Astronomy Buff

Happy Earth Day, Theta

by Tony on April 22nd, 2008

Dear Theta:

You are but a capital, cursive O. Theta, you are but a zero with a curvy line. An egg with a skull cap. You are but a simply decorated easter egg. How simple you are–yet, so useful. You, you, simple symbol, simple ambassador of mathematics, physics, meteorology…. Just look at you.

You are on the Earth Day Flag.

They call you the “dead theta,” the official flag symbol of earth day.

When did you die, I wonder? Did you receive a proper burial?

According to Wikipedia:

According to Flags of the World, the Ecology Flag was created by cartoonist Ron Cobb, and was published for the first time in October 25, 1969. The flag was patterned after the flag of the United States, and had thirteen stripes alternating green and white. Its canton was green with a yellow theta. It originally had a symbol that was a combination of the letters “E” and “O” taken from the words “Environment” and “Organism”, respectively. Later flags used either a theta because of its historic use as a warning symbol, or the peace symbol. Theta would later become associated with Earth Day.

Theta, you are even a warning symbol. You are like the pirate skull and cross bones for peace and conservation! Theta, you are one cool, mean mother.

In classical Athens, the Greeks used you as a warning sign and a symbol for death.

You are, according to wikipedia, an “aspirated dental plosive.” Somehow I like the sound of that.

The Greeks assigned you the value of 9. You may have been partially derived from Egyptian hyroglyphs depicting the sun.

Here are some other things you’ve been used for:

• A plane angle in geometry.
• The voiceless dental fricative in the International Phonetic Alphabet, such as in the words thick or thin (but not as in the, which is the voiced dental fricative).
• The Potential temperature in meteorology.
• The score of a test taker in item response theory.
• Theta Type Replication: a type of bacterial DNA replication specific to circular chromosomes
• Threshold value of an artificial neuron.

Your upper-case letter (Θ) is used as a symbol for:

• Dimensionless temperature in transport phenomena.
• Big O notation. Denoting an asymptotically tight bound in analysis of algorithms.
• Θ (set theory), a certain ordinal number.
• Representing pentaquarks, exotic baryons in particle physics.
• Earth Day.
• Brain Signal Frequency (Beta, Alpha, Theta, Delta) ranging from 4–8 Hz

Thank you, Theta. And, happy Earth Day.

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POSTED IN: general astronomy