frequencies – start with violet … go a bit lower … to blue … then down thru green … yellow … orange.
With orange, we’re in territory we can see in the kitchen. The wires in the toaster glow orange. But once the toast pops – the power is cut – the wires lose energy, and orange drops to red; the wires lose more energy, and the red disappears. But turn your hand toward the wires, and you can feel “low notes” below red – your skin feels infrared – heat energy.
And then the infrared fades. With the right equipment, though, we could see the wires putting out even lower frequency radiation – radio waves.
If the wires could cool down to absolute zero – the coldest temperature possible, minus 460 degrees Fahrenheit – even the radio would disappear, and we’d have light’s equivalent of silence: total darkness.
When we climb stairs, we fight gravity. Shine a flashlight straight up, and light also fights gravity. Gravity sucks energy out of light – shifts the color of light downward – shifts violet down toward blue, blue down toward green.
Don’t try this at home. Not that it’s dangerous – just that you’ll never notice the downshift in color, in the weak gravity we feel on earth.
Like a babe in bathwater, we swim in a sea of stars. Every star we see with the naked eye is a member of our Milky Way Galaxy. Look toward the south, these nights, to find Orion, the hunter. Looking toward the Hunter, we’re looking toward the edge of the Milky Way – were looking outward.
The stars shine by day, as well, but they’re blotted out by sunlight. If we could see the stars in daylight, we’d see the sun surrounded by the stars of the Goat, Sagittarius. Sagittarius is special – looking toward Sadge, we’re looking inward – toward the center of our galaxy.
Smack dab in the center of our galaxy – the very center – sits a black hole – a black hole whose gravity is strong enough to pull light all the way down the spectrum – blue to red to infrared to radio … and then down to nothing … down to darkness. Our galaxy’s black hole – sitting, this time of year, behind the sun – is truly … utterly … black.
Light a candle, and poke the tip of a butter knife into the flame. The knife-tip is quickly covered with black soot.
Get anything hot enough, and it will glow. The candle flame reaches two thousand degrees Fahrenheit – hot enough to make soot glow in every color of the rainbow. Candlelight emerges from glowing soot.
Screens – computer screens, phone screens – make color differently, more precisely. Screens (just like the LEDs that glow red to tell us our devices are powered-up) put out only certain colors. Part of the candle flame does the same. The base of the candle flame glows – more-or-less precisely – blue.
That blue is not coming from soot. The wax molecules in the candle are composed of dozens of atoms, glued together. The heat of the flame first melts the wax – separates one molecule from another – then breaks up the individual molecules into tiny clumps of atoms, just a few atoms in each. These clumps will soon combine with oxygen – will soon burn – to create the flame. But, before they can touch oxygen, they lose some of the energy they’ve absorbed from the flame by emitting light – blue light.
The candle flame is shaped by gravity – hot gases rising up from the candle. In space, with no gravity to shape the flame, candle flames are round.
We slept, last Sunday night, through the longest night of the year … Monday, we cruised through the year’s shortest day … Earth crossed the winter solstice, just after 2 o’clock, Monday morning.
Light is strong medicine … which can make this time of year a challenge. Take care of yourself, take care of those around you. Stay human, and have a happy holiday.
Al Stahler enjoys sharing science and nature with friends and neighbors in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and can be reached at firstname.lastname@example.org.
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